Author name code: weigelt
ADS astronomy entries on 2022-09-14
author:"Weigelt, Gerd"
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Title: The dust sublimation region of the Type 1 AGN NGC4151 at
a hundred micro-arcsecond scale as resolved by the CHARA Array
interferometer
Authors: Kishimoto, Makoto; Anderson, Matt; ten Brummelaar, Theo;
Farrington, Christopher; Antonucci, Robert; Hoenig, Sebastian; Millour,
Florentin; Tristram, Konrad; Weigelt, Gerd; Sturmann, Laszlo; Sturmann,
Judit; Schaefer, Gail; Scott, Nic
Bibcode: 2022arXiv220906061K
Altcode:
The nuclear region of Type 1 AGNs has only been partially resolved
so far in the near-infrared (IR) where we expect to see the dust
sublimation region and the nucleus directly without obscuration. Here
we present the near-IR interferometric observation of the brightest
Type 1 AGN NGC4151 at long baselines of ~250 m using the CHARA Array,
reaching structures at hundred micro-arcsecond scales. The squared
visibilities decrease down to as low as ~0.25, definitely showing that
the structure is resolved. Furthermore, combining with the previous
visibility measurements at shorter baselines but at different position
angles, we show that the structure is elongated *perpendicular* to
the polar axis of the nucleus, as defined by optical polarization and
a linear radio jet. A thin-ring fit gives a minor/major axis ratio of
~0.7 at a radius ~0.5 mas (~0.03 pc). This is consistent with the case
where the sublimating dust grains are distributed preferentially in an
equatorial plane in a ring-like geometry, viewed at an inclination angle
of ~40 deg. Recent mid-IR interferometric finding of polar-elongated
geometry at a pc scale, together with a larger-scale polar outflow as
spectrally resolved by the HST, would generally suggest a dusty, conical
and hollow outflow being launched presumably in the dust sublimation
region. This might potentially lead to a polar-elongated morphology
in the near-IR, as opposed to the results here. We discuss a possible
scenario where an episodic, one-off anisotropic acceleration formed
a polar-fast and equatorially-slow velocity distribution, having lead
to an effectively flaring geometry as we observe.
Title: Changes in the Na D$_1$ Absorption Components of $\eta$ Carinae
Provide Clues on the Location of the Dissipating Central Occulter
Authors: Pickett, Connor S.; Richardson, Noel D.; Gull, Theodore;
Hillier, D. John; Hartman, Henrik; Ibrahim, Nour; Lane, Alexis M.;
Strawn, Emily; Damineli, Augusto; Moffat, Anthony F. J.; Navarete,
Felipe; Weigelt, Gerd
Bibcode: 2022arXiv220806389P
Altcode:
The Na D absorption doublet in the spectrum of $\eta$ Carinae is
complex, with multiple absorption features associated with the Great
Eruption (1840s), the Lesser Eruption (1890s), and interstellar
clouds. The velocity profile is further complicated by the P Cygni
profile originating in the system's stellar winds and blending
with the He I $\lambda$5876 profile. The Na D profile contains a
multitude of absorption components, including those at velocities of
$-$145 km s$^{-1}$, $-$168 km s$^{-1}$, and $+$87 km s$^{-1}$ that we
concentrate on in this analysis. Ground-based spectra recorded from
2008 to 2021 show significant variability of the $-$145 km s$^{-1}$
absorption throughout long-term observations. In the high ionization
phases of $\eta$ Carinae prior to the 2020 periastron passage, this
feature disappeared completely but briefly reappeared across the 2020
periastron, along with a second absorption at $-$168 km s$^{-1}$. Over
the past few decades, $\eta$ Car has been gradually brightening
demonstrated to be caused by a dissipating occulter. The decreasing
absorption of the $-$145 km s$^{-1}$ component, coupled with similar
trends seen in absorptions of ultraviolet resonant lines, indicate
that this central occulter was possibly a large clump associated with
the Little Homunculus or another clump between the Little Homunculus
and the star. We also report on a foreground absorption component at
$+$87 km s$^{-1}$. Comparison of Na D absorption in the spectra of
nearby systems demonstrates that this red-shifted component likely
originates in an extended foreground structure consistent with a
previous ultraviolet spectral survey in the Carina Nebula.
Title: Locating dust and molecules in the inner circumstellar
environment of R~Sculptoris with MATISSE
Authors: Drevon, Julien; Millour, Florentin; Cruzalèbes, Pierre;
Paladini, Claudia; Hron, Josef; Meilland, A.; Allouche, F.; Hofmann,
K. -H.; Lagarde, S.; Lopez, B.; Matter, A.; Petrov, R.; Robbe-Dubois,
S.; Schertl, D.; Wittkowski, M.; Zins, G.; Ábrahám, P.; Antonelli,
P.; Beckmann, U.; Berio, P.; Bettonvil, F.; Glindemann, A.; Graser,
U.; Heininger, M.; Henning, Thomas; Isbell, Jacob W.; Jaffe,
Walter; Labadie, Lucas; Leinert, Christoph; Lehmitz, Michael;
Morel, Sébastien; Meisenheimer, Klaus; Soulain, Anthony; Varga,
Josef; Weigelt, Gerd; Woillez, Julien; Augereau, Jean-Charles; van
Boekel, Roy; Burtscher, Leonard; Danchi, William; Dominik, Carsten;
Gamez-Rosas, Violetta; Hocdé, Vincent; Hogerheijde, M.; Klarmann,
Lucia; Kokoulina, Elena; Leftley, James; Stee, Ph.; Vakili, Farrokh;
Waters, Rens; Wolf, Sebastian; Yoffe, Gideon
Bibcode: 2022arXiv220810845D
Altcode:
AGB stars are one of the main sources of dust production in the
Galaxy. However, it is not clear what this process looks like and
where the dust is condensing in the circumstellar environment. By
characterizing the location of the dust and the molecules in the close
environment of an AGB star, we aim to achieve a better understanding
the history of the dust formation process. We observed the carbon star
R Scl with the VLTI-MATISSE instrument in L- and N-bands. The high
angular resolution of the VLTI observations, combined with a large
uv-plane coverage allowed us to use image reconstruction methods. To
constrain the dust and molecules' location, we used two different
methods: MIRA image reconstruction and the 1D code RHAPSODY. We found
evidence of C2H2 and HCN molecules between 1 and 3.4 Rstar which is
much closer to the star than the location of the dust (between 3.8
and 17.0 Rstar). We also estimated a mass-loss rate of 1.2+-0.4x10-6
Msun per yr. In the meantime, we confirmed the previously published
characteristics of a thin dust shell, composed of amorphous carbon
(amC) and silicon carbide (SiC). However, no clear SiC feature has
been detected in the MATISSE visibilities. This might be caused by
molecular absorption that can affect the shape of the SiC band at 11.3
micron. The appearance of the molecular shells is in good agreement
with predictions from dynamical atmosphere models. For the first time,
we co-located dust and molecules in the environment of an AGB star. We
confirm that the molecules are located closer to the star than the
dust. The MIRA images unveil the presence of a clumpy environment in the
fuzzy emission region beyond 4.0 Rstar. Furthermore, with the available
dynamic range and angular resolution, we did not detect the presence
of a binary companion. Additional observations combining MATISSE and
SAM-VISIR instrument should enable this detection in future studies.
Title: Eta Carinae: An Evolving View of the Central Binary, Its
Interacting Winds and Its Foreground Ejecta
Authors: Gull, Theodore R.; Hillier, D. John; Hartman, Henrik;
Corcoran, Michael F.; Damineli, Augusto; Espinoza-Galeas, David;
Hamaguchi, Kenji; Navarete, Felipe; Nielsen, Krister; Madura, Thomas;
Moffat, Anthony F. J.; Morris, Patrick; Richardson, Noel D.; Russell,
Christopher M. P.; Stevens, Ian R.; Weigelt, Gerd
Bibcode: 2022ApJ...933..175G
Altcode: 2022arXiv220515116G
FUV spectra of η Car, recorded across two decades with HST/STIS,
document multiple changes in resonant lines caused by dissipating
extinction in our line of sight. The FUV flux has increased nearly
tenfold, which has led to increased ionization of the multiple shells
within the Homunculus and photodestruction of H2. Comparison
of observed resonant line profiles with CMFGEN model profiles allows
separation of wind-wind collision and shell absorptions from the
primary wind P Cygni profiles. The dissipating occulter preferentially
obscured the central binary and interacting winds relative to the
very extended primary wind. We are now able to monitor changes in
the colliding winds with orbital phase. High-velocity transient
absorptions occurred across the most recent periastron passage,
indicating acceleration of the primary wind by the secondary wind,
which leads to a downstream, high-velocity bow shock that is newly
generated every orbital period. There is no evidence of changes in
the properties of the binary winds.
Title: The dusty heart of Circinus. I. Imaging the circumnuclear
dust in N-band
Authors: Isbell, J. W.; Meisenheimer, K.; Pott, J. -U.; Stalevski,
M.; Tristram, K. R. W.; Sanchez-Bermudez, J.; Hofmann, K. -H.; Gámez
Rosas, V.; Jaffe, W.; Burtscher, L.; Leftley, J.; Petrov, R.; Lopez,
B.; Henning, T.; Weigelt, G.; Allouche, F.; Berio, P.; Bettonvil, F.;
Cruzalebes, P.; Dominik, C.; Heininger, M.; Hogerheijde, M.; Lagarde,
S.; Lehmitz, M.; Matter, A.; Meilland, A.; Millour, F.; Robbe-Dubois,
S.; Schertl, D.; van Boekel, R.; Varga, J.; Woillez, J.
Bibcode: 2022A&A...663A..35I
Altcode: 2022arXiv220501575I
Context. Active galactic nuclei play a key role in the evolution of
galaxies, but their inner workings and physical connection to the host
are poorly understood due to a lack of angular resolution. Infrared
interferometry makes it possible to resolve the circumnuclear
dust in the nearby Seyfert 2 galaxy, the Circinus Galaxy. Previous
observations have revealed complex structures and polar dust emission
but interpretation was limited to simple models. The new Multi AperTure
mid-Infrared Spectro-Scopic Experiment (MATISSE) makes it possible
to image these structures for the first time.
Aims: We aim to
precisely map the morphology and temperature of the dust surrounding
the supermassive black hole through interferometric imaging.
Methods: We observed the Circinus Galaxy with MATISSE at the Very
Large Telescope Interferometer (VLTI), producing 150 correlated flux
spectra and 100 closure phase spectra. The novel inclusion of closure
phases makes interferometric imaging possible for the first time. We
reconstructed images in the N-band at ∼10 mas resolution. We fit
blackbody functions with dust extinction to several aperture-extracted
fluxes from the images to produce a temperature distribution of central
dusty structures.
Results: We find significant substructure
in the circumnuclear dust: central unresolved flux of ∼0.5 Jy,
a thin disk 1.9 pc in diameter oriented along ∼45°, and a ∼4
× 1.5 pc polar emission extending orthogonal to the disk. The polar
emission exhibits patchiness, which we attribute to clumpy dust. Flux
enhancements to the east and west of the disk are seen for the first
time. We distinguish the temperature profiles of the disk and of the
polar emission: the disk shows a steep temperature gradient indicative
of denser material; the polar profile is flatter, indicating clumpiness
and/or lower dust density. The unresolved flux is fitted with a high
temperature, ∼370 K. The polar dust remains warm (∼200 K) out
to 1.5 pc from the disk. We attribute approximately 60% of the 12
μm flux to the polar dust, 10% to the disk, and 6% is unresolved;
the remaining flux was resolved out. The recovered morphology and
temperature distribution resembles modeling of accretion disks with
radiation-driven winds at large scales, but we placed new constraints on
the subparsec dust.
Conclusions: The spatially resolved subparsec
features imaged here place new constraints on the physical modeling
of circumnuclear dust in active galaxies; we show strong evidence that
the polar emission consists of dust clumps or filaments. The dynamics
of the structures and their role in the Unified Model remain to be
explored. This work makes use of ESO Programmes 099.B-0484(A),
0104.B-0064(A), 0104.B-0127(A), 106.214U.002, and 105.205M.001. The images in Fig. 3 are available at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A35
Title: The disk of FU Orionis viewed with MATISSE/VLTI. First
interferometric observations in L and M bands
Authors: Lykou, F.; Ábrahám, P.; Chen, L.; Varga, J.; Kóspál, Á.;
Matter, A.; Siwak, M.; Szabó, Zs. M.; Zhu, Z.; Liu, H. B.; Lopez, B.;
Allouche, F.; Augereau, J. -C.; Berio, P.; Cruzalèbes, P.; Dominik,
C.; Henning, Th.; Hofmann, K. -H.; Hogerheijde, M.; Jaffe, W. J.;
Kokoulina, E.; Lagarde, S.; Meilland, A.; Millour, F.; Pantin, E.;
Petrov, R.; Robbe-Dubois, S.; Schertl, D.; Scheuck, M.; van Boekel,
R.; Waters, L. B. F. M.; Weigelt, G.; Wolf, S.
Bibcode: 2022A&A...663A..86L
Altcode: 2022arXiv220510173L
Aims: We studied the accretion disk of the archetypal eruptive
young star FU Orionis with the use of mid-infrared interferometry,
which enabled us to resolve the innermost regions of the disk down
to a spatial resolution of 3 milliarcseconds (mas) in the L band,
that is, within 1 au of the protostar.
Methods: We used
the interferometric instrument MATISSE/VLTI to obtain observations
of FU Ori's disk in the L, M, and N bands with multiple baseline
configurations. We also obtained contemporaneous photometry in the
optical (UBVRIr'i'; SAAO and Konkoly Observatory) and near-infrared
(JHKs; NOT). Our results were compared with radiative
transfer simulations modeled by RADMC-3D.
Results: The disk of FU
Orionis is marginally resolved with MATISSE, suggesting that the region
emitting in the thermal infrared is rather compact. An upper limit
of ~1.3 ± 0.1 mas (in L) can be given for the diameter of the disk
region probed in the L band, corresponding to 0.5 au at the adopted
Gaia EDR3 distance. This represents the hot, gaseous region of the
accretion disk. The N-band data indicate that the dusty passive disk is
silicate-rich. Only the innermost region of said dusty disk is found to
emit strongly in the N band, and it is resolved at an angular size of
~5 mas, which translates to a diameter of about 2 au. The observations
therefore place stringent constraints for the outer radius of the inner
accretion disk. Dust radiative transfer simulations with RADMC-3D
provide adequate fits to the spectral energy distribution from the
optical to the submillimeter and to the interferometric observables when
opting for an accretion rate M ~ 2 × 10−5 M⊙
yr−1 and assuming M* = 0.6 M⊙, Most
importantly, the hot inner accretion disk's outer radius can be fixed at
0.3 au. The outer radius of the dusty disk is placed at 100 au, based
on constraints from scattered-light images in the literature. The dust
mass contained in the disk is 2.4 × 10−4 M⊙,
and for a typical gas-to-dust ratio of 100, the total mass in the disk
is approximately 0.02 M⊙. We did not find any evidence
for a nearby companion in the current interferometric data, and we
tentatively explored the case of disk misalignment. For the latter, our
modeling results suggest that the disk orientation is similar to that
found in previous imaging studies by ALMA. Should there be an asymmetry
in the very compact, inner accretion disk, this might be resolved at
even smaller spatial scales (≤1 mas). Based on observations
collected at the European Southern Observatory under ESO programs
0104.C-0782(B), 0104.C-0016(D), 0106.C-0501(D), and 0106.C-0501(F).
Title: NICER X-Ray Observations of Eta Carinae during Its Most Recent
Periastron Passage
Authors: Espinoza-Galeas, David; Corcoran, M. F.; Hamaguchi, K.;
Russell, C. M. P.; Gull, T. R.; Moffat, A. F. J.; Richardson, N. D.;
Weigelt, G.; Hillier, D. John; Damineli, Augusto; Stevens, Ian R.;
Madura, Thomas; Gendreau, K.; Arzoumanian, Z.; Navarete, Felipe
Bibcode: 2022ApJ...933..136E
Altcode: 2022arXiv220703457E
We report high-precision X-ray monitoring observations in the 0.4-10 keV
band of the luminous, long-period colliding wind binary Eta Carinae,
up to and through its most recent X-ray minimum/periastron passage in
2020 February. Eta Carinae reached its observed maximum X-ray flux
on 2020 January 7, at a flux level of 3.30 ×10-10 ergs
s-1 cm-2, followed by a rapid plunge to its
observed minimum flux, 0.03 × 10-10 ergs s-1
cm-2, near 2020 February 17. The NICER observations show an
X-ray recovery from the minimum of only ~16 days, the shortest X-ray
minimum observed so far. We provide new constraints for the "deep"
and "shallow" minimum intervals. Variations in the characteristic
X-ray temperatures of the hottest observed X-ray emission indicate
that the apex of the wind-wind "bow shock" enters the companion's
wind acceleration zone about 81 days before the start of the X-ray
minimum. There is a steplike increase in column density just before the
X-ray minimum, probably associated with the presence of dense clumps
near the shock apex. During the recovery and after, the column density
shows a smooth decline, which agrees with previous N H
measurements made by Swift at the same orbital phase, indicating that
the changes in the mass-loss rate are only a few percent over the
two cycles. Finally, we use the variations in the X-ray flux of the
outer ejecta seen by NICER to derive a kinetic X-ray luminosity of the
ejecta of ~1041 ergs s-1 near the time of the
"Great Eruption."
Title: VizieR Online Data Catalog: Circinus galaxy N-band VLTI/MATISSE
images (Isbell+, 2022)
Authors: Isbell, J. W.; Meisenheimer, K.; Pott, J. -U.; Stalevski,
M.; Tristram, K. R. W.; Sanchez-Bermudez, J.; Hofmann, K. -H.; Gamez
Rosas, V.; Jaffe, W.; Burtscher, L.; Leftley, J.; Petrov, R.; Lopez,
B.; Henning, T.; Weigelt, G.; Allouche, F.; Berio, P.; Bettonvil, F.;
Cruzalebes, P.; Dominik, C.; Heininger, M.; Hogerheijde, M.; Lagarde,
S.; Lehmitz, M.; Matter, A.; Meilland, A.; Millour, F.; Robbe-Dubois,
S.; Schertl, D.; van Boekel, R.; Varga, J.; Woillez, J.
Bibcode: 2022yCat..36630035I
Altcode:
Observations of the active galactic nucleus (AGN), Circinus, with
VLTI/MATISSE resulted in the reconstruction of images at seven
independent wavelength channels in the N-band. These images show
the circumnuclear dust and provide new details on constraints on the
structure commonly known as the AGN torus. The images were reconstructed
from 150 correlated flux and 100 closure phase measurements obtained in
March 2020, February 2021, and June 2021. The images were reconstructed
at 8.5, 8.9, 9.7, 10.5, 11.3, 12.0, and 12.7 micrometers. The images
are given in Fig. 3 of the paper. (2 data files).
Title: Competitive X-Ray and Optical Cooling in the Collisionless
Shocks of WR 140
Authors: Corcoran, Michael; Pollock, Andrew; Stevens, Ian; Russell,
Christopher; Hamaguchi, Kenji; Williams, Peredur; Moffat, Anthony;
Weigelt, Gerd; Shenavrin, Victor; Richardson, Noel; Espinoza Galeas,
David; Drake, Stephen
Bibcode: 2022HEAD...1911098C
Altcode:
WR 140 is a long-period, highly eccentric massive Wolf-Rayet star
binary system with exceptionally well-determined orbital and stellar
parameters. Bright, periodically-varying X-ray emission is primarily
generated in the hot shocked gas produced by the collision of the
winds of the WC7pd+O5.5fc component stars. We define and discuss the
X-ray variations in the context of the colliding-wind model using
time-resolved broad-band X-ray spectrometry from the RXTE, Swift, and
NICER observatories obtained over 20 years and nearly 1000 observations
through 3 consecutive 7.94-year orbital cycles including 3 periastron
passages. The X-ray luminosity varies as expected with the inverse
of the stellar separation over most of the orbit. Departures near
periastron from this simple dependence are produced when the shock
energy balance shifts to excess optical emission in CIII 5696 in
particular. We use X-ray column density measures in a point-source
approximation to determine mass-loss-rate estimates for both stars and
to constrain the overall system morphology. The absorbing-column maximum
coincides closely with inferior conjunction of the WC star and provides
evidence of the ion-reflection mechanism that underlie the formation
of collisionless shocks governed by magnetic fields probably generated
by the Weibel instability. Comparisons after periastron with K-band
emission and He I10830 absorption show that both are correlated with
the asymmetric X-ray absorption. The K-band monitoring shows that dust
appears within only a few days of periastron passage, suggesting that
the dust-forming gas is embedded within shocked gas near the stagnation
point. Comparisons with Eta Carinae show that X-ray flares seen there
in every orbit have not occurred in WR 140, suggesting the absence
of large-scale wind inhomogeneities. Soft emission appearing during
the X-ray minimum is relatively constant and therefore unlikely to be
produced by recombining plasma entrained in outflowing shocked gas.
Title: MATISSE, the VLTI mid-infrared imaging spectro-interferometer
Authors: Lopez, B.; Lagarde, S.; Petrov, R. G.; Jaffe, W.; Antonelli,
P.; Allouche, F.; Berio, P.; Matter, A.; Meilland, A.; Millour,
F.; Robbe-Dubois, S.; Henning, Th.; Weigelt, G.; Glindemann, A.;
Agocs, T.; Bailet, Ch.; Beckmann, U.; Bettonvil, F.; van Boekel, R.;
Bourget, P.; Bresson, Y.; Bristow, P.; Cruzalèbes, P.; Eldswijk,
E.; Fanteï Caujolle, Y.; González Herrera, J. C.; Graser, U.;
Guajardo, P.; Heininger, M.; Hofmann, K. -H.; Kroes, G.; Laun, W.;
Lehmitz, M.; Leinert, C.; Meisenheimer, K.; Morel, S.; Neumann, U.;
Paladini, C.; Percheron, I.; Riquelme, M.; Schoeller, M.; Stee, Ph.;
Venema, L.; Woillez, J.; Zins, G.; Ábrahám, P.; Abadie, S.; Abuter,
R.; Accardo, M.; Adler, T.; Alonso, J.; Augereau, J. -C.; Böhm, A.;
Bazin, G.; Beltran, J.; Bensberg, A.; Boland, W.; Brast, R.; Burtscher,
L.; Castillo, R.; Chelli, A.; Cid, C.; Clausse, J. -M.; Connot, C.;
Conzelmann, R. D.; Danchi, W. -C.; Delbo, M.; Drevon, J.; Dominik,
C.; van Duin, A.; Ebert, M.; Eisenhauer, F.; Flament, S.; Frahm, R.;
Gámez Rosas, V.; Gabasch, A.; Gallenne, A.; Garces, E.; Girard, P.;
Glazenborg, A.; Gonté, F. Y. J.; Guitton, F.; de Haan, M.; Hanenburg,
H.; Haubois, X.; Hocdé, V.; Hogerheijde, M.; ter Horst, R.; Hron,
J.; Hummel, C. A.; Hubin, N.; Huerta, R.; Idserda, J.; Isbell, J. W.;
Ives, D.; Jakob, G.; Jaskó, A.; Jochum, L.; Klarmann, L.; Klein,
R.; Kragt, J.; Kuindersma, S.; Kokoulina, E.; Labadie, L.; Lacour,
S.; Leftley, J.; Le Poole, R.; Lizon, J. -L.; Lopez, M.; Lykou, F.;
Mérand, A.; Marcotto, A.; Mauclert, N.; Maurer, T.; Mehrgan, L. H.;
Meisner, J.; Meixner, K.; Mellein, M.; Menut, J. L.; Mohr, L.; Mosoni,
L.; Navarro, R.; Nußbaum, E.; Pallanca, L.; Pantin, E.; Pasquini, L.;
Phan Duc, T.; Pott, J. -U.; Pozna, E.; Richichi, A.; Ridinger, A.;
Rigal, F.; Rivinius, Th.; Roelfsema, R.; Rohloff, R. -R.; Rousseau,
S.; Salabert, D.; Schertl, D.; Schuhler, N.; Schuil, M.; Shabun,
K.; Soulain, A.; Stephan, C.; Toledo, P.; Tristram, K.; Tromp, N.;
Vakili, F.; Varga, J.; Vinther, J.; Waters, L. B. F. M.; Wittkowski,
M.; Wolf, S.; Wrhel, F.; Yoffe, G.
Bibcode: 2022A&A...659A.192L
Altcode: 2021arXiv211015556L
Context. Optical interferometry is at a key development stage. The
Very Large Telescope Interferometer (VLTI) has established a
stable, robust infrastructure for long-baseline interferometry
that is usable by general astronomical observers. The present
second-generation instruments offer a wide wavelength coverage and
improved performance. Their sensitivity and measurement accuracy
lead to data and images of high reliability.
Aims: We have
developed the Multi AperTure mid-Infrared SpectroScopic Experiment
(MATISSE) to access, for the first time, high resolution imaging
in a wide spectral domain. Many front-line topics are explored with
this new equipment, including: stellar activity and mass loss; planet
formation and evolution in the gas and dust disks around young stars;
and environment interaction and accretion processes around super massive
black holes in active galactic nuclei.
Methods: The instrument
is a spectro-interferometric imager in the transmission windows called
L, M, and N, from 2.8 to 13.0 microns, combining four optical beams
from the VLTI's unit or auxiliary telescopes. Its concept, related
observing procedure, data reduction, and calibration approach, is the
product of 30 years of instrumental research and has benefitted from
the expertise developed in the frame of the VLTI's first generation
instruments. The instrument utilises a multi-axial beam combination
that delivers spectrally dispersed fringes. The signal provides the
following quantities at several spectral resolutions: photometric flux,
coherent fluxes, visibilities, closure phases, wavelength differential
visibilities and phases, and aperture-synthesis imaging.
Results:
This article provides an overview of the physical principle of the
instrument and its functionalities. The motivation of the choice of the
instrumental concept and the characteristics of the delivered signal
are detailed with a description of the observing modes and of their
performance limit. MATISSE offers four spectral resolutions in L&M
bands, namely 30, 500, 1000 and 3400, and 30 and 220 in the N band,
and it provides an angular resolution down to 3 mas for the shortest
wavelengths. The MATISSE stand-alone sensitivity limits are 60 mJy in
L and 300 mJy in N. The paper gives details of the sensitivity limits
for the different measurables and their related precision criteria,
considering telescope configurations and spectral resolutions. We
also discuss the gain provided with the GRA4MAT fringe tracker. An
ensemble of data and reconstructed images illustrate the first
acquired key observations.
Conclusions: The instrument has
been in operation at Cerro Paranal, ESO, Chile, since 2018, and has
been open for science use by the international community since April
2019. The first scientific results are being published now.
Title: Improving the diameters of interferometric calibrators
with MATISSE
Authors: Robbe-Dubois, S.; Cruzalèbes, P.; Berio, Ph; Meilland, A.;
Petrov, R. -G.; Allouche, F.; Salabert, D.; Paladini, C.; Matter,
A.; Millour, F.; Lagarde, S.; Lopez, B.; Burtscher, L.; Jaffe, W.;
Hron, J.; Percheron, I.; van Boekel, R.; Weigelt, G.; Stee, Ph
Bibcode: 2022MNRAS.510...82R
Altcode: 2021MNRAS.tmp.3025R; 2022arXiv220100747R
A good knowledge of the angular diameters of stars used to calibrate the
observables in stellar interferometry is fundamental. As the available
precision for giant stars is worse than the required per cent level, we
aim to improve the knowledge of many diameters using MATISSE (Multiple
AperTure mid-Infrared SpectroScopic Experiment) data in its different
instrumental configurations. Using the squared visibility MATISSE
observable, we compute the angular diameter value, which ensures the
best-fitting curves, assuming an intensity distribution of a uniform
disc. We take into account that the transfer function varies over the
wavelength and is different from one instrumental configuration to
another. The uncertainties on the diameters are estimated using the
residual bootstrap method. Using the low spectral resolution mode in
the Lband, we observed a set of 35 potential calibrators selected in
the Mid-infrared stellar Diameter and Flux Compilation Catalogue with
diameters ranging from about 1 to 3 mas. We reach a precision on the
diameter estimates in the range 0.6 per cent to 4.1 per cent. The study
of the stability of the transfer function in visibility over two nights
makes us confident in our results. In addition, we identify one star,
75 Vir initially present in the calibrator lists, for which our method
does not converge, and prove to be a binary star. This leads us to
the conclusion that our method is actually necessary to improve the
quality of the astrophysical results obtained with MATISSE, and that
it can be used as a useful tool for 'bad calibrator' detection.
Title: Thermal imaging of dust hiding the black hole in NGC 1068
Authors: Gámez Rosas, Violeta; Isbell, Jacob W.; Jaffe, Walter;
Petrov, Romain G.; Leftley, James H.; Hofmann, Karl-Heinz; Millour,
Florentin; Burtscher, Leonard; Meisenheimer, Klaus; Meilland, Anthony;
Waters, Laurens B. F. M.; Lopez, Bruno; Lagarde, Stéphane; Weigelt,
Gerd; Berio, Philippe; Allouche, Fatme; Robbe-Dubois, Sylvie;
Cruzalèbes, Pierre; Bettonvil, Felix; Henning, Thomas; Augereau,
Jean-Charles; Antonelli, Pierre; Beckmann, Udo; van Boekel, Roy;
Bendjoya, Philippe; Danchi, William C.; Dominik, Carsten; Drevon,
Julien; Gallimore, Jack F.; Graser, Uwe; Heininger, Matthias;
Hocdé, Vincent; Hogerheijde, Michiel; Hron, Josef; Impellizzeri,
Caterina M. V.; Klarmann, Lucia; Kokoulina, Elena; Labadie, Lucas;
Lehmitz, Michael; Matter, Alexis; Paladini, Claudia; Pantin, Eric;
Pott, Jörg-Uwe; Schertl, Dieter; Soulain, Anthony; Stee, Philippe;
Tristram, Konrad; Varga, Jozsef; Woillez, Julien; Wolf, Sebastian;
Yoffe, Gideon; Zins, Gerard
Bibcode: 2022Natur.602..403G
Altcode: 2021arXiv211213694G
In the widely accepted `unified model'1 solution of the
classification puzzle of active galactic nuclei, the orientation of a
dusty accretion torus around the central black hole dominates their
appearance. In `type-1' systems, the bright nucleus is visible at
the centre of a face-on torus. In `type-2' systems the thick, nearly
edge-on torus hides the central engine. Later studies suggested
evolutionary effects2 and added dusty clumps and polar
winds3 but left the basic picture intact. However, recent
high-resolution images4 of the archetypal type-2 galaxy
NGC 10685,6, suggested a more radical revision. The images
displayed a ring-like emission feature that was proposed to be hot dust
surrounding the black hole at the radius where the radiation from the
central engine evaporates the dust. That ring is too thin and too far
tilted from edge-on to hide the central engine, and ad hoc foreground
extinction is needed to explain the type-2 classification. These images
quickly generated reinterpretations of the dichotomy between types 1
and 27,8. Here we present new multi-band mid-infrared images
of NGC 1068 that detail the dust temperature distribution and reaffirm
the original model. Combined with radio data (J.F.G. and C.M.V.I.,
manuscript in preparation), our maps locate the central engine that
is below the previously reported ring and obscured by a thick, nearly
edge-on disk, as predicted by the unified model. We also identify
emission from polar flows and absorbing dust that is mineralogically
distinct from that towards the Milky Way centre.
Title: The extended atmosphere and circumstellar environment of the
cool evolved star VX Sagittarii as seen by MATISSE
Authors: Chiavassa, A.; Kravchenko, K.; Montargès, M.; Millour, F.;
Matter, A.; Freytag, B.; Wittkowski, M.; Hocdé, V.; Cruzalèbes, P.;
Allouche, F.; Lopez, B.; Lagarde, S.; Petrov, R. G.; Meilland, A.;
Robbe-Dubois, S.; Hofmann, K. -H.; Weigelt, G.; Berio, P.; Bendjoya,
P.; Bettonvil, F.; Domiciano de Souza, A.; Heininger, M.; Henning, Th.;
Isbell, J. W.; Jaffe, W.; Labadie, L.; Lehmitz, M.; Meisenheimer, K.;
Soulain, A.; Varga, J.; Augereau, J. -C.; van Boekel, R.; Burtscher,
L.; Danchi, W. C.; Dominik, C.; Drevon, J.; Gámez Rosas, V.;
Hogerheijde, M. R.; Hron, J.; Klarmann, L.; Kokoulina, E.; Lagadec,
E.; Leftley, J.; Mosoni, L.; Nardetto, N.; Paladini, C.; Pantin, E.;
Schertl, D.; Stee, P.; Szabados, L.; Waters, R.; Wolf, S.; Yoffe, G.
Bibcode: 2022A&A...658A.185C
Altcode: 2021arXiv211210695C
Context. VX Sgr is a cool, evolved, and luminous red star whose
stellar parameters are difficult to determine, which affects
its classification.
Aims: We aim to spatially resolve the
photospheric extent as well as the circumstellar environment.
Methods: We used interferometric observations obtained with
the MATISSE instrument in the L (3-4 μm), M (4.5-5 μm), and N
(8-13 μm) bands. We reconstructed monochromatic images using
the MIRA software. We used 3D radiation-hydrodynamics simulations
carried out with CO5BOLD and a uniform disc model to
estimate the apparent diameter and interpret the stellar surface
structures. Moreover, we employed the radiative transfer codes OPTIM3D
and RADMC3D to compute the spectral energy distribution for the L,
M, and N bands, respectively.
Results: MATISSE observations
unveil, for the first time, the morphology of VX Sgr across the L, M,
and N bands. The reconstructed images show a complex morphology with
brighter areas whose characteristics depend on the wavelength probed. We
measured the angular diameter as a function of the wavelength and
showed that the photospheric extent in the L and M bands depends on the
opacity through the atmosphere. In addition to this, we also concluded
that the observed photospheric inhomogeneities can be interpreted
as convection-related surface structures. The comparison in the N
band yielded a qualitative agreement between the N-band spectrum
and simple dust radiative transfer simulations. However, it is not
possible to firmly conclude on the interpretation of the current
data because of the difficulty in constraing the model parameters
using the limited accuracy of our absolute flux calibration.
Conclusions: MATISSE observations and the derived reconstructed images
unveil the appearance of VX Sgr's stellar surface and circumstellar
environment across a very large spectral domain for the first time. Based on the observations made with VLTI-ESO Paranal, Chile under
the programme IDs 0103.D-0153(D, E, G). The data are available at oidb.jmmc.fr
Title: VLTI-MATISSE L- and N-band aperture-synthesis imaging of the
unclassified B[e] star FS Canis Majoris
Authors: Hofmann, K. -H.; Bensberg, A.; Schertl, D.; Weigelt, G.;
Wolf, S.; Meilland, A.; Millour, F.; Waters, L. B. F. M.; Kraus,
S.; Ohnaka, K.; Lopez, B.; Petrov, R. G.; Lagarde, S.; Berio, Ph.;
Allouche, F.; Robbe-Dubois, S.; Jaffe, W.; Henning, Th.; Paladini, C.;
Schöller, M.; Mérand, A.; Glindemann, A.; Beckmann, U.; Heininger,
M.; Bettonvil, F.; Zins, G.; Woillez, J.; Bristow, P.; Stee, P.;
Vakili, F.; van Boekel, R.; Hogerheijde, M. R.; Dominik, C.; Augereau,
J. -C.; Matter, A.; Hron, J.; Pantin, E.; Rivinius, Th.; de Wit,
W. -J.; Varga, J.; Klarmann, L.; Meisenheimer, K.; Gámez Rosas,
V.; Burtscher, L.; Leftley, J.; Isbell, J. W.; Yoffe, G.; Kokoulina,
E.; Danchi, W. C.; Cruzalèbes, P.; Domiciano de Souza, A.; Drevon,
J.; Hocdé, V.; Kreplin, A.; Labadie, L.; Connot, C.; Nußbaum, E.;
Lehmitz, M.; Antonelli, P.; Graser, U.; Leinert, C.
Bibcode: 2022A&A...658A..81H
Altcode: 2021arXiv211112458H
Context. FS Canis Majoris (FS CMa, HD 45677) is an unclassified B[e]
star surrounded by an inclined dust disk. The evolutionary stage of
FS CMa is still debated. Perpendicular to the circumstellar disk,
a bipolar outflow was detected. Infrared aperture-synthesis imaging
provides us with a unique opportunity to study the disk structure.
Aims: Our aim is to study the intensity distribution of the
disk of FS CMa in the mid-infrared L and N bands.
Methods:
We performed aperture-synthesis imaging of FS CMa with the MATISSE
instrument (Multi AperTure mid-Infrared SpectroScopic Experiment)
in the low spectral resolution mode to obtain images in the L and N
bands. We computed radiative transfer models that reproduce the L-
and N-band intensity distributions of the resolved disks.
Results: We present L- and N-band aperture-synthesis images of FS CMa
reconstructed in the wavelength bands of 3.4-3.8 and 8.6-9.0 μm. In
the L-band image, the inner rim region of an inclined circumstellar
disk and the central object can be seen with a spatial resolution of
2.7 milliarcsec (mas). An inner disk cavity with an angular diameter
of ~6 × 12 mas is resolved. The L-band disk consists of a bright
northwestern (NW) disk region and a much fainter southeastern (SE)
region. The images suggest that we are looking at the bright inner
wall of the NW disk rim, which is on the far side of the disk. In the N
band, only the bright NW disk region is seen. In addition to deriving
the inclination and the inner disk radius, fitting the reconstructed
brightness distributions via radiative transfer modelling allows one
to constrain the innermost disk structure, in particular the shape of
theinner disk rim. Based on observations collected at the European
Organisation for Astronomical Research in the Southern Hemisphere within
the commissioning of the VLTI-MATISSE instrument (ID 60.A-9257(E)).
Title: Eta Carinae: A Tale of Two Periastron Passages
Authors: Gull, Theodore R.; Navarete, Felipe; Corcoran, Michael F.;
Damineli, Augusto; Espinoza, David; Hamaguchi, Kenji; Hartman, Henrik;
Hillier, D. John; Madura, Thomas; Moffat, Anthony F. J.; Morris,
Patrick; Nielsen, Krister; Pittard, Julian M.; Pollock, Andrew M. T.;
Richardson, Noel D.; Russell, Christopher M. P.; Stevens, Ian R.;
Weigelt, Gerd
Bibcode: 2021ApJ...923..102G
Altcode:
Since 2002, the far-ultraviolet (FUV) flux (1150-1680 Å) of Eta
Carinae, monitored by the Hubble Space Telescope/Space Telescope
Imaging Spectrograph, has increased by an order of magnitude. This
increase is attributed to partial dissipation of a line-of-sight
(LOS) occulter that blocks the central core of the system. Across
the 2020 February periastron passage, changes in the FUV emission
show a stronger wavelength dependence than occurred across the 2003
July periastron passage. Across both periastron passages, most of the
FUV spectrum dropped in flux then recovered a few months later. The
2020 periastron passage included enhancements of FUV flux in narrow
spectral intervals near periastron followed by a transient absorption
and recovery to pre-periastron flux levels. The drop in flux is due
to increased absorption by singly ionized species as the secondary
star plunges deep into the wind of the primary star, which blocks the
companion's ionizing radiation. The enhanced FUV emission is caused by
the companion's wind-blown cavity briefly opening a window to deeper
layers of the primary star. This is the first time transient brightening
has been seen in the FUV comparable to transients previously seen at
longer wavelengths. Changes in resonance line-velocity profiles hint
that the dissipating occulter is associated with material in LOS moving
at -100 to -300 km s-1, similar in velocity of structures
previously associated with the 1890s lesser eruption.
Title: Competitive X-Ray and Optical Cooling in the Collisionless
Shocks of WR 140
Authors: Pollock, A. M. T.; Corcoran, M. F.; Stevens, I. R.; Russell,
C. M. P.; Hamaguchi, K.; Williams, P. M.; Moffat, A. F. J.; Weigelt,
G.; Shenavrin, V.; Richardson, N. D.; Espinoza, D.; Drake, S. A.
Bibcode: 2021ApJ...923..191P
Altcode: 2021arXiv210910350P
The long-period, highly eccentric Wolf-Rayet star binary system
WR 140 has exceptionally well-determined orbital and stellar
parameters. Bright, variable X-ray emission is generated in
shocks produced by the collision of the winds of the WC7pd+O5.5fc
component stars. We discuss the variations in the context of the
colliding-wind model using broadband spectrometry from the RXTE,
Swift, and NICER observatories obtained over 20 yr and nearly 1000
observations through three consecutive 7.94 yr orbits, including
three periastron passages. The X-ray luminosity varies as expected
with the inverse of the stellar separation over most of the orbit;
departures near periastron are produced when cooling shifts to
excess optical emission in C III λ5696 in particular. We use
X-ray absorption to estimate mass-loss rates for both stars and to
constrain the system morphology. The absorption maximum coincides
closely with the inferior conjunction of the WC star and provides
evidence of the ion-reflection mechanism that underlies the formation
of collisionless shocks governed by magnetic fields probably generated
by the Weibel instability. Comparisons with K-band emission and He
I λ10830 absorption show that both are correlated after periastron
with the asymmetric X-ray absorption. Dust appears within a few days of
periastron, suggesting formation within shocked gas near the stagnation
point. The X-ray flares seen in η Car have not occurred in WR 140,
suggesting the absence of large-scale wind inhomogeneities. Relatively
constant soft emission revealed during the X-ray minimum is probably
not from recombining plasma entrained in outflowing shocked gas.
Title: First MATISSE L-band observations of HD 179218. Is the inner
10 au region rich in carbon dust particles?
Authors: Kokoulina, E.; Matter, A.; Lopez, B.; Pantin, E.; Ysard, N.;
Weigelt, G.; Habart, E.; Varga, J.; Jones, A.; Meilland, A.; Dartois,
E.; Klarmann, L.; Augereau, J. -C.; van Boekel, R.; Hogerheijde, M.;
Yoffe, G.; Waters, L. B. F. M.; Dominik, C.; Jaffe, W.; Millour, F.;
Henning, Th.; Hofmann, K. -H.; Schertl, D.; Lagarde, S.; Petrov,
R. G.; Antonelli, P.; Allouche, F.; Berio, P.; Robbe-Dubois, S.;
Ábraham, P.; Beckmann, U.; Bensberg, A.; Bettonvil, F.; Bristow, P.;
Cruzalèbes, P.; Danchi, W. C.; Dannhoff, M.; Graser, U.; Heininger,
M.; Labadie, L.; Lehmitz, M.; Leinert, C.; Meisenheimer, K.; Paladini,
C.; Percheron, I.; Stee, Ph.; Woillez, J.; Wolf, S.; Zins, G.; Delbo,
M.; Drevon, J.; Duprat, J.; Gámez Rosas, V.; Hocdé, V.; Hron, J.;
Hummel, C. A.; Isbell, J. W.; Leftley, J.; Soulain, A.; Vakili, F.;
Wittkowski, M.
Bibcode: 2021A&A...652A..61K
Altcode: 2021arXiv210612947K
Context. Carbon is one of the most abundant components in the
Universe. While silicates have been the main focus of solid phase
studies in protoplanetary discs (PPDs), little is known about the
solid carbon content especially in the planet-forming regions (~0.1-10
au). Fortunately, several refractory carbonaceous species present C-H
bonds (such as hydrogenated nano-diamond and amorphous carbon as well
as polycyclic aromatic hydrocarbons), which generate infrared (IR)
features that can be used to trace the solid carbon reservoirs. The
new mid-IR instrument MATISSE, installed at the Very Large Telescope
Interferometer (VLTI), can spatially resolve the inner regions (~1-10
au) of PPDs and locate, down to the au-scale, the emission coming
from carbon grains.
Aims: Our aim is to provide a consistent
view on the radial structure, down to the au-scale, as well as basic
physical properties and the nature of the material responsible for the
IR continuum emission in the inner disk region around HD 179218.
Methods: We implemented a temperature-gradient model to interpret
the disk IR continuum emission, based on a multiwavelength dataset
comprising a broadband spectral energy distribution and VLTI H-, L-, and
N-bands interferometric data obtained in low spectral resolution. Then,
we added a ring-like component, representing the carbonaceous L-band
features-emitting region, to assess its detectability in future higher
spectral resolution observations employing mid-IR interferometry.
Results: Our temperature-gradient model can consistently reproduce our
dataset. We confirmed a spatially extended inner 10 au emission in H-
and L-bands, with a homogeneously high temperature (~1700 K), which we
associate with the presence of stochastically heated nano-grains. On the
other hand, the N-band emitting region presents a ring-like geometry
that starts at about 10 au with a temperature of 400 K. Moreover, the
existing low resolution MATISSE data exclude the presence of aromatic
carbon grains (i.e., producing the 3.3 μm feature) in close proximity
tothe star (≲1 au). Future medium spectral resolution MATISSE data
will confirm their presence at larger distances.
Conclusions:
Our best-fit model demonstrates the presence of two separated dust
populations: nano-grains that dominate the near- to mid-IR emission
in the inner 10 au region and larger grains that dominate the emission
outward. The presence of such nano-grains in the highly irradiated inner
10 au region of HD 179218 requires a replenishment process. Considering
the expected lifetime of carbon nano-grains from The Heterogeneous dust
Evolution Model for Interstellar Solids (THEMIS model), the estimated
disk accretion inflow of HD 179218 could significantly contribute to
feed the inner 10 au region in nano-grains.Moreover, we also expect a
local regeneration of those nano-grains by the photo-fragmentation of
larger aggregates. Based on observations collected at the European
Southern Observatory, Chile (ESO ID: 0103.D-0069).
Title: VLTI-MATISSE chromatic aperture-synthesis imaging of η
Carinae's stellar wind across the Brα line. Periastron passage
observations in February 2020
Authors: Weigelt, G.; Hofmann, K. -H.; Schertl, D.; Lopez, B.;
Petrov, R. G.; Lagarde, S.; Berio, Ph.; Jaffe, W.; Henning, Th.;
Millour, F.; Meilland, A.; Allouche, F.; Robbe-Dubois, S.; Matter,
A.; Cruzalèbes, P.; Hillier, D. J.; Russell, C. M. P.; Madura, T.;
Gull, T. R.; Corcoran, M. F.; Damineli, A.; Moffat, A. F. J.; Morris,
P. W.; Richardson, N. D.; Paladini, C.; Schöller, M.; Mérand, A.;
Glindemann, A.; Beckmann, U.; Heininger, M.; Bettonvil, F.; Zins, G.;
Woillez, J.; Bristow, P.; Sanchez-Bermudez, J.; Ohnaka, K.; Kraus,
S.; Mehner, A.; Wittkowski, M.; Hummel, C. A.; Stee, P.; Vakili, F.;
Hartman, H.; Navarete, F.; Hamaguchi, K.; Espinoza-Galeas, D. A.;
Stevens, I. R.; van Boekel, R.; Wolf, S.; Hogerheijde, M. R.; Dominik,
C.; Augereau, J. -C.; Pantin, E.; Waters, L. B. F. M.; Meisenheimer,
K.; Varga, J.; Klarmann, L.; Gámez Rosas, V.; Burtscher, L.; Leftley,
J.; Isbell, J. W.; Hocdé, V.; Yoffe, G.; Kokoulina, E.; Hron, J.;
Groh, J.; Kreplin, A.; Rivinius, Th.; de Wit, W. -J.; Danchi, W. -C.;
Domiciano de Souza, A.; Drevon, J.; Labadie, L.; Connot, C.; Nußbaum,
E.; Lehmitz, M.; Antonelli, P.; Graser, U.; Leinert, C.
Bibcode: 2021A&A...652A.140W
Altcode:
Context. Eta Carinae is a highly eccentric, massive binary
system (semimajor axis ~15.5 au) with powerful stellar winds and
a phase-dependent wind-wind collision (WWC) zone. The primary
star, η Car A, is a luminous blue variable (LBV); the secondary,
η Car B, is a Wolf-Rayet or O star with a faster but less dense
wind. Aperture-synthesis imaging allows us to study the mass loss from
the enigmatic LBV η Car. Understanding LBVs is a crucial step toward
improving our knowledge about massive stars and their evolution.
Aims: Our aim is to study the intensity distribution and kinematics of
η Car's WWC zone.
Methods: Using the VLTI-MATISSE mid-infrared
interferometry instrument, we perform Brα imaging of η Car's
distorted wind.
Results: We present the first VLTI-MATISSE
aperture-synthesis images of η Car A's stellar windin several spectral
channels distributed across the Brα 4.052 μm line (spectral resolving
power R ~ 960). Our observations were performed close to periastron
passage in February 2020 (orbital phase ~ 14.0022). The reconstructed
iso-velocity images show the dependence of the primary stellar
wind on wavelength or line-of-sight (LOS) velocity with a spatial
resolution of 6 mas (~14 au). The radius of the faintest outer wind
regions is ~26 mas (~60 au). At several negative LOS velocities, the
primary stellar wind is less extended to the northwest than in other
directions. This asymmetry is most likely caused by the WWC. Therefore,
we see both the velocity field of the undisturbed primary wind and the
WWC cavity. In continuum spectral channels, the primary star wind is
more compact than in line channels. A fit of the observed continuum
visibilities with the visibilities of a stellar wind CMFGEN model
(CMFGEN is an atmosphere code developed to model the spectra of a
variety of objects) provides a full width at half maximum fit diameter
of the primary stellar wind of 2.84 ± 0.06 mas (6.54 ± 0.14 au). We
comparethe derived intensity distributions with the CMFGEN stellar
wind model and hydrodynamic WWC models. Based on observations
collected at the European Organisation for Astronomical Research in
the Southern Hemisphere under ESO program 0104.D-0015A, 0104.D-0015B,
0104.D-0015C, 0106.D-0309(A), 0106.D-0309(B), and 0106.D-0309(C).
Title: The orbit and stellar masses of the archetype colliding-wind
binary WR 140
Authors: Thomas, Joshua D.; Richardson, Noel D.; Eldridge, J. J.;
Schaefer, Gail H.; Monnier, John D.; Sana, Hugues; Moffat, Anthony
F. J.; Williams, Peredur; Corcoran, Michael F.; Stevens, Ian R.;
Weigelt, Gerd; Zainol, Farrah D.; Anugu, Narsireddy; Le Bouquin,
Jean-Baptiste; ten Brummelaar, Theo; Campos, Fran; Couperus, Andrew;
Davies, Claire L.; Ennis, Jacob; Eversberg, Thomas; Garde, Oliver;
Gardner, Tyler; Fló, Joan Guarro; Kraus, Stefan; Labdon, Aaron;
Lanthermann, Cyprien; Leadbeater, Robin; Lester, T.; Maki, Courtney;
McBride, Brendan; Ozuyar, Dogus; Ribeiro, J.; Setterholm, Benjamin;
Stober, Berthold; Wood, Mackenna; Zurmühl, Uwe
Bibcode: 2021MNRAS.504.5221T
Altcode: 2021MNRAS.tmp.1194T; 2021arXiv210110563T
We present updated orbital elements for the Wolf-Rayet (WR) binary
WR 140 (HD 193793; WC7pd + O5.5fc). The new orbital elements were
derived using previously published measurements along with 160 new
radial velocity measurements across the 2016 periastron passage of
WR 140. Additionally, four new measurements of the orbital astrometry
were collected with the CHARA Array. With these measurements, we derive
stellar masses of $M_{\rm WR} = 10.31\pm 0.45 \, \mathrm{M}_\odot$ and
$M_{\rm O} = 29.27\pm 1.14 \, \mathrm{M}_{\odot }$. We also include a
discussion of the evolutionary history of this system from the Binary
Population and Spectral Synthesis model grid to show that this WR
star likely formed primarily through mass-loss in the stellar winds,
with only a moderate amount of mass lost or transferred through binary
interactions.
Title: Spectroscopic signatures of the vanishing natural coronagraph
of Eta Carinae
Authors: Damineli, A.; Navarete, F.; Hillier, D. J.; Moffat, A. F. J.;
Corcoran, M. F.; Gull, T. R.; Richardson, N. D.; Weigelt, G.; Morris,
P. W.; Stevens, I.
Bibcode: 2021MNRAS.505..963D
Altcode: 2021MNRAS.tmp.1370D; 2021arXiv210500590D
Eta Carinae is a massive interacting binary system shrouded in a complex
circumstellar environment whose evolution is the source of the long-term
brightening observed during the last 80 yr. An occulter, acting as a
natural coronagraph, impacts observations from our perspective, but
not from most other directions. Other sight-lines are visible to us
through studies of the Homunculus reflection nebula. The coronagraph
appears to be vanishing, decreasing the extinction towards the central
star, and causing the star's secular brightening. In contrast, the
Homunculus remains at an almost constant brightness. The coronagraph
primarily suppresses the stellar continuum, to a lesser extent the wind
lines, and not the circumstellar emission lines. This explains why the
absolute values of equivalent widths (EWs) of the emission lines in our
direct view are larger than those seen in reflected by the Homunculus,
why the direct view absolute EWs are decreasing with time, and why
lower-excitation spectral wind lines formed at larger radii (e.g Fe II
4585 Å) decrease in intensity at a faster pace than higher excitation
lines that form closer to the star (e.g. H δ). Our main result is
that the star, despite its 10-fold brightening over two decades, is
relatively stable. A vanishing coronagraph that can explain both the
large flux evolution and the much weaker spectral evolution. This is
contrary to suggestions that the long-term variability is intrinsic
to the primary star that is still recovering from the Great Eruption
with a decreasing mass-loss rate and a polar wind that is evolving at
a slower pace than at the equator.
Title: Mid-infrared circumstellar emission of the long-period Cepheid
ℓ Carinae resolved with VLTI/MATISSE
Authors: Hocdé, V.; Nardetto, N.; Matter, A.; Lagadec, E.; Mérand,
A.; Cruzalèbes, P.; Meilland, A.; Millour, F.; Lopez, B.; Berio,
P.; Weigelt, G.; Petrov, R.; Isbell, J. W.; Jaffe, W.; Kervella, P.;
Glindemann, A.; Schöller, M.; Allouche, F.; Gallenne, A.; Domiciano
de Souza, A.; Niccolini, G.; Kokoulina, E.; Varga, J.; Lagarde, S.;
Augereau, J. -C.; van Boekel, R.; Bristow, P.; Henning, Th.; Hofmann,
K. -H.; Zins, G.; Danchi, W. -C.; Delbo, M.; Dominik, C.; Gámez
Rosas, V.; Klarmann, L.; Hron, J.; Hogerheijde, M. R.; Meisenheimer,
K.; Pantin, E.; Paladini, C.; Robbe-Dubois, S.; Schertl, D.; Stee,
P.; Waters, R.; Lehmitz, M.; Bettonvil, F.; Heininger, M.; Bristow,
P.; Woillez, J.; Wolf, S.; Yoffe, G.; Szabados, L.; Chiavassa, A.;
Borgniet, S.; Breuval, L.; Javanmardi, B.; Ábrahám, P.; Abadie, S.;
Abuter, R.; Accardo, M.; Adler, T.; Agócs, T.; Alonso, J.; Antonelli,
P.; Böhm, A.; Bailet, C.; Bazin, G.; Beckmann, U.; Beltran, J.;
Boland, W.; Bourget, P.; Brast, R.; Bresson, Y.; Burtscher, L.;
Buter, R.; Castillo, R.; Chelli, A.; Cid, C.; Clausse, J. -M.; Connot,
C.; Conzelmann, R. D.; De Haan, M.; Ebert, M.; Elswijk, E.; Fantei,
Y.; Frahm, R.; Gámez Rosas, V.; Gabasch, A.; Garces, E.; Girard,
P.; Glazenborg, A.; Gonté, F. Y. J.; González Herrera, J. C.;
Graser, U.; Guajardo, P.; Guitton, F.; Hanenburg, H.; Haubois, X.;
Hubin, N.; Huerta, R.; Idserda, J.; Ives, D.; Jakob, G.; Jaskó,
A.; Jochum, L.; Klein, R.; Kragt, J.; Kroes, G.; Kuindersma, S.;
Labadie, L.; Laun, W.; Le Poole, R.; Leinert, C.; Lizon, J. -L.;
Lopez, M.; Marcotto, A.; Mauclert, N.; Maurer, T.; Mehrgan, L. H.;
Meisner, J.; Meixner, K.; Mellein, M.; Mohr, L.; Morel, S.; Mosoni,
L.; Navarro, R.; Neumann, U.; Nußbaum, E.; Pallanca, L.; Pasquini,
L.; Percheron, I.; Phan Duc, T.; Pott, J. -U.; Pozna, E.; Ridinger,
A.; Rigal, F.; Riquelme, M.; Rivinius, Th.; Roelfsema, R.; Rohloff,
R. -R.; Rousseau, S.; Schuhler, N.; Schuil, M.; Shabun, K.; Soulain,
A.; Stephan, C.; ter Horst, R.; Tromp, N.; Vakili, F.; van Duin, A.;
Venema, L. B.; Vinther, J.; Wittkowski, M.; Wrhel, F.
Bibcode: 2021A&A...651A..92H
Altcode: 2021arXiv210317014H
Context. The nature of circumstellar envelopes (CSEs) around Cepheids
is a matter of ongoing debate. The physical origin of their infrared
(IR) excess could be shown to either be made up of a shell of ionized
gas, a dust envelope, or a combination of both.
Aims: This
study is aimed at constraining the geometry and the IR excess of the
environment of the bright long-period Cepheid ℓ Car (P = 35.5 days)
at mid-IR wavelengths in order to understand its physical nature.
Methods: We first used photometric observations in various bands
(from the visible domain to the infrared) and Spitzer Space Telescope
spectroscopy to constrain the IR excess of ℓ Car. Then we analyzed
the VLTI/MATISSE measurements at a specific phase of observation
in order to determine the flux contribution as well as the size and
shape of the environment of the star in the L band. Finally, we tested
the hypothesis of a shell of ionized gas in order to model the IR
excess.
Results: We report the first detection in the L band
of a centro-symmetric extended emission around ℓ Car, of about 1.7
R⋆ in full width at half maximum, producing an excess of
about 7.0% in this band.This latter value is used to calibrate the IR
excess found when comparing the photometric observations in various
bands and quasi-static atmosphere models. In the N band, there is no
clear evidence for dust emission from VLTI/MATISSE correlated flux
and Spitzer data. On the other side, the modeled shell of ionized
gas implies a more compact CSE (1.13 ± 0.02 R⋆) that
is also fainter (IR excess of 1% in the L band).
Conclusions:
We provide new evidence supporting a compact CSE for ℓ Car and we
demonstrate the capabilities of VLTI/MATISSE for determining common
properties of CSEs. While the compact CSE of ℓ Car is likely to be
of a gaseous nature, the tested model of a shell of ionized gas is not
able to simultaneously reproduce the IR excess and the interferometric
observations. Further Galactic Cepheid observations with VLTI/MATISSE
are necessary for determining the properties of CSEs, which may also
depend on both the pulsation period and the evolutionary state of the
stars. Based on observations made with ESO telescopes at Paranal
observatory under program ID 0104.D-0554(A).
Title: Conditions in the WR 140 wind-collision region revealed by
the 1.083-μ m He I line profile
Authors: Williams, Peredur M.; Varricatt, Watson P.; Chené,
André-Nicolas; Corcoran, Michael F.; Gull, Ted R.; Hamaguchi, Kenji;
Moffat, Anthony F. J.; Pollock, Andrew M. T.; Richardson, Noel D.;
Russell, Christopher M. P.; Sander, Andreas A. C.; Stevens, Ian R.;
Weigelt, Gerd
Bibcode: 2021MNRAS.503..643W
Altcode: 2021MNRAS.tmp..528W; 2021arXiv210209445W
We present spectroscopy of the P Cygni profile of the 1.083-$\mu$m
He I line in the WC7+O5 colliding-wind binary (CWB) WR 140 (HD
193793), observed in 2008, before its periastron passage in 2009,
and in 2016-2017, spanning the subsequent periastron passage. Both
absorption and emission components showed strong variations. The
variation of the absorption component as the O5 star was occulted
by the wind-collision region (WCR) sets a tight constraint on its
geometry. While the sightline to the O5 star traversed the WCR, the
strength and breadth of the absorption component varied significantly
on time-scales of days. An emission subpeak was observed on all our
profiles. The variation of its radial velocity with orbital phase was
shown to be consistent with formation in the WCR as it swung round
the stars in their orbit. Modelling the profile gives a measure
of the extent of the subpeak-forming region. In the phase range
0.93-0.99, the flux in the subpeak increased steadily, approximately
inversely proportionally to the stellar separation, indicating that the
shocked gas in the WCR where the line was formed was adiabatic. After
periastron, the subpeak flux was anomalously strong and varied rapidly,
suggesting formation in clumps downstream in the WCR. For most of the
time, its flux exceeded the 2-10-keV X-ray emission, showing it to be
a significant coolant of the shocked wind.
Title: VizieR Online Data Catalog: Vanishing natural coronagraph of
eta Car (Damineli+, 2021)
Authors: Damineli, A.; Navarete, F.; Hillier, D. J.; Moffat, A. J.;
Corcoran, M. F.; Gull, T. R.; Richardson, N. D.; Weigelt, G.; Morris,
P. W.; Stevens, I.
Bibcode: 2021yCat..75050963D
Altcode:
These are the full versions of Tables A3, A4 and A5 of the
manuscript. (3 data files).
Title: Confirming the First Low-Metallicity Wolf-Rayet Dust Factory
Authors: Lau, Ryan M.; Bond, Howard E.; Corcoran, Michael F.; Endo,
Izumi; Hankins, Matthew J.; Jencson, Jacob; Jones, Olivia; Kasliwal,
Mansi; Lamberts, Astrid; Moffat, Anthony F. J.; Morris, Patrick W.;
Onaka, Takashi; Ressler, Michael E.; Richardson, Noel D.; Russell,
Christopher Michael Post; Sakon, Itsuki; Weigelt, Gerd; Williams,
Peredur
Bibcode: 2021jwst.prop.1863L
Altcode:
In our current understanding of dust-forming sources, we cannot
account for the observed quantities of dust in local and high-redshift
galaxies. Recent studies indicate that the answer to this long-standing
mystery may include carbon-rich Wolf-Rayet (WC) stars. Theoretical
models predict that WC stars can even be significant sources of
dust at sub-solar metallicity, consistent with the lower metallicity
environment of galaxies beyond the local Universe. However, there is
a dearth of known dust-forming WC binaries at sub-solar metallicity to
verify the model predictions. New results from the Spitzer Space
Telescope have identified an IR-luminous outburst named SPIRITS 19q,
which exhibited highly efficient dust production likely linked to a
dust-formation episode from an extragalactic WC system in the subsolar
metallicity outskirts of the nearby galaxy NGC 2403. This tentative link
between SPIRITS 19q and the WC star has not yet been confirmed due to
the unresolved nature of the luminous stellar cluster coincident with
19q. In this proposal, we request 6.74 hours of spectroscopic imaging
observations with the NIRSpec IFU between 0.6 - 5.3 microns at R ~
100 in order to confirm dust formation from the WC star by spatially
resolving and identifying the near-IR (1 - 2 micron) spectroscopic
features associated with the WC star and the mid-IR (3 - 5 micron)
emission associated with the SPIRITS 19q. Efficient dust-formation
from just one WC system can have a significant impact on the ISM,
and confirmation of efficient dust formation from this WC star would
validate the theoretical models that demonstrate WC stars as significant
sources of dust at sub-solar metallicity.
Title: The asymmetric inner disk of the Herbig Ae star HD 163296 in
the eyes of VLTI/MATISSE: evidence for a vortex?
Authors: Varga, J.; Hogerheijde, M.; van Boekel, R.; Klarmann, L.;
Petrov, R.; Waters, L. B. F. M.; Lagarde, S.; Pantin, E.; Berio,
Ph.; Weigelt, G.; Robbe-Dubois, S.; Lopez, B.; Millour, F.; Augereau,
J. -C.; Meheut, H.; Meilland, A.; Henning, Th.; Jaffe, W.; Bettonvil,
F.; Bristow, P.; Hofmann, K. -H.; Matter, A.; Zins, G.; Wolf, S.;
Allouche, F.; Donnan, F.; Schertl, D.; Dominik, C.; Heininger, M.;
Lehmitz, M.; Cruzalèbes, P.; Glindemann, A.; Meisenheimer, K.;
Paladini, C.; Schöller, M.; Woillez, J.; Venema, L.; Kokoulina,
E.; Yoffe, G.; Ábrahám, P.; Abadie, S.; Abuter, R.; Accardo, M.;
Adler, T.; Agócs, T.; Antonelli, P.; Böhm, A.; Bailet, C.; Bazin, G.;
Beckmann, U.; Beltran, J.; Boland, W.; Bourget, P.; Brast, R.; Bresson,
Y.; Burtscher, L.; Castillo, R.; Chelli, A.; Cid, C.; Clausse, J. -M.;
Connot, C.; Conzelmann, R. D.; Danchi, W. -C.; De Haan, M.; Delbo,
M.; Ebert, M.; Elswijk, E.; Fantei, Y.; Frahm, R.; Gámez Rosas, V.;
Gabasch, A.; Gallenne, A.; Garces, E.; Girard, P.; Gonté, F. Y. J.;
González Herrera, J. C.; Graser, U.; Guajardo, P.; Guitton, F.;
Haubois, X.; Hron, J.; Hubin, N.; Huerta, R.; Isbell, J. W.; Ives,
D.; Jakob, G.; Jaskó, A.; Jochum, L.; Klein, R.; Kragt, J.; Kroes,
G.; Kuindersma, S.; Labadie, L.; Laun, W.; Le Poole, R.; Leinert, C.;
Lizon, J. -L.; Lopez, M.; Mérand, A.; Marcotto, A.; Mauclert, N.;
Maurer, T.; Mehrgan, L. H.; Meisner, J.; Meixner, K.; Mellein, M.;
Mohr, L.; Morel, S.; Mosoni, L.; Navarro, R.; Neumann, U.; Nußbaum,
E.; Pallanca, L.; Pasquini, L.; Percheron, I.; Pott, J. -U.; Pozna,
E.; Ridinger, A.; Rigal, F.; Riquelme, M.; Rivinius, Th.; Roelfsema,
R.; Rohloff, R. -R.; Rousseau, S.; Schuhler, N.; Schuil, M.; Soulain,
A.; Stee, P.; Stephan, C.; ter Horst, R.; Tromp, N.; Vakili, F.;
van Duin, A.; Vinther, J.; Wittkowski, M.; Wrhel, F.
Bibcode: 2021A&A...647A..56V
Altcode: 2020arXiv201205697V
Context. A complex environment exists in the inner few astronomical
units of planet-forming disks. High-angular-resolution observations
play a key role in our understanding of the disk structure and the
dynamical processes at work.
Aims: In this study we aim to
characterize the mid-infrared brightness distribution of the inner disk
of the young intermediate-mass star HD 163296 from early VLTI/MATISSE
observations taken in the L- and N-bands. We put special emphasis on
the detection of potential disk asymmetries.
Methods: We use
simple geometric models to fit the interferometric visibilities and
closure phases. Our models include a smoothed ring, a flat disk with
an inner cavity, and a 2D Gaussian. The models can account for disk
inclination and for azimuthal asymmetries as well. We also perform
numerical hydrodynamical simulations of the inner edge of the disk.
Results: Our modeling reveals a significant brightness asymmetry in
the L-band disk emission. The brightness maximum of the asymmetry is
located at the NW part of the disk image, nearly at the position angle
of the semimajor axis. The surface brightness ratio in the azimuthal
variation is 3.5 ± 0.2. Comparing our result on the location of the
asymmetry with other interferometric measurements, we confirm that
the morphology of the r < 0.3 au disk region is time-variable. We
propose that this asymmetric structure, located in or near the inner
rim of the dusty disk, orbits the star. To find the physical origin
of the asymmetry, we tested a hypothesis where a vortex is created
by Rossby wave instability, and we find that a unique large-scale
vortex may be compatible with our data. The half-light radius of
the L-band-emitting region is 0.33 ±0.01 au, the inclination is
52°-7°+5°, and the position angle is 143°
± 3°. Our models predict that a non-negligible fraction of the
L-band disk emission originates inside the dust sublimation radius
for μm-sized grains. Refractory grains or large (≳10 μm-sized)
grains could be the origin of this emission. N-band observations may
also support a lack of small silicate grains in the innermost disk
(r ≲ 0.6 au), in agreement with our findings from L-band data. Based on observations made with ESO Telescopes at the La Silla
Paranal Observatory under program IDs 0103.D-0294 and 0103.D-0153.
Title: The long-period orbit of the dust-producing Wolf-Rayet binary
WR 125
Authors: Daly, A.; Richardson, N.; Chené, A.; Hill, G.; Williams,
P.; Shenavrin, V.; Weigelt, G.
Bibcode: 2021AAS...23713606D
Altcode:
Recently the binary system WR 125, WC7+O, began a dust creation episode
seen with an infrared outburst. This is the first time since 1991 that
this type of activity has been observed for WR 125, leading to the first
determination of a period: 28.1 years. We began collecting spectra
of WR 125 to constrain the orbit, on the assumption that this system
will produce dust near periastron, similarly to WR 140. We present the
infrared light curves showing the similarities between the 1990s dust
event and the current dust event, as well as the first measured radial
velocities for the system to begin constraining the orbit. Based on
data taken with Gemini Observatory and Keck Observatory. This research
was partially supported through Embry-Riddle Aeronautical University's
Faculty Innovative Research in Science and Technology (FIRST) Program
as well as its Undergraduate Research Institute.
Title: WR 140, a Colliding Wind Laboratory: The X-ray History
Authors: Corcoran, M.; Pollock, A.; Hamaguchi, K.; Russell, C.;
Williams, P.; Moffat, A.; Weigelt, G.; Shenavrin, V.; Richardson, N.;
Gendreau, K.; Arzoumanian, Z.; Stevens, I.; Espinoza, D.; Drake, S.;
Gull, T.
Bibcode: 2021AAS...23720406C
Altcode:
WR140 is a long-period, highly eccentric massive colliding
wind binary system with well-determined orbital and stellar
parameters. Periodically-varying X-ray emission is primarily generated
in the hot shocked gas produced by the collision of the winds of the
WC7pd + O5.5fc star components in the space between the two stars. We
have obtained time-resolved broad-band X-ray spectrometry using the
RXTE, Swift and NICER X-ray observatories through 3 orbital cycles,
including two consecutive periastron passages. We discuss the X-ray
variations in the context of the colliding wind model, and we consider
the implications of the X-ray data for our understanding of the
shocked plasma and its relation to the orbital parameters and other
multi-wavelength observations .
Title: Infrared interferometric imaging of the compact dust disk
around the AGB star HR3126 with the bipolar Toby Jug Nebula
Authors: Ohnaka, K.; Schertl, D.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2020A&A...643A.175O
Altcode: 2020arXiv201200768O
Aims: The asymptotic giant branch (AGB) star HR3126, associated
with the arcminute-scale bipolar Toby Jug Nebula, provides a rare
opportunity to study the emergence of bipolar structures at the end of
the AGB phase. Our goal is to image the central region of HR3126 with
high spatial resolution.
Methods: We carried out long-baseline
interferometric observations with AMBER and GRAVITY (2-2.45 μm) at the
Very Large Telescope Interferometer with spectral resolutions of 1500
and 4500, speckle interferometric observations with VLT/NACO (2.24 μm),
and imaging with SPHERE-ZIMPOL (0.55 μm) and VISIR (7.9-19.5 μm).
Results: The images reconstructed in the continuum at 2.1-2.29 μm
from the AMBER+GRAVITY data reveal the central star surrounded by an
elliptical ring-like structure with a semimajor and semiminor axis of
5.3 and 3.5 mas, respectively. The ring is interpreted as the inner rim
of an equatorial dust disk viewed from an inclination angle of ~50°,
and its axis is approximately aligned with the arcminute-scale bipolar
nebula. The disk is surprisingly compact, with an inner radius of a
mere 3.5 R⋆ (2 au). Our 2-D radiative transfer modeling
shows that an optically thick flared disk with silicate grains as large
as ~4 μm can simultaneously reproduce the observed continuum images
and the spectral energy distribution. The images reconstructed in the
CO first overtone bands reveal elongated extended emission around the
central star, suggesting the oblateness of the star's atmosphere or
the presence of a CO gas disk inside the dust cavity. The object is
unresolved with SPHERE-ZIMPOL, NACO, and VISIR.
Conclusions:
If the disk formed together with the bipolar nebula, the grain growth
from sub-micron to a few microns should have taken place over the
nebula's dynamical age of ~3900 yrs. The non-detection of a companion
in the reconstructed images implies that either its 2.2 μm brightness
is more than ~30 times lower than that of the red giant or it might
have been shredded due to binary interaction. Based on AMBER,
GRAVITY, NACO, SPHERE, and VISIR observations made with the Very Large
Telescope and Very Large Telescope Interferometer of the European
Southern Observatory. Program IDs: 096.D-0482, 098.D-0525, 099.D-0493,
and 0102.D-0550. Based on observations with AKARI, a JAXA project
with the participation of ESA. Herschel is an ESA space observatory
with science instruments provided by European-led Principal Investigator
consortia and with important participation from NASA.
Title: Onthe changes in the physical properties of the ionized
region around the Weigelt structures in η Carinae over the 5.54-yr
spectroscopic cycle
Authors: Teodoro, M.; Gull, T. R.; Bautista, M. A.; Hillier, D. J.;
Weigelt, G.; Corcoran, M. F.
Bibcode: 2020MNRAS.495.2754T
Altcode: 2020arXiv200502139T; 2020MNRAS.tmp.1429T
We present HST/STIS observations and analysis of two prominent nebular
structures around the central source of η Carinae, the knots C and
D. The former is brighter than the latter for emission lines from
intermediate- or high-ionization potential ions. The brightness of lines
from intermediate- and high-ionization potential ions significantly
decreases at phases around periastron. We do not see conspicuous
changes in the brightness of lines from low-ionization potential
(<13.6 eV) ions over the orbital period. Line ratios suggest that
the total extinction towards the Weigelt structures is AV
= 2.0. Weigelt C and D are characterized by an electron density of
106.9 cm-3 that does not significantly change
throughout the orbital cycle. The electron temperature varies from
5500 (around periastron) to 7200 K (around apastron). The relative
changes in the brightness of the He I lines are well reproduced by
the variations in the electron temperature alone. We found that, at
phases around periastron, the electron temperature seems to be higher
for Weigelt C than that of D. The Weigelt structures are located close
to the Homunculus equatorial plane, at a distance of about 1240 au
from the central source. From the analysis of proper motion and age,
the Weigelt complex can be associated with the equatorial structure
called 'Butterfly Nebula' surrounding the central binary system.
Title: Imaging the expanding knotty structure in the close environment
of the LBV star $\eta$ Carinae
Authors: Millour, F.; Lagadec, E.; Montargès, M.; Kervella, P.;
Soulain, A.; Vakili, F.; Petrov, R.; Weigelt, G.; Groh, J.; Smith, N.;
Mehner, A.; Schmid, H. M.; Ramos, J.; Moeller-Nillson, O.; Roelfsema,
R.; Rigal, F.
Bibcode: 2020arXiv200615660M
Altcode:
$\eta$~Car is one of the most massive stars in the Galaxy. It underwent
a massive eruption in the 19th century, which produced the impressive
bipolar Homunculus nebula now surrounding it. The central star is an
eccentric binary with a period of 5.54\,years. Although the companion
has not been detected directly, it causes time-variable ionization and
colliding-wind X-ray emission. By characterizing the complex structure
and kinematics of the ejecta close to the star, we aim to constrain past
and present mass loss of $\eta$~Car. $\eta$~Car is observed with the
extreme adaptive optics instrument SPHERE at the Very Large Telescope,
using its polarimetric mode in the optical with the ZIMPOL camera. A
spatial resolution of 20\,mas was achieved, i.e. very close to the
presumed 13 mas apastron separation of the companion star. We detect
new structures within the inner arcsecond to the star (2\,300\,au at
a 2.3\,kpc distance). We can relate these structures to the eruption
near 1890 by tracking their proper motions derived from our new images
and historical images over a 30\,years time span. Besides, we find a
fan-shaped structure in the inner 200~au to the star in the H$\alpha$
line, that could potentially be associated with the wind collision
zone of the two stars.
Title: Brightest Non-Thermal X-ray Emission Observed from Eta Carinae
Authors: Hamaguchi, Kenji; Espinoza-Galeas, David A.; Corcoran,
Michael Francis; Russell, Christopher; Pittard, Julian; Madura,
Thomas; Takahashi, Hiromitsu; Gull, Theodore; Richardson, Noel;
Damineli, Augusto; Hillier, Desmond; Moffat, Anthony; Weigelt, Gerd;
Pollock, Andy
Bibcode: 2020ATel13738....1H
Altcode:
The NuSTAR X-ray observatory pointed at the massive colliding wind
binary system, eta Carinae, for 90 ksec on 2020 April 13-14 (phi_orb =
4.0297) as its thermal X-ray emission was gradually recovering from
its minimum flux in mid February (ATel #13636) near its most recent
periastron passage.
Title: Modeling of Spectroscopic and Interferometric Observations
of the Herbig Star VV Ser with Hybrid Models
Authors: Tambovtseva, L. V.; Kreplin, A.; Grinin, V. P.; Weigelt, G.
Bibcode: 2020ARep...64..336T
Altcode:
Modeling of hydrogen emission lines is a powerful tool to study physical
processes in the nearest vicinity of young stars because spectral
lines carry information on the kinematics and physical conditions of
the gas. One of the lines that probe emitting regions closest to the
star is the Br line. We consider different types of hybrid models to
reproduce both interferometric VLTI-AMBER observations and LBT-LUCIFER
spectroscopic observations of the single-peak profile of the Br line
of the Herbig AeBe star (HAEBE) VV Ser, a member of the UX Ori type
subclass. We computed models of a magneto-centrifugal disk wind,
a magnetospheric accretion region (magnetosphere), Cranmer's polar
wind, and scattered light from circumstellar polar dust. Furthermore,
we calculated hybrid two-component models consisting of a disk wind
and one of the aforementioned models. We computed visibilities and line
profiles for all types of models and compared them with the available
interferometric observations to constrain model parameters. We conclude
that for the inclinations reported for this star (60°-70°), the
disk wind alone cannot explain the Br line profile although it may
be a dominant contributor to the hydrogen line radiation. However,
magneto-centrifugal disk wind in combination with aforementioned
emitting regions (magnetosphere, polar wind, or scattered light from
polar dust) may be able to reproduce the observations.
Title: CO, Water, and Tentative Methanol in η Carinae Approaching
Periastron
Authors: Morris, Patrick W.; Charnley, Steven B.; Corcoran, Michael;
Cordiner, Martin; Damineli, Augusto; Groh, Jose H.; Gull, Theodore R.;
Loinard, Laurent; Madura, Thomas; Mehner, Andrea; Moffat, Anthony;
Palmer, Maureen Y.; Rau, Gioia; Richardson, Noel D.; Weigelt, Gerd
Bibcode: 2020ApJ...892L..23M
Altcode: 2020arXiv200211053M
The complex circumstellar environment around the massive binary and
luminous blue variable η Carinae is known to harbor numerous light
molecules, emitting most strongly in rotational states with upper level
energies to ∼300 K. In circumstellar gas, the complex organic molecule
methanol (CH3OH) has been found almost exclusively around
young stellar objects, and thus regarded as a signpost of recent star
formation. Here we report the first potential detection of methanol
around a highly evolved high-mass star, while using the Atacama Large
Millimeter Array to investigate molecular cloud conditions traced by CO
(2-1) in an orbit phase preceding the 2020 periastron. The methanol
emission originates from hot (Tgas ≃ 700 K) material,
∼2″ (0.02 pc) across, centered on the dust-obscured binary, and is
accompanied by prominent absorption of continuum radiation in a cooler
(Tgas ≃ 110 K) layer of gas. We also report a first
detection of water in Herschel observations at 557 and 988 GHz. The
methanol abundance is several to 50 times higher than observed toward
several lower-mass stars, while water abundances are similar to those
observed in cool, dense molecular clouds. The very high methanol:water
abundance ratio in the core of η Car may suggest methanol formation
processes similar to Fischer-Tropsch-type catalytic reactions on dust
grains. These observations prove that complex molecule formation can
occur in a chemically evolved massive stellar environment, given
sufficient gas densities and shielding conditions as may occur in
material around massive interacting companions and merger remnants.
Title: Eta Carinae's Recovery from the 2020 X-ray Minimum as Seen
by NICER\
Authors: Espinoza-Galeas, David A.; Corcoran, Michael Francis;
Hamaguchi, Kenji; Gull, Theodore; Richardson, Noel; Russell,
Christopher; Damineli, Augusto; Navarete, Felipe; Hillier, Desmond;
Moffat, Anthony; Weigelt, Gerd; Pollock, Andy; Arzoumanian, Zaven;
Gendreau, Keith C.
Bibcode: 2020ATel13636....1E
Altcode:
Eta Carinae (Eta Car) is a super-massive, long-period, eccentric,
unstable Colliding Wind Binary (CWB) system which experiences periodic
X-ray minima near periastron passage.
Title: NICER Observations of the 2020 X-ray Minimum of eta Carinae
Authors: Corcoran, Michael F.; Hamaguchi, Kenji; Espinoza, David;
Gull, Ted; Gendreau, Keith; Arzoumanian, Zaven; Moffat, A. F. J.;
Weigelt, Gerd; Richardson, Noel; Damineli, Augusto; Navarete, Felipe
Bibcode: 2020ATel13516....1C
Altcode:
X-ray emission from the massive colliding wind binary eta Carinae has
been monitored by NASA's Neutron Star Interior Composition Explorer
(NICER) X-ray observatory since 20 July 2017, through the system's
recent X-ray minimum and periastron passage (ATEL #13508).
Title: GRAVITY and the Galactic Centre
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...26G
Altcode:
On a clear night, our home galaxy, the Milky Way, is visible as a
starry ribbon across the sky. Its core is located in the constellation
of Sagittarius, approximately where the bright glow is interrupted
by the darkest dust filaments. There, hidden, lies a massive black
hole. To peer through the obscuring clouds and see the stars and gas
near the black hole we use GRAVITY. The main GRAVITY results are the
detection of gra- vitational redshift, the most precise mass- distance
measurement, the test of the equivalence principle, and the detection
of orbital motion near the black hole.
Title: An Image of the Dust Sublimation Region in the Nucleus of
NGC 1068
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...24G
Altcode:
The superb resolution of the Very Large Telescope Interferometer
(VLTI) and the unrivalled sensitivity of GRAVITY have allowed us to
reconstruct the first detailed image of the dust sublimation region in
an active galaxy. In the nearby archetypal Seyfert 2 galaxy NGC 1068,
the 2 µm continuum emission traces a highly inclined thin ring-like
structure with a radius of 0.24 pc. The observed morphology challenges
the picture of a geometrically and optically thick torus.
Title: 3D time-dependent hydrodynamical and radiative transfer
modeling of Eta Carinae's innermost fossil colliding wind structures
Authors: Madura, Thomas; Gull, T. R.; Clementel, N.; Corcoran,
M.; Damineli, A.; Hamaguchi, K.; Hillier, D. J.; Moffat, A. F. J.;
Richardson, N.; Weigelt, G.
Bibcode: 2019IAUS..346...62M
Altcode:
Eta Carinae is the most massive active binary within 10,000
light-years. While famous for the largest non-terminal stellar
explosion ever recorded, observations reveal a supermassive (∼120
M⊙) binary consisting of an LBV and either a WR or
extreme O star in a very eccentric orbit (e=0.9) with a 5.54-year
period. Dramatic changes across multiple wavelengths are routinely
observed as the stars move about in their highly elliptical orbits,
especially around periastron when the hot (∼40 kK) companion star
delves deep into the denser and much cooler (∼15 kK) extended wind
photosphere of the LBV primary. Many of these changes are due to a
dynamic wind-wind collision region (WWCR) that forms between the stars,
plus expanding radiation-illuminated fossil WWCRs formed one, two,
and three 5.54-year orbital cycles ago. These fossil WWCRs have been
spatially and spectrally resolved by the Hubble Space Telescope/Space
Telescope Imaging Spectrograph (HST/STIS) at multiple epochs, resulting
in data cubes that spatially map Eta Carinae's innermost WWCRs and
follow temporal changes in several forbidden emission lines (e.g. [Fe
uc(iii)] 4659 Å, [Fe uc(ii)] 4815 Å) across the 5.54-year cycle. We
present initial results of 3D time-dependent hydrodynamical and
radiative-transfer simulations of the Eta Carinae binary and its WWCRs
with the goal of producing synthetic data cubes of forbidden emission
lines for comparison to the available HST/STIS observations. Comparison
of the theoretical models to the observations reveals important details
about the binary's orbital motion, photoionization properties, and
recent (5-15year) mass loss history. Such an analysis also provides
a baseline for following future changes in Eta Carinae, essential
for understanding the late-stage evolution of a nearby supernova
progenitor. Our modeling methods can also be adapted to a number of
other colliding wind binary systems (e.g. WR 140) that are scheduled
to be studied with future observatories (e.g. the James Webb Space
Telescope).
Title: Spatially Resolved Accretion-Ejection in Compact Binaries
with GRAVITY
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...29G
Altcode:
The GRAVITY instrument at the Very Large Telescope Interferometer has
led to the first spatially resolved observations of X-ray binaries at
scales comparable to the binary orbit, providing unprecedented spatial
information on their accretion-ejection mechanisms. In particular,
observations of the hypercritical accretor SS433 have revealed a
variety of spatial structures at the heart of this exotic microquasar,
including bipolar outflows, super-Keplerian equatorial outflows and
extended baryonic jets photoionised by collimated ultraviolet radiation.
Title: Variable Warm Dust around the Herbig Ae Star HD 169142:
Birth of a Ring?
Authors: Chen, Lei; Moór, Attila; Kreplin, Alexander; Kóspál,
Ágnes; Ábrahám, Peter; Matter, Alexis; Carmona, Andres; Hofmann,
Karl-Heinz; Schertl, Dieter; Weigelt, Gerd
Bibcode: 2019ApJ...887L..32C
Altcode: 2019arXiv191110253C
The Herbig Ae star HD 169142 is known to have a gaseous disk with
a large inner hole, and also a photometrically variable inner dust
component in the sub-astronomical-unit region. Following up on our
previous analysis, we further studied the temporal evolution of
inner dust around HD 169142, which may provide information on the
evolution from late-stage protoplanetary disks to debris disks. We
used near-infrared interferometric observations obtained with the
Very Large Telescope Interferometer/PIONIER to constrain the dust
distribution at three epochs spanning six years. We also studied
the photometric variability of HD 169142 using our optical-infrared
observations and archival data. Our results indicate that a dust ring
at ∼0.3 au formed some time between 2013 and 2018, and then faded
(but did not completely disappear) by 2019. The short-term variability
resembles that observed in extreme debris disks, and is likely related
to short-lived dust of secondary origin, though variable shadowing from
the inner ring could be an alternative interpretation. If confirmed,
this is the first direct detection of secondary dust production inside
a protoplanetary disk. Based on observations collected at the
European Organisation for Astronomical Research in the Southern
Hemisphere under ESO programs 0101.C-0367 and 60.A-9135.
Title: Hunting Exoplanets with Single-Mode Optical Interferometry
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...47G
Altcode:
The GRAVITY instrument was primarily conceived for imaging and
astrometry of the Galactic centre. However, its sensitivity and
astrometric capabilities have also enabled interferometry to reach
a new domain of astrophysics: exoplanetology. In March 2019, the
GRAVITY collaboration published the first spectrum and astrometry of an
exoplanet obtained by optical interferometry. In this article, we show
how this observation is paving the way to even more exciting discoveries
— finding new planets, and characterising their atmospheres.
Title: Evidence of a discontinuous disk structure around the Herbig
Ae star HD 139614 (Corrigendum)
Authors: Matter, A.; Labadie, L.; Kreplin, A.; Lopez, B.; Wolf, S.;
Weigelt, G.; Ertel, S.; Pott, J. -U.; Danchi, W. C.
Bibcode: 2019A&A...632C...2M
Altcode:
Based on observations collected at the European Southern Observatory,
Chile (ESO IDs: 385.C-0886(A) and 087.C-0811(A)).
Title: Spatially Resolving the Inner Gaseous Disc of the Herbig Star
51 Oph through its CO Ro-vibration Emission
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...40G
Altcode:
Near-infrared interferometry gives us the opportunity to
spatially resolve the circumstellar environment of young stars at
sub-astronomical-unit (au) scales, which a standalone telescope could
not reach. In particular, the sensitivity of GRAVITY on the VLTI allows
us to spatially resolve the CO overtone emission at 2.3 microns. In
this article, we present a new method of using the model of the CO
spectrum to reconstruct the differential phase signal and extract the
geometry and size of the emitting region.
Title: Spatially Resolving the Quasar Broad Emission Line Region
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...20A
Altcode:
The angular resolution of the Very Large Telescope Interferometer
(VLTI) and the excellent sensitivity of GRAVITY have led to the
first detection of spatially resolved kinematics of high velocity
atomic gas near an accreting super- massive black hole, revealing
rotation on sub-parsec scales in the quasar 3C 273 at a distance of
550 Mpc. The observations can be explained as the result of circular
orbits in a thick disc configuration around a 300 million solar mass
black hole. Within an ongoing Large Programme, this capability will
be used to study the kinematics of atomic gas and its relation to hot
dust in a sample of quasars and Seyfert galaxies. We will measure a
new radius-luminosity relation from spatially resolved data and test
the current methods used to measure black hole mass in large surveys.
Title: Multiple Star Systems in the Orion Nebula
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...36G
Altcode:
GRAVITY observations reveal that most massive stars in the
Orion Trapezium cluster live in multiple systems. Our deep,
milliarcsecond-resolution interferometry fills the gap at 1-100
astronomical units (au), which is not accessible to traditional imaging
and spectroscopy, but is crucial to uncovering the mystery of high-mass
star formation.The new observations find a significantly higher
companion fraction than earlier studies of mostly OB associations. The
observed distribution of mass ratios declines steeply with mass and
follows a Salpeter power-law initial mass function. The observations
therefore exclude stellar mergers as the dominant formation mechanism
for massive stars in Orion.
Title: Images at the Highest Angular Resolution with GRAVITY: The
Case of η Carinae
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...31G
Altcode:
The main goal of an interferometer is to probe the physics of
astronomical objects at the highest possible angular resolution. The
most intuitive way of doing this is by reconstructing images from the
interferometric data. GRAVITY at the Very Large Telescope Interferometer
(VLTI) has proven to be a fantastic instrument in this endeavour. In
this article, we describe the reconstruction of the wind-wind collision
cavity of the massive binary η Car with GRAVITY across two spectral
lines: HeI and Brγ.
Title: Probing the Discs of Herbig Ae/Be Stars at Terrestrial Orbits
Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler,
T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.;
Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy,
M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast,
R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti,
A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet,
É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.;
Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit,
W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert,
G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.;
Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.;
Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.;
Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.;
Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.;
Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.;
Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler,
S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.;
Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum,
L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.;
Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki,
M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère,
V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen,
R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.;
Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière,
P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.;
Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro,
J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.;
Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc,
T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto,
A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray,
T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.;
Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer,
S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.;
Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub,
O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.;
Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.;
van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.;
Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann,
F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez,
J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G.
Bibcode: 2019Msngr.178...38G
Altcode:
More than 4000 exoplanets are known to date in systems that differ
greatly from our Solar System. In particular, inner exoplanets tend
to follow orbits around their parent star that are much more compact
than that of Earth. These systems are also extremely diverse, covering
a range of intrinsic properties. Studying the main physi- cal processes
at play in the innermost regions of the protoplanetary discs is crucial
to understanding how these planets form and migrate so close to their
host. With GRAVITY, we focused on the study of near-infrared emission
of a sample of young intermediate- mass stars, the Herbig Ae/Be stars.
Title: Mid-infrared evolution of η Carinae from 1968 to 2018
Authors: Mehner, A.; de Wit, W. -J.; Asmus, D.; Morris, P. W.;
Agliozzo, C.; Barlow, M. J.; Gull, T. R.; Hillier, D. J.; Weigelt, G.
Bibcode: 2019A&A...630L...6M
Altcode: 2019arXiv190809154M
η Car is one of the most luminous and massive stars in our Galaxy
and is the brightest mid-IR source in the sky outside our solar
system. Since the late 1990s, the central source has dramatically
brightened at UV and optical wavelengths. This might be explained by
a decrease in circumstellar dust extinction. We aim to establish the
mid-IR flux evolution and further our understanding of the star's UV
and optical brightening. Mid-IR images from 8-20 μm were obtained
in 2018 with VISIR at the Very Large Telescope. Archival data from
2003 and 2005 were retrieved from the ESO Science Archive Facility,
and historical records were collected from publications. We present
mid-IR images of η Car with the highest angular resolution to date
at the corresponding wavelengths (≥0.22″). We reconstruct the
mid-IR evolution of the spectral energy distribution of the spatially
integrated Homunculus nebula from 1968 to 2018 and find no long-term
changes. The bolometric luminosity of η Car has been stable over
the past five decades. We do not observe a long-term decrease in the
mid-IR flux densities that could be associated with the brightening at
UV and optical wavelengths, but circumstellar dust must be declining
in our line of sight alone. Short-term flux variations within about
25% of the mean levels could be present. Based on observations
collected at ESO's Very Large Telescope under Prog-IDs: 074.A-9016(A),
0101.D-0077(A). Based on observations made with ESO Telescopes at
the La Silla Paranal Observatory under Prog-IDs: 60.A-9126(A,C,E,I),
69.D-0304(B),71.D-0049(A).
Title: Setting the Stage for the Planet Formation Imager
Authors: Monnier, John; Aarnio, Alicia; Absil, Olivier; Alonso-Herrero,
Almudena; Anugu, Narsireddy; Baines, Ellyn; Bayo, Amelia; Berger,
Jean-Philippe; Danchi, William; Elias, Nicholas; Gai, Mario; Gandhi,
Poshak; Gardner, Tyler; Gies, Douglas; Gonzalez, Jean-François;
Haniff, Chris; Hoenig, Sebastian; Ireland, Michael; Isella, Andrea;
Kane, Stephen; Kirchschlager, Florian; Kishimoto, Makoto; Klarmann,
Lucia; Kluska, Jacques; Kraus, Stefan; Labadie, Lucas; Le Bouquin,
Jean-Baptiste; Leisawitz, David; Linz, Hendrik; Mennesson, Bertrand;
Morlok, Andreas; Norris, Ryan; Pope, Benjamin; Quiroga-Nuñez, Luis
Henry; Rau, Gioia; Regaly, Zsolt; Reynolds, Mark; Riva, Alberto;
Roettenbacher, Rachael; Schaefer, Gail; Setterholm, Benjamin; Smith,
Michael; Stencel, Robert; ten Brummelaar, Theo; Tristram, Konrad R. W.;
van Belle, Gerard; Vasisht, Gautam; Weigelt, Gerd; Wittkowski, Markus
Bibcode: 2019BAAS...51g.133M
Altcode: 2019astro2020U.133M
The Planet Formation Imager (PFI) is a next-generation infrared
interferometer designed to image the active phases of planet formation
and to take planetary “snapshots” of young systems. We outline
a technology plan to make PFI a reality, identifying a potential
breakthrough opportunity for making inexpensive large telescopes
available.
Title: Infrared Interferometric Three-dimensional Diagnosis of the
Atmospheric Dynamics of the AGB Star R Dor with VLTI/AMBER
Authors: Ohnaka, Keiichi; Weigelt, Gerd; Hofmann, Karl-Heinz
Bibcode: 2019ApJ...883...89O
Altcode: 2019arXiv190806997O
The mechanism of mass loss in late evolutionary stages of low-
and intermediate-mass stars is not yet well understood. Therefore,
it is crucial to study the dynamics of the region within a few R
⋆, where the wind acceleration is considered to take
place. We present a three-dimensional diagnosis of the atmospheric
dynamics of the closest asymptotic giant branch star R Dor from the low
photospheric layers to the extended outer atmosphere, for the first time
for a star other than the Sun. The images reconstructed with a spatial
resolution of 6.8 mas—seven times finer than the star’s angular
diameter of 51.2 mas in the continuum—using the AMBER instrument at
the Very Large Telescope Interferometer show a large, bright region over
the surface of the star and an extended atmosphere. The velocity-field
maps over the star’s surface and atmosphere obtained from the Mg
and H2O lines near 2.3 μm forming at atmospheric heights
below ∼1.5 R ⋆ show little systematic motion beyond the
measurement uncertainty of 1.7 km s-1. In marked contrast,
the velocity-field map obtained from the CO first overtone lines reveals
systematic outward motion at 7-15 km s-1 in the extended
outer atmosphere at a height of ∼1.8 R ⋆. Given the
detection of dust formation at ∼1.5 R ⋆, the strong
acceleration of material between ∼1.5 and 1.8 R ⋆
may be caused by the radiation pressure on dust grains. However,
we cannot yet exclude the possibility that the outward motion may
be intermittent, caused by ballistic motion due to convection and/or
pulsation. Based on AMBER observations made with the Very Large
Telescope and Very Large Telescope Interferometer of the European
Southern Observatory. Program ID: 092.D-0456(A), 092.D-0465(A/B).
Title: A Realistic Roadmap to Formation Flying Space Interferometry
Authors: Monnier, John; Aarnio, Alicia; Absil, Olivier; Anugu,
Narsireddy; Baines, Ellyn; Bayo, Amelia; Berger, Jean-Philippe;
Cleeves, L. Ilsedore; Dale, Daniel; Danchi, William; de Wit, W. J.;
Defrère, Denis; Domagal-Goldman, Shawn; Elvis, Martin; Froebrich,
Dirk; Gai, Mario; Gandhi, Poshak; Garcia, Paulo; Gardner, Tyler; Gies,
Douglas; Gonzalez, Jean-François; Gunter, Brian; Hoenig, Sebastian;
Ireland, Michael; Jorgensen, Anders M.; Kishimoto, Makoto; Klarmann,
Lucia; Kloppenborg, Brian; Kluska, Jacques; Knight, J. Scott; Kral,
Quentin; Kraus, Stefan; Labadie, Lucas; Lawson, Peter; Le Bouquin,
Jean-Baptiste; Leisawitz, David; Lightsey, E. Glenn; Linz, Hendrik;
Lipscy, Sarah; MacGregor, Meredith; Matsuo, Hiroshi; Mennesson,
Bertrand; Meyer, Michael; Michael, Ernest A.; Millour, Florentin;
Mozurkewich, David; Norris, Ryan; Ollivier, Marc; Packham, Chris;
Petrov, Romain; Pueyo, Laurent; Pope, Benjamin; Quanz, Sascha; Ragland,
Sam; Rau, Gioia; Regaly, Zsolt; Riva, Alberto; Roettenbacher, Rachael;
Savini, Giorgio; Setterholm, Benjamin; Sewilo, Marta; Smith, Michael;
Spencer, Locke; ten Brummelaar, Theo; Turner, Neal; van Belle, Gerard;
Weigelt, Gerd; Wittkowski, Markus
Bibcode: 2019BAAS...51g.153M
Altcode: 2019astro2020U.153M
The ultimate astronomical observatory would be a formation flying
space interferometer, combining sensitivity and stability with high
angular resolution. The smallSat revolution offers a new and maturing
prototyping platform for space interferometry and we put forward a
realistic plan for achieving first stellar fringes in space by 2030.
Title: Eta Carinae: Taking the Plunge
Authors: Corcoran, Michael F.; Damineli, Augusto; Espinoza, David;
Gull, Theodore Raymond; Hamaguchi, Kenji; Hillier, D. John; Madura,
Thomas I.; Moffat, Anthony F. J.; Petre, Robert; Pittard, Julian M.;
Richardson, Noel D.; Russell, Christopher Michael Post; Weigelt, Gerd
Bibcode: 2019hst..prop15992C
Altcode:
Eta Carinae is the nearest superluminous binary system we can easily
study. Over the past 20 years the HETGS has been a key to unlocking
the dynamics of the wind-wind collision and the nature of the hidden
companion star. The AO 21 interval includes the next periastron
passage, offering us a view of the hot gas in the wind-wind bow shock
as it plunges towards the primary. We request Chandra and HST imaging
spectrometry to uniquely probe the wind-wind shock on scales from the
stellar separation to 100s of AU. These observations and our approved
AO20 HETG Eta Car observations (not yet obtained),with new imaging
with VLTI/MATISSE, and previous X-ray spectra from Chandra and other
instruments will provide a detailed view of the colliding wind shock
structure and the nature of the companion. The four HST/STIS orbits are
committed to monitor the FUV spectral changes as the X-ray flux peaks,
then drops through the minimum.
Title: Imaging the Key Stages of Planet Formation
Authors: Monnier, John; Rau, Gioia; Bermudez, Joel Sanchez; Ragland,
Sam; Akeson, Rachel; Duchene, Gaspard; van Belle, Gerard; Norris, Ryan;
Gordon, Kathryn; Defrère, Denis; Kluska, Jacques; Ridgway, Stephen;
Le Bouquin, Jean-Baptiste; Anugu, Narsireddy; Scott, Nicholas; Kane,
Stephen; Richardson, Noel D.; Regaly, Zsolt; Zhu, Zhaohuan; Vasisht,
Gautam; Stassun, Keivan G.; Andrews, Sean; Lacour, Sylvestre; Weigelt,
Gerd; Turner, Neal; Adams, Fred C.; Gies, Douglas; Calvet, Nuria;
Espaillat, Catherine; Millan-Gabet, Rafael; Gardner, Tyler; Packham,
Chris; Gai, Mario; Kral, Quentin; Berger, Jean-Philippe; Linz,
Hendrik; Klarmann, Lucia; Bate, Matthew; Bae, Jaehan; Lopez, Rebeca
Garcia; Garufi, Antonio; Baron, Fabien; Kama, Mihkel; Wilner, David;
Hartmann, Lee; Kishimoto, Makoto; Olofsson, Johan; McClure, Melissa;
Haniff, Chris; Hoenig, Sebastian; Line, Michael; Petrov, Romain G.;
Smith, Michael; ten Brummelaar, Theo; De Furio, Matthew; Koutoulaki,
Maria; Rinehart, Stephen; Leisawitz, David; Danchi, William; Huber,
Daniel; Zhang, Ke; Pope, Benjamin; Ireland, Michael; Kraus, Stefan;
Isella, Andrea; Setterholm, Benjamin; White, Russel
Bibcode: 2019BAAS...51c.498M
Altcode: 2019astro2020T.498M
In this white paper, we explore how higher angular resolution beyond
ALMA and 8m-class telescopes can extend our understanding of the
key stages of planet formation, to resolve accreting circumplanetary
disks themselves, and to watch planets forming in situ for the nearest
star-forming regions.
Title: The Future of Exoplanet Direct Detection
Authors: Monnier, John; Rau, Gioia; Baines, Ellyn K.; Sanchez-Bermudez,
Joel; Elvis, Martin; Ragland, Sam; Akeson, Rachel; van Belle, Gerard;
Norris, Ryan; Gordon, Kathryn; Defrère, Denis; Ridgway, Stephen;
Le Bouquin, Jean-Baptiste; Anugu, Narsireddy; Scott, Nicholas; Kane,
Stephen; Richardson, Noel; Regaly, Zsolt; Zhu, Zhaohuan; Chiavassa,
Andrea; Vasisht, Gautam; Stassun, Keivan G.; Dong, Chuanfei; Absil,
Olivier; Lacour, Sylvestre; Weigelt, Gerd; Gies, Douglas; Adams, Fred
C.; Calvet, Nuria; Quanz, Sascha P.; Espaillat, Catherine; Gardner,
Tyler; Greenbaum, Alexandra; Millan-Gabet, Rafael; Packham, Chris; Gai,
Mario; Kral, Quentin; Berger, Jean-Philippe; Linz, Hendrik; Klarmann,
Lucia; Bae, Jaehan; Lopez Garcia, Rebeca; Alexandre, Gallenne; Baron,
Fabien; Hartmann, Lee; Kishimoto, Makoto; McClure, Melissa; Olofsson,
Johan; Haniff, Chris; Line, Michael; Petrov, Romain G.; Smith, Michael;
Hummel, Christian; ten Brummelaar, Theo; De Furio, Matthew; Rinehart,
Stephen; Leisawitz, David; Danchi, William; Huber, Daniel; Wishnow,
Edward; Mourard, Denis; Pope, Benjamin; Ireland, Michael; Kraus,
Stefan; Setterholm, Benjamin; White, Russel
Bibcode: 2019BAAS...51c.514M
Altcode: 2019astro2020T.514M
Diffraction fundamentally limits our ability to image and characterize
exoplanets. Interferometry offers some advantages in exoplanet detection
and characterization and we explore in this white paper some of the
potential scientific breakthroughs possible.
Title: VizieR Online Data Catalog: The LEECH exoplanet imaging survey
(Stone+, 2018)
Authors: Stone, J. M.; Skemer, A. J.; Hinz, P. M.; Bonavita, M.;
Kratter, K. M.; Maire, A. -L.; Defrere, D.; Bailey, V. P.; Spalding,
E.; Leisenring, J. M.; Desidera, S.; Bonnefoy, M.; Biller, B.;
Woodward, C. E.; Henning, T.; Skrutskie, M. F.; Eisner, J. A.; Crepp,
J. R.; Patience, J.; Weigelt, G.; De Rosa, R. J.; Schlieder, J.;
Brandner, W.; Apai, D.; Su, K.; Ertel, S.; Ward-Duong, K.; Morzinski,
K. M.; Schertl, D.; Hofmann, K. -H.; Close, L. M.; Brems, S. S.;
Fortney, J. J.; Oza, A.; Buenzli, E.; Bass, B.
Bibcode: 2019yCat..51560286S
Altcode:
Our survey was conducted using the LBTI instrument (Hinz et
al. 2016SPIE.9907E..04H) at the LBT on Mt. Graham in southern
Arizona. LBTI is located between the two 8.4 m primary mirrors of
the LBT at the combined bent Gregorian focus. Light from each side
of the telescope is corrected for atmospheric aberrations using the
LBTI AO system (Bailey et al. 2014SPIE.9148E..03B) and delivered
into the instrument via a cryogenic beam combiner where it is then
directed to individual science modules. For LEECH observations, we
used the LMIRcam module of LBTI, which is optimized for work in the
thermal-infrared (3-5 μm; Skrutskie et al. 2010SPIE.7735E..3HS;
Leisenring et al. 2012SPIE.8446E..4FL). LBTI does not include an
instrument derotator, so images always rotate with respect to the
detector pixels as the parallactic angle changes. During the course of
the LEECH survey, LMIRcam provided an 11"x11" field of view, reading
a 1024x1024 subsection of its 5.2 μm cutoff HAWAII-2RG detector (the
full 2048x2048 extent of the array now provides a 20"x20" field of view
with LMIRcam). LMIRcam was designed with a plate scale to accommodate
imaging interferometry at the full resolution of the 23 m LBT (10.7
mas/pixel). However, for LEECH observations, we operated without
overlapping and interfering the beams of the two primary mirrors,
opting to make two images of each source on the detector instead. In
this mode, the L' images from each side were oversampled, providing
added robustness to bad pixels and cosmic rays. (4 data files).
Title: Compact gaseous accretion disk in Keplerian rotation around
MWC 147
Authors: Hone, Edward; Kraus, Stefan; Davies, Claire L.; Kreplin,
Alexander; Monnier, John D.; Baron, Fabien; Millan-Gabet, Rafael;
Hofmann, Karl-Heinz; Schertl, Dieter; Sturmann, Judit; Sturmann,
Laszlo; Ten Brummelaar, Theo; Weigelt, Gerd
Bibcode: 2019A&A...623A..38H
Altcode: 2019arXiv190104394H
Context. The disks around some Herbig Be stars have been observed to
be more compact than the expected dust sublimation radius for such
objects. Highly refractory dust grains and optically thick gas emission
have been proposed as possible explanations for this phenomenon.
Aims: Previously, the "undersized" Herbig Be star MWC 147 was
observed with interferometry, and the results indicated a presence of
a compact gaseous disk based on the measured wavelength-dependence of
near-infrared or mid-infrared visibilities. Our aim is to search for
direct evidence for the presence of hot gas inside of the expected
dust sublimation radius of MWC 147.
Methods: By combining
VLTI/AMBER spectro-interferometry (R = 12 000) with CRIRES spectroscopy
(R = 100 000) we can both spectrally and spatially resolve the Brγ
line-emitting gas around MWC 147. Additionally, using CHARA/CLIMB
enables us to achieve baseline lengths up to 330 m, offering 2 times
higher angular resolution (and a better position angle coverage)
than has previously been achieved with interferometry for MWC 147. To
model the continuum we fit our AMBER and CLIMB measurements with a
geometric model of an inclined Gaussian distribution as well as a ring
model. We fit our high-resolution spectra and spectro-interferometric
data with a kinematic model of a disk in Keplerian rotation.
Results: Our interferometric visibility modelling of MWC 147
indicates the presence of a compact continuum disk with a close
to face-on orientation. We model the continuum with an inclined
Gaussian and a ring with a radius of 0.60 mas (0.39 au), which is well
within the expected dust sublimation radius of 1.52 au. We detect no
significant change in the measured visibilities across the Brγ line,
indicating that the line-emitting gas is located in the same region
as the continuum-emitting disk. Using our differential phase data
we construct photocentre displacement vectors across the Brγ line,
revealing a velocity profile consistent with a rotating disk. We fit our
AMBER spectro-interferometry data with a kinematic model of a disk in
Keplerian rotation, where both the line-emitting and continuum-emitting
components of the disk originate from the same compact region close to
the central star. The presence of line-emitting gas in the same region
as the K-band continuum supports the interpretation that the K-band
continuum traces an optically thick gas disk.
Conclusions:
Our spatially and spectrally resolved observations of MWC 147 reveal
that the K-band continuum and Brγ emission both originate from a
similar region which is 3.9 times more compact than the expected dust
sublimation radius for the star; Brγ is emitted from the accretion
disk or disk wind region and exhibits a rotational velocity profile. We
conclude that we detect the presence of a compact, gaseous accretion
disk in Keplerian rotation around MWC 147. Based on observations
made with ESO Telescopes at the La Silla Paranal Observatory under
programme IDs 082.C-0627, 082.C-0893 and 086.C-0684.
Title: Distinguishing circumstellar from stellar photometric
variability in Eta Carinae
Authors: Damineli, A.; Fernández-Lajús, E.; Almeida, L. A.;
Corcoran, M. F.; Damineli, D. S. C.; Gull, T. R.; Hamaguchi, K.;
Hillier, D. J.; Jablonski, F. J.; Madura, T. I.; Moffat, A. F. J.;
Navarete, F.; Richardson, N. D.; Ruiz, G. F.; Salerno, N. E.; Scalia,
M. C.; Weigelt, G.
Bibcode: 2019MNRAS.484.1325D
Altcode: 2019arXiv190100531D; 2019MNRAS.tmp...89D
The interacting binary Eta Carinae remains one of the most
enigmatic massive stars in our Galaxy despite over four centuries of
observations. In this work, its light curve from the ultraviolet
to the near-infrared is analysed using spatially resolved HST
observations and intense monitoring at the La Plata Observatory,
combined with previously published photometry. We have developed a
method to separate the central stellar object in the ground-based
images using HST photometry and applying it to the more numerous
ground-based data, which supports the hypothesis that the central
source is brightening faster than the almost-constant Homunculus. After
detrending from long-term brightening, the light curve shows periodic
orbital modulation (ΔV ∼ 0.6 mag) attributed to the wind-wind
collision cavity as it sweeps around the primary star and it shows
variable projected area to our line-of-sight. Two quasi-periodic
components with time-scales of 2-3 and 8-10 yr and low amplitude,
ΔV < 0.2 mag, are superimposed on the brightening light curve,
being the only stellar component of variability found, which indicates
minimal stellar instability. Moreover, the light-curve analysis shows
no evidence of `shell ejections' at periastron. We propose that the
long-term brightening of the stellar core is due to the dissipation of
a dusty clump in front of the central star, which works like a natural
coronagraph. Thus, the central stars appear to be more stable than
previously thought since the dominant variability originates from a
changing circumstellar medium. We predict that the brightening phase,
due mainly to dust dissipation, will be completed around 2032 ± 4 yr,
when the star will be brighter than in the 1600s by up to ΔV ∼ 1 mag.
Title: ARGOS at the LBT. Binocular laser guided ground-layer
adaptive optics
Authors: Rabien, S.; Angel, R.; Barl, L.; Beckmann, U.; Busoni, L.;
Belli, S.; Bonaglia, M.; Borelli, J.; Brynnel, J.; Buschkamp, P.;
Cardwell, A.; Contursi, A.; Connot, C.; Davies, R.; Deysenroth, M.;
Durney, O.; Eisenhauer, F.; Elberich, M.; Esposito, S.; Frye, B.;
Gaessler, W.; Gasho, V.; Gemperlein, H.; Genzel, R.; Georgiev, I. Y.;
Green, R.; Hart, M.; Kohlmann, C.; Kulas, M.; Lefebvre, M.; Mazzoni,
T.; Noenickx, J.; Orban de Xivry, G.; Ott, T.; Peter, D.; Puglisi,
A.; Qin, Y.; Quirrenbach, A.; Raab, W.; Rademacher, M.; Rahmer, G.;
Rosensteiner, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Sivitilli,
A.; Steinmetz, M.; Storm, J.; Veillet, C.; Weigelt, G.; Ziegleder, J.
Bibcode: 2019A&A...621A...4R
Altcode: 2018arXiv180609938R; 2018A&A...621A...4R
Having completed its commissioning phase, the Advanced Rayleigh
guided Ground-layer adaptive Optics System (ARGOS) facility is coming
online for scientific observations at the Large Binocular Telescope
(LBT). With six Rayleigh laser guide stars in two constellations and
the corresponding wavefront sensing, ARGOS corrects the ground-layer
distortions for both LBT 8.4 m eyes with their adaptive secondary
mirrors. Under regular observing conditions, this set-up delivers
a point spread function (PSF) size reduction by a factor of 2-3
compared to a seeing-limited operation. With the two LUCI infrared
imaging and multi-object spectroscopy instruments receiving the
corrected images, observations in the near-infrared can be performed
at high spatial and spectral resolution. We discuss the final ARGOS
technical set-up and the adaptive optics performance. We show that
imaging cases with ground-layer adaptive optics (GLAO) are enhancing
several scientific programmes, from cluster colour magnitude diagrams
and Milky Way embedded star formation, to nuclei of nearby galaxies or
extragalactic lensing fields. In the unique combination of ARGOS with
the multi-object near-infrared spectroscopy available in LUCI over a
4 × 4 arcmin field of view, the first scientific observations have
been performed on local and high-z objects. Those high spatial and
spectral resolution observations demonstrate the capabilities now at
hand with ARGOS at the LBT.
Title: Why chromatic imaging matters
Authors: Sanchez-Bermudez, Joel; Millour, Florentin; Baron, Fabien;
van Boekel, Roy; Bourgès, Laurent; Duvert, Gilles; Garcia, Paulo
J. V.; Gomes, Nuno; Hofmann, Karl-Heinz; Henning, Thomas; Isbell,
Jacob W.; Lopez, Bruno; Matter, Alexis; Pott, J. -Uwe; Schertl,
Dieter; Thiébaut, Eric; Weigelt, Gerd; Young, John
Bibcode: 2018ExA....46..457S
Altcode: 2018ExA...tmp...75S; 2018arXiv181206191S
During the last two decades, the first generation of beam combiners at
the Very Large Telescope Interferometer has proved the importance of
optical interferometry for high-angular resolution astrophysical studies
in the near- and mid-infrared. With the advent of 4-beam combiners at
the VLTI, the u - v coverage per pointing increases significantly,
providing an opportunity to use reconstructed images as powerful
scientific tools. Therefore, interferometric imaging is already a key
feature of the new generation of VLTI instruments, as well as for other
interferometric facilities like CHARA and JWST. It is thus imperative
to account for the current image reconstruction capabilities and their
expected evolutions in the coming years. Here, we present a general
overview of the current situation of optical interferometric image
reconstruction with a focus on new wavelength-dependent information,
highlighting its main advantages and limitations. As an Appendix we
include several cookbooks describing the usage and installation of
several state-of-the art image reconstruction packages. To illustrate
the current capabilities of the software available to the community,
we recovered chromatic images, from simulated MATISSE data, using
the MCMC software SQUEEZE. With these images, we aim at showing the
importance of selecting good regularization functions and their impact
on the reconstruction.
Title: The LEECH Exoplanet Imaging Survey: Limits on Planet Occurrence
Rates under Conservative Assumptions
Authors: Stone, Jordan M.; Skemer, Andrew J.; Hinz, Philip M.;
Bonavita, Mariangela; Kratter, Kaitlin M.; Maire, Anne-Lise; Defrere,
Denis; Bailey, Vanessa P.; Spalding, Eckhart; Leisenring, Jarron
M.; Desidera, S.; Bonnefoy, M.; Biller, Beth; Woodward, Charles E.;
Henning, Th.; Skrutskie, Michael F.; Eisner, J. A.; Crepp, Justin R.;
Patience, Jennifer; Weigelt, Gerd; De Rosa, Robert J.; Schlieder,
Joshua; Brandner, Wolfgang; Apai, Dániel; Su, Kate; Ertel, Steve;
Ward-Duong, Kimberly; Morzinski, Katie M.; Schertl, Dieter; Hofmann,
Karl-Heinz; Close, Laird M.; Brems, Stefan S.; Fortney, Jonathan J.;
Oza, Apurva; Buenzli, Esther; Bass, Brandon
Bibcode: 2018AJ....156..286S
Altcode: 2018arXiv181010560S
We present the results of the largest L‧ (3.8 μm) direct
imaging survey for exoplanets to date, the Large Binocular Telescope
Interferometer Exozodi Exoplanet Common Hunt (LEECH). We observed 98
stars with spectral types from B to M. Cool planets emit a larger
share of their flux in L‧ compared to shorter wavelengths,
affording LEECH an advantage in detecting low-mass, old, and
cold-start giant planets. We emphasize proximity over youth in
our target selection, probing physical separations smaller than
other direct imaging surveys. For FGK stars, LEECH outperforms
many previous studies, placing tighter constraints on the hot-start
planet occurrence frequency interior to ∼20 au. For less luminous,
cold-start planets, LEECH provides the best constraints on giant-planet
frequency interior to ∼20 au around FGK stars. Direct imaging survey
results depend sensitively on both the choice of evolutionary model
(e.g., hot- or cold-start) and assumptions (explicit or implicit)
about the shape of the underlying planet distribution, in particular
its radial extent. Artificially low limits on the planet occurrence
frequency can be derived when the shape of the planet distribution
is assumed to extend to very large separations, well beyond typical
protoplanetary dust-disk radii (≲50 au), and when hot-start models
are used exclusively. We place a conservative upper limit on the planet
occurrence frequency using cold-start models and planetary population
distributions that do not extend beyond typical protoplanetary
dust-disk radii. We find that ≲90% of FGK systems can host a 7-10
M Jup planet from 5 to 50 au. This limit leaves open the
possibility that planets in this range are common.
Title: The Life and Times of AMBER: The VLTI's Astronomical Multi-BEam
combineR
Authors: de Wit, W. -J.; Wittkowski, M.; Rantakyrö, F.; Schöller,
M.; Mérand, A.; Petrov, R. G.; Weigelt, G.; Malbet, F.; Massi, F.;
Kraus, S.; Ohnaka, K.; Millour, F.; Lagarde, S.; Haubois, X.; Bourget,
P.; Percheron, I.; Berger, J. -P.; Richichi, A.
Bibcode: 2018Msngr.174....8W
Altcode:
The sharpest images on Paranal are produced by the beam-combining
instruments of the Very Large Telescope Interferometer
(VLTI). Currently, the VLTI is close to completing a transitional
period, moving away from the first generation of instruments (AMBER,
MIDI) and offering new instruments and subsystems to the community. In
this article, we report on the life and achievements of the recently
decommissioned, near-infrared beam combiner instrument AMBER, the most
prolific optical interferometric instrument to date.
Title: GRAVITY chromatic imaging of η Car's core. Milliarcsecond
resolution imaging of the wind-wind collision zone (Brγ, He I)
Authors: GRAVITY Collaboration; Sanchez-Bermudez, J.; Weigelt,
G.; Bestenlehner, J. M.; Kervella, P.; Brandner, W.; Henning, Th.;
Müller, A.; Perrin, G.; Pott, J. -U.; Schöller, M.; van Boekel, R.;
Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Benisty,
M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brast, R.;
Buron, A.; Cantalloube, F.; Caratti O Garatti, A.; Cassaing, F.;
Chapron, F.; Choquet, E.; Clénet, Y.; Collin, C.; Coudé Du Foresto,
V.; de Wit, W.; de Zeeuw, T.; Deen, C.; Delplancke-Ströbele, F.;
Dembet, R.; Derie, F.; Dexter, J.; Duvert, G.; Ebert, M.; Eckart,
A.; Eisenhauer, F.; Esselborn, M.; Fédou, P.; Garcia, P. J. V.;
Garcia Dabo, C. E.; Garcia Lopez, R.; Gao, F.; Gendron, E.; Genzel,
R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Hippler,
S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.;
Jakob, G.; Jochum, L.; Jocou, L.; Karl, M.; Kaufer, A.; Kellner, S.;
Kendrew, S.; Kern, L.; Kiekebusch, M.; Klein, R.; Kolb, J.; Kulas, M.;
Lacour, S.; Lapeyrère, V.; Lazareff, B.; Le Bouquin, J. -B.; Léna,
P.; Lenzen, R.; Lévêque, S.; Lippa, M.; Magnard, Y.; Mehrgan, L.;
Mellein, M.; Mérand, A.; Moreno-Ventas, J.; Moulin, T.; Müller,
E.; Müller, F.; Neumann, U.; Oberti, S.; Ott, T.; Pallanca, L.;
Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.;
Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Duc, T. P.; Plewa, P. M.;
Popovic, D.; Rabien, S.; Ramirez, A.; Ramos, J.; Rau, C.; Riquelme,
M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rosales, A.; Rousset, G.;
Scheithauer, S.; Schuhler, N.; Spyromilio, J.; Straub, O.; Straubmeier,
C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura, N.; Vincent,
F.; Waisberg, I.; Wank, I.; Widmann, F.; Wieprecht, E.; Wiest, M.;
Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yazici, S.;
Ziegler, D.; Zins, G.
Bibcode: 2018A&A...618A.125G
Altcode: 2018arXiv180802141G
Context. η Car is one of the most intriguing luminous blue variables in
the Galaxy. Observations and models of the X-ray, ultraviolet, optical,
and infrared emission suggest a central binary in a highly eccentric
orbit with a 5.54 yr period residing in its core. 2D and 3D radiative
transfer and hydrodynamic simulations predict a primary with a dense and
slow stellar wind that interacts with the faster and lower density wind
of the secondary. The wind-wind collision scenario suggests that the
secondary's wind penetrates the primary's wind creating a low-density
cavity in it, with dense walls where the two winds interact. However,
the morphology of the cavity and its physical properties are not yet
fully constrained.
Aims: We aim to trace the inner ∼5-50
au structure of η Car's wind-wind interaction, as seen through Brγ
and, for the first time, through the He I 2s-2p line.
Methods:
We have used spectro-interferometric observations with the K-band
beam-combiner GRAVITY at the VLTI. The analyses of the data include
(i) parametrical model-fitting to the interferometric observables,
(ii) a CMFGEN model of the source's spectrum, and (iii) interferometric
image reconstruction.
Results: Our geometrical modeling of the
continuum data allows us to estimate its FWHM angular size close to
2 mas and an elongation ratio ɛ = 1.06 ± 0.05 over a PA = 130° ±
20°. Our CMFGEN modeling of the spectrum helped us to confirm that
the role of the secondary should be taken into account to properly
reproduce the observed Brγ and He I lines. Chromatic images across the
Brγ line reveal a southeast arc-like feature, possibly associated to
the hot post-shocked winds flowing along the cavity wall. The images
of the He I 2s-2p line served to constrain the 20 mas (∼50 au)
structure of the line-emitting region. The observed morphology of He
I suggests that the secondary is responsible for the ionized material
that produces the line profile. Both the Brγ and the He I 2s-2p maps
are consistent with previous hydrodynamical models of the colliding
wind scenario. Future dedicated simulations together with an extensive
interferometric campaign are necessary to refine our constraints on
the wind and stellar parameters of the binary, which finally will help
us predict the evolutionary path of η Car.
Title: Parsec-scale jets driven by high-mass young stellar
objects. Connecting the au- and the parsec-scale jet in IRAS
13481-6124
Authors: Fedriani, R.; Caratti o Garatti, A.; Coffey, D.; Garcia Lopez,
R.; Kraus, S.; Weigelt, G.; Stecklum, B.; Ray, T. P.; Walmsley, C. M.
Bibcode: 2018A&A...616A.126F
Altcode: 2018arXiv180511512F
Context. Protostellar jets in high-mass young stellar objects (HMYSOs)
play a key role in the understanding of star formation and provide us
with an excellent tool to study fundamental properties of HMYSOs.
Aims: We aim at studying the physical and kinematic properties
of the near-infrared (NIR) jet of IRAS 13481-6124 from au to parsec
scales.
Methods: Our study includes NIR data from the Very Large
Telescope instruments SINFONI, CRIRES, and ISAAC. Information about
the source and its immediate environment is retrieved with SINFONI. The
technique of spectro-astrometry is performed with CRIRES to study the
jet on au scales. The parsec-scale jet and its kinematic and dynamic
properties are investigated using ISAAC.
Results: The SINFONI
spectra in H and K bands are rich in emission lines that are mainly
associated with ejection and accretion processes. Spectro-astrometry is
applied to the Brγ line, and for the first time, to the Brα line,
revealing their jet origin with milliarcsecond-scale photocentre
displacements (11-15 au). This allows us to constrain the kinematics
of the au-scale jet and to derive its position angle ( 216°). ISAAC
spectroscopy reveals H2 emission along the parsec-scale
jet, which allows us to infer kinematic and dynamic properties of the
NIR parsec-scale jet. The mass-loss rate inferred for the NIR jet is
Ṁejec 10-4 M⊙ yr-1
and the thrust is Ṗ 10-2 M⊙ yr-1
km s-1, which is roughly constant for the formation history
of the young star. A tentative estimate of the ionisation fraction is
derived for the massive jet by comparing the radio and NIR mass-loss
rates. An ionisation fraction ≲8% is obtained, which means that the
bulk of the ejecta is traced by the NIR jet and that the radio jet only
delineates a small portion of it. Based on observations collected
at the European Southern Observatory La Silla, Chile, 087.C-0951(A),
087.C-0951(B), 087.C-0489(C), and 090.C-0371(C).
Title: The installation and ongoing commissioning of the MATISSE
mid-infrared interferometer at the ESO Very Large Telescope
Observatory
Authors: Lopez, B.; Lagarde, S.; Matter, A.; Agocs, T.; Allouche, F.;
Antonelli, P.; Augereau, J. -C.; Bailet, C.; Berio, P.; Bettonvil, F.;
Beckmann, U.; van Boekel, R.; Bresson, Y.; Bristow, P.; Cruzalebes,
P.; Delbo, M.; Dominik, C.; Elswijk, E.; Fantei, Y.; Glindemann, A.;
Heininger, M.; Hofmann, K. -H.; Hogerheijde, M.; Hron, J.; Jaffe,
W.; Kroes, G.; Laun, W.; Lehmitz, M.; Meilland, A.; Meisenheimer,
K.; Millour, F.; Morel, S.; Neumann, U.; Pantin, E.; Petrov, R. G.;
Robbe-Dubois, S.; Schertl, D.; Schoeller, M.; Wolf, S.; Zins, G.;
Henning, T.; Stee, Ph.; Weigelt, G.
Bibcode: 2018SPIE10701E..0ZL
Altcode:
MATISSE is the second-generation mid-infrared spectrograph and imager
for the Very Large Telescope Interferometer (VLTI) at Paranal. This
new interferometric instrument will allow significant advances in
various fundamental research fields: studying the planet-forming
region of disks around young stellar objects, understanding the surface
structures and mass loss phenomena affecting evolved stars, and probing
the environments of black holes in active galactic nuclei. As a first
breakthrough, MATISSE will enlarge the spectral domain of current
optical interferometers by offering the L and M bands in addition to
the N band. This will open a wide wavelength domain, ranging from
2.8 to 13 μm, exploring angular scales as small as 3 mas (L band)
/ 10 mas (N band). As a second breakthrough, MATISSE will allow
mid-infrared imaging - closure-phase aperture-synthesis imaging -
with the four Unit Telescopes (UT) or Auxiliary Telescopes (AT) of the
VLTI. Moreover, MATISSE will offer a spectral resolution range from R
30 to R 5000. Here, we remind the concept, the instrumental design,
and the main features of MATISSE. We also describe the last months
of preparation, the status of the instrument, which was shipped to
Cerro Paranal on the site of the ESO Very Large Telescope in October
2017, and the expected schedule for the opening to the community. The
instrument is currently in its Commissioning phase. A complementary
dedicated article details the Commissioning results, which include
the first performance estimates on sky.
Title: MATISSE: performance in laboratory, results of AIV in Paranal,
and first results on sky
Authors: Robbe-Dubois, S.; Lagarde, S.; Antonelli, P.; Lopez, B.;
Allouche, F.; Bailet, C.; Berio, Ph.; Bresson, Y.; Clausse, J. -M.;
Cruzalèbes, P.; Fantei-Caujolle, Y.; Marcotto, A.; Matter, A.;
Meilland, A.; Millour, F.; Morel, S.; Petrov, R. G.; Rousseau, S.;
Soulain, A.; Zins, G.; Lehmitz, M.; Laun, W.; Adler, T.; Klein, R.;
Maurer, T.; Bettonvil, F.; Eldswick, E.; Beckmann, U.; Heininger,
M.; Bristow, P.; Glindemann, A.; Hubin, N.; Jochum, L.; Rivinus,
Th.; Schoeller, M.; Beltran, J.; Bourget, P.; Gallenne, A.; Guerlet,
Th.; Haubois, X.; Ives, D.; Jakob, G.; Meister, A.; Riquelme, M.;
Schuhler, N.; Stephan, C.; Toledo, P.; Tristam, K.; Woillez, J.;
Neumann, U.; Chelli, A.; Guitton, F.; Meisenheimer, K.; Pichon, B.;
Spang, A.; Varga, J.; Henning, Th.; Jaffe, W.; Pasquini, L.; Stee,
Ph.; Weigelt, G.
Bibcode: 2018SPIE10701E..0HR
Altcode:
MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the
spectro-interferometer for the VLTI of the European Southern Observatory
(ESO), operating in the L-, M- and N- spectral bands, and combining
up to four beams from the unit or the auxiliary telescopes (UTs or
ATs). MATISSE will offer new breakthroughs in the study of circumstellar
environments by allowing the mapping of the material distribution,
the gas and essentially the dust. The instrument consists in a warm
optical system (WOP) accepting four beams from the VLTI and relaying
them after a spectral splitting to cold optical benches (COB) located in
two separate cryostats, one in L-M- band, and one in N-band. The test
plan of the complete instrument has been conducted at the Observatoire
de la Côte d'Azur in order to confirm the compliance of the performance
with the high-level requirements. MATISSE has successfully passed the
Preliminary Acceptance in Europe the 12th September 2017. Following
this result, ESO gave approval for the instrument to be shipped to
Paranal. The Alignment, Integration and Verification phase was conducted
until end of February 2018, at the end of which first observations on
sky have been performed to test the operations with the VLTI and to
obtain first stellar light. The two first runs of the commissioning
followed, respectively in March and in May 2018. It has the goal to
optimize the MATISSE-VLTI communication, the acquisition procedures
and the interface parameters. The observations were performed on
bright L-M- and N- stars, with four ATs located on short baselines
and UTs. The limit magnitudes will be deduced. This paper reports on
the performance of the instrument measured in laboratory (results of
test plan in Nice and AIV in Paranal) in terms of spectral coverage,
dispersion laws and spectral resolutions, and transfer function
analysis: instrumental contrast, visibility accuracy, accuracy of
the differential phase, of the closure-phase and of the differential
visibility. It also provides results of the first tests on sky and
the planning of the on-going commissioning.
Title: Planet formation imager: project update
Authors: Monnier, John D.; Ireland, Michael; Kraus, Stefan;
Alonso-Herrero, Almudena; Bonsor, Amy; Baron, Fabien; Bayo, Amelia;
Berger, Jean-Philippe; Boyajian, Tabetha; Chiavassa, Andrea; Ciardi,
David; Creech-Eakman, Michelle; de Wit, Willem-Jan; Defrère, Denis;
Dong, Ruobing; Duchêne, Gaspard; Espaillat, Catherine; Gallenne,
Alexandre; Gandhi, Poshak; Gonzalez, Jean-Francois; Haniff, Chris;
Hoenig, Sebastian; Ilee, John; Isella, Andrea; Jensen, Eric; Juhasz,
Attila; Kane, Stephen; Kishimoto, Makoto; Kley, Wilhelm; Kral, Quentin;
Kratter, Kaitlin; Labadie, Lucas; Lacour, Sylvestre; Laughlin, Greg; Le
Bouquin, Jean-Baptiste; Michael, Ernest; Meru, Farzana; Millan-Gabet,
Rafael; Millour, Florentin; Minardi, Stefano; Morbidelli, Alessandro;
Mordasini, Chris; Morlok, Andreas; Mozurkewich, Dave; Nelson,
Richard; Olofsson, Johan; Oudmaijer, Rene; Packham, Chris; Paladini,
Claudia; Panic, Olja; Petrov, Romain; Pope, Benjamin; Pott, Joerg-Uwe;
Quiroga-Nunez, Luis Henry; Ramos Almeida, Cristina; Raymond, Sean N.;
Regaly, Zsolt; Reynolds, Mark; Ridgway, Stephen; Rinehart, Stephen;
Schreiber, Matthias; Smith, Michael; Stassun, Keivan; Surdej, Jean;
ten Brummelaar, Theo; Tristram, Konrad; Turner, Neal; Tuthill, Peter;
van Belle, Gerard; Vasisht, Gautum; Wallace, Alexander; Weigelt,
Gerd; Wishnow, Edward; Wittkowski, Markus; Wolf, Sebastian; Young,
John; Zhao, Ming; Zhu, Zhaohuan; Zúñiga-Fernández, Sebastian
Bibcode: 2018SPIE10701E..18M
Altcode: 2018arXiv180711555M
The Planet Formation Imager (PFI) is a near- and mid-infrared
interferometer project with the driving science goal of imaging directly
the key stages of planet formation, including the young proto-planets
themselves. Here, we will present an update on the work of the Science
Working Group (SWG), including new simulations of dust structures during
the assembly phase of planet formation and quantitative detection
efficiencies for accreting and non-accreting young exoplanets as
a function of mass and age. We use these results to motivate two
reference PFI designs consisting of a) twelve 3m telescopes with a
maximum baseline of 1.2km focused on young exoplanet imaging and b)
twelve 8m telescopes optimized for a wider range of young exoplanets
and protoplanetary disk imaging out to the 150K H2O ice
line. Armed with 4 x 8m telescopes, the ESO/VLTI can already detect
young exoplanets in principle and projects such as MATISSE, Hi-5 and
Heimdallr are important PFI pathfinders to make this possible. We also
discuss the state of technology development needed to make PFI more
affordable, including progress towards new designs for inexpensive,
small field-of-view, large aperture telescopes and prospects for
Cubesat-based space interferometry.
Title: On the Brγ line emission of the Herbig Ae/Be star MWC 120
Authors: Kreplin, Alexander; Tambovtseva, Larisa; Grinin, Vladimir;
Kraus, Stefan; Weigelt, Gerd; Wang, Yang
Bibcode: 2018MNRAS.476.4520K
Altcode:
The origin of the Br γ line in Herbig Ae/Be stars is still an open
question. It has been proposed that a fraction of the 2.166-μm Br γ
emission might emerge from a disc wind, the magnetosphere and other
regions. Investigations of the Br γ line in young stellar objects
are important to improve our understanding of the accretion-ejection
process. Near-infrared long-baseline interferometry enables the
investigation of the Br γ line-emitting region with high spatial and
high spectral resolution. We observed the Herbig Ae/Be star MWC 120
with the Astronomical Multi-Beam Recombiner (AMBER) on the Very Large
Telescope Interferometer (VLTI) in different spectral channels across
the Br γ line with a spectral resolution of R ∼ 1500. Comparison
of the visibilities, differential and closure phases in the continuum
and the line-emitting region with geometric and radiative transfer
disc-wind models leads to constraints on the origin and dynamics of the
gas emitting the Br γ light. Geometric modelling of the visibilities
reveals a line-emission region about two times smaller than the K-band
continuum region, which indicates a scenario where the Br γ emission is
dominated by an extended disc wind rather than by a much more compact
magnetospheric origin. To compare our data with a physical model,
we applied a state-of-the-art radiative transfer disc-wind model. We
find that all measured visibilities, differential and closure phases
of MWC 120 can be approximately reproduced by a disc-wind model. A
comparison with other Herbig stars indicates a correlation of the
modelled inner disc-wind radii with the corresponding Alfvén radii
for late spectral type stars.
Title: Weak Magnetic Fields in Two Herbig Ae Systems: The SB2 AK
Sco and the Presumed Binary HD 95881
Authors: Järvinen, S. P.; Carroll, T. A.; Hubrig, S.; Ilyin, I.;
Schöller, M.; Castelli, F.; Hummel, C. A.; Petr-Gotzens, M. G.;
Korhonen, H.; Weigelt, G.; Pogodin, M. A.; Drake, N. A.
Bibcode: 2018ApJ...858L..18J
Altcode: 2018arXiv180504701J
We report the detection of weak mean longitudinal magnetic fields
in the Herbig Ae double-lined spectroscopic binary AK Sco and in the
presumed spectroscopic Herbig Ae binary HD 95881 using observations
with the High Accuracy Radial velocity Planet Searcher polarimeter
(HARPSpol) attached to the European Southern Observatory’s
(ESO’s) 3.6 m telescope. Employing a multi-line singular value
decomposition method, we detect a mean longitudinal magnetic
field < {B}{{z}}> =-83+/- 31 G in the secondary
component of AK Sco on one occasion. For HD 95881, we measure <
{B}{{z}}> =-93+/- 25 G and < {B}{{z}}>
=105+/- 29 G at two different observing epochs. For all the detections
the false alarm probability is smaller than 10-5. For AK
Sco system, we discover that accretion diagnostic Na I doublet lines
and photospheric lines show intensity variations over the observing
nights. The double-lined spectral appearance of HD 95881 is presented
here for the first time.
Title: BRITE-Constellation reveals evidence for pulsations in the
enigmatic binary η Carinae
Authors: Richardson, Noel D.; Pablo, Herbert; Sterken, Christiaan;
Pigulski, Andrzej; Koenigsberger, Gloria; Moffat, Anthony F. J.;
Madura, Thomas I.; Hamaguchi, Kenji; Corcoran, Michael F.; Damineli,
Augusto; Gull, Theodore R.; Hillier, D. John; Weigelt, Gerd; Handler,
Gerald; Popowicz, Adam; Wade, Gregg A.; Weiss, Werner W.; Zwintz,
Konstanze
Bibcode: 2018MNRAS.475.5417R
Altcode: 2018arXiv180105445R; 2018MNRAS.tmp..153R
η Car is a massive, eccentric binary with a rich observational
history. We obtained the first high-cadence, high-precision light
curves with the BRITE-Constellation nanosatellites over 6 months in
2016 and 6 months in 2017. The light curve is contaminated by several
sources including the Homunculus nebula and neighbouring stars,
including the eclipsing binary CPD -59°2628. However, we found
two coherent oscillations in the light curve. These may represent
pulsations that are not yet understood but we postulate that they are
related to tidally excited oscillations of η Car's primary star, and
would be similar to those detected in lower mass eccentric binaries. In
particular, one frequency was previously detected by van Genderen et
al. and Sterken et al. through the time period of 1974-1995 through
timing measurements of photometric maxima. Thus, this frequency seems
to have been detected for nearly four decades, indicating that it has
been stable in frequency over this time span. These pulsations could
help provide the first direct constraints on the fundamental parameters
of the primary star if confirmed and refined with future observations.
Title: Embedded AGN and star formation in the central 80 pc of IC 3639
Authors: Fernández-Ontiveros, J. A.; Tristram, K. R. W.; Hönig,
S.; Gandhi, P.; Weigelt, G.
Bibcode: 2018A&A...611A..46F
Altcode: 2017arXiv171101268F
Aims: Our goal is to probe the inner structure and the nature of
the mid-IR emission in the active galaxy IC 3639, which hosts a Seyfert
2 nucleus and shows signatures of strong star-forming activity.
Methods: We used interferometric observations in the N-band with
VLTI/MIDI to resolve the mid-IR emission of this nucleus. The origin of
the nuclear infrared emission is determined from: (1) the comparison
of the correlated fluxes from VLTI/MIDI with the fluxes measured at
subarcsecond resolution (VLT/VISIR, VLT/ISAAC); (2) diagnostics based
on IR fine-structure line ratios, the IR continuum emission, IR bands
produced by polycyclic aromatic hydrocarbons (PAH) and silicates; and
(3) the high-angular resolution spectral energy distribution.
Results: A large fraction of the total mid-IR emission of IC 3639 is
produced in the innermost ≲80 pc with only 1% of the total luminosity
released in the UV/optical range. The unresolved flux of IC 3639 is
90 ± 20 mJy at 10.5 μm, measured with three different baselines
in VLTI (UT1-UT2, UT3-UT4, and UT2-UT3; 46-58 m), making this the
faintest measurement so far achieved with mid-IR interferometry. The
correlated flux is a factor of 3-4 times fainter than the VLT/VISIR
total flux measurement. The observations suggest that most of the
mid-IR emission has its origin on spatial scales between 10 and 80 pc
(40-340 mas). The emission confined within the inner 80 pc is either
dominated by a starburst component or by the AGN core. The brightness
distribution could be reproduced by a single component associated
with the AGN, although this scenario would imply a very extended dust
distribution when compared to other nearby Seyfert galaxies detected
with MIDI. The extended component could also be associated with polar
dust emission, that is, with a dusty wind blown by the AGN. However,
a mixed contribution dominated by the star formation component over the
AGN is favoured by the diagnostics based on ratios of IR fine-structure
emission lines, the shape of the IR continuum, and the PAH and silicate
bands.
Conclusions: A composite AGN-starburst scenario is able
to explain both the mid-IR brightness distribution and the IR spectral
properties observed in the nucleus of IC 3639. The nuclear starburst
would dominate the mid-IR emission and the ionisation of low-excitation
lines (e.g. [Ne II]12.8 μm) with a net contribution
of 70%. The AGN accounts for the remaining 30% of the mid-IR flux,
ascribed to the unresolved component in the MIDI observations, and the
ionisation of high-excitation lines (e.g. [Ne V]14.3 μm
and [O IV]25.9 μm). Based on observations collected
at the European Southern Observatory, Chile, programmes 070.B-0393,
088.D-0005 and 088.B-0809.
Title: A study of dust properties in the inner sub-au region of the
Herbig Ae star HD 169142 with VLTI/PIONIER
Authors: Chen, L.; Kóspál, Á.; Ábrahám, P.; Kreplin, A.; Matter,
A.; Weigelt, G.
Bibcode: 2018A&A...609A..45C
Altcode: 2017arXiv170906514C
Context. An essential step to understanding protoplanetary evolution
is the study of disks that contain gaps or inner holes. The
pre-transitional disk around the Herbig star HD 169142 exhibits
multi-gap disk structure, differentiated gas and dust distribution,
planet candidates, and near-infrared fading in the past decades, which
make it a valuable target for a case study of disk evolution.
Aims: Using near-infrared interferometric observations with
VLTI/PIONIER, we aim to study the dust properties in the inner sub-au
region of the disk in the years 2011-2013, when the object is already
in its near-infrared faint state.
Methods: We first performed
simple geometric modeling to characterize the size and shape of the
NIR-emitting region. We then performed Monte-Carlo radiative transfer
simulations on grids of models and compared the model predictions
with the interferometric and photometric observations.
Results:
We find that the observations are consistent with optically thin gray
dust lying at Rin ~ 0.07 au, passively heated to T ~ 1500
K. Models with sub-micron optically thin dust are excluded because such
dust will be heated to much higher temperatures at similar distance. The
observations can also be reproduced with a model consisting of optically
thick dust at Rin ~ 0.06 au, but this model is plausible
only if refractory dust species enduring ~ 2400 K exist in the inner
disk. Based on observations collected at the European Organisation
for Astronomical Research in the Southern Hemisphere under ESO programs
190.C-963 and 087.C-0709.
Title: VLTI Imaging of a High-Mass Protobinary System: Unveiling
the Dynamical Processes in High-Mass Star Formation
Authors: Kraus, S.; Kluska, J.; Kreplin, A.; Bate, M.; Harries,
T.; Hofmann, K. -H.; Hone, E.; Monnier, J.; Weigelt, G.; Anugu, N.;
de Wit, W. -J. .; Wittkowski, M.
Bibcode: 2017Msngr.170...45K
Altcode:
High-mass stars exhibit a significantly higher multiplicity
frequency than low-mass stars, likely reflecting differences
in how they formed. Theory suggests that high-mass binaries
may form by the fragmentation of self-gravitational discs or by
alternative scenarios such as disc-assisted capture. Near-infrared
interferometric observations reveal the high-mass young stellar object
IRAS 17216-3801 to be a close high-mass protobinary with a separation of
0.058 arcseconds ( 170 au). This is the closest high-mass protobinary
system imaged to date. We also resolve near- infrared excess emission
around the individual stars, which is associated with hot dust in
circumstellar discs. These discs are strongly misaligned with respect
to the binary separation vector, indicating that tidal forces have not
yet had time to realign. We measure a higher accretion rate towards
the circumsecondary disc, confirming a hydrodynamic effect where the
secondary star disrupts the primary star’s accretion stream and
effectively limits the mass that the primary star can accrete. NACO
L'-band imaging may also have resolved the circumbinary disc that
feeds the accretion onto the circumstellar discs. This discovery
demonstrates the unique capabilities of the VLTI, creating exciting
new opportunities to study the dynamical processes that govern the
architecture of close multiple systems.
Title: 4-D Imaging and Modeling of Eta Carinae's Inner Fossil Wind
Structures
Authors: Madura, Thomas I.; Gull, Theodore; Teodoro, Mairan; Clementel,
Nicola; Corcoran, Michael; Damineli, Augusto; Groh, Jose; Hamaguchi,
Kenji; Hillier, D. John; Moffat, Anthony; Richardson, Noel; Weigelt,
Gerd; Lindler, Don; Feggans, Keith
Bibcode: 2017IAUS..329..420M
Altcode:
Eta Carinae is the most massive active binary within 10,000
light-years and is famous for the largest non-terminal stellar
explosion ever recorded. Observations reveal that the supermassive
(~120 M⊙) binary, consisting of an LBV and either a
WR or extreme O star, undergoes dramatic changes every 5.54 years
due to the stars' very eccentric orbits (e ~ 0.9). Many of these
changes are caused by a dynamic wind-wind collision region (WWCR)
between the stars, plus expanding fossil WWCRs formed one, two, and
three 5.54-year cycles ago. The fossil WWCRs can be spatially and
spectrally resolved by the Hubble Space Telescope/Space Telescope
Imaging Spectrograph (HST/STIS). Starting in June 2009, we used the
HST/STIS to spatially map Eta Carinae's fossil WWCRs across one full
orbit, following temporal changes in several forbidden emission lines
(e.g. [Feiii] 4659 Å, [Feii] 4815 Å), creating detailed data cubes
at multiple epochs. Multiple wind structures were imaged, revealing
details about the binary's orbital motion, photoionization properties,
and recent (~5 - 15 year) mass-loss history. These observations allow
us to test 3-D hydrodynamical and radiative-transfer models of the
interacting winds. Our observations and models strongly suggest that
the wind and photoionization properties of Eta Carinae's binary have
not changed substantially over the past several orbital cycles. They
also provide a baseline for following future changes in Eta Carinae,
essential for understanding the late-stage evolution of this nearby
supernova progenitor. For more details, see Gull et al. (2016) and
references therein.
Title: The wind-wind collision hole in eta Car
Authors: Damineli, A.; Teodoro, M.; Richardson, N. D.; Gull, T. R.;
Corcoran, M. F.; Hamaguchi, K.; Groh, J. H.; Weigelt, G.; Hillier,
D. J.; Russell, C.; Moffat, A.; Pollard, K. R.; Madura, T. I.
Bibcode: 2017IAUS..329..186D
Altcode:
Eta Carinae is one of the most massive observable binaries. Yet
determination of its orbital and physical parameters is hampered by
obscuring winds. However the effects of the strong, colliding winds
changes with phase due to the high orbital eccentricity. We wanted
to improve measures of the orbital parameters and to determine the
mechanisms that produce the relatively brief, phase-locked minimum
as detected throughout the electromagnetic spectrum. We conducted
intense monitoring of the He ii λ4686 line in η Carinae for 10
months in the year 2014, gathering ~300 high S/N spectra with ground-
and space-based telescopes. We also used published spectra at the
FOS4 SE polar region of the Homunculus, which views the minimum from
a different direction. We used a model in which the He ii λ4686
emission is produced by two mechanisms: a) one linked to the intensity
of the wind-wind collision which occurs along the whole orbit and
is proportional to the inverse square of the separation between the
companion stars; and b) the other produced by the `bore hole' effect
which occurs at phases across the periastron passage. The opacity
(computed from 3D SPH simulations) as convolved with the emission
reproduces the behavior of equivalent widths both for direct and
reflected light. Our main results are: a) a demonstration that the
He ii λ4686 light curve is exquisitely repeatable from cycle to
cycle, contrary to previous claims for large changes; b) an accurate
determination of the longitude of periastron, indicating that the
secondary star is `behind' the primary at periastron, a dispute extended
over the past decade; c) a determination of the time of periastron
passage, at ~4 days after the onset of the deep light curve minimum;
and d) show that the minimum is simultaneous for observers at different
lines of sight, indicating that it is not caused by an eclipse of the
secondary star, but rather by the immersion of the wind-wind collision
interior to the inner wind of the primary.
Title: Gas dynamics in the inner few AU around the Herbig B[e]
star MWC297. Indications of a disk wind from kinematic modeling and
velocity-resolved interferometric imaging
Authors: Hone, Edward; Kraus, Stefan; Kreplin, Alexander; Hofmann,
Karl-Heinz; Weigelt, Gerd; Harries, Tim; Kluska, Jacques
Bibcode: 2017A&A...607A..17H
Altcode: 2017arXiv170908467H
Aims: Circumstellar accretion disks and outflows play
an important role in star formation. By studying the continuum
and Brγ-emitting region of the Herbig B[e] star MWC297 with
high-spectral and high-spatial resolution we aim to gain insight into
the wind-launching mechanisms in young stars.
Methods: We present
near-infrared AMBER (R = 12 000) and CRIRES (R = 100 000) observations
of the Herbig B[e] star MWC297 in the hydrogen Brγ-line. Using the
VLTI unit telescopes, we obtained a uv-coverage suitable for aperture
synthesis imaging. We interpret our velocity-resolved images as well
as the derived two-dimensional photocenter displacement vectors,
and fit kinematic models to our visibility and phase data in order
to constrain the gas velocity field on sub-AU scales.
Results:
The measured continuum visibilities constrain the orientation of the
near-infrared-emitting dust disk, where we determine that the disk
major axis is oriented along a position angle of 99.6 ± 4.8°. The
near-infrared continuum emission is 3.6 × more compact than the
expected dust-sublimation radius, possibly indicating the presence
of highly refractory dust grains or optically thick gas emission in
the inner disk. Our velocity-resolved channel maps and moment maps
reveal the motion of the Brγ-emitting gas in six velocity channels,
marking the first time that kinematic effects in the sub-AU inner
regions of a protoplanetary disk could be directly imaged. We find a
rotation-dominated velocity field, where the blue- and red-shifted
emissions are displaced along a position angle of 24° ± 3° and
the approaching part of the disk is offset west of the star. The
visibility drop in the line as well as the strong non-zero phase
signals can be modeled reasonably well assuming a Keplerian velocity
field, although this model is not able to explain the 3σ difference
that we measure between the position angle of the line photocenters
and the position angle of the dust disk. We find that the fit can be
improved by adding an outflowing component to the velocity field,
as inspired by a magneto-centrifugal disk-wind scenario.
Conclusions: This study combines spectroscopy, spectroastrometry, and
high-spectral dispersion interferometric, providing yet the tightest
constraints on the distribution and kinematics of Brγ-emitting gas in
the inner few AU around a young star. All observables can be modeled
assuming a disk wind scenario. Our simulations show that adding a
poloidal velocity component causes the perceived system axis to shift,
offering a powerful new diagnostic for detecting non-Keplerian velocity
components in other systems. Based on observations made with ESO
Telescopes at the La Silla Paranal Observatory under programme IDs
081.D-0230, 083.C-0590, 089.C-0959, and 089.C-0563.
Title: Vigorous atmospheric motion in the red supergiant star Antares
Authors: Ohnaka, K.; Weigelt, G.; Hofmann, K. -H.
Bibcode: 2017Natur.548..310O
Altcode: 2017arXiv170806372O
Red supergiant stars represent a late stage of the evolution of
stars more massive than about nine solar masses, in which they
develop complex, multi-component atmospheres. Bright spots have been
detected in the atmosphere of red supergiants using interferometric
imaging. Above the photosphere of a red supergiant, the molecular
outer atmosphere extends up to about two stellar radii. Furthermore,
the hot chromosphere (5,000 to 8,000 kelvin) and cool gas (less than
3,500 kelvin) of a red supergiant coexist at about three stellar
radii. The dynamics of such complex atmospheres has been probed by
ultraviolet and optical spectroscopy. The most direct approach,
however, is to measure the velocity of gas at each position over
the image of stars as in observations of the Sun. Here we report the
mapping of the velocity field over the surface and atmosphere of the
nearby red supergiant Antares. The two-dimensional velocity field
map obtained from our near-infrared spectro-interferometric imaging
reveals vigorous upwelling and downdrafting motions of several huge
gas clumps at velocities ranging from about -20 to +20 kilometres
per second in the atmosphere, which extends out to about 1.7 stellar
radii. Convection alone cannot explain the observed turbulent motions
and atmospheric extension, suggesting that an unidentified process is
operating in the extended atmosphere.
Title: Numerical simulations and infrared spectro-interferometry
reveal the wind collision region in γ2 Velorum
Authors: Lamberts, A.; Millour, F.; Liermann, A.; Dessart, L.; Driebe,
T.; Duvert, G.; Finsterle, W.; Girault, V.; Massi, F.; Petrov, R. G.;
Schmutz, W.; Weigelt, G.; Chesneau, O.
Bibcode: 2017MNRAS.468.2655L
Altcode: 2017arXiv170101124L
Colliding stellar winds in massive binary systems have been studied
through their radio, optical lines and strong X-ray emission
for decades. More recently, near-infrared spectro-interferometric
observations have become available in a few systems, but isolating the
contribution from the individual stars and the wind collision region
still remains a challenge. In this paper, we study the colliding
wind binary γ2 Velorum and aim at identifying the wind
collision zone from infrared interferometric data, which provide unique
spatial information to determine the wind properties. Our analysis is
based on multi-epoch Very Large Telescope Interferometer/Astronomical
Multi-BEam Recombiner (VLTI/AMBER) data that allows us to separate
the spectral components of both stars. First, we determine the
astrometric solution of the binary and confirm previous distance
measurements. We then analyse the spectra of the individual stars,
showing that the O star spectrum is peculiar within its class. Then,
we perform three-dimensional hydrodynamic simulations of the system
from which we extract model images, visibility curves and closure phases
that can be directly compared with the observed data. The hydrodynamic
simulations reveal the 3D spiral structure of the wind collision region,
which results in phase-dependent emission maps. Our model visibility
curves and closure phases provide a good match when the wind collision
region accounts for 3-10 per cent γ2 Vel's total flux
in the near-infrared. The dialogue between hydrodynamic simulations,
radiative transfer models and observations allows us to fully exploit
the observations. Similar efforts will be crucial to study circumstellar
environments with the new generation of VLTI instruments like GRAVITY
and MATISSE.
Title: Aperture synthesis imaging of the carbon AGB star R
Sculptoris. Detection of a complex structure and a dominating spot
on the stellar disk
Authors: Wittkowski, M.; Hofmann, K. -H.; Höfner, S.; Le Bouquin,
J. B.; Nowotny, W.; Paladini, C.; Young, J.; Berger, J. -P.; Brunner,
M.; de Gregorio-Monsalvo, I.; Eriksson, K.; Hron, J.; Humphreys,
E. M. L.; Lindqvist, M.; Maercker, M.; Mohamed, S.; Olofsson, H.;
Ramstedt, S.; Weigelt, G.
Bibcode: 2017A&A...601A...3W
Altcode: 2017arXiv170202574W
Aims: We present near-infrared interferometry of the carbon-rich
asymptotic giant branch (AGB) star R Sculptoris (R Scl).
Methods:
We employ medium spectral resolution K-band interferometry obtained with
the instrument AMBER at the Very Large Telescope Interferometer (VLTI)
and H-band low spectral resolution interferometric imaging observations
obtained with the VLTI instrument PIONIER. We compare our data to a
recent grid of dynamic atmosphere and wind models. We compare derived
fundamental parameters to stellar evolution models.
Results:
The visibility data indicate a broadly circular resolved stellar disk
with a complex substructure. The observed AMBER squared visibility
values show drops at the positions of CO and CN bands, indicating that
these lines form in extended layers above the photosphere. The AMBER
visibility values are best fit by a model without a wind. The PIONIER
data are consistent with the same model. We obtain a Rosseland angular
diameter of 8.9 ± 0.3 mas, corresponding to a Rosseland radius of 355
± 55 R⊙, an effective temperature of 2640 ± 80 K, and a
luminosity of log L/L⊙ = 3.74 ± 0.18. These parameters
match evolutionary tracks of initial mass 1.5 ± 0.5 M⊙
and current mass 1.3 ± 0.7 M⊙. The reconstructed PIONIER
images exhibit a complex structure within the stellar disk including
a dominant bright spot located at the western part of the stellar
disk. The spot has an H-band peak intensity of 40% to 60% above the
average intensity of the limb-darkening-corrected stellar disk. The
contrast between the minimum and maximum intensity on the stellar
disk is about 1:2.5.
Conclusions: Our observations are broadly
consistent with predictions by dynamic atmosphere and wind models,
although models with wind appear to have a circumstellar envelope
that is too extended compared to our observations. The detected
complex structure within the stellar disk is most likely caused by
giant convection cells, resulting in large-scale shock fronts, and
their effects on clumpy molecule and dust formation seen against
the photosphere at distances of 2-3 stellar radii. Based on
observations made with the VLT Interferometry (VLTI) at Paranal
Observatory under programme IDs 090.D-0136, 093.D-0015, 096.D-0720.
Title: Accretion Disks, Magnetospheres, and Disk Winds as Emitters
of the Hydrogen Lines in Herbig Ae/Be Stars
Authors: Tambovtseva, L. V.; Grinin, V. P.; Weigelt, G.; Schertl,
D.; Hofmann, K. -H.; Caratti o Garatti, A.; Garcia Lopez, R.
Bibcode: 2017ASPC..508...67T
Altcode:
Various disk and outflow components of the circumstellar environment
of young Herbig Ae/Be stars may contribute to the hydrogen line
emission. These are a magnetosphere, a disk wind, and a gaseous
accretion disk. Non-LTE modeling was performed to show the influence of
the model parameters on the intensity and the line profiles for each
emitting region to present the spatial distribution of the brightness
for each component and to compare their contributions to the total
line emission. The modeling shows that the disk wind is the dominant
contributor to the Brγ and Hα lines rather than the magnetospheric
accretion and gaseous accretion disk.
Title: TYC 8241 2652 1 and the case of the disappearing disk: No
smoking gun yet
Authors: Günther, Hans Moritz; Kraus, Stefan; Melis, Carl; Curé,
Michel; Harries, Tim; Ireland, Michael; Kanaan, Samer; Poppenhaeger,
Katja; Rizzuto, Aaron; Rodriguez, David; Schneider, Christian P.;
Sitko, Michael; Weigelt, Gerd; Willson, Matthew; Wolk, Scott
Bibcode: 2017A&A...598A..82G
Altcode: 2016arXiv161101371G
Context. TYC8241 2652 1 is a young star that showed a strong
mid-infrared (mid-IR, 8-25 μm) excess in all observations before
2008, which is consistent with a dusty disk. Between 2008 and 2010
the mid-IR luminosity of this system dropped dramatically by at
least a factor of 30 suggesting a loss of dust mass of an order of
magnitude or more.
Aims: We aim to constrain possible models
including the removal of disk material by stellar activity processes,
the presence of a binary companion, or other explanations suggested
in the literature.
Methods: We present new X-ray observations,
optical spectroscopy, near-IR interferometry, and mid-IR photometry of
this system to constrain its parameters and further explore the cause
of the dust mass loss.
Results: In X-rays TYC8241 2652 1 has
all the properties expected from a young star: Its luminosity is in
the saturation regime and the abundance pattern shows enhancement of
O/Fe. The photospheric Hα line is filled with a weak emission feature,
indicating chromospheric activity that is consistent with the observed
level of coronal emission. Interferometry does not detect a companion
and sets upper limits on the companion mass of 0.2, 0.35, 0.1, and
0.05 M⊙ at projected physical separations of 0.1-4 AU,
4-5 AU, 5-10 AU, and 10-30 AU, respectively (assuming a distance of
120.9 pc). Our mid-IR measurements, the first of the system since 2012,
are consistent with the depleted dust level seen after 2009.
Conclusions: The new data confirm that stellar activity is unlikely to
destroy the dust in the disk and shows that scenarios, in which either
TYC8241 2652 1 heats the disk of a binary companion or a potential
companion heats the disk of TYC8241 2652 1, are unlikely. Based
on observations made with ESO telescopes at the Paranal Observatory
(ESO program IDs 090.C-0697(A), 090.C-0904(A), and 095.C-0438(A)) and
on observations obtained with XMM-Newton, an ESA science mission with
instruments and contributions directly funded by ESA Member States
and NASA.
Title: A High-mass Protobinary System with Spatially Resolved
Circumstellar Accretion Disks and Circumbinary Disk
Authors: Kraus, S.; Kluska, J.; Kreplin, A.; Bate, M.; Harries, T. J.;
Hofmann, K. -H.; Hone, E.; Monnier, J. D.; Weigelt, G.; Anugu, A.;
de Wit, W. J.; Wittkowski, M.
Bibcode: 2017ApJ...835L...5K
Altcode: 2016arXiv161207804K
High-mass multiples might form via fragmentation of self-gravitational
disks or alternative scenarios such as disk-assisted capture. However,
only a few observational constraints exist on the architecture
and disk structure of high-mass protobinaries and their accretion
properties. Here, we report the discovery of a close (57.9 ± 0.2
mas = 170 au) high-mass protobinary, IRAS17216-3801, where our
VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image
the circumstellar disks around the individual components with ∼3
mas resolution. We estimate the component masses to ∼20 and ∼18
M⊙ and find that the radial intensity profiles can be
reproduced with an irradiated disk model, where the inner regions
are excavated of dust, likely tracing the dust sublimation region in
these disks. The circumstellar disks are strongly misaligned with
respect to the binary separation vector, which indicates that the
tidal forces did not have time to realign the disks, pointing toward
a young dynamical age of the system. We constrain the distribution of
the Brγ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry
and VLT/CRIRES spectro-astrometry and find that the secondary is
accreting at a higher rate than the primary. VLT/NACO imaging shows
L‧-band emission on (3-4)× larger scales than the binary separation,
matching the expected dynamical truncation radius for the circumbinary
disk. The IRAS17216-3801 system is ∼3× more massive and ∼5× more
compact than other high-mass multiplies imaged at infrared wavelength
and the first high-mass protobinary system where circumstellar and
circumbinary dust disks could be spatially resolved. This opens
exciting new opportunities for studying star-disk interactions and
the role of multiplicity in high-mass star formation. Based
on observations made with ESO telescopes at Paranal Observatory
under program IDs 60.A-9174(A), 089.C-0819(A,C), 089.C-0959(D,E),
094.C-0153(A), 096.C-0652(A).
Title: Clumpy dust clouds and extended atmosphere of the AGB star
W Hydrae revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER. II. Time
variations between pre-maximum and minimum light
Authors: Ohnaka, K.; Weigelt, G.; Hofmann, K. -H.
Bibcode: 2017A&A...597A..20O
Altcode: 2016A&A...597A..20O; 2016arXiv161104622O
Aims: Our recent visible polarimetric images of the
well-studied AGB star W Hya taken at pre-maximum light (phase 0.92) with
VLT/SPHERE-ZIMPOL have revealed clumpy dust clouds close to the star at
2 R⋆. We present second-epoch SPHERE-ZIMPOL observations of
W Hya at minimum light (phase 0.54) as well as high-spectral resolution
long-baseline interferometric observations with the AMBER instrument
at the Very Large Telescope Interferometer (VLTI).
Methods:
We observed W Hya with VLT/SPHERE-ZIMPOL at three wavelengths in the
continuum (645, 748, and 820 nm), in the Hα line at 656.3 nm, and in
the TiO band at 717 nm. The VLTI/AMBER observations were carried out
in the wavelength region of the CO first overtone lines near 2.3 μm
with a spectral resolution of 12 000.
Results: The high-spatial
resolution polarimetric images obtained with SPHERE-ZIMPOL have allowed
us to detect clear time variations in the clumpy dust clouds as close
as 34-50 mas (1.4-2.0 R⋆) to the star. We detected
the formation of a new dust cloud as well as the disappearance of
one of the dust clouds detected at the first epoch. The Hα and TiO
emission extends to 150 mas ( 6 R⋆), and the Hα images
obtained at two epochs reveal time variations. The degree of linear
polarization measured at minimum light, which ranges from 13 to 18%,
is higher than that observed at pre-maximum light. The power-law-type
limb-darkened disk fit to the AMBER data in the continuum results in
a limb-darkened disk diameter of 49.1 ± 1.5 mas and a limb-darkening
parameter of 1.16 ± 0.49, indicating that the atmosphere is more
extended with weaker limb-darkening compared to pre-maximum light. Our
Monte Carlo radiative transfer modeling shows that the second-epoch
SPHERE-ZIMPOL data can be explained by a shell of 0.1 μm grains
of Al2O3, Mg2SiO4, and
MgSiO3 with a 550 nm optical depth of 0.6 ± 0.2 and an inner
and outer radii of 1.3 R⋆ and 10 ± 2R⋆,
respectively. Our modeling suggests the predominance of small (0.1
μm) grains at minimum light, in marked contrast to the predominance
of large (0.5 μm) grains at pre-maximum light.
Conclusions:
The variability phase dependence of the characteristic grain size
implies that small grains might just have started to form at minimum
light in the wake of a shock, while the pre-maximum light phase might
have corresponded to the phase of efficient grain growth. Based
on SPHERE and AMBER observations made with the Very Large Telescope
and Very Large Telescope Interferometer of the European Southern
Observatory. Program ID: 095.D-0397(B) and 092.D-0461(A).
Title: The fossil wind structures of Eta Carinae: changes across
one 5.54-yr cycle
Authors: Gull, Theodore R.; Madura, Thomas I.; Teodoro, Mairan;
Clementel, Nicola; Corcoran, Michael; Damineli, Augusto; Groh, Jose H.;
Hamaguchi, Kenji; Hillier, D. John; Moffat, Anthony F. J.; Richardson,
Noel D.; Weigelt, Gerd; Lindler, Don; Feggans, Keith
Bibcode: 2016MNRAS.462.3196G
Altcode: 2016arXiv160806193G
Eta Carinae, the closest, active, massive binary containing a highly
unstable Luminous Blue Variable, exhibits expanding, compressed wind
shells, seen in emission, that are spatially and spectrally resolved by
Hubble Space Telescope/Space Telescope Imaging Spectrograph. Starting
in 2009 June, these structures were mapped across its 5.54-yr, highly
elliptical, binary orbit to follow temporal changes in the light of
[Fe III] 4659 Å and [Fe II] 4815 Å. The emissions trace portions of
fossil wind shells, that were formed by wind-wind interactions across
each cycle. Over the high-ionization state, dense arcs, photoionized
by far-ultraviolet radiation from the hot secondary, are seen in
[Fe III]. Other arcs, ionized by mid-ultraviolet radiation from the
primary star, are seen in [Fe II]. The [Fe III] structures tend to be
interior to [Fe II] structures that trace extensive, less disturbed
primary wind. During the brief periastron passage when the secondary
plunges deep into the primary's extremely dense wind, on the far side
of primary star, high-ionization [Fe III] structures fade and reappear
in [Fe II]. Multiple fossil wind structures were traced across the
5.7-yr monitoring interval. The strong similarity of the expanding
[Fe II] shells suggests that the wind and photoionization properties
of the massive binary have not changed substantially from one orbit
to the next over the past several orbital cycles. These observations
trace structures that can be used to test 3D hydrodynamical and
radiative-transfer models of massive, interacting winds. They also
provide a baseline for following future changes in η Car, especially
of its winds and photoionization properties.
Title: V346 Normae: first post-outburst observations of an FU
Orionis star
Authors: Kraus, S.; Caratti o Garatti, A.; Garcia-Lopez, R.; Kreplin,
A.; Aarnio, A.; Monnier, J. D.; Naylor, T.; Weigelt, G.
Bibcode: 2016MNRAS.462L..61K
Altcode: 2016arXiv160703114K
During their formation phase, stars gain most of their mass in
violent episodic accretion events, such as observed in FU Orionis
(FUor) and EXor stars. V346 Normae is a well-studied FUor that
underwent a strong outburst beginning around 1980. Here, we report
on photometric and spectroscopic observations, which show that the
visual/near-infrared brightness has decreased dramatically between
the 1990s and 2010 (ΔR ≈ 10.9 mag, ΔJ ≈ 7.8 mag and ΔK ≈ 5.8
mag). The spectral properties of this fading event cannot be explained
by variable extinction alone, but indicate a drop in accretion rate
by two to three orders of magnitude. This is the first time that
a member of the FUor class has been observed to switch to a very
low accretion phase. Remarkably, in the last few years (2011-2015)
V346 Nor has brightened again at all near-infrared wavelengths,
indicating the onset of a new outburst event. The observed behaviour
might be consistent with the clustered luminosity bursts that have been
predicted by recent gravitational instability and fragmentation models
for the early stages of protostellar evolution. Given V346 Nor's unique
characteristics (concerning outburst duration, repetition frequency
and spectroscopic diagnostics), our results also highlight the need
to revisit the FUor/EXor classification scheme.
Title: VLTI-AMBER velocity-resolved aperture-synthesis imaging of η
Carinae with a spectral resolution of 12 000. Studies of the primary
star wind and innermost wind-wind collision zone
Authors: Weigelt, G.; Hofmann, K. -H.; Schertl, D.; Clementel, N.;
Corcoran, M. F.; Damineli, A.; de Wit, W. -J.; Grellmann, R.; Groh,
J.; Guieu, S.; Gull, T.; Heininger, M.; Hillier, D. J.; Hummel,
C. A.; Kraus, S.; Madura, T.; Mehner, A.; Mérand, A.; Millour, F.;
Moffat, A. F. J.; Ohnaka, K.; Patru, F.; Petrov, R. G.; Rengaswamy,
S.; Richardson, N. D.; Rivinius, T.; Schöller, M.; Teodoro, M.;
Wittkowski, M.
Bibcode: 2016A&A...594A.106W
Altcode: 2016arXiv161005438W
Context. The mass loss from massive stars is not understood
well. η Carinae is a unique object for studying
the massive stellar wind during the luminous blue variable phase. It
is also an eccentric binary with a period of 5.54 yr. The nature
of both stars is uncertain, although we know from X-ray studies
that there is a wind-wind collision whose properties change with
orbital phase.
Aims: We want to investigate the structure and
kinematics of η Car's primary star wind and wind-wind collision
zone with a high spatial resolution of ~6 mas (~14 au) and high
spectral resolution of R = 12 000.
Methods: Observations of
η Car were carried out with the ESO Very Large
Telescope Interferometer (VLTI) and the AMBER instrument between
approximately five and seven months before the August 2014 periastron
passage. Velocity-resolved aperture-synthesis images were reconstructed
from the spectrally dispersed interferograms. Interferometric studies
can provide information on the binary orbit, the primary wind, and
the wind collision.
Results: We present velocity-resolved
aperture-synthesis images reconstructed in more than 100 different
spectral channels distributed across the Brγ 2.166 μm emission
line. The intensity distribution of the images strongly depends
on wavelength. At wavelengths corresponding to radial velocities of
approximately -140 to - 376 km s-1 measured relative to line
center, the intensity distribution has a fan-shaped structure. At
the velocity of - 277 km s-1, the position angle of
the symmetry axis of the fan is ~126°. The fan-shaped structure
extends approximately 8.0 mas (~18.8 au) to the southeast and 5.8
mas (~13.6 au) to the northwest, measured along the symmetry axis at
the 16% intensity contour. The shape of the intensity distributions
suggests that the obtained images are the first direct images of
the innermost wind-wind collision zone. Therefore, the observations
provide velocity-dependent image structures that can be used to
test three-dimensional hydrodynamical, radiative transfer models of
the massive interacting winds of η Car. Based on observations
collected at the European Organisation for Astronomical Research in the
Southern Hemisphere under ESO program 092.D-0289(A).The reconstructed
digital images are only available at the CDS via anonymous ftp to
http://cdsarc.u-strasbg.fr
(http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A106
Title: VizieR Online Data Catalog: eta Car velocity-resolved imaging
(Weigelt+, 2016)
Authors: Weigelt, G.; Hofmann, K. -H.; Schertl, D.; Clementel, N.;
Corcoran, M. F.; Damineli, A.; de Wit, W. -J.; Grellmann, R.; Groh,
J.; Guieu, S.; Gull, T.; Heininger, M.; Hillier, D. J.; Hummel,
C. A.; Kraus, S.; Madura, T.; Mehner, A.; Merand, A.; Millour, F.;
Moffat, A. F. J.; Ohnaka, K.; Patru, F.; Petrov, R. G.; Rengaswamy,
S.; Richardson, N. D.; Rivinius, T.; Schoeller, M.; Teodoro, M.;
Wittkowski, M.
Bibcode: 2016yCat..35940106W
Altcode:
We present the reconstructed images from Fig. 4 of the paper. The
interferometric data were taken with the ESO VLTI and the AMBER
instrument with high spectral resolution (R=12000) in many spectral
channels across the Brackett Gamma line at 2.166 micron. 96 images
were reconstructed at velocity channels from -663km/s to 520km/s. The velocity of each channel is coded into the filename. Plate
scale is 0.781mas/pixel. North is up, and east to the left. FOV is
50mas. The resolution of the images is ~6 mas. (2 data files).
Title: Grown-up stars physics with MATISSE
Authors: Millour, F.; Hron, J.; Chiavassa, A.; Weigelt, G.; Soulain,
A.; Khorrami, Z.; Meilland, A.; Nardetto, N.; Paladini, C.; Domiciano
de Souza, A.; Niccolini, G.; Hofmann, K. -H.; Schertl, D.; Stee, P.;
Bendjoya, P.; Thévenin, F.; Vakili, F.; Berio, P.; Lanz, T.; Matter,
A.; Cruzalèbes, P.; Petrov, R.; Lopez, B.
Bibcode: 2016SPIE.9907E..3QM
Altcode: 2016arXiv160702393M
MATISSE represents a great opportunity to image the environment around
massive and evolved stars. This will allow one to put constraints
on the circumstellar structure, on the mass ejection of dust and its
reorganization, and on the dust-nature and formation processes. MATISSE
measurements will often be pivotal for the understanding of large
multiwavelength datasets on the same targets collected through
many high-angular resolution facilities at ESO like sub-millimeter
interferometry (ALMA), near-infrared adaptive optics (NACO, SPHERE),
interferometry (PIONIER, GRAVITY), spectroscopy (CRIRES), and
mid-infrared imaging (VISIR). Among main sequence and evolved stars,
several cases of interest have been identified that we describe in
this paper.
Title: An overview of the mid-infrared spectro-interferometer MATISSE:
science, concept, and current status
Authors: Matter, A.; Lopez, B.; Antonelli, P.; Lehmitz, M.; Bettonvil,
F.; Beckmann, U.; Lagarde, S.; Jaffe, W.; Petrov, R.; Berio, P.;
Millour, F.; Robbe-Dubois, S.; Glindemann, A.; Bristow, P.; Schoeller,
M.; Lanz, T.; Henning, T.; Weigelt, G.; Heininger, M.; Morel, S.;
Cruzalebes, P.; Meisenheimer, K.; Hofferbert, R.; Wolf, S.; Bresson,
Y.; Agocs, T.; Allouche, F.; Augereau, J. -C.; Avila, G.; Bailet, C.;
Behrend, J.; van Belle, G.; Berger, J. -P.; van Boekel, R.; Bourget,
P.; Brast, R.; Clausse, J. -M.; Connot, C.; Conzelmann, R.; Csepany,
G.; Danchi, W. C.; Delbo, M.; Dominik, C.; van Duin, A.; Elswijk, E.;
Fantei, Y.; Finger, G.; Gabasch, A.; Gonté, F.; Graser, U.; Guitton,
F.; Guniat, S.; De Haan, M.; Haguenauer, P.; Hanenburg, H.; Hofmann,
K. -H.; Hogerheijde, M.; ter Horst, R.; Hron, J.; Hummel, C.; Isderda,
J.; Ives, D.; Jakob, G.; Jasko, A.; Jolley, P.; Kiraly, S.; Kragt,
J.; Kroener, T.; Kroes, G.; Kuindersma, S.; Labadie, L.; Laun, W.;
Leinert, C.; Lizon, J. -L.; Lucuix, C.; Marcotto, A.; Martinache,
F.; Martinot-Lagarde, G.; Mauclert, N.; Mehrgan, L.; Meilland, A.;
Mellein, M.; Menardi, S.; Merand, A.; Neumann, U.; Nussbaum, E.;
Ottogalli, S.; Palsa, R.; Panduro, J.; Pantin, E.; Percheron, I.;
Phan Duc, T.; Pott, J. -U.; Pozna, E.; Roelfsema, R.; Rupprecht, G.;
Schertl, D.; Schmidt, C.; Schuil, M.; Spang, A.; Stegmeier, J.; Tromp,
N.; Vakili, F.; Vannier, M.; Wagner, K.; Venema, L.; Woillez, J.
Bibcode: 2016SPIE.9907E..0AM
Altcode: 2016arXiv160802350M
MATISSE is the second-generation mid-infrared spectrograph and imager
for the Very Large Telescope Interferometer (VLTI) at Paranal. This
new interferometric instrument will allow significant advances by
opening new avenues in various fundamental research fields: studying
the planet-forming region of disks around young stellar objects,
understanding the surface structures and mass loss phenomena affecting
evolved stars, and probing the environments of black holes in active
galactic nuclei. As a first breakthrough, MATISSE will enlarge the
spectral domain of current optical interferometers by offering the L
and M bands in addition to the N band. This will open a wide wavelength
domain, ranging from 2.8 to 13 μm, exploring angular scales as small
as 3 mas (L band) / 10 mas (N band). As a second breakthrough, MATISSE
will allow mid-infrared imaging - closure-phase aperture-synthesis
imaging - with up to four Unit Telescopes (UT) or Auxiliary Telescopes
(AT) of the VLTI. Moreover, MATISSE will offer a spectral resolution
range from R ∼ 30 to R ∼ 5000. Here, we present one of the main
science objectives, the study of protoplanetary disks, that has driven
the instrument design and motivated several VLTI upgrades (GRA4MAT
and NAOMI). We introduce the physical concept of MATISSE including
a description of the signal on the detectors and an evaluation of
the expected performances. We also discuss the current status of
the MATISSE instrument, which is entering its testing phase, and the
foreseen schedule for the next two years that will lead to the first
light at Paranal.
Title: The 2016 interferometric imaging beauty contest
Authors: Sanchez-Bermudez, J.; Thiébaut, E.; Hofmann, K. -H.;
Heininger, M.; Schertl, D.; Weigelt, G.; Millour, F.; Schutz, A.;
Ferrari, A.; Vannier, M.; Mary, D.; Young, J.
Bibcode: 2016SPIE.9907E..1DS
Altcode:
Image reconstruction in optical interferometry has gained considerable
importance for astrophysical studies during the last decade. This has
been mainly due to improvements in the imaging capabilities of existing
interferometers and the expectation of new facilities in the coming
years. However, despite the advances made so far, image synthesis in
optical interferometry is still an open field of research. Since 2004,
the community has organized a biennial contest to formally test the
different methods and algorithms for image reconstruction. In 2016,
we celebrated the 7th edition of the "Interferometric Imaging Beauty
Contest". This initiative represented an open call to participate
in the reconstruction of a selected set of simulated targets with
a wavelength-dependent morphology as they could be observed by the
2nd generation of VLTI instruments. This contest represents a unique
opportunity to benchmark, in a systematic way, the current advances
and limitations in the field, as well as to discuss possible future
approaches. In this contribution, we summarize: (a) the rules of
the 2016 contest; (b) the different data sets used and the selection
procedure; (c) the methods and results obtained by each one of the
participants; and (d) the metric used to select the best reconstructed
images. Finally, we named Karl-Heinz Hofmann and the group of the
Max-Planck-Institut fur Radioastronomie as winners of this edition of
the contest.
Title: Planet Formation Imager (PFI): science vision and key
requirements
Authors: Kraus, Stefan; Monnier, John D.; Ireland, Michael J.;
Duchêne, Gaspard; Espaillat, Catherine; Hönig, Sebastian; Juhasz,
Attila; Mordasini, Chris; Olofsson, Johan; Paladini, Claudia; Stassun,
Keivan; Turner, Neal; Vasisht, Gautam; Harries, Tim J.; Bate, Matthew
R.; Gonzalez, Jean-François; Matter, Alexis; Zhu, Zhaohuan; Panic,
Olja; Regaly, Zsolt; Morbidelli, Alessandro; Meru, Farzana; Wolf,
Sebastian; Ilee, John; Berger, Jean-Philippe; Zhao, Ming; Kral,
Quentin; Morlok, Andreas; Bonsor, Amy; Ciardi, David; Kane, Stephen
R.; Kratter, Kaitlin; Laughlin, Greg; Pepper, Joshua; Raymond, Sean;
Labadie, Lucas; Nelson, Richard P.; Weigelt, Gerd; ten Brummelaar,
Theo; Pierens, Arnaud; Oudmaijer, Rene; Kley, Wilhelm; Pope, Benjamin;
Jensen, Eric L. N.; Bayo, Amelia; Smith, Michael; Boyajian, Tabetha;
Quiroga-Nuñez, Luis Henry; Millan-Gabet, Rafael; Chiavassa, Andrea;
Gallenne, Alexandre; Reynolds, Mark; de Wit, Willem-Jan; Wittkowski,
Markus; Millour, Florentin; Gandhi, Poshak; Ramos Almeida, Cristina;
Alonso Herrero, Almudena; Packham, Chris; Kishimoto, Makoto; Tristram,
Konrad R. W.; Pott, Jörg-Uwe; Surdej, Jean; Buscher, David; Haniff,
Chris; Lacour, Sylvestre; Petrov, Romain; Ridgway, Steve; Tuthill,
Peter; van Belle, Gerard; Armitage, Phil; Baruteau, Clement; Benisty,
Myriam; Bitsch, Bertram; Paardekooper, Sijme-Jan; Pinte, Christophe;
Masset, Frederic; Rosotti, Giovanni
Bibcode: 2016SPIE.9907E..1KK
Altcode: 2016arXiv160800578K
The Planet Formation Imager (PFI) project aims to provide a strong
scientific vision for ground-based optical astronomy beyond the upcoming
generation of Extremely Large Telescopes. We make the case that a
breakthrough in angular resolution imaging capabilities is required in
order to unravel the processes involved in planet formation. PFI will be
optimised to provide a complete census of the protoplanet population
at all stellocentric radii and over the age range from 0.1 to 100
Myr. Within this age period, planetary systems undergo dramatic changes
and the final architecture of planetary systems is determined. Our goal
is to study the planetary birth on the natural spatial scale where the
material is assembled, which is the "Hill Sphere" of the forming planet,
and to characterise the protoplanetary cores by measuring their masses
and physical properties. Our science working group has investigated the
observational characteristics of these young protoplanets as well as
the migration mechanisms that might alter the system architecture. We
simulated the imprints that the planets leave in the disk and study how
PFI could revolutionise areas ranging from exoplanet to extragalactic
science. In this contribution we outline the key science drivers of PFI
and discuss the requirements that will guide the technology choices,
the site selection, and potential science/technology tradeoffs.
Title: Imaging capabilities of the VLTI/MATISSE
spectro-interferometric instrument
Authors: Sanchez-Bermudez, J.; Pott, J. -U.; van Boekel, R.; Henning,
T.; Baron, F.; Matter, A.; Lopez, B.; Millour, F.; Weigelt, G.;
Hofmann, K. -H.; Schertl, D.
Bibcode: 2016SPIE.9907E..0BS
Altcode:
During the last decade, the first generation of beam combiners at
the Very Large Telescope Interferometer has proved the importance
of optical interferometry for high-angular resolution astrophysical
studies in the nearand mid-infrared. With the advent of 4-beam
combiners at the VLTI, the u - v coverage per pointing increases
significantly, providing an opportunity to use reconstructed images
as powerful scientific tools. Here, we present our ongoing studies to
characterize the imaging capabilities of the Multi-AperTure mid-infrared
SpectroScopic Experiment (MATISSE), a second-generation instrument
for the Very Large Telescope Interferometer (VLTI). By providing
simultaneous observations with 6 baselines and spectral resolutions
up to R 5000. MATISSE will deliver, for the first time, thermal-IR
interferometric data with enough u-v coverage and phase information
for imaging. In this work, we report detailed image reconstruction
studies carried out with the image reconstruction package SQUEEZE. For
our studies, we use realistic simulated MATISSE data from radiative
transfer simulations of a proto-planetary disk. In particular,
we will discuss the role of the regularization function and of the
initial brightness distribution. MATISSE will perform observations
at three different mid-infrared bands: L, M and N. Hence, due to its
large bandwidth, chromatic effects should be taken into account when
image reconstruction is attempted. We also discuss the capabilities
of SQUEEZE to perform multi-wavelength image reconstruction. Finally,
we perform an analysis of the image quality and present our future
line of research. The work here presented is being carried out within
the Opticon FP7-2 joint research activity on interferometric imaging.
Title: Data reduction for the MATISSE instrument
Authors: Millour, F.; Berio, P.; Heininger, M.; Hofmann, K. -H.;
Schertl, D.; Weigelt, G.; Guitton, F.; Jaffe, W.; Beckmann, U.;
Petrov, R.; Allouche, F.; Robbe-Dubois, S.; Lagarde, S.; Soulain,
A.; Meilland, A.; Matter, A.; Cruzalèbes, P.; Lopez, B.
Bibcode: 2016SPIE.9907E..23M
Altcode: 2016arXiv160801913M
We present in this paper the general formalism and data processing steps
used in the MATISSE data reduction software, as it has been developed
by the MATISSE consortium. The MATISSE instrument is the mid-infrared
new generation interferometric instrument of the Very Large Telescope
Interferometer (VLTI). It is a 2-in-1 instrument with 2 cryostats and 2
detectors: one 2k × 2k Rockwell Hawaii 2RG detector for L&M-bands,
and one 1k × 1k Raytheon Aquarius detector for N-band, both read at
high framerates, up to 30 frames per second. MATISSE is undergoing
its first tests in laboratory today.
Title: Image reconstruction method IRBis for optical/infrared
long-baseline interferometry
Authors: Hofmann, Karl-Heinz; Heininger, Matthias; Schertl, Dieter;
Weigelt, Gerd; Millour, Florentin; Berio, Philippe
Bibcode: 2016SPIE.9907E..3HH
Altcode:
IRBis is an image reconstruction method for optical/infrared
long-baseline interferometry. IRBis can reconstruct images from (a)
measured visibilities and closure phases, or from (b) measured complex
visibilities (i.e. the Fourier phases and visibilities). The applied
optimization routine ASA CG is based on conjugate gradients. The method
allows the user to implement different regularizers, as for example,
maximum entropy, smoothness, total variation, etc., and apply residual
ratios as an additional metric for goodness-of-fit. In addition, IRBis
allows the user to change the following reconstruction parameters:
(a) FOV of the area to be reconstructed, (b) the size of the pixel-grid
used, (c) size of a binary mask in image space allowing reconstructed
intensities < 0 within the binary mask only, (d) the strength of
the regularization, etc. The two main reconstruction parameters are
the size of the binary mask in image space (c) and the strength of the
regularization (d). Several values of these two parameters are tested
within the algorithm. The quality of the different reconstructions
obtained is roughly estimated by evaluation of the differences between
the measured data and the reconstructed image (using the reduced
χ2 values and the residual ratios). The best-quality
reconstruction and a few reconstructions sorted according to their
quality are provided to the user as resulting reconstructions. We
describe the theory of IRBis and will present several applications to
simulated interferometric data and data of real astronomical objects:
(a) We have investigated image reconstruction experiments of MATISSE
target candidates by computer simulations. We have modeled gaps in
a disk of a young stellar object and have simulated interferometric
data (squared visibilities and closure phases) with a signal-to-noise
ratio as expected for MATISSE observations. We have performed image
reconstruction experiments with this model for different flux levels
of the target and different amount of observing time, that is, with
different uv coverages. As expected, the quality of the reconstructions
clearly depends on the flux of the source and the completeness of
the uv coverage. (b) We also discuss reconstructions of the Luminous
Blue Variable η Carinae obtained from AMBER observations in the high
spectral resolution mode in the K band. The images were reconstruction
(1) using the closure phases and (2) using the absolute phases derived
from the measured wavelength-differential phases and the closure phase
reconstruction in the continuum.
Title: Science with MATISSE
Authors: Wolf, Sebastian; Lopez, Bruno; Augereau, Jean-Charles;
Delbo, Marco; Dominik, Carsten; Henning, Thomas; Hofmann, Karl-Heinz;
Hogerheijde, Michiel; Hron, Josef; Jaffe, Walter; Lanz, Thierry;
Meisenheimer, Klaus; Millour, Florentin; Pantin, Eric; Petrov, Roman;
Schertl, Dieter; van Boekel, Roy; Weigelt, Gerd; Chiavassa, Andrea;
Juhasz, Attila; Matter, Alexis; Meilland, Anthony; Nardetto, Nicolas;
Paladini, Claudia
Bibcode: 2016SPIE.9907E..3SW
Altcode: 2016arXiv160906152W
We present an overview of the scientific potential of MATISSE, the
Multi Aperture mid-Infrared SpectroScopic Experiment for the Very
Large Telescope Interferometer. For this purpose we outline selected
case studies from various areas, such as star and planet formation,
active galactic nuclei, evolved stars, extrasolar planets, and solar
system minor bodies and discuss strategies for the planning and analysis
of future MATISSE observations. Moreover, the importance of MATISSE
observations in the context of complementary high-angular resolution
observations at near-infrared and submillimeter/millimeter wavelengths
is highlighted.
Title: Brackett γ radiation from the inner gaseous accretion disk,
magnetosphere, and disk wind region of Herbig AeBe stars
Authors: Tambovtseva, L. V.; Grinin, V. P.; Weigelt, G.
Bibcode: 2016A&A...590A..97T
Altcode:
Various disk and outflow components such as the magnetosphere, the disk
wind, the gaseous accretion disk, and other regions may contribute to
the hydrogen line emission of young Herbig AeBe stars. Non-LTE modeling
was performed to show the influence of the model parameters of each
emitting region on the intensity and shape of the Brγ line profile,
to present the spatial brightness distribution of each component,
and to compare the contribution of each component to the total line
emission. The modeling shows that the disk wind is the dominant
contributor to the Brγ line rather than the magnetosphere and inner
gaseous accretion disk. The contribution of the disk wind region to
the Hα line is also considered.
Title: Tracing jet emission at the base of a high-mass YSO. First
AMBER/VLTI observations of the Brγ emission in IRAS 13481-6124
Authors: Caratti o Garatti, A.; Stecklum, B.; Weigelt, G.; Schertl,
D.; Hofmann, K. -H.; Kraus, S.; Oudmaijer, R. D.; de Wit, W. J.;
Sanna, A.; Garcia Lopez, R.; Kreplin, A.; Ray, T. P.
Bibcode: 2016A&A...589L...4C
Altcode: 2016arXiv160306860G; 2016A&A...589L...4G
Aims: To probe the circumstellar environment of IRAS 13481-6124,
a 20 M⊙ high-mass young stellar object (HMYSO) with a
collimated parsec-scale jet and an accretion disc, we investigate
the origin of its Brγ emission line through near-infrared (NIR)
interferometry.
Methods: We present the first AMBER/VLTI
observations of the Brγ emitting region in an HMYSO at medium spectral
resolution (R = 1500).
Results: Our AMBER/VLTI observations
reveal a spatially and spectrally resolved Brγ line in emission with
a strong P Cygni profile, indicating outflowing matter with a terminal
velocity of ~500 km s-1. Visibilities, differential phases,
and closure phases are detected in our observations within the spectral
line and in the adjacent continuum. Both total visibilities (continuum
plus line emitting region) and pure-line visibilities indicate that
the Brγ-emitting region is more compact (2-4 mas in diameter or ~6-13
au at 3.2 kpc) than the continuum-emitting region (~5.4 mas or ~17
au). The absorption feature is also spatially resolved at the longest
baselines (81 and 85 m) and has a visibility that is slightly smaller
than the continuum-emitting region. The differential phases at the four
longest baselines display an "S"-shaped structure across the line,
peaking in the blue- and red-shifted high-velocity components. The
calibrated photocentre shifts are aligned with the known jet axis, I.e
they are probably tracing an ionised jet. The high-velocity components
(vr ~ 100-500 km s-1) are located far from the
source, whereas the low-velocity components (0-100 km s-1)
are observed to be closer, indicating a strong acceleration of the gas
flow in the inner 10 au. Finally, a non-zero closure phase along the
continuum is detected. By comparing our observations with the synthetic
images of the continuum around 2.16 μm, we confirm that this feature
originates from the asymmetric brightness distribution of the continuum
owing to the inclination of the inner disc. Based on observations
collected at the VLT (ESO Paranal, Chile) with programmes 090.C-0371(B).
Title: Clumpy dust clouds and extended atmosphere of the AGB star
W Hydrae revealed with VLT/SPHERE-ZIMPOL and VLTI/AMBER
Authors: Ohnaka, K.; Weigelt, G.; Hofmann, K. -H.
Bibcode: 2016A&A...589A..91O
Altcode: 2016arXiv160301197O
Context. Dust formation is thought to play an important role in the
mass loss from stars at the asymptotic giant branch (AGB); however,
where and how dust forms is still open to debate.
Aims: We
present visible polarimetric imaging observations of the well-studied
AGB star W Hya taken with VLT/SPHERE-ZIMPOL as well as high spectral
resolution long-baseline interferometric observations taken with the
AMBER instrument at the Very Large Telescope Interferometer (VLTI). Our
goal is to spatially resolve the dust and molecule formation region
within a few stellar radii.
Methods: We observed W Hya with
VLT/SPHERE-ZIMPOL at three wavelengths in the continuum (645, 748, and
820 nm), in the Hα line at 656.3 nm, and in the TiO band at 717 nm. The
VLTI/AMBER observations were carried out in the wavelength region of
the CO first overtone lines near 2.3 μm with a spectral resolution of
12000.
Results: Taking advantage of the polarimetric imaging
capability of SPHERE-ZIMPOL combined with the superb adaptive optics
performance, we succeeded in spatially resolving three clumpy dust
clouds located at ~50 mas (~2 R⋆) from the central star,
revealing dust formation very close to the star. The AMBER data
in the individual CO lines suggest a molecular outer atmosphere
extending to ~3 R⋆. Furthermore, the SPHERE-ZIMPOL
image taken over the Hα line shows emission with a radius of up to
~160 mas (~7 R⋆). We found that dust, molecular gas, and
Hα-emitting hot gas coexist within 2-3 R⋆. Our modeling
suggests that the observed polarized intensity maps can reasonably be
explained by large (0.4-0.5 μm) grains of Al2O3,
Mg2SiO4, or MgSiO3 in an optically
thin shell (τ550nm = 0.1 ± 0.02) with an inner and outer
boundary radius of 1.9-2.0 R⋆ and 3 ± 0.5R⋆,
respectively. The observed clumpy structure can be reproduced by a
density enhancement of a factor of 4 ± 1.
Conclusions: The grain
size derived from our modeling of the SPHERE-ZIMPOL polarimetric images
is consistent with the prediction of the hydrodynamical models for
the mass loss driven by the scattering due to micron-sized grains. The
detection of the clumpy dust clouds close to the star lends support to
the dust formation induced by pulsation and large convective cells as
predicted by the 3D simulations for AGB stars. Based on SPHERE and
AMBER observations made with the Very Large Telescope and Very Large
Telescope Interferometer of the European Southern Observatory. Program
ID: 095.D-0397(D) and 093.D-0468(A).
Title: Resolving the inner disk of UX Orionis
Authors: Kreplin, A.; Madlener, D.; Chen, L.; Weigelt, G.; Kraus,
S.; Grinin, V.; Tambovtseva, L.; Kishimoto, M.
Bibcode: 2016A&A...590A..96K
Altcode:
Aims: The cause of the UX Ori variability
in some Herbig Ae/Be stars is still a matter of debate. Detailed
studies of the circumstellar environment of UX Ori objects (UXORs) are
required to test the hypothesis that the observed drop in photometry
might be related to obscuration events.
Methods: Using near-
and mid-infrared interferometric AMBER and MIDI observations, we
resolved the inner circumstellar disk region around UX Ori.
Results: We fitted the K-, H-, and N-band visibilities and the spectral
energy distribution (SED) of UX Ori with geometric and parametric disk
models. The best-fit K-band geometric model consists of an inclined ring
and a halo component. We obtained a ring-fit radius of 0.45 ± 0.07 AU
(at a distance of 460 pc), an inclination of 55.6 ± 2.4°, a position
angle of the system axis of 127.5 ± 24.5°, and a flux contribution
of the over-resolved halo component to the total near-infrared excess
of 16.8 ± 4.1%. The best-fit N-band model consists of an elongated
Gaussian with a HWHM ~ 5 AU of the semi-major axis and an axis ration of
a/b ~ 3.4 (corresponding to an inclination of ~72°). With a parametric
disk model, we fitted all near- and mid-infrared visibilities and
the SED simultaneously. The model disk starts at an inner radius of
0.46 ± 0.06 AU with an inner rim temperature of 1498 ± 70 K. The
disk is seen under an nearly edge-on inclination of 70 ± 5°. This
supports any theories that require high-inclination angles to explain
obscuration events in the line of sight to the observer, for example,
in UX Ori objects where orbiting dust clouds in the disk or disk
atmosphere can obscure the central star. Based on observations
made with ESO telescopes at Paranal Observatory under program IDs:
090.C-0769, 074.C-0552.
Title: Probing the wind-launching regions of the Herbig Be star HD
58647 with high spectral resolution interferometry
Authors: Kurosawa, Ryuichi; Kreplin, A.; Weigelt, G.; Natta, A.;
Benisty, M.; Isella, Andrea; Tatulli, Eric; Massi, F.; Testi, Leonardo;
Kraus, Stefan; Duvert, G.; Petrov, Romain G.; Stee, Ph.
Bibcode: 2016MNRAS.457.2236K
Altcode: 2016arXiv160102209K
We present a study of the wind-launching region of the Herbig Be star HD
58647 using high angular (λ/2B = 0.003 arcsec) and high spectral (R =
12 000) resolution interferometric Very Large Telescope Interferometer
(VLTI)-Astronomical Multi-Beam combiner (AMBER) observations of
the near-infrared hydrogen emission line, Brγ. The star displays
double peaks in both Brγ line profile and wavelength-dependent
visibilities. The wavelength-dependent differential phases show S-shaped
variations around the line centre. The visibility level increases
in the line (by ∼0.1) at the longest projected baseline (88 m),
indicating that the size of the line emission region is smaller than
the size of the K-band continuum-emitting region, which is expected
to arise near the dust sublimation radius of the accretion disc. The
data have been analysed using radiative transfer models to probe the
geometry, size and physical properties of the wind that is emitting
Brγ. We find that a model with a small magnetosphere and a disc wind
with its inner radius located just outside of the magnetosphere can well
reproduce the observed Brγ profile, wavelength-dependent visibilities,
differential and closure phases, simultaneously. The mass-accretion
and mass-loss rates adopted for the model are dot{M}a=3.5×
10^{-7} and dot{M}_{dw}=4.5× 10^{-8} M_{odot yr^{-1}}, respectively
(dot{M}_{dw}/dot{M}a=0.13). Consequently, about 60 per cent
of the angular momentum loss rate required for a steady accretion
with the measured accretion rate is provided by the disc wind. The
small magnetosphere in HD 58647 does not contribute to the Brγ line
emission significantly.
Title: He II λ4686 Emission from the Massive Binary System in
η Car: Constraints to the Orbital Elements and the Nature of the
Periodic Minima
Authors: Teodoro, M.; Damineli, A.; Heathcote, B.; Richardson, N. D.;
Moffat, A. F. J.; St-Jean, L.; Russell, C.; Gull, T. R.; Madura, T. I.;
Pollard, K. R.; Walter, F.; Coimbra, A.; Prates, R.; Fernández-Lajús,
E.; Gamen, R. C.; Hickel, G.; Henrique, W.; Navarete, F.; Andrade,
T.; Jablonski, F.; Luckas, P.; Locke, M.; Powles, J.; Bohlsen, T.;
Chini, R.; Corcoran, M. F.; Hamaguchi, K.; Groh, J. H.; Hillier,
D. J.; Weigelt, G.
Bibcode: 2016ApJ...819..131T
Altcode: 2016arXiv160103396T
Eta Carinae (η Car) is an extremely massive binary system in which
rapid spectrum variations occur near periastron. Most notably, near
periastron the He II λ4686 line increases rapidly in strength, drops
to a minimum value, then increases briefly before fading away. To
understand this behavior, we conducted an intense spectroscopic
monitoring of the He II λ4686 emission line across the 2014.6
periastron passage using ground- and space-based telescopes. Comparison
with previous data confirmed the overall repeatability of the line
equivalent width (EW), radial velocities, and the timing of the minimum,
though the strongest peak was systematically larger in 2014 than
in 2009 by 26%. The EW variations, combined with other measurements,
yield an orbital period of 2022.7 ± 0.3 days. The observed variability
of the EW was reproduced by a model in which the line flux primarily
arises at the apex of the wind-wind collision and scales inversely
with the square of the stellar separation, if we account for the
excess emission as the companion star plunges into the hot inner
layers of the primary’s atmosphere, and including absorption from the
disturbed primary wind between the source and the observer. This model
constrains the orbital inclination to 135°-153°, and the longitude
of periastron to 234°-252°. It also suggests that periastron passage
occurred on {T}0=2456874.4\quad (+/- 1.3 days). Our model
also reproduced EW variations from a polar view of the primary star
as determined from the observed He II λ 4686 emission scattered off
the Homunculus nebula. Based in part on observations made with
the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope
Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These
observations are associated with program numbers 11506, 12013, 12508,
12750, and 13054. Support for program numbers 12013, 12508, and 12750
was provided by NASA through a grant from the Space Telescope Science
Institute, which is operated by the Association of Universities for
Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Title: The LEECH Exoplanet Imaging Survey: Characterization of
the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for
Superstellar Metallicity
Authors: Skemer, Andrew J.; Morley, Caroline V.; Zimmerman, Neil T.;
Skrutskie, Michael F.; Leisenring, Jarron; Buenzli, Esther; Bonnefoy,
Mickael; Bailey, Vanessa; Hinz, Philip; Defrére, Denis; Esposito,
Simone; Apai, Dániel; Biller, Beth; Brandner, Wolfgang; Close, Laird;
Crepp, Justin R.; De Rosa, Robert J.; Desidera, Silvano; Eisner,
Josh; Fortney, Jonathan; Freedman, Richard; Henning, Thomas; Hofmann,
Karl-Heinz; Kopytova, Taisiya; Lupu, Roxana; Maire, Anne-Lise; Males,
Jared R.; Marley, Mark; Morzinski, Katie; Oza, Apurva; Patience, Jenny;
Rajan, Abhijith; Rieke, George; Schertl, Dieter; Schlieder, Joshua;
Stone, Jordan; Su, Kate; Vaz, Amali; Visscher, Channon; Ward-Duong,
Kimberly; Weigelt, Gerd; Woodward, Charles E.
Bibcode: 2016ApJ...817..166S
Altcode: 2015arXiv151109183S
As gas giant planets and brown dwarfs radiate away the residual heat
from their formation, they cool through a spectral type transition
from L to T, which encompasses the dissipation of cloud opacity and
the appearance of strong methane absorption. While there are hundreds
of known T-type brown dwarfs, the first generation of directly imaged
exoplanets were all L type. Recently, Kuzuhara et al. announced
the discovery of GJ 504 b, the first T dwarf exoplanet. GJ 504 b
provides a unique opportunity to study the atmosphere of a new type of
exoplanet with a ∼500 K temperature that bridges the gap between the
first directly imaged planets (∼1000 K) and our own solar system's
Jupiter (∼130 K). We observed GJ 504 b in three narrow L-band filters
(3.71, 3.88, and 4.00 μm), spanning the red end of the broad methane
fundamental absorption feature (3.3 μm) as part of the LBTI Exozodi
Exoplanet Common Hunt (LEECH) exoplanet imaging survey. By comparing
our new photometry and literature photometry with a grid of custom
model atmospheres, we were able to fit GJ 504 b's unusual spectral
energy distribution for the first time. We find that GJ 504 b is well
fit by models with the following parameters: Teff = 544 ±
10 K, g < 600 m s-2, [M/H] = 0.60 ± 0.12, cloud opacity
parameter of fsed = 2-5, R = 0.96 ± 0.07 RJup,
and log(L) = -6.13 ± 0.03 L⊙, implying a hot start
mass of 3-30 Mjup for a conservative age range of 0.1-6.5
Gyr. Of particular interest, our model fits suggest that GJ 504 b has
a superstellar metallicity. Since planet formation can create objects
with nonstellar metallicities, while binary star formation cannot,
this result suggests that GJ 504 b formed like a planet, not like
a binary companion. The LBT is an international collaboration
among institutions in the United States, Italy, and Germany. LBT
Corporation partners are the University of Arizona on behalf of the
Arizona university system; Istituto Nazionale di Astrophisica, Italy;
LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck
Society, the Astrophysical Institute Potsdam, and Heidelberg University;
The Ohio State University, and the Research Corporation, on behalf of
the University of Notre Dame, University of Minnesota, and University
of Virginia.
Title: Investigating the origin and spectroscopic variability of
the near-infrared H I lines in the Herbig star VV Ser
Authors: Garcia Lopez, Rebeca; Kurosawa, Ryuichi; Caratti o Garatti,
Alessio; Kreplin, Alexander; Weigelt, Gerd; Tambovtseva, Larisa V.;
Grinin, Vladimir P.; Ray, Thomas P.
Bibcode: 2016MNRAS.456..156G
Altcode: 2015arXiv151103181G
The origin of the near-infrared (NIR) H I emission lines in young
stellar objects are not yet understood. To probe it, we present
multi-epoch LBT-LUCIFER spectroscopic observations of the Paδ, Paβ,
and Brγ lines observed in the Herbig star VV Ser, along with Very
Large Telescope Interferometer-AMBER Brγ spectro-interferometric
observations at medium resolution. Our spectroscopic observations
show line profile variability in all the H I lines. The strongest
variability is observed in the redshifted part of the line profiles. The
Brγ spectro-interferometric observations indicate that the Brγ line
emitting region is smaller than the continuum emitting region. To
interpret our results, we employed radiative transfer models with
three different flow configurations: magnetospheric accretion,
a magnetocentrifugally driven disc wind, and a schematic bipolar
outflow. Our models suggest that the H I line emission in VV Ser is
dominated by the contribution of an extended wind, perhaps a bipolar
outflow. Although the exact physical process for producing such
outflow is not known, this model is capable of reproducing the averaged
single-peaked line profiles of the H I lines. Additionally, the observed
visibilities, differential and closure phases are best reproduced
when a wind is considered. Nevertheless, the complex line profiles and
variability could be explained by changes in the relative contribution
of the magnetosphere and/or winds to the line emission. This might
indicate that the NIR H I lines are formed in a complex inner disc
region where inflow and outflow components might coexist. Furthermore,
the contribution of each of these mechanisms to the line appears time
variable, suggesting a non-steady accretion/ejection flow.
Title: The LEECH Exoplanet Imaging Survey: Orbit and Component Masses
of the Intermediate-Age, Late-Type Binary NO UMa
Authors: Schlieder, Joshua E.; Skemer, Andrew J.; Maire, Anne-Lise;
Desidera, Silvano; Hinz, Philip; Skrutskie, Michael F.; Leisenring,
Jarron; Bailey, Vanessa; Defrère, Denis; Esposito, Simone;
Strassmeier, Klaus G.; Weber, Michael; Biller, Beth A.; Bonnefoy,
Mickaël; Buenzli, Esther; Close, Laird M.; Crepp, Justin R.; Eisner,
Josh A.; Hofmann, Karl-Heinz; Henning, Thomas; Morzinski, Katie M.;
Schertl, Dieter; Weigelt, Gerd; Woodward, Charles E.
Bibcode: 2016ApJ...818....1S
Altcode: 2015arXiv151003813S
We present high-resolution Large Binocular Telescope LBTI/LMIRcam images
of the spectroscopic and astrometric binary NO UMa obtained as part of
the LBT Interferometer Exozodi Exoplanet Common Hunt exoplanet imaging
survey. Our H-, Ks-, and L‧-band observations resolve
the system at angular separations <0.″09. The components exhibit
significant orbital motion over a span of ∼7 months. We combine our
imaging data with archival images, published speckle interferometry
measurements, and existing spectroscopic velocity data to solve the
full orbital solution and estimate component masses. The masses of
the K2.0 ± 0.5 primary and K6.5 ± 0.5 secondary are 0.83 ± 0.02
M⊙ and 0.64 ± 0.02 M⊙, respectively. We also
derive a system distance of d = 25.87 ± 0.02 pc and revise the Galactic
kinematics of NO UMa. Our revised Galactic kinematics confirm NO UMa as
a nuclear member of the ∼500 Myr old Ursa Major moving group, and it
is thus a mass and age benchmark. We compare the masses of the NO UMa
binary components to those predicted by five sets of stellar evolution
models at the age of the Ursa Major group. We find excellent agreement
between our measured masses and model predictions with little systematic
scatter between the models. NO UMa joins the short list of nearby,
bright, late-type binaries having known ages and fully characterized
orbits. Based on data obtained with the STELLA robotic telescope
in Tenerife, an AIP facility jointly operated by AIP and IAC.
Title: Constraining the evolutionary state of the hot, massive
companion star and the wind-wind collision region in Eta Carinae
Authors: Gull, Theodore Raymond; Corcoran, Michael F.; Damineli,
Augusto; Groh, Jose; Hamaguchi, Kenji; Hillier, D. John; Madura,
Thomas I.; Owocki, Stanley P.; Richardson, Noel D.; Weigelt, Gerd
Bibcode: 2016hst..prop13395G
Altcode:
Our primary goal is to constrain the physical properties of Eta
Car's wind-wind collision region and the properties of Eta Car B,
the hot, very massive secondary companion that is hidden from our
view. We propose to do this by measuring the forbidden emission lines
in the extended, interacting wind structures resolved in the inner
1.5 arcseconds region. As the mass-loss structures evolve across the
5.54-year orbital period, we will selectively map their spatial and
velocity changes at critical phases using the spatial resolution of
HST and moderate spectral resolving power of the STIS to generate
spatial (2-D), velocity (1-D) data cubes of regions of critical
collisional densities. We will use these spatial-velocity data cubes
to drive ongoing 3-D models of the interacting winds, adding radiative
transfer. We will (A) strongly constrain the 3-D mass loss from the
system and (B) determine the properties of Eta Car B, the source of
FUV radiation and the driving wind creating the X-ray emitting cavity
out of the dominating wind of Eta Car A.
Title: Monte-Carlo radiative transfer simulation of the circumstellar
disk of the Herbig Ae star HD 144432
Authors: Chen, L.; Kreplin, A.; Weigelt, G.; Hofmann, K. -H.; Schertl,
D.; Malbet, F.; Massi, F.; Petrov, R.; Stee, Ph.
Bibcode: 2016A&A...586A..54C
Altcode: 2015arXiv151202276C
Context. Studies of pre-transitional disks, with a gap region between
the inner near-infrared-emitting region and the outer disk, are
important to improving our understanding of disk evolution and planet
formation.Previous infrared interferometric observations have shown
hints of a gap region in the protoplanetary disk around the Herbig Ae
star HD 144432.
Aims: We study the dust distribution around this
star with two-dimensional radiative transfer modeling.
Methods:
We compare the model predictions obtained via the Monte-Carlo radiative
transfer code RADMC-3D with infrared interferometric observations
and the spectral energy distribution of HD 144432.
Results:
The best-fit model that we found consists of an inner optically thin
component at 0.21-0.32 AU and an optically thick outer disk at 1.4-10
AU. We also found an alternative model in which the inner sub-AU region
consists of an optically thin and an optically thick component.
Conclusions: Our modeling suggests an optically thin component exists
in the inner sub-AU region, although an optically thick component may
coexist in the same region. Our modeling also suggests a gap-like
discontinuity in the disk of HD 144432. Based on observations
made with ESO telescopes at Paranal Observatory under program ID
083.D-0224(C) and 085.C-0126(A).
Title: Constraining the evolutionary state of the hot, massive
companion star and the wind-wind collision region in Eta Carinae
Authors: Gull, Theodore Raymond; Cherchneff, Isabelle; Corcoran,
Michael F.; Damineli, Augusto; Groh, Jose; Hamaguchi, Kenji; Hillier,
D. John; Icke, Vincent; Madura, Thomas I.; Owocki, Stanley P.;
Richardson, Noel D.; Weigelt, Gerd
Bibcode: 2016hst..prop12508G
Altcode:
Our primary goal is to constrain the physical properties of Eta
Car's wind-wind collision region and the properties of Eta Car B,
the hot, very massive secondary companion that is hidden from our
view. We propose to do this by measuring the forbidden emission lines
in the extended, interacting wind structures resolved in the inner
1.5 arcseconds region. As the mass-loss structures evolve across the
5.54-year orbital period, we will selectively map their spatial and
velocity changes at critical phases using the spatial resolution of
HST and moderate spectral resolving power of the STIS to generate
spatial {2-D}, velocity {1-D} data cubes of regions of critical
collisional densities. We will use these spatial-velocity data cubes
to drive ongoing 3-D models of the interacting winds, adding radiative
transfer. We will {A} strongly constrain the 3-D mass loss from the
system and {B} determine the properties of Eta Car B, the source of
FUV radiation and the driving wind creating the X-ray emitting cavity
out of the dominating wind of Eta Car A.
Title: Revealing the Complex Dynamics of the Atmospheres of Red
Supergiants with the Very Large Telescope Interferometer
Authors: Ohnaka, K.; Weigelt, G.; Hofmann, K. -H.; Schertl, D.
Bibcode: 2015Msngr.162...46O
Altcode:
Massive stars lose a significant fraction of their initial mass when
they evolve to red supergiants before they end their life in supernova
explosions. The mass loss greatly affects their final fate. However,
the mass loss from these dying supergiants is not yet understood
well. Here we present our efforts to spatially resolve the dynamics
of the atmospheres of red supergiants with the Very Large Telescope
Interferometer (VLTI) and the AMBER instrument to clarify the physical
mechanism behind the mass loss. The VLTI/AMBER's combination of
milliarcsecond spatial resolution and high spectral resolution allows
us to spatially resolve stellar atmospheres and extract the dynamical
information at each position over the star and the atmosphere — just
like observations of the Sun.
Title: High angular resolution at LBT
Authors: Conrad, A.; Arcidiacono, C.; Bertero, M.; Boccacci, P.;
Davies, A. G.; Defrere, D.; de Kleer, K.; De Pater, I.; Hinz, P.;
Hofmann, K. H.; La Camera, A.; Leisenring, J.; Kürster, M.; Rathbun,
J. A.; Schertl, D.; Skemer, A.; Skrutskie, M.; Spencer, J. R.; Veillet,
C.; Weigelt, G.; Woodward, C. E.
Bibcode: 2015AGUFM.P23D..08C
Altcode:
High angular resolution from ground-based observatories stands as a
key technology for advancing planetary science. In the window between
the angular resolution achievable with 8-10 meter class telescopes,
and the 23-to-40 meter giants of the future, LBT provides a glimpse
of what the next generation of instruments providing higher angular
resolution will provide. We present first ever resolved images of an
Io eruption site taken from the ground, images of Io's Loki Patera
taken with Fizeau imaging at the 22.8 meter LBT [Conrad, et al.,
AJ, 2015]. We will also present preliminary analysis of two data sets
acquired during the 2015 opposition: L-band fringes at Kurdalagon and an
occultation of Loki and Pele by Europa (see figure). The light curves
from this occultation will yield an order of magnitude improvement
in spatial resolution along the path of ingress and egress. We will
conclude by providing an overview of the overall benefit of recent
and future advances in angular resolution for planetary science.
Title: AMBER/VLTI high spectral resolution observations of the Brγ
emitting region in HD 98922. A compact disc wind launched from the
inner disc region
Authors: Caratti o Garatti, A.; Tambovtseva, L. V.; Garcia Lopez, R.;
Kraus, S.; Schertl, D.; Grinin, V. P.; Weigelt, G.; Hofmann, K. -H.;
Massi, F.; Lagarde, S.; Vannier, M.; Malbet, F.
Bibcode: 2015A&A...582A..44C
Altcode: 2015A&A...582A..44G; 2015arXiv150800798G
Context. High angular and spectral resolution observations can provide
us with fundamental clues to the complex circumstellar structure
of young stellar objects (YSOs) and to the physical processes taking
place close to these sources.
Aims: We analyse the main physical
parameters and the circumstellar environment of the young Herbig Be star
HD 98922.
Methods: We present AMBER/VLTI high spectral resolution
(R = 12 000) interferometric observations across the Brγ line,
accompanied by UVES high-resolution spectroscopy and SINFONI-AO assisted
near-infrared (NIR) integral field spectroscopic data. To interpret
our observations, we develop a magneto-centrifugally driven disc-wind
model.
Results: Our analysis of the UVES spectrum shows that HD
98922 is a young (~5 × 105 yr) Herbig Be star (SpT = B9V),
located at a distance of 440± 6050 pc, with a
mass accretion rate (Ṁacc) of ~(9 ± 3) × 10-7
M⊙ yr-1. SINFONI K-band AO-assisted imaging
shows a spatially resolved circumstellar disc-like region (~140 AU in
diameter) with asymmetric brightness distribution. Our AMBER/VLTI UT
observations indicate that the Brγ emitting region (ring-fit radius
~0.31 ± 0.04 AU) is smaller than the continuum emitting region (inner
dust radius ~0.7 ± 0.2 AU), showing significant non-zero V-shaped
differential phases (i.e. non S-shaped, as expected for a rotating
disc). The value of the continuum-corrected pure Brγ line visibility
at the longest baseline (89 m) is ~0.8 ± 0.1, i.e. the Brγ emitting
region is partially resolved. Our modelling suggests that the observed
Brγ line-emitting region mainly originates from a disc wind with a
half opening angle of 30°, and with a mass-loss rate (Ṁw)
of ~2 × 10-7 M⊙ yr-1. The observed
V-shaped differential phases are reliably reproduced by combining
a simple asymmetric continuum disc model with our Brγ disc-wind
model.
Conclusions: In conclusion, the Brγ emission of HD
98922 can be modelled with a disc wind that is able to approximately
reproduce all interferometric observations if we assume that the
intensity distribution of the dust continuum disc is asymmetric. Based on observations collected at the VLT (ESO Paranal, Chile) with
programmes 075.C-0637(A), 083.C-0236(A-D), 090.C-0192(A), 090.C-0378(A)
and 090.C-0371(A).Appendices are available in electronic form at http://www.aanda.org
Title: High resolution LBT imaging of Io and Jupiter
Authors: Conrad, A.; de Kleer, K.; Leisenring, J.; La Camera, A.;
Arcidiacono, C.; Bertero, M.; Boccacci, P.; Defrère, D.; de Pater,
I.; Hinz, P.; Hoffman, K. -H.; Kürster, M.; Rathbun, J.; Schertl,
D.; Skemer, A.; Skrutskie, M.; Spencer, J.; Veillet, C.; Weigelt,
G.; Woodward, C.
Bibcode: 2015EPSC...10..351C
Altcode:
We report here results from observing Io at high angular resolution,
∼32 mas at 4.8 μm, with LBT at two favorable oppositions as described
in our report given at the 2011 EPSC [1]. Analysis of datasets acquired
during the last two oppositions has yielded spatially resolved M-band
emission at Loki Patera [2], L-band fringes at an eruption site,
an occultation of Loki and Pele by Europa, and sufficient sub-earth
longitude (SEL) and parallactic angle coverage to produce a full disk
map.We summarize completed results for the first of these, and give
brief progress reports for the latter three. Finally, we provide plans
for imaging the full disk of Jupiter using the MCAO system which is
in its commissioning phase at LBT.
Title: AMBER-NACO aperture-synthesis imaging of the half-obscured
central star and the edge-on disk of the red giant L2
Puppis
Authors: Ohnaka, K.; Schertl, D.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2015A&A...581A.127O
Altcode: 2015arXiv150706668O
Aims: The red giant L2 Pup started a dimming event
in 1994, which is considered to be caused by the ejection of dust
clouds. We present near-IR aperture-synthesis imaging of L2
Pup achieved by combining data from VLT/NACO and the AMBER instrument of
the Very Large Telescope Interferometer (VLTI). Our aim is to spatially
resolve the innermost region of the circumstellar environment.
Methods: We carried out speckle interferometric observations at 2.27
μm with VLT/NACO and long-baseline interferometric observations
with VLTI/AMBER at 2.2-2.35 μm with baselines of 15-81 m. We also
extracted an 8.7 μm image from the mid-IR VLTI instrument MIDI.
Results: The diffraction-limited image obtained by bispectrum speckle
interferometry with NACO with a spatial resolution of 57 mas shows
an elongated component. The aperture-synthesis imaging combining
the NACO speckle data and AMBER data with a spatial resolution of
5.6 × 7.3 mas further resolves not only this elongated component,
but also the central star. The reconstructed image reveals that the
elongated component is a nearly edge-on disk with a size of ~180 ×
50 mas lying in the E-W direction, and furthermore, that the southern
hemisphere of the central star is severely obscured by the equatorial
dust lane of the disk. The angular size of the disk is consistent with
the distance that the dust clouds that were ejected at the onset of the
dimming event should have traveled by the time of our observations, if
we assume that the dust clouds moved radially. This implies that the
formation of the disk may be responsible for the dimming event. The
8.7 μm image with a spatial resolution of 220 mas extracted from
the MIDI data taken in 2004 (seven years before the AMBER and NACO
observations) shows an approximately spherical envelope without a
signature of the disk. This suggests that the mass loss before the
dimming event may have been spherical. Based on AMBER, NACO, and
MIDI observations made with the Very Large Telescope and Very Large
Telescope Interferometer of the European Southern Observatory. Program
ID: 074.D-0075(A), 074.D-0101(A), 074.D-0198(B), 088.D-0150(A/B),
and 288.D-5041(A). Appendices are available in electronic form at http://www.aanda.org
Title: The LEECH Exoplanet Imaging Survey. Further constraints on
the planet architecture of the HR 8799 system (Corrigendum)
Authors: Maire, A. -L.; Skemer, A. J.; Hinz, P. M.; Desidera, S.;
Esposito, S.; Gratton, R.; Marzari, F.; Skrutskie, M. F.; Biller,
B. A.; Defrère, D.; Bailey, V. P.; Leisenring, J. M.; Apai, D.;
Bonnefoy, M.; Brandner, W.; Buenzli, E.; Claudi, R. U.; Close,
L. M.; Crepp, J. R.; De Rosa, R. J.; Eisner, J. A.; Fortney, J. J.;
Henning, T.; Hofmann, K. -H.; Kopytova, T. G.; Males, J. R.; Mesa,
D.; Morzinski, K. M.; Oza, A.; Patience, J.; Pinna, E.; Rajan, A.;
Schertl, D.; Schlieder, J. E.; Su, K. Y. L.; Vaz, A.; Ward-Duong,
K.; Weigelt, G.; Woodward, C. E.
Bibcode: 2015A&A...579C...2M
Altcode:
The LBT is an international collaboration among institutions in
the United States, Italy and Germany. LBT Corporation partners are:
The University of Arizona on behalf of the Arizona university system;
Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft,
Germany, representing the Max-Planck Society, the Astrophysical
Institute Potsdam, and Heidelberg University; The Ohio State University,
and The Research Corporation, on behalf of The University of Notre Dame,
University of Minnesota, and University of Virginia.
Title: Investigating 2MASS J06593158-0405277: AN FUor Burst in a
Triple System?
Authors: Caratti o Garatti, A.; Garcia Lopez, R.; Ray, T. P.;
Eislöffel, J.; Stecklum, B.; Scholz, A.; Kraus, S.; Weigelt, G.;
Kreplin, A.; Shenavrin, V.
Bibcode: 2015ApJ...806L...4C
Altcode: 2015ApJ...806L...4G; 2015arXiv150503691G
FUor outbursts in young stellar objects are the most dramatic events
among episodic accretion phenomena. The origin of these bursts is not
clear: disk instabilities and/or disk perturbations by an external
body being the most viable hypotheses. Here, we report our Very Large
Telescope/SINFONI high angular resolution AO-assisted observations of
2MASS J06593158-0405277, which is undergoing a recently discovered
FUor outburst. Our observations reveal the presence of an extended
disk-like structure around the FUor, a very low-mass companion
(2MASS J06593158-0405277B) at ∼100 AU in projection, and, possibly,
a third closer companion at ∼11 AU. These sources appear to be
young, displaying accretion signatures. Assuming the components are
physically linked, 2MASS J06593158-0405277 would then be one of the
very few triple systems observed in FUors.
Title: Spatially Resolved M-band Emission from Io's Loki Patera-Fizeau
Imaging at the 22.8 m LBT
Authors: Conrad, Albert; de Kleer, Katherine; Leisenring, Jarron;
La Camera, Andrea; Arcidiacono, Carmelo; Bertero, Mario; Boccacci,
Patrizia; Defrère, Denis; de Pater, Imke; Hinz, Philip; Hofmann,
Karl-Heinz; Kürster, Martin; Rathbun, Julie; Schertl, Dieter; Skemer,
Andy; Skrutskie, Michael; Spencer, John; Veillet, Christian; Weigelt,
Gerd; Woodward, Charles E.
Bibcode: 2015AJ....149..175C
Altcode:
The Large Binocular Telescope Interferometer mid-infrared camera,
LMIRcam, imaged Io on the night of 2013 December 24 UT and detected
strong M-band (4.8 μm) thermal emission arising from Loki Patera. The
22.8 m baseline of the Large Binocular Telescope provides an angular
resolution of ∼32 mas (∼100 km at Io) resolving the Loki Patera
emission into two distinct maxima originating from different regions
within Loki’s horseshoe lava lake. This observation is consistent
with the presence of a high-temperature source observed in previous
studies combined with an independent peak arising from cooling crust
from recent resurfacing. The deconvolved images also reveal 15 other
emission sites on the visible hemisphere of Io including two previously
unidentified hot spots.
Title: Physical Properties of the Massive Magnetic Binary
θ1 Ori C Components
Authors: Balega, Yu. Yu.; Chentsov, E. L.; Rzaev, A. Kh.; Weigelt, G.
Bibcode: 2015ASPC..494...57B
Altcode:
Thirty spectroscopic measurements of radial velocities and twenty eight
interferometric observations of relative positions of the young massive
magnetic binary θ1 Ori C (HR 1895) components were used
to derive a combined 3D orbit. The total mass of the system is 45.5±
10.0M⊙. The masses of the components are M1
=33.5± 3.2M⊙ and M2 =12.0± 3.0M⊙
for a mass ratio q = 0.36±0.05. However, the accuracy of the combined
orbital parameters is rather low. The principal difficulty consists in
stochastic variations of absorption lines of the magnetic primary star,
caused by a clumpy structure of absorbing material in the plane of
the magnetic equator. In addition, weak and shallow lines of the fast
rotating secondary do not allow precise radial velocity estimation. We
believe that the continuation of θ1 Ori Cspectroscopic
monitoring will allow us to refine the orbital parameters over the
next few years.
Title: The LEECH Exoplanet Imaging Survey. Further constraints on
the planet architecture of the HR 8799 system
Authors: Maire, A. -L.; Skemer, A. J.; Hinz, P. M.; Desidera, S.;
Esposito, S.; Gratton, R.; Marzari, F.; Skrutskie, M. F.; Biller,
B. A.; Defrère, D.; Bailey, V. P.; Leisenring, J. M.; Apai, D.;
Bonnefoy, M.; Brandner, W.; Buenzli, E.; Claudi, R. U.; Close,
L. M.; Crepp, J. R.; De Rosa, R. J.; Eisner, J. A.; Fortney, J. J.;
Henning, T.; Hofmann, K. -H.; Kopytova, T. G.; Males, J. R.; Mesa,
D.; Morzinski, K. M.; Oza, A.; Patience, J.; Pinna, E.; Rajan, A.;
Schertl, D.; Schlieder, J. E.; Su, K. Y. L.; Vaz, A.; Ward-Duong,
K.; Weigelt, G.; Woodward, C. E.
Bibcode: 2015A&A...576A.133M
Altcode: 2014arXiv1412.6989M
Context. Astrometric monitoring of directly imaged exoplanets allows
the study of their orbital parameters and system architectures. Because
most directly imaged planets have long orbital periods (>20 AU),
accurate astrometry is challenging when based on data acquired on
timescales of a few years and usually with different instruments. The
LMIRCam camera on the Large Binocular Telescope is being used for the
LBT Exozodi Exoplanet Common Hunt (LEECH) survey to search for and
characterize young and adolescent exoplanets in L' band (3.8 μm),
including their system architectures.
Aims: We first aim to
provide a good astrometric calibration of LMIRCam. Then, we derive
new astrometry, test the predictions of the orbital model of 8:4:2:1
mean motion resonance proposed for the system, and perform new orbital
fitting of the HR 8799 bcde planets. We also present deep limits on
a putative fifth planet inside the known planets.
Methods:
We use observations of HR 8799 and the Θ1 Ori C field
obtained during the same run in October 2013.
Results: We first
characterize the distortion of LMIRCam. We determine a platescale and
a true north orientation for the images of 10.707 ± 0.012 mas/pix and
-0.430 ± 0.076°, respectively. The errors on the platescale and true
north orientation translate into astrometric accuracies at a separation
of 1'' of 1.1 mas and 1.3 mas, respectively. The measurements for
all planets agree within 3σ with a predicted ephemeris. The orbital
fitting based on the new astrometric measurements favors an architecture
for the planetary system based on 8:4:2:1 mean motion resonance. The
detection limits allow us to exclude a fifth planet slightly brighter
or more massive than HR 8799 b at the location of the 2:1 resonance
with HR 8799 e (~9.5 AU) and about twice as bright as HR 8799 cde
at the location of the 3:1 resonance with HR 8799 e (~7.5 AU). The LBT is an international collaboration among institutions in
the United States, Italy, and Germany. LBT Corporation partners are:
The University of Arizona on behalf of the Arizona university system;
Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft,
Germany, representing the Max-Planck Society, the Astrophysical
Institute Potsdam, and Heidelberg University; The Ohio State University,
and The Research Corporation, on behalf of The University of Notre Dame,
University of Minnesota, and University of Virginia.
Title: Probing the accretion-ejection connection with VLTI/AMBER. High
spectral resolution observations of the Herbig Ae star HD 163296
Authors: Garcia Lopez, R.; Tambovtseva, L. V.; Schertl, D.; Grinin,
V. P.; Hofmann, K. -H.; Weigelt, G.; Caratti o Garatti, A.
Bibcode: 2015A&A...576A..84G
Altcode: 2015arXiv150203027G
Context. Accretion and ejection are tightly connected and represent
the fundamental mechanisms regulating star formation. However, the
exact physical processes involved are not yet fully understood.
Aims: We present high angular and spectral resolution observations
of the Brγ emitting region in the Herbig Ae star HD 163296 (MWC 275)
in order to probe the origin of this line and constrain the physical
processes taking place at sub-AU scales in the circumstellar region.
Methods: By means of VLTI-AMBER observations at high spectral
resolution (R ~ 12 000), we studied interferometric visibilities,
wavelength-differential phases, and closure phases across the Brγ
line of HD 163296. To constrain the physical origin of the Brγ line
in Herbig Ae stars, all the interferometric observables were compared
with the predictions of a line radiative transfer disc wind model.
Results: The measured visibilities clearly increase within the
Brγ line, indicating that the Brγ emitting region is more compact
than the continuum. By fitting a geometric Gaussian model to the
continuum-corrected Brγ visibilities, we derived a compact radius of
the Brγ emitting region of ~0.07 ± 0.02 AU (Gaussian half width at
half maximum; or a ring-fit radius of ~0.08 ± 0.02 AU). To interpret
the observations, we developed a magneto-centrifugally driven disc wind
model. Our best disc wind model is able to reproduce, within the errors,
all the interferometric observables and it predicts a launching region
with an outer radius of ~0.04 AU. However, the intensity distribution
of the entire disc wind emitting region extends up to ~0.16 AU.
Conclusions: Our observations, along with a detailed modelling of
the Brγ emitting region, suggest that most of the Brγ emission in
HD 163296 originates from a disc wind with a launching region that is
over five times more compact than previous estimates of the continuum
dust rim radius. Appendices are available in electronic form at http://www.aanda.orgBased
on observations collected at the European Southern Observatory Paranal,
Chile (ESO programme 089.C-0443(A)).
Title: On the changes in the physical properties of the ionized
region around the Weigelt structures in η Carinae over the 5.54-yr
spectroscopic cycle
Authors: Teodoro, Mairan; Gull, Theodore R.; Bautista, Manuel; Hillier,
Desmond John; Weigelt, Gerd
Bibcode: 2015AAS...22534421T
Altcode:
We present HST/STIS observations and analysis of two prominent
nebular structures around the central source of η Carinae, the
so-called Weigelt blobs C and D. The former is brighter than the
latter for emission lines from intermediate or high ionization
potential ions. The brightness of lines from intermediate and high
ionization potential ions significantly decreases at phases around
periastron. We do not see conspicuous changes in the brightness of
lines from low ionization potential ions over the orbital period. Line
ratios suggest that the total extinction towards the Weigelt structures
is AV=2.0. Weigelt C and D are characterized by an electron
density of 106.9 cm-3 that does not significantly
change throughout the orbital cycle. The electron temperature varies
from 5500 K (around periastron) to 7200 K (around apastron). The
relative changes in the brightness of He0 lines are well
reproduced by the variations in the electron temperature alone. We found
that, at phases around periastron, the electron temperature seems to be
higher for Weigelt C than that of D. The Weigelt structures are located
close to the Homunculus equatorial plane, at a distance of about 1240
AU from the central source. From the analysis of proper motion and age,
the Weigelt complex can be associated with the equatorial structure
called `Butterfly Nebula' surrounding the central binary system.
Title: The interacting winds of Eta Carinae: Observed forbidden line
changes and the Forbidden Blue(-Shifted) Crab
Authors: Gull, Theodore R.; Madura, Thomas; Corcoran, Michael F.;
Teodoro, Mairan; Richardson, Noel; Hamaguchi, Kenji; Groh, Jose H.;
Hillier, Desmond John; Damineli, Augusto; Weigelt, Gerd
Bibcode: 2015AAS...22534416G
Altcode:
The massive binary, Eta Carinae (EC), produces such massive winds
that strong forbidden line emission of singly- and doubly-ionized
iron traces wind-wind interactions from the current cycle plus fossil
interactions from one, two and three 5.54-year cycles ago.With an
eccentricity of >0.9, the >90 solar mass primary (EC-A) and
>30 solar mass secondary (EC-B) approach to within 1.5 AU during
periastron and recede to nearly 30 AU across apastron. The wind-wind
structures move outward driven by the 420 km/s primary wind interacting
with the ~3000 km/s secondary wind yielding partially-accelerated
compressed primary wind shells that are excited by mid-UV from EC-A
and in limited lines of sight, FUV from EC-B.These structures are
spectroscopically and spatially resolved by HST's Space Telescope
Imaging Spectrograph. At critical binary phases, we have mapped
the central 2'x2' region in the light of [Fe III] and [Fe II] with
spatial resolution of 0.12' and velocity resolution of 40 km/s.1) The
bulk of forbidden emission originates from the large cavity northwest
of EC and is due to ionization of massive ejecta from the 1840s and
1890s eruptions. The brightest clumps are the Weigelt Blobs C and D,
but there are additionally multiple, fainter emission clumps. Weigelt
B appears to have faded.2) Three concentric, red-shifted [FeII] arcs
expand at ~470 km/s excited by mid-UV of EC-A.3) The structure of
primarily blue-shifted [Fe III] emission resembles a Maryland Blue
Crab. The claws appear at the early stages of the high-excitation
recovery from the periastron passage, expand at radial velocities
exceeding the primary wind terminal velocity, 420 km/s and fade as the
binary system approaches periastron with the primary wind enveloping
the FUV radiation from EC-B.4) All [Fe III] emission faded by late June
2014 and disappeared by August 2, 2014, the beginning of periastron
passage.Comparisons to HST/STIS observations between 1998 to 2004.3
indicate long-term fading of [Fe II]. Likewise, Na D emission has
faded. 3D hydro/radiative models suggest a small decrease (< factor
of 2) in primary mass loss rate to be the cause.
Title: High Resolution Imaging of Io's Volcanoes with LBTI
Authors: Conrad, Al; Leisenring, Jarron; de Kleer, Katherine; Skemer,
Andy; Hinz, Philip; Skrutskie, Michael; Veillet, Christian; de Pater,
Imke; Bertero, Mario; Boccacci, Patrizia; Defrère, Denis; Hofmann,
Karl-Heinz; La Camera, Andrea; Schertl, Dieter; Spencer, John; Weigelt,
Gerd; Woodward, Charles E.
Bibcode: 2014DPS....4641818C
Altcode:
The Large Binocular Telescope (LBT), located on Mount Graham in eastern
Arizona, employs two 8.4 meter mirrors with a 14.4 center-to-center
separation on a common mount. Coherent combination of these two
AO-corrected apertures via the LBT Interferometer (LBTI) produces
Fizeau interferometric images with spatial resolution consistent with
the diffraction limit of the 22.8-meter aperture. In particular LBTI
resolves thermal signatures (i.e., features observed at M-band) on
the surface of Io down to ~150 kilometers; a two-fold improvement
over what has previously been possible from the ground. We show
images collected with LBTI on December 24, 2013, in which Loki's
shape is clearly resolved and at least fourteen additional volcanic
hot spots are detected.We analyze three locations in the LBTI data:
emission features within Loki Patera, the area near Rarog and Heno
Patarae, and a hot spot seen in the Colchis Regio.For Loki Patera,
we interpret spatially resolved variation in the emission within
that region. With M-band resolution that is comparable to what has
previously been achievable only at K-band, we compare localized emission
features with what has been seen in earlier observations at shorter
wavelengths.Thermal emission from activity at Rarog and Heno Patarae
is well resolved in these images, while a third hot-spot in the nearby
Lerna Regio is also clearly resolved. This area is of special interest
since it was the site of two high-effusion outbursts on August 15th,
2013 [de Pater et al. (2014) Icarus].Lastly, we explore a hot-spot
seen in the Colchis Regio that may be a remnant of a violent outburst
detected on August 29th, 2013 [de Kleer et al. (2014) Icarus].
Title: An Overview of the MATISSE Instrument — Science, Concept
and Current Status
Authors: Lopez, B.; Lagarde, S.; Jaffe, W.; Petrov, R.; Schöller,
M.; Antonelli, P.; Beckmann, U.; Berio, P.; Bettonvil, F.;
Glindemann, A.; Gonzalez, J. -C.; Graser, U.; Hofmann, K. -H.;
Millour, F.; Robbe-Dubois, S.; Venema, L.; Wolf, S.; Henning, T.;
Lanz, T.; Weigelt, G.; Agocs, T.; Bailet, C.; Bresson, Y.; Bristow,
P.; Dugué, M.; Heininger, M.; Kroes, G.; Laun, W.; Lehmitz, M.;
Neumann, U.; Augereau, J. -C.; Avila, G.; Behrend, J.; van Belle, G.;
Berger, J. -P.; van Boekel, R.; Bonhomme, S.; Bourget, P.; Brast,
R.; Clausse, J. -M.; Connot, C.; Conzelmann, R.; Cruzalèbes, P.;
Csepany, G.; Danchi, W.; Delbo, M.; Delplancke, F.; Dominik, C.;
van Duin, A.; Elswijk, E.; Fantei, Y.; Finger, G.; Gabasch, A.; Gay,
J.; Girard, P.; Girault, V.; Gitton, P.; Glazenborg, A.; Gonté, F.;
Guitton, F.; Guniat, S.; De Haan, M.; Haguenauer, P.; Hanenburg, H.;
Hogerheijde, M.; ter Horst, R.; Hron, J.; Hugues, Y.; Hummel, C.;
Idserda, J.; Ives, D.; Jakob, G.; Jasko, A.; Jolley, P.; Kiraly,
S.; Köhler, R.; Kragt, J.; Kroener, T.; Kuindersma, S.; Labadie,
L.; Leinert, C.; Le Poole, R.; Lizon, J. -L.; Lucuix, C.; Marcotto,
A.; Martinache, F.; Martinot-Lagarde, G.; Mathar, R.; Matter, A.;
Mauclert, N.; Mehrgan, L.; Meilland, A.; Meisenheimer, K.; Meisner,
J.; Mellein, M.; Menardi, S.; Menut, J. -L.; Merand, A.; Morel, S.;
Mosoni, L.; Navarro, R.; Nussbaum, E.; Ottogalli, S.; Palsa, R.;
Panduro, J.; Pantin, E.; Parra, T.; Percheron, I.; Duc, T. P.; Pott,
J. -U.; Pozna, E.; Przygodda, F.; Rabbia, Y.; Richichi, A.; Rigal, F.;
Roelfsema, R.; Rupprecht, G.; Schertl, D.; Schmidt, C.; Schuhler, N.;
Schuil, M.; Spang, A.; Stegmeier, J.; Thiam, L.; Tromp, N.; Vakili,
F.; Vannier, M.; Wagner, K.; Woillez, J.
Bibcode: 2014Msngr.157....5L
Altcode:
MATISSE, a second generation Very Large Telescope Interferometer (VLTI)
instrument, is a combined imager and spectrograph for interferometry
in the 3-5 μm region (L- and M-bands) and the 8-13 μm window
(N-band). MATISSE builds on the experience gained with the VLTI's
first generation instruments. It employs multi-axial beam combination
while also providing wavelength differential visibility and phase,
and closure-phase aperture-synthesis imaging at a range of spectral
resolutions. MATISSE is designed for a broad range of science goals,
and its potential for studies of the discs around young stars and
active galactic nuclei are highlighted. The instrument concept and
operating modes are described; construction is in progress towards
installation at the VLTI in 2016.
Title: Study of the sub-AU disk of the Herbig B[e] star HD 85567
with near-infrared interferometry
Authors: Vural, J.; Kraus, S.; Kreplin, A.; Weigelt, G.; Fossat, E.;
Massi, F.; Perraut, K.; Vakili, F.
Bibcode: 2014A&A...569A..25V
Altcode: 2014arXiv1407.8190V
Context. The structure of the inner disk of Herbig Be stars is not
well understood. The continuum disks of several Herbig Be stars have
inner radii that are smaller than predicted by models of irradiated
disks with optically thin holes.
Aims: We study the size of
the inner disk of the Herbig B[e] star HD 85567 and compare the model
radii with the radius suggested by the size-luminosity relation.
Methods: The object was observed with the AMBER instrument of the
Very Large Telescope Interferometer. We obtained K-band visibilities
and closure phases. These measurements are interpreted with geometric
models and temperature-gradient models.
Results: Using several
types of geometric star-disk and star-disk-halo models, we derived
inner ring-fit radii in the K band that are in the range of 0.8-1.6
AU. Additional temperature-gradient modeling resulted in an extended
disk with an inner radius of 0.67+0.51-0.21
AU, a high inner temperature of 2200+750-350 K,
and a disk inclination of 53+15-11 °.
Conclusions: The derived geometric ring-fit radii are approximately 3-5
times smaller than that predicted by the size-luminosity relation. The
small geometric and temperature-gradient radii suggest optically thick
gaseous material that absorbs stellar radiation inside the dust disk. Based on observations made with ESO telescopes at the La Silla
Paranal Observatory under program IDs 080.C-0541(C), 082.C-0893(A),
084.C-0848(B).Appendix A is available in electronic form at http://www.aanda.org
Title: He II 4686 in eta Carinae: no significant changes between
2009.0 and 2014.6
Authors: Teodoro, Mairan; Heathcote, Bernard; Richardson, Noel;
Luckas, Paul; Walter, Frederick; Prates, Rodrigo; Hickel, Gabriel;
Coimbra, Adriano M.; Navarete, Felipe; Locke, Malcolm; Bohlsen, Terry;
Damineli, Augusto; Jablonski, Francisco; Henrique, William; Powles,
Jonathan; West, Julian; Andrade, Thiago A.; Fernandez-Lajus, Eduardo;
Gull, Theodore; Corcoran, Michael F.; Groh, Jose H.; Hamaguchi, Kenji;
Madura, Thomas; St-Jean, Lucas; Weigelt, Gerd
Bibcode: 2014ATel.6464....1T
Altcode:
We are conducting a multi-observatory campaign focused on the monitoring
of He II 4686 emission across the periastron event of eta Carinae. The
behavior of the equivalent width of the He II 4686 emission line across
the 2014.6 event is similar to that observed in 2009.0.
Title: The stability of the He II 4686 line emission across periastron
passages in eta Carinae
Authors: Teodoro, Mairan; Heathcote, Bernard; Richardson, Noel; Prates,
Rodrigo; Damineli, Augusto; Hickel, Gabriel; Bohlsen, Terry; Luckas,
Paul; Locke, Malcolm; Navarete, Felipe; West, Julian; Andrade, Thiago
A.; Coimbra, Adriano M.; Fernandez-Lajus, Eduardo; Gull, Theodore;
Jablonski, Francisco; Corcoran, Michael F.; Groh, Jose H.; Hamaguchi,
Kenji; Madura, Thomas; St-Jean, Lucas; Weigelt, Gerd
Bibcode: 2014ATel.6380....1T
Altcode:
Preliminary analysis of data from the international campaign to
monitor eta Carinae through the 2014 event shows that, as expected,
the equivalent width of the He II 4686 emission line has reached its
minimum strength on JD=2456870.8 (August 01 2014).
Title: HD 139614: the interferometric case for a group-Ib
pre-transitional young disk
Authors: Labadie, Lucas; Matter, Alexis; Kreplin, Alexander;
Lopez, Bruno; Wolf, Sebastian; Weigelt, Gerd; Ertel, Steve; Berger,
Jean-Philippe; Pott, Jorg-Uwe; Danchi, William C.
Bibcode: 2014SPIE.9146E..2TL
Altcode: 2014arXiv1408.3876L
The Herbig Ae star HD 139614 is a group-Ib object, which featureless
SED indicates disk flaring and a possible pre-transitional evolutionary
stage. We present mid- and near-IR interferometric results collected
with MIDI, AMBER and PIONIER with the aim of constraining the spatial
structure of the 0.1-10 AU disk region and assess its possible
multi-component structure. A two-component disk model composed of an
optically thin 2-AU wide inner disk and an outer temperature-gradient
disk starting at 5.6 AU reproduces well the observations. This is
an additional argument to the idea that group-I HAeBe inner disks
could be already in the disk-clearing transient stage. HD 139614 will
become a prime target for mid-IR interferometric imaging with the
second-generation instrument MATISSE of the VLTI.
Title: The LINC-NIRVANA high resolution imager: challenges from the
lab to first light
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2014SPIE.9147E..1MH
Altcode:
We present an update on LINC-NIRVANA (LN), an innovative,
high-resolution infrared imager for the Large Binocular Telescope
(LBT). LN uses Multi-Conjugate Adaptive Optics (MCAO) for
high-sky-coverage diffraction-limited imagery and interferometric
beam combination. The last two years have seen both successes and
challenges. On the one hand, final integration is proceeding well in
the lab. We also achieved First Light at the LBT with the Pathfinder
experiment. On the other hand, funding constraints have forced a
significant re-planning of the overall instrument implementation. This
paper presents our progress and plans for bringing the instrument
online at the telescope.
Title: A low-noise HAWAII detector system and new cold optics for
the CLASSIC/CLIMB beam combiner instrument of the CHARA array
Authors: Beckmann, Udo; Connot, Claus; Heininger, Matthias; Hofmann,
Karl-Heinz; Nußbaum, Eddy; Schertl, Dieter; Solscheid, Walter;
ten Brummelaar, Theo; Turner, Nils; Weigelt, Gerd
Bibcode: 2014SPIE.9146E..1WB
Altcode:
As part of a new collaboration between CHARA and the Max Planck
Institute for Radio Astronomy, we have developed a new detector system
for the CLASSIC/CLIMB beam combiner of the CHARA Array. This detector
is based on the Rockwell HAWAII-1 HgCdTe focal plane array and has
lower readout noise (∼5 electrons) than the current PICNIC based
system. Presently, CLASSIC/CLIMB observations at different wavelength
bands can be made only successively by selecting individual filters
in a filter wheel. Therefore, another upgrade goal is to install a
non-deviating prism in order to image the H- and K'-band light onto
separate detector pixels and to simultaneously observe in the H and K'
bands. The detector control electronics were built at the Max Planck
Institute for Radio Astronomy. The goal was to achieve the lowest
possible readout noise and electronic pick-up noise. The detector
readout noise can be significantly reduced by the following approach:
First, the analog detector output signal is processed by a moving
boxcar filter consisting of an analog approximation of a finite impulse
response filter with a response time adapted to the 10 MHz sample rate
of an analog-to-digital converter. Second, a digital filter averages
up to 1024 samples for each addressed pixel. This hybrid (analog plus
digital) filter approach gives a unique flexibility of a programmable
bandwidth for optimum noise reduction.
Title: High contrast imaging at the LBT: the LEECH exoplanet imaging
survey
Authors: Skemer, Andrew J.; Hinz, Philip; Esposito, Simone; Skrutskie,
Michael F.; Defrère, Denis; Bailey, Vanessa; Leisenring, Jarron;
Apai, Daniel; Biller, Beth; Bonnefoy, Mickaël.; Brandner, Wolfgang;
Buenzli, Esther; Close, Laird; Crepp, Justin; De Rosa, Robert J.;
Desidera, Silvano; Eisner, Josh; Fortney, Jonathan; Henning, Thomas;
Hofmann, Karl-Heinz; Kopytova, Taisiya; Maire, Anne-Lise; Males, Jared
R.; Millan-Gabet, Rafael; Morzinski, Katie; Oza, Apurva; Patience,
Jenny; Rajan, Abhijith; Rieke, George; Schertl, Dieter; Schlieder,
Joshua; Su, Kate; Vaz, Amali; Ward-Duong, Kimberly; Weigelt, Gerd;
Woodward, Charles E.; Zimmerman, Neil
Bibcode: 2014SPIE.9148E..0LS
Altcode: 2014arXiv1407.2876S
In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey
began its ~130-night campaign from the Large Binocular Telescope
(LBT) atop Mt Graham, Arizona. This survey benefits from the many
technological achievements of the LBT, including two 8.4-meter mirrors
on a single fixed mount, dual adaptive secondary mirrors for high
Strehl performance, and a cold beam combiner to dramatically reduce the
telescope's overall background emissivity. LEECH neatly complements
other high-contrast planet imaging efforts by observing stars at L'
(3.8 μm), as opposed to the shorter wavelength near-infrared bands
(1-2.4 μm) of other surveys. This portion of the spectrum offers
deep mass sensitivity, especially around nearby adolescent (~0.1-1
Gyr) stars. LEECH's contrast is competitive with other extreme
adaptive optics systems, while providing an alternative survey
strategy. Additionally, LEECH is characterizing known exoplanetary
systems with observations from 3-5μm in preparation for JWST.
Title: MATISSE status report and science forecast
Authors: Lopez, B.; Lagarde, S.; Jaffe, W.; Petrov, R.; Schöller,
M.; Antonelli, P.; Beckman, U.; Bério, Ph.; Bettonvil, F.; Graser,
U.; Millour, F.; Robbe-Dubois, S.; Venema, L.; Wolf, S.; Bristow, P.;
Glindemann, A.; Gonzalez, J. -C.; Lanz, Th.; Henning, T.; Weigelt,
G.; Agócs, T.; Augereau, J. -C.; Ávila, G.; Bailet, C.; Behrend,
J.; Berger, J. -P.; von Boekel, Roy; Bonhomme, S.; Bourget, P.; Brast,
R.; Bresson, Y.; Clausse, J. M.; Chesneau, O.; Csépány, G.; Connot,
C.; Crida, A.; Danchi, W. C.; Delbo, M.; Delplancke, F.; Dominik, C.;
Dugué, M.; Elswijk, E.; Fanteï, Y.; Finger, G.; Gabasch, A.; Girard,
P.; Girault, V.; Gitton, P.; Glazenborg, A.; Gonté, F.; Guitton, F.;
Guniat, S.; De Haan, M.; Haguenauer, P.; Hanenburg, H.; Heininger, M.;
Hofmann, K. -H.; Hogerheijde, M.; ter Horst, R.; Hron, J.; Hughes, Y.;
Ives, D.; Jakob, G.; Jaskó, A.; Jolley, P.; Kragt, J.; Köhler, R.;
Kroener, T.; Kroes, G.; Labadie, L.; Laun, W.; Lehmitz, M.; Leinert,
Ch.; Lizon, J. L.; Lucuix, Ch.; Marcotto, A.; Martinache, F.; Matter,
A.; Martinot-Lagarde, G.; Mauclert, N.; Mehrgan, L.; Meilland, A.;
Mellein, M.; Ménardi, S.; Menut, J. L.; Meisenheimer, K.; Morel,
S.; Mosoni, L.; Navarro, R.; Neumann, U.; Nussbaum, E.; Ottogalli,
S.; Palsa, R.; Panduro, J.; Pantin, E.; Percheron, I.; Duc, T. Phan;
Pott, J. -U.; Pozna, Eszter; Przygodda, F.; Richichi, A.; Rigal,
F.; Rupprecht, G.; Schertl, D.; Stegmeier, J.; Thiam, L.; Tromp, N.;
Vannier, M.; Vakili, F.; van Belle, G.; Wagner, K.; Woillez, J.
Bibcode: 2014SPIE.9146E..0ML
Altcode:
MATISSE is the mid-infrared spectrograph and imager for the Very Large
Telescope Interferometer (VLTI) at Paranal. This second generation
interferometry instrument will open new avenues in the exploration
of our Universe. Mid-infrared interferometry with MATISSE will allow
significant advances in various fundamental research fields: studies
of disks around young stellar objects where planets form and evolve,
surface structures and mass loss of stars in late evolutionary stages,
and the environments of black holes in active galactic nuclei. MATISSE
is a unique instrument. As a first breakthrough it will enlarge the
spectral domain used by optical interferometry by offering the L
& M bands in addition to the N band, opening a wide wavelength
domain, ranging from 2.8 to 13 μm on angular scales of 3 mas (L/M
band) / 10 mas (N band). As a second breakthrough, it will allow
mid-infrared imaging - closure-phase aperture-synthesis imaging -
with up to four Unit Telescopes (UT) or Auxiliary Telescopes (AT)
of the VLTI. MATISSE will offer various ranges of spectral resolution
between R~30 to ~5000. In this article, we present some of the main
science objectives that have driven the instrument design. We introduce
the physical concept of MATISSE including a description of the signal
on the detectors and an evaluation of the expected performance and
discuss the project status. The operations concept will be detailed in
a more specific future article, illustrating the observing templates
operating the instrument, the data reduction and analysis, and the
image reconstruction software.
Title: The 2014 interferometric imaging beauty contest
Authors: Monnier, John D.; Berger, Jean-Philippe; Le Bouquin,
Jean-Baptiste; Tuthill, Peter G.; Wittkowski, Markus; Grellmann,
Rebekka; Müller, André; Renganswany, Sridhar; Hummel, Christian;
Hofmann, Karl-Heinz; Schertl, Dieter; Weigelt, Gerd; Young, John;
Buscher, David; Sanchez-Bermudez, Joel; Alberdi, Antxon; Schoedel,
Rainer; Köhler, Rainer; Soulez, Ferréol; Thiébaut, Éric; Kluska,
Jacques; Malbet, Fabien; Duvert, Gilles; Kraus, Stefan; Kloppenborg,
Brian K.; Baron, Fabien; de Wit, Willem-Jan; Rivinius, Thomas;
Merand, Antoine
Bibcode: 2014SPIE.9146E..1QM
Altcode:
Here we present the results of the 6th biennial optical interferometry
imaging beauty contest. Taking advantage of a unique opportunity,
the red supergiant VY CMa and the Mira variable R Car were observed
in the astronomical H-band with three 4-telescope configurations of
the VLTI-AT array using the PIONIER instrument. The community was
invited to participate in the subsequent image reconstruction and
interpretation phases of the project. Ten groups submitted entries to
the beauty contest, and we found reasonable consistency between images
obtained from independent workers using quite different algorithms. We
also found that significant differences existed between the submitted
images, much greater than in past beauty contests that were all based on
simulated data. A novel crowd-sourcing" method allowed consensus median
images to be constructed, filtering likely artifacts and retaining
real features." We definitively detect strong spots on the surfaces
of both stars as well as distinct circumstellar shells of emission
(likely water/CO) around R Car. In a close contest, Joel Sanchez
(IAA-CSIC/Spain) was named the winner of the 2014 interferometric
imaging beauty contest. This process has shown that new comers" can use
publicly-available imaging software to interpret VLTI/PIONIER imaging
data, as long as sufficient observations are taken to have complete uv
coverage { a luxury that is often missing. We urge proposers to request
adequate observing nights to collect sufficient data for imaging and for
time allocation committees to recognise the importance of uv coverage
for reliable interpretation of interferometric data. We believe that
the result of the proposed broad international project will contribute
to inspiring trust in the image reconstruction processes in optical
interferometry.
Title: The LINC-NIRVANA Fizeau interferometric imager: final lab
integration, first light experiments and challenges
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2014SPIE.9146E..0IH
Altcode:
LINC-NIRVANA (LN) is an innovative Fizeau interferometric imager
for the Large Binocular Telescope (LBT). LN uses Multi-Conjugate
Adaptive Optics (MCAO) for high-sky-coverage single-eye imagery
and interferometric beam combination. The last two years have seen
both successes and challenges. On the one hand, final integration is
proceeding well in the lab. We also achieved First Light at the LBT
with the Pathfinder experiment. On the other hand, funding constraints
have forced a significant re-planning of the overall instrument
implementation. These laboratory, observatory, and financial "events"
provide lessons for builders of complex interferometric instruments
on large telescopes. This paper presents our progress and plans for
bringing the instrument online at the telescope.
Title: Fizeau interferometric imaging of Io volcanism with
LBTI/LMIRcam
Authors: Leisenring, J. M.; Hinz, P. M.; Skrutskie, M.; Skemer, A.;
Woodward, C. E.; Veillet, C.; Arcidiacono, C.; Bailey, V.; Bertero,
M.; Boccacci, P.; Conrad, A.; de Kleer, K.; de Pater, I.; Defrère,
D.; Hill, J.; Hofmann, K. -H.; Kaltenegger, L.; La Camera, A.; Nelson,
M. J.; Schertl, D.; Spencer, J.; Weigelt, G.; Wilson, J. C.
Bibcode: 2014SPIE.9146E..2SL
Altcode:
The Large Binocular Telescope (LBT) houses two 8.4-meter mirrors
separated by 14.4 meters on a common mount. Coherent combination of
these two AO-corrected apertures via the LBT Interferometer (LBTI)
produces Fizeau interferometric images with a spatial resolution
equivalent to that of a 22.8-meter telescope and the light- gathering
power of single 11.8-meter mirror. Capitalizing on these unique
capabilities, we used LBTI/LMIRcam to image thermal radiation from
volcanic activity on the surface of Io at M-Band (4.8 μm) over a range
of parallactic angles. At the distance of Io, the M-Band resolution
of the interferometric baseline corresponds to a physical distance of
~135 km, enabling high-resolution monitoring of Io volcanism such as
ares and outbursts inaccessible from other ground-based telescopes
operating in this wavelength regime. Two deconvolution routines are
used to recover the full spatial resolution of the combined images,
resolving at least sixteen known volcanic hot spots. Coupling these
observations with advanced image reconstruction algorithms demonstrates
the versatility of Fizeau interferometry and realizes the LBT as the
first in a series of extremely large telescopes.
Title: An image reconstruction method (IRBis) for optical/infrared
interferometry
Authors: Hofmann, K. -H.; Weigelt, G.; Schertl, D.
Bibcode: 2014A&A...565A..48H
Altcode:
Aims: We present an image reconstruction method for
optical/infrared long-baseline interferometry called IRBis (image
reconstruction software using the bispectrum). We describe the theory
and present applications to computer-simulated interferograms.
Methods: The IRBis method can reconstruct an image from measured
visibilities and closure phases. The applied optimization routine ASA_CG
is based on conjugate gradients. The method allows the user to implement
different regularizers, apply residual ratios as an additional metric
for goodness-of-fit, and use previous iteration results as a prior to
force convergence.
Results: We present the theory of the IRBis
method and several applications of the method to computer-simulated
interferograms. The image reconstruction results show the dependence
of the reconstructed image on the noise in the interferograms (e.g.,
for ten electron read-out noise and 139 to 1219 detected photons per
interferogram), the regularization method, the angular resolution,
and the reconstruction parameters applied. Furthermore, we present
the IRBis reconstructions submitted to the interferometric imaging
beauty contest 2012 initiated by the IAU Working Group on Optical/IR
Interferometry and describe the performed data processing steps.
Title: The inner circumstellar disk of the UX Orionis star V1026
Scorpii
Authors: Vural, J.; Kreplin, A.; Kishimoto, M.; Weigelt, G.; Hofmann,
K. -H.; Kraus, S.; Schertl, D.; Dugué, M.; Duvert, G.; Lagarde, S.;
Massi, F.
Bibcode: 2014A&A...564A.118V
Altcode: 2014arXiv1403.4941V
Context. The UX Ori type variables (named after the prototype of
their class) are intermediate-mass pre-main sequence objects. One of
the most likely causes of their variability is the obscuration of the
central star by orbiting dust clouds.
Aims: We investigate the
structure of the circumstellar environment of the UX Ori star V1026
Sco (HD 142666) and test whether the disk inclination is large enough
to explain the UX Ori variability.
Methods: We observed the
object in the low-resolution mode of the near-infrared interferometric
VLTI/AMBER instrument and derived H- and K-band visibilities and
closure phases. We modeled our AMBER observations, published Keck
Interferometer observations, archival MIDI/VLTI visibilities, and the
spectral energy distribution using geometric and temperature-gradient
models.
Results: Employing a geometric inclined-ring disk
model, we find a ring radius of 0.15 ± 0.06 AU in the H band and
0.18 ± 0.06 AU in the K band. The best-fit temperature-gradient
model consists of a star and two concentric, ring-shaped disks. The
inner disk has a temperature of 1257+133-53
K at the inner rim and extends from 0.19 ± 0.01 AU to 0.23 ± 0.02
AU. The outer disk begins at 1.35+0.19-0.20
AU and has an inner temperature of 334+35-17
K. The derived inclination of 48.6+2.9-3.6°
approximately agrees with the inclination derived with the geometric
model (49 ± 5° in the K band and 50 ± 11° in the H band). The
position angle of the fitted geometric and temperature-gradient
models are 163 ± 9° (K band; 179 ± 17° in the H band) and
169.3+4.2-6.7°, respectively.
Conclusions:
The narrow width of the inner ring-shaped model disk and the disk
gap might be an indication for a puffed-up inner rim shadowing outer
parts of the disk. The intermediate inclination of ~50° is consistent
with models of UX Ori objects where dust clouds in the inclined disk
obscure the central star. Based on observations made with ESO
telescopes at the La Silla Paranal Observatory under programme IDs
083.D-0224(C), 083.C-0236(A), 087.C-0013(A) and 073.A-9014(A).Member
of the International Max Planck Research School (IMPRS) for Astronomy
and Astrophysics at the Universities of Bonn and Cologne.
Title: Milliarcsecond imaging of clumpy dust clouds in the red giant
L2 Pup with the Very Large Telescope Interferometer
Authors: Ohnaka, K.; Schertl, D.; Hofmann, K. H.; Weigelt, G.
Bibcode: 2014apn6.confE..65O
Altcode:
Despite its importance in mass loss, the dust formation in AGB
stars is not yet understood well. There is growing evidence that
the dust envelopes of AGB stars are much more complex--clumpy and/or
bipolar--than spherically expanding shells. The non-spherical structures
emerging in AGB stars may be the seed of asymmetry in planetary
nebulae. However, direct observations of the clumpy dust cloud formation
close to the star is difficult, because we need milliarcsecond spatial
resolution. We present milliarcsecond resolution near-IR imaging of the
bright, nearby M giant L2 Pup. The 2.2 micron image taken with VLT/NACO
at a spatial resolution of 54 mas shows an asymmetric circumstellar
envelope with 300 x 200 mas (12 x 8 stellar radii), elongated in
East-West direction. Furthermore, we succeeded in aperture-synthesis
imaging of L2 Pup by combining these single-dish VLT/NACO data with
near-IR interferometric data taken with the AMBER instrument at the Very
Large Telescope Interferometer. The reconstructed image with a spatial
resolution of 12 mas shows two clumps at 20--30 mas away from the star,
as well as another clump over the stellar. This is the first imaging
of clumpy dust clouds toward L2 Pup, whose presence was only inferred
from polarimetric and photometric observations. Our observations reveal
the clumpy dust formation close to the star, at 1.5--2.5 stellar radii.
Title: The dusty torus in the Circinus galaxy: a dense disk and the
torus funnel
Authors: Tristram, Konrad R. W.; Burtscher, Leonard; Jaffe, Walter;
Meisenheimer, Klaus; Hönig, Sebastian F.; Kishimoto, Makoto;
Schartmann, Marc; Weigelt, Gerd
Bibcode: 2014A&A...563A..82T
Altcode: 2013arXiv1312.4534T
Context. With infrared interferometry it is possible to resolve the
nuclear dust distributions that are commonly associated with the dusty
torus in active galactic nuclei (AGN). The Circinus galaxy hosts the
closest Seyfert 2 nucleus and previous interferometric observations have
shown that its nuclear dust emission is particularly well resolved.
Aims: The aim of the present interferometric investigation is to
better constrain the dust morphology in this active nucleus.
Methods: To this end, extensive new observations were carried out with
the MID-infrared Interferometric instrument (MIDI) at the Very Large
Telescope Interferometer, leading to a total of 152 correlated flux
spectra and differential phases between 8 and 13 μm. To interpret
this data, we used a model consisting of black-body emitters with
a Gaussian brightness distribution and with dust extinction.
Results: The direct analysis of the data and the modelling confirm that
the emission is distributed in two distinct components: a disk-like
emission component with a size (FWHM) of ~0.2 × 1.1 pc and an extended
component with a size of ~0.8 × 1.9 pc. The disk-like component is
elongated along PA ~ 46° and oriented perpendicular to the ionisation
cone and outflow. The extended component is responsible for 80%
of the mid-infrared emission. It is elongated along PA ~ 107°,
which is roughly perpendicular to the disk component and thus in
polar direction. It is interpreted as emission from the inner funnel
of an extended dust distribution and shows a strong increase in the
extinction towards the south-east. We find both emission components to
be consistent with dust at T ~ 300 K, that is we find no evidence of an
increase in the temperature of the dust towards the centre. From this
we infer that most of the near-infrared emission probably comes from
parsec scales as well. We further argue that the disk component alone is
not sufficient to provide the necessary obscuration and collimation of
the ionising radiation and outflow. The material responsible for this
must instead be located on scales of ~1 pc, surrounding the disk. We
associate this material with the dusty torus.
Conclusions:
The clear separation of the dust emission into a disk-like emitter
and a polar elongated source will require an adaptation of our current
understanding of the dust emission in AGN. The lack of any evidence of
an increase in the dust temperature towards the centre poses a challenge
for the picture of a centrally heated dust distribution. Based on
observations collected at the European Southern Observatory, Chile,
programme numbers 073.A-9002(A), 060.A-9224(A), 074.B-0213(A/B),
075.B-0215(A), 077.B-0026(A), 081.B-0893(A), 081.B-0908(A/B),
383.B-0159(A), 383.B-0993(A), 087.B-0746(C), 087.B-0971(A-C), and
087.B-0266(H).Appendices are available in electronic form at http://www.aanda.org
Title: Hydrogen lines as a diagnostic tool for studying multicomponent
emitting regions in hot young stars: magnetosphere, X-wind, and
disk wind
Authors: Tambovtseva, L. V.; Grinin, V. P.; Weigelt, G.
Bibcode: 2014A&A...562A.104T
Altcode:
Infrared interferometric observations with high spatial and
spectral resolution and their quantitative modeling provide us
with a unique opportunity to improve our understanding of the
circumstellar environment of young stars and the accretion-ejection
process. The goal of this paper is to investigate various models of
the emitting regions in young Herbig Ae/Be stars that consist of
(i) a compact rotating magnetosphere; (ii) an X-wind; and (iii) a
disk wind. These models can be used, for example, to quantitatively
interpret line profile measurements and infrared interferometric
observations with the AMBER instrument of the Very Large Telescope
Interferometer (VLTI) in the high spectral resolution mode (R =
12 000). VLTI/AMBER observations allow us to resolve the disk wind
region and study the flux contribution of the unresolved magnetosphere
and X-wind region to the total line flux. Analyzing the results of
our non-LTE calculations, we conclude that the mechanisms of the
different broadening of emission lines of different series include
(1) the kinematic expansion due to the motion of the outflowing,
accelerating gas in the magneto-centrifugal disk wind; (2) the Stark
effect; and (3) the rotation of the magnetosphere. We also investigated
extinction effects that can influence the shape of the line profiles. We
considered the obscuration of the outer disk wind by an opaque dust and
gas disk, the obscuration of the disk wind by a flared disk or by dust
in the disk wind itself, and absorption of the star and disk continuum
radiation in the disk wind along the line of sight. We show that due to
extinction effects, the line profiles can change from double-peaked to
single-peaked and P Cygni profiles. We studied the contribution of the
different components of the stellar environment to different hydrogen
emission lines and investigated how this contribution is dependent on
the model parameters. The results of this study can be used for the
detailed modeling of the emitting regions of individual young stars.
Title: Evidence of a discontinuous disk structure around the Herbig
Ae star HD 139614
Authors: Matter, A.; Labadie, L.; Kreplin, A.; Lopez, B.; Wolf, S.;
Weigelt, G.; Ertel, S.; Pott, J. -U.; Danchi, W. C.
Bibcode: 2014A&A...561A..26M
Altcode: 2013arXiv1311.5131M
The formation and evolution of a planetary system are intrinsically
linked to the evolution of the primordial accretion disk and its
dust and gas content. A new class of pre-main sequence objects has
been recently identified as pre-transitional disks. They present
near-infrared excess coupled to a flux deficit at about 10 microns and
a rising mid-infrared and far-infrared spectrum. These features suggest
a disk structure with inner and outer dust components, separated by a
dust-depleted region (or gap). This could be the result of particular
planet formation mechanisms that occur during the disk evolution. We
here report on the first interferometric observations of the disk
around the Herbig Ae star HD 139614. Its infrared spectrum suggests
a flared disk, and presents pre-transitional features, namely a
substantial near-infrared excess accompanied by a dip around 6 microns
and a rising mid-infrared part. In this framework, we performed a
study of the spectral energy distribution (SED) and the mid-infrared
VLTI/MIDI interferometric data to constrain the spatial structure of
the inner dust disk region and assess its possibly multi-component
structure. We based our work on a temperature-gradient disk model
that includes dust opacity. While we could not reproduce the SED
and interferometric visibilities with a one-component disk, a better
agreement was obtained with a two-component disk model composed of
an optically thin inner disk extending from 0.22 to 2.3 AU, a gap,
and an outer temperature-gradient disk starting at 5.6 AU. Therefore,
our modeling favors an extended and optically thin inner dust component
and in principle rules out the possibility that the near-infrared
excess originates only from a spatially confined region. Moreover,
the outer disk is characterized by a very steep temperature profile
and a temperature higher than 300 K at its inner edge. This suggests
the existence of a warm component corresponding to a scenario where
the inner edge of the outer disk is directly illuminated by the
central star. This is an expected consequence of the presence of a
gap, thus indicative of a "pre-transitional" structure. Based
on observations collected at the European Southern Observatory, Chile
(ESO IDs: 385.C-0886(A) and 087.C-0811(A)).
Title: Young massive binary θ 1 OriC: Radial velocities
of components
Authors: Balega, Yu. Yu.; Chentsov, E. L.; Leushin, V. V.; Rzaev,
A. Kh.; Weigelt, G.
Bibcode: 2014AstBu..69...46B
Altcode:
We succeeded in separating the absorption lines of both the primary
C1 and the secondary C2 component in the spectra of the young
massive binary θ 1 OriC (O6Vp + B0V, mass sum 44 ± 7
M ⊙), obtained during the period from November 1995 to
February 2013 with different telescopes. These observations allowed
us to derive, for the first time, the radial velocities of both
components. The orbitalmotion of the secondary star is traced through
its weak (the line depth is approximately 0.01-0.02) absorption lines
of CII, NII, OII, Si III, which are broadened by fast rotation of the
star. Silicon absorptions Si III λλ 4553, 4568, and 4575 are better
suited for radial velocity measurements than the other lines. From
the velocity curves, we obtained the systemic velocity of the system,
γ = 31 ±2 kms-1, and semi-amplitudes of the C1 and C2
velocities: K 1 = 15 ± 2 kms-1, K 2
= 43 ± 3 kms-1. This leads to individual component masses
of M 1 = 33 ± 5 M ⊙ and M 2 =
11 ± 5 M ⊙, based on the adopted mass sum. At present,
the combined spectroscopic-interferometric orbital solution cannot be
obtained because of the large scatter of velocity measurements caused
by chaotic line shifts in the spectrum of the primary star and by the
weakness of wide absorptions from the secondary. New spectroscopy with
a resolution of R ≥ 30000 and S/N ratio over 200 performed in the
period close to the periastron passage in the second half of 2013,
as well as additional long-baseline interferometry, will be decisive
in refining the parameters of θ 1 OriC. We expect that as
a result of this campaign, masses and luminosities of the components
will be determined with an accuracy of 2-3%.
Title: LEECH: A 100 Night Exoplanet Imaging Survey at the LBT
Authors: Skemer, Andrew; Apai, Daniel; Bailey, Vanessa; Biller, Beth;
Bonnefoy, Mickael; Brandner, Wolfgang; Buenzli, Esther; Close, Laird;
Crepp, Justin; Defrere, Denis; Desidera, Silvano; Eisner, Josh;
Esposito, Simone; Fortney, Jonathan; Henning, Thomas; Hinz, Phil;
Hofmann, Karl-Heinz; Leisenring, Jarron; Males, Jared; Millan-Gabet,
Rafael; Morzinski, Katie; Oza, Apurva; Pascucci, Ilaria; Patience,
Jenny; Rieke, George; Schertl, Dieter; Schlieder, Joshua; Skrutskie,
Mike; Su, Kate; Weigelt, Gerd; Woodward, Charles E.; Zimmerman, Neil
Bibcode: 2014IAUS..299...70S
Altcode: 2014arXiv1401.0481S
In February 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey
began its 100-night campaign from the Large Binocular Telescope atop
Mount Graham in Arizona. LEECH neatly complements other high-contrast
planet imaging efforts by observing stars in L' band (3.8 microns)
as opposed to the shorter wavelength near-infrared bands (1-2.3
microns). This part of the spectrum offers deeper mass sensitivity
for intermediate age (several hundred Myr-old) systems, since their
Jovian-mass planets radiate predominantly in the mid-infrared. In this
proceedings, we present the science goals for LEECH and a preliminary
contrast curve from some early data.
Title: The Classic/climb Beam Combiner at the CHARA Array
Authors: Ten Brummelaar, T. A.; Sturmann, J.; Ridgway, S. T.; Sturmann,
L.; Turner, N. H.; McAlister, H. A.; Farrington, C. D.; Beckmann,
U.; Weigelt, G.; Shure, M.
Bibcode: 2013JAI.....240004T
Altcode:
In the same way that every telescope has multiple instruments and
cameras, an interferometric array like the CHARA Array will have
numerous beam combiners at the back end. And like the instruments of
a single telescope, each of these combiners will be optimized for a
particular kind of observation or scientific program. In this paper we
describe the CLASSIC and CLIMB beam combiners of the CHARA Array. Both
are open air, aperture plane, wide bandwidth single spectral channel
instruments optimized for sensitivity. CLASSIC is the original two beam
combiner used for the first science at CHARA, and it still has the
faintest magnitude limit. CLIMB is a three beam expansion of CLASSIC
that can also provide closure phase measurements.
Title: Evidence for a Receding Dust Sublimation Region around a
Supermassive Black Hole
Authors: Kishimoto, Makoto; Hönig, Sebastian F.; Antonucci, Robert;
Millan-Gabet, Rafael; Barvainis, Richard; Millour, Florentin; Kotani,
Takayuki; Tristram, Konrad R. W.; Weigelt, Gerd
Bibcode: 2013ApJ...775L..36K
Altcode: 2013arXiv1308.6517K
The near-IR emission in Type 1 active galactic nuclei (AGNs) is thought
to be dominated by the thermal radiation from dust grains that are
heated by the central engine in the UV/optical and are almost at the
sublimation temperature. A brightening of the central source can thus
further sublimate the innermost dust, leading to an increase in the
radius of the near-IR emitting region. Such changes in radius have been
indirectly probed by the measurements of the changes in the time lag
between the near-IR and UV/optical light variation. Here we report
direct evidence for such a receding sublimation region through the
near-IR interferometry of the brightest Type 1 AGN in NGC 4151. The
increase in radius follows a significant brightening of the central
engine with a delay of at least a few years, which is thus the implied
destruction timescale of the innermost dust distribution. Compiling
historic flux variations and radius measurements, we also infer the
reformation timescale for the inner dust distribution to be several
years in this galactic nucleus. More specifically and quantitatively,
we find that the radius at a given time seems to be correlated with
a long-term average of the flux over the previous several (~6) years,
instead of the instantaneous flux. Finally, we also report measurements
of three more Type 1 AGNs newly observed with the Keck interferometer,
as well as the second epoch measurements for three other AGNs.
Title: HD 85567: A Herbig B[e] star or an interacting B[e]
binary?. Resolving HD 85567's circumstellar environment with the
VLTI and AMBER
Authors: Wheelwright, H. E.; Weigelt, G.; Caratti o Garatti, A.;
Garcia Lopez, R.
Bibcode: 2013A&A...558A.116W
Altcode: 2013arXiv1308.6000W
Context. HD 85567 is an enigmatic object exhibiting
the B[e] phenomenon, i.e. an infrared excess and forbidden emission
lines in the optical. The object's evolutionary status is uncertain and
there are conflicting claims that it is either a young stellar object
(YSO) or an evolved, interacting binary.
Aims: To elucidate
the reason for the B[e] behaviour of HD 85567, we have observed
it with the VLTI and AMBER.
Methods: Our observations were
conducted in the K-band with moderate spectral resolution (R ~ 1500,
i.e. 200 km s-1). The spectrum of HD 85567 exhibits Brγ
and CO overtone bandhead emission. The interferometric data obtained
consist of spectrally dispersed visibilities, closure phases and
differential phases across these spectral features and the K-band
continuum.
Results: The closure phase observations do not reveal
evidence of asymmetry. The apparent size of HD 85567 in the K-band was
determined by fitting the visibilities with a ring model. The best
fitting radius, 0.8 ± 0.3 AU, is relatively small making HD 85567
undersized in comparison to the size-luminosity relationship based
on YSOs of low and intermediate luminosity. This has previously been
found to be the case for luminous YSOs, and it has been proposed that
this is due to the presence of an optically thick gaseous disc. We
demonstrate that the differential phase observations over the CO
bandhead emission are indeed consistent with the presence of a compact
(~1 AU) gaseous disc interior to the dust sublimation radius.
Conclusions: The observations reveal no sign of binarity. However,
the data do indicate the presence of a gaseous disc interior to the
dust sublimation radius. We conclude that the data are consistent with
the hypothesis that HD 85567 is a YSO with an optically thick gaseous
disc within a larger dust disc that is being photo-evaporated from
the outer edge. Based on observations conducted at the European
Southern Observatory, Paranal, Chile, which were obtained via the
program 089.C-0220.Appendices are available in electronic form at http://www.aanda.org
Title: A diversity of dusty AGN tori. Data release for the VLTI/MIDI
AGN Large Program and first results for 23 galaxies
Authors: Burtscher, L.; Meisenheimer, K.; Tristram, K. R. W.; Jaffe,
W.; Hönig, S. F.; Davies, R. I.; Kishimoto, M.; Pott, J. -U.;
Röttgering, H.; Schartmann, M.; Weigelt, G.; Wolf, S.
Bibcode: 2013A&A...558A.149B
Altcode: 2013arXiv1307.2068B
Context. The AGN-heated dust distribution (the "torus") is increasingly
recognized not only as the absorber required in unifying models, but
as a tracer for the reservoir that feeds the nuclear super-massive
black hole. Yet, even its most basic structural properties (such
as its extent, geometry and elongation) are unknown for all but
a few archetypal objects.
Aims: In order to understand how
the properties of AGN tori are related to feeding and obscuration,
we need to resolve the matter distribution on parsec scales.
Methods: Since most AGNs are unresolved in the mid-IR, even with
the largest telescopes, we utilize the MID-infrared interferometric
Instrument (MIDI) at the Very Large Telescope Interferometer (VLTI)
that is sensitive to structures as small as a few milli-arcseconds
(mas). We present here an extensive amount of new interferometric
observations from the MIDI AGN Large Program (2009-2011) and add
data from the archive to give a complete view of the existing MIDI
observations of AGNs. Additionally, we have obtained high-quality
mid-IR spectra from VLT/VISIR to provide a precise total flux
reference for the interferometric data.
Results: We present
correlated and total fluxes for 23 AGNs (16 of which with new
data) and derive flux and size estimates at 12 μm using simple
axisymmetric geometrical models. Perhaps the most surprising result is
the relatively high level of unresolved flux and its large scatter:
The median "point source fraction" is 70% for type 1 and 47 % for
type 2 AGNs meaning that a large part of the flux is concentrated
on scales <5 mas (0.1-10 pc). Among sources observed with similar
spatial resolution, it varies from 20%-100%. For 18 of the sources,
two nuclear components can be distinguished in the radial fits. While
these models provide good fits to all but the brightest sources,
significant elongations are detected in eight sources.
Conclusions: The half-light radii of the fainter sources are smaller
than expected from the size ∝L0.5 scaling of the bright
sources and show a large scatter, especially when compared to the
relatively tight size-luminosity relation in the near-infrared. It
is likely that a common "size-luminosity" relation does not exist
for AGN tori, but that they are dominated by intrinsic differences
in their dust structures. Variations in the relative contribution of
extended dust in the narrow line region or heated by star formation
vs. compact AGN-heated dust and non-thermal emission also have to
be taken into account. Based on observations collected at the
European Organisation for Astronomical Research in the Southern
Hemisphere, Chile, program numbers 184.B-0832, 087.B-0266 (PI:
K. Meisenheimer), 086.B-0919 (PI: Tristram). Based on data obtained
from the ESO Science Archive Facility.Tables A.2-A.28 as well as all
reduced data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A149
Title: VizieR Online Data Catalog: VLTI/MIDI AGN Large Program
observations (Burtscher+, 2013)
Authors: Burtscher, L.; Meisenheimer, K.; Tristram, K. R. W.;
Jaffe, W.; Honig, S. F.; Davies, R. I.; Kishimoto, M.; Pott, J. -U.;
Rottgering, H.; Schartmann, M.; Weigelt, G.; Wolf, S.
Bibcode: 2013yCat..35580149B
Altcode: 2013yCat..35589149B
All interferometric observations were carried out with MIDI, the
MID-infrared interferometric Instrument at the European Southern
Observatory's (ESO's) Very Large Telescope Interferometer (VLTI)
on Cerro Paranal, Chile. The MIDI AGN Large Program (ESO
program number 184.B-0832) consisted of 13.1 nights of Visitor Mode
observations. Between December 2009 and August 2011, in total 228
science fringe track observations of 15 AGNs have been observed in
this program. For this paper, we also include from the archive 159
previously observed tracks for these sources, 156 fringe tracks of
other weak AGNs and 132 tracks for the two mid-IR brightest AGNs (NGC
1068 and the Circinus galaxy). The observing logs of each galaxy can
be upload in the subdirectory log. OIFITS is the standard for the
exchange of reduced optical interferometry data. It is an IAU accepted
standard and defined in Pauls et al. (2005PASP..117.1255P). Since we use a special observing technique, detailed in the
paper, our primary observable is not the visibility but the
"correlated flux". This is not yet part of the OIFITS specification
(version 1), but is currently discussed for OIFITS version 2.0
(http://ipag.obs.ujf-grenoble.fr/twiki/bin/view/Jmmc/OIFITSTwoProject#
Proposalforcorrelated_flux). For the attached data
I include both the standard VISAMP/VISAMPERR fields which is the
corr. flux divided by the spectrum used for this source (from VISIR, if
available, for all sources except Mrk 1239, see the paper) and also new
CFLUX/CFLUXERR fields that are proposed for OIFITS version 2.0. These
fields comply with the FITS standard and are ignored by strict OIFITS
viewers; less strict OIFITS readers like MIA+EWS's oirgetvis() routine
will read these fields. For NGC 1068, I have downsampled the early
GRISM observations to PRISM resolution so that they can be combined
in one file. The total flux can be retrieved from CFLUX/VISAMP
and its error from flux * sqrt((VISAMPERR/VISAMP)2 -
(CFLUXERR/CFLUX)2). (5 data files).
Title: Spatially resolved atomic and molecular emission from the
very low-mass star YLW52
Authors: Garcia Lopez, Rebeca; Caratti o Garatti, Alessio; Weigelt,
Gerd; Nisini, Brunella; Antoniucci, Simone
Bibcode: 2013prpl.conf1K048G
Altcode: 2013arXiv1307.0677G
Molecular outflows from very low-mass stars (VLMSs) and brown dwarfs
(BDs) have been studied very little, and only a few objects have been
directly imaged. Using VLT SINFONI K-band observations, we spatially
resolved, for the first time, the H2 emission around YLW52, a ~0.1-0.2
Msun Class I source. The molecular emission shows a complex structure
delineating a large outflow cavity and an asymmetric molecular jet. In
addition, new [FeII] VLT ISAAC observations at 1.644 um allowed us to
discover the atomic jet counterpart which extends down to the central
source. The outflow structure is similar to those found in low-mass
Class I young stellar objects (YSOs) and Classical TTauri stars
(CTTSs). However, its Lacc/Lbol ratio is very high (~80%), and the
derived mass accretion rate is about one order of magnitude higher
than in objects with similar mass, pointing to the young nature of
this source.
Title: Revealing the inclined circumstellar disk in the UX Ori system
KK Ophiuchi
Authors: Kreplin, A.; Weigelt, G.; Kraus, S.; Grinin, V.; Hofmann,
K. -H.; Kishimoto, M.; Schertl, D.; Tambovtseva, L.; Clausse, J. -M.;
Massi, F.; Perraut, K.; Stee, Ph.
Bibcode: 2013prpl.conf2B025K
Altcode:
We study the inner sub-AU region of the circumstellar environment of the
UX Ori type star KK Oph with near-infrared VLTI/AMBER interferometry. We
are particularly interested in the inclination of the star-disk
system, and we will use this information to test the current standard
picture for UX Ori stars. We recorded spectrally dispersed (R∼35)
interferograms in the near-infrared H and K bands with the VLTI/AMBER
instrument. The derived visibilities, closure phases and the SED of
KK Oph were compared with two-dimensional geometric and radiative
transfer models (RADMC). We obtained visibilities at four different
position angles. Using two-dimensional geometric models, we derive an
axis ratio ∼3.0 corresponding to an inclination of ∼70 degree. A
fitted inclined ring model leads to a ring radius of 2.8 ± 0.2 mas,
corresponding to 0.44 ± 0.03 AU at a distance of 160 pc, which is
larger than the dust sublimation radius of ∼0.1 AU predicted for a
dust sublimation temperature of 1500 K. Our derived two-dimensional
RADMC model consists of a circumstellar disk with an inclination
angle of ∼70 degree and an additional dust envelope. The finding
of an ∼70 degree inclined disk around KK Oph is consistent with
the prediction that UX Ori objects are seen under large inclination
angles, and orbiting clouds in the line of sight cause the observed
variability. Furthermore, our results suggest that the orbit of the
companion KK Oph B and the disk plane are coplanar.
Title: Evidence of a discontinuous inner disk structure around the
Herbig star HD 139 614
Authors: Matter, Alexis; Labadie, Lucas; Kreplin, Alexander; Lopez,
Bruno; Wolf, Sebastian; Weigelt, Gerd; Ertel, Steve; Pott, Jörg-Uwe;
Danchi, William C.
Bibcode: 2013prpl.conf2B014M
Altcode:
A new class of pre-main sequence objects has been recently identified as
`pre-transitional disks'. They present a near-infrared excess coupled
to a flux deficit around 10 microns and then a rising mid-infrared
spectrum. Therefore, they probably represent disk showing an inner
and outer dust component separated by a dust-depleted region (or
gap). Such a configuration could be for instance the result of planet
formation processes occuring during the disk evolution (see e.g. the
case of LkCa 15; Espaillat et al. 2008, Kraus et al. 2012). We here
report on the first interferometric observations of the disk around
the Herbig Ae star HD 139 614. Its infrared spectrum suggests a flared
disk and presents a substantial near-infrared excess accompanied by a
dip around 6 microns, then followed by a rising mid-infrared part. We
modeled both the SED and mid-infrared VLTI/MIDI interferometric data
to constrain the spatial structure of the inner dust disk region, and
assess its possibly multi-component organisation. A good agreement
with the measured mid-infrared SED and interferometric visibilities
was obtained with an unresolved component emitting at 1500 K, followed
by a gap extending to 5.9 AU, and an outer temperature-gradient disk
characterized by a steep temperature profile and a high temperature
of about 350 K at its inner edge. This suggests a warm component
corresponding to the inner edge of the outer disk directly illuminated
by the central star. This is an expected consequence of the presence of
a gap, possibly indicative of a pre-transitional structure. However,
our best-fit model underestimated the near-infrared excess. This
suggests the existence of an extended inner component that is partly
resolved by MIDI.
Title: High spectral resolution imaging of the dynamical atmosphere
of the red supergiant Antares in the CO first overtone lines with
VLTI/AMBER
Authors: Ohnaka, K.; Hofmann, K. -H.; Schertl, D.; Weigelt, G.; Baffa,
C.; Chelli, A.; Petrov, R.; Robbe-Dubois, S.
Bibcode: 2013A&A...555A..24O
Altcode: 2013arXiv1304.4800O
Aims: We present aperture-synthesis imaging of the red supergiant
Antares (α Sco) in the CO first overtone lines. Our goal is to probe
the structure and dynamics of the outer atmosphere.
Methods:
Antares was observed between 2.28 μm and 2.31 μm with VLTI/AMBER
with spectral resolutions of up to 12 000 and angular resolutions as
high as 7.2 mas at two epochs with a time interval of one year.
Results: The reconstructed images in individual CO lines reveal that
the star appears differently in the blue wing, line center, and red
wing. In 2009, the images in the line center and red wing show an
asymmetrically extended component, while the image in the blue wing
shows little trace of it. In 2010, however, the extended component
appears in the line center and blue wing, and the image in the red wing
shows only a weak signature of the extended component. Our modeling of
these AMBER data suggests that there is an outer atmosphere (MOLsphere)
extending to 1.2-1.4 R⋆ with CO column densities of
(0.5-1) × 1020 cm-2 and a temperature of ~2000
K. The CO line images observed in 2009 can be explained by a model
in which a large patch or clump of CO gas is infalling at only 0-5
km s-1, while the CO gas in the remaining region is moving
outward much faster at 20-30 km s-1. The images observed in
2010 suggest that a large clump of CO gas is moving outward at 0-5 km
s-1, while the CO gas in the remaining region is infalling
much faster at 20-30 km s-1. In contrast to the images in the
CO lines, the AMBER data in the continuum show only a slight deviation
from limb-darkened disks and only marginal time variations. We derive
a limb-darkened disk diameter of 37.38 ± 0.06 mas and a power-law-type
limb-darkening parameter of (8.7 ± 1.6) × 10-2 (2009) and
37.31 ± 0.09 mas and (1.5 ± 0.2) × 10-1 (2010). We also
obtain an effective temperature of 3660 ± 120 K (the error includes the
effects of the temporal flux variation that is assumed to be the same
as Betelgeuse) and a luminosity of log L⋆/L⊙
= 4.88 ± 0.23. Comparison with theoretical evolutionary tracks
suggests a mass of 15 ± 5 M⊙ with an age of 11-15
Myr, which is consistent with the recently estimated age for the
Upper Scorpius OB association.
Conclusions: The properties
of the outer atmosphere of Antares are similar to those of another
well-studied red supergiant, Betelgeuse. The density of the extended
outer atmosphere of Antares and Betelgeuse is higher than predicted
by the current 3D convection simulations by at least six orders of
magnitude, implying that convection alone cannot explain the formation
of the extended outer atmosphere. Based on AMBER observations
made with the Very Large Telescope Interferometer of the European
Southern Observatory. Program ID: 083.D-0333(A/B) (AMBER guaranteed time
observation), 085.D-0085(A/B).Appendices are available in electronic
form at http://www.aanda.orgMovies
of data cube are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A24
Title: A 100-Night Exoplanet Imaging Survey at the LBT
Authors: Zimmerman, Neil; Skemer, Andrew; Apai, Daniel; Bailey,
Vanessa; Biller, Beth; Bonnefoy, Mickael; Brandner, Wolfgang; Buenzli,
Esther; Close, Laird; Crepp, Justin; Defrere, Denis; Desidera, Silvano;
Eisner, Josh; Esposito, Simone; Fortney, Jonathan; Henning, Thomas;
Hinz, Phil; Hofmann, Karl-Heinz; Leisenring, Jarron; Males, Jared;
Millan-Gabet, Rafael; Morzinski, Katie; Pascucci, Ilaria; Patience,
Jenny; Rieke, George; Schertl, Dieter; Schlieder, Joshua; Skrutskie,
Michael; Su, Kate; Woodward, Chick; Weigelt, Gerd
Bibcode: 2013prpl.conf2K006Z
Altcode:
In February 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey
began its 100-night campaign from the Large Binocular Telescope atop
Mount Graham in Arizona. LEECH neatly complements other high-contrast
planet imaging efforts by observing stars in L' band (3.8 microns)
as opposed to the shorter wavelength near-infrared bands (1-2.3
microns). This part of the spectrum offers deeper mass sensitivity
for intermediate age (several hundred Myr-old) systems, since their
Jovian-mass planets radiate predominantly in the mid-infrared. We
present the science goals for LEECH and a preliminary contrast curve
from some early data.
Title: Dust in the Polar Region as a Major Contributor to the Infrared
Emission of Active Galactic Nuclei
Authors: Hönig, S. F.; Kishimoto, M.; Tristram, K. R. W.; Prieto,
M. A.; Gandhi, P.; Asmus, D.; Antonucci, R.; Burtscher, L.; Duschl,
W. J.; Weigelt, G.
Bibcode: 2013ApJ...771...87H
Altcode: 2013arXiv1306.4312H
Dust around active galactic nuclei (AGNs) is distributed over a wide
range of spatial scales and can be observed in the infrared (IR). It
is generally assumed that the distribution on parsec scales forms a
geometrically and optically thick entity in the equatorial plane around
the accretion disk and broad-line region—dubbed "dust torus"—that
emits the bulk of the subarcsecond-scale IR emission and gives rise to
orientation-dependent obscuration. However, recent IR interferometry
studies with unprecedented position angle (P.A.) and baseline coverage
on these small scales in two obscured (type 2) AGNs have revealed that
the majority of the mid-IR emission in these objects is elongated in the
polar direction. These observations are difficult to reconcile with the
standard interpretation that most of the parsec-scale mid-IR emission
in AGNs originate from the torus and challenges the justification of
using simple torus models to model the broadband IR emission. Here,
we report detailed interferometry observations of the unobscured (type
1) AGN in NGC 3783 that allow us to constrain the size, elongation,
and direction of the mid-IR emission with high accuracy. The mid-IR
emission is characterized by a strong elongation toward position angle
P.A. -52°, closely aligned with the polar axis (P.A. -45°). We
determine half-light radii along the major and minor axes at 12.5
μm of (20.0 ± 3.0) mas × (6.7 ± 1.0) mas or (4.23 ± 0.63) pc ×
(1.42 ± 0.21) pc, which corresponds to intrinsically scaled sizes
of (69.4 ± 10.8) r in × (23.3 ± 3.5) r in
for the inner dust radius of r in = 0.061 pc as inferred
from near-IR reverberation mapping. This implies an axis ratio of
3:1, with about 60%-90% of the 8-13 μm emission associated with
the polar-elongated component. It is quite likely that the hot-dust
emission as recently resolved by near-IR interferometry is misaligned
with the mid-IR emitting source, which also finds a correspondence in
the two distinct 3-5 μm and 20 μm bumps seen in the high angular
resolution spectral energy distribution (SED). Based on this SED,
we determine covering factors for the hot and warm dust components of
C_{hot} = 0.42^{+0.42}_{-0.21} and C_{warm} = 0.92^{+0.92}_{-0.46},
respectively. We conclude that these observations support a scenario
where the majority of the mid-IR emission in Seyfert AGNs originate
from a dusty wind in the polar region of the AGN.
Title: VizieR Online Data Catalog: Aperture-synthesis imaging of
Antares (Ohnaka+, 2013)
Authors: Ohnaka, K.; Hofmann, K. -H.; Schertl, D.; Weigelt, G.; Baffa,
C.; Chelli, A.; Petrov, R.; Robbe-Dubois, S.
Bibcode: 2013yCat..35550024O
Altcode: 2013yCat..35559024O
Two animated gif movies made from high spectral resolution aperture-
synthesis imaging of the red supergiant Antares in the CO first
overtone lines near 2.3 micron. The observations were carried out
with the near-IR interferometric instrument AMBER at the Very Large
Telescope Interferometer with a spatial resolution of 9.8 mas and a
spectral resolution of 8000. The movies are based on the data taken in
2009. The first movie (alfsco1.gif) shows the observed CO line
spectrum from 2.28 and 2.31 micron in the lower panel (normalized
with the continuum). As the dot in the lower panel moves across the
spectrum, the image reconstructed at each wavelength is shown in the
upper panel. The reconstructed image at each wavelength is normalized
with its peak intensity. The images at 2.303275 and 2.303455 micron
are severely affected by bad data points and are unreliable. The
second movie (alfsco2.gif) shows the spatially resolved spectrum at
each position along a line across the stellar image. The movie shows,
in the lower panel, the reconstructed image of Antares in the center
of the CO line at 2.3058 micron. As the gray dot moves across the
stellar image, the spatially resolved spectrum at each position is
shown in red in the upper panel. The spatially resolved spectra are
scaled for comparison with the spatially unresolved spectrum shown in
black. The extraction of the spatially resolved spectra is described
in Sect. 3.3. (3 data files).
Title: LBT/LUCIFER near-infrared spectroscopy of PV Cephei. An
outbursting young stellar object with an asymmetric jet
Authors: Caratti o Garatti, A.; Garcia Lopez, R.; Weigelt, G.;
Tambovtseva, L. V.; Grinin, V. P.; Wheelwright, H.; Ilee, J. D.
Bibcode: 2013A&A...554A..66C
Altcode: 2013arXiv1304.6267G; 2013A&A...554A..66G
Context. Young stellar objects (YSOs) occasionally experience enhanced
accretion events, the nature of which is still poorly understood. The
discovery of various embedded outbursting YSOs has recently questioned
the classical definition of EXors and FUors.
Aims: We present
a detailed spectroscopic investigation of the young eruptive star PV
Cep, to improve our understanding of its nature and characterise its
circumstellar environment after its last outburst in 2004.
Methods: The analysis of our medium-resolution spectroscopy in the
near-infrared (NIR, 0.9-2.35 μm), collected in 2012 at the Large
Binocular Telescope with the IR spectrograph LUCIFER, allows us to infer
the main stellar parameters (visual extinction, accretion luminosity,
mass accretion and ejection rates), and model the inner disc, jet, and
wind.
Results: The NIR spectrum displays several strong emission
lines associated with accretion/ejection activity and circumstellar
environment. Our analysis shows that the brightness of PV Cep is fading,
as well as the mass accretion rate (2 × 10-7 M⊙
yr-1 in 2012 vs. ~5 × 10-6 M⊙
yr-1 in 2004), which is more than one order of magnitude
lower than in the outburst phase. Among the several emission lines,
only the [Fe ii] intensity increased after the outburst. The observed
[Fe ii] emission delineates blue- and red-shifted lobes, both with
high- and low-velocity components, which trace an asymmetric jet and
wind, respectively. The observed emission in the jet has a dynamical
age of 7-8 years, indicating that it was produced during the last
outburst. The visual extinction decreases moving from the red-shifted
(AV(red) = 10.1 ± 0.7 mag) to the blue-shifted lobe
(AV(blue) = 6.5 ± 0.4 mag). We measure an average
electron temperature of 17 500 K and electron densities of 30 000
cm-3 and 15 000 cm-3 for the blue and the red
lobe, respectively. The mass ejection rate in both lobes is ~1.5
× 10-7 M⊙ yr-1, approximately
matching the high accretion rate observed during and immediately after
the outburst (Ṁout/Ṁacc ~ 0.05-0.1). The
observed jet/outflow asymmetries are consistent with an inhomogeneous
medium. Our modelling of the CO emission hints at a small-scale gaseous
disc ring, extending from ~0.2-0.4 AU to ~3 AU from the source, with
an inner temperature of ~3000 K. Our H i lines modelling indicates
that most of the observed emission comes from an expanding disc wind
at Te = 10 000 K. The line profiles are strongly affected
by scattering, disc screening, and outflow self-absorption.
Conclusions: According to the classical definition, PV Cep is not
an EXor object, because it is more massive and younger than typical
EXors. Nevertheless, its spectrum shows the signature of an "EXor-like"
outburst, suggesting a common origin. Based on observations
collected at LBT. The LBT is an international collaboration among
institutions in the United States, Italy and Germany. LBT Corporation
partners are: LBT Beteiligungsgesellschaft, Germany, representing
the Max-Planck Society, the Astrophysical Institute Potsdam,
and Heidelberg University; The University of Arizona on behalf of
the Arizona university system; Istituto Nazionale di Astrofisica,
Italy; The Ohio State University, and The Research Corporation, on
behalf of The University of Notre Dame, University of Minnesota and
University of Virginia.Appendix A is available in electronic form at
http://www.aanda.org
Title: Spatially resolved H2 emission from a very
low-mass star
Authors: Garcia Lopez, R.; Caratti o Garatti, A.; Weigelt, G.; Nisini,
B.; Antoniucci, S.
Bibcode: 2013A&A...552L...2G
Altcode: 2013arXiv1302.6749G
Context. Molecular outflows from very low-mass stars (VLMSs) and
brown dwarfs have been studied very little. So far, only a few
CO outflows have been observed, allowing us to map the immediate
circumstellar environment.
Aims: We present the first
spatially resolved H2 emission around IRS54 (YLW 52),
a ~0.1-0.2 M⊙ Class I source.
Methods: By means
of VLT SINFONI K-band observations, we probed the H2
emission down to the first ~50 AU from the source.
Results:
The molecular emission shows a complex structure delineating a large
outflow cavity and an asymmetric molecular jet. Thanks to the detection
of several H2 transitions, we are able to estimate average
values along the jet-like structure (from source position to knot D)
of AV ~ 28 mag, T ~ 2000-3000 K, and H2 column
density N(H2) ~ 1.7 × 1017 cm-2. This
allows us to estimate a mass loss rate of ~2 × 10-10
M⊙ yr-1 for the warm H2 component. In
addition, from the total flux of the Br γ line, we infer an accretion
luminosity and mass accretion rate of 0.64 L⊙ and ~3
× 10-7M⊙ yr-1, respectively. The
outflow structure is similar to those found in low-mass Class I and
CTTS. However, the Lacc/Lbol ratio is very high
(~80%), and the mass accretion rate is about one order of magnitude
higher when compared to objects of roughly the same mass, pointing to
the young nature of the investigated source. Based on observations
collected at the European Southern Observatory Paranal, Chile (ESO
programme 385.C-0893(A)).Appendices are available in electronic
form at http://www.aanda.orgThe
reduced datacube is only available at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/L2
Title: Pre-main-sequence binaries with tidally disrupted discs:
the Brγ in HD 104237
Authors: Garcia, P. J. V.; Benisty, M.; Dougados, C.; Bacciotti, F.;
Clausse, J. -M.; Massi, F.; Mérand, A.; Petrov, R.; Weigelt, G.
Bibcode: 2013MNRAS.430.1839G
Altcode: 2013arXiv1301.0276G
Active pre-main-sequence binaries with separations of around 10
stellar radii present a wealth of phenomena unobserved in common
systems. The study of these objects is extended from classical
T Tauri stars to the Herbig Ae star HD 104237. The primary
has a mass 2.2 ± 0.2 M⊙ and secondary 1.4 ± 0.3
M⊙. Spectrointerferometry with the VLTI/AMBER in the
K-band continuum and the Brγ line is presented. It is found
that the K-band continuum squared visibilities are compatible with a
circumbinary disc with a radius of ∼0.5 AU. However, a significant
fraction (∼50 per cent) of the flux is unresolved and not fully
accounted by the stellar photospheres. The stars probably do not hold
circumstellar discs, in addition to the circumbinary disc, due to the
combined effects of inner magnetospheric truncation and outer tidal
truncation. This unresolved flux likely arises in compact structures
inside the tidally disrupted circumbinary disc. Most (≳90 per
cent) of the Brγ line emission is unresolved. The line-to-continuum
spectroastrometry shifts in time, along the direction of the Lyα
jet known to be driven by the system. The shift is anticorrelated
with the Brγ equivalent width. It is shown that the unresolved Brγ
emission cannot originate in the jet but instead is compatible with
stellar emission from the orbiting binary components. The increase
in the absolute value of the equivalent width of the line takes place
at periastron passage; it could arise in an accretion burst, a flare
or in the increase in effective size of the emission region by the
interaction of the magnetospheres. The binary longitude of the ascending
node is found to be Ω = (235 ± 3)° and the orbit retrograde. The origin of the jet is revisited. The tidal disruption of the
circumstellar discs creates difficulties to ejection models that rely
on stellar magnetosphere and disc coupling. A scenario of a stellar
wind collimated by a circumbinary disc wind is suggested.
Title: Revealing the inclined circumstellar disk in the UX Orionis
system KK Ophiuchi
Authors: Kreplin, A.; Weigelt, G.; Kraus, S.; Grinin, V.; Hofmann,
K. -H.; Kishimoto, M.; Schertl, D.; Tambovtseva, L.; Clausse, J. -M.;
Massi, F.; Perraut, K.; Stee, Ph.
Bibcode: 2013A&A...551A..21K
Altcode:
Aims: We study the inner sub-AU region of the circumstellar
environment of the UX Ori-type star KK Oph with
near-infrared VLTI/AMBER interferometry. We are particularly interested
in the inclination of the star-disk system, and we use this information
to test the current standard picture for UX Ori stars.
Methods:
We recorded spectrally dispersed (R ~ 35) interferograms in the
near-infrared H and K bands with the VLTI/AMBER instrument. The derived
visibilities, closure phases, and the spectral energy distribution
of KK Oph were compared with two-dimensional geometric and radiative
transfer models (RADMC).
Results: We obtained visibilities at
four different position angles. Using two-dimensional geometric models,
we derive an axis ratio ~3.0 corresponding to an inclination of ~70°. A
fitted inclined ring model leads to a ring radius of 2.8 ± 0.2 mas,
corresponding to 0.44 ± 0.03 AU at a distance of 160 pc, which is
larger than the dust sublimation radius of ~0.1 AU predicted for a
dust sublimation temperature of 1500 K. Our derived two-dimensional
RADMC model consists of a circumstellar disk with an inclination
angle of ~70° and an additional dust envelope.
Conclusions:
The finding of an ~70° inclined disk around KK Oph is consistent with
the prediction that UX Ori objects are seen under large inclination
angles, and orbiting clouds in the line of sight cause the observed
variability. Furthermore, our results suggest that the orbit of the
companion KK Oph B and the disk plane are coplanar. Based on
observations made with ESO telescopes at Paranal Observatory under
program ID: 083.D-0224(C) and 088.C-0575(A).
Title: Resolving the innermost dusty accretion in the brightest Type
1 AGN with the CHARA array
Authors: Kishimoto, Makoto; Barvainis, Richard; Antonucci, Robert;
Hoenig, Sebastian; Millour, Florentin; Tristram, Konrad; Weigelt, Gerd
Bibcode: 2013noao.prop..241K
Altcode:
We believe that we have finally started to spatially resolve and
quantify the innermost dusty structure in AGN tori with long-baseline
interferometry in the infrared. A major goal here is to see if
the inner radial distribution of the accreting material is closely
related to the mode of the central engine: based on the results so
far, this might indeed be the case. However, our previous and on-going
observations have a big limitation in the baseline length, with which
we can only marginally resolve the structure, leaving ambiguity in the
interpretation of the data. Here we propose to break this limit by
using the very long baselines offered in the CHARA array. This will
test our fundamental picture and conclusively measure the innermost
dusty structure in the brightest Type 1 AGN.
Title: Unveiling the inner structure of EXor eruptive variables
Authors: Kloppenborg, Brian; Antoniucci, Simone; Li Causi, Gianluca;
Lorenzetti, Dario; Giannini, Teresa; Weigelt, Gerd; Kishimoto, Makoto
Bibcode: 2013noao.prop..151K
Altcode:
We plan to conduct the first comprehensive high spatial resolution study
of EXor objects in order to understand the mechanism regulating their
recurrent accretion outburst and to access the differences/similarities
with respect to other classes of YSO objects such as FUors and
classical T Tauri stars. Here we propose a mini survey of four EXors
that are observable with both CHARA and the VLTI. We will derive the
properties of the inner/outer disk and of emission line regions with
radiative transfer codes and compare the results to those obtained
for T Tauri stars. As the objects will most likely be in quiescence,
these interferometric data will serve as a pre-outburst baseline for
a future comparative analysis between quiescence and outburst phases,
which we plan to perform. To this aim we are now beginning a photometric
and spectroscopic EXor monitoring program that will ensure we promptly
detect any future outburst of known EXors.
Title: VizieR Online Data Catalog: SINFONI K-band observations of
IRS54(YLW52) (Garcia Lopez+, 2013)
Authors: Garcia Lopez, R.; Caratti, O. Garatti A.; Weigelt, G.;
Nisini, B.; Antoniucci, S.
Bibcode: 2013yCat..35529002G
Altcode:
SINFONI K-band integral field spectroscopic datacube of the YSO IRS54
(YLW52) at medium resolution (R~4000). The main data reduction
process was done using the SINFONI data-reduction pipeline, i.e.,
dark and bad pixel masks, flat-field corrections, optical distortion
correction, and wavelength calibration using arc lamps. A
systematic wavelength shift of ~2.2 Angstroms was found and should be
taken into account. The STARLINK software was used to correct
the spectrum from atmospheric absorption and to flux-calibrate the
data. Flux units are erg/s/cm^2; Wavelength units are microns. (2
data files).
Title: Spatially resolved atomic and molecular emission from the
very low-mass star IRS54.
Authors: Garcia Lopez, R.; Caratti o Garatti, A.; Weigelt, G.; Nisini,
B.; Antoniucci, S.
Bibcode: 2013MmSAI..84..875G
Altcode:
Molecular outflows from very low-mass stars and brown dwarfs have
been studied very little, and only a few objects have been directly
imaged. Using VLT SINFONI K-band observations, we spatially resolved,
for the first time, the H_2 emission around IRS54, a ∼0.1-0.2 M_⊙
Class I source. The molecular emission shows a complex structure
delineating a large outflow cavity and an asymmetric molecular jet. In
addition, new [Fe II] VLT ISAAC observations at 1.644 mu m allowed us to
discover the atomic jet counterpart which extends down to the central
source. The outflow structure is similar to those found in low-mass
Class I young stellar objects and Classical T Tauri stars. However, its
L_acc/L_bol ratio is very high (∼80%), and the derived mass accretion
rate is about one order of magnitude higher than in objects with
similar mass, pointing to the young nature of the investigated source.
Title: A Companion as the Cause of Latitude-dependent Effects in
the Wind of Eta Carinae
Authors: Groh, J. H.; Madura, T. I.; Hillier, D. J.; Kruip, C. J. H.;
Weigelt, G.
Bibcode: 2012ApJ...759L...2G
Altcode: 2012arXiv1210.2709G
We analyze spatially resolved spectroscopic observations of the Eta
Carinae binary system obtained with the Hubble Space Telescope/STIS. Eta
Car is enshrouded by the dusty Homunculus nebula, which scatters light
emitted by the central binary and provides a unique opportunity to study
a massive binary system from different vantage points. We investigate
the latitudinal and azimuthal dependence of Hα line profiles caused
by the presence of a wind-wind collision (WWC) cavity created by
the companion star. Using two-dimensional radiative transfer models,
we find that the wind cavity can qualitatively explain the observed
line profiles around apastron. Regions of the Homunculus which
scatter light that propagated through the WWC cavity show weaker or
no Hα absorption. Regions scattering light that propagated through
a significant portion of the primary wind show stronger P Cygni
absorption. Our models overestimate the Hα absorption formed in the
primary wind, which we attribute to photoionization by the companion,
not presently included in the models. We can qualitatively explain
the latitudinal changes that occur during periastron, shedding light
on the nature of Eta Car's spectroscopic events. Our models support
the idea that during the brief period of time around periastron when
the primary wind flows unimpeded toward the observer, Hα absorption
occurs in directions toward the central object and Homunculus SE pole,
but not toward equatorial regions close to the Weigelt blobs. We suggest
that observed latitudinal and azimuthal variations are dominated by
the companion star via the WWC cavity, rather than by rapid rotation
of the primary star. Based on observations made with HST/STIS.
Title: AMBER/VLTI observations of the B[e] star MWC 300
Authors: Wang, Y.; Weigelt, G.; Kreplin, A.; Hofmann, K. -H.; Kraus,
S.; Miroshnichenko, A. S.; Schertl, D.; Chelli, A.; Domiciano de Souza,
A.; Massi, F.; Robbe-Dubois, S.
Bibcode: 2012A&A...545L..10W
Altcode: 2012arXiv1208.5882W
Aims: We study the enigmatic B[e] star MWC 300 to investigate its
disk and binary with milli-arcsecond-scale angular resolution.
Methods: We observed MWC 300 with the VLTI/AMBER instrument in the H
and K bands and compared these observations with temperature-gradient
models to derive model parameters.
Results: The measured
low visibility values, wavelength dependence of the visibilities,
and wavelength dependence of the closure phase directly suggest that
MWC 300 consists of a resolved disk and a close binary. We present
a model consisting of a binary and a temperature-gradient disk that
is able to reproduce the visibilities, closure phases, and spectral
energy distribution. This model allows us to constrain the projected
binary separation (~4.4 mas or ~7.9 AU), the flux ratio of the binary
components (~2.2), the disk temperature power-law index, and other
parameters. Based on observations made with ESO telescopes at
Paranal Observatory under program ID 083.D-0224(C).
Title: VizieR Online Data Catalog: Interferometry of α Eri (Domiciano
de Souza+, 2012)
Authors: Domiciano de Souza, A.; Hadjara, M.; Vakili, F.; Bendjoya,
P.; Millour, F.; Abe, L.; Carciofi, A. C.; Faes, D. M.; Kervella,
P.; Lagarde, S.; Marconi, A.; Monin, J. -L.; Niccolini, G.; Petrov,
R. G.; Weigelt, G.
Bibcode: 2012yCat..35450130D
Altcode: 2012yCat..35459130D
We used the AMBER focal instrument at ESO-VLTI in its high spectral
resolution mode to record interferometric data on the fast rotator
Achernar. Differential phases centered on the hydrogen Brγ line
(K band) were obtained during four almost consecutive nights with a
continuous Earth-rotation synthesis during ~5h/night, corresponding
to ~60° position angle coverage per baseline. These observations
were interpreted with our numerical code dedicated to long-baseline
interferometry of rotating stars. (2 data files).
Title: Beyond the diffraction limit of optical/IR
interferometers. I. Angular diameter and rotation parameters of
Achernar from differential phases
Authors: Domiciano de Souza, A.; Hadjara, M.; Vakili, F.; Bendjoya,
P.; Millour, F.; Abe, L.; Carciofi, A. C.; Faes, D. M.; Kervella,
P.; Lagarde, S.; Marconi, A.; Monin, J. -L.; Niccolini, G.; Petrov,
R. G.; Weigelt, G.
Bibcode: 2012A&A...545A.130D
Altcode:
Context. Spectrally resolved long-baseline optical/IR interferometry
of rotating stars opens perspectives to investigate their fundamental
parameters and the physical mechanisms that govern their interior,
photosphere, and circumstellar envelope structures.
Aims: Based
on the signatures of stellar rotation on observed interferometric
wavelength-differential phases, we aim to measure angular diameters,
rotation velocities, and orientation of stellar rotation axes.
Methods: We used the AMBER focal instrument at ESO-VLTI in its
high-spectral resolution mode to record interferometric data on the
fast rotator Achernar. Differential phases centered on the hydrogen
Br γ line (K band) were obtained during four almost consecutive
nights with a continuous Earth-rotation synthesis during ~5 h/night,
corresponding to ~60° position angle coverage per baseline. These
observations were interpreted with our numerical code dedicated
to long-baseline interferometry of rotating stars.
Results:
By fitting our model to Achernar's differential phases from AMBER,
we could measure its equatorial radius Req = 11.6 ± 0.3
R⊙, equatorial rotation velocity Veq = 298 ± 9
km s-1, rotation axis inclination angle i = 101.5 ± 5.2°,
and rotation axis position angle (from North to East) PArot
= 34.9 ± 1.6°. From these parameters and the stellar distance, the
equatorial angular diameter ⌀eq of Achernar is found to be
2.45 ± 0.09 mas, which is compatible with previous values derived from
the commonly used visibility amplitude. In particular, ⌀eq
and PArot measured in this work with VLTI/AMBER are
compatible with the values previously obtained with VLTI/VINCI.
Conclusions: The present paper, based on real data, demonstrates the
super-resolution potential of differential interferometry for measuring
sizes, rotation velocities, and orientation of rotating stars in cases
where visibility amplitudes are unavailable and/or when the star is
partially or poorly resolved. In particular, we showed that differential
phases allow the measurement of sizes up to ~4 times smaller than
the diffraction-limited angular resolution of the interferometer. Based on observations performed at ESO, Chile under AMBER-consortium
GTO programme ID 084.D-0456.Full Fig. 5 is available in electronic
form at http://www.aanda.orgThe
FITS tables of the reduced data are only available at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A130
Title: Parsec-scale Dust Emission from the Polar Region in the Type
2 Nucleus of NGC 424
Authors: Hönig, S. F.; Kishimoto, M.; Antonucci, R.; Marconi, A.;
Prieto, M. A.; Tristram, K.; Weigelt, G.
Bibcode: 2012ApJ...755..149H
Altcode: 2012arXiv1206.4307H
Advancements in infrared (IR) interferometry open up the possibility
to spatially resolve active galactic nuclei (AGNs) on the parsec-scale
level and study the circumnuclear dust distribution, commonly referred
to as the "dust torus," that is held responsible for the type 1/type
2 dichotomy of AGNs. We used the mid-IR beam combiner MIDI together
with the 8 m telescopes at the Very Large Telescope Interferometer
to observe the nucleus of the Seyfert 2 galaxy NGC 424, achieving an
almost complete coverage of the uv-plane accessible by the available
telescope configurations. We detect extended mid-IR emission with a
relatively baseline- and model-independent mid-IR half-light radius
of (2.0 ± 0.2) pc × (1.5 ± 0.3) pc (averaged over the 8-13 μm
wavelength range). The extended mid-IR source shows an increasing size
with wavelength. These properties are in agreement with the idea of
dust heated in thermal equilibrium with the AGN. The orientation of
the major axis in position angle ~ - 27° is closely aligned with the
system axis as set by optical polarization observations. Torus models
typically favor extension along the mid-plane at mid-IR wavelengths
instead. Therefore, we conclude that the majority of the parsec-scale
mid-IR emission (gsim60%) in this type 2 AGN originates from optically
thin dust in the polar region of the AGN, a scenario consistent with
the near- to far-IR spectral energy distribution. We suggest that
a radiatively driven dusty wind, possibly launched in a puffed-up
region of the inner hot part of the torus, is responsible for the polar
dust. In this picture, the torus dominates the near-IR emission up to
about 5 μm, while the polar dust is the main contributor to the mid-IR
flux. Our results of NGC 424 are consistent with recent observations of
the AGN in the Circinus galaxy and resemble large-scale characteristics
of other objects. If our results reflect a general property of the AGN
population, the current paradigm for interpreting and modeling the IR
emission of AGNs has to be revised.
Title: Spectral line profiles changed by dust scattering in heavily
obscured young stellar objects
Authors: Grinin, V. P.; Tambovtseva, L. V.; Weigelt, G.
Bibcode: 2012A&A...544A..45G
Altcode: 2012arXiv1207.2576G
It is known that scattering of radiation by circumstellar dust can
strongly change the line profiles in stellar spectra. This hampers
the analysis of spectral lines originating in the emitting regions of
heavily obscured young stars. To calculate the line profile of the
scattered radiation, we suggest to use the approximation of remote
scattering particles. This approximation assumes that the scattering
dust grains are at a distance from the star that is much larger than
the characteristic size of the emitting region. Using this method,
we calculated the line profiles of several simple models. They show
the Hα line profiles of Herbig AeBe stars in the presence and absence
of motionless or moving dust.
Title: LINC-NIRVANA: assembly, integration, and verification update
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2012SPIE.8445E..0VH
Altcode:
We present an update on the LINC-NIRVANA (LN) instrument, an innovative
Fizeau-mode beam combiner for the Large Binocular Telescope (LBT). LN
will deliver 10 mas spatial resolution in the near infrared over a 10
arcsec field of view. In addition to optical-path-difference control,
the instrument must correct a wide field of view on the sky using
multi-conjugated adaptive optics. This substantially increases sky
coverage for fringe tracking reference stars. Subsystem delivery
and testing is almost complete, and final Assembly, Integration,
and Verification are well advanced. We report on closed-loop control
of a number of subsystems, including fine-tuning and optimization of
the delay line. Measurement and remediation of instrument flexure are
key to the success of LN. Several laboratory performance experiments
demonstrate that components are within specification. With several
interacting subsystems, LN faces a complexity challenge. A Pathfinder
experiment at LBT will verify multiple aspects of LINC-NIRVANA and the
telescope starting in winter 2012-2013. Finally, we report on efforts
to prepare for early science exploitation in "LINC" mode, which uses
single-conjugate adaptive optics.
Title: Revealing the inner circumstellar disk of the T Tauri star
S Coronae Australis N using the VLTI
Authors: Vural, J.; Kreplin, A.; Kraus, S.; Weigelt, G.; Driebe, T.;
Benisty, M.; Dugué, M.; Massi, F.; Monin, J. -L.; Vannier, M.
Bibcode: 2012A&A...543A.162V
Altcode: 2012arXiv1207.2467V
Aims: We investigate the structure of the circumstellar disk of
the T Tauri star S CrA N and test whether the observations agree with
the standard picture proposed for Herbig Ae stars.
Methods:
Our observations were carried out with the VLTI/AMBER instrument
in the H and K bands with the low spectral resolution mode. For the
interpretation of our near-infrared AMBER and archival mid-infrared
MIDI visibilities, we employed both geometric and temperature-gradient
models.
Results: To characterize the disk size, we first fitted
geometric models consisting of a stellar point source, a ring-shaped
disk, and a halo structure to the visibilities. In the H and K bands,
we measured ring-fit radii of 0.73 ± 0.03 mas (corresponding to 0.095
± 0.018 AU for a distance of 130 pc) and 0.85 ± 0.07 mas (0.111
± 0.026 AU), respectively. This K-band radius is approximately
two times larger than the dust sublimation radius of ≈0.05 AU
expected for a dust sublimation temperature of 1500 K and gray dust
opacities, but approximately agrees with the prediction of models
including backwarming (namely a radius of ≈0.12 AU). The derived
temperature-gradient models suggest that the disk is approximately
face-on consisting of two disk components with a gap between star and
disk. The inner disk component has a temperature close to the dust
sublimation temperature and a quite narrow intensity distribution with
a radial extension from 0.11 AU to 0.14 AU.
Conclusions: Both
our geometric and temperature-gradient models suggest that the T Tauri
star S CrA N is surrounded by a circumstellar disk that is truncated
at an inner radius of ≈ 0.11 AU. The narrow extension of the inner
temperature-gradient disk component implies that there is a hot inner
rim. Based on observations made with ESO telescopes at the La Silla
Paranal Observatory under program IDs 081.C-0272(A), 083.C-0236(C).
Title: The 2012 interferometric imaging beauty contest
Authors: Baron, Fabien; Cotton, William D.; Lawson, Peter R.; Ridgway,
Steve T.; Aarnio, Alicia; Monnier, John D.; Hofmann, Karl-Heinz;
Schertl, Dieter; Weigelt, Gerd; Thiébaut, Eric; Soulez, Férréol;
Mary, David; Millour, Florentin; Vannier, Martin; Young, John; Elias,
Nicholas M.; Schmitt, Henrique R.; Rengaswamy, Sridharan
Bibcode: 2012SPIE.8445E..1EB
Altcode: 2012arXiv1207.7141B
We present the results of the fifth Interferometric Imaging Beauty
Contest. The contest consists in blind imaging of test data sets derived
from model sources and distributed in the OIFITS format. Two scenarios
of imaging with CHARA/MIRC-6T were offered for reconstruction: imaging
a T Tauri disc and imaging a spotted red supergiant. There were eight
different teams competing this time: Monnier with the software package
MACIM; Hofmann, Schertl and Weigelt with IRS; Thiebaut and Soulez with
MiRA ; Young with BSMEM; Mary and Vannier with MIROIRS; Millour and
Vannier with independent BSMEM and MiRA entries; Rengaswamy with an
original method; and Elias with the radio-astronomy package CASA. The
contest model images, the data delivered to the contestants and the
rules are described as well as the results of the image reconstruction
obtained by each method. These results are discussed as well as the
strengths and limitations of each algorithm.
Title: AMBER and CRIRES observations of the binary sgB[e] star HD
327083: evidence of a gaseous disc traced by CO bandhead emission
Authors: Wheelwright, H. E.; de Wit, W. J.; Weigelt, G.; Oudmaijer,
R. D.; Ilee, J. D.
Bibcode: 2012A&A...543A..77W
Altcode: 2012arXiv1206.6252W
Context. HD 327083 is a supergiant B[e] star that
forms a binary system with an orbital semi-major axis of approximately
1.7 AU.
Aims: Our previous observations using the VLTI
and AMBER in the medium resolution K-band mode spatially resolved
the environment of HD 327083. The continuum visibilities obtained
indicate the presence of a circumbinary disc. CO bandhead emission
was also observed. However, due to the limited spectral resolution
of the previous observations, the kinematic structure of the emitting
material could not be constrained. In this paper, we address this and
probe the source of the CO emission with high spectral resolution
and spatial precision.
Methods: To determine the properties
and kinematics of its CO emitting region, we have observed HD 327083
with high spectral resolution (25 and 6 km s-1) using AMBER
and CRIRES. The observations are compared to kinematical models to
constrain the source of the emission.
Results: The multi-epoch
AMBER spectra obtained over 5 months contain no evidence that the CO
1st overtone emission of HD 327083 is variable. This indicates that the
structure of the emitting region is not strongly dependent on orbital
phase. It is shown that the CO bandhead emission can be reproduced using
a model of a Keplerian disc with an inclination and size consistent
with our previous VLTI observations. The model is compared to AMBER
differential phase measurements, which have a precision as high as ~30
μas. A differential phase signal corresponding to 0.15 mas (~5σ)
is seen over the bandhead emission, which is in excellent agreement
with the model that fits the CRIRES observations. In comparison, a
model of an equatorial outflow, as envisaged in the standard sgB[e]
scenario, does not reproduce the observations well.
Conclusions:
We present a direct test of the circumstellar kinematics of the binary
sgB[e] star HD 327083 using both spatial and spectral information. The
excellent agreement between the disc model and observations in the
spatial and spectral domains is compelling evidence that the CO bandhead
emission of HD 327083 originates in a circumbinary Keplerian disc. In
contrast, the model of an equatorial outflow cannot reproduce the
observations well. This suggests that the standard sgB[e] scenario is
not applicable to HD 327083, which supports the hypothesis that the B[e]
behaviour of HD 327083 is due to binarity. Based on data obtained
at the European Southern Observatory, Paranal, Chile via the observing
programmes 385.D-0513 and 087.D-0889.
Title: Perspective of imaging in the mid-infrared at the Very Large
Telescope Interferometer
Authors: Lopez, B.; Lagarde, S.; Antonelli, P.; Jaffe, W.; Petrov, R.;
Venema, L.; Robbe-Dubois, Sylvie; Bettonvil, F.; Berio, P.; Navarro,
R.; Graser, U.; Beckman, U.; Weigelt, G.; Vakili, F.; Henning, T.;
Gonzales, J. -C.; Wolf, S.; Bailet, C.; Behrend, J.; Bresson, Y.;
Chesneau, O.; Clausse, J. M.; Connot, C.; Dugué, M.; Fantei, Y.;
Elswijk, E.; Hanenburg, H.; Hofmann, K. H.; Heininger, M.; ter Horst,
R.; Hron, J.; Kragt, J.; Tromp, N.; Agocs, T.; Kroes, G.; Laun,
W.; Leinert, Ch.; Lehmitz, M.; Matter, A.; Menut, J. L.; Millour,
F.; Neumann, U.; Nussbaum, E.; Ottogalli, S.; Pott, J. -U.; Rigal,
F.; Roussel, A.; Schertl, D.; Vannier, M.; Wagner, K.; Mellein, M.;
Kroener, T.; Mauclert, N.; Girard, P.; Lagarde, G. M.; Mosoni, L.;
Jasko, A.; Glindemann, A.; Phan Duc, T.; Finger, G.; Ives, D.; Jakob,
G.; Percheron, I.; Avila, G.; Palsa, R.; Pozna, E.; Lizon, J. L.;
Lucuix, Ch.; Menardi, S.; Haguenauer, P.; Gitton, P.; Morel, S.;
Gonté, F.; Jolley, P.; Rupprecht, G.; Bourget, P.; Delplancke, F.;
Mehrgan, L.; Stegmeier, J.; van Belle, G.; Richichi, A.; Moorwood, A.
Bibcode: 2012SPIE.8445E..0RL
Altcode:
MATISSE is a mid-infrared spectro-interferometer combining the
beams of up to four Unit Telescopes or Auxiliary Telescopes of the
Very Large Telescope Interferometer (VLTI) of the European Southern
Observatory. MATISSE will constitute an evolution of the two-beam
interferometric instrument MIDI. New characteristics present in MATISSE
will give access to the mapping and the distribution of the material,
the gas and essentially the dust, in the circumstellar environments by
using the mid-infrared band coverage extended to L, M and N spectral
bands. The four beam combination of MATISSE provides an efficient
uv-coverage: 6 visibility points are measured in one set and 4 closure
phase relations which can provide aperture synthesis images in the
mid-infrared spectral regime. We give an overview of the instrument
including the expected performances and a view of the Science Case. We
present how the instrument would be operated. The project involves the
collaborations of several agencies and institutes: the Observatoire de
la Côte d’Azur of Nice and the INSU-CNRS in Paris, the Max Planck
Institut für Astronomie of Heidelberg; the University of Leiden and
the NOVA-ASTRON Institute of Dwingeloo, the Max Planck Institut für
Radioastronomie of Bonn, the Institut für Theoretische Physik und
Astrophysik of Kiel, the Vienna University and the Konkoly Observatory.
Title: The complexity of parsec-scaled dusty tori in AGN
Authors: Tristram, K. R. W.; Schartmann, M.; Burtscher, L.;
Meisenheimer, K.; Jaffe, W.; Kishimoto, M.; Hönig, S. F.; Weigelt, G.
Bibcode: 2012JPhCS.372a2035T
Altcode: 2012arXiv1204.2823T
Warm gas and dust surround the innermost regions of active galactic
nuclei (AGN). They provide the material for accretion onto the
super-massive black hole and they are held responsible for the
orientation-dependent obscuration of the central engine. The AGN-heated
dust distributions turn out to be very compact with sizes on scales
of about a parsec in the mid-infrared. Only infrared interferometry
currently provides the necessary angular resolution to directly study
the physical properties of this dust. Size estimates for the dust
distributions derived from interferometric observations can be used to
construct a size-luminosity relation for the dust distributions. The
large scatter about this relation suggests significant differences
between the dust tori in the individual galaxies, even for nuclei of
the same class of objects and with similar luminosities. This questions
the simple picture of the same dusty doughnut in all AGN. The Circinus
galaxy is the closest Seyfert 2 galaxy. Because its mid-infrared
emission is well resolved interferometrically, it is a prime target for
detailed studies of its nuclear dust distribution. An extensive new
interferometric data set was obtained for this galaxy. It shows that
the dust emission comes from a very dense, disk-like structure which is
surrounded by a geometrically thick, similarly warm dust distribution
as well as significant amounts of warm dust within the ionisation cone.
Title: Probing the innermost dusty structure in AGN with mid-IR and
near-IR interferometers
Authors: Kishimoto, M.; Hönig, S. F.; Antonucci, R.; Barvainis, R.;
Kotani, T.; Millour, F.; Tristram, K. R. W.; Weigelt, G.
Bibcode: 2012JPhCS.372a2033K
Altcode: 2012arXiv1204.4871K
With mid-IR and near-IR long-baseline interferometers, we are now
mapping the radial distribution of the dusty accreting material in
AGNs at sub-pc scales. We currently focus on Type 1 AGNs, where the
innermost region is unobscured and its intrinsic structure can be
studied directly. As a first systematic study of Type 1s, we obtained
mid-/near-IR data for small samples over ~3-4 orders of magnitudes
in UV luminosity L of the central engine. Here we effectively trace
the structure by observing dust grains that are radiatively heated
by the central engine. Consistent with a naive expectation for such
dust grains, the dust sublimation radius Rin is in fact
empirically known to be scaling with L1/2 from the near-IR
reverberation measurements, and this is also supported by our near-IR
interferometry. Utilizing this empirical relationship, we normalize the
radial extent by Rin and eliminate the simple L1/2
scaling for a direct comparison over the samples. We then find that, in
the mid-IR, the overall size in units of Rin seems to become
more compact in higher luminosity sources. More specifically, the mid-IR
brightness distribution is rather well described by a power-law, and
this power-law becomes steeper in higher luminosity objects. The near-IR
flux does not seem to be a simple inward extrapolation of the mid-IR
power-law component toward shorter wavelengths, but it rather comes from
a little distinct brightness concentration at the inner rim region of
the dust distribution. Its structure is not well constrained yet, but
there is tentative evidence that this inner near-IR-emitting structure
has a steeper radial distribution in jet-launching objects. All these
should be scrutinized with further observations.
Title: VLTI/AMBER differential interferometry of the broad-line
region of the quasar 3C273
Authors: Petrov, Romain G.; Millour, Florentin; Lagarde, Stéphane;
Vannier, Martin; Rakshit, Suvendu; Marconi, Alessandro; weigelt, Gerd
Bibcode: 2012SPIE.8445E..0WP
Altcode: 2014arXiv1410.3108P
Unveiling the structure of the Broad Line Region (BLR) of AGNs is
critical to understand the quasar phenomenon. Resolving a few BLRs by
optical interferometry will bring decisive information to confront,
complement and calibrate the reverberation mapping technique, seed
of the mass-luminosity relation in quasars. BLRs are much smaller
than the angular resolution of the VLT and Keck interferometers
and they can be resolved only by differential interferometry very
accurate measurements of differential visibility and phase. The latest
yields the photocenter variation with λ, and constrains the size,
position and velocity law of various regions of the BLR. AGNs are
below the magnitude limit for spectrally resolved interferometry set
by currently available fringe trackers. A new “blind” observation
method and a data processing based on the accumulation of 2D Fourier
power and cross spectra permitted us the first spectrally resolved
interferometric observation of a BLR, on the K=10 quasar 3C273. A
careful bias analysis is still in progress, but we report strong
evidence that, as the baseline increases, the differential visibility
decreases in the Paα line. Combined with a differential
phase certainly smaller than 3°, this yields an angular radius of
the BLR larger than 0.4 milliarcseconds, or 1000 light days at the
distance of 3C273, much larger than the reverberation mapping radius
of 300 light days. Explaining the coexistence of these two different
scales, and possibly structures and mechanisms, implies very new
insights about the BLR of 3C273.
Title: On the Nature of the Herbig B[e] Star Binary System V921
Scorpii: Geometry and Kinematics of the Circumprimary Disk on
Sub-AU Scales
Authors: Kraus, Stefan; Calvet, Nuria; Hartmann, Lee; Hofmann,
Karl-Heinz; Kreplin, Alexander; Monnier, John D.; Weigelt, Gerd
Bibcode: 2012ApJ...752...11K
Altcode: 2012arXiv1204.1969K
V921 Scorpii is a close binary system (separation 0farcs025) showing
the B[e]-phenomenon. The system is surrounded by an enigmatic
bipolar nebula, which might have been shaped by episodic mass-loss
events, possibly triggered by dynamical interactions between the
companion and the circumprimary disk. In this paper, we investigate
the spatial structure and kinematics of the circumprimary disk,
with the aim to obtain new insights into the still strongly debated
evolutionary stage. For this purpose, we combine, for the first time,
infrared spectro-interferometry (VLTI/AMBER, λ/Δλ = 12, 000) and
spectro-astrometry (VLT/CRIRES, λ/Δλ = 100, 000), which allows us
to study the AU-scale distribution of circumstellar gas and dust with
an unprecedented velocity resolution of 3 km s-1. Using
a model-independent photocenter analysis technique, we find that
the Brγ-line-emitting gas rotates in the same plane as the dust
disk. We can reproduce the wavelength-differential visibilities and
phases and the double-peaked line profile using a Keplerian-rotating
disk model. The derived mass of the central star is 5.4 ± 0.4 M
⊙ · (d/1150 pc), which is considerably lower than
expected from the spectral classification, suggesting that V921 Sco
might be more distant (d ~ 2 kpc) than commonly assumed. Using the
geometric information provided by our Brγ spectro-interferometric
data and Paschen, Brackett, and Pfund line decrement measurements in
61 hydrogen recombination line transitions, we derive the density
of the line-emitting gas (Ne = (2-6) × 1019
m-3). Given that our measurements can be reproduced with
a Keplerian velocity field without an outflowing velocity component
and the non-detection of age-indicating spectroscopic diagnostics,
our study provides new evidence for the pre-main-sequence nature of
V921 Sco. Based on observations made with ESO telescopes at the
Paranal Observatory under the open-time program ID 084.C-0668(A, B)
and with the Magellan Clay telescope.
Title: On the influence of the companion star in Eta Carinae: 2D
radiative transfer modelling of the ultraviolet and optical spectra
Authors: Groh, Jose H.; Hillier, D. John; Madura, Thomas I.; Weigelt,
Gerd
Bibcode: 2012MNRAS.423.1623G
Altcode: 2012arXiv1204.1963G; 2012MNRAS.tmp.3024G
We present two-dimensional (2D) radiative transfer modelling of the
Eta Carinae binary system accounting for the presence of a wind-wind
collision (WWC) cavity carved in the optically thick wind of the
primary star. By comparing synthetic line profiles with spectra
obtained with the Hubble Space Telescope/Space Telescope Imaging
Spectrograph near apastron, we show that the WWC cavity has a strong
influence on multi-wavelength diagnostics. This influence is regulated
by the modification of the optical depth in the continuum and spectral
lines. We find that Hα, Hβ and Fe II lines are the most affected by
the WWC cavity, since they form over a large volume of the stellar
wind of the primary. These spectral lines depend on latitude and
azimuth since, according to the orientation of the cavity, different
velocity regions of a spectral line are affected. For 2D models with
orientation corresponding to orbital inclination angle ? and longitude
of periastron ?, the blueshifted and zero-velocity regions of the
line profiles are the most affected by the cavity. These orbital
orientations are required to simultaneously fit the ultraviolet (UV)
and optical spectrum of Eta Car around apastron, for a half-opening
angle of the cavity in the range of 50°-70°. We find that the excess
P Cygni absorption seen in Hα, Hβ and optical Fe II lines in 1D
spherical models becomes much weaker or absent in the 2D cavity models,
in agreement with the observations. The observed UV spectrum of Eta Car
is strongly dominated by absorption of Fe II lines that are superbly
reproduced by our 2D models when the presence of the low-density WWC
cavity is taken into account. Small discrepancies still remain, as the
P Cygni absorption of Hγ and Hδ is overestimated by our 2D models at
apastron. We suggest that photoionization of the wind of the primary
by the hot companion star is responsible for the weak absorption seen
in these lines. Our CMFGEN models indicate that the primary star has a
mass-loss rate of 8.5 × 10-4 M⊙ yr-1
and wind terminal velocity of 420 km s-1 around the 2000-2001
apastron. Based on observations made with the Hubble Space Telescope
Imaging Spectrograph under programmes 9420 and 9973.
Title: VLTI/AMBER observations of the Seyfert nucleus of NGC 3783
Authors: Weigelt, G.; Hofmann, K. -H.; Kishimoto, M.; Hönig, S.;
Schertl, D.; Marconi, A.; Millour, F.; Petrov, R.; Fraix-Burnet, D.;
Malbet, F.; Tristram, K.; Vannier, M.
Bibcode: 2012A&A...541L...9W
Altcode: 2012arXiv1204.6122W
Context. The putative tori surrounding the accretion disks of active
galactic nuclei (AGNs) play a fundamental role in the unification
scheme of AGNs. Infrared long-baseline interferometry allows us
to study the inner dust distribution in AGNs with unprecedented
spatial resolution over a wide infrared wavelength range.
Aims: Near- and mid-infrared interferometry is used to investigate
the milli-arcsecond-scale dust distribution in the type 1.5 Seyfert
nucleus of NGC 3783.
Methods: We observed NGC 3783 with the
VLTI/AMBER instrument in the K-band and compared our observations
with models.
Results: From the K-band observations, we derive
a ring-fit torus radius of 0.74 ± 0.23 mas or 0.16 ± 0.05 pc. We
compare this size with infrared interferometric observations of other
AGNs and UV/optical-infrared reverberation measurements. For the
interpretation of our observations, we simultaneously model our near-
and mid-infrared visibilities and the spectral energy distribution (SED)
with a temperature/density-gradient model including an additional inner
hot 1400 K ring component. Based on observations made with ESO
telescopes at Paranal Observatory under programme IDs 083.B-0212(A)
and 087.B-0578(A).
Title: Near-infrared interferometric observation of the Herbig Ae
star HD 144432 with VLTI/AMBER
Authors: Chen, L.; Kreplin, A.; Wang, Y.; Weigelt, G.; Hofmann,
K. -H.; Kraus, S.; Schertl, D.; Lagarde, S.; Natta, A.; Petrov, R.;
Robbe-Dubois, S.; Tatulli, E.
Bibcode: 2012A&A...541A.104C
Altcode: 2012arXiv1203.6240C
Aims: We study the sub-AU-scale circumstellar environment of the
Herbig Ae star HD 144432 with near-infrared VLTI/AMBER observations
to investigate the structure of its inner dust disk.
Methods:
The interferometric observations were carried out with the AMBER
instrument in the H and K band. We interpret the measured H- and
K-band visibilities, the near- and mid-infrared visibilities from the
literature, and the spectral energy distribution (SED) of HD 144432 by
using geometric ring models and ring-shaped temperature-gradient disk
models with power-law temperature distributions.
Results: We
derive a K-band ring-fit radius of 0.17 ± 0.01 AU and an H-band radius
of 0.18 ± 0.01 AU (for a distance of 145 pc). This measured K-band
radius of ~0.17 AU lies in the range between the dust sublimation radius
of ~0.13 AU (predicted for a dust sublimation temperature of 1500 K and
gray dust) and the prediction of models including backwarming (~0.27
AU). We find that an additional extended halo component is required in
both the geometric and temperature-gradient modeling. In the best-fit
temperature-gradient model, the disk consists of two components. The
inner part of the disk is a thin ring with an inner radius of ~0.21 AU,
a temperature of ~1600 K, and a ring thickness ~0.02 AU. The outer
part extends from ~1 AU to ~10 AU with an inner temperature of ~400
K. We find that the disk is nearly face-on with an inclination angle
of <28°.
Conclusions: Our temperature-gradient modeling
suggests that the near-infrared excess is dominated by emission from
a narrow, bright rim located at the dust sublimation radius, while an
extended halo component contributes ~6% to the total flux at 2 μm. The
mid-infrared model emission has a two-component structure with ~20%
of the flux originating from the inner ring and the rest from the outer
parts. This two-component structure is indicative of a disk gap, which
is possibly caused by the shadow of a puffed-up inner rim. Based
on observations made with ESO telescopes at Paranal Observatory under
program ID 083.D-0224(C) and 085.C-0126(A).
Title: On the Nature of the Herbig B[e] Star Binary System V921
Scorpii: Discovery of a Close Companion and Relation to the
Large-scale Bipolar Nebula
Authors: Kraus, Stefan; Calvet, Nuria; Hartmann, Lee; Hofmann,
Karl-Heinz; Kreplin, Alexander; Monnier, John D.; Weigelt, Gerd
Bibcode: 2012ApJ...746L...2K
Altcode: 2012arXiv1201.2420K
Belonging to the group of B[e] stars, V921 Scorpii is associated with
a strong infrared excess and permitted and forbidden line emission,
indicating the presence of low- and high-density circumstellar gas
and dust. Many aspects of V921 Sco and other B[e] stars still remain
mysterious, including their evolutionary state and the physical
conditions resulting in the class-defining characteristics. In
this Letter, we employ Very Large Telescope Interferometer/AMBER
spectro-interferometry in order to reconstruct high-resolution
(λ/2B = 0farcs0013) model-independent interferometric images for
three wavelength bands around 1.65, 2.0, and 2.3 μm. In our images,
we discover a close (25.0 ± 0.8 mas, corresponding to ~29 ± 0.9 AU
at 1.15 kpc) companion around V921 Sco. Between two epochs in 2008 and
2009, we measure orbital motion of ~7°, implying an orbital period of
~35 years (for a circular orbit). Around the primary star, we detect
a disk-like structure with indications for a radial temperature
gradient. The polar axis of this AU-scale disk is aligned with the
arcminute-scale bipolar nebula in which V921 Sco is embedded. Using
Magellan/IMACS imaging, we detect multi-layered arc-shaped substructure
in the nebula, suggesting episodic outflow activity from the system
with a period of ~25 years, roughly matching the estimated orbital
period of the companion. Our study supports the hypothesis that the
B[e] phenomenon is related to dynamical interaction in a close binary
system. Based on observations made with ESO telescopes at the
Paranal Observatory under the open-time programme ID 081.C-0706(A-D)
and with the Magellan Baade and Clay telescopes.
Title: Resolving the innermost dusty accretion in the brightest Type
1 AGN with the CHARA array
Authors: Kishimoto, Makoto; Barvainis, Richard; Antonucci, Robert;
Hoenig, Sebastian; Millour, Florentin; Tristram, Konrad; Weigelt, Gerd
Bibcode: 2012noao.prop..187K
Altcode:
We believe that we have finally started to spatially resolve and
quantify the innermost dusty structure in AGN tori with long-baseline
interferometry in the infrared. A major goal here is to see if
the inner radial distribution of the accreting material is closely
related to the mode of the central engine: based on the results so
far, this might indeed be the case. However, our previous and on-going
observations have a big limitation in the baseline length, with which
we can only marginally resolve the structure, leaving ambiguity in the
interpretation of the data. Here we propose to break this limit by
using the very long baselines offered in the CHARA array. This will
test our fundamental picture and conclusively measure the innermost
dusty structure in the brightest Type 1 AGN.
Title: Spatially resolving the outer atmosphere of the M giant BK
Virginis in the CO first overtone lines with VLTI/AMBER
Authors: Ohnaka, K.; Hofmann, K. -H.; Schertl, D.; Weigelt, G.;
Malbet, F.; Massi, F.; Meilland, A.; Stee, Ph.
Bibcode: 2012A&A...537A..53O
Altcode: 2011arXiv1111.5987O
Context. The mass-loss mechanism in normal K-M giant stars with small
variability amplitudes is not yet understood, although the majority
among red giant stars are precisely of this type.
Aims: We
present high-spatial and high-spectral resolution observations of the
M7 giant BK Vir with AMBER at the Very Large Telescope Interferometer
(VLTI). Our aim is to probe the physical properties of the outer
atmosphere by spatially resolving the star in the individual CO
first overtone lines.
Methods: BK Vir was observed between
2.26 and 2.31 μm using the 16-32-48 m telescope configuration with
an angular resolution of 9.8 mas and a spectral resolution of 12
000.
Results: The uniform-disk diameters observed in the CO
first overtone lines are 12 - 31% larger than those measured in
the continuum. We also detected asymmetry in the CO line-forming
region, which manifests itself as non-zero/non-π differential and
closure phases. The data taken 1.5 months apart show possible time
variation on a spatial scale of 30 mas (corresponding to 3 × stellar
diameter) at the CO band head. Comparison of the observed data with
the MARCS photospheric model shows that whereas the observed CO line
spectrum can be satisfactorily reproduced by the model, the angular
sizes observed in the CO lines are much larger than predicted by
the model. Our model with two additional CO layers above the MARCS
photosphere reproduces the observed spectrum and interferometric data
in the CO lines simultaneously. This model suggests that the inner
CO layer at ~1.2 R⋆ is very dense and warm with a CO
column density of ~1022 cm-2 and temperatures
of 1900 - 2100 K, while the outer CO layer at 2.5-3.0 R⋆
is characterized by column densities of 1019-1020
cm-2 and temperatures of 1500 - 2100 K.
Conclusions:
Our AMBER observations of BK Vir have spatially resolved the extended
molecular outer atmosphere of a normal M giant in the individual CO
lines for the first time. The temperatures derived for the CO layers are
higher than, or equal to, the uppermost layer of the MARCS photospheric
model, implying the operation of some heating mechanism in the outer
atmosphere. This study also illustrates that testing photospheric models
only with the spectra of strong molecular or atomic features can be
misleading. Based on AMBER observations made with the Very Large
Telescope Interferometer of the European Southern Observatory. Program
ID: 081.D-0233(A) (AMBER Guaranteed Time Observation).
Title: High-Resolution Studies of Eta Carinae's Ejecta and Stellar
Wind
Authors: Weigelt, Gerd; Kraus, Stefan
Bibcode: 2012ASSL..384..129W
Altcode:
Hubble Space Telescope observations and interferometric measurements
provide unique insights into the small-scale structure of η Car's
circumstellar ejecta and its extreme, optically thick, aspherical
stellar wind. We discuss speckle interferometric imaging and HST
images of η Car's ejecta in the inner 1 arcsec. We also review
the first infrared long-baseline spectro-interferometry with high
spatial resolution of 5 mas and high spectral resolution. Infrared
interferometry allows us, for the first time, to study the strong
wavelength dependence of η Car's non-spherical wind structure within
emission lines.
Title: Resolving the circumstellar environment of the B[e] star V921
Scorpii in the near-infrared with VLTI/AMBER
Authors: Kreplin, A.; Kraus, S.; Hofmann, K. -H.; Schertl, D.; Weigelt,
G.; Driebe, T.
Bibcode: 2012A&A...537A.103K
Altcode:
Aims: We study the AU-scale circumstellar environment of the
unclassified B[e] star V921 Sco in the near-infrared. For interpreting
the observations, we employ temperature-gradient disk models.
Methods: Using the near-infrared beam combiner instrument
AMBER, we recorded spectrally dispersed (spectral resolution R =
35) interferograms in the H and K bands. To obtain an improved
calibration of the visibilities, we developed a method that is able to
equalize the histograms of the optical path difference of target and
calibrator. We fit temperature-gradient disk models to the visibilities
and spectral energy distribution (SED) to analyze the circumstellar
dust geometry.
Results: We derived a geometric ring-fit radius
of 2.10 ± 0.16 mas in the K band. If we adopt the distance of 1150
± 150 pc reported elsewhere, we obtain a ring-fit radius of 2.4 AU,
which is slightly smaller than the 3.5 AU dust sublimation radius
predicted by the size-luminosity relation. The fitted H-band radius of
1.61 ± 0.23 mas (1.85 AU) is found to be more compact than the K-band
radius. The best-fit temperature-gradient disk model has an inner disk
radius of ~1.45 AU, an inner-edge disk temperature T0 = 1533
K, and a temperature-gradient exponent q = 0.46 suggesting a flared
disk geometry.
Conclusions: The distance and luminosity of V921
Sco are not well known. If we assume a distance of 1150 ± 150 pc, we
derive a ring-fit radius of ~2.4 AU, which is approximately consistent
with the computed temperature-gradient disk model with inner and outer
ring radii of 1.45 and 8.5 AU, respectively. If the inner radius of
V921 Sco is more compact than the sublimation radius, this compact
observed size can be explained by emitting material (e.g., a gaseous
disk) inside the dust sublimation radius, as suggested for several
other B[e] stars. Based on observations made with ESO telescopes
at Paranal Observatory under program ID (MPG-VISA GTO): 079.C-0212(A).
Title: Mapping the radial structure of AGN tori
Authors: Kishimoto, M.; Hönig, S. F.; Antonucci, R.; Millour, F.;
Tristram, K. R. W.; Weigelt, G.
Bibcode: 2011A&A...536A..78K
Altcode: 2011arXiv1110.4290K
We present mid-IR interferometric observations of six type 1 AGNs
at multiple baseline lengths ranging from 27 m to 130 m, reaching
high angular resolutions up to λ/B ~ 0.02 arcsec. For two of the
targets, we have simultaneous near-IR interferometric measurements
as well, taken within a week. We find that all the objects are
partially resolved at long baselines in these IR wavelengths. The
multiple-baseline data directly probe the radial distribution of
the material on sub-pc scales. We show that for our sample, which
is small but spans over ~2.5 orders of magnitudes in the UV/optical
luminosity L of the central engine, the radial distribution clearly and
systematically changes with luminosity. The brightness distribution
at a given mid-IR wavelength seems to be rather well described by
a power law, which makes a simple Gaussian or ring size estimation
quite inadequate. In this case, a half-light radius R1/2
can be used as a representative size. We show that the higher
luminosity objects become more compact in normalized half-light radii
R1/2/Rin in the mid-IR, where Rin is
the dust sublimation radius empirically given by the L1/2
fit of the near-IR reverberation radii. This means that, contrary to
previous studies, the physical mid-IR emission size (e.g. in pc) is
not proportional to L1/2, but increases with L much more
slowly. With our current datasets, we find that R1/2 ∝
L0.21 ± 0.05 at 8.5 μm, and R1/2 nearly constant
at 13 μm. The derived size information also seems to correlate with
the properties of the total flux spectrum, in particular the smaller
R1/2/Rin objects having bluer mid-IR spectral
shape. We use a power-law temperature/density gradient model as a
reference, and infer that the radial surface density distribution
of the heated dust grains at a radius r changes from a steep
~r-1 structure in high luminosity objects to a shallower
~r0 structure in those of lower luminosity. The inward
dust temperature distribution does not seem to smoothly reach the
sublimation temperature - on the innermost scale of ~Rin,
a relatively low temperature core seems to co-exist with a slightly
distinct brightness concentration emitting roughly at the sublimation
temperature. Appendices are available in electronic form at http://www.aanda.org
Title: Near-Infrared Imaging Polarimetry of Bipolar Proto-planetary
Nebulae
Authors: Murakawa, K.; Driebe, T.; Hofmann, K.; Meixner, M.; Ohnaka,
K.; Oya, S.; Schertl, D.; Weigelt, G.; Ueta, T.
Bibcode: 2011ASPC..449..327M
Altcode:
We present results of radiative transfer modeling of two bipolar
proto-planetary nebulae based on the data archives of HST/NICMOS
imaging polarimetry. We constrained the model parameters by fitting the
spectral energy distributions, the intensity and polarization images,
and assumed multiple grain models in different geometry space. From
our sample, we found that (1) model geometries with a disk reproduce
the bipolar appearance with a narrow waist, (2) grains in the bipolar
lobes have submicron sizes, but ∼10μm or larger sizes are expected
in the equatorial region, and (3) the grain sizes in the disk correlate
to the disk geometry, but not the stellar temperature, luminosity,
or lobe shape. Our results agree with the disk/reservoir hypothesis
in PN shaping.
Title: Status report on the Large Binocular Telescope's ARGOS
ground-layer AO system
Authors: Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Beckmann, U.;
Bonaglia, M.; Boose, Y.; Borelli, J. L.; Bluemchen, T.; Carbonaro,
L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich,
M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein,
H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx,
J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.;
Schwab, C.; Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.
Bibcode: 2011SPIE.8149E..0JH
Altcode: 2011SPIE.8149E..18H
ARGOS, the laser-guided adaptive optics system for the Large Binocular
Telescope (LBT), is now under construction at the telescope. By
correcting atmospheric turbulence close to the telescope, the system is
designed to deliver high resolution near infrared images over a field
of 4 arc minute diameter. Each side of the LBT is being equipped with
three Rayleigh laser guide stars derived from six 18 W pulsed green
lasers and projected into two triangular constellations matching the
size of the corrected field. The returning light is to be detected by
wavefront sensors that are range gated within the seeing-limited depth
of focus of the telescope. Wavefront correction will be introduced by
the telescope's deformable secondary mirrors driven on the basis of
the average wavefront errors computed from the respective guide star
constellation. Measured atmospheric turbulence profiles from the site
lead us to expect that by compensating the ground-layer turbulence,
ARGOS will deliver median image quality of about 0.2 arc sec across
the JHK bands. This will be exploited by a pair of multi-object
near-IR spectrographs, LUCIFER1 and LUCIFER2, with 4 arc minute field
already operating on the telescope. In future, ARGOS will also feed two
interferometric imaging instruments, the LBT Interferometer operating
in the thermal infrared, and LINC-NIRVANA, operating at visible and
near infrared wavelengths. Together, these instruments will offer very
broad spectral coverage at the diffraction limit of the LBT's combined
aperture, 23 m in size.
Title: ARGOS - the Laser Star Adaptive Optics for LBT
Authors: Rabien, S.; Barl, L.; Beckmann, U.; Blümchen, T.; Bonaglia,
M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro, L.; Conot,
C.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito,
S.; Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green,
R.; Haug, M.; Lloyd Hart, M.; Hubbard, P.; Kanneganti, S.; Kulas,
M.; Noenickx, J.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Rix,
H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel, M.;
Weigelt, G.; Ziegleder, J.; Orban de Xivry, G.
Bibcode: 2011aoel.confE..51R
Altcode:
We will present the design and status of ARGOS - the Laser Guide
Star adaptive optics facility for the Large Binocular Telescope. By
projecting a constellation of multiple laser guide stars above each of
the 8.4m primary mirrors of the LBT, ARGOS in its ground layer mode
will enable a wide field adaptive optics correction for multi object
spectroscopy. ARGOS implements high power pulsed green lasers and makes
use of Rayleigh scattering for the guide star creation. The geometric
relations of this setup in guide star height vs. primary diameter
are quite comparable to an ELT with sodium guide stars. The use of
LBT's adaptive secondary mirror, gated wavefront sensors, a prime
focus calibration system and the laser constellation shows several
aspects that may be used as pathfinding technology for the planned
ELTs. In already planned upgrade steps with a hybrid Sodium-Rayleigh
combination ARGOS will enable MCAO and MOAO implementations at LBT
allowing unique astronomical observations.
Title: The Large Binocular Telescope's ARGOS ground-layer AO system
Authors: Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Bechmann, U.;
Bonaglia, M.; Boose, Y.; Borelli, J.; Bluemchen, T.; Carbonaro,
L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich,
M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein,
H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx,
J.; Orban de Xivry, G.; Qirrenback, A.; Rademacher, M.; Schwab, C.;
Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.
Bibcode: 2011amos.confE..59H
Altcode:
ARGOS, the laser-guided adaptive optics system for the Large Binocular
Telescope (LBT), is now under construction at the telescope. By
correcting atmospheric turbulence close to the telescope, the system
is designed to deliver high resolution near infrared images over a
field of 4 arc minute diameter. ARGOS is motivated by a successful
prototype multi-laser guide star system on the 6.5 m MMT telescope,
results from which are presented in this paper. At the LBT, each side
of the twin 8.4 m aperture is being equipped with three Rayleigh
laser guide stars derived from six 18 W pulsed green lasers and
projected into two triangular constellations matching the size of the
corrected field. The returning light is to be detected by wavefront
sensors that are range gated within the seeinglimited depth of focus
of the telescope. Wavefront correction will be introduced by the
telescope’s deformable secondary mirrors driven on the basis of
the average wavefront errors computed from the respective guide star
constellation. Measured atmospheric turbulence profiles from the site
lead us to expect that by compensating the ground-layer turbulence,
ARGOS will deliver median image quality of about 0.2 arc sec in the
near infrared bands. This will be exploited by a pair of multi-object
near-IR spectrographs, LUCI1 and LUCI2, each with 4 arc minute field
already operating on the telescope. In future, ARGOS will also feed two
interferometric imaging instruments, the LBT Interferometer operating
in the thermal infrared, and LINC-NIRVANA, operating at visible and
near infrared wavelengths. Together, these instruments will offer
very broad spectral coverage at the diffraction limit of the LBT’s
combined aperture, 23 m in size.
Title: Mid-infrared interferometry of the massive young stellar
object NGC 2264 IRS 1
Authors: Grellmann, R.; Ratzka, T.; Kraus, S.; Linz, H.; Preibisch,
T.; Weigelt, G.
Bibcode: 2011A&A...532A.109G
Altcode: 2011arXiv1107.0928G
Context. The optically invisible infrared-source NGC 2264 IRS 1
lying north of the Cone Nebula is thought to be a massive young
stellar object (~10 M⊙). Although strong infrared excess
clearly shows that the central object is surrounded by large amounts of
circumstellar material, no information about the spatial distribution
of this circumstellar material has been available until now.
Aims: We used the ESO Very Large Telescope Interferometer to perform
long-baseline interferometric observations of NGC 2264 IRS 1 in
the mid-infrared regime. Our observations resolve the circumstellar
material around NGC 2264 IRS 1, provide the first direct measurement
of the angular size of the mid-infrared emission, and yield direct
constraints on the spatial distribution of the dust.
Methods:
We analyze the spectrally dispersed interferometric data taken with
MIDI at two different position angles and baseline lengths. We use
different approaches (a geometrical model, a temperature-gradient
model, and radiative transfer models) to jointly model the observed
interferometric visibilities and the spectral energy distribution.
Results: The derived visibility values between ~0.02 and ~0.3 show
that the mid-infrared emission is clearly resolved. The characteristic
size of the MIR-emission region is ~30-60 AU; this value is typical for
other YSOs with similar or somewhat lower luminosities. A comparison of
the sizes for the two position angles shows a significant elongation of
the dust distribution. Simple spherical envelope models are therefore
inconsistent with the data. The radiative transfer modeling of our
data suggests that we observe a geometrically thin and optically thick
circumstellar disk with a mass of about 0.1 M⊙.
Conclusions: Our modeling indicates that NGC 2264 IRS 1 is surrounded
by a flat circumstellar disk that has properties similar to disks
typically found around lower-mass young stellar objects. This result
supports the assumption that massive young stellar objects form via
accretion from circumstellar disks. Based on observations collected
at the European Organisation for Astronomical Research in the Southern
Hemisphere, Chile, observing programs 076.C-0725(B) and 082.C-899(A).
Title: Images of unclassified and supergiant B[e] stars disks with
interferometry
Authors: Millour, Florentin; Meilland, Anthony; Chesneau, Olivier;
Fernandes, Marcelo Borges; Groh, Jose H.; Driebe, Thomas; Liermann,
Adrianne; Weigelt, Gerd
Bibcode: 2011IAUS..272..410M
Altcode: 2010arXiv1011.3391M
B[e] stars are among the most peculiar objects in the sky. This
spectral type, characterised by allowed and forbidden emission lines,
and a large infrared excess, does not represent an homogenous class of
objects, but instead, a mix of stellar bodies seen in all evolutionary
status. Among them, one can find Herbig stars, planetary nebulae
central stars, interacting binaries, supermassive stars, and even
``unclassified'' B[e] stars: systems sharing properties of several
of the above. Interferometry, by resolving the innermost regions of
these stellar systems, enables us to reveal the true nature of these
peculiar stars among the peculiar B[e] stars.
Title: A low optical depth region in the inner disk of the Herbig
Ae star HR 5999
Authors: Benisty, M.; Renard, S.; Natta, A.; Berger, J. P.; Massi,
F.; Malbet, F.; Garcia, P. J. V.; Isella, A.; Mérand, A.; Monin,
J. L.; Testi, L.; Thiébaut, E.; Vannier, M.; Weigelt, G.
Bibcode: 2011A&A...531A..84B
Altcode: 2011arXiv1106.4150B
Context. Circumstellar disks surrounding young stars are known to be
the birthplaces of planetary systems, and the innermost astronomical
unit is of particular interest. Near-infrared interferometric
studies have revealed a complex morphology for the close environment
surrounding Herbig Ae stars.
Aims: We present new long-baseline
spectro-interferometric observations of the Herbig Ae star, HR 5999,
obtained in the H and K bands with the AMBER instrument at the VLTI, and
aim to produce near-infrared images at the sub-AU spatial scale.
Methods: We spatially resolve the circumstellar material and
reconstruct images in the H and K bands using the MiRA algorithm. In
addition, we interpret the interferometric observations using models
that assume that the near-infrared excess is dominated by the emission
of a circumstellar disk. We compare the images reconstructed from the
VLTI measurements to images obtained using simulated model data.
Results: The K-band image reveals three main elements: a ring-like
feature located at ~0.65 AU, a low surface brightness region inside
0.65 AU, and a central spot. At the maximum angular resolution of our
observations (B/λ ~ 1.3 mas), the ring is resolved while the central
spot is only marginally resolved, preventing us from revealing the
exact morphology of the circumstellar environment. We suggest that
the ring traces silicate condensation, i.e., an opacity change, in
a circumstellar disk around HR 5999. We build a model that includes
a ring at the silicate sublimation radius and an inner disk of low
surface brightness responsible for a large amount of the near-infrared
continuum emission. The model successfully fits the SED, visibilities,
and closure phases in the H and K bands, and provides evidence of a low
surface brightness region inside the silicate sublimation radius.
Conclusions: This study provides milli-arcsecond resolution images of
the environment of HR 5999 and additional evidence that in Herbig Ae
stars, there is material in a low surface brightness region, probably
a low optical depth region, located inside the silicate sublimation
radius and of unknown nature. The possibility that the formation of
such a region in a thick disk is related to disk evolution should
be investigated. Based on observations collected at the VLTI
(ESO Paranal, Chile) with programs 080.C-0056, 083.C-0298, 083.C-0144,
083.C-0334, 083.C-0170, 083.C-0857, 083.C-0864, 083.C-0602, 084.C-0590,
085.C-0769, 085.C-0502.Appendix A is available in electronic form at
http://www.aanda.org
Title: Constraining the structure of the planet-forming region in
the disk of the Herbig Be star HD 100546
Authors: Tatulli, E.; Benisty, M.; Ménard, F.; Varnière, P.;
Martin-Zaïdi, C.; Thi, W. -F.; Pinte, C.; Massi, F.; Weigelt, G.;
Hofmann, K. -H.; Petrov, R. G.
Bibcode: 2011A&A...531A...1T
Altcode: 2011arXiv1104.0905T
Context. Studying the physical conditions in circumstellar disks
is a crucial step toward understanding planet formation and disk
evolution. Of particular interest is the case of HD 100546, a Herbig Be
star that presents a gap within the first 13 AU of its protoplanetary
disk, a gap that may originate in the dynamical interactions of
a forming planet with its hosting disk.
Aims: We seek a
more detailed understanding of the structure of the circumstellar
environment of HD 100546 and refine our previous disk model that is
composed of a tenuous inner disk, a gap and a massive outer disk (see
Benisty et al. 2010, A&A, 511, A75). We also investigate whether
planetary formation processes can explain the complex density structure
observed in the disk.
Methods: We gathered a large amount of
new interferometric data using the AMBER/VLTI instrument in the H-
and K-bands to spatially resolve the warm inner disk and constrain
its structure. Then, combining these measurements with photometric
observations, we analyze the circumstellar environment of HD 100546
in the light of a passive disk model based on 3D Monte-Carlo radiative
transfer. Finally, we use hydrodynamical simulations of gap formation
by planets to predict the radial surface density profile of the disk
and test the hypothesis of ongoing planet formation.
Results:
The SED (spectral energy distribution) from the UV to the millimeter
range, and the NIR (near-infrared) interferometric data are adequately
reproduced by our model. We show that the H- and K-band emissions
are coming mostly from the inner edge of the internal dust disk,
located near 0.24 AU from the star, i.e., at the dust sublimation
radius in our model. At such a short distance, the survival of hot
(silicate) dust requires the presence of micron-sized grains, heated
at ~1750 K. We directly measure an inclination of 33° ± 11° and a
position angle of 140° ± 16° for the inner disk. This is similar
to the values found for the outer disk (i ≃ 42°, PA ≃ 145°),
suggesting that both disks may be coplanar. We finally show that 1
to 8 Jupiter mass planets located at ~8 AU from the star would have
enough time to create the gap and the required surface density jump of
three orders of magnitude between the inner and outer disk. However,
no information on the amount of matter left in the gap is available,
which precludes us from setting precise limits on the planet mass,
for now. Based on observations collected at the VLT (ESO Paranal,
Chile) with programs 082.D-0010(A), 083.C-0298(A,B), 083.D-0224(C),
083.C-0146(B), 083.C-0144(A,D), 083.C-0236(A), 075.C-0637(A)
Title: Imaging ``Pinwheel'' nebulae with optical long-baseline
interferometry
Authors: Millour, Florentin; Driebe, Thomas; Groh, Jose H.; Chesneau,
Olivier; Weigelt, Gerd; Liermann, Adriane; Meilland, Anthony
Bibcode: 2011IAUS..272..408M
Altcode: 2010arXiv1011.3394M
Dusty Wolf-Rayet stars are few but remarkable in terms
of dust production rates (up to Ṁ = 10-6
Msolar/yr). Infrared excesses associated to mass-loss are
found in the sub-types WC8 and WC9. Few WC9d stars are hosting a
``pinwheel'' nebula, indirect evidence of a companion star around
the primary. While few other WC9d stars have a dust shell which has
been barely resolved so far, the available angular resolution offered
by single telescopes is insufficient to confirm if they also host
``pinwheel'' nebulae or not. In this article, we present the possible
detection of such nebula around the star WR 118. We discuss about the
potential of interferometry to image more ``pinwheel'' nebulae around
other WC9d stars.
Title: Imaging the dynamical atmosphere of the red supergiant
Betelgeuse in the CO first overtone lines with VLTI/AMBER
Authors: Ohnaka, K.; Weigelt, G.; Millour, F.; Hofmann, K. -H.;
Driebe, T.; Schertl, D.; Chelli, A.; Massi, F.; Petrov, R.; Stee, Ph.
Bibcode: 2011A&A...529A.163O
Altcode: 2011arXiv1104.0958O
Aims: We present one-dimensional aperture synthesis imaging of
the red supergiant Betelgeuse (α Ori) with VLTI/AMBER. We reconstructed
for the first time one-dimensional images in the individual CO first
overtone lines. Our aim is to probe the dynamics of the inhomogeneous
atmosphere and its time variation.
Methods: Betelgeuse was
observed between 2.28 and 2.31 μm with VLTI/AMBER using the 16-32-48
m telescope configuration with a spectral resolution up to 12 000 and
an angular resolution of 9.8 mas. The good nearly one-dimensional uv
coverage allows us to reconstruct one-dimensional projection images
(i.e., one-dimensional projections of the object's two-dimensional
intensity distributions).
Results: The reconstructed
one-dimensional projection images reveal that the star appears
differently in the blue wing, line center, and red wing of the
individual CO lines. The one-dimensional projection images in the
blue wing and line center show a pronounced, asymmetrically extended
component up to ~1.3 R⋆, while those in the red wing do
not show such a component. The observed one-dimensional projection
images in the lines can be reasonably explained by a model in which the
CO gas within a region more than half as large as the stellar size is
moving slightly outward with 0-5 km s-1, while the gas in
the remaining region is infalling fast with 20-30 km s-1. A
comparison between the CO line AMBER data taken in 2008 and 2009 shows
a significant time variation in the dynamics of the CO line-forming
region in the photosphere and the outer atmosphere. In contrast to
the line data, the reconstructed one-dimensional projection images
in the continuum show only a slight deviation from a uniform disk
or limb-darkened disk. We derive a uniform-disk diameter of 42.05
± 0.05 mas and a power-law-type limb-darkened disk diameter of
42.49 ± 0.06 mas and a limb-darkening parameter of (9.7 ± 0.5) ×
10-2. This latter angular diameter leads to an effective
temperature of 3690 ± 54 K for the continuum-forming layer. These
diameters confirm that the near-IR size of Betelgeuse was nearly
constant over the last 18 years, in marked contrast to the recently
reported noticeable decrease in the mid-IR size. The continuum data
taken in 2008 and 2009 reveal no or only marginal time variations,
much smaller than the maximum variation predicted by the current
three-dimensional convection simulations.
Conclusions:
Our two-epoch AMBER observations show that the outer atmosphere
extending to ~1.3-1.4 R⋆ is asymmetric and its dynamics
is dominated by vigorous, inhomogeneous large-scale motions, whose
overall nature changes drastically within one year. This is likely
linked to the wind-driving mechanism in red supergiants. Based on
AMBER observations made with the Very Large Telescope Interferometer
of the European Southern Observatory. Program ID: 082.D-0280 (AMBER
Guaranteed Time Observation).Appendices are available in electronic
form at http://www.aanda.org
Title: Zooming in on high-mass star formation with combined VLTI
near-infrared interferometry and ATCA millimeter interferometry
Authors: Kraus, Stefan; Menten, Karl; Schilke, Peter; Wyrowski,
Friedrich; Bergin, Edwin; Wienen, Marion; Weigelt, Gerd
Bibcode: 2011atnf.prop.4135K
Altcode:
In spite of its importance for astrophysics, the process through
which massive stars form is only poorly understood. In a recent study,
we detected with VLTI near-infrared interferometry a compact (9 AU)
disk-like structure around the high-mass protostar IRAS13481-6124
(Kraus et al. 2010, Nature 466, 339). Perpendicular to the disk
plane, we detected two bow shocks in Spitzer/IRAC images, suggesting
the presence of a collimated bipolar outflow. In order to study the
inner-most outflow regions and to measure the precise outflow direction
and collimation angle, we propose ATCA interferometric observations
in SiO, HCN, HCO+ line and 3mm continuum emission. In our initial
2010APRS observations, we successfully resolved IRAS13481-6124
with ATCA baselines up to 1.2km and at wavelengths down to 3mm,
although a large fraction of the observing time was lost due to poor
atmospheric conditions. The proposed follow-up observations will
result in an uv-coverage suitable for direct imaging. For the physical
interpretation, we will simultaneously fit the SED, and VLTI&ATCA
visibilities using 2-D radiative transfer modeling, allowing us to
solve many of the degeneracies which are inherent to single-wavelength
investigations and to characterize the global disk structure.
Title: VLTI/AMBER spectro-interferometry of the Herbig Be star MWC
297 with spectral resolution 12 000
Authors: Weigelt, G.; Grinin, V. P.; Groh, J. H.; Hofmann, K. -H.;
Kraus, S.; Miroshnichenko, A. S.; Schertl, D.; Tambovtseva, L. V.;
Benisty, M.; Driebe, T.; Lagarde, S.; Malbet, F.; Meilland, A.;
Petrov, R.; Tatulli, E.
Bibcode: 2011A&A...527A.103W
Altcode: 2011arXiv1101.3695W
Context. Circumstellar disks and outflows play a fundamental role
in star formation. Infrared spectro-interferometry allows the inner
accretion-ejection region to be resolved.
Aims: We study the disk
and Brγ-emitting region of MWC 297 with high spatial
and spectral resolution and compare our observations with disk-wind
models.
Methods: We measured interferometric visibilities,
wavelength-differential phases, and closure phases of MWC 297 with a
spectral resolution of 12 000. To interpret our MWC 297 observations,
we employed disk-wind models.
Results: The measured continuum
visibilities confirm previous results that the continuum-emitting region
of MWC 297 is remarkably compact. We derive a continuum ring-fit radius
of ~2.2 mas (~0.56 AU at a distance of 250 pc), which is ~5.4 times
smaller than the 3 AU dust sublimation radius expected for silicate
grains (in the absence of radiation-shielding material). The strongly
wavelength-dependent and asymmetric Brγ-emitting region is more
extended (~2.7 times) than the continuum-emitting region. At the center
of the Brγ line, we derive a Gaussian fit radius of ~6.3 mas HWHM (~1.6
AU). To interpret the observations, we employ a magneto-centrifugally
driven disk-wind model consisting of an accretion disk, which emits
the observed continuum radiation, and a disk wind, which emits the Brγ
line. The calculated wavelength-dependent model intensity distributions
and Brγ line profiles are compared with the observations (i.e., K-band
spectrum, visibilities, differential phases, and closure phases). The
closest fitting model predicts a continuum-emitting disk with an inner
radius of ~0.3 AU and a disk wind ejection region with an inner radius
of ~ 0.5 AU (~17.5 stellar radii). We obtain a disk-wind half-opening
angle (the angle between the rotation axis and the innermost streamline
of the disk wind) of ~80°, which is larger than in T Tau models,
and a disk inclination angle of ~20° (i.e., almost pole-on).
Conclusions: Our observations with a spectral resolution of 12 000
allow us to study the AU-scale environment of MWC 297 in ~10 different
spectral channels across the Brγ emission line. We show that the K-band
flux, visibilities, and remarkably strong phases can be explained by
the employed magneto-centrifugally driven disk wind model. Based
on observations made with ESO telescopes at Paranal Observatory under
programme ID 081.D-0230(A).
Title: The innermost dusty structure in active galactic nuclei as
probed by the Keck interferometer
Authors: Kishimoto, M.; Hönig, S. F.; Antonucci, R.; Barvainis, R.;
Kotani, T.; Tristram, K. R. W.; Weigelt, G.; Levin, K.
Bibcode: 2011A&A...527A.121K
Altcode: 2010arXiv1012.5359K
We are now exploring the inner region of type 1 active galactic nuclei
(AGNs) with the Keck interferometer in the near-infrared. Adding to
the four targets previously studied, we report measurements of the
K-band (2.2 μm) visibilities for four more targets, namely AKN120,
IC 4329A, Mrk6, and the radio-loud QSO 3C 273 at z = 0.158. The
observed visibilities are quite high for all the targets, which
we interpret as an indication of the partial resolution of the dust
sublimation region. The effective ring radii derived from the observed
visibilities scale approximately with L1/2, where L is
the AGN luminosity. Comparing the radii with those from independent
optical-infrared reverberation measurements, these data support our
previous claim that the interferometric ring radius is either roughly
equal to or slightly larger than the reverberation radius. We interpret
the ratio of these two radii for a given L as an approximate probe
of the radial distribution of the inner accreting material. We show
tentative evidence that this inner radial structure might be closely
related to the radio-loudness of the central engine. Finally, we
re-observed the brightest Seyfert 1 galaxy NGC 4151. Its marginally
higher visibility at a shorter projected baseline, compared to our
previous measurements obtained one year before, further supports
the partial resolution of the inner structure. We did not detect any
significant change in the implied emission size when the K-band flux
was brightened by a factor of 1.5 over a time interval of one year.
Title: Testing 3D SPH Models Of Eta Carina's Winds By HST, RXTE,
VLT And VLTI Observations
Authors: Gull, Theodore R.; Madura, T.; Groh, J.; Weigelt, G.;
Corcoran, M.; Owocki, S.; Russell, C.; Okazaki, A.
Bibcode: 2011AAS...21733817G
Altcode: 2011BAAS...4333817G
Observations of Eta Carina have been combined with three-dimensional
smoothed-particle hydrodynamic (3DSPH) simulations providing
considerable insight on this >100 Mo binary that may become
near-term supernovae, a GRB, or a staid WR binary. Understanding how
this system loses 1e-3 Mo/yr, 500 km/s will provide new understanding
of massive stellar evolution, including the first progenitors of GRBs,
supernovae and pseudo-supernovae. The 3DSPH models extend to 100
semi-major axes ( 2000 AU, <2” at 2300 pc). At these scales,
HST/STIS resolves [Fe III] and [Fe II] spatial-velocity structures
that change with orbital phase and position angle. Radiative transfer
models combining temperature and density with EtaCar B's FUV lead to
synthetic spectroimages of extended wind-wind interfaces. Model X-ray
light curves provide orbital inclination and location of periastron
but cannot determine sky PA. Synthetic spectro-images generated for
a range of possible binary orientations lead to best-fit when the
orbital axis is closely aligned with the Homunculus axis of symmetry,
and periastron with EtaCar B on the far side of EtaCar A. VLTI/AMBER
measures of the continuum, extended hydrogen and helium structures
of EtaCar A demonstrate that, across periastron, EtaCar B penetrates
the primary extended atmosphere. Spectroimagery observations of He
10830 by VLT/CRIRES show blue-shifted emission extending to -1500
km/s, consistent with wind-wind structures driven by the companion's
fast wind. The 2009.0 RXTE X-ray recovery and return of the
spectroscopic high state was much sooner than the 1998.0 and 2003.5
recoveries. What has changed? Suggestions range from a drop in the
primary wind, changes in the secondary wind or line-of-sight shifting
of the wind-wind boundary. We will discuss potential observational
tests based upon predictions by 3DSPH models.
Title: Magnetic Braking of the Main Component of θ^{1} Ori C
Authors: Balega, Yu. Yu.; Leushin, V. V.; Weigelt, G.
Bibcode: 2011mast.conf..179B
Altcode:
θ^{1} Ori C is the nearest massive O star at the early phase of
the evolution. Interferometric study of the star at the 6-m BTA
telescope showed that it is a binary system with an orbital period
of 11 yr (Weigelt et al., 1999). It was also found that θ^{1} Ori
C is an oblique magnetic rotator (Donati et al., 2002; Wade et al.,
2006). From high resolution spectra of the binary collected with the
6-m telescope we succeeded to separate week lines of the secondary
component and to measure its rotation velocity. It was found that the
secondary rotates three times faster than the primary. We discuss the
possibility of magnetic braking of the primary star as the mechanism
explaining the difference of rotation.
Title: The 2008 outburst in the young stellar system Z
CMa. I. Evidence of an enhanced bipolar wind on the AU-scale
Authors: Benisty, M.; Malbet, F.; Dougados, C.; Natta, A.; Le Bouquin,
J. B.; Massi, F.; Bonnefoy, M.; Bouvier, J.; Chauvin, G.; Chesneau,
O.; Garcia, P. J. V.; Grankin, K.; Isella, A.; Ratzka, T.; Tatulli,
E.; Testi, L.; Weigelt, G.; Whelan, E. T.
Bibcode: 2010A&A...517L...3B
Altcode: 2010arXiv1007.0682B
Context. Accretion is a fundamental process in star formation. Although
the time evolution of accretion remains a matter of debate,
observations and modelling studies suggest that episodic outbursts
of strong accretion may dominate the formation of the central
protostar. Observing young stellar objects during these elevated
accretion states is crucial to understanding the origin of unsteady
accretion.
Aims: Z CMa is a pre-main-sequence binary system
composed of an embedded Herbig Be star, undergoing photometric
outbursts, and a FU Orionis star. This system therefore provides a
unique opportunity to study unsteady accretion processes. The Herbig Be
component recently underwent its largest optical photometric outburst
detected so far. We aim to constrain the origin of this outburst
by studying the emission region of the HI Brγ line,
a powerful tracer of accretion/ejection processes on the AU-scale in
young stars.
Methods: Using the AMBER/VLTI instrument at spectral
resolutions of 1500 and 12 000, we performed spatially and spectrally
resolved interferometric observations of the hot gas emitting across the
Brγ emission line, during and after the outburst. From the
visibilities and differential phases, we derive characteristic sizes
for the Brγ emission and spectro-astrometric measurements
across the line, with respect to the continuum.
Results: We find
that the line profile, the astrometric signal, and the visibilities
are inconsistent with the signature of either a Keplerian disk or
infall of matter. They are, instead, evidence of a bipolar wind, maybe
partly seen through a disk hole inside the dust sublimation radius. The
disappearance of the Brγ emission line after the outburst
suggests that the outburst is related to a period of strong mass loss
rather than a change of the extinction along the line of sight.
Conclusions: Apart from the photometric increase of the system,
the main consequence of the outburst is to trigger a massive bipolar
outflow from the Herbig Be component. Based on these conclusions,
we speculate that the origin of the outburst is an event of enhanced
mass accretion, similar to those occuring in EX Ors and FU Ors. Based on observations collected at the VLTI (ESO Paranal, Chile)
with programs 282.C-5031, 082.C-0376, 084.C-0162.
Title: Imaging beyond the fringe: an update on the LINC-NIRVANA
Fizeau interferometer for the LBT
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2010SPIE.7734E..07H
Altcode: 2010SPIE.7734E...6H
We present an update on the construction and integration of
LINC-NIRVANA, a Fizeau-mode imaging interferometer for the
Large Binocular Telescope (LBT). The LBT is a unique platform for
interferometry, since its two, co-mounted 8.4 meter primary mirrors
present an orientation-independent entrance pupil. This allows
Fizeau-mode beam combination, providing 23-meter spatial resolution and
12-meter effective collecting area for panoramic imagery LINC-NIRVANA
will sit at one of the shared, bent focal stations, receiving
light from both mirrors of the LBT. The instrument uses visible
wavelength radiation for wavefront control, and the near-infrared
bands for science and fringe tracking. LINC-NIRVANA employs a number of
innovative technologies, including multi-conjugated adaptive optics,
state-of-the-art materials, low vibration mechanical coolers, active
and passive control, and sophisticated software for data analysis. The
instrument is in its final construction and integration phase. This
paper reports on overall progress, including insights gained on
large instrument assembly, software integration, science planning,
and vibration control. A number of additional contributions to this
conference focus on individual subsystems and integration-related
issues.
Title: A hot compact dust disk around a massive young stellar object
Authors: Kraus, Stefan; Hofmann, Karl-Heinz; Menten, Karl M.; Schertl,
Dieter; Weigelt, Gerd; Wyrowski, Friedrich; Meilland, Anthony; Perraut,
Karine; Petrov, Romain; Robbe-Dubois, Sylvie; Schilke, Peter; Testi,
Leonardo
Bibcode: 2010Natur.466..339K
Altcode: 2010arXiv1007.5062K
Circumstellar disks are an essential ingredient of the formation of
low-mass stars. It is unclear, however, whether the accretion-disk
paradigm can also account for the formation of stars more massive
than about 10 solar masses, in which strong radiation pressure
might halt mass infall. Massive stars may form by stellar merging,
although more recent theoretical investigations suggest that the
radiative-pressure limit may be overcome by considering more complex,
non-spherical infall geometries. Clear observational evidence, such
as the detection of compact dusty disks around massive young stellar
objects, is needed to identify unambiguously the formation mode of
the most massive stars. Here we report near-infrared interferometric
observations that spatially resolve the astronomical-unit-scale
distribution of hot material around a high-mass (~20 solar masses)
young stellar object. The image shows an elongated structure with a
size of ~13×19astronomical units, consistent with a disk seen at an
inclination angle of ~45°. Using geometric and detailed physical
models, we found a radial temperature gradient in the disk, with
a dust-free region less than 9.5astronomical units from the star,
qualitatively and quantitatively similar to the disks observed in
low-mass star formation. Perpendicular to the disk plane we observed
a molecular outflow and two bow shocks, indicating that a bipolar
outflow emanates from the inner regions of the system.
Title: Detection of high-velocity material from the wind-wind
collision zone of Eta Carinae across the 2009.0 periastron passage
Authors: Groh, J. H.; Nielsen, K. E.; Damineli, A.; Gull, T. R.;
Madura, T. I.; Hillier, D. J.; Teodoro, M.; Driebe, T.; Weigelt, G.;
Hartman, H.; Kerber, F.; Okazaki, A. T.; Owocki, S. P.; Millour, F.;
Murakawa, K.; Kraus, S.; Hofmann, K. -H.; Schertl, D.
Bibcode: 2010A&A...517A...9G
Altcode: 2010arXiv1003.4527G
We report near-infrared spectroscopic observations of the Eta Carinae
massive binary system during 2008-2009 using the CRIRES spectrograph
mounted on the 8 m UT 1 Very Large Telescope (VLT Antu). We detect a
strong, broad absorption wing in He i λ10833 extending up to -1900
km s-1 across the 2009.0 spectroscopic event. Analysis of
archival Hubble Space Telescope/Space Telescope Imaging Spectrograph
ultraviolet and optical data identifies a similar high-velocity
absorption (up to -2100 km s-1) in the ultraviolet resonance
lines of Si iv λλ1394, 1403 across the 2003.5 event. Ultraviolet
resonance lines from low-ionization species, such as Si ii λλ1527,
1533 and C ii λλ1334, 1335, show absorption only up to -1200
km s-1, indicating that the absorption with velocities
-1200 to -2100 km s-1 originates in a region markedly
more rapidly moving and more ionized than the nominal wind of the
primary star. Seeing-limited observations obtained at the 1.6 m
OPD/LNA telescope during the last four spectroscopic cycles of
Eta Carinae (1989-2009) also show high-velocity absorption in He i
λ10833 during periastron. Based on the large OPD/LNA dataset, we
determine that material with velocities more negative than -900 km
s-1 is present in the phase range 0.976 ≤ ϕ ≤ 1.023 of
the spectroscopic cycle, but absent in spectra taken at ϕ ≤ 0.94 and
ϕ ≥ 1.049. Therefore, we constrain the duration of the high-velocity
absorption to be 95 to 206 days (or 0.047 to 0.102 in phase). We propose
that the high-velocity absorption component originates in shocked gas
in the wind-wind collision zone, at distances of 15 to 45 AU in the
line-of-sight to the primary star. With the aid of three-dimensional
hydrodynamical simulations of the wind-wind collision zone, we find that
the dense high-velocity gas is along the line-of-sight to the primary
star only if the binary system is oriented in the sky such that the
companion is behind the primary star during periastron, corresponding
to a longitude of periastron of ω ~ 240°-270°. We study a possible
tilt of the orbital plane relative to the Homunculus equatorial
plane and conclude that our data are broadly consistent with orbital
inclinations in the range i = 40°-60°. Based on observations
made with ESO Telescopes at the La Silla Paranal Observatory under
programme IDs 381.D-0262, 282.D-5043, and 383.D-0240; with the Hubble
Space Telescope Imaging Spectrograph (HST/STIS) under programs 9420
and 9973; and with the 1.6 m telescope of the OPD/LNA (Brazil).
Title: OVMS: the optical path difference and vibration monitoring
system for the LBT and its interferometers
Authors: Kürster, M.; Bertram, T.; Borelli, J. L.; Brix, M.; Gässler,
W.; Herbst, T. M.; Naranjo, V.; Pott, J. -U.; Trowitzsch, J.; Connors,
T. E.; Hinz, P. M.; McMahon, T. J.; Ashby, D. S.; Brynnel, J. G.;
Cushing, N. J.; Edgin, T.; Esguerra, J. D.; Green, R. F.; Kraus, J.;
Little, J.; Beckmann, U.; Weigelt, G. P.
Bibcode: 2010SPIE.7734E..2YK
Altcode: 2010SPIE.7734E..94K
Characterisation, mitigation and correction of telescope vibrations
have proven to be crucial for the performance of astronomical infrared
interferometers. The project teams of the interferometers for the LBT,
LINC-NIRVANA and LBTI, and LBT Observatory (LBTO) have embarked on a
joint effort to implement an accelerometer-based vibration measurement
system distributed over the optical elements of the LBT. OVMS,
the Optical Path Difference and Vibration Monitoring System will
serve to (i) ensure conditions suitable for adaptive optics (AO)
and interferometric (IF) observations and (ii) utilize vibration
information, converted into tip-tilt and optical path difference data,
in the control strategies of the LBT adaptive secondary mirrors and the
beam combining interferometers. The system hardware is mainly developed
by Steward Observatory's LBTI team and its installation at the LBT
is underway. The OVMS software development and associated computer
infrastructure is the responsibility of the LINC-NIRVANA team at MPIA
Heidelberg. Initially, the OVMS will fill a data archive provided by
LBTO that will be used to study vibration data and correlate them with
telescope movements and environmental parameters thereby identifiying
sources of vibrations and to eliminate or mitigate them. Data display
tools will help LBTO staff to keep vibrations within predefined
thresholds for quiet conditions for AO and IF observations. Later-on
real-time data from the OVMS will be fed into the control loops of
the AO systems and IF instruments in order to permit the correction
of vibration signals with frequencies up to 450 Hz.
Title: First results from VLTI near-infrared interferometry on
high-mass young stellar objects
Authors: Kraus, Stefan; Hofmann, Karl-Heinz; Menten, Karl M.; Schertl,
Dieter; Weigelt, Gerd; Wyrowski, Friedrich; Meilland, Anthony; Perraut,
Karine; Petrov, Romain; Robbe-Dubois, Sylvie; Schilke, Peter; Testi,
Leonardo
Bibcode: 2010SPIE.7734E..08K
Altcode: 2010SPIE.7734E...7K; 2010arXiv1008.0001K
Due to the recent dramatic technological advances, infrared
interferometry can now be applied to new classes of objects,
resulting in exciting new science prospects, for instance, in the
area of high-mass star formation. Although extensively studied at
various wavelengths, the process through which massive stars form is
still only poorly understood. For instance, it has been proposed that
massive stars might form like low-mass stars by mass accretion through
a circumstellar disk/envelope, or otherwise by coalescence in a dense
stellar cluster. Therefore, clear observational evidence, such as
the detection of disks around high-mass young stellar objects (YSOs),
is urgently needed in order to unambiguously identify the formation
mode of the most massive stars. After discussing the technological
challenges which result from the special properties of these objects,
we present first near-infrared interferometric observations, which we
obtained on the massive YSO IRAS 13481-6124 using VLTI/AMBER infrared
long-baseline interferometry and NTT speckle interferometry. From
our extensive data set, we reconstruct a model-independent aperture
synthesis image which shows an elongated structure with a size of ~
13 x 19 AU, consistent with a disk seen under an inclination of -
45°. The measured wavelengthdependent visibilities and closure phases
allow us to derive the radial disk temperature gradient and to detect a
dust-free region inside of 9.5 AU from the star, revealing qualitative
and quantitative similarities with the disks observed in low-mass star
formation. In complementary mid-infrared Spitzer and sub-millimeter APEX
imaging observations we detect two bow shocks and a molecular outflow,
which are oriented perpendicular to the disk plane and indicate the
presence of a bipolar outflow emanating from the inner regions of
the system.
Title: ARGOS: the laser guide star system for the LBT
Authors: Rabien, S.; Ageorges, N.; Barl, L.; Beckmann, U.; Blümchen,
T.; Bonaglia, M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro,
L.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito, S.;
Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green, R.; Haug,
M.; Hart, M. L.; Hubbard, P.; Kanneganti, S.; Masciadri, E.; Noenickx,
J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.;
Rix, H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel,
M.; Weigelt, G.; Ziegleder, J.
Bibcode: 2010SPIE.7736E..0ER
Altcode: 2010SPIE.7736E..12R
ARGOS is the Laser Guide Star adaptive optics system for the Large
Binocular Telescope. Aiming for a wide field adaptive optics correction,
ARGOS will equip both sides of LBT with a multi laser beacon system
and corresponding wavefront sensors, driving LBT's adaptive secondary
mirrors. Utilizing high power pulsed green lasers the artificial beacons
are generated via Rayleigh scattering in earth's atmosphere. ARGOS
will project a set of three guide stars above each of LBT's mirrors
in a wide constellation. The returning scattered light, sensitive
particular to the turbulence close to ground, is detected in a gated
wavefront sensor system. Measuring and correcting the ground layers of
the optical distortions enables ARGOS to achieve a correction over a
very wide field of view. Taking advantage of this wide field correction,
the science that can be done with the multi object spectrographs LUCIFER
will be boosted by higher spatial resolution and strongly enhanced flux
for spectroscopy. Apart from the wide field correction ARGOS delivers
in its ground layer mode, we foresee a diffraction limited operation
with a hybrid Sodium laser Rayleigh beacon combination.
Title: The dusty heart of nearby active galaxies. I. High-spatial
resolution mid-IR spectro-photometry of Seyfert galaxies
Authors: Hönig, S. F.; Kishimoto, M.; Gandhi, P.; Smette, A.; Asmus,
D.; Duschl, W.; Polletta, M.; Weigelt, G.
Bibcode: 2010A&A...515A..23H
Altcode: 2010arXiv1003.0920H
In a series of papers, we aim at stepping towards characterizing
physical properties of the AGN dust torus by combining IR high-spatial
resolution observations with 3D clumpy torus models. In this
first paper, we present mid-IR imaging and 8-13 μm low-resolution
spectroscopy of nine type 1 and ten type 2 AGN. The observations
were carried out with the VLT/VISIR mid-IR imager and spectrograph
and can be considered the largest currently available mid-infrared
spectro-photometric data set of AGN at spatial resolution ⪉100
pc. These data resolve scales at which the emission from the dust
torus dominates the overall flux, and emission from the host galaxy
(e.g. star-formation) is resolved out in most cases. The silicate
absorption features are moderately deep and emission features, if
seen at all, are shallow. The strongest silicate emission feature
in our sample shows some notable shift of the central wavelength
from the expected 9.7 μm (based on ISM extinction curves) to ~10.5
μm. We compare the observed mid-IR luminosities of our objects to
AGN luminosity tracers (X-ray, optical and [O iii] luminosities)
and find that the mid-IR radiation is emitted quite isotropically. In
two cases, IC 5063 and MCG-3-34-64, we find evidence for extended dust
emission in the narrow-line region. We confirm the correlation between
observed silicate feature strength and Hydrogen column density, which
was recently found in Spitzer data at lower spatial resolution. In
a further step, our 3D clumpy torus model has been used to interpret
the data. We show that the strength of the silicate feature and the
mid-IR spectral index α can be used to get reasonable constraints
on the radial dust distribution of the torus and the average number
of clouds N0 along an equatorial line-of-sight in clumpy
torus models. The mid-IR spectral index α is almost exclusively
determined by the radial dust distribution power-law index a, while the
silicate feature depth mostly depends on N0 and the torus
inclination. A comparison of model predictions to our type 1 and type 2
AGN reveals that average parameters of a = -1.0±0.5 and N0
= 5-8 are typically seen in the presented sample, which means that the
radial dust distribution is rather shallow. As a proof-of-concept of
this method, we compared the model parameters derived from α and the
silicate feature strength to more detailed studies of full IR SEDs and
interferometry and found that the constraints on a and N0
are consistent. Finally, we may have found evidence that the radial
structure of the torus changes from low to high AGN luminosities
towards steeper dust distributions, and we discuss implications for
the IR size-luminosity relation. Based on ESO observing programs
078.B-0303, 080.B-0240, 280.B-5068, 082.B-0299, and 083.B-0239.
Title: Is Eta Carinae a Fast Rotator, and How Much Does the Companion
Influence the Inner Wind Structure?
Authors: Groh, J. H.; Madura, T. I.; Owocki, S. P.; Hillier, D. J.;
Weigelt, G.
Bibcode: 2010ApJ...716L.223G
Altcode: 2010arXiv1006.4816G
We analyze interferometric measurements of the luminous blue variable
Eta Carinae with the goal of constraining the rotational velocity of
the primary star and probing the influence of the companion. Using
two-dimensional radiative transfer models of latitude-dependent
stellar winds, we find that prolate-wind models with a ratio of the
rotational velocity (v rot) to the critical velocity (v
crit) of W = 0.77-0.92, inclination angle of i = 60°-90°,
and position angle (P.A.) =108°-142° reproduce simultaneously K-band
continuum visibilities from VLTI/VINCI and closure phase measurements
from VLTI/AMBER. Interestingly, oblate models with W = 0.73-0.90 and
i = 80°-90° produce similar fits to the interferometric data, but
require P.A. =210°-230°. Therefore, both prolate and oblate models
suggest that the rotation axis of the primary star is not aligned
with the Homunculus polar axis. We also compute radiative transfer
models of the primary star allowing for the presence of a cavity and
dense wind-wind interaction region created by the companion star. We
find that the wind-wind interaction has a significant effect on the
K-band image mainly via free-free emission from the compressed walls
and, for reasonable model parameters, can reproduce the VLTI/VINCI
visibilities taken at phivb03 = 0.92-0.93. We conclude that
the density structure of the primary wind can be sufficiently disturbed
by the companion, thus mimicking the effects of fast rotation in the
interferometric observables. Therefore, fast rotation may not be the
only explanation for the interferometric observations. Intense temporal
monitoring and three-dimensional modeling are needed to resolve these
issues. Based on observations made with VLTI/AMBER and VLTI/VINCI.
Title: Zooming in on high-mass star formation with combined VLTI
near-infrared interferometry and ATCA millimeter interferometry
Authors: Kraus, Stefan; Menten, Karl; Schilke, Peter; Wyrowski,
Friedrich; Bergin, Edwin; Weigelt, Gerd
Bibcode: 2010atnf.prop.3317K
Altcode:
In spite of its importance for astrophysics, the process through which
massive stars form is only poorly understood. In a recent study,
we resolved the inner environment around the high-mass protostar
IRAS13481-6124 (G310.0135+00.3892) using VLTI near-infrared (2
micrometer) long-baseline interferometry and detected a compact (11
AU) disk-like structure, whose size is consistent with the expected
dust sublimation radius. Perpendicular to the disk plane, we detect
two bow shocks in Spitzer/IRAC images, suggesting the presence of a
collimated bipolar outflow. The outflow was also detected in molecular
line emission using the APEX single-dish telescope. In order to study
the inner-most outflow regions and to measure the collimation angle,
we propose interferometric observations in SiO, HCO+, and in the 3mm
continuum emission. We also aim to resolve the thermal emission of the
circumstellar dust, providing important constraints on the radial dust
density profile. For the physical interpretation of the obtained data,
we will simultaneously fit the SED and VLTI&ATCA visibilities using
2-D radiative transfer modeling, enabling us to characterize the global
structure of the putative disk around this high-mass protostar.
Title: First spatial resolution of the stellar components of the
interacting binary CH Cygni
Authors: Mikołajewska, Joanna; Balega, Yuri; Hofmann, Karl-Heinz;
Weigelt, Gerd
Bibcode: 2010MNRAS.403L..21M
Altcode: 2009arXiv0910.5176M; 2010MNRAS.tmpL...8M
We report the first resolved bispectrum speckle interferometry of
the symbiotic binary CH Cyg. The measured component separation,
ρ = 42 +/- 2mas, is consistent with the one derived from the
known spectroscopic orbit and distance. In particular, our result
implies a total mass of the binary of Mt = Mg +
Mwd = 3.7+3.5-1.7Msolar,
which is in good agreement with the value Mt =
2.7+1.2-0.6Msolar derived from
the spectroscopic orbit solution for the red giant and evolutionary
constraints. We also show that the radio jets and the bipolar outflow
are not orthogonal to the orbital plane of the binary system. Based on observations made with the 6-m BTA telescope, which is
operated by the Special Astrophysical Observatory (SAO), Russia. E-mail: mikolaj@camk.edu.pl
Title: Infrared Interferometry of Young Stellar Objects
Authors: Kraus, S.; Hofmann, K. -H.; Preibisch, T.; Weigelt, G.
Bibcode: 2010RMxAC..38...63K
Altcode:
The circumstellar disks around young stellar objects play a key role
in the formation process of stars and provide the stage for planet
formation. Since recently, infrared interferometry provides the
spatial resolution required to directly study the distribution of the
gas and dust in the innermost AU around the forming star. We present
recent investigations in which we employed the VLTI and its near- and
mid-infrared interferometric instruments AMBER and MIDI to constrain
the geometry and physical conditions of the disks around Herbig Ae/Be
stars and to study the accretion and outflow processes taking place
close to the central star.
Title: Probing the innermost infrared emission in the brightest Type
1 AGN with the CHARA array
Authors: Kishimoto, Makoto; Antonucci, Robert; Barvainis, Richard;
Hoenig, Sebastian; Millour, Florentin; Tristram, Konrad; Weigelt, Gerd
Bibcode: 2010noao.prop...81K
Altcode:
We are making a major progress in AGN studies with the Keck
long- baseline interferometer in the near-IR. Based on our recent
observations, we are spatially resolving the innermost structure of
the AGN tori, and mapping out its radial structure quantitatively. This
totally new knowledge could well be the key to understand the critical
accretion process toward the central engine. Here we propose to
consolidate our new exploration by probing the structure of the
brightest Type 1 AGN at the highest spatial frequencies using very
long baselines, available only with the CHARA array.
Title: Strong near-infrared emission in the sub-AU disk of the Herbig
Ae star HD 163296: evidence of refractory dust?
Authors: Benisty, M.; Natta, A.; Isella, A.; Berger, J. -P.; Massi,
F.; Le Bouquin, J. -B.; Mérand, A.; Duvert, G.; Kraus, S.; Malbet,
F.; Olofsson, J.; Robbe-Dubois, S.; Testi, L.; Vannier, M.; Weigelt, G.
Bibcode: 2010A&A...511A..74B
Altcode: 2009arXiv0911.4363B
We present new long-baseline spectro-interferometric observations
of the Herbig Ae star HD 163296 (MWC 275) obtained in the H and K
bands with the AMBER instrument at the VLTI. The observations cover
a range of spatial resolutions between ~3 and ~12 milliarcseconds,
with a spectral resolution of ~30. With a total of 1481 visibilities
and 432 closure phases, they represent the most comprehensive (u,v)
coverage achieved so far for a young star. The circumstellar material
is resolved at the sub-AU spatial scale and closure phase measurements
indicate a small but significant deviation from point-symmetry. We
discuss the results assuming that the near-infrared excess in HD 163296
is dominated by the emission of a circumstellar disk. A successful fit
to the spectral energy distribution, near-infrared visibilities and
closure phases is found with a model in which a dominant contribution
to the H and K band emission originates in an optically thin, smooth
and point-symmetric region extending from about 0.1 to 0.45 AU. At
a distance of 0.45 AU from the star, silicates condense, the disk
becomes optically thick and develops a puffed-up rim, whose skewed
emission can account for the non-zero closure phases. We discuss
the source of the inner disk emission and tentatively exclude dense
molecular gas as well as optically thin atomic or ionized gas as its
possible origin. We propose instead that the smooth inner emission
is produced by very refractory grains in a partially cleared region,
extending to at least ~0.5 AU. If so, we may be observing the disk of
HD 163296 just before it reaches the transition disk phase. However,
we note that the nature of the refractory grains or, in fact, even
the possibility of any grain surviving at the very high temperatures
we require (~2100-2300 K at 0.1 AU from the star) is unclear and
should be investigated further. Based on AMBER observations
collected at the VLTI (European Southern Observatory, Paranal, Chile)
with Arcetri Guaranteed Time program 081.C-0124, LAOG Guaranteed Time
program 081.C-0794 and open time programs 081.C-0851, 081.C-0098.
Title: High Velocity Absorption during Eta Car B's periastron passage
Authors: Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, T. R.;
Madura, T. I.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro,
M.; Weigelt, G.; Hartman, H.
Bibcode: 2010AAS...21542605N
Altcode: 2010BAAS...42..341N
Eta Car is one of the most luminous massive stars in the Galaxy,
with repeated eruptions with a 5.5 year periodicity. These events are
caused by the periastron passage of a massive companion in an eccentric
orbit. We report the VLT/CRIRES detection of a strong high-velocity
(< 1900 km/s), broad absorption wing in He I at 10833 A during the
2009.0 periastron passage. Previous observations during the 2003.5
event have shown evidence of such high-velocity absorption in the He
I 10833 transition, allowing us to conclude that the high-velocity
gas is crossing the line-of-sight toward Eta Car over a time period
of approximately 2 months. Our analysis of HST/STIS archival data
with observations of high velocity absorption in the ultraviolet Si
IV and C IV resonance lines, confirm the presence of a high-velocity
material during the spectroscopic low state. The observations provide
direct detection of high-velocity material flowing from the wind-wind
collision zone around the binary system, and we discuss the implications
of the presence of high-velocity gas in Eta Car during periastron.
Title: Revealing the sub-AU asymmetries of the inner dust rim in
the disk around the Herbig Ae star R Coronae Austrinae
Authors: Kraus, S.; Hofmann, K. -H.; Malbet, F.; Meilland, A.; Natta,
A.; Schertl, D.; Stee, P.; Weigelt, G.
Bibcode: 2009A&A...508..787K
Altcode: 2009arXiv0911.3653K
Context: Unveiling the structure of the disks around intermediate-mass
pre-main-sequence stars (Herbig Ae/Be stars) is essential for our
understanding of the star and planet formation process. In particular,
models predict that in the innermost AU around the star, the dust disk
forms a “puffed-up” inner rim, which should result in a strongly
asymmetric brightness distribution for disks seen under intermediate
inclination.
Aims: Our aim is to constrain the sub-AU geometry
of the inner disk around the Herbig Ae star R CrA and search for
the predicted asymmetries.
Methods: Using the VLTI/AMBER
long-baseline interferometer, we obtained 24 near-infrared (H- and
K-band) spectro-interferometric observations on R CrA. Observing
with three telescopes in a linear array configuration, each data
set samples three equally spaced points in the visibility function,
providing direct information about the radial intensity profile. In
addition, the observations cover a wide position angle range (~97°),
also probing the position angle dependence of the source brightness
distribution.
Results: In the derived visibility function,
we detect the signatures of an extended (Gaussian FWHM ~ 25 mas)
and a compact component (Gaussian FWHM ~ 5.8 mas), with the compact
component contributing about two-thirds of the total flux (both in
H- and K-band). The brightness distribution is highly asymmetric,
as indicated by the strong closure phases (up to ~40°) and the
detected position angle dependence of the visibilities and closure
phases. To interpret these asymmetries, we employ various geometric
as well as physical models, including a binary model, a skewed ring
model, and a puffed-up inner rim model with a vertical or curved
rim shape. For the binary and vertical rim model, no acceptable fits
could be obtained. On the other hand, the skewed ring model and the
curved puffed-up inner rim model allow us to simultaneously reproduce
the measured visibilities and closure phases. From these models we
derive the location of the dust sublimation radius (~0.4 AU), the disk
inclination angle (~35°), and a north-south disk orientation (PA ~
180-190°). Our curved puffed-up rim model can reproduce reasonably well
the interferometric observables and the SED and suggests a luminosity of
~29 L⊙ and the presence of relatively large (⪆1.2 μm)
Silicate dust grains. Our study also reveals discrepancies between
the measured interferometric observables and the puffed-up inner
rim models, providing important constraints for future refinements
of these theoretical models. Perpendicular to the disk, two bow
shock-like structures appear in the associated reflection nebula NGC
6729, suggesting that the detected sub-AU size disk is the driving
engine of a large-scale outflow.
Conclusions: Detecting, for the
first time, strong non-localized asymmetries in the inner regions of a
Herbig Ae disk, our study supports the existence of a puffed-up inner
rim in YSO disks. Based on observations made with ESO telescopes
at the La Silla Paranal Observatory under programme IDs 079.D-0370(A),
081.C-0272(A,B,C), and 081.C-0321(A).
Title: Exploring the inner region of type 1 AGNs with the Keck
interferometer
Authors: Kishimoto, M.; Hönig, S. F.; Antonucci, R.; Kotani, T.;
Barvainis, R.; Tristram, K. R. W.; Weigelt, G.
Bibcode: 2009A&A...507L..57K
Altcode: 2009arXiv0911.0666K
The exploration of extragalactic objects with long-baseline
interferometers in the near-infrared has been very limited. Here we
report successful observations with the Keck interferometer at K-band
(2.2 μm) for four type 1 AGNs, namely NGC 4151, Mrk231, NGC 4051,
and the QSO IRAS 13349+2438 at z = 0.108. For the latter three objects,
these are the first long-baseline interferometric measurements in the
infrared. We detect high visibilities (V2 ~ 0.8-0.9) for
all the four objects including NGC 4151, for which we confirm the high
V2 level measured by Swain et al. (2003, ApJ, 596, L163). We
marginally detect a decrease of V2 with increasing baseline
lengths for NGC 4151, although over a very limited range, where the
decrease and absolute V2 are well fitted with a ring model
having a radius of 0.45 ± 0.04 mas (0.039 ± 0.003 pc). Strikingly,
this matches independent radius measurements from optical-infrared
reverberations that are thought to be probing the dust sublimation
radius. We also show that the effective radius of the other objects,
obtained from the same ring model, is either roughly equal to or
slightly larger than the reverberation radius as a function of AGN
luminosity. This suggests that we are indeed partially resolving the
dust sublimation region. The ratio of the effective ring radius to the
reverberation radius might also give us an approximate probe for the
radial structure of the inner accreting material in each object. This
should be scrutinized with further observations.
Title: VLTI/AMBER unveils a possible dusty pinwheel nebula in WR118
Authors: Millour, F.; Driebe, T.; Chesneau, O.; Groh, J. H.; Hofmann,
K. -H.; Murakawa, K.; Ohnaka, K.; Schertl, D.; Weigelt, G.
Bibcode: 2009A&A...506L..49M
Altcode: 2009arXiv0909.4207M
Context: Most Wolf-Rayet stars (WR) of the WC9 subtype exhibit a
dusty circumstellar envelope, but it is still a matter of debate
how dust can form in their harsh environment. In a few cases, a
pinwheel-like structure of the dusty envelope has been detected;
therefore, it has been suggested that dust formation in all dusty
WR stars might be linked to colliding winds in a binary system.
Aims: We probed the innermost region of the circumstellar dust
shell of the deeply embedded WR star WR 118.
Methods: We carried out spectro-interferometric observations using
the AMBER instrument of ESO's Very Large Telescope Interferometer in
low-spectral resolution mode (R=35). The K-band observations were
obtained with three 1.8 m telescopes spanning projected baselines
between 9.2 and 40.1 m.
Results: At high spatial frequencies,
the AMBER visibilities exhibit a prominent lobe, indicating that the
envelope contains one or several zones with a large local intensity
gradient. The strong closure phase signal clearly shows that the
circumstellar envelope of WR 118 can only be
described by an asymmetric intensity distribution. We show that a
pinwheel nebula seen at low inclination is consistent with the AMBER
data. Its size was determined to be 13.9±1.1 mas.
Conclusions:
WR 118 possibly harbors a pinwheel nebula, which
suggests a binary nature of the system. According to our best model,
the period of the system would be ≈60 days (for d=3 kpc), making
WR 118 the shortest-period pinwheel nebula known so far. The
observations presented in this paper were obtained with the
AMBER instrument of ESO's Very Large Telescope Interferometer
(VLTI) as part of the guaranteed time programme 079.D-0359(A)
(PI: T. Driebe). The reduced data will be sent to the ESO archive.
Title: A binary engine fuelling HD 87643's complex circumstellar
environment. Determined using AMBER/VLTI imaging
Authors: Millour, F.; Chesneau, O.; Borges Fernandes, M.; Meilland,
A.; Mars, G.; Benoist, C.; Thiébaut, E.; Stee, P.; Hofmann, K. -H.;
Baron, F.; Young, J.; Bendjoya, P.; Carciofi, A.; Domiciano de Souza,
A.; Driebe, T.; Jankov, S.; Kervella, P.; Petrov, R. G.; Robbe-Dubois,
S.; Vakili, F.; Waters, L. B. F. M.; Weigelt, G.
Bibcode: 2009A&A...507..317M
Altcode: 2009arXiv0908.0227M
Context: The star HD 87643, exhibiting the “B[e] phenomenon”, has
one of the most extreme infrared excesses for this object class. It
harbours a large amount of both hot and cold dust, and is surrounded
by an extended reflection nebula.
Aims: One of our major goals
was to investigate the presence of a companion in HD87643. In addition,
the presence of close dusty material was tested through a combination of
multi-wavelength high spatial resolution observations.
Methods:
We observed HD 87643 with high spatial resolution techniques, using
the near-IR AMBER/VLTI interferometer with baselines ranging from 60
m to 130 m and the mid-IR MIDI/VLTI interferometer with baselines
ranging from 25 m to 65 m. These observations are complemented by
NACO/VLT adaptive-optics-corrected images in the K and L-bands,
and ESO-2.2m optical Wide-Field Imager large-scale images in the B,
V and R-bands.
Results: We report the direct detection of a
companion to HD 87643 by means of image synthesis using the AMBER/VLTI
instrument. The presence of the companion is confirmed by the MIDI and
NACO data, although with a lower confidence. The companion is separated
by ~34 mas with a roughly north-south orientation. The period must be
large (several tens of years) and hence the orbital parameters are not
determined yet. Binarity with high eccentricity might be the key to
interpreting the extreme characteristics of this system, namely a dusty
circumstellar envelope around the primary, a compact dust nebulosity
around the binary system and a complex extended nebula suggesting
past violent ejections. Based on observations made with the ESO
very large telescope at Paranal Observatory under programs 076.D-0575,
077.D-0095, 076.D-0141, 380.D-0340, and 280.C-5071, with the ESO 1.52-m
and archival ESO data. Appendix is only available in electronic
form at http://www.aanda.org
Title: Resolving the asymmetric inner wind region of the yellow
hypergiant IRC +10420 with VLTI/AMBER in low and
high spectral resolution mode
Authors: Driebe, T.; Groh, J. H.; Hofmann, K. -H.; Ohnaka, K.; Kraus,
S.; Millour, F.; Murakawa, K.; Schertl, D.; Weigelt, G.; Petrov,
R.; Wittkowski, M.; Hummel, C. A.; Le Bouquin, J. B.; Merand, A.;
Schöller, M.; Massi, F.; Stee, P.; Tatulli, E.
Bibcode: 2009A&A...507..301D
Altcode: 2009arXiv0909.4688D
Context: IRC +10420 is a massive evolved star
belonging to the group of yellow hypergiants. Currently, this star
is rapidly evolving through the Hertzprung-Russell diagram, crossing
the so-called yellow void. IRC +10420 is suffering
from intensive mass loss which led to the formation of an extended
dust shell. Moreover, the dense stellar wind of IRC +10420
is subject to strong line emission.
Aims: Our goal was
to probe the photosphere and the innermost circumstellar environment
of IRC +10420, to measure the size of its continuum-
as well as the Brγ line-emitting region on milliarcsecond scales, and
to search for evidence of an asymmetric distribution of IRC
+10420's dense, circumstellar gas.
Methods: We obtained
near-infrared long-baseline interferometry of IRC +10420
with the AMBER instrument of ESO's Very Large Telescope
Interferometer (VLTI). The measurements were carried out in May/June
2007 and May 2008 in low-spectral resolution mode in the JHK bands
using three auxillary telescopes (ATs) at projected baselines ranging
from 30 to 96 m, and in October 2008 in high-spectral resolution
mode in the K band around the Brγ emission line using three unit
telescopes (UTs) with projected baselines between 54 and 129 m. The
high-spectral resolution mode observations were analyzed by means
of radiative transfer modeling using CMFGEN and the 2D Busche &
Hillier codes.
Results: For the first time, we have been able to
absolutely calibrate the H- and K-band data and, thus, to determine
the angular size of IRC+10420's continuum- and Brγ line-emitting
regions. We found that both the low resolution differential and
closure phases are zero within the uncertainty limits across all three
bands. In the high-spectral resolution observations, the visibilities
show a noticeable drop across the Brγ line on all three baselines. We
found differential phases up to -25° in the redshifted part of the
Brγ line and a non-zero closure phase close to the line center. The
calibrated visibilities were corrected for AMBER's limited field-of-view
to appropriately account for the flux contribution of IRC
+10420's extended dust shell. From our low-spectral resolution
AMBER data we derived FWHM Gaussian sizes of 1.05±0.07 and 0.98±0.10
mas for IRC +10420's continuum-emitting region in
the H and K bands, respectively. From the high-spectral resolution
data, we obtained a FWHM Gaussian size of 1.014±0.010 mas in the
K-band continuum. The Brγ -emitting region can be fitted with a
geometric ring model with a diameter of 4.18^+0.19-0.09
mas, which is approximately 4 times the stellar size. The geometric
model also provides some evidence that the Brγ line-emitting region
is elongated towards a position angle of 36°, well aligned with the
symmetry axis of the outer reflection nebula. Assuming an unclumped
wind and a luminosity of 6×10^5{ {L}⊙}, the spherical
radiative transfer modeling with CMGFEN yields a current mass-loss
rate of 1.5-2.0×10-5{ {M}⊙ yr-1}
based on the Brγ equivalent width. However, the spherical CMFGEN model
poorly reproduces the observed line shape, blueshift, and extension,
definitively showing that the IRC +10420 outflow
is asymmetric. Our 2D radiative transfer modeling shows that the
blueshifted Brγ emission and the shape of the visibility across the
emission line can be explained with an asymmetric bipolar outflow with a
high density contrast from pole to equator (8-16), where the redshifted
light is substantially diminished. The low-spectral resolution
data have been obtained as part of the Guaranteed Time Programme
for VLTI/AMBER (program ID: 079.D-0356(B)), while the high-spectral
resolution data were obtained in the context of science verification
observations (program ID: 60.A-9053(D)).
Title: Spatially resolving the inhomogeneous structure of the
dynamical atmosphere of Betelgeuse with VLTI/AMBER
Authors: Ohnaka, K.; Hofmann, K. -H.; Benisty, M.; Chelli, A.; Driebe,
T.; Millour, F.; Petrov, R.; Schertl, D.; Stee, Ph.; Vakili, F.;
Weigelt, G.
Bibcode: 2009A&A...503..183O
Altcode: 2009arXiv0906.4792O
Aims: We present spatially resolved, high-spectral resolution K-band
observations of the red supergiant Betelgeuse
(α Ori) using AMBER at the Very Large Telescope
Interferometer (VLTI). Our aim is to probe inhomogeneous structures
in the dynamical atmosphere of Betelgeuse.
Methods: Betelgeuse
was observed in the wavelength range between 2.28 and 2.31 μm
with VLTI/AMBER using baselines of 16, 32, and 48 m. The spectral
resolutions of 4800-12 000 allow us to study inhomogeneities seen
in the individual CO first overtone lines.
Results: Spectrally
dispersed interferograms have been successfully obtained in the second,
third, and fifth lobes, which represents the highest spatial resolution
(9 mas) achieved for Betelgeuse. This corresponds to five resolution
elements over its stellar disk. The AMBER visibilities and closure
phases in the K-band continuum can be reasonably fitted by a uniform
disk with a diameter of 43.19 ± 0.03 mas or a limb-darkening disk
with 43.56 ± 0.06 mas and a limb-darkening parameter of (1.2 ±
0.07) × 10-1. These AMBER data and the previous K-band
interferometric data taken at various epochs suggest that Betelgeuse
seen in the K-band continuum shows much smaller deviations from
the above uniform disk or limb-darkened disk than predicted by
recent 3-D convection simulations for red supergiants. On the other
hand, our AMBER data in the CO lines reveal salient inhomogeneous
structures. The visibilities and phases (closure phases, as well as
differential phases representing asymmetry in lines with respect to
the continuum) measured within the CO lines show that the blue and red
wings originate in spatially distinct regions over the stellar disk,
indicating an inhomogeneous velocity field that makes the star appear
different in the blue and red wings. Our AMBER data in the CO lines can
be roughly explained by a simple model, in which a patch of CO gas is
moving outward or inward with velocities of 10-15 km s-1,
while the CO gas in the remaining region in the atmosphere is moving
in the opposite direction at the same velocities. Also, the AMBER
data are consistent with the presence of warm molecular layers
(so-called MOLsphere) extending to 1.4-1.5 Rstar with
a CO column density of 1 × 1020 cm-2.
Conclusions: Our AMBER observations of Betelgeuse are the first
spatially resolved study of the so-called macroturbulence in a stellar
atmosphere (photosphere and possibly MOLsphere as well) other than
the Sun. The spatially resolved CO gas motion is likely to be related
to convective motion in the upper atmosphere or intermittent mass
ejections in clumps or arcs. Based on AMBER and VINCI observations
made with the Very Large Telescope Interferometer of the European
Southern Observatory. Program IDs: 080.D-0236 (AMBER Guaranteed Time
Observation), 60.A-9054A, and 60.A-9222A.
Title: Tracing the Dynamic Orbit of the Young, Massive
High-Eccentricity Binary System θ1 Orionis C. First results from
VLTI aperture-synthesis imaging and ESO 3.6-metre visual speckle
interferometry
Authors: Kraus, Stefan; Weigelt, Gerd; Balega, Yuri; Docobo, Jose;
Hofmann, Karl-Heinz; Preibisch, Thomas; Schertl, Dieter; Tamazian,
Vakhtang; Driebe, Thomas; Ohnaka, Keiichi; Petrov, Romain; Schöller,
Markus; Smith, Michael
Bibcode: 2009Msngr.136...44K
Altcode:
Located in the Orion Trapezium Cluster, θ1 Ori C is one of the youngest
and nearest high-mass stars known. Besides its unique properties
as an oblique magnetic rotator, the star happens to be a close (~20
milliarcseconds) binary system, which makes it an ideal laboratory
to determine the fundamental parameters of young hot stars. In this
article, we report on our 11-year interferometric monitoring campaign,
which covers nearly the full dynamic orbit of the system and resulted in
the first interferometric images obtained with the VLT interferometer
(VLTI) in the infrared (~20 µm) and diffraction-limited bispectrum
speckle interferometry at the ESO 3.6-metre telescope at visual (440
nm) wavelengths.
Title: A new spectroscopic and interferometric study of the young
stellar object V645 Cygni
Authors: Miroshnichenko, A. S.; Hofmann, K. -H.; Schertl, D.;
Weigelt, G.; Kraus, S.; Manset, N.; Albert, L.; Balega, Y. Y.;
Klochkova, V. G.; Rudy, R. J.; Lynch, D. K.; Mazuk, S.; Venturini,
C. C.; Russell, R. W.; Grankin, K. N.; Puetter, R. C.; Perry, R. B.
Bibcode: 2009A&A...498..115M
Altcode: 2009arXiv0904.1822M
Aims: We present the results of high-resolution optical spectroscopy,
low-resolution near-IR spectroscopy and near-infrared speckle
interferometry of the massive young stellar object candidate V645 Cyg,
acquired to refine its fundamental parameters and the properties of
its circumstellar envelope.
Methods: Speckle interferometry in
the H- and K-bands and an optical spectrum in the range 5200-6680 Å
with a spectral resolving power of R = 60 000 were obtained at the
6 m telescope of the Russian Academy of Sciences. Another optical
spectrum in the range 4300-10 500 Å with R = 79 000 was obtained at
the 3.6 m CFHT. Low-resolution spectra in the ranges 0.46-1.4 μm and
1.4-2.5 μm with R ~ 800 and ~700, respectively, were obtained at the
3 m Shane telescope of the Lick Observatory.
Results: Using
a novel kinematical method based on the non-linear modeling of the
neutral hydrogen density profile in the direction toward the object,
we propose a distance of D = 4.2 ± 0.2 kpc. We also suggest a revised
estimate of the star's effective temperature, T_eff ~ 25 000 K. We
resolved the object in both H- and K-bands. Using a two-component ring
fit, we derived a compact component size of 14 mas and 12 mas in the
H- and K-band, respectively, which correspond to 29 and 26 AU at the
revised distance. Analysis of our own and previously published data
indicates a ~2 mag decrease in the near-infrared brightness of V645
Cyg at the beginning of the 1980's. At the same time, the cometary
nebular condensation N1 appears to fade in this wavelength range with
respect to the N0 object, representing the star with a nearly pole-on
optically-thick disk and an optically-thin envelope.
Conclusions:
We conclude that V645 Cyg is a young, massive, main-sequence star,
which recently emerged from its cocoon and has already experienced
its protostellar accretion stage. The presence of accretion is not
necessary to account for the high observed luminosity of (2-6) ×
104 M⊙ yr-1. The receding part
of a strong, mostly uniform outflow with a terminal velocity of
~800 km s-1 is only blocked from view far from the star,
where forbidden lines form. The near-infrared size of the source is
consistent with the dust sublimation distance close to this hot and
luminous star and is the largest among all young stellar objects
observed interferometrically to-date. Partially based on data
obtained at the 6-m BTA telescope of the Russian Academy of Sciences,
3.6-m Canada-France-Hawaii telescope, and 3-m Shane telescope of the
Lick Observatory.
Title: Tracing the young massive high-eccentricity binary system
θ^1Orionis C through periastron passage
Authors: Kraus, S.; Weigelt, G.; Balega, Y. Y.; Docobo, J. A.; Hofmann,
K. -H.; Preibisch, T.; Schertl, D.; Tamazian, V. S.; Driebe, T.;
Ohnaka, K.; Petrov, R.; Schöller, M.; Smith, M.
Bibcode: 2009A&A...497..195K
Altcode: 2009arXiv0902.0365K
Context: The nearby high-mass star binary system θ^1Ori C is the
brightest and most massive of the Trapezium OB stars at the core of
the Orion Nebula Cluster, and it represents a perfect laboratory
to determine the fundamental parameters of young hot stars and to
constrain the distance of the Orion Trapezium Cluster.
Aims: By
tracing the orbital motion of the θ^1Ori C components, we aim to refine
the dynamical orbit of this important binary system.
Methods:
Between January 2007 and March 2008, we observed θ^1Ori C with
VLTI/AMBER near-infrared (H- and K-band) long-baseline interferometry,
as well as with bispectrum speckle interferometry with the ESO 3.6 m
and the BTA 6 m telescopes (B'- and V'-band). Combining AMBER data
taken with three different 3-telescope array configurations, we
reconstructed the first VLTI/AMBER closure-phase aperture synthesis
image, showing the θ^1Ori C system with a resolution of ∼ 2 mas. To
extract the astrometric data from our spectrally dispersed AMBER data,
we employed a new algorithm, which fits the wavelength-differential
visibility and closure phase modulations along the H- and K-band
and is insensitive to calibration errors induced, for instance, by
changing atmospheric conditions.
Results: Our new astrometric
measurements show that the companion has nearly completed one orbital
revolution since its discovery in 1997. The derived orbital elements
imply a short-period (P ≈ 11.3 yr) and high-eccentricity orbit
(e ≈ 0.6) with periastron passage around 2002.6. The new orbit
is consistent with recently published radial velocity measurements,
from which we can also derive the first direct constraints on the mass
ratio of the binary components. We employ various methods to derive
the system mass (M_system = 44 ± 7 M⊙) and the dynamical
distance (d = 410 ± 20 pc), which is in remarkably good agreement
with recently published trigonometric parallax measurements obtained
with radio interferometry. Based on observations made with
ESO telescopes at the La Silla Paranal Observatory under the OT and
VISA-MPG GTO programme IDs 078.C-0360(A), 080.C-0541(A,B,C,D),
080.D-0225(B), and 080.C-0388(A).
Title: Resolving the dusty torus and the mystery surrounding LMC
red supergiant WOH G64
Authors: Ohnaka, Keiichi; Driebe, Thomas; Hofmann, Karl-Heinz; Weigelt,
Gerd; Wittkowski, Markus
Bibcode: 2009IAUS..256..454O
Altcode:
We present mid-IR long-baseline interferometric observations of the red
supergiant WOH G64 in the Large Magellanic Cloud with MIDI at the ESO's
Very Large Telescope Interferometer (VLTI). Our MIDI observations of WOH
G64 are the first VLTI observations to spatially resolve an individual
stellar source in an extragalactic system. Our 2-D radiative transfer
modeling reveals the presence of a geometrically and optically thick
torus seen nearly pole-on. This model brings WOH G64 in much better
agreement with the current evolutionary tracks for a 25 M⊙
star — about a half of the previous estimate of 40 M⊙
— and solves the serious discrepancy between theory and observation
which existed for this object.
Title: Wolf-Rayet Stars at the Highest Angular Resolution
Authors: Millour, Florentin; Chesneau, Olivier; Driebe, Thomas; Matter,
Alexis; Schmutz, Werner; Lopez, Bruno; Petrov, Romain G.; Groh, José
H.; Bonneau, Daniel; Dessart, Luc; Hofmann, Karl-Heinz; Weigelt, Gerd
Bibcode: 2009Msngr.135...26M
Altcode:
Interferometric observations of high-mass evolved stars provide new and
very valuable information of their nature. With the unique capabilities
of the VLTI, direct images of their closest environment where mass
loss and dust formation occur, can be obtained. The breakthrough of
the VLTI in terms of angular resolution as well as spectral resolution
allows competing theoretical models, based on indirect constraints,
to be tested. The high angular resolution made available by the VLTI
shows that there is still a lot to discover about these massive stars.
Title: MATISSE Science Cases
Authors: Wolf, S.; Lopez, B.; Jaffe, W.; Weigelt, G.; Augereau,
J. -Ch.; Berruyer, N.; Chesneau, O.; Danchi, W. C.; Delbo, M.; Demyk,
K.; Domiciano, A.; Henning, Th.; Hofmann, K. -H.; Kraus, S.; Leinert,
Ch.; Linz, H.; Mathias, Ph.; Meisenheimer, K.; Menut, J. -L.; Millour,
F.; Mosoni, L.; Niedzielski, A.; Petrov, R.; Ratzka, Th.; Stecklum,
B.; Thiebaut, E.; Vakili, F.; Waters, L. B. F. M.; Absil, O.; Hron,
J.; Lagarde, S.; Matter, A.; Nardetto, N.; Olofsson, J.; Valat, B.;
Vannier, M.
Bibcode: 2009ASSP....9..359W
Altcode: 2009svlt.conf..359W
MATISSE is foreseen as a mid-infrared spectro-interferometric instrument
combining the beams of up to four UTs/ATs of the Very Large Telescope
Interferometer (VLTI). MATISSE will measure closure phase relations
and thus offer an efficient capability for image reconstruction. In
addition to this, MATISSE will open 2 new observing windows at the VLTI:
the L and M band in addition to the N band. Furthermore, the instrument
will offer the possibility to perform simultaneous observations in
separate bands. MATISSE will also provide several spectroscopic
modes. In summary, MATISSE can be seen as a successor of MIDI by
providing imaging capabilities in the mid-infrared domain (for a more
detailed description of MATISSE see Lopez et al., these proceedings).
Title: First IR-interferometric Study Of The Physical Properties Of
The Supergiant IRS 7 In The Particular Environment Of The Galactic
Center.
Authors: Pott, Jorg-Uwe; Ghez, A.; Weigelt, G.; Woillez, J.;
Wizinowich, P.
Bibcode: 2009AAS...21320407P
Altcode: 2009BAAS...41..267P
The first successful observations with an optical long baseline
interferometer of a supergiant in the Galactic center will be
presented. GCIRS 7 is resolved by the VLTI baselines at 2 and
10microns. Its interaction with its particular environment can be
studied. The unique L-band capabilities of the Keck interferometer
promise to give further insights in the life of a star under influence
of a supermassive black hole.
Title: Milli-arcsecond Astrophysics with VSI, the VLTI Spectro-imager
in the ELT Era
Authors: Malbet, F.; Buscher, D.; Weigelt, G.; Garcia, P.; Gai, M.;
Lorenzetti, D.; Surdej, J.; Hron, J.; Neuhäuser, R.; Kern, P.; Jocou,
L.; Berger, J. -P.; Absil, O.; Beckmann, U.; Corcione, L.; Duvert,
G.; Filho, M.; Labeye, P.; Le Coarer, E.; Li Causi, G.; Lima, J.;
Perraut, K.; Tatulli, E.; Thiébaut, E.; Young, J.; Zins, G.; Amorim,
A.; Aringer, B.; Beckert, T.; Benisty, M.; Bonfils, X.; Chelli, A.;
Chesneau, O.; Chiavassa, A.; Corradi, R.; de Becker, M.; Delboulbé,
A.; Duchêne, G.; Forveille, T.; Haniff, C.; Herwats, E.; Hofmann,
K. -H.; Le Bouquin, J. -B.; Ligori, S.; Loreggia, D.; Marconi, A.;
Moitinho, A.; Nisini, B.; Petrucci, P. -O.; Rebordao, J.; Speziali,
R.; Testi, L.; Vitali, F.
Bibcode: 2009ASSP....9..343M
Altcode: 2008arXiv0801.2694M; 2009svlt.conf..343M
Nowadays, compact sources relatively warm like surfaces of nearby
stars, circumstellar environments of stars from early stages to
the most evolved ones and surroundings of active galactic nuclei
can be investigated at milli-arcsecond scales only with the VLT in
its interferometric mode. We propose a spectro-imager, named VSI
(VLTI spectro-imager), which is capable to probe these sources both
over spatial and spectral scales in the near-infrared domain. This
instrument will provide information complementary to what is obtained
at the same time with ALMA at different wavelengths and the extreme
large telescopes.
Title: Possible evidence for a common radial structure in nearby
AGN tori
Authors: Kishimoto, M.; Hönig, S. F.; Tristram, K. R. W.; Weigelt, G.
Bibcode: 2009A&A...493L..57K
Altcode: 2008arXiv0812.1964K
We present a quantitative and relatively model-independent way to
assess the radial structure of nearby AGN tori. These putative tori
have been studied with long-baseline infrared (IR) interferometry, but
the spatial scales probed are different for different objects. They
are at various distances and also have different physical sizes that
apparently scale with the luminosity of the central engine. Here we look
at interferometric size information, or visibilities, as a function
of spatial scales normalized by the size of the inner torus radiu
R_in. This approximately eliminates luminosity and distance dependence
and, thus, provides a way to uniformly view the visibilities observed
for various objects and at different wavelengths. We can construct
a composite visibility curve over a wide range of spatial scales
if different tori share a common radial structure. The currently
available observations do suggest, independent of models, a common
radial surface brightness distribution in the mid-IR that is roughly of
a power-law form r-2 as a function of radius r and extends
to ~100 times R_in. Taking into account the temperature decrease toward
outer radii with a simple torus model, this corresponds to the radial
surface density distribution of dusty material directly illuminated
by the central engine roughly in the range between r0
and r-1. This should be tested with further data.
Title: VLTI-AMBER Observations of η Carinae with High Spatial
Resolution and Spectral Resolutions of λ/Δλ=1500 and 12
000*
Authors: Weigelt, G.; Kraus, S.; Driebe, T.; Hofmann, K. -H.; Millour,
F.; Petrov, R.; Schertl, D.; Chesneau, O.; Davidson, K.; Domiciano
de Souza, A.; Gull, T.; Hillier, J. D.; Malbet, F.; Rantakyrö, F.;
Richichi, A.; Schöller, M.; Wittkowski, M.
Bibcode: 2009ASSP....9..107W
Altcode: 2009svlt.conf..107W
We report spectro-interferometric observations of the Luminous Blue
Variable (LBV) η Car using the AMBER instrument of ESO's Very Large
Telescope Interferometer (VLTI) 1. The observations around the He I
2.059 μm and the Brγ 2.166 μm emission lines allow us to investigate
the wavelength dependence of the visibility, differential phase, and
closure phase of η Car's stellar wind region. If we fit visibility
profiles derived from Hillier et al. models 2 to the AMBER visibilities,
we obtain 50% encircled-energy diameters of 4.3, 6.5, and 9.6 mas
in the 2.17 μm continuum, the He I, and the Brγ emission lines,
respectively. For the interpretation of the non-zero differential and
closure phases measured within the Brγ line, we developed a simple
wind model. Our observations support theoretical models of winds from
fast-rotating, luminous hot stars.
Title: Matisse
Authors: Lopez, B.; Lagarde, S.; Wolf, S.; Jaffe, W.; Weigelt, G.;
Antonelli, P.; Abraham, P.; Augereau, J. -Ch.; Beckman, U.; Behrend,
J.; Berruyer, N.; Bresson, Y.; Chesneau, O.; Clausse, J. M.; Connot,
C.; Danchi, W. C.; Delbo, M.; Demyk, K.; Domiciano, A.; Dugué, M.;
Glazenborg, A.; Graser, U.; Hanenburg, H.; Henning, Th.; Heininger,
M.; Hofmann, K. -H.; Hugues, Y.; Jankov, S.; Kraus, S.; Laun, W.;
Leinert, Ch.; Linz, H.; Matter, A.; Mathias, Ph.; Meisenheimer, K.;
Menut, J. -L.; Millour, F.; Mosoni, L.; Neumann, U.; Niedzielski, A.;
Nussbaum, E.; Petrov, R.; Ratzka, Th.; Robbe-Dubois, S.; Roussel, A.;
Schertl, D.; Schmider, F. -X.; Stecklum, B.; Thiebaut, E.; Vakili,
F.; Wagner, K.; Waters, L. B. F. M.; Absil, O.; Hron, J.; Nardetto,
N.; Olofsson, J.; Valat, B.; Vannier, M.; Goldman, B.; Hönig, S.;
Cotton, W. D.
Bibcode: 2009ASSP....9..353L
Altcode: 2009svlt.conf..353L
MATISSE is foreseen as a mid-infrared spectro-interferometer
combining the beams of up to four UTs/ATs of the Very Large Telescope
Interferometer (VLTI). MATISSE will measure closure phase relations and
thus offer an efficient capability for image reconstruction in the L,
M and N bands of the mid-infrared domain.
Title: A Mid-infrared Interferometric Study of the Circumstellar
Environment of Dusty OH/IR Stars with VLTI/MIDI
Authors: Driebe, T.; Ohnaka, K.; Murakawa, K.; Hofmann, K. -H.;
Schertl, D.; Weigelt, G.; Verhoelst, T.; Chesneau, O.; Domiciano de
Souza, A.; Riechers, D.; Schöller, M.; Wittkowski, M.
Bibcode: 2009ASSP....9..125D
Altcode: 2009svlt.conf..125D
OH/IR stars are evolved stars exhibiting large infrared excess as well
as prominent OH maser emission. The vast majority of this heterogeneous
object class are highly-evolved low- and intermediate-mass stars
ascending the upper part of the asymptotic giant branch (AGB). Thus,
these stars are in the final phase of their AGB evolution which
is characterized by intensive mass loss with mass-loss rates that
can reach up to 10-4 M⊙. This high mass
loss leads to the development of an extended, usually optically
thick dusty circumstellar envelope which can be well studied with
infrared-interferometric observations.
Title: Multi-epoch VLTI/MIDI Observations of the Carbon-rich Mira
Star V Oph
Authors: Ohnaka, K.; Driebe, T.; Weigelt, G.; Wittkowski, M.
Bibcode: 2009ASSP....9..119O
Altcode: 2009svlt.conf..119O
The driving mechanism of mass outflows in Mira variables has not
yet been fully understood. Recent progress in optical and infrared
interferometric techniques has been contributing to studies of the
region between the top of the photosphere and the innermost region of
the circumstellar dust shell, exactly where mass outflows are expected
to be initiated. Infrared interferometric observations of oxygen-rich
Mira stars have spatially resolved dense, warm (∼1000-2000 K)
molecular layers consisting of H2O, SiO, and CO and
extending to ∼2-3 R ⋆ (e.g., Mennesson et al. 1;
Perrin et al. 6; Ohnaka et al. 4). The optically thick emission from
the warm molecular layers affect the apparent size of Mira stars: the
object appears larger than the star itself at wavelengths where the
opacities of the above molecular species are higher. In particular,
H2O has strong spectral features in the mid-infrared,
which causes the angular size to increase from the near-infrared to
the mid-infrared as observed toward oxygen-rich Miras.
Title: HK-band imaging polarimetry and radiative transfer modeling
of the massive young stellar object CRL 2136
Authors: Murakawa, K.; Preibisch, T.; Kraus, S.; Weigelt, G.
Bibcode: 2008A&A...490..673M
Altcode:
Aims: We investigate the physical properties of the dust environment of
the massive proto-stellar object CRL 2136 by means of two-dimensional
radiative transfer modeling, which combines fitting of the spectral
energy distribution, the intensity images, and the polarization
images.
Methods: We obtained polarimetric images of CRL 2136
in the H and K bands using the CIAO instrument on the 8 m Subaru
telescope. We developed a new Monte Carlo code which can deal with
multiple-grain models and computes the SED, the dust temperature, and
the Stokes IQUV images. With this code, we performed two-dimensional
modeling of CRL 2136's circumstellar disk and envelope.
Results:
Our images show a compact infrared source, two bright lobes extending
towards the south and east, and two faint lobes extending towards the
northwest and west. The polarization images show a polarization disk
near the central star with a position angle of ~ -135°, a polarization
vector alignment approximately parallel to the polarization disk, and
a region with low polarization between the eastern and the southern
lobes. In our modeling, we assume three grain models: bare grains,
warm grains with a crystalline water ice mantle, and cold grains with
an amorphous water ice mantle. We obtained a maximum grain core size of
0.45 μm. We found that the CRL 2136 disk has a low disk mass of 0.007
M⊙, a large radius of 2000 AU, a scale height of 1.0,
and a low accretion rate of 2.1 × 10-7 M⊙
yr-1 compared to an envelope mass infall rate of 1.0 ×
10-4 M⊙ yr-1.
Conclusions: The
predicted environment of the disk and the envelope is consistent with a
scenario in which the central star forms rapidly (~ 2 × 105
yr), with a high mass infalling rate, and nearly isotropically (large
disk scale height) in the early phase. Then, the accretion of the disk
matter is prevented by the strong radiation pressure from the luminous
central star, resulting in a low disk mass and a low accretion rate.
Title: Near-IR bispectrum speckle interferometry, AO imaging
polarimetry, and radiative transfer modeling of the proto-planetary
nebula Frosty Leonis
Authors: Murakawa, K.; Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Oya,
S.; Schertl, D.; Weigelt, G.
Bibcode: 2008A&A...489..195M
Altcode:
Aims: We combined bispectrum speckle interferometry, adaptive optics
(AO) imaging polarimetry, and radiative transfer modeling of polarized
light to derive various physical properties of the proto-planetary
nebula Frosty Leo.
Methods: We performed bispectrum K'-band
speckle interferometry and H- and K-band imaging polarimetry of
Frosty Leo using the ESO 3.6 m telescope and the AO-equipped CIAO
instrument of the 8 m Subaru telescope, respectively. Two-dimensional
radiative transfer modeling was carried out in order to obtain a
quantitative interpretation of our observations.
Results: Our
diffraction-limited speckle image shows distinct hourglass-shaped,
point-symmetric bipolar lobes, an equatorial dust lane, and complex
clumpy structures in the lobes. Our polarimetric data display a
centro-symmetric polarization vector pattern with P~30-50% in the
bipolar lobes and a polarization disk between them. The polarization
images also reveal an elongated region with low polarization along
a position angle of -45°. The observations suggest that this region
has a low dust density and was carved out by a jet-like outflow. Our
radiative transfer modeling can simultaneously explain the observed
spectral energy distribution, the intensity distribution of the
hourglass-shaped lobes, and our polarization images if we use two grain
species with sizes of 0.005 ≤ a ≤ 2.0 μm at latitudes between -2°
and +2°, and 0.005 ≤ a ≤ 0.7 μm in the bipolar lobes. Assuming
a distance of 3 kpc, an expansion velocity of 25 km s-1,
and a gas-to-dust mass ratio of 160, we derive a dust mass of the
disk of 2.85×10-3 M⊙, a gas mass-loss rate
of 8.97×10-3 M⊙ yr-1, and a total
envelope mass of 4.23 M⊙.
Title: Asymmetric silicate dust distribution toward the silicate
carbon star BM Geminorum
Authors: Ohnaka, K.; Izumiura, H.; Leinert, Ch.; Driebe, T.; Weigelt,
G.; Wittkowski, M.
Bibcode: 2008A&A...490..173O
Altcode: 2008arXiv0807.3342O
Context: Despite their carbon-rich photospheres, silicate carbon
stars show 10 μm silicate emission. They are considered to have
circumbinary or circum-companion disks, which serve as a reservoir
of oxygen-rich material shed by mass loss in the past.
Aims:
We present N-band spectro-interferometric observations of the silicate
carbon star BM Gem using MIDI at the Very Large Telescope Interferometer
(VLTI). Our aim is to probe the spatial distribution of oxygen-rich
dust at high spatial resolution.
Methods: Using the UT2-UT3 and
UT3-UT4 configurations, BM Gem was observed with VLTI/MIDI at 44-62
m baselines.
Results: The N-band visibilities observed for BM
Gem decrease steeply between 8 and ~10 μm and increase gradually
longward of ~10 μm, reflecting the optically thin silicate emission
feature emanating from sub-micron-sized amorphous silicate grains. The
differential phases obtained at baselines of ~44-46 m show significant
non-zero values (∼ -70°) in the central part of the silicate emission
feature between ~9 and 11 μm, revealing a photocenter shift and the
asymmetric nature of the silicate emitting region. The observed N-band
visibilities and differential phases can be described adequately by a
simple geometrical model in which the unresolved star is surrounded
by a ring with azimuthal brightness modulation. The best-fit model
is characterized by a broad ring (~70 mas across at 10 μm) with
a bright region offset from the unresolved star by ~20 mas at a
position angle of ~280°. This model can be interpreted as a system
with a circum-companion disk and is consistent with the spectroscopic
signatures of an accretion disk around an unseen companion, which were
discovered in the violet spectrum of BM Gem. Based on observations
made with the Very Large Telescope Interferometer of the European
Southern Observatory. Program ID: 078.D-0292.
Title: VizieR Online Data Catalog: Speckle interferometry of nearby
multiples (Balega+, 2007)
Authors: Balega, I. I.; Balega, Yu. Yu.; Maksimov, A. F.; Malogolovets,
E. V.; Rastegaev, D. A.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2008yCatp033006203B
Altcode:
The results of speckle interferometric observations of 104 binary
and 6 triple stars performed at the BTA 6m telescope in 2004 October
are presented. Nearby low-mass stars are mostly observed for the
program, among which 59 there are new binaries recently discovered
by the Hipparcos astrometric satellite. Concurrently with the
diffraction-limited position measurements we obtained 154 brightness
ratio measurements of binary and multiple star components in different
bands of the visible spectrum. New, first-resolved binaries are the
symbiotic star CH Cyg with a weak companion at 0.043" separation and
the pair of red dwarfs, GJ 913 = HIP 118212. In addition, we derived
the orbital parameters for two interferometric systems: the CN-giant
pair HD 210211 = HIP 109281 (P=10.7yr) and the G2V-K2V G2V-K2V binary
GJ 9830 = HIP 116259 (P=15.7yr). (2 data files).
Title: The origin of hydrogen line emission for five Herbig Ae/Be
stars spatially resolved by VLTI/AMBER spectro-interferometry
Authors: Kraus, S.; Hofmann, K. -H.; Benisty, M.; Berger, J. -P.;
Chesneau, O.; Isella, A.; Malbet, F.; Meilland, A.; Nardetto, N.;
Natta, A.; Preibisch, T.; Schertl, D.; Smith, M.; Stee, P.; Tatulli,
E.; Testi, L.; Weigelt, G.
Bibcode: 2008A&A...489.1157K
Altcode: 2008arXiv0807.1119K
Context: Accretion and outflow processes are of fundamental
importance for our understanding of the formation of stars and
planetary systems. To trace these processes, diagnostic spectral
lines such as the Brγ 2.166 μm line are widely used, although due
to a lack of spatial resolution, the origin of the line emission is
still unclear.
Aims: Employing the AU-scale spatial resolution
which can be achieved with infrared long-baseline interferometry,
we aim to distinguish between theoretical models which associate
the Brγ line emission with mass infall (magnetospheric accretion,
gaseous inner disks) or mass outflow processes (stellar winds, X-winds,
or disk winds).
Methods: Using the VLTI/AMBER instrument, we
spatially and spectrally (λ/Δλ = 1500) resolved the inner (⪉5
AU) environment of five Herbig Ae/Be stars (HD 163296, HD 104237,
HD 98922, MWC 297, V921 Sco) in the Brγ emission line as well as
in the adjacent continuum. From the measured wavelength-dependent
visibilities, we derive the characteristic size of the continuum and
Brγ line-emitting region. Additional information is provided by the
closure phase, which we could measure both in the continuum wavelength
regime (for four objects) as well as in the spectrally resolved
Brγ emission line (for one object). The spectro-interferometric
data is supplemented by archival and new VLT/ISAAC spectroscopy.
Results: For all objects (except MWC 297), we measure an increase
of visibility within the Brγ emission line, indicating that the
Brγ-emitting region in these objects is more compact than the dust
sublimation radius. For HD 98922, our quantitative analysis reveals
that the line-emitting region is compact enough to be consistent
with the magnetospheric accretion scenario. For HD 163296, HD 104237,
MWC 297, and V921 Sco we identify an extended stellar wind or a disk
wind as the most likely line-emitting mechanism. Since the stars in
our sample cover a wide range of stellar parameters, we also search
for general trends and find that the size of the Brγ-emitting region
does not seem to depend on the basic stellar parameters (such as the
stellar luminosity), but correlates with spectroscopic properties,
in particular with the Hα line profile shape.
Conclusions: By
performing the first high-resolution spectro-interferometric survey
on Herbig Ae/Be stars, we find evidence for at least two distinct Brγ
line-formation mechanisms. Most significant, stars with a P-Cygni Hα
line profile and a high mass-accretion rate seem to show particularly
compact Brγ-emitting regions (RBrγ/Rcont
< 0.2), while stars with a double-peaked or single-peaked Hα-line
profile show a significantly more extended Brγ-emitting region (0.6
⪉ RBrγ/Rcont ⪉ 1.4), possibly tracing
a stellar wind or a disk wind. Based on observations made
with ESO telescopes at the La Silla Paranal Observatory under open time programme IDs 077.C-0694, 078.C-0360, and 078.C-0680.
Title: VLT/NACO and Subaru/CIAO JHK-band high-resolution imaging
polarimetry of the Herbig Be star R Monocerotis
Authors: Murakawa, K.; Preibisch, T.; Kraus, S.; Ageorges, N.; Hofmann,
K. -H.; Ishii, M.; Oya, S.; Rosen, A.; Schertl, D.; Weigelt, G.
Bibcode: 2008A&A...488L..75M
Altcode:
Aims: We investigate the dust properties of the disk and envelope of
the Herbig Be star R Mon by means of near-infrared multiwavelength
imaging polarimetry.
Methods: We obtained JHK-band polarimetric
images using the adaptive optics instruments NACO on the VLT, and CIAO
on the Subaru telescope.
Results: Our NACO JK_S-band images of
~0.1 arcsec angular resolution resolve clearly the R Mon binary system
as well as twisted string-like features in the fan-shaped lobe. The
polarimetric images reveal a butterfly-shaped polarization disk with
an almost constant shape and an extension of 4 arcsec in the J, H,
and K bands. In this region, the polarization values are as low as
P_J∼7%, P_H∼2%, and P_K∼1%, and the polarization vectors are not
systematically aligned along the equatorial plane. On the other hand,
highly polarized scattered light is detected in the fan-shaped lobe
(PJ ∼24%, PH ∼ 33%, and P_K∼53%).
Conclusions: Our polarimetric data suggests the presence of multiple
grain populations in the R Mon nebula. From our one-dimensional single
scattering modeling, the maximum grain size in the nebula at large
scale is estimated to be 0.23 μm. On the other hand, the aforementioned
properties of the polarization disk and a nearly spherical appearance
of the nebulosity close to the central star suggests the presence of
large grains (micron-size or larger) in the polarization disk.
Title: First VLTI infrared spectro-interferometry on GCIRS
7. Characterizing the prime reference source for Galactic center
observations at highest angular resolution
Authors: Pott, J. -U.; Eckart, A.; Glindemann, A.; Kraus, S.; Schödel,
R.; Ghez, A. M.; Woillez, J.; Weigelt, G.
Bibcode: 2008A&A...487..413P
Altcode: 2008arXiv0805.4408P
Context: The massive black hole Sgr A* at the very center of the
Galaxy, and its immediate stellar and non-stellar environment,
have been studied in the past decade with increasing intensity and
wavelength coverage, revealing surprising results. This research
requires the highest angular resolution available to avoid source
confusion and to study the physical properties of the objects.
Aims: GCIRS 7 is the dominating star of the central cluster in the
NIR, so it has been used as wavefront and astrometric reference. Our
studies investigate, for the first time, its properties at 2 and 10
μm using the VLTI. We aim at analyzing the suitability of GCIRS 7
as an interferometric phase-reference for the upcoming generation
of dual-field facilities at optical interferometers.
Methods:
VLTI-AMBER and MIDI instruments were used to spatially resolve GCIRS
7 and to measure the wavelength dependence of the visibility using the
low spectral resolution mode (λ / Δ λ ≈ 30) and projected baseline
lengths of about 50 m, resulting in an angular resolution of about
9 mas and 45 mas for the NIR and MIR, respectively.
Results:
The first K-band fringe detection of a GC star suggests that GCIRS 7
could be marginally resolved at 2 micron, which would imply that the
photosphere of the supergiant is enshrouded by a molecular and dusty
envelope. At 10 μm, GCIRS 7 is strongly resolved with a visibility of
approximately 0.2. The MIR is dominated by moderately warm (200 K),
extended dust, mostly distributed outside of a radius of about 120
AU (15 mas) around the star. A deep 9.8 μm-silicate absorption in
excess of the usual extinction law with respect to the NIR extinction
has been found.
Conclusions: Our VLTI observations show that
interferometric NIR phase-referencing experiments with mas resolution
using GCIRS 7 as phase reference appear to be feasible, but more such
studies are required to definitely characterize the close environment
around this star. The MIR data confirm recent findings of a relatively
enhanced, interstellar 9.8 μm-silicate absorption with respect to
the NIR extinction towards another star in the central arc-seconds,
suggesting an unusual dust composition in that region. We demonstrate
that the resolution and sensitivity of modern large-aperture optical
telescope arrays is required to resolve the innermost environment of
stars at the Galactic center. Based on observations collected
at the European Southern Observatory, Paranal, Chile (programs
076.B-0863, 077.D-0709).
Title: The structure of the Winds of Eta Carinae as seen by HST/STIS
and VLTI/AMBER
Authors: Nielsen, K. E.; Weigelt, G.; Gull, T. R.; Corcoran, M. F.;
Driebe, T.; Kraus, S.; Hamaguchi, K.; Hillier, D. J.
Bibcode: 2008RMxAC..33..136N
Altcode:
Eta Carinae (η Car) is currently understood to be a massive binary,
within an extended wind, engulfed by its ejecta.
Title: Probing the dusty environment of the Seyfert 1 nucleus in
NGC 3783 with MIDI/VLTI interferometry
Authors: Beckert, T.; Driebe, T.; Hönig, S. F.; Weigelt, G.
Bibcode: 2008A&A...486L..17B
Altcode: 2008arXiv0806.0531B
Aims: We present mid-IR spectro-interferometry of the Seyfert type
1 nucleus of NGC 3783. The dusty circumnuclear
environment is spatially resolved and the wavelength dependence of
the compact emission is discussed.
Methods: The observations
were carried out with the MIDI instrument at the Very Large Telescope
Interferometer in the N-band. Spectra and visibilities were derived
with a spectral resolution of λ/Δλ ~ 30 in the wavelength range
from 8 to 13 μm. For the interpretation we developed a simple dusty
disk model with a small and variable covering factor.
Results:
At baselines of 65 and 69 m, visibilities in the range of 0.4 to
0.7 were measured. The N-band spectra show a monotonic increase of
the measured flux with wavelength with no apparent silicate feature
around 10 μm. We find that the mid-IR emission from the nucleus can
be reproduced by an extended dust disk or torus with a small covering
factor of the radiating dust clouds.
Conclusions: Our mid-IR
observations of NGC 3783 are consistent with a clumpy circumnuclear
dust environment. The interpretation in terms of a dusty torus with
a low covering factor supports a clumpy version of the unified scheme
for AGN. The inferred sizes and luminosities are in good agreement with
dust reverberation sizes and bolometric luminosities from optical and
X-ray observations.
Title: VSI: the VLTI spectro-imager
Authors: Malbet, F.; Buscher, D.; Weigelt, G.; Garcia, P.; Gai, M.;
Lorenzetti, D.; Surdej, J.; Hron, J.; Neuhäuser, R.; Kern, P.; Jocou,
L.; Berger, J. -P.; Absil, O.; Beckmann, U.; Corcione, L.; Duvert,
G.; Filho, M.; Labeye, P.; Le Coarer, E.; Li Causi, G.; Lima, J.;
Perraut, K.; Tatulli, E.; Thiébaut, E.; Young, J.; Zins, G.; Amorim,
A.; Aringer, B.; Beckert, T.; Benisty, M.; Bonfils, X.; Cabral, A.;
Chelli, A.; Chesneau, O.; Chiavassa, A.; Corradi, R.; De Becker, M.;
Delboulbé, A.; Duchêne, G.; Forveille, T.; Haniff, C.; Herwats,
E.; Hofmann, K. -H.; Le Bouquin, J. -B.; Ligori, S.; Loreggia, D.;
Marconi, A.; Moitinho, A.; Nisini, B.; Petrucci, P. -O.; Rebordao,
J.; Speziali, R.; Testi, L.; Vitali, F.
Bibcode: 2008SPIE.7013E..29M
Altcode: 2008SPIE.7013E..68M; 2008arXiv0807.1062M
The VLTI Spectro Imager (VSI) was proposed as a second-generation
instrument of the Very Large Telescope Interferometer providing
the ESO community with spectrally-resolved, near-infrared images
at angular resolutions down to 1.1 milliarcsecond and spectral
resolutions up to R = 12000. Targets as faint as K = 13 will be
imaged without requiring a brighter nearby reference object; fainter
targets can be accessed if a suitable reference is available. The
unique combination of high-dynamic-range imaging at high angular
resolution and high spectral resolution enables a scientific program
which serves a broad user community and at the same time provides the
opportunity for breakthroughs in many areas of astrophysics. The high
level specifications of the instrument are derived from a detailed
science case based on the capability to obtain, for the first time,
milliarcsecond-resolution images of a wide range of targets including:
probing the initial conditions for planet formation in the AU-scale
environments of young stars; imaging convective cells and other
phenomena on the surfaces of stars; mapping the chemical and physical
environments of evolved stars, stellar remnants, and stellar winds;
and disentangling the central regions of active galactic nuclei and
supermassive black holes. VSI will provide these new capabilities
using technologies which have been extensively tested in the past and
VSI requires little in terms of new infrastructure on the VLTI. At the
same time, VSI will be able to make maximum use of new infrastructure
as it becomes available; for example, by combining 4, 6 and eventually
8 telescopes, enabling rapid imaging through the measurement of up to
28 visibilities in every wavelength channel within a few minutes. The
current studies are focused on a 4-telescope version with an upgrade
to a 6-telescope one. The instrument contains its own fringe tracker
and tip-tilt control in order to reduce the constraints on the VLTI
infrastructure and maximize the scientific return.
Title: Science case for 1 mas spectro-imagining in the near-infrared
Authors: Garcia, Paulo J. V.; Berger, Jean-Philippe; Marconi,
Alessandro; Krivov, Alexander; Chiavassa, Andrea; Aringer, Bernard;
Nisini, Brunella; Defrére, Denis; Mawet, Dimitri; Schertl, Dieter;
Tatuli, Eric; Thiébaut, Eric; Baron, Fabien; Malbet, Fabien;
Duchéne, Gaspard; Weigelt, Gerd; Duvert, Gilles; Henri, Gilles;
Klahr, Hubert; Surdej, Jean; Augereau, Jean-Charles; Claeskens,
Jean-François; Young, John; Hron, Josef; Perraut, Karine; Hofmann,
Karl-Heinz; Testi, Leonardo; Cunha, Margarida; Filho, Mercedes;
De Becker, Michaël; Absil, Olivier; Chesneau, Olivier; Collette,
Pierre; Petrucci, Pierre-Olivier; Neuhaeuser, Ralph; Corradi, Romano;
Antón, Sónia; Wolf, Sebastian; Hoenig, Sebastian; Renard, Stephanie;
Forveille, Thierry; Beckert, Thomas; Lebzelter, Thomas; Harries, Tim;
Borkowski, Virginie; Bonfils, Xavier
Bibcode: 2008SPIE.7013E..4NG
Altcode: 2008SPIE.7013E.146G
We present the work developed within the science team of the Very
Large Telescope Interferometer Spectro-Imager (VSI) during the Phase
A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data
cubes in the near-infrared, with several spectral resolutions up to
12 000, by combining up to 8 VLTI telescopes. In the design of an
instrument, the science case plays a central role by supporting the
instrument construction decision, defining the top-level requirements
and balancing design options. The overall science philosophy of VSI was
that of a general user instrument serving a broad community. The science
team addressed themes which included several areas of astrophysics
and illustrated specific modes of operation of the instrument: a)
YSO disks and winds; b) Multiplicity of young stars; c) Exoplanets;
d) Debris disks; e) Stellar surface imaging; f) The environments of
evolved stars; g) AGN tori; h) AGN's Broad Line Region; i) Supermassive
black-holes; and j) Microlensing. The main conclusions can be summarized
as follows: a) The accessible targets and related science are extremely
sensitive to the instrument limiting magnitude; the instrument should be
optimized for sensitivity and have its own fringe tracker. b) Most of
the science cases are readily achievable with on-axis fringe tracking,
off-axis fringe tracking enabling extra science. c) In most targets
(YSOs, evolved stars and AGNs), the interpretation and analysis of
circumstellar/nuclear dust morphology requires direct access to the gas
via spectral resolved studies of emission lines, requiring at least a
spectral resolution of 2 500. d) To routinely deliver images at the
required sensitivity, the number of telescopes in determinant, with
6 telescopes being favored. e) The factorial increase in the number
of closure phases and visibilities, gained in a single observation,
makes massive surveys of parameters and related science for the first
time possible. f) High dynamic range imaging and very high dynamic
range differential closure phase are possible allowing the study of
debris disks and characterization of pegasides. g) Spectro-imaging
in the near-infrared is highly complementary to ALMA, adaptive optics
and interferometric imaging in the thermal infrared.
Title: MATISSE: perspective of imaging in the mid-infrared at the VLTI
Authors: Lopez, B.; Antonelli, P.; Wolf, S.; Lagarde, S.; Jaffe,
W.; Navarro, R.; Graser, U.; Petrov, R.; Weigelt, G.; Bresson, Y.;
Hofmann, K. H.; Beckman, U.; Henning, T.; Laun, W.; Leinert, Ch.;
Kraus, S.; Robbe-Dubois, S.; Vakili, F.; Richichi, A.; Abraham, P.;
Augereau, J. -C.; Behrend, J.; Berio, Ph.; Berruyer, N.; Chesneau,
O.; Clausse, J. M.; Connot, C.; Demyk, K.; Danchi, W. C.; Dugué, M.;
Finger, G.; Flament, S.; Glazenborg, A.; Hannenburg, H.; Heininger,
M.; Hugues, Y.; Hron, J.; Jankov, S.; Kerschbaum, F.; Kroes, G.; Linz,
H.; Lizon, J. -L.; Mathias, Ph.; Mathar, R.; Matter, A.; Menut, J. L.;
Meisenheimer, K.; Millour, F.; Nardetto, N.; Neumann, U.; Nussbaum,
E.; Niedzielski, A.; Mosoni, L.; Olofsson, J.; Rabbia, Y.; Ratzka, T.;
Rigal, F.; Roussel, A.; Schertl, D.; Schmider, F. -X.; Stecklum, B.;
Thiebaut, E.; Vannier, M.; Valat, B.; Wagner, K.; Waters, L. B. F. M.
Bibcode: 2008SPIE.7013E..2BL
Altcode: 2008SPIE.7013E..70L
MATISSE is foreseen as a mid-infrared spectro-interferometer
combining the beams of up to four UTs/ATs of the Very Large Telescope
Interferometer (VLTI) of the European Southern Observatory. The
related science case study demonstrates the enormous capability of a
new generation mid-infrared beam combiner. MATISSE will constitute
an evolution of the two-beam interferometric instrument MIDI. MIDI
is a very successful instrument which offers a perfect combination
of spectral and angular resolution. New characteristics present in
MATISSE will give access to the mapping and the distribution of the
material (typically dust) in the circumstellar environments by using
a wide mid-infrared band coverage extended to L, M and N spectral
bands. The four beam combination of MATISSE provides an efficient
UV-coverage : 6 visibility points are measured in one set and 4 closure
phase relations which can provide aperture synthesis images in the
mid-infrared spectral regime.
Title: LINC-NIRVANA: the Fizeau interferometer for the Large
Binocular Telescope
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2008SPIE.7013E..26H
Altcode: 2008SPIE.7013E..65H
LINC-NIRVANA is an innovative imaging interferometer fed by dedicated
multi-conjugated adaptive optics systems. The instrument combines the
light of the two, 8.4-meter primary mirrors of the Large Binocular
Telescope (LBT) on a single focal plane, providing panoramic imagery
with 23-meter spatial resolution. LINC-NIRVANA is entering its
final integration phase, with the large adaptive-optics and imaging
subsystems coming together in the clean room in Heidelberg. Here, we
report on progress, including insights gained on instrument assembly
and vibration control.
Title: LINC-NIRVANA: achieving 10 mas imagery on the Large Binocular
Telescope
Authors: Herbst, T. M.; Ragazzoni, R.; Eckart, A.; Weigelt, G.
Bibcode: 2008SPIE.7014E..1AH
Altcode: 2008SPIE.7014E..43H
LINC-NIRVANA is an innovative imaging interferometer fed by dedicated
multi-conjugated adaptive optics systems. The instrument combines the
light of the two, 8.4-meter primary mirrors of the Large Binocular
Telescope (LBT) on a single focal plane, providing panoramic imagery
with 23-meter spatial resolution. The instrument employs a number of
innovative technologies, including multi-conjugated adaptive optics,
state-of-the-art materials, low vibration mechanical coolers,
active and passive control, and sophisticated software for data
analysis. LINC-NIRVANA is entering its final integration phase, with
the large adaptive-optics and imaging subsystems coming together in
the clean room in Heidelberg. Here, we report on progress, including
insights gained on integration of large instruments.
Title: Wolf-Rayet stars probed by AMBER/VLTI
Authors: Millour, Florentin; Chesneau, Olivier; Driebe, Thomas;
Petrov, Romain G.; Bonneau, Daniel; Dessart, Luc; Hofmann, Karl-Heinz;
Weigelt, Gerd
Bibcode: 2008SPIE.7013E..0TM
Altcode: 2008arXiv0807.0293M; 2008SPIE.7013E..24M
Massive stars deeply influence their surroundings by their luminosity
and the injection of kinetic energy. So far, they have mostly been
studied with spatially unresolved observations, although evidence of
geometrical complexity of their wind are numerous. Interferometry
can provide spatially resolved observations of massive stars
and their immediate vicinity. Specific geometries (disks, jets,
latitude-dependent winds) can be probed by this technique. The first
observation of a Wolf-Rayet (WR) star (γ2 Vel) with the
AMBER/VLTI instrument yielded to a re-evaluation of its distance and
an improved characterization of the stellar components, from a very
limited data-set. This motivated our team to increase the number of WR
targets observed with AMBER. We present here new preliminary results
that encompass several spectral types, ranging from early WN to evolved
dusty WC. We present unpublished data on WR79a, a massive star probably
at the boundary between the O and Wolf-Rayet type, evidencing some
Wolf-Rayet broad emission lines from an optically thin wind. We also
present new data obtained on γ2 Vel that can be compared
to the up-to-date interferometry-based orbital parameters from North
et al. (2007). We discuss the presence of a wind-wind collision zone
in the system and provide preliminary analysis suggesting the presence
of such a structure in the data. Then, we present data obtained on 2
dusty Wolf-Rayet stars: WR48a-b and WR118, the latter exhibiting some
clues of a pinwheel-like structure from the visibility variations.
Title: Discovery of a strong Baldwin effect in mid-infrared AGN lines
Authors: Hönig, S. F.; Smette, A.; Beckert, T.; Horst, H.; Duschl,
W.; Gandhi, P.; Kishimoto, M.; Weigelt, G.
Bibcode: 2008A&A...485L..21H
Altcode: 2008arXiv0805.2151H
We present the discovery of a Baldwin effect in 8 nearby Seyfert
galaxies for the three most prominent mid-infrared forbidden emission
lines observable from the ground that are commonly found in AGN,
[AR III](λ8.99 μm), [S IV](λ10.51 μm), and [Ne II](λ12.81
μm). The observations were carried out using the VLT/VISIR imager
and spectrograph at the ESO/Paranal observatory. The bulk of the
observed line emission originates in the innermost region within a
diameter of 0.4 arcsec, which corresponds to spatial scales of less
than 100 pc within the targeted galaxies. The correlation index is
approximately -0.6 and does not vary significantly for all lines
studied. To date, this is the strongest anticorrelation that has been
measured between line equivalent width and continuum luminosity. In
the case of Circinus, we show that, despite using mid-infrared lines,
obscuration by either the host galaxy or the circumnuclear dust torus
might affect the measurement. Given the small observed spatial scales
from which most of the line emission emanates, it is unclear how
well these observations agree with the favored “disappearing NLR”
scenario for the narrow-line Baldwin effect. Based on ESO observing
programmes 078.B-0303, 080.B-0240, and the DDT program 280.B-5068.
Title: Phase closure image reconstruction for future VLTI
instrumentation
Authors: Filho, Mercedes E.; Renard, Stephanie; Garcia, Paulo; Duvert,
Gilles; Duchene, Gaspard; Thiebaut, Eric; Young, John; Absil, Olivier;
Berger, Jean-Phillipe; Beckert, Thomas; Hoenig, Sebastian; Schertl,
Dieter; Weigelt, Gerd; Testi, Leonardo; Tatuli, Eric; Borkowski,
Virginie; de Becker, Michaël; Surdej, Jean; Aringer, Bernard;
Hron, Joseph; Lebzelter, Thomas; Chiavassa, Andrea; Corradi, Romano;
Harries, Tim
Bibcode: 2008SPIE.7013E..3ZF
Altcode: 2008arXiv0810.0549F; 2008SPIE.7013E.123F
Classically, optical and near-infrared interferometry have relied on
closure phase techniques to produce images. Such techniques allow us
to achieve modest dynamic ranges. In order to test the feasibility
of next generation optical interferometers in the context of the
VLTI-spectro-imager (VSI), we have embarked on a study of image
reconstruction and analysis. Our main aim was to test the influence
of the number of telescopes, observing nights and distribution of
the visibility points on the quality of the reconstructed images. Our
results show that observations using six Auxiliary Telescopes (ATs)
during one complete night yield the best results in general and
is critical in most science cases; the number of telescopes is the
determining factor in the image reconstruction outcome. In terms of
imaging capabilities, an optical, six telescope VLTI-type configuration
and ~200 meter baseline will achieve 4 mas spatial resolution, which is
comparable to ALMA and almost 50 times better than JWST will achieve at
2.2 microns. Our results show that such an instrument will be capable
of imaging, with unprecedented detail, a plethora of sources, ranging
from complex stellar surfaces to microlensing events.
Title: Phase referencing in optical interferometry
Authors: Filho, Mercedes E.; Garcia, Paulo; Duvert, Gilles; Duchene,
Gaspard; Thiebaut, Eric; Young, John; Absil, Olivier; Berger,
Jean-Phillipe; Beckert, Thomas; Hoenig, Sebastian; Schertl, Dieter;
Weigelt, Gerd; Testi, Leonardo; Tatuli, Eric; Borkowski, Virginie;
de Becker, Michaël; Surdej, Jean; Aringer, Bernard; Hron, Joseph;
Lebzelter, Thomas; Chiavassa, Andrea; Corradi, Romano; Harries, Tim
Bibcode: 2008SPIE.7013E..1FF
Altcode: 2008SPIE.7013E..40F; 2008arXiv0810.0545F
One of the aims of next generation optical interferometric
instrumentation is to be able to make use of information contained
in the visibility phase to construct high dynamic range images. Radio
and optical interferometry are at the two extremes of phase corruption
by the atmosphere. While in radio it is possible to obtain calibrated
phases for the science objects, in the optical this is currently not
possible. Instead, optical interferometry has relied on closure phase
techniques to produce images. Such techniques allow only to achieve
modest dynamic ranges. However, with high contrast objects, for faint
targets or when structure detail is needed, phase referencing techniques
as used in radio interferometry, should theoretically achieve higher
dynamic ranges for the same number of telescopes. Our approach is
not to provide evidence either for or against the hypothesis that
phase referenced imaging gives better dynamic range than closure
phase imaging. Instead we wish to explore the potential of this
technique for future optical interferometry and also because image
reconstruction in the optical using phase referencing techniques has
only been performed with limited success. We have generated simulated,
noisy, complex visibility data, analogous to the signal produced in
radio interferometers, using the VLTI as a template. We proceeded with
image reconstruction using the radio image reconstruction algorithms
contained in aips imagr (clean algorithm). Our results show that
image reconstruction is successful in most of our science cases,
yielding images with a 4 milliarcsecond resolution in K band. We have
also investigated the number of target candidates for optical phase
referencing. Using the 2MASS point source catalog, we show that there
are several hundred objects with phase reference sources less than 30
arcseconds away, allowing to apply this technique.
Title: System overview of the VLTI Spectro-Imager
Authors: Jocou, L.; Berger, J. P.; Malbet, F.; Kern, P.; Beckmann, U.;
Lorenzetti, D.; Corcione, L.; Li Causi, G.; Buscher, D.; Young, J.;
Gai, M.; Weigelt, G.; Zins, G.; Duvert, G.; Perraut, K.; Labeye, P.;
Absil, O.; Garcia, P.; Loreggia, D.; Lima, J.; Rebordao, J.; Ligori,
S.; Amorim, A.; Rabou, P.; Le Bouquin, J. B.; Haniff, C.; Le Coarer,
E.; Feautrier, P.; Duchene, G.; Benisty, M.; Chelli, A.; Herwats,
E.; Delboulbé, A.
Bibcode: 2008SPIE.7013E..2YJ
Altcode: 2008arXiv0807.3403J; 2008SPIE.7013E..90J
The VLTI Spectro Imager project aims to perform imaging with a
temporal resolution of 1 night and with a maximum angular resolution
of 1 milliarcsecond, making best use of the Very Large Telescope
Interferometer capabilities. To fulfill the scientific goals (see Garcia
et. al.), the system requirements are: a) combining 4 to 6 beams;
b) working in spectral bands J, H and K; c) spectral resolution
from R= 100 to 12000; and d) internal fringe tracking on-axis,
or off-axis when associated to the PRIMA dual-beam facility. The
concept of VSI consists on 6 sub-systems: a common path distributing
the light between the fringe tracker and the scientific instrument,
the fringe tracker ensuring the co-phasing of the array, the scientific
instrument delivering the interferometric observables and a calibration
tool providing sources for internal alignment and interferometric
calibrations. The two remaining sub-systems are the control system
and the observation support software dedicated to the reduction of
the interferometric data. This paper presents the global concept of
VSI science path including the common path, the scientific instrument
and the calibration tool. The scientific combination using a set of
integrated optics multi-way beam combiners to provide high-stability
visibility and closure phase measurements are also described. Finally
we will address the performance budget of the global VSI instrument. The
fringe tracker and scientific spectrograph will be shortly described.
Title: Aperture-synthesis imaging with the mid-infrared instrument
MATISSE
Authors: Hofmann, Karl-Heinz; Heininger, Matthias; Jaffe, Walter;
Kraus, Stefan; Lopez, Bruno; Millour, Florentin; Schertl, Dieter;
Weigelt, Gerd; Wolf, Sebastian
Bibcode: 2008SPIE.7013E..3YH
Altcode: 2008SPIE.7013E.122H
MATISSE is the second-generation mid-IR interferometry instrument
proposed for ESO's Very Large Telescope Interferometer. MATISSE will
combine the beams of up to four UTs or ATs of the VLTI and will allow
aperture-synthesis imaging in the L, M, and N bands with a resolution
of a few milli-arcseconds. We report on detailed image reconstruction
experiments with simulated MATISSE interferograms. Using model images
as input for many of our simulations, we study the dependence of
the reconstructions on the brightness and size of the target, the uv
coverage, and several other parameters.
Title: VLTI-AMBER observations of Eta Carinae with the FINITO fringe
tracker and spectral resolution 12000
Authors: Weigelt, Gerd; Chesneau, Olivier; Driebe, Thomas; Foy,
Renaud; Fraix-Burnet, Didier; Groh, Jose H.; Hofmann, Karl-Heinz;
Kraus, Stefan; Malbet, Fabien; Marconi, Alessandro; Mathias, Philippe;
Millour, Florentin; Monin, Jean-Louis; Petrov, Romain G.; Rantakyrö,
Frederik; Richichi, Andrea; Schertl, Dieter; Schöller, Markus; Stee,
Philippe; Testi, Leonardo; Wittkowski, Markus
Bibcode: 2008SPIE.7013E..03W
Altcode: 2008SPIE.7013E...2W
We present interferometric near-infrared observations of the Luminous
Blue Variable (LBV) η Car using the Very Large Telescope Interferometer
(VLTI) and the AMBER instrument of the European Southern Observatory
(ESO). A high spatial resolution of 5 mas (~11.5 AU) and a high spectral
resolution R = λ/Δλ=1500 and 12000 were obtained. Some of the
data was recorded using the fringe tracker FINITO. The observations
were obtained in the wavelength range around both the He I 2.059
μm and the Brγ 2.166 μm emission lines. The AMBER interferograms
allow the investigation of the wavelength dependence of η Car's
visibility, wavelength-differential phase, and closure phase. If we fit
Hillier et al. model visibilities to the observations, we obtain 50%
encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 μm
continuum, the He I, and the Brγ emission lines, respectively. In
the continuum, an elongation along a position angle of 120° +/-
15° was derived from the visibilities. The VLTI observations support
theoretical models of anisotropic winds from fast-rotating, luminous
hot stars with enhanced high-velocity mass loss near the pole.
Title: 2008 imaging beauty contest
Authors: Cotton, William; Monnier, John; Baron, Fabien; Hofmann,
Karl-Heinz; Kraus, Stefan; Weigelt, Gerd; Rengaswamy, Sridharan;
Thiébaut, Eric; Lawson, Peter; Jaffe, Walter; Hummel, Christian;
Pauls, Tom; Schmitt, Henrique; Tuthill, Peter; Young, John
Bibcode: 2008SPIE.7013E..1NC
Altcode: 2008SPIE.7013E..48C
We present the results of the third Optical/IR Interferometry Imaging
Beauty Contest. A formal comparison is presented of the performance of
algorithms used for imaging data from optical/infrared long-baseline
interferometers. The contest consists of blind imaging of test data sets
derived from model sources and distributed in the OI-FITS format. The
test data consisted of datasets on two objects each "observed" in
J, H, and K bands. The majority of the entries produced accurate
reconstructions of the initial models. Each of the methods presented
is discussed.
Title: Infrared spectro-interferometry of YSOs
Authors: Kraus, Stefan; Hofmann, Karl-Heinz; Ohnaka, Keiichi;
Preibisch, Thomas; Weigelt, Gerd
Bibcode: 2008SPIE.7013E..0RK
Altcode: 2008SPIE.7013E..23K
The latest generation of infrared long-baseline interferometric
instruments combines high spatial resolution with spectroscopic
capabilities, enabling fascinating new studies of the AU-scale
circumstellar environment around young stellar objects. Here,
we present recent investigations, which we conducted using the
VLTI instruments AMBER and MIDI and which demonstrate these new
observational possibilities. In one study, we combine near- and
mid-infrared interferometry (H-/K-/N-band) to constrain the geometry
and radial temperature profile of the circumstellar accretion disk
around the Herbig Be star MWC147. Using detailed radiative transfer
modeling, we find strong evidence for the presence of an optically-thick
inner gaseous disk. In another investigation, we used AMBER's medium
spectral resolution mode (R = 1500) to study the spatial origin of
the hydrogen Brγ line for five Herbig Ae/Be stars, associating the
line emission with different physical mechanisms, such as disk winds
and magnetospheric accretion. Finally, we present AMBER H- and K-band
observations of the close binary star θ 1OrionisC and
illustrate the benefits of fitting wavelength-differential visibilities
and closure phases. Besides yielding a high observing efficiency,
this approach is also insensitive to calibration errors, induced,
for instance, by fast changing atmospheric conditions.
Title: The laser guide star program for the LBT
Authors: Rabien, S.; Ageorges, N.; Angel, R.; Brusa, G.; Brynnel, J.;
Busoni, L.; Davies, R.; Deysenroth, M.; Esposito, S.; Gässler, W.;
Genzel, R.; Green, R.; Haug, M.; Lloyd Hart, M.; Hölzl, G.; Masciadri,
E.; Pogge, R.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari,
P.; Schwab, C.; Stalcup, T., Jr.; Storm, J.; Strüder, L.; Thiel,
M.; Weigelt, G.; Ziegleder, J.
Bibcode: 2008SPIE.7015E..15R
Altcode: 2008SPIE.7015E..28R
Laser guide star adaptive optics and interferometry are currently
revolutionizing ground-based near-IR astronomy, as demonstrated at
various large telescopes. The Large Binocular Telescope from the
beginning included adaptive optics in the telescope design. With
the deformable secondary mirrors and a suite of instruments taking
advantage of the AO capabilities, the LBT will play an important role
in addressing major scientific questions. Extending from a natural
guide star based system, towards a laser guide stars will multiply
the number of targets that can be observed. In this paper we present
the laser guide star and wavefront sensor program as currently being
planned for the LBT. This program will provide a multi Rayleigh guide
star constellation for wide field ground layer correction taking
advantage of the multi object spectrograph and imager LUCIFER in a
first step. The already foreseen upgrade path will deliver an on axis
diffraction limited mode with LGS AO based on tomography or additional
sodium guide stars to even further enhance the scientific use of the
LBT including the interferometric capabilities.
Title: Mid-infrared view of cool evolved stars with the Very Large
Telescope Interferometer
Authors: Ohnaka, Keiichi; Driebe, Thomas; Hofmann, Karl-Heinz; Weigelt,
Gerd; Wittkowski, Markus
Bibcode: 2008SPIE.7013E..4MO
Altcode: 2008SPIE.7013E.145O
Two interferometric instruments at ESO's Very Large Telescope
Interferometer (VLTI) - MIDI and AMBER operating in the mid-infrared
(8-13 μm) and the near-infrared (JHK), respectively - have proven to
be very powerful to study the physical properties of the circumstellar
material around evolved stars. With the "spectro-interferometric"
capability of MIDI and AMBER, we can disentangle spectral and spatial
information on the observed object. VLTI observations have confirmed
our pictures on the circumstellar environment of cool evolved stars
in some cases but brought about entirely unexpected pictures in other
cases. Here, we present our recent results obtained with VLTI/MIDI.
Title: Spatially resolved dusty torus toward the red supergiant WOH
G64 in the Large Magellanic Cloud
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Weigelt, G.;
Wittkowski, M.
Bibcode: 2008A&A...484..371O
Altcode: 2008arXiv0803.3823O
Aims: We present N-band spectro-interferometric observations of the
red supergiant WOH G64 in the Large Magellanic
Cloud (LMC) using MIDI at the Very Large Telescope Interferometer
(VLTI). While the very high luminosity (∼ 5 × 105
L⊙) previously estimated for WOH G64 suggests that it
is a very massive star with an initial mass of ~40 M⊙,
its low effective temperature (~3200 K) is in serious disagreement
with the current stellar evolution theory.
Methods: WOH G64
was observed with VLTI/MIDI using the UT2-UT3 and UT3-UT4 baseline
configurations.
Results: The dust envelope around WOH G64 has
been spatially resolved with a baseline of ~60 m - the first MIDI
observations to resolve an individual stellar source in an extragalactic
system. The observed N-band visibilities show a slight decrease from
8 to ~10 μm and a gradual increase longward of ~10 μm, reflecting
the 10 μm silicate feature in self-absorption. This translates into a
steep increase of the uniform-disk diameter from 8 to 10 μm (from 18 to
26 mas) and a roughly constant diameter above 10 μm. The visibilities
measured at four position angles differing by ~60° but at approximately
the same baseline length (~60 m) do not show a noticeable difference,
suggesting that the object appears nearly centrosymmetric. The observed
N-band visibilities and spectral energy distribution can be reproduced
by an optically and geometrically thick silicate torus model viewed
close to pole-on. The luminosity of the central star is derived to be
∼ 2.8 × 105 L⊙, which is by a factor of 2
lower than the previous estimates based on spherical models. We also
identify the H2O absorption features at 2.7 and 6 μm in the spectra
obtained with the Infrared Space Observatory and the Spitzer Space
Telescope. The 2.7 μm feature originates in the photosphere and/or
the extended molecular layers, while the 6 μm feature is likely to
be of circumstellar origin.
Conclusions: The lower luminosity
newly derived from our MIDI observations and two-dimensional modeling
brings the location of WOH G64 on the H-R diagram in much better
agreement with theoretical evolutionary tracks for a 25 M⊙
star. However, the effective temperature is still somewhat too cool for
the theory. The low effective temperature of WOH G64 places it very
close to or even beyond the Hayashi limit, which implies that this
object may be experiencing unstable, violent mass loss. Based on
observations made with the Very Large Telescope Interferometer of the
European Southern Observatory. Program ID: 076.D-0253, 080.D-0222. This work is based [in part] on observations made with the Spitzer
Space Telescope, which is operated by the Jet Propulsion Laboratory,
California Institute of Technology under a contract with NASA.
Title: Establishing the AGN torus inner boundary with a first direct
access to the central engine in the near-IR
Authors: Kishimoto, Makoto; Barvainis, Richard; Antonucci, Robert;
Kotani, Takayuki; Honig, Sebastian; Beckert, Thomas; Weigelt, Gerd
Bibcode: 2008noao.prop..184K
Altcode:
Contrary to the expectation that near-IR long-baseline interferometry
can spatially resolve the innermost dusty torus in Type 1 AGN, the
only existing such measurement, with the Keck Interferometer (KI)
by Swain et al. (2003) for the brightest Seyfert 1 galaxy NGC 4151,
has indicated an unexpectedly compact size (radius <=0.5 mas or
0.04 pc; V^2=0.84+/-0.06 at K-band), much smaller than the nominal
dust sublimation radius. This has been interpreted as a dominance of
an unresolved accretion disk, implying non-existence of the putative
torus in this prototypical Type 1 nucleus. However, we recently pointed
out that the inner torus radii suggested by near-IR reverberations
are generally also much smaller, by a factor of 3, than the nominal
sublimation radius. Now with the significantly improved KI, we propose
to conduct an independent and conclusive size measurement by obtaining
K- band visibilities over a significant range of baselines. This will
restore the torus picture, with a much smaller radius than expected
from nominal ISM grains, and establish a significantly different
nature of the grains in the innermost AGN. Furthermore, with a new
H-band visibility measurement, we will be able to have a first direct
access to the unresolved accretion disk in the near-IR.
Title: High-Resolution Near-Infrared Speckle Interferometry and
Radiative Transfer Modeling of the OH/IR Star OH 104.9+2.4
Authors: Riechers, D.; Driebe, T.; Balega, Y. Y.; Hofmann, K. -H.;
Men'shchikov, A. B.; Weigelt, G.
Bibcode: 2008poii.conf..505R
Altcode: 2008poio.conf..505R
We present near-infrared speckle interferometry of the OH/IR star
OH 104.9+2.4 in the K' band obtained with the 6m telescope of the
Special Astrophysical Observatory (SAO) in Sep. 2002 and Oct. 2003. At
a wavelength of λ = 2.13 μ m the diffraction-limited resolution of 74
mas was attained. The reconstructed visibility reveals a spherically
symmetric, circumstellar dust shell (CDS) surrounding the central
star. The visibility function shows that the stellar contribution
to the total flux at λ = 2.13 μ m is less than 30% at all phases,
indicating a rather large optical depth of the CDS. The azimuthally
averaged 1-dimensional Gaussian visibility fit yields a diameter of
47 ± 3 mas (FHWM), which corresponds to 112 ± 13 AU for an adopted
distance of D = 2.38 ± 0.24 kpc.To determine the structure and the
roperties of the CDS of OH 104.9+2.4, radiative transfer calculations
using the code DUSTY cite{rie:ie95} were performed to simultaneously
model its visibility and the spectral energy distribution (SED). Since
OH 104.9+2.4 is highly variable, the observational data taken into
consideration for the modeling correspond to different phases of the
object's variability cycle. This offers the possibility to derive
several physical parameters of the central star and its CDS as a
function of phase
Title: Speckle Interferometry of Two Low-mass Triple Systems in the
Solar Neighbourhood
Authors: Malogolovets, E. V.; Balega, Y. Y.; Hofmann, K. -H.;
Rastegaev, D. A.; Weigelt, G.
Bibcode: 2008msah.conf..125M
Altcode:
No abstract at ADS
Title: VEGA: A Visible Spectrograph and Polarimeter for the VLTI
Authors: Mourard, D.; Antonelli, P.; Blazit, A.; Bonneau, D.; Bresson,
Y.; Clausse, J. M.; Domiciano, A.; Dugué, M.; Foy, R.; Harmanec, P.;
Heininger, M.; Hofmann, K. -H.; Jankov, S.; Koubsky, P.; Lagarde, S.;
Lebouquin, J. B.; Mathias, P.; Meilland, A.; Nardetto, N.; Petrov,
R.; Rousselet-Perraut, K.; Schertl, D.; Stee, Ph.; Tallon-Bosc, I.;
Tallon, M.; Thiébaut, E.; Vakili, F.; Weigelt, G.
Bibcode: 2008poii.conf..395M
Altcode: 2008poio.conf..395M
The ESO/VLTI has now clearly a position of world leader in the domain of
ground-based optical interferometry. With four 8.2 m telescopes and two
(four) 1.8 m telescopes, the Paranal Observatory is without any doubt
the best optical interferometric facility in the world. Since many
years, it has attracted the major part of the European interferometric
community and with the opening of MIDI and AMBER, the astronomers
have now access to 'general user' interferometric instruments in
the thermal and near infrared. This paper describes a project for a
second generation focal instrument of the VLTI, named VEGAfor Visible
spEctroGraph and polArimeter. The goal is to give access to the visible
wavelength region, with spectroscopic and polarimetric capabilities,
taking advantage of the coherent field of view of the VLTI. It is a
unique scientific field for the VLTI. For example, a 200m interferometer
operating in the visible will be able to resolve structures of the
order of 0.5 mas or 0.1 AU at the distance of the Ophiuchus cloud.
Title: Probing the Outer Atmosphere of Mira Variables and the Effects
of Chemical Composition on the Mid-Infrared Visibility
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Preibisch, Th.;
Schertl, D.; Weigelt, G.; Wittkowski, M.
Bibcode: 2008poii.conf..495O
Altcode: 2008poio.conf..495O
No abstract at ADS
Title: First AMBER/VLTI Observations of Hot Massive Stars
Authors: Petrov, R. G.; Millour, F.; Chesneau, O.; Weigelt, G.;
Bonneau, D.; Stee, Ph.; Kraus, S.; Mourard, D.; Meilland, A.; Vannier,
M.; Malbet, F.; Lisi, F.; Antonelli, P.; Kern, P.; Beckmann, U.;
Lagarde, S.; Perraut, K.; Gennari, S.; Le Coarer, E.; Driebe, Th.;
Accardo, M.; Robbe-Dubois, S.; Ohnaka, K.; Busoni, S.; Roussel, A.;
Zins, G.; Behrend, J.; Ferruzi, D.; Bresson, Y.; Duvert, G.; Nussbaum,
E.; Marconi, A.; Feautrier, Ph.; Dugué, M.; Chelli, A.; Tatulli,
E.; Heininger, M.; Delboulbe, A.; Bonhomme, S.; Schertl, D.; Testi,
L.; Mathias, Ph.; Monin, J. -L.; Gluck, L.; Hofmann, K. H.; Salinari,
P.; Puget, P.; Clausse, J. M.; Fraix-Burnet, D.; Foy, R.; Isella, A.
Bibcode: 2008poii.conf..153P
Altcode: 2005astro.ph..9208P; 2008poio.conf..153P
AMBER is the first near infrared focal instrument of the
VLTI. It combines three telescopes and produces spectrally resolved
interferometric measures. This paper discusses some preliminary results
of the first scientific observations of AMBER with three Unit Telescopes
at medium (1500) and high (12000) spectral resolution. We derive a
first set of constraints on the structure of the circumstellar material
around the Wolf Rayet γ2 Velorum and the LBV η Carinae.
Title: A methodology for studying physical and dynamical properties
of multiple stars. Application to the system of red dwarfs Gl 22
Authors: Docobo, J. A.; Tamazian, V. S.; Balega, Y. Y.; Andrade, M.;
Schertl, D.; Weigelt, G.; Campo, P.; Palacios, M.
Bibcode: 2008A&A...478..187D
Altcode:
Aims:The main aim of this study is the elaboration of a methodology
for studying physical and dynamical properties of multiple stars and
its application to the hierarchical triple system Gl 22. A careful
evaluation of the components' masses and a study of the system's overall
stability and long-term dynamical evolution were also pursued.
Methods: New NIR speckle interferometric observations with the
6 m telescope of the Special Astrophysical Observatory (Russia)
in the K' photometric band have been carried out. We have made use
of the method for orbit calculation reported by Docobo (1985).
Results: An original methodology was elaborated and applied to
evaluate the most probable elements of the outer orbit. Due to the
almost definitive orbit of the inner pair, which just covered a
full revolution, the motion of B relative to MCA has been
carefully calculated. The position of MCA was estimated on
the basis of differential photometry and empirical mass-luminosity
relationships. A weak sinusoidal pattern in the apparent motion of
the component B was noticed.
Conclusions: Our methodology was
successfully applied to the triple system Gl 22. The newly calculated
outer orbit exhibits a moderate eccentricity (e = 0.29), which
differs from the previously known circular solutions. Both orbits are
coplanar and co-revolving. This already known suggestion is now based
on a much larger set of observational data, including a significant
number of speckle measurements. Gl 22 is most likely a dynamically
stable system, at least on the time scale of 10 Myr. The sinusoidal
pattern in the motion of the B component could be caused by a fourth,
unseen, very low-mass object with a mass of 0.015~M⊙
(16 MJ) on a circular orbit around B with a period of ~15
yr and semimajor axis 0.35 arcsec.
Title: Interferometric Observations of the Mira Star o Ceti with
the VLTI/VINCI Instrument in the Near-Infrared
Authors: Driebe, T.; Woodruff, H. C.; Eberhardt, M.; Hofmann, K. -H.;
Ohnaka, K.; Richichi, A.; Schertl, D.; Schöller, M.; Scholz, M.;
Weigelt, G.; Wittkowski, M.; Wood, P. R.
Bibcode: 2008poii.conf..503D
Altcode: 2008poio.conf..503D
We present K-band commissioning observations of the Mira star prototype
o Cet obtained at the ESO Very Large Telescope Interferometer (VLTI)
with the VINCI instrument and two siderostats mounted to the VLTI
stations EO and GO, forming an unprojected baseline length of 16
m. Rosseland angular radii were derived from the measured visibilities
by fitting theoretical visibility functions obtained from center-to-limb
intensity variations (CLVs) of different Mira star models, and the phase
dependence of the visibility function and the apparent diameter have
been investigated. Comparison of the derived Rosseland radii, effective
temperatures, and the shape of the observed visibility functions with
model predictions suggests that o Cet is a fundamental mode pulsator.
Title: VLTI MIDI Observations of the Herbig Ae Star HR 5999
Authors: Preibisch, Thomas; Driebe, Thomas; Kraus, Stefan; Lachaume,
Regis; van Boekel, Roy; Weigelt, Gerd
Bibcode: 2008poii.conf..249P
Altcode: 2008poio.conf..249P
We have used long-baseline mid-infrared interferometric observations
with MIDI at the VLTI to resolve the circumstellar material around the
Herbig Ae star HR 5999 and to provide the first direct measurement of
its angular size. The obtained visibilities range between ~ 0.5 and
~ 0.9 at 10μm. This implies that the mid-infrared emission from HR
5999 is clearly resolved, but has a compact structure not much larger
than the resolution limit of the MIDI observations. The characteristic
size of the emission region depends on the position angles, and ranges
between 10 and 25 milli-arcseconds (corresponding to ~ 2-5 AU) for a
uniform-disk model, and 5-15 mas (~ 1-3 AU) for a Gauss model (FWHM). We
find a dependence of the characteristic size on the projected baseline
position angle, which suggests asymmetry of the emission region. To
derive constraints on the geometry of the dust distribution, we compare
our interferometric measurements to 2D, frequency-dependent radiation
transfer simulations of circumstellar disks.
Title: APerture Synthesis in the MID-Infrared with the VLTI
Authors: Lopez, B.; Wolf, S.; Duguée, M.; Graser, U.; Mathias, Ph.;
Antonelli, P.; Augereau, J. -C.; Behrend, J.; Berruyer, N.; Bresson,
Y.; Chesneau, O.; Connot, C.; Demyk, K.; Difolco, E.; Dutrey, A.;
Flament, S.; Gitton, Ph.; Glazenborg, A.; Glindemann, A.; Heininger,
M.; Henning, Th.; Hofmann, K. -H.; Hugues, Y.; Jaffe, W.; Jankov,
S.; Kraus, S.; Lagarde, S.; Leinert, Ch.; Linz, H.; Meisenheimer, K.;
Mosoni, L.; Menut, J. -L.; Neumann, U.; Niedzielski, A.; Przygodda,
F.; Puech, F.; Ratzka, T.; Rohloff, R.; Roussel, A.; Schertl, D.;
Schmider, F. -X.; Stecklum, B.; Thiéebaut, E.; Vakili, F.; Wagner,
K.; Weigelt, G.
Bibcode: 2008poii.conf..345L
Altcode: 2008poio.conf..345L
Our objective is to develop of the mid-infrared imaging for
the VLTI. Several areas of astrophysics will benefit of this new
capability. APreS-MIDI comprises a beam combiner which interfaces with
the current MIDI instrument. It thus constitutes an extension to the
two-beam interferometric instrument MIDI by increasing the number of
recombined beams up to four. This extension provides better uv-coverage
(6 visibility points measured in one set) and moreover will allow
measurement of 4 closure phase relations thus providing for the first
time aperture synthesis images in the mid-infrared spectral regime.
Title: High-Resolution Near-Infrared Speckle Interferometry and
Radiative Transfer Modeling of the OH/IR Star OH 26.5+0.6
Authors: Driebe, T.; Riechers, D.; Balega, Y. Y.; Hofmann, K. -H.;
Men'shchikov, A. B.; Weigelt, G.
Bibcode: 2008poii.conf..509D
Altcode: 2008poio.conf..509D
We present near-infrared speckle interferometry of the OH/IR star OH
26.5+0.6 in the K' band obtained with the 6m telescope of the Special
Astrophysical Observatory (SAO) in Oct. 2003. At a wavelength of λ =
2.13 μm the diffraction-limited resolution of 74 mas was attained. The
reconstructed visibility reveals a spherically symmetric, circumstellar
dust shell (CDS) surrounding the central star. In accordance with the
deep silicate absorption feature in the spectral energy distribution
(SED), the drop of the visibility function to a value of 0.36 at the
cutoff frequency indicates a rather large optical depth of the CDS. To
determine the structure and the properties of the CDS of OH 26.5+0.6,
radiative transfer calculations using the code DUSTY[3] were performed
to simultaneously model its visibility and the SED. Since OH 26.5+0.6
is highly variable, the observational data taken into consideration
for the modeling correspond to different phases of the object's
variability cycle. As in the case of another OH/IR star, OH 104.9+2.4
(see [5] and Riechers et al., this volume), we used these observational
constraints at different epochs to derive several physical parameters
of the central star and the CDS of OH 26.5+0.6 as a function of phase
Title: Eta Car through the Eyes of Interferometers
Authors: Chesneau, O.; van Boekel, R.; Herbst, T.; Kervella, P.; Min,
M.; Waters, L. B. F. M.; Leinert, Ch.; Petrov, R.; Weigelt, G.
Bibcode: 2008poii.conf..131C
Altcode: 2008poio.conf..131C
The core of the nebula surrounding Eta Carinae has recently been
observed with VLT/NACO, VLTI/VINCI, VLTI/MIDI and VLTI/AMBER in order
to spatially and spectrally constrain the warm dusty environment and
the central object. Narrow-band images at 3.74 μm and 4.05 μm reveal
the structured butterfly-shaped dusty environment close to the central
star with an unprecedented spatial resolution of about 60 mas. VINCI
has resolved the present-day stellar wind of Eta Carinae on a scale
of several stellar radii owing to the spatial resolution of the order
of 5 mas (~ 11 AU). The VINCI observations show that the object is
elongated with a de-projected axis ratio of approximately 1.5. Moreover
the major axis is aligned with that of the large bipolar nebula that
was ejected in the 19th century. Fringes have also been obtained in the
Mid-IR with MIDI using baselines of 75m. A peak of correlated flux of
100 Jy is detected 0.3" south-east from the photocenter of the nebula
at 8.7 μm is detected. This correlated flux is partly attributed to
the central object but it is worth noting that at these wavelengths,
virtually all the 0.5" x 0.5" central area can generate detectable
fringes witnessing the large clumping of the dusty ejecta. These
observations provide an upper limit for the SED of the central source
from 3.8 μm to 13.5 μm and constrain some parameters of the stellar
wind which can be compared to Hillier's model. Lastly, we present the
great potential of the AMBER instrument to study the numerous near-IR
emissive lines from the star and its close vicinity. In particular,
we discuss its ability to detect and follow the faint companion.
Title: Interferometric Orbits of New Hipparcos Binaries
Authors: Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.; Malogolovets,
E. V.; Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2008msah.conf..114B
Altcode:
First orbits are derived for 12 new Hipparcos binary systems based
on the precise speckle interferometric measurements of the relative
positions of the components. The orbital periods of the pairs
are between 5.9 and 29.0 yrs. Magnitude differences obtained from
differential speckle photometry allow us to estimate the absolute
magnitudes and spectral types of individual stars and to compare
their position on the mass-magnitude diagram with the theoretical
curves. The spectral types of the new orbiting pairs range from late
F to early M. Their mass-sums are determined with a relative accuracy
of 10-30%. The mass errors are completely defined by the errors of
Hipparcos parallaxes.
Title: Disentangling the Wind and the Disk in the Close Surrounding
of the Young Stellar Object MWC297 with AMBER/VLTI
Authors: Malbet, F.; Benisty, M.; De Wit, W. J.; Kraus, S.; Meilland,
A.; Millour, F.; Tatulli, E.; Berger, J. -P.; Chesneau, O.; Hofmann,
K. -H.; Isella, A.; Petrov, R.; Preibisch, T.; Stee, P.; Testi, L.;
Weigelt, G.
Bibcode: 2008poii.conf..255M
Altcode: 2005astro.ph..7226M; 2008poio.conf..255M
The young stellar object MWC297 is a B1.5Ve star exhibiting strong
hydrogen emission lines. This object has been observed by the AMBER/VLTI
instrument in 2-telescope mode in a sub-region of the K spectral band
centered around the Brγ line at 2.1656μm. The object has not only been
resolved in the continuum with a visibility of 0.50±0.10, but also in
the Brγ line, where the flux is about twice larger, with a visibility
about twice smaller (0.33±0.06). The continuum emission is consistent
with the expectation of an optically thick thermal emission from dust
in a circumstellar disk. The hydrogen emission can be understood by
the emission of a halo above the disk surface. It can be modelled
as a latitudinal-dependant wind model and it explains the width, the
strength and the visibibility through the emission lines. The AMBER
data associated with a high resolution ISAAC spectrum constrains the
apparent size of the wind but also its kinematics
Title: Temporal Variation of the Warm Molecular Layers around the
Mira Variable RR Sco Detected with the VLTI/MIDI Instrument
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Schertl, D.; Weigelt,
G.; Wittkowski, M.
Bibcode: 2008poii.conf..497O
Altcode: 2008poio.conf..497O
No abstract at ADS
Title: Mid-Infrared Long-Baseline Interferometry of the Symbiotic
Mira Star RX Pup with the VLTI/MIDI Instrument
Authors: Driebe, T.; Hofmann, K. -H.; Ohnaka, K.; Schertl, D.; Weigelt,
G.; Wittkowski, M.
Bibcode: 2008poii.conf..507D
Altcode: 2008poio.conf..507D
We present mid-infrared long-baseline interferometric observations of
the symbiotic Mira star RX Pup obtained with the VLTI/MIDI instrument
in prism mode within the framework of the Science Demonstration Time
(SDT) program in Feb. 2004. Four visibility measurements have been
carried out using the unit telescopes UT2 and UT3, with projected
baseline lengths ranging from 34.7 to 46.5 m.As we show by means of
radiative transfer modelin with the code DUSTY [3], the wavelength
dependence of the visibility and the N-band spectrum measured with
MIDI can be interpreted as thesignature of a circumstellar dust shell
which is dominated by silicate dust.
Title: N-Band Observation of the Silicate Carbon Star IRAS08002-3803
(Hen 38) with VLTI/MIDI
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Preibisch, Th.;
Schertl, D.; Weigelt, G.; Wittkowski, M.
Bibcode: 2008poii.conf..499O
Altcode: 2008poio.conf..499O
No abstract at ADS
Title: The Circumstellar Environment of Evolved Stars as seen by
VLTI/MIDI
Authors: Ohnaka, K.; Bergeat, J.; Driebe, T.; Graser, U.; Hofmann,
K. -H.; Köhler, R.; Leinert, Ch.; Lopez, B.; Malbet, F.; Morel, S.;
Paresce, F.; Perrin, G.; Preibisch, Th.; Richichi, A.; Schertl, D.;
Schöller, M.; Sol, H.; Weigelt, G.; Wittkowski, M.
Bibcode: 2008poii.conf..111O
Altcode: 2008poio.conf..111O
We present the results of the first mid-infrared interferometric
observations of the Mira variable RRSco with the VLTI/MIDI, together
with K-band observations using VLTI/VINCI.The uniform-disk diameter was
found to be 18mas between 8 and 10μm, while it gradually increases at
wavelengths longer than 10μm to reach 24mas at 13μm.These uniform-disk
diameters in the mid-infrared are significantly larger than the K-band
uniform-disk diameter of 10.2±0.5 mas measured using VLTI/VINCI,
three weeks after the MIDI observations. Our model calculations show
that optically thick emission from a warm molecular envelope consisting
of H2O and SiO can cause the apparent mid-infrared diameter
to be much larger than the continuum diameter, and this can explain the
mid-infrared angular sizes roughly twice as large as that measured in
the K band. The observed increase of the uniform-disk diameter longward
of 10μm can be explained by an optically thin dust shell consisting
of corundum and silicate grains.
Title: η Carinae 2009.0: One of the Most Remarkable Stars in the Sky
Authors: Sterken, Christiaan; van Genderen, Arnout; Weigelt, Gerd;
Kaufer, Andreas
Bibcode: 2007Msngr.130...32S
Altcode:
η Carinae is one of the most luminous and massive stars in the
Galaxy. The star underwent a major eruption in 1838, followed by a
second maximum a few decades later and a low-gradient brightening to the
present. The central source of η Car is a highly-eccentric binary with
a period of 5.54 years. The photometric and interferometric monitoring
programmes with ESO telescopes are summarised. On the occasion of the
forthcoming periastron passage in 2009.0, the star will be the target
of intensive photometric, spectroscopic and interferometric monitoring
from Chile and other southern observatories.
Title: Eta Carinae: Preparing for the Next Spectroscopic Event and
What We May Learn
Authors: Gull, Theodore R.; Corcoran, M.; Damineli, A.; Hillier, D.;
Owocki, S.; Madura, T.; Weigelt, G.; Groh, J.; Nielsen, K.; Vieira
Kober, G.; Weis, K.; Hartman, H.; Smith, N.; Hamaguchi, K.; Bautista,
M.; Carinae Bunch, Eta
Bibcode: 2007AAS...211.5103G
Altcode: 2007BAAS...39..815G
Eta Carinae, with its historical ejection events of the 19th century
and propinquity, provides an excellent test bed for understanding
how the most massive stars transition from hydrogen burning to the
presupernova stage. The next X-ray and visible/UV spectroscopic
event, associated with the binary periastron, is predicted to be January
11, 2009 +/- 2 days. Observations are being prepared and proposed
to test models of the binary system and response by the ejecta to
changes in the photo-excitation. This poster will describe current
and developing models and observations that are planned to test and
further enhance these models. We solicit additional observational
and modeling efforts. We acknowledge the resources of the many
observatories supporting this project.
Title: The innermost region of AGN tori: implications from the
HST/NICMOS type 1 point sources and near-IR reverberation
Authors: Kishimoto, M.; Hönig, S. F.; Beckert, T.; Weigelt, G.
Bibcode: 2007A&A...476..713K
Altcode: 2007arXiv0709.0431K
Spatially resolving the innermost region of the putative torus-like
structure in an active galactic nucleus (AGN) is one of the main goals
of high-spatial-resolution studies. This could be done in the near-IR
observations of type 1 AGNs where we directly see the hottest dust
grains in the torus. We discuss two critical issues in such studies. One
is the possible contribution from the central putative accretion disk
(the near-IR part of the big blue bump emission), which should be taken
into account for the torus measurements. The other is the expected size
of the inner boundary of the torus, essential for the feasibility of
spatially resolving the region. We examine the nuclear near-IR point
sources in the HST/NICMOS images of nearby type 1 AGNs to evaluate the
accretion disk contribution. After the subtraction of the host bulge
flux through two-dimensional decompositions, we show that near-IR colors
of the point sources appear quite interpretable simply as a composite of
a black-body-like spectrum and a relatively blue distinct component,
as expected for a torus and an accretion disk in the near-IR. The
near-IR colors of our radiative transfer models for clumpy tori also
support this simple two-component interpretation. The observed near-IR
colors for the available sample suggest a fractional accretion disk
contribution of ~25% or less at 2.2 μm. We also show that the innermost
torus radii as indicated by recent near-IR reverberation measurements
are systematically smaller by a factor of ~3 than the predicted dust
sublimation radius with a reasonable assumption for graphite grains
of a sublimation temperature 1500 K and size 0.05 μm in radius. The
discrepancy might indicate a much higher sublimation temperature or a
typical grain size much larger in the innermost tori, though the former
case appears to be disfavored by the observed colors of the HST point
sources studied above. Alternatively, the central engine radiation
might be significantly anisotropic. The near-IR interferometry with a
baseline of ~100 m should be able to provide important, independent
size measurements for the innermost torus region, based on the low
fractional contribution from the accretion disk obtained above.
Title: Speckle interferometry of nearby multiple
stars. IV. Measurements in 2004 and new orbits
Authors: Balega, I. I.; Balega, Yu. Yu.; Maksimov, A. F.; Malogolovets,
E. V.; Rastegaev, D. A.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2007AstBu..62..339B
Altcode: 2007arXiv0712.2573B
The results of speckle interferometric observations of 104 binary and
6 triple stars performed at the BTA 6 m telescope in 2004 October
are presented. Nearby low-mass stars are mostly observed for the
program, among which 59 there are new binaries recently discovered
by the Hipparcos astrometric satellite. Concurrently with the
diffraction-limited position measurements we obtained 154 brightness
ratio measurements of binary and multiple star components in different
bands of the visible spectrum. New, first-resolved binaries are the
symbiotic star CH Cyg with a weak companion at 0.043″ separation and
the pair of red dwarfs, GJ 913 = HIP 118212. In addition, we derived
the orbital parameters for two interferometric systems: the CN-giant
pair HD 210211 = HIP 109281 (P = 10.7 yr) and the G2V-K2V G2V-K2V
binary GJ 9830 = HIP 116259 (P = 15.7 yr).
Title: Mid-Infrared Long-Baseline Interferometry of the Symbiotic
Mira Star RX Pup with the VLTI/MIDI Instrument
Authors: Driebe, T.; Hofmann, K. -H.; Ohnaka, K.; Schertl, D.;
Weigelt, G.
Bibcode: 2007ASPC..378..291D
Altcode:
We present mid-infrared long-baseline interferometric observations of
the symbiotic Mira star RX Pup obtained with the VLTI/MIDI instrument
within the framework of the Science Demonstration Time (SDT) program
in February 2004. Four visibility measurements have been carried
out using the unit telescopes UT2 and UT3, with projected baseline
lengths ranging from 34.7 to 46.5 m. All visibility measurements show
a distinct wavelength dependence: a rather steep decrease between 8 and
10 μm, and a shallower monotonic increase longward of 10 μm. For the
corresponding uniform disk diameter, this visibility shape translates
into a diameter increase by a factor of 2 from 25 to 50 mas between 8
and 10 μm and an almost wavelength-independent diameter between 10
and 13 μm. As we show by means of radiative transfer modeling with
the code dusty, this wavelength dependence measured with VLTI/MIDI
can be interpreted as the mid-infrared signature of a circumstellar
dust shell which is dominated by silicate dust.
Title: High-Resolution Near-Infrared Speckle Interferometry and
Radiative Transfer Modeling of the OH/IR Star OH 26.5+0.6
Authors: Driebe, T.; Riechers, D.; Balega, Y. Y.; Hofmann, K. -H.;
Menshchikov, A. B.; Weigelt, G.
Bibcode: 2007ASPC..378..289D
Altcode:
We present near-infrared speckle interferometry of the OH/IR star
OH 26.5+0.6 in the K' band obtained with the 6-m telescope of the
Special Astrophysical Observatory (SAO) in October 2003. At λ = 2.12
μm the diffraction-limited resolution of 74 mas was attained. The
reconstructed visibility function shows that the stellar contribution to
the total flux at λ = 2.12 μm is less than 50%, indicating a rather
large optical depth of the circumstellar dust shell (CDS) surrounding
this highly reddened object, in accordance with the strong silicate
absorption feature seen in the spectral energy distribution (SED). Our
phase-dependent modeling approach follows a strategy similar to the
one recently applied successfully to interpret observations of the
OH/IR star OH 104.9+2.4 (Riechers et al. 2005). From our analysis,
we derived several physical parameters of the central star and the
CDS as a function of pulsation phase.
Title: Bispectrum Speckle Interferometry and Imaging Polarimetry of
the Carbon Star IRC+10216: the Dynamic Evolution of the Innermost
Circumstellar Environment from 1995 to 2005
Authors: Weigelt, G.; Balega, Y. Y.; Hofmann, K. -H.; Men'shchikov,
A.; Murakawa, K.; Schertl, D.
Bibcode: 2007ASPC..378..349W
Altcode:
We report on bispectrum speckle interferometry monitoring, radiative
transfer modeling, and imaging polarimetry of IRC+10216.
Title: VLTI/MIDI Observation of the Silicate Carbon Star IRAS
08002--3803: Dusty Environment Spatially Resolved for the First Time
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Preibisch, Th.;
Schertl, D.; Weigelt, G.; Wittkowski, M.
Bibcode: 2007ASPC..378..327O
Altcode:
We present the results of N--band high angular resolution observations
of the silicate carbon star IRAS 08002--3803 with the MID-infrared
Interferometric instrument (MIDI) at ESO's Very Large Telescope
Interferometer (VLTI). Our VLTI/MIDI observations of IRAS 08002--3803
have spatially resolved the dusty environment of a silicate carbon
star for the first time. However, neither spherical shell models nor
axisymmetric disk models consisting of silicate grains alone can
simultaneously explain the observed wavelength dependence of the
visibility and the spectral energy distribution (SED). We propose
that the circumstellar environment of IRAS 08002--3803 may consist
of two grain species coexisting in the disk: silicate and a second
grain species, for which we consider amorphous carbon, large silicate
grains, and metallic iron grains. Our MIDI observations and radiative
transfer calculations lend support to a picture in which oxygen-rich
material around IRAS 08002--3803 is stored in an optically thick
circumbinary disk surrounding the carbon-rich primary star and its
putative low-luminosity companion.
Title: Near-Infrared Speckle Imaging and AO Polarimetry of the
Bipolar Proto-Planetary Nebula Frosty Leo
Authors: Murakawa, K.; Ohnaka, K.; Driebe, T.; Hofmann, K. -H.;
Scherti, D.; Oya, S.; Weigelt, G.
Bibcode: 2007ASPC..378..321M
Altcode:
We present a K'--band speckle image and H,K--band polarimetric images
of the oxygen-rich proto-planetary nebula Frosty Leo. Our speckle image
reveals clumpy structures in the hourglass-like bipolar nebula. The
polarimetric data, for the first time, detected an elongated region with
small polarization. We have performed radiative transfer calculations
to investigate the physical properties of the Frosty Leo nebula. We
found that micron-size grains in the dense equatorial region and small
grains in the bipolar lobes are required to explain the total intensity
images, the polarization images, and the spectral energy distribution.
Title: Cool evolved stars as seen by the Very Large Telescope
Interferometer: Power of infrared spectro-interferometry
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Schertl, D.; Weigelt,
G.; Wittkowski, M.
Bibcode: 2007AIPC..948..449O
Altcode:
Two interferometric instruments at ESO's Very Large Telescope
Interferometer (VLTI), MIDI and AMBER which operate in the mid-infrared
(8-13 μm) and the near-infrared (JHK) respectively, have proven to
be powerful tools to probe the circumstellar environment of evolved
stars. Their spectro-interferometric capability enables us to observe
objects with spectral and spatial information disentangled. VLTI
observations confirm our pictures on the circumstellar environment of
cool evolved stars in some cases but bring about entirely unexpected
pictures for other cases. Here, we present particularly our recent
results obtained with VLTI/MIDI.
Title: 3D Radiative Transfer Modeling of Clumpy Dust Tori Around AGN
Authors: Hönig, S. F.; Beckert, T.; Ohnaka, K.; Weigelt, G.
Bibcode: 2007ASPC..373..487H
Altcode: 2006astro.ph.11946H
We present 3-dimensional radiative transfer models for clumpy dust tori
around AGN. Our method combines Monte Carlo simulations of individual
dust clouds with the actual 3-dimensional distribution of clouds in
the torus. The model has been applied to NIR and MIR photometric
and interferometric observations of NGC 1068. For the first time,
it is possible to simultaneously reproduce both photometric and
interferometric observations in the NIR and MIR. We infer a luminosity
L=2×1045 ergs/s and an inclination of i=70° for NGC 1068
from our model.
Title: AMBER/VLTI observations of η Carinae with high spatial
resolution and spectral resolutions of λ/Δ λ = 1500 and 12 000
Authors: Weigelt, G.; Driebe, T.; Hofmann, K. -H.; Kraus, S.; Petrov,
R.; Schertl, D.
Bibcode: 2007NewAR..51..724W
Altcode:
We present the first NIR interferometric observations of the
LBV η Carinae with high spectral resolution [Weigelt et al.,
2007. Near-infrared interferometry of η Carinae with spectral
resolutions of 1500 and 12000 using AMBER/VLTI. A&A 464, 87.]. Our
observations demonstrate the potential of AMBER/VLTI to unveil new
structures on the scales of milliarcseconds. The aim of this work is
to study the wavelength dependence of η Car's optically thick wind
region with a high spatial resolution of 5 mas (11 AU) and high spectral
resolution. The observations were carried out with three 8.2 m VLTI
Unit Telescopes. The raw data are interferograms obtained with spectral
resolutions of λ/Δ λ = 1500 (MR-K mode) and 12 000 (HR-K mode). The
observations were performed in the wavelength range around both the
HeI 2.059 μm and the Brγ 2.166 μm emission lines. The spectrally
dispersed AMBER interferograms allow us to investigate the wavelength
dependence of the visibility, differential phase, and closure phase of
η Car. If we fit [Hillier, D.J., Davidson, K., Ishibashi, K., Gull,
T., 2001. On the Nature of the Central Source in η Carinae. ApJ 553,
837] model visibilities (Hillier et al., 2001) to the observed AMBER
visibilities, we obtain 50% encircled-energy diameters of 4.3, 6.5,
and 9.6 mas in the 2.17 μm continuum, the HeI, and the Brγ emission
lines, respectively. We find good agreement between the measured
visibilities and the predictions of the radiative transfer model of
Hillier et al. (2001). Our observations support theoretical models of
anisotropic winds from fast-rotating, luminous hot stars with enhanced
high-velocity mass loss near the polar regions.
Title: In the intimacy of stars with AMBER at the VLTI
Authors: Malbet, F.; Petrov, R.; Weigelt, G.; Chesneau, O.; Domiciano
de Souza, A.; Meilland, A.; Millour, F.; Tatulli, E.; Amber Consortium
Bibcode: 2007sf2a.conf...13M
Altcode:
The AMBER instrument installed at the Very Large Telescope (VLT)
combines the beams from three telescopes to produce spectrally dispersed
interference fringes with milli-arcsecond angular scales in the near
infrared. Three years after installation, first scientific observations
have been carried out mostly during the Science Demonstration Time
and the Guaranteed Time. The first science has mainly focused on the
environment of various types of stars. Because AMBER has dramatically
increased the number of measures per baseline, this instrument brings
strong constraints on morphology and models.
Title: Resolving the B[e] star Hen 3-1191 at 10 μm with VLTI/MIDI
Authors: Lachaume, R.; Preibisch, Th.; Driebe, Th.; Weigelt, G.
Bibcode: 2007A&A...469..587L
Altcode: 2007astro.ph..3736L
We report spatially resolved, spectrally dispersed N-band observations
of the B[e] star Hen 3-1191 with the MIDI instrument of the Very Large
Telescope Interferometer. The object is resolved with a 40 m baseline
and has an equivalent uniform disc diameter ranging from 24 mas at 8
μm} to 36 mas at 13 {μm}. The MIDI spectrum and visibilities show a
curvature which can arise from a weak silicate feature in which the
object appears ≈15% larger than in the continuum, but this could
result from a change in the object's geometry within the band. We
then model Hen's 3-1191 spectral energy distribution (.4-60 μm)
and N-band visibilities. Because of the unknown nature of the object,
we use a wide variety of models for objects with IR excesses. We find
the observations to be consistent with a disc featuring an unusually
high mass accretion and a large central gap almost void of matter,
an excretion disc, and a binary made of two IR sources. We are unable
to find a circumstellar shell model consistent with the data. We
review the different hypotheses concerning the physical nature of the
star and conclude that it is neither a Be supergiant nor a symbiotic
star. However, we could not discriminate between the scenario of a
young stellar object featuring an unusually strong FU Orionis-like
outburst of mass accretion (4-250×10-4 M_⊙/{yr}) and
that of a protoplanetary nebula with an equatorial mass excretion rate
⪆4 × 10-5 M_⊙/yr. In both cases, taking the additional
presence of an envelope or wind into account would result in lower mass
flows. Based on observations made with the Very Large Telescope
Interferometer of the European Southern Observatory. Programme ID:
073.C-0757.
Title: GJ 900: A new hierarchical system with low-mass components
Authors: Malogolovets, E. V.; Balega, Yu. Yu.; Rastegaev, D. A.;
Hofmann, K. -H.; Weigelt, G.
Bibcode: 2007AstBu..62..117M
Altcode: 2007arXiv0707.2193M
Speckle interferometric observations made with the 6 m telescope
of the Special Astrophysical Observatory of the Russian Academy
of Sciences in 2000 revealed the triple nature of the nearby ( π
Hip = 51.80 ± 1.74 mas) low-mass young (≈ 200 Myr)
star GJ 900. The configuration of the triple system allowed it to
be dynamically unstable. Differential photometry performed from
2000 through 2004 yielded I- and K-band absolute magnitudes and
spectral types for the components to be I A =6.66±0.08,
I B =9.15±0.11, I C =10.08±0.26,
K A =4.84±0.08, K B =6.76±0.20, K
C =7.39±0.31, Sp A ≈K5-K7, Sp B
≈M3-M4, Sp C ≈M5-M6. The “mass-luminosity”
relation is used to estimate the individual masses of the components:
M A ≈0.64 M ⊙, M B ≈0.21
M ⊙, M C ≈0.13 M ⊙. From
the observations of the components’ relative motion in the period
2000 2006, we conclude that GJ 900 is a hierarchical triple star
with the possible orbital periods PA-BC≈80 yrs and
PBC≈20 yrs. An analysis of the 2MASS images of the region
around GJ 900 leads us to suggest that the system can include other
very-low-mass components.
Title: Visual/infrared interferometry of Orion Trapezium stars:
preliminary dynamical orbit and aperture synthesis imaging of the
θ1 Orionis C system
Authors: Kraus, S.; Balega, Y. Y.; Berger, J. -P.; Hofmann, K. -H.;
Millan-Gabet, R.; Monnier, J. D.; Ohnaka, K.; Pedretti, E.; Preibisch,
Th.; Schertl, D.; Schloerb, F. P.; Traub, W. A.; Weigelt, G.
Bibcode: 2007A&A...466..649K
Altcode: 2007astro.ph..2462K
Context: Located in the Orion Trapezium cluster, θ^1Ori C is one of
the youngest and nearest high-mass stars (O5-O7) known. Besides its
unique properties as a magnetic rotator, the system is also known to
be a close binary.
Aims: By tracing its orbital motion, we aim
to determine the orbit and dynamical mass of the system, yielding
a characterization of the individual components and, ultimately,
also new constraints for stellar evolution models in the high-mass
regime. Furthermore, a dynamical parallax can be derived from the orbit,
providing an independent estimate for the distance of the Trapezium
cluster.
Methods: Using new multi-epoch visual and near-infrared
bispectrum speckle interferometric observations obtained at the BTA
6 m telescope, and IOTA near-infrared long-baseline interferometry,
we traced the orbital motion of the θ^1Ori C components over
the interval 1997.8 to 2005.9, covering a significant arc of the
orbit. Besides fitting the relative position and the flux ratio, we
applied aperture synthesis techniques to our IOTA data to reconstruct a
model-independent image of the θ^1Ori C binary system.
Results:
The orbital solutions suggest a highly eccentricity (e≈0.91) and
short-period (P≈10.9 yrs) orbit. As the current astrometric data
only allows rather weak constraints on the total dynamical mass,
we present the two best-fit orbits. Of these two, the one implying
a system mass of 48 M⊙ and a distance of 434 pc to
the Trapezium cluster can be favored. When also taking the measured
flux ratio and the derived location in the HR-diagram into account,
we find good agreement for all observables, assuming a spectral
type of O5.5 for θ^1Ori C1 (M = 34.0 M⊙, T_eff = 39
900 K) and O9.5 for C2 (M = 15.5 M⊙, T_eff = 31 900
K). Using IOTA, we also obtained first interferometric observations
on θ^1Ori D, finding some evidence for a resolved structure, maybe
by a faint, close companion.
Conclusions: We find indications
that the companion C2 is massive itself, which makes it likely that
its contribution to the intense UV radiation field of the Trapezium
cluster is non-negligible. Furthermore, the high eccentricity of the
preliminary orbit solution predicts a very small physical separation
during periastron passage (∼1.5 AU, next passage around 2007.5),
suggesting strong wind-wind interaction between the two O stars.
Title: Temporal variations of the outer atmosphere and the dust shell
of the carbon-rich Mira variable V Ophiuchi probed with VLTI/MIDI
Authors: Ohnaka, K.; Driebe, T.; Weigelt, G.; Wittkowski, M.
Bibcode: 2007A&A...466.1099O
Altcode: 2007astro.ph..2226O
Aims:We present the first multi-epoch N-band spectro-interferometric
observations of the carbon-rich Mira variable V Oph
using MIDI at the ESO's Very Large Telescope Interferometer. Our
aim is to study temporal variations of physical properties of
the outer atmosphere and the circumstellar dust shell based on
spectrally-dispersed N-band visibilities over the C2H2 (+HCN)
features and the dust emission.
Methods: Our MIDI observations
were carried out at three different phases 0.18, 0.49, and 0.65,
with three different baselines (projected baseline lengths of 42-124
m) using four 8.2 m Unit Telescopes (UT2-UT4, UT1-UT4, and UT2-UT3
baseline configurations).
Results: The wavelength dependence of
the uniform-disk diameters obtained at all epochs is characterized
by a roughly constant region between 8 and 10 μm with a slight dip
centered at 9.5 μm and a gradual increase longward of 10 μm. These
N-band angular sizes are significantly larger than the estimated
photospheric size of V Oph. The angular sizes observed at different
epochs reveal that the object appears smaller at phase 0.49 (minimum
light) with uniform-disk diameters of 5-12 mas than at phases 0.18
( 12-20 mas) and 0.65 ( 9-15 mas). We interpret these results with
a model consisting of optically thick C2H2 layers and an optically
thin dust shell. Our modeling suggests that the C2H2 layers around
V Oph are more extended ( 1.7-1.8 Rstar) at phases 0.18
and 0.65 than at phase 0.49 ( 1.4 Rstar) and that the
C2H2 column densities appear to be the smallest at phase 0.49. We
also find that the dust shell consists of amorphous carbon and SiC
with an inner radius of 2.5 Rstar, and the total optical
depths of τV ≈ 0.6-0.9 (τ11.3 μm ≈
0.003 and 0.004 for amorphous carbon and SiC, respectively) found at
phases 0.18 and 0.65 are higher than the value obtained at phase 0.49,
τV ≈ 0.3 (τ11.3 μm ≈ 0.001 and 0.002 for
amorphous carbon and SiC, respectively).
Conclusions: Our MIDI
observations and modeling indicate that carbon-rich Miras also have
extended layers of polyatomic molecules as previously confirmed in
oxygen-rich Miras. The temporal variation of the N-band angular size is
largely governed by the variations of the opacity and the geometrical
extension of the C2H2 layers and the dust shell, and consequently,
this masks the size variation of the photosphere. Also, the observed
weakness of the mid-infrared C2H2 absorption in carbon-rich Miras
can be explained by the emission from the extended C2H2 layers and
the dust shell. Based on observations made with the Very Large
Telescope Interferometer of the European Southern Observatory. Program
ID: 075.D-0607. Table 4 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/466/1099
Title: First AMBER/VLTI Science
Authors: Malbet, F.; Petrov, R.; Weigelt, G.; Chesneau, O.; Domiciano
de Souza, A.; Meilland, A.; Millour, F.; Tatulli, E.; Amber Consortium
Bibcode: 2007Msngr.127...37M
Altcode:
Three years after the installation of AMBER, the first scientific
observations have been carried out mostly during Science Demonstration
Time and Guaranteed Time. The first science has mainly focused on the
environment of various types of stars. Observations described are:
the discs and wind in the young star MWC297; the rotating gas envelope
around the hot active star CPD-57 2874; mass loss from the massive star
Eta Carinae; the colliding wind WR and O star binary gamma2 Velorum;
the outburst of the recurrent nova RS Oph.
Title: AMBER, the near-infrared spectro-interferometric
three-telescope VLTI instrument
Authors: Petrov, R. G.; Malbet, F.; Weigelt, G.; Antonelli, P.;
Beckmann, U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.;
Gennari, S.; Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi,
F.; Millour, F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois,
S.; Roussel, A.; Salinari, P.; Tatulli, E.; Zins, G.; Accardo, M.;
Acke, B.; Agabi, K.; Altariba, E.; Arezki, B.; Aristidi, E.; Baffa,
C.; Behrend, J.; Blöcker, T.; Bonhomme, S.; Busoni, S.; Cassaing,
F.; Clausse, J. -M.; Colin, J.; Connot, C.; Delboulbé, A.; Domiciano
de Souza, A.; Driebe, T.; Feautrier, P.; Ferruzzi, D.; Forveille,
T.; Fossat, E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.;
Gil, C.; Glentzlin, A.; Heiden, M.; Heininger, M.; Hernandez Utrera,
O.; Hofmann, K. -H.; Kamm, D.; Kiekebusch, M.; Kraus, S.; Le Contel,
D.; Le Contel, J. -M.; Lesourd, T.; Lopez, B.; Lopez, M.; Magnard,
Y.; Marconi, A.; Mars, G.; Martinot-Lagarde, G.; Mathias, P.; Mège,
P.; Monin, J. -L.; Mouillet, D.; Mourard, D.; Nussbaum, E.; Ohnaka,
K.; Pacheco, J.; Perrier, C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.;
Richichi, A.; Robini, A.; Sacchettini, M.; Schertl, D.; Schöller,
M.; Solscheid, W.; Spang, A.; Stee, P.; Stefanini, P.; Tallon, M.;
Tallon-Bosc, I.; Tasso, D.; Testi, L.; Vakili, F.; von der Lühe,
O.; Valtier, J. -C.; Vannier, M.; Ventura, N.
Bibcode: 2007A&A...464....1P
Altcode:
Context: Optical long-baseline interferometry is moving a crucial
step forward with the advent of general-user scientific instruments
that equip large aperture and hectometric baseline facilities,
such as the Very Large Telescope Interferometer (VLTI).
Aims:
AMBER is one of the VLTI instruments that combines up to three beams
with low, moderate and high spectral resolutions in order to provide
milli-arcsecond spatial resolution for compact astrophysical sources
in the near-infrared wavelength domain. Its main specifications are
based on three key programs on young stellar objects, active galactic
nuclei central regions, masses, and spectra of hot extra-solar
planets.
Methods: These key science goals led to scientific
specifications, which were used to propose and then validate the
instrument concept. AMBER uses single-mode fibers to filter the entrance
signal and to reach highly accurate, multiaxial three-beam combination,
yielding three baselines and a closure phase, three spectral dispersive
elements, and specific self-calibration procedures.
Results: The
AMBER measurements yield spectrally dispersed calibrated visibilities,
color-differential complex visibilities, and a closure phase allows
astronomers to contemplate rudimentary imaging and highly accurate
visibility and phase differential measurements. AMBER was installed
in 2004 at the Paranal Observatory. We describe here the present
implementation of the instrument in the configuration with which the
astronomical community can access it.
Conclusions: .After two
years of commissioning tests and preliminary observations, AMBER has
produced its first refereed publications, allowing assessment of its
scientific potential.
Title: An asymmetry detected in the disk of κ Canis
Majoris with AMBER/VLTI
Authors: Meilland, A.; Millour, F.; Stee, P.; Domiciano de Souza, A.;
Petrov, R. G.; Mourard, D.; Jankov, S.; Robbe-Dubois, S.; Spang, A.;
Aristidi, E.; Antonelli, P.; Beckmann, U.; Bresson, Y.; Chelli, A.;
Dugué, M.; Duvert, G.; Gennari, S.; Glück, L.; Kern, P.; Lagarde,
S.; Le Coarer, E.; Lisi, F.; Malbet, F.; Perraut, K.; Puget, P.;
Rantakyrö, F.; Roussel, A.; Tatulli, E.; Weigelt, G.; Zins, G.;
Accardo, M.; Acke, B.; Agabi, K.; Altariba, E.; Arezki, B.; Baffa,
C.; Behrend, J.; Blöcker, T.; Bonhomme, S.; Busoni, S.; Cassaing,
F.; Clausse, J. -M.; Colin, J.; Connot, C.; Delboulbé, A.; Driebe,
T.; Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat, E.; Foy,
R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin,
A.; Heiden, M.; Heininger, M.; Hernandez Utrera, O.; Hofmann, K. -H.;
Kamm, D.; Kiekebusch, M.; Kraus, S.; Le Contel, D.; Le Contel, J. -M.;
Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars, G.;
Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin, J. -L.; Mouillet,
D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier, C.; Rabbia, Y.;
Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.; Sacchettini, M.;
Schertl, D.; Schöller, M.; Solscheid, W.; Stefanini, P.; Tallon,
M.; Tallon-Bosc, I.; Tasso, D.; Testi, L.; Vakili, F.; von der Lühe,
O.; Valtier, J. -C.; Vannier, M.; Ventura, N.
Bibcode: 2007A&A...464...73M
Altcode: 2006astro.ph.11563M
Aims:We study the geometry and kinematics of the circumstellar
environment of the Be star κ CMa in the Brγ emission line and its
nearby continuum.
Methods: We use the AMBER/VLTI instrument
operating in the K band, which provides a spatial resolution of about 6
mas with a spectral resolution of 1500, to study the kinematics within
the disk and to infer its rotation law. To obtain more kinematical
constraints we also use a high spectral resolution Paβ line profile
obtain in December 2005 at the Observatorio do Pico do Dios, Brazil and
we compile V/R line profile variations and spectral energy distribution
data points from the literature.
Results: Using differential
visibilities and differential phases across the Brγ line we detect an
asymmetry in the disk. Moreover, we found that κ CMa seems difficult to
fit within the classical scenario for Be stars, illustrated recently
by α Arae observations, i.e. a fast rotating B star close to its
breakup velocity surrounded by a Keplerian circumstellar disk with
an enhanced polar wind. We discuss the possibility that κ CMa is a
critical rotator with a Keplerian rotating disk and examine whether if
the detected asymmetry can be interpreted within the “one-armed”
viscous disk framework. Based on observations collected at the
European Southern Observatory, Paranal, Chile, within the guaranteed
time programme 074.A-9025(A).
Title: Constraining the wind launching region in Herbig Ae stars:
AMBER/VLTI spectroscopy of HD 104237
Authors: Tatulli, E.; Isella, A.; Natta, A.; Testi, L.; Marconi, A.;
Malbet, F.; Stee, P.; Petrov, R. G.; Millour, F.; Chelli, A.; Duvert,
G.; Antonelli, P.; Beckmann, U.; Bresson, Y.; Dugué, M.; Gennari, S.;
Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut,
K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; Weigelt,
G.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba, E.; Arezki,
B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker, T.; Bonhomme,
S.; Busoni, S.; Cassaing, F.; Clausse, J. -M.; Colin, J.; Connot,
C.; Delboulbé, A.; Domiciano de Souza, A.; Driebe, T.; Feautrier,
P.; Ferruzzi, D.; Forveille, T.; Fossat, E.; Foy, R.; Fraix-Burnet,
D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin, A.; Heiden, M.;
Heininger, M.; Hernandez Utrera, O.; Hofmann, K. -H.; Kamm, D.;
Kiekebusch, M.; Kraus, S.; Le Contel, D.; Le Contel, J. -M.; Lesourd,
T.; Lopez, B.; Lopez, M.; Magnard, Y.; Mars, G.; Martinot-Lagarde,
G.; Mathias, P.; Mège, P.; Monin, J. -L.; Mouillet, D.; Mourard,
D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier, C.; Rabbia, Y.;
Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.; Sacchettini, M.;
Schertl, D.; Schöller, M.; Solscheid, W.; Spang, A.; Stefanini, P.;
Tallon, M.; Tallon-Bosc, I.; Tasso, D.; Vakili, F.; von der Lühe,
O.; Valtier, J. -C.; Vannier, M.; Ventura, N.
Bibcode: 2007A&A...464...55T
Altcode: 2006astro.ph..6684T
Aims:We investigate the origin of the Brγ emission of the Herbig
Ae star HD 104237 on Astronomical Unit (AU) scales.
Methods:
Using AMBER/VLTI at a spectral resolution R=1500 we spatially resolve
the emission in both the Brγ line and the adjacent continuum.
Results: The visibility does not vary between the continuum and the
Brγ line, even though the line is strongly detected in the spectrum,
with a peak intensity 35% above the continuum. This demonstrates that
the line and continuum emission have similar size scales. We assume that
the K-band continuum excess originates in a “puffed-up” inner rim
of the circumstellar disk, and discuss the likely origin of Brγ.
Conclusions: .We conclude that this emission most likely arises from
a compact disk wind, launched from a region 0.2-0.5 AU from the star,
with a spatial extent similar to that of the near infrared continuum
emission region, i.e., very close to the inner rim location. Based
on observations collected at the European Southern Observatory, Paranal,
Chile, within the guaranteed time programme 074.A-9025(A).
Title: Disk and wind interaction in the young stellar object
MWC 297 spatially resolved with AMBER/VLTI
Authors: Malbet, F.; Benisty, M.; de Wit, W. -J.; Kraus, S.; Meilland,
A.; Millour, F.; Tatulli, E.; Berger, J. -P.; Chesneau, O.; Hofmann,
K. -H.; Isella, A.; Natta, A.; Petrov, R. G.; Preibisch, T.; Stee,
P.; Testi, L.; Weigelt, G.; Antonelli, P.; Beckmann, U.; Bresson, Y.;
Chelli, A.; Dugué, M.; Duvert, G.; Gennari, S.; Glück, L.; Kern,
P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut, K.; Puget, P.;
Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; Zins, G.; Accardo,
M.; Acke, B.; Agabi, K.; Altariba, E.; Arezki, B.; Aristidi, E.;
Baffa, C.; Behrend, J.; Blöcker, T.; Bonhomme, S.; Busoni, S.;
Cassaing, F.; Clausse, J. -M.; Colin, J.; Connot, C.; Delboulbé,
A.; Domiciano de Souza, A.; Driebe, T.; Feautrier, P.; Ferruzzi, D.;
Forveille, T.; Fossat, E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.;
Giani, E.; Gil, C.; Glentzlin, A.; Heiden, M.; Heininger, M.; Hernandez
Utrera, O.; Kamm, D.; Kiekebusch, M.; Le Contel, D.; Le Contel, J. -M.;
Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars, G.;
Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin, J. -L.; Mouillet,
D.; Mourard, D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier,
C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.;
Sacchettini, M.; Schertl, D.; Schöller, M.; Solscheid, W.; Spang,
A.; Stefanini, P.; Tallon, M.; Tallon-Bosc, I.; Tasso, D.; Vakili,
F.; von der Lühe, O.; Valtier, J. -C.; Vannier, M.; Ventura, N.
Bibcode: 2007A&A...464...43M
Altcode: 2005astro.ph.10350M
The young stellar object MWC 297 is an embedded
B1.5Ve star exhibiting strong hydrogen emission lines and a strong
near-infrared continuum excess. This object has been observed with
the VLT interferometer equipped with the AMBER instrument during
its first commissioning run. AMBER/VLTI is currently the only
near infrared interferometer that can observe spectrally dispersed
visibilities. MWC 297 has been spatially resolved in
the continuum with a visibility of 0.50+0.08-0.10
as well as in the Brγ emission line where the visibility decreases
to 0.33±0.06. This change in the visibility with wavelength can be
interpreted by the presence of an optically thick disk responsible for
the visibility in the continuum and of a stellar wind traced by the
Brγ emission line and whose apparent size is 40% larger. We validate
this interpretation by building a model of the stellar environment
that combines a geometrically thin, optically thick accretion disk
model consisting of gas and dust, and a latitude-dependent stellar
wind outflowing above the disk surface. The continuum emission and
visibilities obtained from this model are fully consistent with the
interferometric AMBER data. They agree also with existing optical,
near-infrared spectra and other broad-band near-infrared interferometric
visibilities. We also reproduce the shape of the visibilities in the
Brγ line as well as the profile of this line obtained at an higher
spectral resolution with the VLT/ISAAC spectrograph, and those of
the Hα and Hβ lines. The disk and wind models yield a consistent
inclination of the system of approximately 20°. A picture emerges in
which MWC 297 is surrounded by an equatorial flat
disk that is possibly still accreting and an outflowing wind that has
a much higher velocity in the polar region than at the equator. The
AMBER/VLTI unique capability of measuring spectral visibilities
therefore allows us for the first time to compare the apparent geometry
of a wind with the disk structure in a young stellar system. Based
on observations collected at the European Southern Observatory, Paranal,
Chile, within the commissioning programme 60.A-9054(A).
Title: Near-infrared interferometry of η Carinae
with spectral resolutions of 1 500 and 12 000 using AMBER/VLTI
Authors: Weigelt, G.; Kraus, S.; Driebe, T.; Petrov, R. G.; Hofmann,
K. -H.; Millour, F.; Chesneau, O.; Schertl, D.; Malbet, F.; Hillier,
J. D.; Gull, T.; Davidson, K.; Domiciano de Souza, A.; Antonelli,
P.; Beckmann, U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.;
Gennari, S.; Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi,
F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel,
A.; Tatulli, E.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba,
E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker, T.;
Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse, J. -M.; Colin, J.;
Connot, C.; Delboulbé, A.; Feautrier, P.; Ferruzzi, D.; Forveille,
T.; Fossat, E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.;
Gil, C.; Glentzlin, A.; Heiden, M.; Heininger, M.; Hernandez Utrera,
O.; Kamm, D.; Kiekebusch, M.; Le Contel, D.; Le Contel, J. -M.;
Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars,
G.; Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin, J. -L.;
Mouillet, D.; Mourard, D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.;
Perrier, C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.; Richichi, A.;
Robini, A.; Sacchettini, M.; Schöller, M.; Solscheid, W.; Spang,
A.; Stee, P.; Stefanini, P.; Tallon, M.; Tallon-Bosc, I.; Tasso, D.;
Testi, L.; Vakili, F.; von der Lühe, O.; Valtier, J. -C.; Vannier,
M.; Ventura, N.; Weis, K.; Wittkowski, M.
Bibcode: 2007A&A...464...87W
Altcode: 2006astro.ph..9715W
Aims: We present the first NIR spectro-interferometry of the LBV
η Carinae. The observations were performed with
the AMBER instrument of the ESO Very Large Telescope Interferometer
(VLTI) using baselines from 42 to 89 m. The aim of this work is to
study the wavelength dependence of η Car's optically thick wind
region with a high spatial resolution of 5 mas (11 AU) and high
spectral resolution.
Methods: The observations were carried
out with three 8.2 m Unit Telescopes in the K-band. The raw data are
spectrally dispersed interferograms obtained with spectral resolutions
of 1500 (MR-K mode) and 12 000 (HR-K mode). The MR-K observations
were performed in the wavelength range around both the He I 2.059 μm
and the Brγ 2.166 μm emission lines, the HR-K observations only in
the Brγ line region.
Results: The spectrally dispersed AMBER
interferograms allow the investigation of the wavelength dependence of
the visibility, differential phase, and closure phase of η Car. In
the K-band continuum, a diameter of 4.0±0.2 mas (Gaussian FWHM, fit
range 28-89 m baseline length) was measured for η Car's optically
thick wind region. If we fit Hillier et al. (2001, ApJ, 553, 837)
model visibilities to the observed AMBER visibilities, we obtain 50%
encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 μm
continuum, the He I, and the Brγ emission lines, respectively. In
the continuum near the Brγ line, an elongation along a position
angle of 120°±15° was found, consistent with previous VINCI/VLTI
measurements by van Boekel et al. (2003, A&A, 410, L37). We compare
the measured visibilities with predictions of the radiative transfer
model of Hillier et al. (2001), finding good agreement. Furthermore, we
discuss the detectability of the hypothetical hot binary companion. For
the interpretation of the non-zero differential and closure phases
measured within the Brγ line, we present a simple geometric model of
an inclined, latitude-dependent wind zone. Our observations support
theoretical models of anisotropic winds from fast-rotating, luminous hot
stars with enhanced high-velocity mass loss near the polar regions. Based on observations collected at the European Southern Observatory,
Paranal, Chile, within the AMBER guaranteed time programme 074.A-9025
and the VLTI science demonstration programme 074.A-9024.
Title: Interferometric data reduction with AMBER/VLTI. Principle,
estimators, and illustration
Authors: Tatulli, E.; Millour, F.; Chelli, A.; Duvert, G.; Acke, B.;
Hernandez Utrera, O.; Hofmann, K. -H.; Kraus, S.; Malbet, F.; Mège,
P.; Petrov, R. G.; Vannier, M.; Zins, G.; Antonelli, P.; Beckmann, U.;
Bresson, Y.; Dugué, M.; Gennari, S.; Glück, L.; Kern, P.; Lagarde,
S.; Le Coarer, E.; Lisi, F.; Perraut, K.; Puget, P.; Rantakyrö,
F.; Robbe-Dubois, S.; Roussel, A.; Weigelt, G.; Accardo, M.; Agabi,
K.; Altariba, E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend,
J.; Blöcker, T.; Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse,
J. -M.; Colin, J.; Connot, C.; Delboulbé, A.; Domiciano de Souza,
A.; Driebe, T.; Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat,
E.; Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.;
Glentzlin, A.; Heiden, M.; Heininger, M.; Kamm, D.; Kiekebusch, M.;
Le Contel, D.; Le Contel, J. -M.; Lesourd, T.; Lopez, B.; Lopez, M.;
Magnard, Y.; Marconi, A.; Mars, G.; Martinot-Lagarde, G.; Mathias,
P.; Monin, J. -L.; Mouillet, D.; Mourard, D.; Nussbaum, E.; Ohnaka,
K.; Pacheco, J.; Perrier, C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.;
Richichi, A.; Robini, A.; Sacchettini, M.; Schertl, D.; Schöller,
M.; Solscheid, W.; Spang, A.; Stee, P.; Stefanini, P.; Tallon, M.;
Tallon-Bosc, I.; Tasso, D.; Testi, L.; Vakili, F.; von der Lühe,
O.; Valtier, J. -C.; Ventura, N.
Bibcode: 2007A&A...464...29T
Altcode: 2006astro.ph..3046T
Aims:In this paper, we present an innovative data reduction method
for single-mode interferometry. It has been specifically developed
for the AMBER instrument, the three-beam combiner of the Very Large
Telescope Interferometer, but it can be derived for any single-mode
interferometer.
Methods: The algorithm is based on a direct
modelling of the fringes in the detector plane. As such, it requires
a preliminary calibration of the instrument in order to obtain the
calibration matrix that builds the linear relationship between the
interferogram and the interferometric observable, which is the complex
visibility. Once the calibration procedure has been performed, the
signal processing appears to be a classical least-square determination
of a linear inverse problem. From the estimated complex visibility,
we derive the squared visibility, the closure phase, and the spectral
differential phase.
Results: The data reduction procedures have
been gathered into the so-called amdlib software, now available for
the community, and are presented in this paper. Furthermore, each
step in this original algorithm is illustrated and discussed from
various on-sky observations conducted with the VLTI, with a focus on
the control of the data quality and the effective execution of the data
reduction procedures. We point out the present limited performances of
the instrument due to VLTI instrumental vibrations which are difficult
to calibrate. Based on observations collected at the European
Southern Observatory, Paranal, Chile.
Title: AMBER/VLTI and MIDI/VLTI spectro-interferometric observations
of the B[e] supergiant CPD-57°2874. Size and
geometry of the circumstellar envelope in the near- and mid-IR
Authors: Domiciano de Souza, A.; Driebe, T.; Chesneau, O.; Hofmann,
K. -H.; Kraus, S.; Miroshnichenko, A. S.; Ohnaka, K.; Petrov,
R. G.; Preisbisch, T.; Stee, P.; Weigelt, G.; Lisi, F.; Malbet, F.;
Richichi, A.
Bibcode: 2007A&A...464...81D
Altcode: 2005astro.ph.10735D
We present the first high spatial and spectral resolution
observations of the circumstellar envelope (CSE) of a B[e] supergiant
(CPD-57°2874), performed with the Very Large Telescope Interferometer
(VLTI). Spectra, visibilities and closure phase were obtained using
the beam-combiner instruments AMBER (near-IR interferometry with
three 8.3 m Unit Telescopes or UTs) and MIDI (mid-IR interferometry
with two UTs). The interferometric observations of the CSE are well
fitted by an elliptical Gaussian model with FWHM diameters varying
linearly with wavelength. Typical diameters measured are ≃1.8×3.4
mas or ≃4.5×8.5 AU (adopting a distance of 2.5 kpc) at 2.2 μm,
and ≃12×15 mas or ≃30×38 AU at 12 μm. The size of the region
emitting the Brγ flux is ≃2.8×5.2 mas or ≃7.0×13.0 AU. The
major-axis position angle of the elongated CSE in the mid-IR (≃144°)
agrees well with previous polarimetric data, hinting that the hot-dust
emission originates in a disk-like structure. In addition to the
interferometric observations we also present new optical (UBVR_cI_c) and
near-IR (JHKL) broadband photometric observations of CPD-57°2874. Our
spectro-interferometric VLTI observations and data analysis support
the non-spherical CSE paradigm for B[e] supergiants. Based on
observations collected at the European Southern Observatory, Paranal,
Chile, within the AMBER science demonstration time programme 074.A-9026
and the MIDI open time programme 074.D-0101.
Title: Accurate masses of low mass stars GJ 765.2AB (0.83
M⊙ + 0.76 M⊙)
Authors: Balega, Y. Y.; Beuzit, J. -L.; Delfosse, X.; Forveille, T.;
Perrier, C.; Mayor, M.; Ségransan, D.; Udry, S.; Tokovinin, A. A.;
Schertl, D.; Weigelt, G.; Balega, I. I.; Malogolovets, E. V.
Bibcode: 2007A&A...464..635B
Altcode:
Context: Because of the lack of precise masses, the coverage of
the main-sequence empirical mass-luminosity relation for stars
in the mass range from 0.6 M⊙ to 0.9 M⊙
is incomplete. The nearby K-type visual and spectroscopic binary GJ
765.2 = MLR 224 is a good candidate for new reliable points in this
significant part of the relation.
Aims: We have found a combined
orbital solution for the pair and derived physical properties of the
components using interferometric and spectroscopic data.
Methods:
The diffraction-limited speckle observations were mostly collected
at the 6 m BTA telescope, and the velocities of the components were
obtained using the CORAVEL radial velocity scanner on the Swiss 1 m
telescope.
Results: In a combined solution, the orbital period
is found to be 11.919 yr. The masses of the GJ 765.2 components are
MA=0.831± 0.020 M⊙ and MB=0.763±
0.019 M⊙. The obtained orbital parallax of the system,
π_orb=31.0±0.5 mas, is 7 percent lower than the Hipparcos value. The
absolute V magnitudes of the stars, derived from the measured speckle
magnitude differences, are: MVA=5.99±0.04
and MVB=6.64±0.05. The effective
temperatures of the components, T_effA=5060±130 K and
T_effB=4690±160 K, follow from the V-K and J-K color
indices. The star metallicity value, estimated from the 6 m telescope
spectrum, is [M/H]=-0.35±0.15 dex.
Conclusions: .The presented
individual masses have 2.4% and 2.5% relative accuracies. Therefore,
the components of GJ 765.2 rank among a dozen stars with masses accurate
to within a few percent in the mass range 0.6-0.9 M⊙. The
existing data on the kinematics of GJ 765.2 and its chromospheric
activity indicate that the binary belongs to the middle age (3-4×
109 yr) thin disk population of the galaxy. Based on
observations made with the 6 m BTA telescope, which is operated by
the Special Astrophysical Observatory, Russia, and the Observatoire
de Haute-Provence, operated by the Centre National de la Recherche
Scientifique de France. Tables 1 and 2 are only available in electronic
form at http://www.aanda.org
Title: Direct constraint on the distance of γ2 Velorum
from AMBER/VLTI observations
Authors: Millour, F.; Petrov, R. G.; Chesneau, O.; Bonneau, D.;
Dessart, L.; Bechet, C.; Tallon-Bosc, I.; Tallon, M.; Thiébaut,
E.; Vakili, F.; Malbet, F.; Mourard, D.; Antonelli, P.; Beckmann,
U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.; Gennari, S.;
Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut,
K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; Tatulli,
E.; Weigelt, G.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba,
E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker, T.;
Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse, J. -M.; Colin, J.;
Connot, C.; Delboulbé, A.; Domiciano de Souza, A.; Driebe, T.;
Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat, E.; Foy, R.;
Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin, A.;
Heiden, M.; Heininger, M.; Hernandez Utrera, O.; Hofmann, K. -H.;
Kamm, D.; Kiekebusch, M.; Kraus, S.; Le Contel, D.; Le Contel,
J. -M.; Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi,
A.; Mars, G.; Martinot-Lagarde, G.; Mathias, P.; Mège, P.; Monin,
J. -L.; Mouillet, D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier,
C.; Rabbia, Y.; Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.;
Sacchettini, M.; Schertl, D.; Schöller, M.; Solscheid, W.; Spang,
A.; Stee, P.; Stefanini, P.; Tasso, D.; Testi, L.; von der Lühe,
O.; Valtier, J. -C.; Vannier, M.; Ventura, N.
Bibcode: 2007A&A...464..107M
Altcode: 2006astro.ph.10936M
Context: Interferometry can provide spatially resolved observations of
massive star binary systems and their colliding winds, which thus far
have been studied mostly with spatially unresolved observations.
Aims: We present the first AMBER/VLTI observations, taken at
orbital phase 0.32, of the Wolf-Rayet and O (WR+O) star binary system
γ2 Velorum and use the interferometric observables
to constrain its properties.
Methods: The AMBER/VLTI instrument
was used with the telescopes UT2, UT3, and UT4 on baselines ranging
from 46 m to 85 m. It delivered spectrally dispersed visibilities,
as well as differential and closure phases, with a resolution R=1500
in the spectral band 1.95-2.17 μm. We interpret these data in the
context of a binary system with unresolved components, neglecting in a
first approximation the wind-wind collision zone flux contribution.
Results: Using WR- and O-star synthetic spectra, we show that the
AMBER/VLTI observables result primarily from the contribution of the
individual components of the WR+O binary system. We discuss several
interpretations of the residuals, and speculate on the detection of an
additional continuum component, originating from the free-free emission
associated with the wind-wind collision zone (WWCZ), and contributing at
most to the observed K-band flux at the 5% level. Based on the accurate
spectroscopic orbit and the Hipparcos distance, the expected absolute
separation and position angle at the time of observations were 5.1±0.9
mas and 66±15°, respectively. However, using theoretical estimates
for the spatial extent of both continuum and line emission from each
component, we infer a separation of 3.62+0.11-0.30
mas and a position angle of 73+9-11°, compatible
with the expected one. Our analysis thus implies that the binary system
lies at a distance of 368+38-13 pc, in agreement
with recent spectrophotometric estimates, but significantly larger
than the Hipparcos value of 258+41-31 pc. Based on observations collected at the European Southern Observatory,
Paranal, Chile, within the guaranteed time programme 074.A-9025(A).
Title: Optical configuration and analysis of the AMBER/VLTI instrument
Authors: Robbe-Dubois, S.; Lagarde, S.; Petrov, R. G.; Lisi,
F.; Beckmann, U.; Antonelli, P.; Bresson, Y.; Martinot-Lagarde,
G.; Roussel, A.; Salinari, P.; Vannier, M.; Chelli, A.; Dugué, M.;
Duvert, G.; Gennari, S.; Glück, L.; Kern, P.; Le Coarer, E.; Malbet,
F.; Millour, F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Tatulli, E.;
Weigelt, G.; Zins, G.; Accardo, M.; Acke, B.; Agabi, K.; Altariba,
E.; Arezki, B.; Aristidi, E.; Baffa, C.; Behrend, J.; Blöcker,
T.; Bonhomme, S.; Busoni, S.; Cassaing, F.; Clausse, J. -M.; Colin,
J.; Connot, C.; Delage, L.; Delboulbé, A.; Domiciano de Souza, A.;
Driebe, T.; Feautrier, P.; Ferruzzi, D.; Forveille, T.; Fossat, E.;
Foy, R.; Fraix-Burnet, D.; Gallardo, A.; Giani, E.; Gil, C.; Glentzlin,
A.; Heiden, M.; Heininger, M.; Hernandez Utrera, O.; Hofmann, K. -H.;
Kamm, D.; Kiekebusch, M.; Kraus, S.; Le Contel, D.; Le Contel, J. -M.;
Lesourd, T.; Lopez, B.; Lopez, M.; Magnard, Y.; Marconi, A.; Mars,
G.; Mathias, P.; Mège, P.; Monin, J. -L.; Mouillet, D.; Mourard,
D.; Nussbaum, E.; Ohnaka, K.; Pacheco, J.; Perrier, C.; Rabbia, Y.;
Rebattu, S.; Reynaud, F.; Richichi, A.; Robini, A.; Sacchettini,
M.; Schertl, D.; Schöller, M.; Solscheid, W.; Spang, A.; Stee, P.;
Stefanini, P.; Tallon, M.; Tallon-Bosc, I.; Tasso, D.; Testi, L.;
Vakili, F.; von der Lühe, O.; Valtier, J. -C.; Ventura, N.
Bibcode: 2007A&A...464...13R
Altcode: 2008arXiv0807.3717R
Aims:This paper describes the design goals and engineering efforts
that led to the realization of AMBER (Astronomical Multi BEam
combineR) and to the achievement of its present performance.
Methods: On the basis of the general instrumental concept, AMBER was
decomposed into modules whose functions and detailed characteristics
are given. Emphasis is put on the spatial filtering system, a key
element of the instrument. We established a budget for transmission
and contrast degradation through the different modules, and made the
detailed optical design. The latter confirmed the overall performance
of the instrument and defined the exact implementation of the AMBER
optics.
Results: The performance was assessed with laboratory
measurements and commissionings at the VLTI, in terms of spectral
coverage and resolution, instrumental contrast higher than 0.80,
minimum magnitude of 11 in K, absolute visibility accuracy of 1%,
and differential phase stability of 10-3 rad over one minute.
Title: VizieR Online Data Catalog: Temporal variations of the outer
atmosphere and the dust shell of the carbon-rich Mira variable V
Oph probed with VLTI/MIDI.
Authors: Ohnaka, K.; Driebe, T.; Weigelt, G.; Wittkowski, M.
Bibcode: 2007yCat..34661099O
Altcode:
N-band visibilities of the carbon-rich Mira variable V Oph observed
with VLTI/MIDI on six nights between April and September 2005. For
each data set, the visibilities at 101 wavelengths between 7.7 and
13.2 micron are tabulated. (1 data file).
Title: Interferometry in the Near-Infrared: 1 Mas Resolution at the
Wavelength of 1 Micron
Authors: Weigelt, G.; Balega, Y.; Beckert, T.; Driebe, T.; Hofmann,
K. -H.; Ohnaka, K.; Preibisch, T.; Schertl, D.; Wittkowski, M.
Bibcode: 2007ecf..book...63W
Altcode:
High-resolution interferometric imaging at optical and infrared
wavelengths provides unique information for the study of many different
classes of astronomical objects. A large number of key objects
have been resolved with unprecedented resolution using bispectrum
speckle interferometry or infrared long-baseline interferometry. IR
interferometry allows the study of, for example, disks and out-
flows of YSOs (e.g., [1]), the wavelength and phase-dependent size of
evolved stars (e.g., [2]), as well as the structure of AGN. The ESO Very
Large Telescope Interferometer with its AMBER phase-closure instrument
will enable us to achieve the spectacular resolution of 1 mas at the
wavelength of 1 micron. The science goals of AMBER include studies of
the jet structure of YSOs, the interferometric detection of extra-solar
planets as well as the resolution of tori and broad-line regions of AGN.
Title: Fizeau Interferometry with the LBT Astronomy on the Way to ELTs
Authors: Gaessler, W.; Herbst, T. M.; Ragazzoni, R.; Eckart, A.;
Weigelt, G.; Linc-Nirvana Team
Bibcode: 2007ecf..book...55G
Altcode:
The Large Binocular Telescope (LBT) consists of two 8.4 m mirrors on
one mechanical mounting, with a center to center separation of 14.4
m. In the combined, focus the LBT provides the spatial resolution
of a 23 m telescope and the sensitivity of a 12 m telescope. We are
building an instrument called LINC-NIRVANA using the capability of LBT
in Fizeau mode (imaging interferometry), leading to a unique combination
of spatial resolution, sensitivity and field of view. The instrument
will prove technology, such as Multi-Conjugated Adaptive Optics, which
is needed for the next generation of Extremely Large Telescopes (ELT)
(20 to 100 m diameter). The capabilities of LINC-NIRVANA will extend
science, especially for extragalactic programs, building a bridge
between current 10 m class telescopes and ELTs.
Title: The Vicinity of the Galactic Supergiant B[e] Star CPD-57°2874
from Near- and Mid-IR Long Baseline Spectro-Interferometry with the
VLTI (AMBER and MIDI)
Authors: Domiciano de Souza, A.; Driebe, T.; Chesneau, O.; Hofmann,
K. -H.; Kraus, S.; Miroshnichenko, A. S.; Ohnaka, K.; Petrov, R. G.;
Preibisch, Th.; Stee, Ph.; Weigelt, G.
Bibcode: 2006ASPC..355..155D
Altcode: 2005astro.ph.10736D
We present the first spectro-interferometric observations of the
circumstellar envelope (CSE) of a B[e] supergiant (CPD-57°2874}),
performed with the Very Large Telescope Interferometer (VLTI) using
the beam-combiner instruments AMBER (near-IR interferometry with
three 8.3~m Unit Telescopes or UTs) and MIDI (mid-IR interferometry
with two UTs). Our observations of the CSE are well fitted by an
elliptical Gaussian model with FWHM diameters varying linearly
with wavelength. Typical diameters measured are ≃1.8×3.4~mas
or ≃4.5×8.5~AU (adopting a distance of 2.5~kpc) at 2.2 μm, and
≃12×15~mas or ≃30×38~AU at 12 μm. We show that a spherical dust
model reproduces the SED but it underestimates the MIDI visibilities,
suggesting that a dense equatorial disk is required to account for the
compact dust-emitting region observed. Moreover, the derived major-axis
position angle in the mid-IR (≃144°) agrees well with previous
polarimetric data, hinting that the hot-dust emission originates in a
disk-like structure. Our results support the non-spherical CSE paradigm
for B[e] supergiants.
Title: A compact dusty disk around the Herbig Ae star HR 5999 resolved
with VLTI / MIDI
Authors: Preibisch, Th.; Kraus, S.; Driebe, Th.; van Boekel, R.;
Weigelt, G.
Bibcode: 2006A&A...458..235P
Altcode: 2006astro.ph..7497P
Aims.We have used mid-infrared long-baseline interferometry to
resolve the circumstellar material around the Herbig Ae star HR 5999,
providing the first direct measurement of its angular size, and to
derive constraints on the spatial distribution of the dust.
Methods: .MIDI at the VLTI was used to obtain a set of ten spectrally
dispersed (8-13 μm) interferometric measurements of HR 5999 at
different projected baseline lengths and position angles. To derive
constraints on the geometrical distribution of the dust, we compared
our interferometric measurements to 2D, frequency-dependent radiation
transfer simulations of circumstellar disks and envelopes.
Results: .The derived visibility values between 0.5 and 0.9 show
that the mid-infrared emission from HR 5999 is clearly resolved. The
characteristic size of the emission region depends on the projected
baseline length and position angle, and it ranges between 5-15
milliarcsec (Gauss FWHM), corresponding to remarkably small physical
sizes of 1-3 AU. For disk models with radial power-law density
distributions, the relatively weak but very extended emission from
outer disk regions (⪆ 3 AU) leads to model visibilities that are
significantly lower than the observed visibilities, making these models
inconsistent with the MIDI data. Disk models in which the density is
truncated at outer radii of 2 - 3 AU, on the other hand, provide good
agreement with the data.
Conclusions: .A satisfactory fit to
the observed MIDI visibilities of HR 5999 is found with a model of a
geometrically thin disk that is truncated at 2.6 AU and seen under an
inclination angle of 58degr (i.e. closer to an edge-on view than to a
face-on view). Neither models of a geometrically thin disk seen nearly
edge-on, nor models of spherical dust shells can achieve agreement
between the observed and predicted visibilities. The reason why the
disk is so compact remains unclear; we speculate that it has been
truncated by a close binary companion.
Title: Outflows from the high-mass protostars NGC
7538 IRS1/2 observed with bispectrum speckle
interferometry. Signatures of flow precession
Authors: Kraus, S.; Balega, Y.; Elitzur, M.; Hofmann, K. -H.;
Preibisch, Th.; Rosen, A.; Schertl, D.; Weigelt, G.; Young, E. T.
Bibcode: 2006A&A...455..521K
Altcode: 2006astro.ph..4328K
Context.NGC 7538 IRS1 is a high-mass
(30 M⊙) protostar with a CO outflow, an associated
ultracompact H II region, and a linear methanol maser structure, which
might trace a Keplerian-rotating circumstellar disk. The directions
of the various associated axes are misaligned with each other.
Aims.We investigate the near-infrared morphology of the source to
clarify the relations among the various axes.
Methods.K'-band
bispectrum speckle interferometry was performed at two 6-meter-class
telescopes - the BTA 6 m telescope and the 6.5 m MMT. Complementary
IRAC images from the Spitzer Space Telescope Archive were used to
relate the structures detected with the outflow at larger scales.
Results.High-dynamic range images show fan-shaped outflow structure
in which we detect 18 stars and several blobs of diffuse emission. We
interpret the misalignment of various outflow axes in the context of
a disk precession model, including numerical hydrodynamic simulations
of the molecular emission. The precession period is ~280 years and
its half-opening angle is ~40°. A possible triggering mechanism is
non-coplanar tidal interaction of an (undiscovered) close companion
with the circumbinary protostellar disk. Our observations resolve
the nearby massive protostar NGC 7538 IRS2 as a
close binary with separation of 195 mas. We find indications for shock
interaction between the outflow activities in IRS1 and IRS2. Finally,
we find prominent sites of star formation at the interface between
two bubble-like structures in NGC 7538, suggestive of a triggered star
formation scenario.
Conclusions.Indications of outflow precession
have been discovered to date in a number of massive protostars,
all with large precession angles (~20-45°). This might explain the
difference between the outflow widths in low- and high-mass stars and
add support to a common collimation mechanism.
Title: MATISSE: a four beams combiner in the mid-infrared for the VLTI
Authors: Lagarde, S.; Lopez, B.; Antonelli, P.; Beckman, U.; Behrend,
J.; Bresson, Y.; Chesneau, O.; Dugué, M.; Glazenborg, A.; Graser,
U.; Hofmann, K. H.; Jaffe, W.; Leinert, Ch.; Millour, F.; Menut,
J. L.; Petrov, R. G.; Ratzka, T.; Weigelt, G.; Wolf, S.; Abraham, P.;
Connot, C.; Henning, T.; Heininger, M.; Hugues, Y.; Kraus, S.; Laun,
W.; Matter, A.; Neumann, U.; Nussbaum, E.; Niedzielski, A.; Mosoni,
L.; Robbe-Dubois, S.; Roussel, A.; Schertl, D.; Vakili, F.; Wagner,
K.; Waters, L. B. F. M.
Bibcode: 2006SPIE.6268E..3ML
Altcode: 2006SPIE.6268E.115L
A first generation of VLTI (Very Large Telescopes Interferometer) focal
instruments, AMBER in the near-infrared and MIDI in the mid-infrared,
has been already integrated and tested. New and important science
results have been obtained. These instruments combine two (for MIDI)
or three (for AMBER) beams coming from the eight telescopes installed
at Cerro Paranal (four 8-meters and four 1.8-meters telescopes). In
order to improve the capabilities of the interferometer and to
engage a new scientific prospective, the second generation of VLTI
instruments is currently under study. MATISSE belongs to this second
generation. MATISSE objective is the image reconstruction. It will
extend the astrophysical potential of the VLTI by overcoming the
ambiguities existing in the interpretation of simple visibility
measurements. It is a spectro-interferometer combining up to four
beams with a large spectral coverage ranging from 3 to 25 μm (L,
M, N and Q bands). Different spectral resolutions (between 30 and
1500) are foreseen. MATISSE will measure closure phase relations thus
offering an efficient capability for image reconstruction. The concept
of MATISSE is presented in this paper. The recombination mode of MATISSE
is similar to the AMBER beam combination, but has been adapted to the
constraints specific to the mid-infrared domain.
Title: Aperture synthesis imaging with the LBT: reconstruction of
diffraction-limited images from LBT LINC-NIRVANA data using the
Richardson-Lucy and regularized building block method
Authors: Hofmann, Karl-Heinz; Driebe, Thomas; Heininger, Mathias;
Schertl, Dieter; Weigelt, Gerd
Bibcode: 2006SPIE.6268E..3HH
Altcode: 2006SPIE.6268E.111H
The regularized and space-variant Building Block method allow the
reconstruction of diffraction-limited aperture-synthesis images from
Large Binocular Telescope (LBT) LINC-NIRVANA data. Images with the
diffraction-limited resolution of a 22.8 m single-dish telescope
can be reconstructed if raw images are taken at several different
hour angles. Computer-generated and laboratory LBT interferograms
were simulated that are similar to the data which can be obtained
with the LINC-NIRVANA beam combiner instrument. From the simulated
interferograms, diffraction-limited images were reconstructed with
the regularized Building Block method, which is an extension of the
Building Block method. We compare the Building Block reconstructions
to images obtained with the Richardson-Lucy (RL) method and the Ordered
Subsets Expectation Maximization (OSEM) method. Our image reconstruction
studies were performed with computer-simulated J-band and laboratory
H-band raw data of a galaxy with simulated total magnitudes of J = 16
to 18 and H = 16 to 19, respectively. One of the faintest structures
in the images has a brightness of J~25. The simulated reference stars
within the isoplanatic patch have magnitudes of J = 20 - 21 and H =
19. All three methods are able to reconstruct diffraction-limited
images of similar quality.
Title: Aperture synthesis image reconstruction study for the
mid-infrared VLTI imager MATISSE
Authors: Hofmann, Karl-Heinz; Kraus, Stefan; Lopez, Bruno; Weigelt,
Gerd; Wolf, Sebastian
Bibcode: 2006SPIE.6268E..3IH
Altcode: 2006SPIE.6268E.112H
Aperture synthesis imaging provides a way to overcome the ambiguities
which often exist in the interpretation of single-baseline
interferometric visibility measurements. The mid-infrared imager
MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment), which
was proposed to ESO as a second-generation VLTI instrument, is designed
to combine up to four 8.2 m VLTI UTs or 1.8 m ATs while simultaneously
providing a high spectroscopic resolution. To demonstrate that MATISSE
will allow high-quality interferometric imaging within realistic
observation time constraints, we performed an image reconstruction
study, for which we simulated the uv-coverage achievable in 3, 5,
or 7 nights with 3 or 4 telescopes. As input image for our studies,
a protostellar disk image was simulated with the radiative transfer
code MC3D1 . From the simulated visibilities and closure
phases, we derived aperture synthesis images using the Building Block
algorithm2 . The main features of the disk image could
be reconstructed in the presence of noise and assuming the sparse
uv-coverage achievable within just 3 nights of observations.
Title: 2006 interferometry imaging beauty contest
Authors: Lawson, Peter R.; Cotton, William D.; Hummel, Christian A.;
Baron, Fabien; Young, John S.; Kraus, Stefan; Hofmann, Karl-Heinz;
Weigelt, Gerd P.; Ireland, Michael; Monnier, John D.; Thiébaut,
Eric; Rengaswamy, Sridharan; Chesneau, Olivier
Bibcode: 2006SPIE.6268E..1UL
Altcode: 2006SPIE.6268E..59L
We present a formal comparison of the performance of algorithms
used for synthesis imaging with optical/infrared long-baseline
interferometers. Five different algorithms are evaluated based on
their performance with simulated test data. Each set of test data
is formatted in the OI-FITS format. The data are calibrated power
spectra and bispectra measured with an array intended to be typical
of existing imaging interferometers. The strengths and limitations of
each algorithm are discussed.
Title: The imaging fringe and flexure tracker of LINC-NIRVANA:
basic opto-mechanical design and principle of operation
Authors: Straubmeier, Christian; Bertram, Thomas; Eckart, Andreas;
Rost, Steffen; Wang, Yeping; Herbst, Tom; Ragazzoni, Roberto;
Weigelt, Gerd
Bibcode: 2006SPIE.6268E..1IS
Altcode: 2006SPIE.6268E..48S
LINC-NIRVANA is the interferometric near-infrared imaging camera for the
Large Binocular Telescope (LBT). Being able to observe at wavelength
bands from J to K (suppported by an adaptive optics system operating
at visible light) LINC-NIRVANA will provide an unique and unprecedented
combination of high angular resolution (~ 9 milliarcseconds at 1.25μm),
wide field of view (~ 100 arcseconds2 at 1.25μm), and large
collecting area (~ 100m2). One of the major contributions
of the 1. Physikalische Institut of the University of Cologne to
this project is the development and provision of the Fringe and
Flexure Tracking System (FFTS). In addition to the single-eye adaptive
optics systems the FFTS is a crucial component to ensure a time-stable
wavefront correction over the full aperture of the double-eye telescope,
a mandatory pre-requisite for interferometric observations. Using a
independent HAWAII 1 detector array at a combined focus close to the
science detector, the Fringe and Flexure Tracking System analyses the
complex two-dimensional interferometric point spread function (PSF)
of a suitably bright reference source at frame rates of up to several
hundred Hertz. By fitting a parameterised theoretical model PSF to the
preprocessed image-data the FFTS determines the amount of pistonic
phase difference and angular misalignment between the wavefronts
of the two optical paths of LINC-NIRVANA. For every exposure the
corrective parameters are derived in real-time and transmitted to a
dedicated piezo-electric fast linear mirror for simple path lengths
adjustments, and/or to the adaptive optics systems of the single-eye
telescopes for more complicated corrections. In this paper we present
the basic concept and currect status of the opto-mechanical design of
the Fringe and Flexure Tracker, the operating principle of the fringe
and flexure tracking loops, and the encouraging result of a laboratory
test of the piston control loop.
Title: Radiative transfer modeling of three-dimensional clumpy AGN
tori and its application to NGC 1068
Authors: Hönig, S. F.; Beckert, T.; Ohnaka, K.; Weigelt, G.
Bibcode: 2006A&A...452..459H
Altcode: 2006astro.ph..2494H
Recent observations of NGC 1068 and other AGN support the idea of a
geometrically and optically thick dust torus surrounding the central
supermassive black hole and accretion disk of AGN. In type 2 AGN,
the torus is seen roughly edge-on, leading to obscuration of the
central radiation source and a silicate absorption feature near 10 {μ
m}. While most of the current torus models distribute the dust smoothly,
there is growing evidence that the dust must be arranged in clouds. We
describe a new method for modeling near- and mid-infrared emission of
3-dimensional clumpy tori using Monte Carlo simulations. We calculate
the radiation fields of individual clouds at various distances from the
AGN and distribute these clouds within the torus region. The properties
of the individual clouds and their distribution within the torus are
determined from a theoretical approach of self-gravitating clouds close
to the shear limit in a gravitational potential. We demonstrate that
clumpiness in AGN tori can overcome the problem of over-pronounced
silicate features. Finally, we present model calculations for the
prototypical Seyfert 2 galaxy NGC 1068 and compare them to recent
high-resolution measurements. Our model is able to reproduce both
the SED and the interferometric observations of NGC 1068 in the near-
and mid-infrared.
Title: MATISSE: perspective of imaging in the mid-infrared at the VLTI
Authors: Lopez, B.; Wolf, S.; Lagarde, S.; Abraham, P.; Antonelli,
P.; Augereau, J. C.; Beckman, U.; Behrend, J.; Berruyer, N.;
Bresson, Y.; Chesneau, O.; Clausse, J. M.; Connot, C.; Demyk, K.;
Danchi, W. C.; Dugué, M.; Flament, S.; Glazenborg, A.; Graser, U.;
Henning, T.; Hofmann, K. H.; Heininger, M.; Hugues, Y.; Jaffe, W.;
Jankov, S.; Kraus, S.; Laun, W.; Leinert, Ch.; Linz, H.; Mathias,
Ph.; Meisenheimer, K.; Matter, A.; Menut, J. L.; Millour, F.;
Neumann, U.; Nussbaum, E.; Niedzielski, A.; Mosonic, L.; Petrov, R.;
Ratzka, T.; Robbe-Dubois, S.; Roussel, A.; Schertl, D.; Schmider,
F. -X.; Stecklum, B.; Thiebaut, E.; Vakili, F.; Wagner, K.; Waters,
L. B. F. M.; Weigelt, G.
Bibcode: 2006SPIE.6268E..0ZL
Altcode: 2006SPIE.6268E..31L
Our objective is the development of mid-infrared imaging at the
VLTI. The related science case study demonstrates the enormous
capability of a new generation mid-infrared beam combiner. MATISSE will
constitute an evolution of the two-beam interferometric instrument
MIDI by increasing the number of recombined beams up to four. MIDI
is a very successful instrument which offers a perfect combination
of spectral and angular resolution. New characteristics present in
MATISSE will give access to the mapping and the distribution of the
material (typically dust) in the circumstellar environments by using
a wide mid-infrared band coverage extended to L, M, N and Q spectral
bands. The four beam combination of MATISSE provides an efficient
UV-coverage: 6 visibility points are measured in one set and 4 closure
phase relations which can provide for the first time aperture synthesis
images in the mid-infrared spectral regime. The mid-infrared spectral
domain is very relevant for the study of the environment of various
astrophysical sources. Our science case studies show the wide field of
applications of MATISSE. They will be illustrated in the first part of
this presentation through the perspective of imaging the circumstellar
environments/discs of young stellar objects. The MATISSE characteristics
will be given in a second part of the presentation.
Title: VSI: a milli-arcsec spectro-imager for the VLTI
Authors: Malbet, F.; Kern, P. Y.; Berger, J. -P.; Jocou, L.; Garcia,
P.; Buscher, D.; Rousselet-Perraut, K.; Weigelt, G.; Gai, M.; Surdej,
J.; Hron, J.; Neuhäuser, R.; Le Coarer, E.; Labeye, P. R.; Le Bouquin,
J.; Benisty, M.; Herwats, E.
Bibcode: 2006SPIE.6268E..0YM
Altcode: 2006astro.ph..7291M
VLTi Spectro-Imager (VSI) is a proposition for a second generation
VLTI instrument which is aimed at providing the ESO community with the
capability of performing image synthesis at milli-arcsecond angular
resolution. VSI provides the VLTI with an instrument able to combine
4 telescopes in a baseline version and optionally up to 6 telescopes
in the near-infrared spectral domain with moderate to high spectral
resolution. The instrument contains its own fringe tracker in order
to relax the constraints onto the VLTI infrastructure. VSI will do
imaging at the milli-arcsecond scale with spectral resolution of: a)
the close environments of young stars probing the initial conditions
for planet formation; b) the surfaces of stars; c) the environment of
evolved stars, stellar remnants and stellar winds, and d) the central
region of active galactic nuclei and supermassive black holes. The
science cases allowed us to specify the astrophysical requirements
of the instrument and to define the necessary studies of the science
group for phase A.
Title: First astrophysical results from AMBER/VLTI
Authors: Malbet, F.; Petrov, R. G.; Weigelt, G.; Stee, P.; Tatulli,
E.; Domiciano de Souza, A.; Millour, F.
Bibcode: 2006SPIE.6268E..02M
Altcode: 2006astro.ph..6484M; 2006SPIE.6268E...2M
The AMBER instrument installed at the Very Large Telescope
(VLT) combines three beams from as many telescopes to produce
spectrally dispersed fringes from milli-arcsecond angular scale in
the near infrared. Two years after installation, first scientific
observations have been carried out during the Science Demonstration
Time and the Guaranteed Time mostly on bright sources due to some VLTI
limitations. In this paper, we review these first astrophysical results
and we show which types of completely new information is brought by
AMBER. The first astrophysical results have been mainly focusing
on stellar wind structure, kinematics, and its interaction with
dust usually concentrated in a disk. Because AMBER has dramatically
increased the number of measures per baseline, this instrument brings
strong constraints on morphology and models despite a relatively poor
(u,v) coverage for each object.
Title: VLTI/MIDI observation of the silicate carbon star Hen 38
(IRAS08002-3803): silicate dust reservoir spatially resolved for
the first time
Authors: Ohnaka, Keiichi; Driebe, Thomas; Hofmann, Karl-Heinz;
Preibisch, Thomas; Schertl, Dieter; Weigelt, Gerd
Bibcode: 2006SPIE.6268E..2VO
Altcode: 2006SPIE.6268E..91O
We present the results of N-band spectro-interferometric observations
of the silicate carbon star Hen 38 (IRAS08002-3803) with the
MID-infrared Interferometric instrument (MIDI) at the Very Large
Telescope Interferometer (VLTI) of the European Southern Observatory
(ESO). Our observations of IRAS08002-3803 with baseline lengths of
39-47 m have spatially resolved the dusty environment of a silicate
carbon star for the first time and revealed an unexpected wavelength
dependence of the angular size in the N band: the uniform-disk diameter
is found to be constant and ~36 mas (72 R *) between 8 and
10 μm, while it steeply increases longward of 10 μm to reach ~53
mas (106 R *) at 13 μm. Neither spherical shell models
nor axisymmetric disk models consisting of silicate grains alone can
simultaneously explain the observed wavelength dependence of the
visibility and the spectral energy distribution (SED). We propose
that the circumstellar environment of IRAS08002-3803 may consist of
two grain species coexisting in the disk: silicate and a second grain
species, for which we consider amorphous carbon, large silicate grains,
and metallic iron grains. Comparison of the observed visibilities
and SED with our models shows that such disk models can fairly -
though not entirely satisfactorily - reproduce the observed SED and
N-band visibilities. Our MIDI observations and the radiative transfer
calculations lend support to the picture where oxygen-rich material
around IRAS08002-3803 is stored in a circumbinary disk surrounding
the carbon-rich primary star and its putative low-luminosity companion.
Title: VEGA: a visible spectrograph and polarimeter for CHARA -
science cases description
Authors: Stee, Philippe; Mourard, Denis; Bonneau, Daniel;
Berlioz-Arthaud, Paul; Domiciano de Souza, Armando; Foy, Renaud;
Harmanec, Petr; Jankov, Slobodan; Kervella, Pierre; Koubsky,
Pavel; Lagarde, Stéphane; Le Bouquin, Jean-Baptiste; Mathias,
Philippe; Mérand, Antoine; Nardetto, Nicolas; Petrov, Romain G.;
Rousselet-Perraut, Karine; Stehle, Chantal; Weigelt, Gerd
Bibcode: 2006SPIE.6268E..3RS
Altcode: 2006SPIE.6268E.119S
Interferometry has been intensively done at long wavelengths, starting
with the radio interferometers in the years 50 since it was easier to
guide radio wavelengths in cable while keeping the phase information or
using a local oscillator and a correlator to recombine "a posteriori"
the beams over intercontinental distances. In the optical a lot of work
as been done at IR and near-IR wavelengths since it was technically
easier, or we must say, less difficult to recombine directly the
optical beams since the coherence length is larger and the turbulence
slower than at shorter wavelengths. Therefore, the visible domain of
the electromagnetic spectrum is not covered at the same level than
near or mid infrared. Some very nice and important results have been
however obtained with the GI2T interferometer in south of France,
the Mark III interferometer on the Mount Wilson, USA, the NPOI array
in Flagstaff, USA or the SUSI interferometer in Australia. We will
present in this paper the science cases of a new but already existing
and tested instrument: the REGAIN focal instrument which was designed
and built for the GI2T. This instrument, in his CHARA adaptation, called
VEGA will open new fields in a wide range of Astrophysical topics
only addressable in the visible domain. It will provide a spectral
resolution up to 30000 within the spectral range 0.4-0.9 micron and
a spatial resolution of less than 1mas for up to 4 telescopes in its
X-lambda special configuration. A polarimetric device (SPIN) measuring
simultaneously the polarization in 2 directions either circular or
linear is also implemented in this instrument. Since VEGA was already
tested on the sky on 1.5 m telescopes it is also very well suited
for the 1m CHARA array and will only need minor adaptations for the
injection of the CHARA beams. This paper will focus on some of the most
promising science drivers only possible with this visible instrument.
Title: VLTI-AMBER observations of Eta Carinae with high spatial
resolution and spectral resolutions of 1,500 and 10,000
Authors: Weigelt, Gerd; Petrov, Romain G.; Chesneau, Olivier;
Davidson, Kris; Domiciano de Souza, Armando; Driebe, Thomas; Foy,
Renaud; Fraix-Burnet, Didier; Gull, Ted; Hillier, John D.; Hofmann,
Karl-Heinz; Kraus, Stefan; Malbet, Fabien; Marconi, Alessandro;
Mathias, Philippe; Monin, Jean-Louis; Millour, Florentin; Ohnaka,
Keiichi; Rantakyrö, Frederik; Richichi, Andrea; Schertl, Dieter;
Schöller, Markus; Stee, Philippe; Testi, Leonardo; Wittkowski, Markus
Bibcode: 2006SPIE.6268E..2SW
Altcode: 2006SPIE.6268E..88W
We present the first interferometric NIR observations of the LBV η
Carinae with high spectral resolution. The observations were carried out
with three 8.2 m VLTI Unit Telescopes in the K-band. The raw data are
spectrally dispersed interferograms obtained with spectral resolutions
of 1,500 (MR-K mode) and 12,000 (HR-K mode). The observations were
performed in the wavelength range around both the He I 2.059 μm and
the Brγ 2.166 μm emission lines. The spectrally dispersed AMBER
interferograms allow the investigation of the wavelength dependence of
the visibility, differential phase, and closure phase of η Car. In
the K-band continuum, a diameter of 4.0+/-0.2 mas (Gaussian FWHM)
was measured for η Car's optically thick wind region, whereas the
Brγ and He I emission line regions are larger. If we fit Hillier et
al. model visibilities to the observed AMBER visibilities, we obtain
50% encircled-energy diameters of 4.3, 6.5 and 9.6 mas in the 2.17 μm
continuum, the He I, and the Brγemission lines, respectively. In the
continuum near the Brγ line, an elongation along a position angle
of 128° +/- 15° was found, consistent with previous VLTI/VINCI
measurements. We find good agreement between the measured visibilities
and the predictions of the radiative transfer model of Hillier et
al. For the interpretation of the non-zero differential and closure
phases measured within the Brγ line, we present a simple geometric
model of an inclined, latitude-dependent wind zone. Our observations
support theoretical models of anisotropic winds from fast-rotating,
luminous hot stars with enhanced high-velocity mass loss near the
polar regions.
Title: Moving shadows on the dusty disks of young stars
Authors: Tambovtseva, L. V.; Grinin, V. P.; Weigelt, G.
Bibcode: 2006A&A...448..633T
Altcode:
We investigate the formation of moving shadows on the circumbinary (CB)
disk of young binary systems. Moving shadows can be created by a dusty
disk wind of the secondary component. The densest parts of the dusty
disk wind and the associated common envelope can be optically thick and
may block the stellar radiation inside a certain solid angle, resulting
in the appearance of a moving shadow zone. Its shape and size depends
on the mass loss rate, the disk wind velocity, and optical properties
of the dust. Our calculations show that the shadow zone is observable
if the mass loss rate dot Mw is greater than 10-9
M⊙ per year. This shadow resembles a clock hand. If the
orbit is an elliptical, the properties of this clock hand will change
during the orbital motion of the secondary.
Title: Near-infrared speckle interferometry and radiative transfer
modelling of the carbon star LP Andromedae
Authors: Men'shchikov, A. B.; Balega, Y. Y.; Berger, M.; Driebe,
T.; Hofmann, K. -H.; Maximov, A. F.; Schertl, D.; Shenavrin, V. I.;
Weigelt, G.
Bibcode: 2006A&A...448..271M
Altcode:
We present the near-infrared speckle interferometry for LP
And in the H and K' bands with diffraction-limited resolutions
of 56 and 72 mas, new JHKLM photometry, and the results of our
radiative transfer modelling of this carbon star. The reconstructed
visibility reveals a spherically-symmetric envelope surrounding the
central star. To determine the physical parameters of the latter and
the properties of its dusty envelope, we performed extensive radiative
transfer calculations. The well-defined spectral energy distribution
of LP And in the entire range from the near-IR to
millimeter wavelengths (including the absorption feature visible in the
stellar continuum at 3 μm and the shapes of the dust emission bands at
11 and 27 μm), together with our H-band visibility can be reproduced
by a spherical dust envelope with parameters that are very similar to
those of CW Leo (IRC +10 216), the
best studied carbon star. For the newly estimated pulsation period P =
617 ± 6 days and distance D = 740 ± 100 pc, our model of LP
And changes its luminosity Lstar between 16 200 and
2900 L⊙, its effective temperature Tstar between
3550 and 2100 K, and its radius Rstar between 340 and 410
R⊙. The model estimates the star's mass-loss rate dot{M}
≈ 1.9 × 10-5 M⊙ yr- 1, assuming a
constant outflow velocity v = 14 km s-1. If the latter also
applied to the innermost parts of the dusty envelope, then presently the
star would be losing mass at a rate dot{M} ≈ 6.0 × 10-5
M⊙ yr-1. However, we believe that the inner
wind velocity must actually be closer to v ≈ 4 km s-1
instead, as wind acceleration is expected in the dust-formation
zone. The dusty envelope of LP And extends from
R1 ≈ 2 Rstar to distances of R2
≈ 3 pc from the star. The total mass of the envelope lost by the
central star is M = 3.2 M⊙ assuming a dust-to-gas mass
ratio of ρ_d/ρ = 0.0039. The circumstellar optical depth towards
the star is τV = 25 in the visual. The dust model contains
small silicon carbide grains, inhomogeneous grains made of a mixture
of SiC and incompletely amorphous carbon, and thin mantles made of
iron-magnesium sulfides. This dust mixture perfectly fits the infrared
continuum and both the 11.3 μm and 27 μm emission bands. We find that
our K'-band visibility could not be fitted by our spherical model, so we
discuss possible reasons for this interesting result. More observations
are required in order to determine what causes this effect. If slight
deviations from spherical geometry in its envelope are the reason, then
the object's evolutionary stage would be even more similar to that of
CW Leo. It appears that LP And is
a highly-evolved intermediate-mass star (initial mass M^0star
≈ 4 M⊙) at the end of its AGB phase.
Title: Orbits of new Hipparcos binaries. II
Authors: Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.; Malogolovets,
E. V.; Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2006A&A...448..703B
Altcode:
We continue the presentation of new orbits for Hipparcos binaries
determined from regular speckle interferometric observations. Most of
the data were collected in the period between 1998.77 and 2004.82 using
the 6 m BTA telescope of the Special Astrophysical Observatory
in Zelenchuk. New orbits are presented for six pairs: HIP 4809,
HIP 4849, HIP 5531, HIP 19206, HIP 105947, and HIP 114922. One
of the pairs, HIP 114922, has M dwarf components orbiting with a
period of 19.72 yr. Two binaries, HIP 4809 and HIP 5531, have
luminosity class IV components. The periods of the orbits range from
7.30 yr to 28.99 yr. All of the orbits can be considered definitive;
however, the total mass error for the systems remains high, mainly
due to Hipparcos parallax error.
Title: Photopolarimetric activity and circumstellar environment of
the young binary system DF Tau
Authors: Shakhovskoj, D.; Grinin, V.; Rostopchina, A.; Schertl, D.;
Hofmann, K. -H.; Weigelt, G.; Balega, Yu.; Kiyaeva, O.; Melnikov, S.
Bibcode: 2006A&A...448.1075S
Altcode:
We present the results of multi-year photometric and polarimetric
observations of the young binary system DF Tau in the UBVRI bands, as
well as bispectrum speckle interferometric observations in the H and K
bands obtained between 2001 and 2003. The photometric and polarimetric
observations suggest that the linear polarization of DF Tau does
not depend on its brightness, and the polarization variation has a
stochastic character. This result confirms earlier suggestions about
the dominant role of hot accretion spots in the photometric activity
of this star. We argue that the hot spots are at high latitudes and/or
the star rotation axis is inclined to the line-of-sight. The influence
of circumstellar (CS) dust on the variability is probably small since
the inclination of the primary's CS disk to the line-of-sight is
large. Using the total mass of the binary system DF Tau from Hartigan
& Kenyon (2003, ApJ, 583, 334), we calculated new orbital parameters
of the system. The new value of the orbital period (P = 74.1 yr)
disagrees with the photometric cycle of about 40 yr revealed by Lamzin
et al. (2001b, A&A, 372, 922) from analysis of the historical light
curve of this star. This suggests that this cycle is not caused by the
orbital motions of the binary components, but probably reflects the
cyclical variability of the global magnetic field on the main component.
Title: Bispectrum speckle interferometry of the massive protostellar
outflow source IRAS 23151+5912
Authors: Weigelt, G.; Beuther, H.; Hofmann, K. -H.; Meyer, M. R.;
Preibisch, Th.; Schertl, D.; Smith, M. D.; Young, E. T.
Bibcode: 2006A&A...447..655W
Altcode: 2005astro.ph.11178W
We present bispectrum speckle interferometry of the massive protostellar
object IRAS 23151+5912 in the near-infrared K' band. The reconstructed
image shows the diffuse nebulosity north-east of two point-like sources
in unprecedented detail. The comparison of our near-infrared image
with mm continuum and CO molecular line maps shows that the brighter of
the two point sources lies near the center of the mm peak, indicating
that it is a high-mass protostar. The nebulosity coincides with the
blue-shifted molecular outflow component. The most prominent feature
in the nebulosity is a bow-shock-like arc. We assume that this feature
is associated with a precessing jet which has created an inward-pointed
cone in the swept-up material. We present numerical jet simulations that
reproduce this and several other features observed in our speckle image
of the nebulosity. Our data also reveal a linear structure connecting
the central point source to the extended diffuse nebulosity. This
feature may represent the innermost part of a jet that drives the
strong molecular outflow (PA ∼ 80°) from IRAS 23151+5912. With
the aid of radiative transfer calculations, we demonstrate that, in
general, the observed inner structures of the circumstellar material
surrounding high-mass stars are strongly influenced by the orientation
and symmetry of the bipolar cavity.
Title: High angular resolution N-band observation of the silicate
carbon star IRAS08002-3803 with the VLTI/MIDI instrument . Dusty
environment spatially resolved
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Leinert, Ch.; Morel,
S.; Paresce, F.; Preibisch, Th.; Richichi, A.; Schertl, D.; Schöller,
M.; Waters, L. B. F. M.; Weigelt, G.; Wittkowski, M.
Bibcode: 2006A&A...445.1015O
Altcode: 2005astro.ph..9746O
We present the results of N-band spectro-interferometric
observations of the silicate carbon star IRAS08002-3803 with the
MID-infrared Interferometric instrument (MIDI) at the Very Large
Telescope Interferometer (VLTI) of the European Southern Observatory
(ESO). The observations were carried out using two unit telescopes
(UT2 and UT3) with projected baseline lengths ranging from 39 to 47
m. Our observations of IRAS08002-3803 have spatially resolved the
dusty environment of a silicate carbon star for the first time and
revealed an unexpected wavelength dependence of the angular size in
the N band: the uniform-disk diameter is found to be constant and
36 mas (72 Rstar) between 8 and 10 μm, while it steeply
increases longward of 10 μm to reach 53 mas (106 Rstar) at
13 μm. Model calculations with our Monte Carlo radiative transfer code
show that neither spherical shell models nor axisymmetric disk models
consisting of silicate grains alone can simultaneously explain the
observed wavelength dependence of the visibility and the spectral energy
distribution (SED). We propose that the circumstellar environment of
IRAS08002-3803 may consist of two grain species coexisting in the disk:
silicate and a second grain species, for which we consider amorphous
carbon, large silicate grains, and metallic iron grains. Comparison of
the observed visibilities and SED with our models shows that such disk
models can fairly - though not entirely satisfactorily - reproduce
the observed SED and N-band visibilities. Our MIDI observations and
the radiative transfer calculations lend support to the picture
where oxygen-rich material around IRAS08002-3803 is stored in a
circumbinary disk surrounding the carbon-rich primary star and its
putative low-luminosity companion.
Title: NIR high-resolution imaging and radiative transfer modeling
of the Frosty Leo nebula
Authors: Murakawa, K.; Ohnaka, K.; Driebe, T.; Hofmann, K. -H.;
Schertl, D.; Oya, S.; Weigelt, G.
Bibcode: 2006IAUS..234..473M
Altcode:
We present a K'-band speckle image and HK-band polarimetric images
of the proto-planetary nebula Frosty Leo obtained using the 6 m SAO
telescope and the 8 m Subaru telescope, respectively. Our speckle image
revealed clumpy structures in the hourglass-like bipolar nebula. The
polarimetric data, for the first time, detected an elongated region
with small polarizations and polarization vector alignment on the
east side of the central star. We have performed radiative transfer
calculations to model the dust shell of Frosty Leo. We found that
micron-size grains in the equatorial dense region and small grains in
the bipolar lobes are required to explain the total intensity images,
the polarization images, and the spectral energy distribution.
Title: Molecular jet simulation with a large precession angle and
its application to emission from NGC 7538 IRS1
Authors: Rosen, A.; Kraus, S.; Weigelt, G.; Smith, M. D.
Bibcode: 2005AAS...207.7416R
Altcode: 2005BAAS...37.1286R
Recent high resolution bispectrum speckle interferometric observations
in the near-infrared have revealed that the area surrounding NGC 7538
IRS1 is associated with a fan-like region that contains several stars
and regions of diffuse emission. An interpretation of the speckle,
CO, and methanol maser data, which shows the current position angle
of the protostar's accretion disk on the sky, is of a jet with a
large precession angle. Here, we run a molecular jet simulation with
a similarly wide precession angle. We analyze the simulation for
properties associated with the flow and the calculated emission. We
can reproduce the ``older" average position angle for the CO emission,
compared with a more recent value from molecular hydrogen (i.e., shocked
gas) emission (which we use as a proxy for the K' band emission). Thus,
the model is consistent with the interpretation that a precessing jet
is responsible for much of the molecular emission (covering different
emission lines) in the IRS1 region.
Title: Reconstruction of aperture-synthesis images from LBT
LINC-NIRVANA data using the Richardson-Lucy and space-variant Building
Block method
Authors: Hofmann, K. -H.; Driebe, T.; Heininger, M.; Schertl, D.;
Weigelt, G.
Bibcode: 2005A&A...444..983H
Altcode:
We present a new method, the regularized and space-variant Building
Block method, which is able to reconstruct diffraction-limited
aperture-synthesis images from Large Binocular Telescope (LBT)
LINC-NIRVANA data. Images with the diffraction-limited resolution of
a 22.8 m single-dish telescope can be derived if raw images are taken
at several different hour angles. We simulated computer-generated
and laboratory LBT interferograms that are similar to the data which
can be obtained with the LINC-NIRVANA beam combiner instrument. From
the simulated data, diffraction-limited images were reconstructed
with the regularized Building Block method, which is an extension
of the Building Block method (Hofmann & Weigelt 1993, A&A,
278, 328). We compare the Building Block reconstructions to images
obtained with the Richardson-Lucy (RL) method (Richardson 1972,
J. Opt. Soc. Am., 62, 55; Lucy 1974, AJ, 79, 745) and the Ordered
Subsets Expectation Maximization (OSEM) method (Hudson & Larkin
1994, IEEE Trans. Med. Imag., 13, 601; Bertero & Boccacci 2000,
A&AS, 144, 181). Our image reconstruction studies were performed
with computer-simulated J-band and laboratory H-band raw data of
a galaxy with simulated total magnitudes of J = 16m to
18m and H = 16m to 19^m, respectively. One
of the faintest structures in the images has a brightness of J ∼
25^m. The simulated reference stars within the isoplanatic patch have
magnitudes of J = 20^m{-}21m and H = 19^m. All three methods
are able to reconstruct diffraction-limited images with almost the same
quality. Furthermore, raw data with space-variant point spread functions
were simulated, and diffraction-limited images were reconstructed
using the space-variant version of the Building Block method.
Title: LINC-NIRVANA: MCAO toward Extremely Large Telescopes
Authors: Gaessler, W.; Arcidiacono, C.; Egner, S.; Herbst, T. M.;
Andersen, D.; Baumeister, H.; Bizenberger, P.; Boehnhardt, H.; Briegel,
F.; Kuerster, M.; Laun, W.; Mohr, L.; Grimm, B.; Rix, H. -W.; Rohloff,
R. -R.; Soci, R.; Storz, C.; Xu, W.; Ragazzoni, R.; Salinari, P.;
Diolaiti, E.; Farinato, J.; Carbillet, M.; Schreiber, L.; Eckart,
A.; Bertram, T.; Straubmeier, C.; Wang, Y.; Zealouk, L.; Weigelt,
G.; Beckmann, U.; Behrend, J.; Driebe, T.; Heininger, M.; Hofmann,
K. -H.; Nußbaum, E.; Schertel, D.; Masciadri, E.
Bibcode: 2005CRPhy...6.1129G
Altcode:
LINC-NIRVANA is a Fizeau (imaging) interferometer exploiting the full
spatial resolution of a 23 m class telescope in the combined beam of the
Large Binocular Telescope supported through Multi-Conjugated Adaptive
Optics (MCAO). By means of science cases, we show how LINC-NIRVANA takes
advantage of the MCAO, increasing the sky coverage of the instrument
and the field of view for the Fringe and Flexure tracker. We introduce
the MCAO system of LINC-NIRVANA in detail, which in a first step will
be installed with two deformable mirrors per arm and has the provision
to be upgraded with a third mirror. The MCAO system implements several
novel concepts proposed for extremely large telescopes, such as layer
oriented MCAO, optical co-adding of guide stars, or Multiple Field
of View sensing. LINC-NIRVANA will demonstrate some of the concepts
for the first time on sky. To cite this article: W. Gaessler et. al.,
C. R. Physique 6 (2005).
Title: VizieR Online Data Catalog: UBVRI photometry and polarimetry
of DF Tau (Shakhovskoj+, 2006)
Authors: Shakhovskoj, D.; Grinin, V.; Rostopchina, A.; Schertl, D.;
Hofmann, K. -H.; Weigelt, G.; Balega, Yu.; Kiyaeva, O.; Melnikov, S.
Bibcode: 2005yCat..34481075S
Altcode:
Photometric and polarimetric observations of DF Tau were carried out
between 1991 and 1998 using the five-band photopolarimeter mounted
at the 1.25m telescope of the Crimean Astrophysical Observatory
(CrAO). This instrument permits simultaneous observations of
polarization and brightness in the U, B, V, R, and I bands. The
effective wavelengths of the instrumental system are close to the
standard wavelengths of the Johnson photometric system. (1
data file).
Title: Infrared emission from a clumpy and dusty torus around AGN.
Authors: Beckert, T.; Hoenig, S.; Duschl, W. J.; Weigelt, G.
Bibcode: 2005AN....326..536B
Altcode:
No abstract at ADS
Title: High-resolution near-infrared speckle interferometry and
radiative transfer modeling of the OH/IR star OH 26.5+0.6.
Authors: Driebe, T.; Riechers, D.; Balega, Y.; Hofmann, K. -H.;
Men'shchikov, A. B.; Weigelt, G.
Bibcode: 2005AN....326..648D
Altcode:
No abstract at ADS
Title: Mid-infrared spectro-interferometric observation of the Mira
variable RR Sco with the VLTI/MIDI instrument.
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Schertl, D.;
Weigelt, G.
Bibcode: 2005AN....326R.567O
Altcode:
No abstract at ADS
Title: Near-infrared Interferometry with the AMBER Instrument of
the VLTI.
Authors: Weigelt, G.; Beckert, T.; Beckmann, U.; Driebe, T.; Foy, R.;
Fraix-Burnet, D.; Hofmann, K. -H.; Kraus, S.; Malbet, F.; Mathias,
P.; Marconi, A.; Monin, J. -L.; Petrov, R.; Schertl, D.; Stee, P.;
Testi, L.
Bibcode: 2005AN....326..572W
Altcode:
No abstract at ADS
Title: Bispectrum speckle interferometry of the massive protostellar
outflow source IRAS 23151+5912.
Authors: Preibisch, T.; Beuther, H.; Hofmann, K. -H.; Meyer, M.;
Schertl, D.; Smith, M. D.; Weigelt, G.; Young, E. T.
Bibcode: 2005AN....326..570P
Altcode:
No abstract at ADS
Title: Mid-infrared long-baseline interferometry of the symbiotic
Mira star RX Pup with the VLTI/MIDI instrument.
Authors: Driebe, T.; Hofmann, K. -H.; Ohnaka, K.; Preibisch, T.;
Weigelt, G.; Wittkowski, M.
Bibcode: 2005AN....326..649D
Altcode:
No abstract at ADS
Title: High-Resolution near-infrared speckle interferometry and
radiative transfer modeling of the OH/IR star OH 104.9+2.4.
Authors: Riechers, D.; Driebe, T.; Balega, Y.; Hofmann, K. -H.;
Menshchikov, A. B.; Weigelt, G.
Bibcode: 2005AN....326R.666R
Altcode: 2005AN....326..666R
No abstract at ADS
Title: Infrared interferometry of the Seyfert galaxy NGC 1068.
Authors: Weigelt, G.; Balega, Y. Y.; Beckert, T.; Duschl, W. J.;
Hofmann, K. -H.; Men'shchikov, A. B.; Schertl, D.; Wittkowski, M.
Bibcode: 2005AN....326..558W
Altcode:
No abstract at ADS
Title: VLTI/MIDI observation of the silicate carbon star Hen 38
(IRAS 08002-3803): silicate dust reservoir spatially resolved for
the first time.
Authors: Ohnaka, K.; Driebe, T.; Hofmann, K. -H.; Schertl, D.;
Weigelt, G.
Bibcode: 2005AN....326Q.567O
Altcode:
No abstract at ADS
Title: Bispectrum speckle imaging of the ultracompact HII region
K3-50A.
Authors: Kraus, S.; Balega, Y. Y.; Hofmann, K. -H.; Preibisch, T.;
Weigelt, G.
Bibcode: 2005AN....326R.563K
Altcode:
No abstract at ADS
Title: A quasi-time-dependent radiative transfer model of OH 104.9+2.4
Authors: Riechers, D.; Balega, Y.; Driebe, T.; Hofmann, K. -H.;
Men'shchikov, A. B.; Shenavrin, V. I.; Weigelt, G.
Bibcode: 2005A&A...436..925R
Altcode: 2005astro.ph..2269R
We investigate the pulsation-phase dependent properties of
the circumstellar dust shell (CDS) of the OH/IR star OH
104.9+2.4 based on radiative transfer modeling (RTM) using the
code DUSTY. Our previous study concerning simultaneous modeling of the
spectral energy distribution (SED) and near-infrared (NIR) visibilities
(Riechers et al. 2004) has now been extended by means of a more detailed
analysis of the pulsation-phase dependence of the model parameters of
OH 104.9+2.4. In order to investigate the temporal
variation in the spatial structure of the CDS, additional NIR speckle
interferometric observations in the K' band were carried out with
the 6 m telescope of the Special Astrophysical Observatory (SAO). At a
wavelength of λ = 2.12 μm the diffraction-limited resolution of 74 mas
was attained. Several key parameters of our previous best-fitting model
had to be adjusted in order to be consistent with the newly extended
amount of observational data. It was found that a simple rescaling of
the bolometric flux F_bol is not sufficient to take the variability
of the source into account, as the change in optical depth τ over a
full pulsation cycle is rather high. On the other hand, the impact of a
change in effective temperature T_eff on SED and visibility is rather
small. However, observations, as well as models for other AGB stars,
show the necessity of including a variation of T_eff with pulsation
phase in the radiative transfer models. Therefore, our new best-fitting
model accounts for these changes.
Title: Eta Car through the eyes of interferometers
Authors: Chesneau, Olivier; Van Boekel, R.; Herbst, T.; Kervella,
P.; Min, M.; Waters, L. B. F. M.; Leinert, Ch.; Petrov, R.; Weigelt, G.
Bibcode: 2005astro.ph..6756C
Altcode:
The core of the nebula surrounding Eta Carinae has recently been
observed with VLT/NACO, VLTI/VINCI, VLTI/MIDI and VLTI/AMBER in order
to spatially and spectrally constrain the warm dusty environment and
the central object. Narrow-band images at 3.74 and 4.05 micron reveal
the structured butterfly-shaped dusty environment close to the central
star with an unprecedented spatial resolution of about 60 mas. VINCI
has resolved the present-day stellar wind of Eta Carinae on a scale of
several stellar radii owing to the spatial resolution of the order of
5 mas (11 AU). The VINCI observations show that the object is elongated
with a de-projected axis ratio of approximately 1.5. Moreover the major
axis is aligned with that of the large bipolar nebula that was ejected
in the 19th century. Fringes have also been obtained in the Mid-IR
with MIDI using baselines of 75m. A peak of correlated flux of 100
Jy is detected 0.3" south-east from the photocenter of the nebula at
8.7 micron is detected. This correlated flux is partly attributed to
the central object but it is worth noting that at these wavelengths,
virtually all the 0.5" x 0.5" central area can generate detectable
fringes witnessing the large clumping of the dusty ejecta. These
observations provide an upper limit for the SED of the central source
from 3.8 to 13.5 micron and constrain some parameters of the stellar
wind which can be compared to Hillier's model. Lastly, we present the
great potential of the AMBER instrument to study the numerous near-IR
emissive lines from the star and its close vicinity. In particular,
we discuss its ability to detect and follow the faint companion.
Title: Orbits of new Hipparcos binaries. I
Authors: Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.; Pluzhnik,
E. A.; Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2005A&A...433..591B
Altcode:
We present first orbits for 6 new Hipparcos binaries. The orbits were
determined from speckle interferometric measurements collected mainly
at the6m BTAtelescope of the Special Astrophysical Observatory
in Zelenchuk. Three of the systems, HIP 11352, HIP 14075
and HIP 14230, have late G- or early K-type components, while
HIP 14669 = GJ 125, HIP 106972 = GJ 4210 and HIP 111685 =
GJ 4287 have M-type components. The periods of the orbits are in
the range of6-28years. Mass sums and their errors are derived for the
systems. The Hipparcos parallax error is the dominating error source
of themass determination. Based on observations made with the
6-m BTA telescope, which is operated by the Special Astrophysical
Observatory, Russia.
Title: Mid-infrared interferometry of the Mira variable RR Sco with
the VLTI MIDI instrument
Authors: Driebe, T.; Ohnaka, K.; Weigelt, G.
Bibcode: 2005ESASP.560..351D
Altcode: 2005csss...13..351D
No abstract at ADS
Title: Atmospheric Elemental Abundances for the Components of the
Multiple System ADS 11061. 41 Draconis
Authors: Balega, Yu. Yu.; Leushin, V. V.; Weigelt, G.
Bibcode: 2005ARep...49..217B
Altcode:
We obtained speckle interferometric and spectroscopic observations
of the system 41 Dra during its periastron passage in 2001. The
components’ lines are resolved in the spectral interval 3700 9200
Å. The observed wavelength dependence of the brightness difference
between the components is used to estimate the B-V indices separately
for each of the components: B-V = 0.511 for component a and B-V =
0.502 for component b. We derived improved effective temperatures of
the components from their B-V values and hydrogen-line profiles. The
observations can be described with the parameters for the components T
eff a = 6370 K, log g a = 4.05 and T eff b = 6410 K, log g b = 4.20. The
iron, carbon, nitrogen, and oxygen abundances in the atmospheres of
the components are log N(Fe)a = 7.55, log N(Fe)b = 7.60, log N(C)a =
8.52, log N(C)b = 8.58, log N(N)a = 8.05, log N(N)b = 7.99, log N(O)a =
8.73, log N(O)b = 8.76.
Title: Interferometric observations of the Mira star o Ceti with
the VLTI/VINCI instrument in the near-infrared
Authors: Hofmann, K. -H.; Eberhardt, M.; Driebe, T.; Schertl, D.;
Scholz, M.; Schoeller, M.; Weigelt, G.; Wittkowski, M.; Woodruff, H. C.
Bibcode: 2005ESASP.560..651H
Altcode: 2005csss...13..651H
No abstract at ADS
Title: Close binary companions of the HAeBe stars LkHα 198, Elias 1,
HK Ori and V380 Ori
Authors: Smith, K. W.; Balega, Y. Y.; Duschl, W. J.; Hofmann, K. -H.;
Lachaume, R.; Preibisch, T.; Schertl, D.; Weigelt, G.
Bibcode: 2005A&A...431..307S
Altcode: 2004astro.ph.10449S
We present diffraction-limited bispectrum speckle interferometry
observations of four well-known Herbig Ae/Be (HAeBe) stars,
LkHα 198, Elias 1, HK
Ori and V380 Ori. For two of these,
LkHα 198 and Elias 1, we present the first unambiguous detection of
close companions. The plane of the orbit of the new LkHα 198 companion
appears to be significantly inclined to the plane of the circumprimary
disk, as inferred from the orientation of the outflow. We show that
the Elias 1 companion may be a convective star, and suggest that
it could therefore be the true origin of the X-ray emission from
this object. In the cases of HK Ori and V380 Ori, we present new
measurements of the relative positions of already-known companions,
indicating orbital motion. For HK Ori, photometric measurements of
the brightness of the individual components in four bands allowed us
to decompose the system spectral energy distribution (SED) into the
two separate component SEDs. The primary exhibits a strong infrared
excess which suggests the presence of circumstellar material, whereas
the companion can be modelled as a naked photosphere. The infrared
excess of HK Ori A was found to contribute around two thirds of the
total emission from this component, suggesting that accretion power
contributes significantly to the flux. Submillimetre constraints mean
that the circumstellar disk cannot be particularly massive, whilst
the near-infrared data indicates a high accretion rate. Either the
disk lifetime is very short, or the disk must be seen in an outburst
phase. Based on observations performed with the 6 m telescope
of the Special Astrophysical Observatory, Russia, the 2.2 m ESO/MPG
telescope at La Silla, and with the NASA/ESA Hubble Space Telescope,
obtained from the data archive at the Space Telescope Institute. STScI
is operated by the association of Universities for Research in
Astronomy, Inc. under the NASA contract NAS 5-26555.
Title: Mid-infrared interferometry of the Mira variable RR Sco with
the VLTI MIDI instrument
Authors: Ohnaka, K.; Bergeat, J.; Driebe, T.; Graser, U.; Hofmann,
K. -H.; Köhler, R.; Leinert, Ch.; Lopez, B.; Malbet, F.; Morel, S.;
Paresce, F.; Perrin, G.; Preibisch, Th.; Richichi, A.; Schertl, D.;
Schöller, M.; Sol, H.; Weigelt, G.; Wittkowski, M.
Bibcode: 2005A&A...429.1057O
Altcode:
We present the results of the first mid-infrared interferometric
observations of the Mira variable RR Sco with the MID-infrared
Interferometer (MIDI) coupled to the European Southern Observatory's
(ESO) Very Large Telescope Interferometer (VLTI), together with
K-band observations using VLTI VINCI. The observations were carried
out in June 2003, when the variability phase of the object was 0.6,
using two unit telescopes (UT1 and UT3), as part of the Science
Demonstration Time (SDT) program of the instrument. Projected baseline
lengths ranged from 73 to 102 m, and a spectral resolution of 30 was
employed in the observations, which enabled us to obtain the wavelength
dependence of the visibility in the region between 8 and 13 μm. The
uniform-disk diameter was found to be 18 mas between 8 and 10 μm,
while it gradually increases at wavelengths longer than 10 μm to
reach 24 mas at 13 μm. The uniform-disk diameter between 8 and 13
μm is significantly larger than the K-band uniform-disk diameter
of 10.2 ± 0.5 mas measured using VLTI VINCI with projected baseline
lengths of 15-16 m, three weeks after the MIDI observations. Our model
calculations show that optically thick emission from a warm molecular
envelope consisting of H2O and SiO can cause the apparent mid
-infrared diameter to be much larger than the continuum diameter. We
find that the warm molecular envelope model extending to ∼2.3
R\star with a temperature of ∼1400 K and column densities
of H2O and SiO of 3 × 1021 cm-2 and
1 × 1020 cm-2, respectively, can reproduce the
observed uniform-disk diameters between 8 and 10 μm. The observed
increase of the uniform-disk diameter longward of 10 μm can be
explained by an optically thin dust shell consisting of silicate and
corundum grains. The inner radius of the optically thin dust shell is
derived to be 7-8 R\star with a temperature of ∼700 K,
and the optical depth at 10 μm is found to be ∼0.025. Based
on observations made with the Very Large Telescope Interferometer of
the European Southern Observatory.
Title: Near-infrared interferometry of AGN
Authors: Weigelt, G.; Beckert, T.; Hofmann, K. -H.; Schertl, D.;
Wittkowski, M.
Bibcode: 2005MmSAI..76...39W
Altcode:
Interferometry in the infrared is able to resolve the sub-parsec-scale
dust environment surrounding the accretion disk of AGN. A
diffraction-limited K'-band image of NGC 1068 with 74 mas resolution
and the first H-band image with 57 mas resolution were reconstructed
from speckle interferograms obtained with the SAO 6 m telescope. The
resolved structure consists of a compact core and an extended northern
and south-eastern component. The compact core has a north-western,
tail-shaped extension. The K'-band FWHM diameter of this compact core is
approximately 18 × 39 mas (± 4 mas) or 1.3 × 2.8 pc, and the position
angle (PA) of the north-western extension is -16o. The
PA of -16o is similar to that of the western wall of the
ionization cone. This suggests that the H- and K'-band emission from
the compact core is both thermal emission and scattered light from
dust near the western wall of a low-density, conical outflow cavity
or from the innermost region of a parsec-scale dusty torus. The first
K-band long-baseline interferometry of the nucleus of NGC 1068 with
resolution lambda /B ∼ 10 mas was obtained with the ESO VLTI. A
squared visibility amplitude of 16 ± 4% was measured at a baseline of
46 m. Taking into account K-band speckle interferometry observations,
the VLTI observations suggest a multi-component structure, where part
of the flux originates from scales clearly smaller than ∼ 5 mas or
0.4 pc. Based on public commissioning data released from the VLTI
and data collected at the SAO 6 m telescope in Russia.
Title: Modelling a Circumstellar Disc Traced by Methanol Masers
Authors: Pestalozzi, M. R.; Elitzur, M.; Minier, V.; Conway, J.;
Booth, R.; de Buizer, J.; Weigelt, G.
Bibcode: 2005prpl.conf.8129P
Altcode: 2005LPICo1286.8129P
No abstract at ADS
Title: MWC297: Disk and Wind Spatially Resolved with VLTI/AMBER
Authors: Benisty, M.; Malbet, F.; de Wit, W. J.; Kraus, S.; Meilland,
A.; Millour, F.; Tatulli, E.; Berger, J. -P.; Chesneau, O.; Hofmann,
K. -H.; Isella, A.; Petrov, R.; Preisbich, T.; Stee, P.; Testi, L.;
Weigelt, G.; AMBER Consortium
Bibcode: 2005prpl.conf.8395B
Altcode: 2005LPICo1286.8395B
No abstract at ADS
Title: Outflow Structures from the Young High-Mass Star NGC 7538
IRS1 Revealed by Near-Infrared Bispectrum Speckle Interferometry
Authors: Kraus, S.; Hofmann, K. -H.; Preibisch, Th.; Schertl, D.;
Weigelt, G.; Elitzur, M.; Pestalozzi, M. R.; Meyer, M.; Young, E. T.
Bibcode: 2005prpl.conf.8335K
Altcode: 2005LPICo1286.8335K
No abstract at ADS
Title: Recombining light of the VLTI at 10 microns by densifying
the images
Authors: Dugue, Michel; Lopez, Bruno; Przygodda, Frank; Graser, Uwe;
Gitton, Philippe B.; Wolf, Sebastian; Mathias, Philippe; Antonelli,
Pierre; Augereau, J. C.; Berruyer, Nicole; Bresson, Yves; Chesneau,
Olivier; Dutrey, Anne; Flament, Sebastien; Glazenborg-Kluttig, Annelie
W.; Glindemann, Andreas; Henning, Thomas; Hofmann, Karl-Heinz; Lagarde,
Stephane; Hugues, Yves; Leinert, Christoph; Meisenheimer, Klaus;
Menut, Jean-Luc; Rohloff, Ralf-Rainer; Roussel, Alain; Thiebaut,
Eric M.; Weigelt, Gerd P.
Bibcode: 2004SPIE.5491.1536D
Altcode:
APreS-MIDI (APerture Synthesis in the MID-Infrared) instrument function
is to recombine 4 telescope beams of the VLTI. Interference fringes
are sampled in the pupil plane. The optical principle uses "image
densification". It is perfectly adapted for reconstructing images by
aperture synthesis at 10mm. This principle could be used for building
a new generation 10mm instrument, but instead of making a totally new
instrument, we propose the design of an optical module that can supply
the current MIDI-VLTI instrument with 4 beams.
Title: Diffraction-limited bispectrum speckle interferometry of the
nuclear region of the Seyfert galaxy NGC 1068
in the H and K' bands
Authors: Weigelt, G.; Wittkowski, M.; Balega, Y. Y.; Beckert, T.;
Duschl, W. J.; Hofmann, K. -H.; Men'shchikov, A. B.; Schertl, D.
Bibcode: 2004A&A...425...77W
Altcode:
We present near-infrared bispectrum speckle interferometry
studies of the nuclear region of the Seyfert 2 galaxy NGC
1068. A diffraction-limited K'-band image with 74 mas
resolution and the first H-band image with 57 mas resolution were
reconstructed from speckle interferograms obtained with the SAO 6 m
telescope. The resolved structure consists of a compact core and an
extended northern and south-eastern component. The compact core is
resolved at all position angles and has a north-western, tail-shaped
extension as well as a fainter, south-eastern extension. The K'-band
FWHM diameter of this compact core is approximately 18 × 39 mas or
1.3 × 2.8 pc (FWHM of a single-component Gaussian fit; fit range
30-80&%slash; of the telescope cut-off frequency; the diameter
errors are ±4 mas), and the position angle (PA) of the north-western
extension is -16 ± 4 °. If 40% of the flux from the compact K' core
is emission from a point source and 60% from a Gaussian intensity
distribution, then a slightly larger FWHM of approximately 26 × 58
mas is obtained for the compact K' component. In the H band, the FWHM
diameter of the compact core is approximately 18 × 45 mas (±4 mas),
and the PA is -18 ± 4 °. The extended northern component (PA ∼ 0
°) has an elongated structure with a length of about 400 mas or 29
pc. The extended south-eastern component is fainter than the northern
component. The K'- and H-band fluxes from the resolved compact core
were measured to be 350 ± 90 mJy (i.e., K' ∼ 8.2m) and
70 ± 20 mJy (H ∼ 10.4m), respectively. The PA of -16 ±
4 ° of the compact 18 × 39 mas core is very similar to that of the
western wall (PA ∼ -15 °) of the bright region of the ionization
cone. This suggests that the H- and K'-band emission from the compact
core is both thermal emission and scattered light from dust near the
western wall of a low-density, conical cavity or from the innermost
region of a parsec-scale dusty torus that is heated by the central
source (the dust sublimation radius of NGC 1068
is approximately 0.1-1 pc). The northern extended 400 mas structure
lies near the western wall of the ionization cone and coincides with
the inner radio jet (PA ∼ 11 °). The large distance from the core
suggests that the K'-band emission of the northern extended component
is scattered light from the western cavity region and the radio jet
region. Based on observations made with the 6 m BTA telescope,
which is operated by the Special Astrophysical Observatory (SAO),
Russia.
Title: APreS-MIDI, APerture Synthesis in the MID-infrared with
the VLTI
Authors: Lopez, Bruno; Przygodda, Frank; Wolf, Sebastian; Dugue,
Michel; Graser, Uwe; Gitton, Philippe B.; Mathias, Philippe; Antonelli,
Pierre; Augereau, J. C.; Berruyer, Nicole; Bresson, Yves; Chesneau,
Olivier; Dutrey, Anne; Flament, Sebastien; Glazenborg, Annelie;
Glindemann, Andreas; Henning, Thomas; Hofmann, Karl-Heinz; Hugues,
Yves; Lagarde, Stephane; Leinert, Christoph; Meisenheimer, Klaus;
Menut, Jean-Luc; Rohloff, Ralf-Rainer; Roussel, Alain; Thiebaut,
Eric M.; Weigelt, Gerd P.
Bibcode: 2004SPIE.5491..433L
Altcode:
We are studying an optical concept aiming at recombining four
mid-infrared telescope beams, where interference fringes are
sampled in the pupil plane. Such a principle is perfectly adapted
for reconstructing images by aperture synthesis with teh VLTI. It
could be used for building a new generation 10 μm instrument, but
instead of doing a totally new instrument, we propose the design of
an optical module that can supply the surrent MIDI-VLTI instrument
with 4 beams. The combined use of this module together with the MIDI
instrument is the project called APreS-MIDI. Such an instrument at the
VLTI focus will have an unique and very strong astrophysical potential.
Title: The fringe and flexure tracking detector of the LBT
LINC-NIRVANA beam-combiner instrument
Authors: Beckmann, Udo; Behrend, Jan; Bohnhardt, Hermann; Connot,
Claus; Driebe, Thomas M.; Heininger, Matthias; Herbst, Thomas M.;
Hofmann, Karl-Heinz; Nussbaum, Edmund; Schertl, Dieter; Solscheid,
Walter; Straubmeier, Christian; Weigelt, Gerd P.
Bibcode: 2004SPIE.5491.1445B
Altcode:
LINC-NIRVANA is a near-infrared (1-2.4 micron) beam-combiner instrument
for the Large Binocular Telescope (LBT). LINC-NIRVANA is being built
by a consortium of groups at the Max-Planck-Institut fur Astronomie in
Heidelberg, the Osservatorio Astrofisico di Arcetri in Florence, the
Universitat zu Koln, and the Max-Planck-Institut fur Radioastronomie in
Bonn. The MPI fur Radioastronomie is responsible for the near-infrared
detector for the fringe and flexure tracking system (FFTS). We describe
the design and construction of the detector control electronics as
well as the first laboratory measurements of performance parameters
of the NIR detector for the fringe and flexure tracking system of
the LBT LINC-NIRVANA instrument. This detector has to record LBT
interferograms of suitable reference stars in the FOV at a frame
rate of the order of 200 frames per second using, for example, 32
× 32-pixel subframes. Moreover, special noise reduction techniques
have to be applied. The fringe-tracker interferograms are required
for monitoring and closed-loop correction of the atmospheric optical
path difference of the two LBT wavefronts (see C. Straubmeier et al.,
"A fringe and flexure tracking system for LINC-NIRVANA: basic design and
principle of operation"). We will describe our laboratory measurements
of maximum frame rate, readout noise, photometric stability, and other
important parameters together with first measurements of laboratory
simulations of LBT interferograms.
Title: Interferometric observations of the Mira star o Ceti with
the VLTI/VINCI instrument in the near-infrared
Authors: Woodruff, Henry C.; Eberhardt, Maren; Driebe, Thomas M.;
Hofmann, Karl-Heinz; Ohnaka, Keiichi; Richichi, Andrea; Schertl,
Dieter; Schoeller, Markus; Scholz, Michael; Weigelt, Gerd P.;
Wittkowski, Markus; Wood, Peter R.
Bibcode: 2004SPIE.5491.1707W
Altcode:
We present K-band commissioning observations of the Mira star prototype
o Cet obtained at the ESO Very Large Telescope Interferometer (VLTI)
with the VINCI instrument and two siderostats. The observations were
carried out between 2001 October and December, in 2002 January and
December, and in 2003 January. Rosseland angular radii are derived from
the measured visibilities by fitting theoretical visibility functions
obtained from center-to-limb intensity variations (CLVs) of Mira star
models. Using the derived Rosseland angular radii and the spectral
energy distributions (SEDs) reconstructed from available photometric
and spectrophotometric data, we find effective temperatures ranging
from T_eff=3192 +/- 200 K at phase 0.13 to 2918 +/- 183 K at phase
0.26. Comparison of these Rosseland radii, effective temperatures, and
the shape of the observed visibility functions with model predictions
suggests that o Cet is a fundamental mode pulsator. Furthermore, we
investigated the variation of visibility function and diameter with
phase. The Rosseland angular diameter of o Cet increased from 28.9 +/-
0.3 mas (corresponding to a Rosseland radius of 332 +/- 38 Rsun for a
distance of D=107 +/- 12 pc) at phase 0.13 to 34.9 +/- 0.4 mas (402
+/- 46 Rsun) at phase 0.4. The observational error of the Rosseland
linear radius almost entirely results from the error of the parallax,
since the error of the angular diameter is only approximately 1%.
Title: The fringe and flexure tracking system for LINC-NIRVANA:
basic design and principle of operation
Authors: Straubmeier, Christian; Bertram, Thomas; Eckart, Andreas;
Wang, Yibing; Zealouk, Lahbib; Herbst, Thomas M.; Andersen, David R.;
Ragazzoni, Roberto; Weigelt, Gerd P.
Bibcode: 2004SPIE.5491.1486S
Altcode:
LINC-NIRVANA is the interferometric near-infrared imaging camera
for the Large Binocular Telescope (LBT). Operating at JHK bands
LINC-NIRVANA will provide an unique and unprecedented combination of
high angular resolution (~9 milliarcseconds at 1.25 μm), wide field of
view (~100 arcseconds2 at 1.25 μm), and large collecting area (~100
m2). One of the major contributions of the I. Physikalische Institut
of the University of Cologne to this project is the development of the
Fringe and Flexure Tracking System (FFTS). In close cooperation with
the Adaptive Optics systems of LINC-NIRVANA the FFTS is a fundamental
component to ensure a complete and time-stable wavefront correction
at the position of the science detector in order to allow for long
integration times at interferometric angular resolutions. Using a
dedicated near-infrared detector array at a combined focus close to
the science detector, the Fringe and Flexure Tracking System analyses
the interferometric point spread function (PSF) of a suitably bright
reference source at frame rates of several hundred Hertz up to 1 kHz. By
fitting a parameterized theoretical model PSF to the preprocessed
image-data the FFTS determines the amount of pistonic phase difference
and the amount of an angular misalignment between the wavefronts of the
two optical paths of LINC-NIRVANA. For every exposure the correcting
parameters are derived in real-time and transmitted to the respective
control electronics, or the Adaptive Optics systems of the single-eye
telescopes, which will adjust their optical elements accordingly. In
this paper we present the opto-mechanical hardware design, the
principle of operation of the software control algorithms, and the
results of first numerical simulations and laboratory experiments of
the performance of this Fringe and Flexure Tracking System.
Title: High-resolution near-infrared speckle interferometry and
radiative transfer modeling of the OH/IR star OH 104.9+2.4
Authors: Riechers, Dominik; Balega, Yuri Y.; Driebe, Thomas M.;
Hofmann, Karl-Heinz; Men'shchikov, Alexander B.; Schertl, Dieter;
Weigelt, Gerd P.
Bibcode: 2004SPIE.5491.1714R
Altcode:
We present near-infrared speckle interferometry of the OH/IR star
OH 104.9+2.4 in the K' band obtained with the 6m telescope of the
Special Astrophysical Observatory (SAO). At a wavelength of λ = 2.12
micron the diffraction-limited resolution of 74 mas was attained. The
reconstructed visibility reveals a spherically symmetric, circumstellar
dust shell (CDS) surrounding the central star. The visibility function
shows that the stellar contribution to the total flux at λ = 2.12
micron is less than 50%, indicating a rather large optical depth of
the CDS. The azimuthally averaged 1-dimensional Gaussian visibility
fit yields a diameter of 47 +/- 3 mas (FHWM), which corresponds
to 112 +/- 13 AU for an adopted distance of D = 2.38 + 0.24 kpc. To
determine the structure and the properties of the CDS of OH 104.9+2.4,
radiative transfer calculations using the code DUSTY were performed to
simultaneously model its visibility and the spectral energy distribution
(SED). We found that both the ISO spectrum and the visibility of OH
104.9+2.4 can be well reproduced by a radiative transfer model with an
effective temperature Teff = 2500 +/- 500 K of the central source, a
dust temperature Tin = 1000 +/- 200 K at the inner shell boundary Rin =
9.1 Rstar = 25.4 AU, an optical depth tau = 6.5 +/- 0.3 at 2.2 micron,
and dust grain radii ranging from amin = 0.005 +/- 0.003 micron to
amax = 0.2 +/- 0.02 micron with a power law with index -3.5. It was
found that even minor changes in amax have a major impact on both the
slope and the curvature of the visibility function, while the SED shows
only minor changes. Our detailed analysis demonstrates the potential
of dust shell modeling constrained by both the SED and visibilities.
Title: The VLTI focal instrument Amber: results of the first phase
of the alignment, integration, and verification in Paranal
Authors: Robbe-Dubois, Sylvie; Petrov, Romain G.; Lagarde, Stephane;
Antonelli, Pierre; Bresson, Yves; Roussel, Alain; Mourard, Denis;
Malbet, Fabien; Millour, Florentin; Zins, Gerard; Delboulbe, Alain;
Duvert, Gilles; Gluck, Laurence; Kern, Pierre Y.; Le Coarer, Etienne
P.; Rousselet-Perraut, Karine; Tatulli, Eric; Beckmann, Udo; Heininger,
Matthias; Weigelt, Gerd P.; Lisi, Franco; Stefanini, Paolo; Accardo,
Matteo; Gil, Carla S.; Vannier, Martin; Haddad, Nicholas; Housen,
Nico; Kiekebusch, Mario; Mardones, Pedro; Puech, Florence; Rantakyro,
Fredrik T.; Richichi, Andrea; Schoeller, Markus
Bibcode: 2004SPIE.5491.1089R
Altcode:
AMBER, Astronomical Multi BEam combineR, is the near-infrared focal
instrument dedicated to the VLTI. It is designed to combine three
of the VLTI Telescopes and to work simultaneously in the J, H and K
spectral bands (1.0 to 2.4 μm). The project successfully passed the
Preliminary Acceptance in Europe in November 2003, resulting in the
validation of the instrument laboratory performance1, of the compliance
with the initial scientific specifications, and of the acceptance of
ESO for AMBER to be part of the VLTI. After the transportation of the
instrument to Paranal, Chile in January 2004, the Assembly Integration
and Verification phase occurred mid-March to succeed with the first
fringes observing bright stars with the VLTI siderostats. This paper
describes the different steps of the AIV and the first results in terms
of instrumental stability, estimated visibility and differential phase.
Title: Science program of the AMBER consortium
Authors: Malbet, Fabien; Driebe, Thomas M.; Foy, Renaud; Fraix-Burnet,
Didier; Mathias, Philippe; Marconi, Alessandro; Monin, Jean-Louis;
Petrov, Romain G.; Stee, Philippe; Testi, Leonardo; Weigelt, Gerd P.
Bibcode: 2004SPIE.5491.1722M
Altcode:
AMBER had first light in March 2004. The guaranteed time observations
of the AMBER consortium (LAOG, MPIfR, OAA, OCA, UNSA) consists of
87 proposals ranging from cosmology, extragalactic studies, star
formation, planetary system, late stages of stellar evolution to
physical properties of stars. Some examples, AGN, evolved stars and
hot stars are discussed in this paper.
Title: LINC-NIRVANA: the single arm MCAO experiment
Authors: Egner, Sebastian E.; Gaessler, Wolfgang; Herbst, Tom M.;
Ragazzoni, Roberto; Stuik, Remko; Andersen, D. A.; Arcidiacono, C.;
Baumeister, H.; Beckmann, U.; Behrend, J.; Bertram, T.; Bizenberger,
P.; Boehnhardt, H.; Diolaiti, E.; Driebe, T.; Eckhardt, A.; Farinato,
J.; Kuerster, M.; Laun, W.; Ligori, S.; Naranjo, Vianak; Nußbaum, E.;
Rix, H. -W.; Rohloff, R. -R.; Salinari, Piero; Soci, R.; Straubmeier,
C.; Vernet-Viard, E.; Weigelt, Gerd P.; Weiss, R.; Xu, W.
Bibcode: 2004SPIE.5490..924E
Altcode:
LINC-NIRVANA is an imaging interferometer for the Large Binocular
Telescope (LBT) and will make use of multi-conjugated adaptive
optics (MCAO) with two 349 actuators deformable mirrors (DM), two
672 actuator deformable secondary mirrors and a total of 4 wavefront
sensors (WFS) by using 8 or 12 natural guide stars each. The goal of
the MCAO is to increase sky coverage and achieve a medium Strehl-ratio
over the 2 arcmin field of view. To test the concepts and prototypes,
a laboratory setup of one MCAO arm is being built. We present the layout
of the MCAO prototype, planned and accomplished tests, especially for
the used Xinetics DMs, and a possible setup for a test on sky with an
existing 8m class telescope.
Title: LINC-NIRVANA: how to get a 23-m wavefront nearly flat
Authors: Gaessler, Wolfgang; Ragazzoni, Roberto; Herbst, Thomas
M.; Andersen, David R.; Arcidiacono, Carmelo; Baumeister, Harald;
Beckmann, Udo; Behrend, Jan; Bertram, Thomas; Bizenberger, Peter;
Bohnhardt, Hermann; Briegel, F.; Diolaiti, Emiliano; Driebe, Thomas
M.; Eckhardt, A.; Egner, Sebastian E.; Farinato, Jacopo; Heininger,
Matthias; Kürster, M.; Laun, Werner; Ligori, Sebastiano; Naranjo,
Vianak; Nussbaum, Edmund; Rix, Hans-Walter; Rohloff, Ralf-Rainer;
Salinari, Piero; Soci, Roberto; Storz, Clemens; Straubmeier, Christian;
Vernet-Viard, Elise; Weigelt, Gerd P.; Weiss, Robert; Xu, Wenli
Bibcode: 2004SPIE.5490..527G
Altcode:
On the way to the Extremely Large Telescopes (ELT) the Large Binocular
Telescope (LBT) is an intermediate step. The two 8.4m mirrors create a
masked aperture of 23m. LINC-NIRVANA is an instrument taking advantage
of this opportunity. It will get, by means of Multi-Conjugated
Adaptive Optics (MCAO), a moderate Strehl Ratio over a 2 arcmin field
of view, which is used for Fizeau (imaging) interferometry in J,H
and K. Several MCAO concepts, which are proposed for ELTs, will be
proven with this instrument. Studies of sub-systems are done in the
laboratory and the option to test them on sky are kept open. We will
show the implementation of the MCAO concepts and control aspects of
the instrument and present the road map to the final installation at
LBT. Major milestones of LINC-NIRVANA, like preliminary design review
or final design review are already done or in preparation. LINC-NIRVANA
is one of the few MCAO instruments in the world which will see first
light and go into operation within the next years.
Title: High-resolution near-infrared speckle interferometry and
radiative transfer modeling of the OH/IR star OH 104.9+2.4
Authors: Riechers, D.; Balega, Y.; Driebe, T.; Hofmann, K. -H.;
Men'shchikov, A. B.; Weigelt, G.
Bibcode: 2004A&A...424..165R
Altcode: 2004astro.ph..6092R
We present near-infrared speckle interferometry of the OH/IR star
OH 104.9+2.4 in the K' band obtained with the
6 m telescope of the Special Astrophysical Observatory (SAO). At a
wavelength of λ = 2.12 μm the diffraction-limited resolution of 74
mas was attained. The reconstructed visibility reveals a spherically
symmetric, circumstellar dust shell (CDS) surrounding the central
star. The visibility function shows that the stellar contribution to
the total flux at λ = 2.12 μm is less than ∼50%, indicating a rather
large optical depth of the CDS. The azimuthally averaged 1-dimensional
Gaussian visibility fit yields a diameter of 47 ± 3 mas (FHWM), which
corresponds to 112 ± 13 AU for an adopted distance of D = 2.38 ±
0.24 kpc. To determine the structure and the properties of the CDS of
OH 104.9+2.4, radiative transfer calculations using
the code DUSTY were performed to simultaneously model its visibility
and the spectral energy distribution (SED). We found that both the
ISO spectrum and the visibility of OH 104.9+2.4
can be well reproduced by a radiative transfer model with an effective
temperature Teff = 2500 ± 500 K of the central source,
a dust temperature Tin = 1000 ± 200 K at the inner shell
boundary Rin ≃ 9.1 R* = 25.4 AU, an optical
depth τ2.2 μm = 6.5 ± 0.3, and dust g rain radii ranging
from amin = 0.005 ± 0.003 μm to amax = 0.2
± 0.02 μm with a power law n(a) ∝ a-3.5. It was found
that even minor changes in amax have a major impact on
both the slope and the curvature of the visibility function, while
the SED shows only minor changes. Our detailed analysis demonstrates
the potential of dust shell modeling constrained by both the SED and
visibilities. Based on data collected at the 6 m BTA telescope
of the Special Astrophysical Observatory in Russia.
Title: UML modeling of the LINC-NIRVANA control software
Authors: Gaessler, Wolfgang; Bertram, Thomas; Briegel, F.; Driebe,
Thomas M.; Heininger, Matthias; Nussbaum, Edmund; Storz, Clemens;
Wang, J.; Zealouk, Lahbib; Herbst, Thomas M.; Ragazzoni, Roberto;
Eckhardt, A.; Weigelt, Gerd P.
Bibcode: 2004SPIE.5496...79G
Altcode:
LINC-NIRVANA is a Fizeau interferometer for the Large Binocular
Telescope (LBT) doing imaging in the near infrared (J,H,K -
band). Multi-conjugated adaptive optics is used to increase sky
coverage and to get diffraction limited images over a 2 arcminute
field of view. The control system consists of five independent loops,
which are mediated through a master control. Due to the configuration,
LINC-NIRVANA has no delay line like other interferometers. To remove
residual atmospheric piston, the system must control both the primary
and secondary mirrors, in addition to a third, dedicated piston
mirror. This leads to a complex and interlocked control scheme and
software. We will present parts of the instrument software design,
which was developed in an object-oriented manner using UML. Several
diagram types were used to structure the overall system and to evaluate
the needs and interfaces of each sub-system to each other.
Title: The LINC-NIRVANA interferometric imager for the Large
Binocular Telescope
Authors: Herbst, Tom M.; Ragazzoni, Roberto; Eckart, Andreas;
Weigelt, Gerd
Bibcode: 2004SPIE.5492.1045H
Altcode:
We describe LINC-NIRVANA, a 1-2.5 micron interferometric imaging
instrument for the Large Binocular Telescope. Operating in Fizeau
beam combination mode, LINC-NIRVANA will deliver the sensitivity
of a 12-meter telescope and the angular resolution of a 23-meter
telescope. Unlike traditional interferometers, LINC-NIRVANA will
be a true imaging device, with a field of view of ten arcseconds on
a single HAWAII-2 detector array. LINC-NIRVANA employs a number of
state-of-the-art technologies, including multi-conjugated adaptive
optics (MCAO), innovative cooling systems, and complex software for
instrument control and data analysis. We report on overall project
progress and highlight some unique aspects of LINC-NIRVANA that should
be of wider interest to the near-infrared instrument-building community.
Title: Speckle interferometry of nearby multiple stars. II.
Authors: Balega, I.; Balega, Y. Y.; Maksimov, A. F.; Pluzhnik, E. A.;
Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2004A&A...422..627B
Altcode:
This paper is a continuation of diffraction-limited speckle
interferometry of binary and multiple stars carried out at the 6-m
telescope of the Special Astrophysical Observatory in Zelenchuk. The
program has concentrated on nearby (π>10 mas) close binaries
discovered or measured during the Hipparcos mission. Here, we present
132 measurements of relative positions and magnitude differences for 99
pairs and 8 measurements for 6 triple systems. 54 entries in the paper
are new Hipparcos binaries. New triple systems with late-type dwarf
components, discovered in the course of observations, are HIP 8533 and
HIP 25354. Based on data collected at the Special Astrophysical
Observatory, Russia. {Tables 1-3 are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/422/627
Title: Mid-infrared sizes of circumstellar disks around Herbig Ae/Be
stars measured with MIDI on the VLTI
Authors: Leinert, Ch.; van Boekel, R.; Waters, L. B. F. M.; Chesneau,
O.; Malbet, F.; Köhler, R.; Jaffe, W.; Ratzka, Th.; Dutrey, A.;
Preibisch, Th.; Graser, U.; Bakker, E.; Chagnon, G.; Cotton, W. D.;
Dominik, C.; Dullemond, C. P.; Glazenborg-Kluttig, A. W.; Glindemann,
A.; Henning, Th.; Hofmann, K. -H.; de Jong, J.; Lenzen, R.; Ligori, S.;
Lopez, B.; Meisner, J.; Morel, S.; Paresce, F.; Pel, J. -W.; Percheron,
I.; Perrin, G.; Przygodda, F.; Richichi, A.; Schöller, M.; Schuller,
P.; Stecklum, B.; van den Ancker, M. E.; von der Lühe, O.; Weigelt, G.
Bibcode: 2004A&A...423..537L
Altcode:
We present the first long baseline mid-infrared interferometric
observations of the circumstellar disks surrounding Herbig Ae/Be
stars. The observations were obtained using the mid-infrared
interferometric instrument MIDI at the European Southern Observatory
(ESO) Very Large Telescope Interferometer VLTI on Cerro Paranal. The
102 m baseline given by the telescopes UT1 and UT3 was employed,
which provides a maximum full spatial resolution of 20 milli-arcsec
(mas) at a wavelength of 10 μm. The interferometric signal was
spectrally dispersed at a resolution of 30, giving spectrally
resolved visibility information from 8 μm to 13.5 μm. We observed
seven nearby Herbig Ae/Be stars and resolved all objects. The warm
dust disk of HD 100546 could even be resolved in single-telescope
imaging. Characteristic dimensions of the emitting regions at 10 μm
are found to be from 1 AU to 10 AU. The 10 μm sizes of our sample
stars correlate with the slope of the 10-25 μm infrared spectrum
in the sense that the reddest objects are the largest ones. Such a
correlation would be consistent with a different geometry in terms
of flaring or flat (self-shadowed) disks for sources with strong or
moderate mid-infrared excess, respectively. We compare the observed
spectrally resolved visibilities with predictions based on existing
models of passive centrally irradiated hydrostatic disks made to fit
the SEDs of the observed stars. We find broad qualitative agreement
of the spectral shape of visibilities corresponding to these models
with our observations. Quantitatively, there are discrepancies that
show the need for a next step in modelling of circumstellar disks,
satisfying both the spatial constraints such as are now available
from the MIDI observations and the flux constraints from the SEDs in
a consistent way. Based on observations made with the Very Large
Telescope Interferometer at Paranal Observatory.
Title: Bipolar outflow on the asymptotic giant branch - the case
of IRC+10011
Authors: Vinković, Dejan; Blöcker, Thomas; Hofmann, Karl-Heinz;
Elitzur, Moshe; Weigelt, Gerd
Bibcode: 2004MNRAS.352..852V
Altcode: 2004astro.ph..5169V; 2004MNRAS.tmp..153V
Near-infrared imaging of the asymptotic giant branch (AGB) star
IRC+10011 (= CIT3) reveals the presence of a bipolar structure within
the central ~0.1 arcsec of a spherical dusty wind. We show that the
image asymmetries originate from ~10-4 Msolar
of swept-up wind material in an elongated cocoon whose expansion
is driven by bipolar jets. We perform detailed 2D radiative transfer
calculations with the cocoon modelled as two cones extending to ~1100 au
within an opening angle of ~30°, embedded in a wind with the standard
r-2 density profile. The cocoon expansion started <~200
yr ago, while the total lifetime of the circumstellar shell is ~5500
yr. Similar bipolar expansion, at various stages of evolution, has
been recently observed in a number of other AGB stars, culminating in
jet breakout from the confining spherical wind. The bipolar outflow is
triggered at a late stage in the evolution of AGB winds, and IRC+10011
provides its earliest example thus far. These new developments enable
us to identify the first instance of symmetry breaking in the evolution
from AGB to planetary nebula.
Title: Interferometric observations of the Mira star o Ceti with
the VLTI/VINCI instrument in the near-infrared
Authors: Woodruff, H. C.; Eberhardt, M.; Driebe, T.; Hofmann, K. -H.;
Ohnaka, K.; Richichi, A.; Schertl, D.; Schöller, M.; Scholz, M.;
Weigelt, G.; Wittkowski, M.; Wood, P. R.
Bibcode: 2004A&A...421..703W
Altcode: 2004astro.ph..4248W
We present K-band commissioning observations of the Mira star prototype
o Cet obtained at the ESO Very Large Telescope Interferometer (VLTI)
with the VINCI instrument and two siderostats. The observations were
carried out between 2001 October and December, in 2002 January and
December, and in 2003 January. Rosseland angular radii are derived
from the measured visibilities by fitting theoretical visibility
functions obtained from center-to-limb intensity variations (CLVs)
of Mira star models \citep{BSW,HSW,TLSW}. Using the derived Rosseland
angular radii and the SEDs reconstructed from available photometric
and spectrophotometric data, we find effective temperatures ranging
from Teff=3192 ± 200 K at phase Φ=0.13 to 2918 ±
183 K at Φ=0.26. Comparison of these Rosseland radii, effective
temperatures, and the shape of the observed visibility functions
with model predictions suggests that o Cet is a fundamental mode
pulsator. Furthermore, we investigated the variation of visibility
function and diameter with phase. The Rosseland angular diameter of
o Cet increased from 28.9 ± 0.3 mas (corresponding to a Rosseland
radius of 332 ± 38 R⊙ for a distance of D=107±12 pc) at
Φ=0.13 to 34.9 ± 0.4 mas (402 ± 46 R⊙) at Φ=0.4. The
error of the Rosseland linear radius almost entirely results from the
error of the parallax, since the error of the angular diameter is only
approximately 1%. Based on observations collected at the European
Southern Observatory, Paranal, Chile (public commissioning data). Based on data collected at the Special Astrophysical Observatory
(SAO), Russia.
Title: Evidence for Bipolar Jets in Late Stages of AGB Winds
Authors: Vinković, D.; Hofmann, K. -H.; Elitzur, M.; Weigelt, G.
Bibcode: 2004ASPC..313..321V
Altcode: 2003astro.ph.10012V; 2004apnw.conf..321V
Bipolar expansion at various stages of evolution has been recently
observed in a number of AGB stars. The expansion is driven by bipolar
jets that emerge late in the evolution of AGB winds. The wind traps
the jets, resulting in an expanding, elongated cocoon. Eventually
the jets break-out from the confining spherical wind, as recently
observed in W43A. This source displays the most advanced evolutionary
stage of jets in AGB winds. The earliest example is IRC+10011, where
the asymmetry is revealed in high-resolution near-IR imaging. In this
source the jets turned on only ∼ 200 years ago, while the spherical
wind is ∼ 4000 years old.
Title: LINC-NIRVANA: first attempt of an instrument for a 23-m-class
telescope
Authors: Gassler, Wolfgang; Herbst, Thomas M.; Ragazzoni, Roberto;
Andersen, David R.; Arcidiacono, Carmelo; Baumeister, Harald; Beckmann,
Udo; Bertram, Thomas; Bizenberger, Peter; Bohnhardt, Hermann; Diolaiti,
Emiliano; Eckart, Andreas; Farinato, Jacopo; Ligori, Sebastiano; Rix,
Hans-Walter; Rohloff, Ralf-Rainer; Salinari, Piero; Soci, Roberto;
Straubmeier, Christian; Vernet-Viard, Elise; Weigelt, Gerd; Weiss,
Robert; Xu, Wenli
Bibcode: 2004SPIE.5382..742G
Altcode:
LINC-NIRVANA is a Fizeau interferometer which will be built for the
Large Binocular Telescope (LBT). The LBT exists of two 8.4m mirrors
on one mounting with a distance of 22.8m between the outer edges of
the two mirrors. The interferometric technique used in LINC-NIRVANA
provides direct imaging with the resolution of a 23m telescope in one
direction and 8.4m in the other. The instrument uses multi-conjugated
adaptive optics (MCAO) to increase the sky coverage and achieve the
diffraction limit in J, H, K over a moderate Field of View (2 arcmin in
diameter). During the preliminary design phase the team faced several
problems similar to those for an instrument at a 23m telescope. We
will give an overview of the current design, explain problems related
to 20m class telescopes and present solutions.
Title: VizieR Online Data Catalog: Nearby multiple stars speckle
interferometry (Balega+, 2004)
Authors: Balega, I.; Balega, Y. Y.; Maksimov, A. F.; Pluzhnik, E. A.;
Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2004yCat..34220627B
Altcode:
The observations presented here were obtained in October 1999 using
the new speckle camera developed in 1998. (3 data files).
Title: The central dusty torus in the active nucleus of NGC 1068
Authors: Jaffe, W.; Meisenheimer, K.; Röttgering, H. J. A.; Leinert,
Ch.; Richichi, A.; Chesneau, O.; Fraix-Burnet, D.; Glazenborg-Kluttig,
A.; Granato, G. -L.; Graser, U.; Heijligers, B.; Köhler, R.; Malbet,
F.; Miley, G. K.; Paresce, F.; Pel, J. -W.; Perrin, G.; Przygodda,
F.; Schoeller, M.; Sol, H.; Waters, L. B. F. M.; Weigelt, G.; Woillez,
J.; de Zeeuw, P. T.
Bibcode: 2004Natur.429...47J
Altcode:
Active galactic nuclei (AGNs) display many energetic phenomena-broad
emission lines, X-rays, relativistic jets, radio lobes-originating
from matter falling onto a supermassive black hole. It is widely
accepted that orientation effects play a major role in explaining
the observational appearance of AGNs. Seen from certain directions,
circum-nuclear dust clouds would block our view of the central
powerhouse. Indirect evidence suggests that the dust clouds form a
parsec-sized torus-shaped distribution. This explanation, however,
remains unproved, as even the largest telescopes have not been
able to resolve the dust structures. Here we report interferometric
mid-infrared observations that spatially resolve these structures in
the galaxy NGC 1068. The observations reveal warm (320K) dust in a
structure 2.1 parsec thick and 3.4 parsec in diameter, surrounding a
smaller hot structure. As such a configuration of dust clouds would
collapse in a time much shorter than the active phase of the AGN,
this observation requires a continual input of kinetic energy to the
cloud system from a source coexistent with the AGN.
Title: VLTI/VINCI observations of the nucleus of NGC 1068 using the
adaptive optics system MACAO
Authors: Wittkowski, M.; Kervella, P.; Arsenault, R.; Paresce, F.;
Beckert, T.; Weigelt, G.
Bibcode: 2004A&A...418L..39W
Altcode: 2004astro.ph..3497W
We present the first near-infrared K-band long-baseline interferometric
measurement of the nucleus of the prototype Seyfert 2 Galaxy NGC
1068 with resolution λ/B ∼ 10 mas obtained with the Very Large
Telescope Interferometer (VLTI) and the two 8.2 m diameter Unit
Telescopes UT 2 and UT 3. The adaptive optics system MACAO (Multi
Application Curvature Adaptive Optics) was employed to deliver
wavefront-corrected beams to the K-band commissioning instrument
VINCI. A squared visibility amplitude of 16.3 ± 4.3% was measured for
NGC 1068 at a sky-projected baseline length of 45.8 m and azimuth angle
44.9 deg. This value corresponds to a FWHM of the K-band intensity
distribution of 5.0 ± 0.5 mas (0.4 ± 0.04 pc at the distance of
NGC 1068) if it consists of a single Gaussian component. Taking into
account K-band speckle interferometry observations (Wittkowski et
al. \cite{wittkowski}; Weinberger et al. \cite{weinberger}; Weigelt et
al. \cite{weigelt}), we favor a multi-component model for the intensity
distribution where a part of the flux originates from scales clearly
smaller than ∼5 mas (⪉0.4 pc), and another part of the flux
from larger scales. The K-band emission from the small (⪉5 mas)
scales might arise from substructure of the dusty nuclear torus, or
directly from the central accretion flow viewed through only moderate
extinction. Based on public commissioning data released from the
VLTI (www.eso.org/projects/vlti/instru/vinci/ vinci_data_sets.html).
Title: Peering into the heart of a high-mass star forming region:
Bispectrum speckle interferometry of the ultracompact H II region
K3-50 A
Authors: Hofmann, K. -H.; Balega, Y. Y.; Preibisch, T.; Weigelt, G.
Bibcode: 2004A&A...417..981H
Altcode:
We present K'-band bispectrum speckle interferometry of the ultracompact
H II region K3-50A. Our image resolves the central 1''× 1'' region
into at least 7 point-like objects. We find K'-band counterparts
for all but one of the N-band sources discovered by Okamoto et
al. (\cite{Okamoto03}), and there are additional K'-band sources which
were unresolved in the N-band images. Our reconstructed image also
reveals the fine-structure of the cone-shaped nebulosity extending
to the south. The brightest K'-band source is located exactly at the
tip of the cone-shaped nebulosity. The nebula shows several arcs and
the orientation of its main axis agrees very well with the direction
of the CO outflow from K3-50A. This nebulosity therefore very likely
represents the clumpy inner surface of a partially evacuated cavity
excavated by the strong outflows. Based on observations obtained
at the Special Astrophysical Observatory with the 6 m telescope.
Title: Speckle interferometry of the HAeBe star V376 Cas
Authors: Smith, K. W.; Balega, Y. Y.; Hofmann, K. -H.; Preibisch,
Th.; Schertl, D.; Weigelt, G.
Bibcode: 2004A&A...413..217S
Altcode: 2003astro.ph..9759S
We report H- and K'-band speckle interferometric observations of the
HAeBe star V376 Cas. Our observations show that the object is partially
resolved. The visibility curves suggest three separate components:
a large scattering envelope visible only in the H band, a component
approximately 100 mas in radius, and a component with a Gaussian HWHM of
approximately 8±3 mas, corresponding to approximately 5 AU at 600 pc
distance, which contributes most of the flux. We compare the smallest
structure to the radius of dust sublimation in the radiation field of
the star and find that the radius is approximately six times larger
than that expected. This may indicate that the inner regions of the
system are in fact obscured by a flaring circumstellar disk or torus
seen close to edge-on. Based on observations performed with the
6 m telescope of the Special Astrophysical Observatory, Russia.
Title: Bispectrum speckle interferometry of the massive protostellar
outflow source AFGL 2591
Authors: Preibisch, T.; Balega, Y. Y.; Schertl, D.; Weigelt, G.
Bibcode: 2003A&A...412..735P
Altcode:
We present bispectrum speckle interferometry of the massive protostellar
object AFGL 2591 in the near-infrared K-band. Our reconstructed
image of the outflow cavity of AFGL 2591 has a resolution of 170 mas,
corresponding to physical scales of ~ 170 AU at the distance of the
object, and shows the loops which extend from the bright, compact source
in unprecedented detail. The central source is clearly resolved and
has an uniform-disk diameter of ~ 40 mas (40 AU). We use 2D radiation
transfer simulations to show that the resolved structure probably
corresponds to the inner rim of a geometrically thick circumstellar
disk or envelope at the dust sublimation radius. Our image also reveals
a structure that might represent an edge-on circumstellar disk around
one of the other young stellar objects near AFGL 2591.
Title: High-resolution infrared imaging of young outflow-sources
Authors: Preibisch, Thomas; Schertl, Dieter; Weigelt, Gerd
Bibcode: 2003Ap&SS.287..179P
Altcode:
We discuss recent results from near-infrared bispectrum speckle
interferometry observations of the young outflow sources in the S140 and
Mon R2 star forming regions. With spatial resolutions down to 0.075'',
our data represent the highest resolution images obtained so far for
these objects and exhibit previously unseen complex structures in
the immediate vicinity of the young stellar objects. We discuss the
relation of these structures to the jets and outflows.
Title: Fundamental parameters and origin of the very eccentric binary
41 Dra
Authors: Tokovinin, A.; Balega, Y. Y.; Pluzhnik, E. A.; Shatsky,
N. I.; Gorynya, N. A.; Weigelt, G.
Bibcode: 2003A&A...409..245T
Altcode:
The evolutionary status and origin of the most eccentric known
binary in a quadruple system, 41 Dra (e=0.9754, period 3.413 yr),
are discussed. New observations include the much improved combined
speckle-interferometric orbit, resolved photometry of the components
and their spectroscopic analysis. The age of the system is 2.5 +/-
0.2 Gyr; all four components are likely coeval. The high eccentricity
of the orbit together with known age and masses provide a constraint
on the tidal circularization theory: it seems that the eccentric
orbit survived because the convective zones of the F-type dwarfs
were very thin. Now as the components of 41 Dra are leaving the Main
Sequence, their increased interaction at each periastron passage
may result in detectable changes in period and eccentricity. Tables 1, 2, and 3 are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/245
Title: JHK'-band IOTA interferometry of the circumstellar environment
of R CrB
Authors: Ohnaka, K.; Beckmann, U.; Berger, J. -P.; Brewer, M. K.;
Hofmann, K. -H.; Lacasse, M. G.; Malanushenko, V.; Millan-Gabet, R.;
Monnier, J. D.; Pedretti, E.; Schertl, D.; Schloerb, F. P.; Shenavrin,
V. I.; Traub, W. A.; Weigelt, G.; Yudin, B. F.
Bibcode: 2003A&A...408..553O
Altcode:
We report the first long-baseline interferometry of the circumstellar
dust environment of R CrB. The observations were carried out with
the Infrared Optical Telescope Array (IOTA), using our new JHK' beam
combiner which enables us to record fringes in the J, H, and K' bands
simultaneously. The circumstellar dust envelope of R CrB is resolved
at a baseline of 21 m along a position angle of ~ 170deg,
and the visibilities in the J, H, and K' bands are 0.97 +/- 0.06, 0.78
+/- 0.06, and 0.61 +/- 0.03, respectively. These observed visibilities,
together with the K'-band visibility obtained by speckle interferometry
with baselines of up to 6 m, and the spectral energy distribution
are compared with predictions from spherical dust shell models which
consist of the central star and an optically thin dust shell. The
comparison reveals that the observed J- and H-band visibilities are in
agreement with those predicted by these models, and the inner radius
and inner boundary temperature of the dust shell were derived to be
60-80 Rstar and 950-1050 K, respectively. However, the
predicted K'-band visibilities are found to be ~ 10% smaller than the
one obtained with IOTA. Given the simplifications adopted in our models
and the complex nature of the object, this can nevertheless be regarded
as rough agreement. As a hypothesis to explain this small discrepancy,
we propose that there might be a group of newly formed dust clouds,
which may appear as a third visibility component.
Title: Diffraction-limited Bispectrum Speckle Interferometry
Authors: Weigelt, Gerd; Hofmann, Karl-Heinz; Preibisch, Thomas;
Balega, Yuri
Bibcode: 2003ANS...324...68W
Altcode: 2003ANS...324b..68W; 2003ANS...324..P40W
No abstract at ADS
Title: Bispectrum Speckle Interferometry
Authors: Weigelt, G.; Blöcker, T.; Hofmann, K. -H.; Men'shchikov,
A.; Winters, J. M.
Bibcode: 2003ANS...324Q..66W
Altcode: 2003ANS...324..P37W; 2003ANS...324b..66W
No abstract at ADS
Title: High-Resolution Near-Infrared Speckle Interferometry and
Radiative Transfer Modeling of the OH/IR Star OH104.9+2.4
Authors: Riechers, Dominik; Berger, Michael; Balega, Yuri; Driebe,
Thomas; Hofmann, Karl-Heinz; Weigelt, Gerd
Bibcode: 2003ANS...324..136R
Altcode: 2003ANS...324..P50R; 2003ANS...324c.136R
No abstract at ADS
Title: VINCI VLTI Interferometry of Mira Stars
Authors: Eberhardt, Maren; Woodruff, Henry C.; Driebe, T.; Hofmann,
K. -H.; Scholler, M.; Scholz, M.; Weigelt, G.; Wittkowski, M.
Bibcode: 2003ANS...324..136E
Altcode: 2003ANS...324..P51E; 2003ANS...324c.136E
No abstract at ADS
Title: Spectro-interferometry of the Mira Star T Cep with the IOTA
Interferometer and Comparison with Models
Authors: Weigelt, G.; Beckmann, U.; Blöcker, T.; Hofmann, K. -H.;
Ohnaka, K.; Schertl, D.; Brewer, M. K.; Schloerb, F.; Efimov, Y. N.;
Shenavrin, V.; Yudin, B.; Berger, J.; Lacasse, M.; Millan-Gabet, R.;
Monnier, J.; Morel, S.; Pedretti, E.; Traub, W.; Malanushenko, V.;
Mennesson, B.; Scholz, M.
Bibcode: 2003ANS...324...71W
Altcode: 2003ANS...324..P47W; 2003ANS...324b..71W
No abstract at ADS
Title: VizieR Online Data Catalog: ADS 11061 radial velocities
(Tokovinin+, 2003)
Authors: Tokovinin, A.; Balega, Y. Y.; Pluzhnik, E. A.; Shatsky,
N. I.; Gorynya, N. A.; Weigelt, G.
Bibcode: 2003yCat..34090245T
Altcode:
Individual radial velocities (heliocentric date, velocity, error),
interferometric observations and residuals to orbits are given for the
components of ADS 11061 (HD 166866 and HD 166865) (3 data files).
Title: JHK'-Band IOTA Interferometry of the Mira Star T Cep and the
Circumstellar Environment of R CrB
Authors: Ohnaka, K.; Beckmann, U.; Berger, J. -P.; Brewer, M. K.;
Hofmann, K. -H.; Lacasse, M. G.; Millan-Gabet, R.; Monnier, J. D.;
Pedretti, E.; Schertl, D.; Schloerb, F. P.; Scholz, M.; Traub, W. A.;
Weigelt, G.
Bibcode: 2003ANS...324...61O
Altcode: 2003ANS...324c..61O; 2003ANS...324..H03O
No abstract at ADS
Title: Bi-spectrum Speckle Inter-ferometry of Young Jet- and
Outflow-sources
Authors: Preibisch, Thomas; Schertl, Dieter; Weigelt, Gerd; Balega,
Yuri
Bibcode: 2003ANS...324Q..16P
Altcode: 2003ANS...324..C02P; 2003ANS...324b..16P
No abstract at ADS
Title: Bispectrum Speckle Interferometry of the B[e] Star MWC349A
Authors: Hofmann, K. -H.; Ikhsanov, N. R.; Weigelt, G.; Miroshnichenko,
A. S.
Bibcode: 2003ANS...324Q..69H
Altcode: 2003ANS...324Q.P42H; 2003ANS...324b..69H
No abstract at ADS
Title: The Massive Multiple Stars in the Orion Trapezium: Orbital
Motion, Physical Properties, and Implications on Star Formation
Scenarios
Authors: Preibisch, Thomas; Balega, Yuri Y.; Schertl, Dieter;
Weigelt, Gerd
Bibcode: 2003ANS...324...41P
Altcode: 2003ANS...324c..41P; 2003ANS...324..E11P
No abstract at ADS
Title: IOTA Observation of the Circum-stellar Envelope of R CrB
Authors: Ohnaka, K.; Beckmann, U.; Hofman, K. -H.; Malanushenko, V.;
Schertl, D.; Weigelt, G.; Ahearn, A.; Berger, J. -P.; Lacasse, M.;
Millan-Gabet, R.; Monnier, J.; Traub, W.; Brewer, M.; Schloerb, P.;
Shenavrin, V.; Yudin, B.
Bibcode: 2003ANS...324...66O
Altcode: 2003ANS...324b..66O; 2003ANS...324..P36O
No abstract at ADS
Title: Bispectrum speckle interferometry of the carbon star IRC +10216
Authors: Weigelt, G.; Blöcker, T.; Hofmann, K. -H.; Men'shchikov,
A.; Winters, J. M.; Balega, Y.
Bibcode: 2003ASSL..283..249W
Altcode: 2003mlps.work..249W
No abstract at ADS
Title: Orbital motion of the massive multiple stars in the Orion
Trapezium
Authors: Schertl, D.; Balega, Y. Y.; Preibisch, Th.; Weigelt, G.
Bibcode: 2003A&A...402..267S
Altcode:
We present bispectrum speckle interferometry of the multiple Orion
Trapezium stars theta 1Ori A, theta 1Ori B, and
theta 1Ori C obtained with the SAO 6 m telescope in Russia
over a period of 5.5 years (epochs 1995-2001). Our diffraction-limited
images have a resolution lambda /D of 42 mas (J-band), 57 mas (H-band)
and 76 mas (K-band). We clearly detect motion of the companions relative
to their primary stars in the systems theta 1Ori A1-2
(mean separation rho ~ 220 mas, change in position angle Delta PA =
6degr ), theta 1Ori B2-3 (rho ~ 205 mas, Delta PA = 8degr ),
and theta 1Ori C1-2 (rho ~ 37 mas, Delta PA = 18degr ). In
our K-band image of theta 1Ori B we resolve a fourth visual
component, confirming its discovery by Simon et al. (\cite{Sim99}). We
determine the J, H, and K magnitudes of the system components and
estimate the stellar masses of the companions in the HR-diagram. The
companions theta 1Ori C2 and theta 1Ori B2 show
clear evidence of near-infrared excess in the color-color diagram. The
companions theta 1Ori A2 and theta 1Ori B3 show
much stronger extinction than their primary stars, providing evidence
of the presence of circumstellar material around the companions.
Title: Bispectrum speckle interferometry and future long-baseline
interferometry of the carbon star IRC+10216
Authors: Bloecker, Thomas; Balega, Yuri; Hofmann, Karl-Heinz;
Men'shchikov, Alexander B.; Weigelt, Gerd; Winters, Jan-Martin
Bibcode: 2003SPIE.4838.1055B
Altcode:
We present near-infrared (JHK) bispectrum speckle-interferometry
monitoring of IRC+10216 obtained with the SAO 6m telescope. The
present speckle observations covering baselines up to 6m provide
important complementary informations for future long-baseline
interferometry. To disentangle the apparent motions of the various
IRC+10216 components and to reveal the location of the central star,
future high-resolution observations are of utmost value for the
interpretation of this astrophysical key object. The J-, H-, and
K-band resolutions of our speckle observations are 50 mas, 56 mas,
and 73 mas, resp. The K-band observations cover 8 different epochs from
1995 to 2001 and show the dynamical evolution of the dust shell which
consists of several compact components within a 200 milli-arcsecond
radius. Our recent two-dimensional radiative transfer modelling has
shown that the central star is probably not located at the brightest
dust-shell component A but at the position of the northern component
B. The bright and compact component A is the southern lobe of a bipolar
structure. The changes of the dust-shell structure can be related
to corresponding changes of the optical depth caused, for instance,
by mass-loss variations. The present observations are consistent with
the predictions of hydrodynamical models that enhanced dust formation
takes place on a timescale of several pulsational cycles.
Title: IOTA observation of the circumstellar envelope of R CrB
Authors: Ohnaka, Keiichi; Beckmann, Udo; Berger, Jean-Philippe; Brewer,
Michael K.; Hofmann, Karl-Heinz; Lacasse, Marc G.; Malanushenko,
Victor; Millan-Gabet, Rafael; Monnier, John D.; Pedretti, Ettore;
Schertl, Dieter; Schloerb, F. Peter; Shenavrin, Victor; Traub, Wesley
A.; Weigelt, Gerd; Yudin, Boris
Bibcode: 2003SPIE.4838.1068O
Altcode:
We report the first long-baseline interferometric observations of
R CrB. The observations were carried out at the Infrared Optical
Telescope Array (IOTA), using our new JHK beam combiner which enables
us to record fringes simultaneously in the J-, H-, and K-bands. The
circumstellar envelope of R CrB is resolved at a baseline of 21 m,
and the K-band visibility is derived to be 0.61 +/- 0.03 along a
position angle of about 170 degrees. The visibility obtained with
IOTA, as well as speckle visibilities with baselines up to 6 m and the
spectral energy distribution (SED), are fitted with 2-component models
consisting of the central star and an optically thin dust shell. The
K-band visibilities predicted by the models are about 10% smaller than
the visibility obtained with IOTA. However, given the simplifications
adopted in our models and the complex nature of the object, this can
be regarded as rough agreement. As a hypothesis to explain the small
discrepancy, we propose that there might be a group of newly formed
dust clouds, which might appear as a third visibility component.
Title: Astrophysical potential of the AMBER/VLTI instrument
Authors: Malbet, Fabien; Bloecker, Thomas; Foy, Renaud; Fraix-Burnet,
Didier; Mathias, Philippe; Marconi, Alesssandro; Monin, Jean-Louis;
Petrov, Romain G.; Stee, Philippe; Testi, Leonardo; Weigelt, Gerd
Bibcode: 2003SPIE.4838..917M
Altcode:
AMBER is the near-infrared instrument of the Very Large Telescope
Interferometer (VLTI). With a spectral resolution up to 10000 in the
1.2-2.4 micron wavelength range, AMBER will offer the possibility to
combine 3 beams from the VLTI array either 8-m or 1.8m telescopes. The
instrument has been designed to bring high precision measurement
and high sensitivity and therefore opens the way to new domain of
investigation in stellar physics and for the first time access to
extragalactic sources. We show how the performance of the instrument
can apply in these different astrophysical fields. We present the
work of the Science Group and the AMBER consortium who defined precise
astrophysical goals for the first years of operation.
Title: Near-infrared IOTA interferometry of the symbiotic star CH Cyg
Authors: Hofmann, Karl-Heinz; Beckmann, Udo; Berger, Jean-Philippe;
Bloecker, Thomas; Brewer, Michael T.; Lacasse, Marc G.; Malanushenko,
Victor; Millan-Gabet, Rafael; Monnier, John D.; Ohnaka, Keiichi;
Pedretti, Ettore; Schertl, Dieter; Schloerb, F. Peter; Scholz, Michael;
Traub, Wesley A.; Weigelt, Gerd; Yudin, Boris
Bibcode: 2003SPIE.4838.1043H
Altcode:
We present observations of the symbiotic star CH Cyg with a new
JHK-band beam combiner mounted to the IOTA interferometer. The new
beam combiner consists of an anamorphic cylindrical lens system and a
grism, and allows the simultaneous recording of spectrally dispersed
J-, H- and K-band Michelson interferograms. The observations of CH
Cyg were conducted on 5, 6, 8 and 11 June 2001 using baselines of
17m to 25m. From the interferograms of CH Cyg, J-, H-, and K-band
visibility functions can be determined. Uniform-disk fits to the
visibilities give, e.g., stellar diameters of (7.8 +/- 0.6) mas and
(8.7 +/- 0.8) mas in H and K, respectively. Angular stellar filter
radii and Rosseland radii are derived from the measured visibilities
by fitting theoretical center-to-limb intensity variations (CLVs)
of Mira star models. The available HIPPARCOS parallax of CH Cyg
allows us to determine linear radii. For example, on the basis of
the K-band visibility, Rosseland radii in the range of 214 to 243
solar radii can be derived utilizing CLVs of different fundamental
mode Mira models as fit functions. These radii agree well within the
error bars with the corresponding theoretical model Rosseland radii
of 230 to 282 solar radii. Models of first overtone pulsators are not
in good agreement with the observations. The wavelength dependence of
the stellar diameter can be well studied by using visibility ratios
V(λ1)/V(λ2) since ratios of visibilities of
different spectral channels can be measured with higher precision
than absolute visibilities. We found that the 2.03 μm uniform disk
diameter of CH Cyg is approximately 1.1 times larger than the 2.15
μm and 2.26 μm uniform-disk diameter.
Title: Using the near infrared VLTI instrument AMBER
Authors: Petrov, Romain G.; Malbet, Fabien; Weigelt, Gerd; Lisi,
Franco; Puget, Pascal; Antonelli, Pierre; Beckmann, Udo; Lagarde,
Stephane; Le Coarer, Etienne; Robbe-Dubois, Sylvie; Duvert, Gilles;
Gennari, Sandro; Chelli, Alain; Dugue, Michel; Rousselet-Perraut,
Karine; Vannier, Martin; Mourard, Denis
Bibcode: 2003SPIE.4838..924P
Altcode:
AMBER is the General User near infrared focal instrument of the Very
Large Telescope Interferometer. Its a single mode, dispersed fringes,
three telescopes instrument. A limiting magnitude of the order of H=13
will allow to tackle a fair sample of extra galactic targets. A very
high accuracy, in particular in color differential phase and closure
phase modes gives good hope for very high dynamic range observation,
possibly including hot extra solar planets. The relatively high maximum
spectral resolution, up to 10000, will allow some stellar activity
observations. Between this extreme goals, AMBER should have a wide
range of applications including Young Stellar Objects, Evolved Stars,
circumstellar material and many others. This paper tries to introduce
AMBER to its future users with information on what it measures, how
it is calibrated and hopes to give the readers ideas for applications.
Title: Interferometric studies of nearby galactic centers
Authors: Wittkowski, Markus; Duschl, Wolfgang; Hofmann, Karl-Heinz;
Men'shchikov, Alexander B.; Weigelt, Gerd
Bibcode: 2003SPIE.4838.1378W
Altcode:
We discuss the potential of interferometric studies of nearby galactic
nuclei with long-baseline interferometric facilities. Information
on the morphology of galactic centers has so far been limited to
angular sizes corresponding to the diffraction limit of 6-10 m class
telescopes. Optical and near-infrared interferometry could in principle
be used to reach significantly higher angular resolution, but has
so far only been used for bright objects due to the small collecting
areas of existing interferometers. Right now, the first interferometers
consisting of 8-10 m class telescopes are starting operations and,
hence, will soon allow us for the first time to study galactic centers
on angular scales which are of an order of magnitude smaller than ever
before, i.e. on scales corresponding to baselines of up to 100 m. We
discuss these facilities and report on the observational techniques
and strategies which are relevant for interferometric observations of
these objects. We review imaging results of nearby galactic centers
with highest angular resolution so far, with an emphasis on our
bispectrum speckle interferometry studies of the core of the Seyfert
galaxy NGC 1068. Employing these results, we analyze how near-infrared
interferometry can discriminate between the different scenarios which
are consistent with our current knowledge based on observations. In
particular, characteristic sizes of the circumnuclear dusty torus can be
derived with higher precision, additional dust components and the inner
part of the jet can be identified, and radiative transfer models of the
torus can be better constrained. Furthermore, the flux contribution of
central source components can be separated from those of the torus,
and thus they can be modeled in more detail. These investigations
may ultimately result in a refinement of the unification scheme of
galactic nuclei.
Title: New Beam-Combination Techniques at IOTA
Authors: Traub, Wesley A.; Ahearn, Angela; Carleton, Nathaniel P.;
Berger, Jean-Philippe; Brewer, Michael K.; Hofmann, Karl-Heinz; Kern,
Pierre Y.; Lacasse, Marc G.; Malbet, Fabien; Millan-Gabet, Rafael;
Monnier, John D.; Ohnaka, Keiichi; Pedretti, Ettore; Ragland, Sam;
Schloerb, F. Peter; Souccar, Kamal; Weigelt, Gerd
Bibcode: 2003SPIE.4838...45T
Altcode:
New beam combination techniques, using two and three telescopes, have
been the focus of activity at IOTA during the past two years since
our last update. In particular, we have added a third telescope,
made closure-phase measurements, demonstrated two- and three-beam
combination with integrated optics combiners, demonstrated two-beam
combination with an asymmetric coupler, and made simultaneous JHK
visibility measurements with an image-plane combiner.
Title: Bispectrum speckle interferometry and future long-baseline
interferometry of the young bipolar outflow source S140 IRS1
Authors: Preibisch, Thomas; Balega, Yuri; Schertl, Dieter; Hofmann,
Karl-Heinz; Weigelt, Gerd
Bibcode: 2003SPIE.4838.1047P
Altcode:
We present bispectrum speckle interferometric observations of the
deeply embedded protostellar outflow source S140 IRS1. Using the SAO
6 m telescope, we obtained a K-band image with diffraction-limited
resolution of 76 mas, which is the highest resolution image of a young
outflow source ever obtained in the infrared. Our image shows the
circumstellar environment of S140 IRS1 in unprecedented detail and
suggests that the central source is marginally resolved with a FWHM
diameter of approximately 20 mas (approx 20 AU). The dominant feature
is a bright extended and very clumpy structure pointing away from the
central source in exactly the same direction as the blue-shifted CO
outflow lobe. We interprete this feature as the clumpy inner surface of
a partially evacuated cavity in the circumstellar envelope around IRS1,
which has been excavated by the strong outflow from IRS1. In addition,
we find several arc-like structures north-east of IRS 1, extended
diffuse emission south of IRS 1, and four new point sources. The diffuse
and fragmentary structures close to IRS 1 appear to trace circumstellar
material swept up by energetic outflows. In combination with molecular
line emission maps from the literature, our image provides direct
confirmation that two distinct bipolar outflow systems continue
to be driven from IRS 1 on scales between 3" and 100". Our speckle
observations provide important complementary information for future
long-baseline interferometric observations, for example with the LBT.
Title: JHK-band spectro-interferometry of T Cep with the IOTA
interferometer
Authors: Weigelt, Gerd; Beckmann, Udo; Berger, Jean-Philippe; Bloecker,
Thomas; Brewer, Michael K.; Hofmann, Karl-Heinz; Lacasse, Marc G.;
Malanushenko, Victor; Millan-Gabet, Rafael; Monnier, John D.; Ohnaka,
Keiichi; Pedretti, Ettore; Schertl, Dieter; Schloerb, F. Peter;
Scholz, Michael; Traub, Wesley A.; Yudin, Boris
Bibcode: 2003SPIE.4838..181W
Altcode:
Our new IOTA JHK-band beam combiner allows the simultaneous recording
of spectrally dispersed J-, H- and K-band Michelson interferograms. In
this paper we present our IOTA observations of the Mira star T Cep
with this beam combiner (observations in June 2001; four baselines
in the range of 14 m to 27 m). The beam combiner optics consists
of an anamorphic cylindrical lens system and a prism. From the
interferograms of T Cep we derive the visibilities and the J-, H-,
and K-band uniform-disk diameters of 14.0 +/- 0.6 mas, 13.7 +/- 0.6
mas and 15.0 +/- 0.6 mas, respectively. Angular stellar filter radii
and Rosseland radii are derived from the measured visibilities by
fitting theoretical center-to-limb intensity variations (CLVs) of
different Mira star models. The available HIPPARCOS parallax (4.76
+/- 0.75 mas) of T Cep allows us to determine linear radii. For
example, from the K-band visibility we derive a Rosseland radius
of 329-50/+70 solar radii if we use the CLVs
of the M-models as fit functions. This radius is in good agreement
with the theoretical M-model Rosseland radius of 315 solar radii. The
comparison of measured stellar parameters (e.g. diameters, effective
temperature, visibility shape) with theoretical parameters indicates
whether any of the models is a fair representation of T Cep. The ratios
of visibilities of different spectral channels can be measured with
higher precision than absolute visibilities. Therefore, we use the
visibility ratios V(λ1)/V(λ2) to investigate
the wavelength dependence of the stellar diameter. We find that the
2.03 μm uniform-disk diameter of T Cep is about 1.26 times larger
than the 2.26 μm uniform-disk diameter.
Title: Diffraction-Limited Speckle Interferometry and Modeling of
the Circumstellar Envelope of R CrB at Maximum and Minimum Light
Authors: Ohnaka, K.; Blöcker, T.; Hofmann, K. -H.; Ikhsanov, N. R.;
Weigelt, G.; Balega, Y.; Shenavrin, V. I.; Yudin, B. F.; Efimov, Y. S.
Bibcode: 2003IAUS..209...88O
Altcode:
No abstract at ADS
Title: Iron abundance in the atmospheres of components of the binary
system 41 Draconis
Authors: Balega, Yu. Yu.; Leushin, V. V.; Weigelt, G.
Bibcode: 2003BSAO...55....5B
Altcode:
Iron abundances, FeI and FeII lines equivalent widths, and
microturbulence velocities were found for the components of a highly
eccentric spectroscopic and interferometric binary system 41 Dra from
high resolution spectra obtained close to the periastron. Weighted
mean values of iron abundances in the atmospheres are lgN(Fe) =
7.66 ± 0.03 and lgN(Fe) = 7.72 ± 0.03 for the component a and b,
correspondingly. These values are approximately 0.2 dex higher than the
solar iron abundance. The flux ratio, measured from the depths of FeI
and FeII lines, Eb/Ea = 0.7, is in agreement with
the magnitude difference 0.m41 found recently by speckle
interferometry. It is supposed that the weaker companion of the binary
has slightly higher effective temperature.
Title: A Multi-Wavelength Study of the Oxygen-Rich AGB Star CIT 3:
Bispectrum speckle interferometry and dust-shell modelling
Authors: Hofmann, K. -H.; Blöcker, T.; Weigelt, G.; Balega, Y.
Bibcode: 2003IAUS..209..121H
Altcode:
No abstract at ADS
Title: Bipolar Structures in the Dust Shell of the AGB Star IRC+10011
Authors: Vinkovíc, D.; Hofmann, K. -H.; Elitzur, M.; Weigelt, G.
Bibcode: 2003asdu.confE..64V
Altcode:
Planetary nebulae are largely asymmetric, while their progenitors,
AGB winds, are mostly spherically symmetric. This remains one of the
fundamental problems of planetary nebulae evolution. High-resolution
J-band imaging of IRC+10011, the prototype of high mass-loss rate AGB
winds, provides a rare example of shell asymmetry. Interpretation of
the observed asymmetry requires a 2D radiative transfer solver that can
handle arbitrary axially symmetric dust density configurations. LELUYA
(www.leluya.org) is the first such general-purpose code that can provide
the exact solution to an arbitrary multi-grain dust distribution around
an arbitrary heating source. By employing a new numerical method, the
implemented algorithm automatically traces the dust density and optical
depth gradients, creating the optimal unstructured triangular grid. The
radiative transfer equation, including dust scattering, absorption and
emission, is solved without any approximation. Unique to LELUYA is also
its ability to self-consistently reshape the sublimation/condensation
dust cavity around the source to accomodate for the unisotropic
diffuse radiation. We successfully explain the IRC+10011 images and the
overall spectral energy distribution. Particularly interesting is the
wavelength dependence of the imaged asymmetry, which disappears within
a wavelength shift of only 0.5 micron. The asymmetry is produced by an
unusual dust density distribution, traced by the J-band imaging. Two
bipolar cones with 1 / r0.5 density profile are imbedded
in the standard 1/r2 dusty wind profile. The cones are
still breaking though the 1/r2 wind, suggesting they are
a recent episode in the final short superwind phase of AGB evolution
before turning into a proto-planetary nebula.
Title: Interpreting the Evolving Clumpy Shell Structure of IRC +
10216 in Terms of Time Dependent Dust Shell Models
Authors: Winters, J. M.; Blöcker, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2003IAUS..209..127W
Altcode:
No abstract at ADS
Title: Spectral Observations of Envelopes around Stars in Late Stages
of Stellar Evolution
Authors: Blöcker, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2003EAS.....6..203B
Altcode: 2002astro.ph..7093B
Interferometric observations of stars in late stages of stellar
evolution and the impact of VLTIobservations are discussed. Special
attention is paid to the spectral information that can be derived from
these observations and on the corresponding astrophysical interpretation
of the data by radiative transfer modelling. It is emphasized that for
the robust and non-ambiguous construction of dust-shell models it is
essential to take diverse and independent observational constraints into
account. Apart from matching the spectral energy distribution, the use
of spatially resolved information plays a crucial role for obtaining
reliable models. The combination of long-baseline interferometry data
with high-resolution single-dish data (short baselines), as obtained,
for example, by bispectrum speckle interferometry, provide complementary
information and will improve modelling and interpretation.
Title: Near-Infrared Monitoring of the Carbon Star IRC + 10216:
A High Spatial-Resolution Time Sequence of Dust-Shell Evolution
Authors: Weigelt, G.; Blöcker, T.; Hofmann, K. -H.; Men'shchikov,
A.; Winters, J. M.; Balega, Y.
Bibcode: 2003IAUS..209...83W
Altcode:
No abstract at ADS
Title: Speckle interferometer of the 6 m telescope
Authors: Maximov, A. F.; Balega, Yu. Yu.; Beckmann, U.; Weigelt, G.;
Pluzhnik, E. A.
Bibcode: 2003BSAO...56..102M
Altcode:
A description of the 6 m telescope speckle interferometer is
presented. Principles of operation and function of basic units are
briefly considered. Information on the processes of observations and
primary data reduction is given. Methods of measuring binary star
parameters and evaluation of the power spectrum and image restoration
are presented. It is shown that the use of the new device gives us an
opportunity to reach acquisition rate up to 6 frames per second, and
to observe objects up to 14m with a diffraction telescope
resolution of 0."0.2.
Title: High-Resolution Infrared Imaging of Young Outflow-Sources
Authors: Preibisch, Thomas; Schertl, Dieter; Weigelt, Gerd
Bibcode: 2003IAUS..221P.126P
Altcode:
For a better understanding of the mechanisms by which jets and outflows
from young stellar objects are generated accelerated and collimated it
is essential to look as close as possible to their launching point at
the disk/star boundary. High-spatial resolution is therefore of crucial
importance for further progress in this field. In this contribution
we present recent results from our near-infrared bispectrum speckle
interferometry studies of several outflow sources. With a spatial
resolution of up to 0.055'' our images have the highest spatial
resolution achieved so far for these objects and exhibit previously
unseen complex structures. Our results include the identification
of two distinct bipolar outflow systems originating simultaneously
from the protostar S140 IRS1 the detection of an episodic precessing
jet from S140 IRS3 and the discovery of a micro-jet from one of the
embedded sources in Mon R2 IRS3. We will also discuss the relation of
the observed circumstellar structures to the jets and outflows from
the young stellar objects
Title: Bispectrum speckle interferometry of the B[e] star MWC 349A
Authors: Hofmann, K. -H.; Balega, Y.; Ikhsanov, N. R.; Miroshnichenko,
A. S.; Weigelt, G.
Bibcode: 2002A&A...395..891H
Altcode: 2002astro.ph..9533H
We present the results of bispectrum speckle interferometry of
the B[e] star MWC 349A obtained with the SAO 6 m telescope. Our
diffraction-limited J-, H-, and K-band images (resolutions 43-74
mas) suggest the star is surrounded by a circumstellar disk seen
almost edge-on. The observed visibility shape is consistent with
a two-component elliptical disk model, probably corresponding to
the gaseous and dusty components of the disk. We show that the
classification of the object as a pre-main-sequence star or a young
planetary nebula is problematic. An analysis of the uncertainties in
the basic parameter determination leads us to the conclusion that
MWC 349A is probably either a B[e] supergiant or a binary system,
in which the B[e]-companion dominates the observed properties.
Title: The Spectroscopic and Interferometric Orbit of Gliese 150.2
Authors: Balega, Yu. Yu.; Tokovinin, A. A.; Pluzhnik, E. A.;
Weigelt, G.
Bibcode: 2002AstL...28..773B
Altcode:
No abstract at ADS
Title: UBVJHKLM photometry and modeling of R Coronae Borealis
Authors: Yudin, B. F.; Fernie, J. D.; Ikhsanov, N. R.; Shenavrin,
V. I.; Weigelt, G.
Bibcode: 2002A&A...394..617Y
Altcode: 2002astro.ph..9531Y
We present the results of UBVJHKLM photometry of R CrB spanning the
period from 1976 to 2001. Studies of the optical light curve have
shown no evidence of any stable harmonics in the variations of the
stellar emission. In the L band we found semi-regular oscillations
with the two main periods of ~ 3.3 yr and ~ 11.9 yr and the full
amplitude of ~ 0fm8 and ~ 0fm6 , respectively. The colors of the warm
dust shell (resolved by Ohnaka et al. \cite{ohnaka01}) are found to
be remarkably stable in contrast to its brightness. This indicates
that the inner radius is a constant, time-independent characteristic
of the dust shell. The observed behavior of the IR light curve is
mainly caused by the variation of the optical thickness of the dust
shell within the interval tau (V)=0.2-0.4. Anticorrelated changes
of the optical brightness (in particular with P ~ 3.3 yr) have not
been found. Their absence suggests that the stellar wind of R CrB
deviates from spherical symmetry. The light curves suggest that the
stellar wind is variable. The variability of the stellar wind and the
creation of dust clouds may be caused by some kind of activity on the
stellar surface. With some time lag, periods of increased mass-loss
cause an increase in the dust formation rate at the inner boundary of
the extended dust shell and an increase in its IR brightness. We have
derived the following parameters of the dust shell (at mean brightness)
by radiative transfer modeling: inner dust shell radius rR
CrBm in ~ 110 R*, temperature TR CrBm
dust(rR CrBm in) ~ 860 K, dust density R CrBhoR
CrBm dust(rR CrBm in) ~ 1.1x 10-20
R CrBm g cm-3, optical depth tau (V) ~ 0.32 at 0.55 mu
m, mean dust formation rate dot {M}R CrBm dust ~ 3.1 x
10-9 Msun R CrBm yr-1, mass-loss rate
dot {M}R CrBm gas ~ 2.1 x 10-7 Msun
R CrBm yr-1, size of the amorphous carbon grains la 0.01
mu m, and B-V ~ -0.28. Tables 1 and 2 are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/394/617
Title: Properties of the close binary and circumbinary torus of the
Red Rectangle
Authors: Men'shchikov, A. B.; Schertl, D.; Tuthill, P. G.; Weigelt,
G.; Yungelson, L. R.
Bibcode: 2002A&A...393..867M
Altcode: 2002astro.ph..6189M
New diffraction-limited speckle images of the Red
Rectangle in the wavelength range 2.1-3.3
mu m with angular resolutions of 44-68 mas (Tuthill et
al. \cite{Tuthill_etal2002}) and previous speckle images at 0.7-2.2
mu m (Osterbart et al. \cite{Osterbart_etal1997}; Men'shchikov
et al. \cite{Men'shchikov_etal1998}) revealed well-resolved bright
bipolar outflow lobes and long X-shaped spikes originating deep inside
the outflow cavities. This set of high-resolution images stimulated
us to reanalyze all infrared observations of the Red
Rectangle using our two-dimensional radiative transfer
code. The high-resolution images imply a geometrically and optically
thick torus-like density distribution with bipolar conical cavities
and are inconsistent with the flat disk geometry frequently used
to visualize bipolar nebulae. The new detailed modeling, together
with estimates of the interstellar extinction in the direction of
the Red Rectangle enabled us to more accurately
determine one of the key parameters, the distance D ~ 710 pc with
model uncertainties of 70 pc, which is twice as far as the commonly
used estimate of 330 pc. The central binary is surrounded by a compact,
massive (M ~ 1.2 Msun), very dense dusty torus with hydrogen
densities reaching nH ~ 2.5 x 1012 cm-3
(dust-to-gas mass ratio \rhod/\rho ~ 0.01). The model
implies that most of the dust mass in the dense torus is in very
large particles and, on scales of more than an arcsecond, the polar
outflow regions are denser than the surrounding medium. The bright
component of the spectroscopic binary HD 44179 is
a post-AGB star with mass M\star ~ 0.57 Msun,
luminosity L\star ~ 6000 Lsun, and effective
temperature T\star ~ 7750 K. Based on the orbital elements
of the binary, we identify its invisible component with a helium white
dwarf with MWD ~ 0.35 Msun, LWD ~ 100
Lsun, and TWD ~ 6 x 104 K. The hot
white dwarf ionizes the low-density bipolar outflow cavities inside
the dense torus, producing a small H II region observed at radio
wavelengths. We propose an evolutionary scenario for the formation
of the Red Rectangle nebula, in which the binary
initially had 2.3 and 1.9 Msun components at a separation
of ~ 130 Rsun. The nebula was formed in the ejection of a
common envelope after Roche lobe overflow by the present post-AGB star.
Title: VizieR Online Data Catalog: UBVJHKLM photometry of R Corona
Borealis (Yudin+, 2002)
Authors: Yudin, B. F.; Fernie, J. D.; Ikhsanov, N. R.; Shenavrin,
V. I.; Weigelt, G.
Bibcode: 2002yCat..33940617Y
Altcode:
We present the results of UBVJHKLM photometry of R CrB spanning the
period from 1976 to 2001. (2 data files).
Title: Multiple Outflows from the Massive Protostar S140 IRS1
Authors: Preibisch, T.; Weigelt, G.; Schertl, D.; Balega, Y. Y.;
Smith, M. D.
Bibcode: 2002ASPC..267..407P
Altcode: 2002hsw..work..407P
We present a high-resolution near-infrared study of the deeply embedded
young stellar object S140 IRS1 and its environment.
Title: Photometric Observations of R Coronae Borealis in the Optical
and Infrared
Authors: Shenavrin, V. I.; Fernie, J. D.; Weigelt, G.; Yudin, B. F.
Bibcode: 2002ARep...46..805S
Altcode:
The results of long-term photometric observations of R CrB in the UBV
JHKLM bands are presented. The temporal and color characteristics of
the emission of the star itself and of its extended dust envelope
are analyzed in detail. No stable harmonic has been found in the
semiregular variations of the optical brightness of R CrB. Two
harmonics with periods P≈3.3 and 11.3 yrs have been detected in
the brightness variations of the dust envelope; the minima of these
variations coincided in 1999, resulting in a record decrease in the
LM brightness of the envelope. This by chance coincided in time with a
deep minimum of the visual brightness of the star, resulting in a unique
decrease in the total brightness of the star and dust envelope. This
enabled estimation of the bolometric flux of the hot dust clouds,
which made up only a few per cent of the bolometric flux of the
dust envelope. The brightness variations of the dust envelope are
not accompanied by appreciable color changes and are associated with
variations of its optical depth τ(V) in the range 0.2 0.4. The dust
envelope forms at a large and fairly constant distance from the star
, from material in its stellar wind, whose intensity obeys a Reimers
law. No variations synchronous with those of the optical depth of the
dust envelope, in particular, with the period P≈3.3 yrs, have been
found in the optical emission of R CrB, suggesting that the stellar
wind is not spherically symmetric. The dust envelope consists of small
grains (a gr≤0.01 µm), while the clouds screening the star from the
observer are made up of large grains (a gr≈0.1 µm). The activity
of R CrB, whose nature is unclear, is reflected in variations of the
stellar-wind intensity and the appearance of dust clouds in the line
of sight: these variations are repeated by corresponding changes in
the optical depth of the dust envelope with a delay of ∼4 years
(the time for a particle moving at V env≈45 km/s to move from the
star to the boundary of the dust envelope).
Title: IRC +10 216 in action: Present episode
of intense mass-loss reconstructed by two-dimensional radiative
transfer modeling
Authors: Men'shchikov, A. B.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2002A&A...392..921M
Altcode: 2002astro.ph..6410M
We present two-dimensional (2D) radiative transfer modeling of
IRC +10 216 at selected moments of its evolution
in 1995-2001, which correspond to three epochs of our series of 8
near-infrared speckle images (Osterbart et al. \cite{Osterbart_etal2000;
Weigelt et al. \cite{Weigelt_etal2002}). The high-resolution images
obtained over the last 5.4 years revealed the dynamic evolution of the
subarcsecond dusty environment of IRC +10 216 and our
recent time-independent 2D radiative transfer modeling reconstructed its
physical properties at the single epoch of January 1997 (Men'shchikov
et al. \cite{Men'shchikov_etal2001}). Having documented the complex
changes in the innermost bipolar shell of the carbon star, we
incorporate the evolutionary constraints into our new modeling to
understand the physical reasons for the observed changes. The new
calculations show that our previous static model is consistent with
the brightness variations seen in the near-infrared images, implying
that during the last 50 years, we have been witnessing an episode of
a steadily increasing mass loss from the central star, from dot {M} ~
10-5 Msun yr-1 to the rate of dot {M}
~ 3 x 10-4 Msun yr-1 in 2001. The
rapid increase of the mass loss of IRC +10 216 and
continuing time-dependent dust formation and destruction caused the
observed displacement of the initially faint components C and D and
of the bright cavity A from the star which has almost disappeared in
our images in 2001. Increasing dust optical depths are causing strong
backwarming that leads to higher temperatures in the dust formation
zone, displacing the latter outward with a velocity vT ~
27 km s-1 due to the evaporation of the recently formed
dust grains. This self-regulated shift of the dust density peak
in the bipolar shell mimics a rapid radial expansion, whereas the
actual outflow has probably a lower speed v < vinfty
~ 15 km s-1. The model predicts that the star will remain
obscured until dot {M} starts to drop back to lower values in the dust
formation zone; in a few years from that moment, we could be witnessing
the star reappearing.
Title: Diffraction-limited bispectrum speckle interferometry of the
Herbig Be star R Mon
Authors: Weigelt, G.; Balega, Y. Y.; Hofmann, K. -H.; Preibisch, T.
Bibcode: 2002A&A...392..937W
Altcode:
We explore the structures immediately surrounding the intermediate-mass
young stellar object R Mon with bispectrum speckle interferometry,
conventional near-infrared imaging and by analyzing optical HST
archive data. Our near-infrared speckle images with unprecedented
diffraction-limited resolution of 55 mas ( ~ 44 AU; H-band) and 76
mas ( ~ 61 AU; K-band) represent the highest resolution R Mon images
obtained so far and exhibit previously unseen complex structures. While
the binary companion R Mon B appears as an unresolved point source
in our speckle images, the image of the primary R Mon A is marginally
extended in the K-band and significantly extended in the H-band. The
most prominent new feature is a bright arc-shaped structure, pointing
away from R Mon in north-western direction. We interpret this feature as
the surface of a dense structure near the thick circumstellar disk or
torus around R Mon. Our images also reveal several twisted filaments
of helical shape which are similar to the twisted filaments in the
outer parts of the nebula. We identify structures which probably are
responsible for casting pronounced shadows in the outer regions of
the NGC 2261 reflection nebula. Finally, we discuss the relation of
the observed features, in particular the arc-shaped speckle feature,
to the wind and outflow activity (Herbig-Haro objects and jets)
of R Mon. Part of the results presented in this paper are based on
observations obtained at the German-Spanish Astronomical Centre, Calar
Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg,
jointly with the Spanish National Commission for Astronomy. The speckle
data were collected at the Special Astrophysical Observatory with the
6 m telescope.
Title: Bispectrum speckle interferometry of IRC
+10216: The dynamic evolution of the innermost circumstellar
environment from 1995 to 2001
Authors: Weigelt, G.; Balega, Y. Y.; Blöcker, T.; Hofmann, K. -H.;
Men'shchikov, A. B.; Winters, J. M.
Bibcode: 2002A&A...392..131W
Altcode: 2002astro.ph..6309W
We present new near-infrared (JHK) bispectrum speckle-interferometry
monitoring of the carbon star IRC+10216 obtained
between 1999 and 2001 with the SAO 6 m telescope. The J-, H-, and K-band
resolutions are 50 mas, 56 mas, and 73 mas, respectively. The total
sequence of K-band observations covers now 8 epochs from 1995 to 2001
and shows the dynamic evolution of the inner dust shell. The present
observations show that the appearance of the dust shell has considerably
changed compared to the epochs of 1995 to 1998. Four main components
within a 0\farcs2 radius can be identified in the K-band images. The
apparent separation of the two initially brightest components A and B
increased from ~ 191 mas in 1995 to ~ 351 mas in 2001. Simultaneously,
component B has been fading and almost disappeared in 2000 whereas the
initially faint components C and D became brighter (relative to peak
intensity). The changes of the images can be related to changes of the
optical depth caused, for instance, by mass-loss variations or new
dust condensation in the wind. Our recent two-dimensional radiative
transfer model of IRC +10216 suggests that the
observed relative motion of components A and B is not consistent with
the outflow of gas and dust at the well-known terminal wind velocity of
15 km s-1. The apparent motion with a deprojected velocity
of 19 km s-1 on average and of recently 27 km s-1
appears to be caused by a displacement of the dust density peak due to
dust evaporation in the optically thicker and hotter environment. The
present monitoring, covering more than 3 pulsation periods, shows that
the structural variations are not related to the stellar pulsation
cycle in a simple way. This is consistent with the predictions of
hydrodynamical models that enhanced dust formation takes place on a
timescale of several pulsation periods. The timescale of the fading
of component B can well be explained by the formation of new dust in
the circumstellar envelope.
Title: High-resolution study of the young stellar objects in Mon R2
IRS 3
Authors: Preibisch, T.; Balega, Y. Y.; Schertl, D.; Weigelt, G.
Bibcode: 2002A&A...392..945P
Altcode:
We present a bispectrum speckle interferometry study of the embedded
young stellar objects in Mon R2 IRS 3 in the near-infrared H and
K bands. Our images with a resolution of 75 mas (cor 62 AU) show a
close triple system surrounded by strong diffuse nebulosity and three
additional infrared sources (K magnitudes ~ 11.8-13.7) within 3''
of the brightest object IRS 3 A (K ~ 7.9). We use HST/NICMOS archive
images to derive near-infrared photometry for the sources and estimate
the stellar masses of the three brightest objects IRS 3 A, B, and C to
be in the range ~ 5-15 M_sun. IRS 3 A is surrounded by a bipolar nebula
(position angle ~ 30degr ), suggesting it to be embedded in a thick
circumstellar disk or a torus with polar cavities. IRS 3 B shows a
remarkable jet-like emission feature pointing towards the north-east
(position angle 50degr ). This feature consists of at least three
individual knots with projected separations of 130, 230, and 290 mas
(110, 190, and 240 AU) from IRS 3 B, which are much brighter in the
K band than in the H band. This strongly indicates outflow activity
from IRS 3 B, which is therefore probably the source of the compact
high velocity molecular outflow reported from Mon R2 IRS 3. We also
analyze Chandra X-ray archive data for the Mon R2 region and find
IRS 3 A and IRS 3 C to be sources of hard (3 - 10 keV) and variable
X-ray emission, suggesting plasma temperatures of at least 50 x
106 K. The similarity of the X-ray properties to those of
Class I protostars suggests magnetic interaction between the protostars
and their circumstellar disks to be the origin of the X-ray emission;
this provides indirect evidence for the presence of circumstellar
disks in the intermediate- to high-mass young stellar objects IRS 3
A and IRS 3 C.
Title: Bispectrum speckle interferometry of the Red
Rectangle: Diffraction-limited near-infrared images
reconstructed from Keck telescope speckle data
Authors: Tuthill, P. G.; Men'shchikov, A. B.; Schertl, D.; Monnier,
J. D.; Danchi, W. C.; Weigelt, G.
Bibcode: 2002A&A...389..889T
Altcode:
We present new near-infrared (2.1-3.3 mu m) images of the Red
Rectangle with unprecedented diffraction-limited angular
resolutions of 46-68 mas; 4 times higher than that of the Hubble
space telescope and almost a factor of two improvement over the
previous 6 m SAO telecope speckle images presented by Men'shchikov
et al. (\cite{Men'shchikov_etal1998}). The new images, which were
reconstructed from Keck telescope speckle data using the bispectrum
speckle interferometry method, clearly show two bright lobes
above and below the optically thick dark lane obscuring the central
binary. X-shaped spikes, thought to trace the surface of a biconical
flow, change the intensity distribution of the bright lobes, making
them appear broadened or with an east-west double-peak in images
with the highest resolution. The striking biconical appearance of
the Red Rectangle is preserved on scales from
50 mas to 1 arcmin and from the visible (red) to at least 10 mu m,
implying that large grains of at least several microns in size dominate
scattering. The new images supplement previous 76 mas resolution speckle
reconstructions at shorter wavelengths of 0.6-0.8 mu m (Osterbart
et al. \cite{Osterbart_etal1997}) and 0.7-2.2 mu m (Men'shchikov et
al. \cite{Men'shchikov_etal1998}), allowing a more detailed analysis
of the famous bipolar nebula. The intensity distribution of the images
is inconsistent with a flat disk geometry frequently used to model
the bipolar nebulae. Instead, a geometrically thick torus-like density
distribution with bipolar conical cavities is preferred. The extent of
the bright lobes indicates that the dense torus has a diameter of >~
100 AU, for an assumed distance of 330 pc. This torus may be the outer
reaches of a flared thick disk tapering inwards to the central star,
however such a density enhancement on the midplane is not strictly
required to explain the narrow dark lane obscuring the central stars.
Title: VizieR Online Data Catalog: Speckle interferometry of nearby
multiple stars (Balega+, 2002)
Authors: Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.; Maksimov,
A. F.; Pluzhnik, E. A.; Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2002yCat..33850087B
Altcode:
We present the results of diffraction-limited optical speckle
interferometry and infrared bispectrum speckle interferometry of
111 double and 10 triple systems performed in 1998-1999 with the 6-m
telescope of the Special Astrophysical Observatory in Zelenchuk. The
observations concentrated on nearby close binaries discovered during the
Hipparcos mission. Many nearby fast-orbiting low-mass binaries known
before Hipparcos were also included in the program. New companions
were first resolved in 4 systems: HIP 5245, ADS 3179, Kui99, and ADS
16138. In addition to accurate relative positions, magnitude differences
were measured for most of the pairs. We combined our results with the
Hipparcos parallaxes to derive absolute magnitudes and spectral types
for 63 binaries and 4 triples. Preliminary orbital elements and the
mass-sum are derived for HIP 689, and improved orbits are presented
for HIP 16602 (CHR117) and HIP 21280 (CHR17). (3 data files).
Title: Speckle interferometry of nearby multiple stars
Authors: Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.; Maksimov,
A. F.; Pluzhnik, E. A.; Schertl, D.; Shkhagosheva, Z. U.; Weigelt, G.
Bibcode: 2002A&A...385...87B
Altcode:
We present the results of diffraction-limited optical speckle
interferometry and infrared bispectrum speckle interferometry of
111 double and 10 triple systems performed in 1998-1999 with the 6-m
telescope of the Special Astrophysical Observatory in Zelenchuk. The
observations concentrated on nearby close binaries discovered during the
Hipparcos mission. Many nearby fast-orbiting low-mass binaries known
before Hipparcos were also included in the program. New companions
were first resolved in 4 systems: HIP 5245, ADS 3179, Kui 99, and
ADS 16138. In addition to accurate relative positions, magnitude
differences were measured for most of the pairs. We combined our
results with the Hipparcos parallaxes to derive absolute magnitudes
and spectral types for 63 binaries and 4 triples. Preliminary orbital
elements and the mass-sum are derived for HIP 689, and improved orbits
are presented for HIP 16602 (CHR 117) and HIP 21280 (CHR 17). Based
on data collected at the Special Astrophysical Observatory, Russia
Table 1 is only, and Table 2 also, available in electronic form at
the CDS via anonymons ftp to cdsarc.u-strasbg.fr (130.79.128.5) or
via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/385/87
Title: The Potential of an Extension of Amber to the Visible
Authors: Petrov, Romain G.; Stee, Philippe; Weigelt, Gerd; Mourard,
Denis; Vakili, Farrokh; Jankov, Slobodan; Mathias, Philippe; Lagarde,
Stephane; Robbe-Dubois, Sylvie; Foy, Renaud
Bibcode: 2002sdef.conf..320P
Altcode:
We discuss some of the scientific goals of a visible VLTI instrument. An
instrument for the ATs only would already represent an important
progress for the study of stellar physics. It could be a very
straightforward, and therefore relatively cheap and fast, extension
of the currently built infrared VLTI instrument AMBER. Accessing to
the extra galactic programs, like AGN, would require using the UTs
for fringe tracking and therefore operating the instrument in multi
speckle mode. GI2T/Regain has indicated one potential solution to
combine this two problematics.
Title: Bispectrum speckle interferometry of IRC +10 216: the dynamic
evolution of the circumstellar environment from 1995 to 2001.
Authors: Weigelt, G.; Bloecker, T.; Hofmann, K. -H.; Men'shchikov,
A.; Winters, J. M.; Balega, Y. Y.
Bibcode: 2002AGAb...19R..89W
Altcode:
No abstract at ADS
Title: Bispectrum speckle interferometry of young jet- and
outflow-sources.
Authors: Preibisch, T.; Schertl, D.; Weigelt, G.; Balega, Y.
Bibcode: 2002AGAb...19...24P
Altcode:
No abstract at ADS
Title: Diffraction-limited bispectrum speckle interferometry of the
Herbig Be star R Mon.
Authors: Weigelt, G.; Hofmann, K. -H.; Preibisch, T.; Balega, Y.
Bibcode: 2002AGAb...19Q..91W
Altcode:
No abstract at ADS
Title: Observations of Mira stars with the IOTA/FLUOR interferometer
and comparison with Mira star models
Authors: Hofmann, K. -H.; Beckmann, U.; Blöcker, T.; Foresto,
V. Coudé du; Lacasse, M.; Mennesson, B.; Millan-Gabet, R.; Morel, S.;
Perrin, G.; Pras, B.; Ruilier, C.; Schertl, D.; Schöller, M.; Scholz,
M.; Shenavrin, V.; Traub, W.; Weigelt, G.; Wittkowski, M.; Yudin, B.
Bibcode: 2002NewA....7....9H
Altcode: 2002astro.ph..6406H
We present K'-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR
fiber optics beam combiner, which provides high-accuracy visibility
measurements in spite of time-variable atmospheric conditions. For the
M-type Miras X Oph, R Aql, RU Her, R Ser, and the C-type Mira V CrB we
derived the uniform-disk diameters 11.7 mas, 10.9 mas, 8.4 mas, 8.1
mas, and 7.9 mas (±0.3 mas), respectively. Simultaneous photometric
observations yielded the bolometric fluxes. The derived angular
Rosseland radii and the bolometric fluxes allowed the determination of
effective temperatures. For instance, the effective temperature of R
Aql was determined to be 2970 ±110 K. A linear Rosseland radius for R
Aql of 250 +100-60 R ⊙ was derived
from the angular Rosseland radius of 5.5±0.2 mas and the HIPPARCOS
parallax of 4.73±1.19 mas. The observations were compared with
theoretical Mira star models of Bessel et al. [A&A 307 (1996) 481]
and Hofmann et al. [A&A 339 (1998) 846]. The effective temperatures
of the M-type Miras and the linear radius of R Aql indicate fundamental
mode pulsation.
Title: Spectro-interferometry of the Mira star T Cep with the IOTA
interferometer and comparison with models.
Authors: Weigelt, G.; Beckmann, U.; Bloecker, T.; Hofmann, K. -H.;
Ohnaka, K.; Schertl, D.; Brewer, M. K.; Schloerb, F.; Efimov, Y. N.;
Shenavrin, V.; Yudin, B.; Berger, J.; Lacasse, M.; Millan-Gabet, R.;
Monnier, J.; Morel, S.; Pedretti, E.; Traub, W.; Malanushenko, V.;
Mennesson, B.; Scholz, M.
Bibcode: 2002AGAb...19R..94W
Altcode:
No abstract at ADS
Title: Bispectrum speckle interferometry of the massive protostellar
object S140 IRS 1: Evidence for multiple outflows
Authors: Weigelt, G.; Balega, Y. Y.; Preibisch, T.; Schertl, D.;
Smith, M. D.
Bibcode: 2002A&A...381..905W
Altcode:
Bispectrum speckle interferometry is employed to explore the immediate
environment of the deeply embedded young stellar object S140 IRS 1. A
K'-band (2.0-2.3 mu m) diffraction-limited resolution of 76 mas ( ~
70 AU) is achieved with the SAO 6 m telescope, as well as a dynamical
range of more than 8 mag and a field of view of 13'' x 21''. Our image
exhibits many previously unseen complex structures. In addition to the
bright, elongated, and very clumpy feature pointing from the central
source to the south-east, which was already discussed in a previous
paper (Schertl et al. \cite{Schertl00}), we find several arc-like
structures north-east of IRS 1, extended diffuse emission south of IRS
1, and four new point sources. The diffuse and fragmentary structures
close to IRS 1 appear to trace circumstellar material swept up by
energetic outflows. In combination with molecular line emission maps
from the literature, our image provides direct confirmation that two
distinct bipolar outflow systems continue to be driven from IRS 1 on
scales between 3\arcsec and 100\arcsec. A system of three arc-like
structures to the north-east is consistent with cavities excavated by
a precessing jet or wind-driven outflow. We discuss the implications
for the nature of the central source. Based based on observations
obtained at the Special Astrophysical Observatory with the 6 m telecope.
Title: Near-infrared IOTA interferometry of the symbiotic star CH Cyg.
Authors: Hofmann, K. -H.; Beckmann, U.; Bloecker, T.; Ohnaka, K.;
Schertl, D.; Weigelt, G.; Brewer, M. K.; Schloerb, F.; Efimov, Y. N.;
Shenavrin, V.; Yudin, B.; Berger, J.; Lacasse, M.; Millan-Gabet, R.;
Monnier, J.; Morel, S.; Pedretti, E.; Traub, W.; Malanushenko, V.;
Mennesson, B.; Scholz, M.
Bibcode: 2002AGAb...19R..91H
Altcode:
No abstract at ADS
Title: IOTA observation of the circumstellar envelope of R CrB.
Authors: Ohnaka, K.; Beckmann, U.; Malanushenko, V.; Schertl, D.;
Weigelt, G.; Hofmann, K. -H.; Ahearn, A.; Berger, J. -P.; Lacasse,
M.; Millan-Gabet, R.; Monnier, J.; Traub, W.; Brewer, M.; Schloerb,
P.; Shenavrin, V.; Yudin, B.
Bibcode: 2002AGAb...19Q..89O
Altcode:
No abstract at ADS
Title: Bispectrum speckle interferometry of the B[e] star MWC 349A.
Authors: Hofmann, K. -H.; Ikhsanov, N. R.; Weigelt, G.; Miroshnichenko,
A. S.
Bibcode: 2002AGAb...19Q..92H
Altcode:
No abstract at ADS
Title: Diffraction-limited speckle interferometry and modeling of
the circumstellar envelope of R CrB at maximum and minimum light
Authors: Ohnaka, K.; Balega, Y.; Blöcker, T.; Efimov, Y. S.; Hofmann,
K. -H.; Ikhsanov, N. R.; Shenavrin, V. I.; Weigelt, G.; Yudin, B. F.
Bibcode: 2001A&A...380..212O
Altcode: 2002astro.ph..1049O
We present the first speckle interferometric observations of R
CrB, the prototype of a class of peculiar stars which undergo
irregular declines in their visible light curves. The observations
were carried out with the 6 m telescope at the Special Astrophysical
Observatory near maximum light (V=7, 1996 Oct. 1) and at minimum light
(V=10.61, 1999 Sep. 28). A spatial resolution of 75 mas was achieved
in the K-band. The dust shell around R CrB is partially resolved,
and the visibility is approximately 0.8 at a spatial frequency of
10 cycles/arcsec. The two-dimensional power spectra obtained at
both epochs do not show any significant deviation from circular
symmetry. The visibility function and spectral energy distribution
obtained near maximum light can be simultaneously fitted with a model
consisting of the central star and an optically thin dust shell with
density proportional to r-2. The inner boundary of the
shell is found to be 82 Rstar (19 mas) with a temperature
of 920 K. However, this simple model fails to simultaneously reproduce
the visibility and spectral energy distribution obtained at minimum
light. We show that this discrepancy can be attributed to thermal
emission from a newly formed dust cloud.
Title: Speckle interferometry and radiative transfer modelling of
the Wolf-Rayet star WR 118
Authors: Yudin, B.; Balega, Y.; Blöcker, T.; Hofmann, K. -H.; Schertl,
D.; Weigelt, G.
Bibcode: 2001A&A...379..229Y
Altcode: 2001astro.ph.10132Y
WR 118 is a highly evolved Wolf-Rayet star of
the WC10 subtype surrounded by a permanent dust shell absorbing and
re-emitting in the infrared a considerable fraction of the stellar
luminosity. We present the first diffraction-limited 2.13 mu m
speckle interferometric observations of WR 118
with 73 mas resolution. The speckle interferograms were obtained
with the 6 m telescope at the Special Astrophysical Observatory. The
two-dimensional visibility function of the object does not show any
significant deviation from circular symmetry. The visibility curve
declines towards the diffraction cut-off frequency to ~ 0.66 and can be
approximated by a linear function. Radiative transfer calculations have
been carried out to model the spectral energy distribution, given in the
range of 0.5-25 mu m, and our 2.13 mu m visibility function, assuming
spherical symmetry of the dust shell. Both can be fitted with a model
containing double-sized grains (``small'' and ``large'') with the radii
of a = 0.05 mu m and 0.38 mu m, and a mass fraction of the large grains
greater than 65%. Alternatively, a good match can be obtained with the
grain size distribution function n(a) ~ a-3, with a ranging
between 0.005 mu m and 0.6 mu m. At the inner boundary of the modelled
dust shell (angular diameter Thetain = (17 +/- 1) mas),
the temperature of the smallest grains and the dust shell density are
1750 K +/- 100 K and (1 +/- 0.2) x 10-19 g/cm3,
respectively. The dust formation rate is found to be (1.3 +/- 0.5)
x 10-7 Msun/yr, assuming Vwind =
1200 km s-1.
Title: High-resolution near-infrared study of the deeply embedded
young stellar object S140 IRS 3
Authors: Preibisch, T.; Balega, Y. Y.; Schertl, D.; Smith, M. D.;
Weigelt, G.
Bibcode: 2001A&A...378..539P
Altcode:
We explore the structures immediately surrounding the high-mass young
stellar object S140 IRS 3 within the L1204 molecular cloud. We have
obtained a bispectrum speckle interferometric K-band image with a
resolution of 150 mas and a seeing-limited molecular hydrogen line
emission image of IRS 3. Our speckle image resolves IRS 3 into three
point sources, a close binary with separation 0.63'' and a third
component 1.3'' away. A rough assessment of the system stability
suggests that the IRS 3 triple system is unstable. Our speckle image
also reveals extended diffuse emission of very complex morphology
around IRS 3. An extended diffuse feature north-east of IRS 3 displays
a remarkable sf S-shaped structure. This feature is the innermost part
of an at least 15'' long extended structure, which is pointing towards
a bow-shock like patch located 90'' away from IRS 3. We find strong H_2
line emission associated with this feature, suggesting the presence of
shocks, caused by the collision of outflowing material with the ambient
medium. The sf S-shaped structure of this feature can be well reproduced
by a model assuming a precessing outflow from IRS 3a. Furthermore,
we find several elongated features pointing away from IRS 3 in a
southern direction. Some of these features also exhibit strong H_2
line emission, demonstrating that IRS 3 drives outflows in several
directions. Part of the results presented in this paper are based on
observations obtained at the German-Spanish Astronomical Centre, Calar
Alto, operated by the Max-Planck-Institute for Astronomy, Heidelberg,
jointly with the Spanish National Commission for Astronomy. The speckle
observations were collected at the Special Astrophysical Observatory
with the 6 m telecope.
Title: A multi-wavelength study of the oxygen-rich AGB star
CIT 3: Bispectrum speckle interferometry and
dust-shell modelling
Authors: Hofmann, K. -H.; Balega, Y.; Blöcker, T.; Weigelt, G.
Bibcode: 2001A&A...379..529H
Altcode: 2001astro.ph.10108H
CIT 3 is an oxygen-rich long-period variable evolving along the
Asymptotic Giant Branch and is one of the most extreme infrared AGB
objects. Due to substantial mass loss it is surrounded by an optically
thick dust shell which absorbs almost all visible light radiated
by the star and finally re-emits it in the infrared regime. We
present the first near infrared bispectrum speckle-interferometry
observations of CIT 3 in the J-, H-, and K'-band. The J-,
H-, and K'-band resolution is 48 mas, 56 mas, and 73 mas,
resp. The interferograms were obtained with the Russian 6 m telescope
at the Special Astrophysical Observatory. While CIT 3 appears almost
spherically symmetric in the H- and K'-band it is clearly
elongated in the J-band along a symmetry axis of position angle
-28degr . Two structures can be identified: a compact elliptical core
and a fainter north-western fan-like structure. The eccentricity
of the elliptical core, given by the ratio of minor to major axis,
is approximately varepsilon =123 mas/154 mas = 0.8. The full opening
angle of the fan amounts to approximately 40degr . Extensive radiative
transfer calculations have been carried out and confronted with the
observations taking into account the spectral energy distribution
ranging from 1 mu m to 1 mm, our near-infrared visibility functions
at 1.24 mu m, 1.65 mu m and 2.12 mu m, as well as 11 mu m ISI
interferometry. The best model found to match the observations refers
to a cool central star with Teff=2250 K which is surrounded
by an optically thick dust shell with tau (0.55 mum ) = 30. The models
give a central-star diameter of Theta *=10.9 mas and an
inner dust shell diameter of Theta 1=71.9 mas being in line
with lunar occultation observations. The inner rim of the dust-shell
is located at r1= 6.6 R* and has a temperature
of T1=900 K. The grain sizes were found to comply with a
grain-size distribution according to Mathis et al. (\cite{MRN77})
with n(a) ~ a-3.5, and 0.005 mu m <= a <= 0.25
mu m. Uniform outflow models, i.e. density distributions with rho ~
1/r2, turned out to underestimate the flux beyond 20 mu m. A
two-component model existing of an inner uniform-outflow shell region
(rho ~ 1/r2) and an outer region where the density declines
more shallow as rho ~ 1/r1.5 proved to remove this flux
deficiency and to give the best overall match of the observations. The
transition between both density distributions is at r2 = 20.5
r1= 135.7 R* where the dust-shell temperature has
dropped to T2 = 163 K. Provided the outflow velocity kept
constant, the more shallow density distribution in the outer shell
indicates that mass-loss has decreased with time in the past of CIT
3. Adopting vexp=20 km s-1, the termination of
that mass-loss decrease and the begin of the uniform-outflow phase took
place 87 yr ago. The present-day mass-loss rate can be determined to be
dot M = (1.3-2.1) x 10-5 Msun/yr for d=500-800 pc.
Title: Multi-wavelength bispectrum speckle interferometry of R Leo
and comparison with Mira star models
Authors: Hofmann, K. -H.; Balega, Y.; Scholz, M.; Weigelt, G.
Bibcode: 2001A&A...376..518H
Altcode:
We present diffraction-limited (30 mas resolution) bispectrum speckle
interferometry of the Mira star R Leo with the 6 m SAO telescope. The
speckle interferograms were recorded through narrow-band interference
filters with centre wavelength/bandwidth of 673 nm/8 nm (strong TiO
absorption band), 656 nm/10 nm, 699 nm/6 nm and 781 nm/14 nm (moderate
TiO absorption), 754 nm/6 nm (weak TiO absorption), and 1045 nm/9 nm
(continuum). The reconstructed images show that the average uniform-disk
diameters of R Leo are 60.6 mas +/- 3.0 mas at 656 nm, 75.6 mas +/-
3.7 mas at 673 nm, 52.5 mas +/- 2.5 mas at 699 nm, 48.7 mas +/- 2.3
mas at 754 nm, 55.0 mas +/- 2.7 mas at 781 nm, and 37.9 mas +/- 4.0
mas at 1045 nm. In all six observed wavelength bands the shape of R Leo
shows no significant asymmetry. We compare our observations with Mira
star models and check the ability of monochromatic linear diameters
for discriminating between model representations of the observed
star. Monochromatic tau lambda =1 radii were derived from the
observed visibilities by application of model-predicted center-to-limb
variations of the intensity. Adopting the HIPPARCOS parallax we derived
from the 1045 nm-observation a photospheric radius (Rosseland tau_Ross
=1 radius) of R Leo of 417 Rsun +/- 97 Rsun
(19.2 mas +/- 2.0 mas) indicating pulsation in the first-overtone
mode. From JHKL photometry and the angular photospheric radius an
effective temperature of 2590 +/- 180 K at near maximum phase was
obtained. Based on observations collected at the SAO 6 m telescope
in Russia.
Title: AGB and Post-AGB Evolution: Structural and Chemical Changes
Authors: Blöcker, T.; Osterbart, R.; Weigelt, G.; Balega, Y.;
Men'shchikov, A.
Bibcode: 2001ASSL..265..241B
Altcode: 2001astro.ph..2383B; 2001pao..conf..241B
Structural and chemical changes during the AGB and post-AGB evolution
are discussed with respect to two recent observational and theoretical
findings. On the one hand, high-resolution infrared observations
revealed details of the dynamical evolution of the fragmented,
bipolar dust shell around the far-evolved carbon star IRC+10216
giving evidence for rapid changes of an already PPN-like structure
during the very end of the AGB evolution. On the other hand, stellar
evolution calculations considering convective overshoot have shown
how thermal pulses during the post-AGB stage lead to the formation of
hydrogen-deficient post-AGB stars with abundance patterns consistent
with those observed for Wolf-Rayet central stars.
Title: Structure and properties of IRC+10216
Authors: Men'shchikov, Alexander B.; Balega, Yuri Yu.; Blöcker,
Thomas; Osterbart, Roger; Weigelt, Gerd
Bibcode: 2001ASSL..265..343M
Altcode: 2001pao..conf..343M
We present selected results of the first detailed, two-dimensional
radiative transfer modeling of the dusty envelope around the carbon
star IRC+10216. The model reproduces very well the entire beam-matched
spectral energy distribution of IRC+10216 from optical to centimeter
wavelengths (at several phases of stellar luminosity), observed
intensity profiles of the object at 1.25, 2.2, 10.5, 50, 100 microns,
and 1.3 mm, a 10.5 micron lunar occultation intensity profile, our
high-resolution J, H, K, and H-K bispectrum speckle-interferometry
images, and visibilities in J, H, K, L, M, and N bands. We present a
new, accurate identification of the carriers of the well-known 11.3
micron and 30 micron dust features in the spectrum of IRC+10216. The
dust model found in this study can also be successfully applied
to some other carbon stars exhibiting broad emission features in
the 10.3--12.6 micron and 25--37 micron wavelength regions. A firm
result of our modeling is that the brightest compact near-infrared
peak observed in IRC+10216 is not the direct light from the underlying
star. In contrast to previous suggestions, it is the radiation emitted
and scattered in the optically thinner southern outflow cavity of a
bipolar dense shell moving away from the central star.
Title: The Dust Envelope of R Cas
Authors: Weigelt, G.; Yudin, B. F.
Bibcode: 2001ARep...45..510W
Altcode:
The spectral energy distribution in the far infrared and the
shape of a broad emission band in the spectrum of R Cas at 9 13
µm can be reproduced in a model with a dust envelope consisting of
approximately half amorphous olivine (Mg0.8Fe1.2SiO4) and half amorphous
aluminum-oxide grains (Al2O3), with a small admixture of spinel grains
(MgAl2O4). The dust envelope’s optical depth τ(50 µm) is ≈5×10-3
[τ(1.25 µm)≈0.07 for a gr≈0.05 µm], and its mass within r≤0.025
pc M dust is ≈8×10-6 M ⊙. The index α in the power-law radial
dust distribution, n d ∝(R +/r)α, is ≈1.8. Over the last several
thousand years, the mass-loss rate of R Cas has been decreasing as &
$dot M(t) ~ t(0.2) ; (where time is measured backward from
the present). This probably implies that R Cas experienced a thermal
helium flare several thousand years ago. If M gas/M dust≈200 (where
M gas is the gas mass), the mean mass-loss rate of the star is &
dot M ≈ 6 × 10({) - 7} M_ ⊙ /yr$ ; .
Title: Gliese 569B: A Young Multiple Brown Dwarf System?
Authors: Kenworthy, Matthew; Hofmann, Karl-Heinz; Close, Laird; Hinz,
Phil; Mamajek, Eric; Schertl, Dieter; Weigelt, Gerd; Angel, Roger;
Balega, Yuri Y.; Hinz, Joannah; Rieke, George
Bibcode: 2001ApJ...554L..67K
Altcode: 2001astro.ph..5157K
The nearby late M star Gliese 569B was recently found by adaptive optics
imaging to be a double with separation ~1 AU. To explore the orbital
motion and masses, we have undertaken a high-resolution (~0.05")
astrometric study. Images were obtained over 1.5 yr with bispectrum
speckle interferometry at the 6.5 m Multiple Mirror Telescope (MMT) and
6 m Special Astrophysical Observatory telescope. Our data show motion
corresponding to more than half the orbital period and constrain the
total mass to be greater than 0.115 Msolar, with a most
probable value of 0.145 Msolar. Higher masses cannot be
excluded without more extended observations, but from statistical
analysis we find an 80% probability that the total mass is less than
0.21 Msolar. An infrared spectrum of the blended B double
obtained with the MMT has been modeled as a blend of two different
spectral types, chosen to be consistent with the measured J- and K-band
brightness difference of a factor of ~2. The blended fit is not nearly
as good as that to a pure M8.5+ template. Therefore, we hypothesize
that the brighter component likely has two unresolved components with
near equal masses, each the same as the fainter component. If Gl 569B
is a triple, our dynamical limits suggest each component has a mass of
50+23-4 MJup. We infer an age for the
system of 300 Myr from its kinematic motion, which places it as a member
of the Ursa Major moving group. All the above parameters are consistent
with the latest DUSTY evolution models for brown dwarfs. Some of the
observations reported here were obtained at the MMT Observatory, a joint
facility of the University of Arizona and the Smithsonian Institution.
Title: Infrared Observations of the Star R Cas
Authors: Nadzhip, A. E.; Tatarnikov, A. M.; Shenavrin, V. I.; Weigelt,
G.; Yudin, B. F.
Bibcode: 2001AstL...27..324N
Altcode:
We present our JHKLM photometry for R Cas performed during
1988-2000. The pulsation period of R Cas is P = 429.6 days, with the
maximum IR brightness lagging behind the maximum visual brightness
by 0.2 P. The amplitude of light variations appreciably decreases
with increasing wavelength at lambda < 3 micrometers. At lambda
> 3 micrometers, this decrease virtually ceases. There is a step
on the ascending branch of IR JHK brightness. The K-L color index
increases linearly with K magnitude: KL = 0.304 K + 1.20 mag. The
color temperature dependence, T_{K-L} = f(K), is also linear: T_{K-L}
= (-622 K + 1100) K. In going from minimum to maximum, the K flux (as
well as the bolometric flux) from the star and its color temperature
T_{K-L} increase by a factor of 2.2 and 1.3, respectively.
Title: Principle and potential of the near infrared VLTI focal
instrument AMBER
Authors: Petrov, Romain G.; Malbet, Fabien; Weigelt, Gerd; Lisi,
Franco; Puget, Pascal; Antonelli, Pierre; Beckman, Udo; Lagarde,
Stéphane; Le Coarer, Etienne; Robbe-Dubois, Sylvie; Rousselet-Perraut,
Karine; Martinot-Lagarde, Grégoire; Dugué, Michel
Bibcode: 2001sf2a.conf..615P
Altcode:
AMBER is the first general user near infrared VLTI focal instrument. It
combines low and middle resolution spectroscopy with some imaging
capability thanks to the measure of phase closures between three
telescopes. It is optimized for high accuracy measurements thanks to
a spatial filtering of each beam using single mode fibers. The poster
presents AMBER main characteristics, discusses its potential and lists
some of its scientific programs.
Title: Computer simulations of interferometric imaging with the
Very Large Telescope Interferometer and its Astronomical Multibeam
Recombiner instrument
Authors: Przygodda, Frank; Bloecker, Thomas; Hofmann, Karl-Heinz;
Weigelt, Gerd
Bibcode: 2001OptEn..40..753P
Altcode: 2001astro.ph..2030P
We present computer simulations of interferometric imaging with
the Very Large Telescope Interferometer (VLTI) of the European
Southern Observatory and the Astronomical Multibeam Recombiner
(AMBER) phase-closure instrument. These simulations include both
the astrophysical modeling of a stellar object by radiative-transfer
calculations and the simulation of light propagation from the object to
the detector (through atmosphere, telescopes, and the AMBER instrument),
simulation of photon noise and detector readout noise, and finally data
processing of the interferograms. The results show the dependence of
the visibility error bars on the following observational parameters:
different seeing during the observation of object and reference star
(Fried parameters r0,object and r0,ref ranging
between 0.9 and 1.2 m), different residual tip-tilt error ((delta)
tt,object and (delta) tt,ref ranging between
0.1% and 20% of the Airy-disk diameter), and object brightness
(Kobject equals 0.7 to 10.2 mag, Kref equals
0.7 mag). As an example, we focus on stars in late stages of stellar
evolution and study one of the key objects of that kind, the dusty
super-giant IRC + 10420, which is rapidly evolving on human time
scales. We show computer simulations of VLT interferometer (visibility
and phase-closure measurements) of IRC + 10420 with two and three
auxiliary telescopes (in AMBER wide-field mode, i.e., without fiber
optic spatial filters) and discuss whether the visibility accuracy
is sufficient to distinguish between different theoretical model
predictions.
Title: Bispectrum speckle interferometry observations and
radiative transfer modelling of the red supergiant NML
Cyg. Multiple dust-shell structures evidencing previous
superwind phases
Authors: Blöcker, T.; Balega, Y.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2001A&A...369..142B
Altcode: 2001astro.ph..2092B
NML Cyg is a highly evolved OH/IR supergiant, one
of the most prominent infrared objects due to its strong obscuration
by dust, and supposed to be among the most luminous supergiants
in the galaxy. We present the first diffraction-limited 2.13 mu m
observations of NML Cyg with 73 mas resolution. The
speckle interferograms were obtained with the 6 m telescope at the
Special Astrophysical Observatory, and the image reconstruction is
based on the bispectrum speckle-interferometry method. The visibility
function declines towards the diffraction limit to ~ 0.6. Radiative
transfer calculations have been carried out to model the spectral energy
distribution, given by ground-based photometry and ISO spectroscopy, and
our 2.13 mu m visibility function. Additionally, mid-infrared visibility
functions at 11 mu m were considered. The observed dust shell properties
do not appear to be in accordance with standard single-shell (uniform
outflow) models but seem to require multiple components. Considering
previous periods of enhanced mass-loss, various density enhancements
in the dust shell were taken into account. An extensive grid of
models was calculated for different locations and strenghts of such
superwind regions in the dust shell. To match the observations from
the optical to the sub-mm domain requires at least two superwind
regions embedded in the shell. The best model includes a dust shell
with a temperature of 1000 K at its inner radius of 6.2 R*,
a close embedded superwind shell extending from 15.5 R* to
21.7 R* with an amplitude (factor of density enhancement)
of 10, and a far-out density enhancement at 186 R* with an
amplitude of 5. The angular diameters of the central star and of the
inner rim of the dust shell amount to 16.2 mas and 105 mas, resp. The
diameter of the embedded close superwind region extends from 263 mas
to 368 mas, and the inner boundary of the distant superwind region has
a diameter of 3\farcs 15. In the near-infrared the dust condensation
zone is limb-brightened leading to a corresponding ring-like intensity
distribution. The grain sizes, a, were found to be in accordance
with a standard distribution function, n(a) ~ a-3.5,
with a ranging between a_min=0.005 mu m and a_max = 0.15 mu m. The
bolometric flux amounts to F_bol = 3.63 10-9 Wm-2
corresponding to a central-star luminosity of L/Lsun =
1.13 105 * (d/kpc)2. Within the various parts
of the dust shell, 1/r2 density distributions could be
maintained differing only in their amplitude A. A slight improvement
of the far-infrared properties can be obtained if a shallower density
distribution of rho ~ 1/r1.7 is considered in the distant
superwind region. The present-day mass-loss rate was determined to be
dot {M} = 1.2 10-4 Msun/yr. The inner embedded
superwind shell corresponds to a phase of enhanced mass-loss (with
amplitude 10) in the immediate history of NML Cyg
which began 59 yr ago and lasted for ~ 18 yr. Correspondingly, the outer
superwind region is due to to a high mass-loss period (amplitude 5)
which terminated 529 yr ago.
Title: Structure and physical properties of the rapidly evolving
dusty envelope of IRC +10 216 reconstructed by
detailed two-dimensional radiative transfer modeling
Authors: Men'shchikov, A. B.; Balega, Y.; Blöcker, T.; Osterbart,
R.; Weigelt, G.
Bibcode: 2001A&A...368..497M
Altcode:
We present the first detailed, two-dimensional radiative transfer
model of the dusty envelope around the carbon star IRC +10
216. Our goal was to find a self-consistent model of the
star and its envelope which takes into account as many observational
constraints as possible. The model reproduces very well the entire
beam-matched spectral energy distribution of IRC +10
216 from optical to centimeter wavelengths (at several
phases of stellar luminosity), observed intensity profiles of the
object at 1.25, 2.2, 10.5, 50, 100 μ m, and 1.3 mm, a 10.5 μ m lunar
occultation intensity profile, our high-resolution J, H, K, and H -
K bispectrum speckle-interferometry images, and visibilities in J, H,
K, L, M, and N bands. For the adopted distance of 130 pc, the model
of IRC +10 216 implies that the object changes
its luminosity between 13 000 and 5200 Lsun, its effective
temperature between 2800 and 2500 K, and its radius between 500 and 390
Rsun. There is a dense non-spherical dust shell around the
star, with outflow cavities at position angle PA ~ 20°. The southern
cavity with a full opening angle of 36° is tilted toward us by 40°
from the plane of sky, causing the observed bipolar appearance of the
object on a subarcsecond scale. If the envelope's outflow velocity
of 15 km s-1 applies to the material making up the dense
core, then just ~ 15 years ago the star was losing mass at a rate of
9 x; 10-5 Msun yr-1. Dust exists in
the envelope of IRC +10 216 everywhere from the
stellar photosphere up to a distance of 3 pc from the star. The total
mass of the envelope lost by the central star is 3 Msun
and the dust-to-gas mass ratio is 0.004. The total optical depth tau
V toward the star in the visual is 40, in the polar cavities
it is 10. The innermost parts of the envelope are optically thick even
at 10.7 μ m due to a strong resonance absorption of silicon carbide
grains at that wavelength. In addition to SiC dust, the model contains
inhomogeneous grains made of a mixture of SiC and incompletely amorphous
carbon with thin [Mg0.5Fe0.5]S mantles. This
is the simplest dust mixture required to fit all observations of
IRC +10 216 and to correctly interpret the well-known
11.3 μ m and 27 μ m emission bands. The dust model found in this
study can also be successfully applied to many other carbon stars
exhibiting broad emission features in the 10.3-12.6 μ m and 25-37 μ m
wavelength regions. An important and firm result of our modeling is that
the brightest compact peak observed in IRC +10 216
is not the direct light from the underlying central star. In contrast
to previous suggestions, the brightest southern component, labeled A
in our high-resolution near-infrared images \citep{Weigelt_etal1998a,
Weigelt_etal1998b,Osterbart_etal2000}, is only the radiation emitted
and scattered in the optically thinner southern cavity of the bipolar
dense shell moving away from the central star. The carbon star is at
the position of the fainter component B in our H and K images, which
is 0\farcs21 away from A along the symmetry axis. Direct stellar light
(component B) is not seen at all in the Hubble Space Telescope 0.8 μ
m and 1.1 μ m images, being absorbed by the dense dusty material. The
even fainter components C and D in the H and K images are probably
due to smaller deviations of the dense shell from the spherical
shape. IRC +10 216 seems to have entered a phase
immediately before moving off the asymptotic giant branch and started
developing asymmetries in its envelope.
Title: Infrared Speckle Interferometry of Eleven Binaries Using a
Bispectral Analysis
Authors: Balega, I. I.; Balega, Yu. Yu.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2001AstL...27...95B
Altcode:
Infrared speckle-masking observations of eleven binary systems with
the 6-m Special Astrophysical Observatory telescope are presented. A
resolution of 43 mas in J (1.25 micrometer) and 76 mas in K (2.2
micrometers) has been achieved in reconstructed images. Accurate
magnitude differences, separations, and position angles have been
determined for all the resolved binaries. The pair HR 1071 with an
abnormally low lithium abundance is considered in more detail.
Title: High-resolution Near-infrared Study of the Deeply Embedded
Young Stellar Object S140 IRS 3
Authors: Preibisch, Thomas; Schertl, Dieter; Weigelt, Gerd; Balega,
Yuri Y.; Smith, Michael D.
Bibcode: 2001AGM....18..P22P
Altcode: 2001AGAb...18Q.146P
We explore the structures immediately surrounding the high-mass young
stellar object S140 IRS 3 within the L1204 molecular cloud. We have
obtained a bispectrum speckle interferometric K-band image with a
resolution of 150 mas and a seeing-limited molecular hydrogen line
emission image of IRS 3. Our speckle image resolves IRS 3 into three
point sources, a close binary with separation 0.63'' and a third
component 1.3'' away. A rough assessment of the system stability
suggests that the IRS 3 triple system is unstable. Our speckle image
also reveals extended diffuse emission of very complex morphology
around IRS 3. An extended diffuse feature north-east of IRS 3 displays
a remarkable S-shaped structure. This feature is the innermost part of
an at least 15'' long extended structure, which is pointing towards
a bow-shock like patch located 90'' away from IRS 3. We find strong
H2 line emission associated with this feature, suggesting
the presence of shocks, caused by the collision of outflowing material
with the ambient medium. The S-shaped structure of this feature can
be well reproduced by a model assuming a precessing outflow from IRS
3a. Furthermore, we find several elongated features pointing away from
IRS 3 in a southern direction. Some of these features also exhibit
strong H2 line emission, demonstrating that IRS 3 drives
outflows in several directions.
Title: A Multiwavelength Study of the AGB star CIT 3: Bispectrum
Speckle Interferometry and Dust-shell Modelling
Authors: Hofmann, K. -H.; Blöcker, T.; Weigelt, G.; Balega, Y. Y.
Bibcode: 2001AGM....18..P99H
Altcode: 2001AGAb...18R.184H
CIT 3 (= WX Psc = IRC +10 011 = IRAS 01037+1219), an oxygen-rich
long-period variable evolving along the Asymptotic Giant Branch
(AGB), is one of the most extreme infrared AGB objects. This M9-10
star suffers currently from mass-loss rates close to 10-5
Msolar/yr and is surrounded by an optically thick dust
shell which absorbs almost all visible light radiated by the star
and finally re-emits it in the infrared regime. We present the first
bispectrum speckle-interferometry observations of CIT 3 in the J-, H-,
and K-band. The resolution is 48 mas, 56 mas, and 73 mas, resp. The
interferograms were obtained with the Russian 6 m telescope at the
Special Astrophysical Observatory in September 1999. Detailed radiative
transfer calculations have been carried out and confronted with the
observations taking into account the spectral energy distribution
ranging from 1 μm to 1 mm, our near-infrared visibility functions
at 1.24 μm, 1.65 μm and 2.12 μm, as well as the recent 11 μm
interferometric measurements of Lipman et al. (2000).
Title: Confronting the Evolving Clumpy Shell Structure of IRC +10216
with Time Dependent Dust Shell Models
Authors: Winters, J. M.; Blöcker, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 2001AGM....18..P96W
Altcode: 2001AGAb...18Q.183W
The prototypical dust enshrouded carbon Mira IRC +10216 is known
to exhibit intrinsic structural changes on a time scale of the
order of 10 yr as revealed, e.g., by CO infrared line profiles, its
infrared light curves, or by high spatial resolution monitoring in
the infrared. In particular, the light curves obtained over 35 yr
indicate a possible periodicity on a ≈ 20 yr time scale, which
suggests that a recurrent phenomenon might lead to the observed
variations in the CO first overtone line profiles and the clumpy
spatial structure. Such multi-periodicity time scales, which correspond
to several (≈ 10) pulsation periods of the star, are predicted by
consistent hydrodynamical models which include a proper treatment of
dust formation. In these models discrete dust layers form on a time
scale which is longer than the typical pulsation period of AGB stars
(Fleischer et al. 1995). In the high spatial resolution images of IRC
+10216 (Osterbart et al. 2000) several components can be identified,
whose structure and brightness evolve considerably within only a few
years. To shed some light on this evolution, we apply a spherically
symmetric, time-dependent dust shell model which consistently describes
the coupled system of hydrodynamics, chemistry, dust formation and
radiative transfer (Winters et al. 2000) and confront the kinematics
and brightness variations predicted by this model with the high
spatial resolution observations of IRC +10216. Fleischer A.J., Gauger
A., Sedlmayr E., 1995, A&A 297, 543 Osterbart R., Balega Y.Y.,
Blöcker T., et al., 2000, A&A 357, 169 Winters J.M., Le Bertre T.,
Jeong K.S., et al., 2000, A&A 361, 641
Title: Bispectrum Speckle Interferometry of the Massive Protostellar
Object S140 IRS 1: Evidence for Multiple Outflows
Authors: Weigelt, Gerd; Preibisch, Thomas; Schertl, Dieter; Balega,
Yuri Y.; Smith, Michael D.
Bibcode: 2001AGM....18..P21W
Altcode: 2001AGAb...18R.145W
Bispectrum speckle interferometry is emplyed to explore
the deeply embedded young stellar object S140 IRS 1 and its
environment. Diffraction-limited resolution of 76 mas (~ 70 AU),
a dynamical range of more than 8 mag, and a field of view of 13'' ×
21'' in K'-band images were achieved with the SAO 6 m telescope. Our
image reveals a wealth of previously unseen complex structures. In
addition to a bright, elongated, and very clumpy feature pointing
from the central source to the south-east, we find several arc-like
structures north-east of IRS 1, extended diffuse emission south of
IRS 1, and four new point sources. The diffuse structures around IRS 1
seem to trace the interaction of energetic outflows from IRS 1 with the
circumstellar material. In combination with molecular line emission maps
from the literature, our image provides evidence for the presence of two
distinct bipolar outflow systems. A system of three arc-like structures
north-east of IRS 1 suggests directional variability of the outflow,
perhaps caused by the precession of a jet- or wind-driven outflow. We
discuss the implications for the nature of the central source.
Title: Multiplicity of Massive Stars
Authors: Preibisch, Thomas; Weigelt, Gerd; Zinnecker, Hans
Bibcode: 2001IAUS..200...69P
Altcode: 2000astro.ph..8014P
We discuss the observed multiplicity of massive stars and implications
on theories of massive star formation. After a short summary of the
literature on massive star multiplicity, we focus on the O- and B-type
stars in the Orion Nebula Cluster, which constitute a homogenous
sample of very young massive stars. 13 of these stars have recently
been the targets of a bispectrum speckle interferometry survey for
companions. Considering the visual and also the known spectroscopic
companions of these stars, the total number of companions is at least
14. Extrapolation with correction for the unresolved systems suggests
that there are at least 1.5 and perhaps as much as 4 companions per
primary star on average. This number is clearly higher than the mean
number of ~0.5 companions per primary star found for the low-mass
stars in the general field population and also in the Orion Nebula
cluster. This suggests that a different mechanism is at work in the
formation of high-mass multiple systems in the dense Orion Nebula
cluster than for low-mass stars.
Title: The Orbit of the Nearby Low-Mass Binary Gliese 600
Authors: Tokovinin, A. A.; Balega, Yu. Yu.; Hofmann, K. -H.;
Weigelt, G.
Bibcode: 2000AstL...26..668T
Altcode:
We have computed a combined spectroscopic-interferometric orbit for the
nearby binary Gliese 600 discovered by us. The orbital period is 2.78
years, and the semimajor axis is 100 mas (0.1"). Its M0V components
are almost identical and have a mass of 0.5 M_solar. The mass ratio is
uncertain because of the low radial-velocity semiamplitude (7 km/s)
associated with the low orbital inclination (37°deg). The orbital
parallax of the binary (52 +/- 11 mas) matches its dynamical and
photometric parallaxes but differs significantly from the HIPPARCOS
parallax (44.3 +/- 1.6 mas); the latter was probably distorted by the
orbital motion that was not taken into account.
Title: Diffraction-limited bispectrum speckle interferometry and
speckle polarimetry of the young bipolar outflow source S140 IRS1
Authors: Schertl, D.; Balega, Y.; Hannemann, T.; Hofmann, K. -H.;
Preibisch, Th.; Weigelt, G.
Bibcode: 2000A&A...361L..29S
Altcode: 2000astro.ph..9456S
We present bispectrum speckle interferometry and speckle polarimetry
of the deeply embedded infrared bipolar outflow source S140 IRS1,
a massive protostellar object in the L1204 molecular cloud. Using the
SAO 6 m telescope, we obtained 280 mas resolution polarization maps of
S140 IRS1 as well as a K-band image with diffraction-limited resolution
lambda /D of 76 mas, which is the highest angular resolution image of
a young outflow source ever obtained in the infrared. Our data suggest
that the central source is marginally resolved with a FWHM diameter
of approximately 20 mas ( ~ 20 AU). The most remarkable feature in our
image is a bright extended and very clumpy structure pointing away from
the central source in exactly the same direction as the blue-shifted
CO outflow lobe. A centro-symmetric pattern of high polarization in
this feature suggests that we see scattered light from the central
source. We interprete this feature as the clumpy inner surface of a
partially evacuated cavity in the circumstellar envelope around IRS1,
which has been excavated by the strong outflow from IRS1.
Title: Computer simulations of interferometric imaging with the VLT
Interferometer and the AMBER instrument
Authors: Bloecker, Thomas; Hofmann, Karl-Heinz; Przygodda, Frank;
Weigelt, Gerd
Bibcode: 2000SPIE.4006..174B
Altcode: 2000astro.ph..3474B
We present computer simulations of interferometric imaging with the
VLT interferometer and the AMBER instrument. These simulations include
both the astrophysical modeling of a stellar object by radiative
transfer calculations and the simulation of light propagation from the
object to the detector (through atmosphere, telescopes, and the AMBER
instrument), simulation of photon noise and detector read- out noise,
and finally data processing of the interferograms. The results show the
dependence of the visibility error bars on the following observational
parameters: different seeing during the observation of object and
reference star (Fried parameters r0,object equals 2.4 m,
r0,ref. equals 2.5 m), different residual tip- tilt error
((delta) tt,object equals 2% of the Airy disk diameter,
(delta) tt,ref. equals 0.1%), and object brightness
(Kobject equals 3.5 mag and 11 mag, Kref. equals
3.5 mag). Exemplarily, we focus on stars in late stages of stellar
evolution and study one of its key objects, the dusty supergiant
IRC + 10420 that is rapidly evolving on human timescales. We show
computer simulations of VLTI interferometry of IRC + 10420 with two
ATs (wide-field mode, i.e. without fiber optics spatial filters) and
discuss whether the visibility accuracy is sufficient to distinguish
between different theoretical model predictions.
Title: GI2T/REGAIN spectro-interferometry with a new infrared beam
combiner
Authors: Weigelt, Gerd; Mourard, Denis; Abe, Lyu; Beckmann, Udo;
Chesneau, Olivier; Hillemanns, C.; Hofmann, Karl-Heinz; Ragland,
Sam D.; Schertl, Dieter; Scholz, Michael; Stee, Philippe; Thureau,
Nathalie; Vakili, Farrokh
Bibcode: 2000SPIE.4006..617W
Altcode: 2000astro.ph..4184W
We have built an infrared beam combiner for the GI2T/REGAIN
interferometer of the Observatoire de la Cote d'Azur. The beam
controller allows us to record spectrally dispersed Michelson
interference fringes in the near-infrared J-, H- or K-bands. The
beam combiner has the advantage that Michelson interferograms
can simultaneously be recorded in about 128 different spectral
channels. The tilt of the spectrally dispersed fringes is a measure
of the instantaneous optical path difference. We present the optical
design of the beam combiner and GI2T/REGAIN observations of the Mira
star R Cas with this beam combiner in the spectral range of 2.00
micrometers - 2.18 micrometers (observations on 22 and 25 August 1999;
variability phase 0.08; V-magnitude approximately 6; seven baselines
between 12 m and 24 m; reference stars Vega and (beta) Peg).
Title: Observations of MIRA stars with the IOTA/FLUOR interferometer
and comparison with MIRA star models
Authors: Hofmann, Karl-Heinz; Beckmann, Udo; Bloecker, Thomas;
Coudé du Foresto, Vincent; Lacasse, Marc G.; Millan-Gabet, Rafael;
Morel, Sebastien; Pras, B.; Ruilier, Cyril; Schertl, Dieter; Scholz,
Michael; Shenavrin, V.; Traub, Wesley A.; Weigelt, Gerd; Wittkowski,
M.; Yudin, B.
Bibcode: 2000SPIE.4006..688H
Altcode: 2000astro.ph..4013H
We present K-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR
fiber optics beam combiner which provides high- accuracy visibility
measurements in spite of time-variable atmospheric conditions. For
the Mira stars X Oph, R Aql, RU Her, R Ser, and V CrB we derived the
uniform-disk diameters 11.7 mas, 10.9 mas, 8.4 mas, 8.1 mas, and 7.9
mas (+/- 0.3 mas), respectively. Simultaneous photometric observations
yielded the bolometric fluxes. The derived angular Rosseland radii
and the bolometric fluxes allowed the determination of effective
temperatures. For instance, the effective temperature of R Aql was
determined to be 3072 K +/- 161 K. A Rosseland radius for R Aql of
250 R. +/- 63 R. was derived from the angular Rosseland radius of
5.5 mas +/- 0.2 mas and the HIPPARCOS parallax of 4.73 mas +/- 1.19
mas. The observations were compared with theoretical Mira star models
(D/P model Rosseland radius equals 255 R.; measured R Aql Rosseland
radius equals 250 R. +/- 63 R.).
Title: Science opportunities with AMBER, the near-IR VLTI instrument
Authors: Richichi, Andrea; Bloecker, Thomas; Foy, Renaud; Fraix-Burnet,
Didier; Lopez, Bruno; Malbet, Fabien; Stee, Philippe; von der Luehe,
Oskar; Weigelt, Gerd
Bibcode: 2000SPIE.4006...80R
Altcode:
AMBER is the near-IR instrument for the VLTI, which will offer the
possibility of combining two or three beams from either the 8 meter
VLT main telescopes or the 1.8 meter auxiliary telescopes. With
spectral dispersion up to 10,000 high visibility accuracy and the
ability to obtain closure phases, AMBER will offer the means to
perform high quality interferometric measurements in the 1 - 2.5
micron range initially, with later extensions to other portions
of the spectrum. These design characteristics, coupled to the VLT
interferometer potential, open up the access to investigation of several
classes of objects, from stellar to extragalactic astronomy. We will
review the projected performance in terms of sensitivity and angular
resolution, and illustrate the potential applications in some key
research areas. In particular, we will present the work of the AMBER
Science Group, which is evaluating simulated data of source models
and interferometric outputs for the purpose of defining the criteria
for observations.
Title: Multiplicity of the Massive Stars in the Orion Nebula cluster
and Implications on their Formation Mechanism
Authors: Preibisch, Th.; Zinnecker, H.; Weigelt, G.; Hofmann, K. -H.;
Schertl, D.; Balega, Y.
Bibcode: 2000ESASP.445..495P
Altcode: 2000sfsl.conf..495P
No abstract at ADS
Title: The dynamical evolution of the fragmented, bipolar dust shell
around the carbon star IRC +10 216 . Rapid changes of a PPN-like
structure?
Authors: Osterbart, R.; Balega, Y. Y.; Blöcker, T.; Men'shchikov,
A. B.; Weigelt, G.
Bibcode: 2000A&A...357..169O
Altcode: 2000astro.ph..3328O
We present high-resolution J-, H-, and K-band observations and the first
H-K color image of the carbon star IRC +10 216. The
images were reconstructed from 6 m telescope speckle interferograms
using the bispectrum speckle interferometry method. The H and K images
with resolutions between 70 mas and 92 mas consist of several compact
components within a 0\farcs2 radius and a fainter asymmetric nebula. The
brightest four components are denoted with A to D in the order of
decreasing brightness in the 1996 image. A comparison of our images
from 1995, 1996, 1997, and 1998 gives -- almost like a movie of five
frames -- insight into the dynamical evolution of the inner nebula. For
instance, the separation of the two brightest components A and B
increased from 191 mas in 1995 to 265 mas in 1998. At the same time,
component B is fading and the components C and D become brighter. The
X-shaped bipolar structure of the nebula, most prominently present in
the J-band image, implies an asymmetric mass-loss. Such asymmetries
are often present in protoplanetary nebulae but are unexpected for AGB
stars. IRC +10 216 is thus likely to be very advanced
in its AGB evolution, shortly before turning into a protoplanetary
nebula. The cometary shapes of A in the H and J images and in the 0.79
mu m and 1.06 mu m HST images suggest that the core of A is not the
central star, but the southern lobe of a bipolar structure. The position
of the central star is probably at or near the position of component B,
where the H-K color has a value of 4.2. If the star is at or near B,
then the components A, C, and D are likely to be located at the inner
boundary of the dust shell. Based on observations performed with the
6~m telecope at the Special Astrophysical Observatory, Russia.
Title: Diffraction-limited Bispectrum Speckle Interferometry and
Speckle Polarimetry of the Young Bipolar Outflow Source S140 IRS1
Authors: Preibisch, Th.; Hannemann, T.; Hofmann, K. -H.; Schertl,
D.; Weigelt, G.; Balega, Y.
Bibcode: 2000AGM....17..P06P
Altcode: 2000AGAb...17Q..52P
We present bispectrum speckle interferometry and speckle polarimetry
of the deeply embedded infrared bipolar outflow source S140 IRS1,
a massive protostellar object in the L1204 molecular cloud. Using the
SAO 6 m telescope, we obtained 280 mas resolution polarization maps of
S140 IRS1 as well as a K-band image with diffraction-limited resolution
λ/D of 76 mas, which is the highest angular resolution image of a
young outflow source ever obtained in the infrared. Our data suggest
that the central source is marginally resolved with a FWHM diameter
of approximately 20 mas (~ 20 AU). The most remarkable feature in our
image is a bright extended and very clumpy structure pointing away from
the central source in exactly the same direction as the blue-shifted
CO outflow lobe. A centro-symmetric pattern of high polarization in
this feature suggests that we see scattered light from the central
source. We interprete this feature as the clumpy inner surface of a
partially evacuated cavity in the circumstellar envelope around IRS1,
which has been excavated by the strong outflow from IRS1.
Title: The VLT Interferometer and its AMBER Instrument: Simulations
of Interferometric Imaging in the Wide-Field Mode
Authors: Blöcker, T.; Hofmann, K. -H.; Przygodda, F.; Weigelt, G.
Bibcode: 2000AGM....17..P18B
Altcode: 2000AGAb...17Q..58B
We present computer simulations of interferometric imaging with
the VLT interferometer and the AMBER instrument. These simulations
include both the astrophysical modelling of a stellar object
by radiative transfer calculations and the simulation of light
propagation from the object to the detector (through atmosphere,
telescopes, and the AMBER instrument), simulation of photon noise
and detector read-out noise, and finally data processing of the
interferograms. The results show the dependence of the visibility
error bars on the following observational parameters: different seeing
during the observation of object and reference star (Fried parameters
r0,object and r0,ref. ranging between 0.9 m and
1.2 m), different residual tip-tilt error (δtt,object
and δtt,ref. ranging between 0.1% and 20% of the Airy
disk diameter), and object brightness (Kobject=3.5 mag to
13 mag, Kref.=3.5 mag). Exemplarily, we focus on stars in
late stages of stellar evolution and study one of its key objects,
the dusty supergiant IRC +10 420 that is rapidly evolving on human
timescales. We show computer simulations of VLT interferometry of IRC
+10 420 with two ATs (wide-field mode, i.e. without fiber optics spatial
filters) and discuss whether the visibility accuracy is sufficient to
distinguish between different theoretical model predictions.
Title: Multi-wavelength bispectrum speckle interferometry of R Cas
and comparison of the observations with Mira star models
Authors: Hofmann, K. -H.; Balega, Y.; Scholz, M.; Weigelt, G.
Bibcode: 2000A&A...353.1016H
Altcode:
We present diffraction-limited (30 mas) bispectrum speckle
interferometry observations of the Mira star R Cas with the Russian
6 m SAO telescope. The speckle interferograms were recorded through
narrow-band interference filters with centre wavelength/bandwidth
of 671 nm/6 nm and 714 nm/6 nm (strong TiO absorption band), 700
nm/6 nm (moderate TiO absorption), and 1045 nm/9 nm (continuum). The
reconstructed images show that the average uniform-disk diameters of
R Cas are 43.6 mas +/- 2.0 mas at 671 nm, 49.2 mas +/- 2.0 mas at 714
nm, 37.2 mas +/-2.0 mas at 700 nm, and 29.9 mas +/-3.0 mas at 1045
nm. In the 671 nm, 714 nm and 700 nm images the disks of R Cas are
non-uniform and elongated with position angles of the long axis of
52degr , 57degr and 54degr , and axis ratios of 0.70, 0.76 and 0.87,
respectively. For example, at 671 nm the size (elliptical uniform disk
fit) of the elongated R Cas disk is 51.0 mas x 35.6 mas. The 1045 nm
image shows no significant asymmetry. We compare our observations with
theoretical Mira star models and systematically check the capacity of
monochromatic diameter ratios and linear diameters for discriminating
between model representations of the observed star. Monochromatic tau
lambda =1 radii were derived from the observed visibilities
by application of model-predicted center-to-limb variations of the
intensity. Adopting the HIPPARCOS parallax we obtained a photospheric
radius (Rosseland tau_Ross =1 radius) of R Cas of 377 Rsun
+/- 60 Rsun (32.9 mas +/- 3.3 mas). The derived photospheric
radius and the large period ( ~ 430 days) suggest first overtone
pulsation for R Cas. We also determined the effective temperature of
R Cas at near-minimum phase to 1880 K +/- 130 K and propose T_eff ~
1900 K for spectral type M10 in the temperature calibration of very
late M giant spectral classes. Based on observations collected at the
SAO 6~m telescope in Russia
Title: Multiplicity of the young O- and B-type stars in the Orion
Nebula cluster
Authors: Preibisch, Th.; Hofmann, K. -H.; Schertl, D.; Weigelt, G.;
Balega, Y.; Balega, I.; Zinnecker, H.
Bibcode: 2000IAUS..200P.106P
Altcode:
We present the results of a bispectrum speckle interferometric
survey for binaries among the massive stars in the Orion Nebula
cluster. Observations of 13 bright cluster members of spectral type
O or B reveal 8 visual companions in total. Using the flux ratios of
the resolved systems to estimate the masses of the companions, we find
that the systems generally have mass ratios below 0.5. Extrapolation
with correction for the unresolved systems suggests that there are
at least 1.5 companions per primary star on average. This number is
clearly higher than the corresponding number for low-mass primaries,
suggesting that a different mechanism is at work in the formation of
high-mass multiple systems than for low-mass multiple systems.
Title: The dynamical evolution of the dust shell of IRC +10 216.
Authors: Osterbart, R.; Balega, Y.; Blocker, T.; Men'shchikov, A.;
Weigelt, G.
Bibcode: 2000MmSAI..71..701O
Altcode: 2000astro.ph..2473O
We present high-resolution J-, H-, and K-band observations of the carbon
star IRC+10216. The images were reconstructed from 6 m telescope speckle
interferograms using the bispectrum speckle interferometry method. The
H and K images consist of several compact components within a 0.2"
radius and a fainter asymmetric nebula. The brightest four components
are denoted with A to D in the order of decreasing brightness. A
comparison of our images gives - almost like a movie of five frames -
insight to the dynamical evolution of the inner nebula. For instance,
the separation of the two brightest components A and B increased by
almost 40% from 191 mas in 1995 to 265 mas in 1998. At the same time,
component B is fading and the components C and D become brighter. The
X-shaped bipolar structure of the nebula implies an asymmetric mass-loss
suggesting that IRC+10216 is very advanced in its AGB evolution,
shortly before turning into a protoplanetary nebula. The cometary
shape of component A suggests that the core of A is not the central
star, but the southern lobe of a bipolar structure. The position of
the central star is probably at or near the position of component B.
Title: Bispectrum speckle interferometry of the Orion Trapezium stars:
detection of a close (33 mas) companion of θ1 Ori C
Authors: Balega, Yu. Yu.; Weigelt, G.; Preibish, T.; Zinnecker, H.
Bibcode: 2000mfcp.proc...68B
Altcode:
We present bispectrum speckle interferometry observations with
the SAO 6 m telescope of the four brightest stars in the Orion
Trapezium. Diffraction-limited images with an unprecedented
resolution λ/D of 57 mas and 76 mas were obtained in the H- and
K-band, respectively. The H and K images of θ1 Ori C
(the star responsible for the proplyds) show for the first time
that θ1 Ori C is a close binary with a separation of
only ~ 33 mas (H-band observation). The sub-arcsecond companions of
θ1 Ori A and θ1 Ori B reported by Petr et
al. (1998) are confirmed. We use the magnitudes and colors of the
companions to derive information about their stellar properties from
the H-R diagram. In addition we briefly discuss the multiplicity of
the Trapezium stars. Considering both, the visual and spectroscopic
companions of the 4 Trapezium stars, it has been found that there
are at least 7 companions, i.e. at least 1.75 companions per primary
on average. This number is clearly higher than that found for the
low-mass stars in the Orion Nebula cluster as well as in the field
population. This suggests that the mechanisms operative in the formation
of high-mass multiple systems in the dense Trapezium cluster and of
low-mass stars are different.
Title: Observations of Mira Stars with the IOTA/FLUOR Interferometer
and Comparison with Mira Star Models
Authors: Hofmann, K. -H.; Beckmann, U.; Blöcker, T.; Schertl, D.;
Weigelt, G.; Wittkowski, M.; Coudé du Foresto, V.; Ruilier, C.;
Lacasse, M.; Morel, S.; Pras, B.; Traub, W.; Scholz, M.; Shenavrin,
V.; Yudin, B.
Bibcode: 2000AGM....17..P17H
Altcode: 2000AGAb...17R..57H
We present K-band observations of five Mira stars with the IOTA
interferometer. The interferograms were obtained with the FLUOR
fiber optics beam combiner whic h provides high-accuracy visibility
measurements in spite of time-variable atmosp heric conditions. For
the Mira stars X Oph, R Aql, RU Her, R Ser, and V CrB we derive d
the uniform-disk diameters 11.7mas, 10.9mas, 8.4mas, 8.1mas, and
7.9mas (± 0.3 mas), resp. Simultaneous photometric observations
yielded the bolometric fluxes. The derived angular Rosseland radii
and the bolometric fluxes allowed the determination of effective
temperatures. For instance, the effective temperatur e of R Aql was
determined to be 3072 K ± 161 K. A Rosseland radius for R Aql o f
250Rsolar ± 63 Rsolar was derived from the
angular Rosseland radius of 5.5 mas ± 0.2 mas and the HIPPARCOS
parallax of 4.73 mas ± 1.19 mas. The observations were compared
with theoretical Mira star models of Bessel, Scholz & Wood (1996)
and Hofmann, Scholz & Wood (1998) (D/P model Rosseland radius =
255 Rsolar).
Title: Multiplicity of the massive stars in the Orion Nebula cluster
Authors: Preibisch, Thomas; Balega, Yuri; Hofmann, Karl-Heinz; Weigelt,
Gerd; Zinnecker, Hans
Bibcode: 1999NewA....4..531P
Altcode:
We present bispectrum speckle interferometry observations of 13
bright Orion Nebula cluster member stars of spectral type O or
B. Diffraction-limited images with a resolution λ/ D of 75 mas in
the K'-band were obtained with the SAO 6 m telescope. In our speckle
images we find 8 visual companions in total. Using the flux ratios
of the resolved systems to estimate the masses of the companions,
we find that the systems generally have mass ratios below 1/2. The
distribution of mass ratios seems to be consistent with a companion mass
function similar to the field IMF. Considering both, the visual and
the spectroscopic companions of the 13 target stars, the total number
of companions is at least 14. Extrapolation with correction for the
unresolved systems suggests that there are at least 1.5 companions
per primary star on average. This number is clearly higher than
the mean number of ∼0.5 companions per primary star found for the
low-mass stars in the Orion Nebula cluster as well as in the field
population. This suggests that a different mechanism is at work in
the formation of high-mass multiple systems in the dense Orion Nebula
cluster than for low-mass stars.
Title: Parameters of four multiple systems from speckle interferometry
Authors: Balega, I. I.; Balega, Yu. Yu.; Hofmann, K. -H.; Tokovinin,
A. A.; Weigelt, G. P.
Bibcode: 1999AstL...25..797B
Altcode:
New or refined visual orbital elements are presented for four double
stars (HR 266 AP, 88 Tau AP = CHARA 18, eta Ori AB = McA18, ADS
16904 AP = CHARA 149) that are members of multiple systems. Relative
photometry and positional speckle measurements with the 6-m telescope
and published radial-velocity data for the stars are used. Photometric
data and parallaxes from the Hipparcos catalogs are also taken into
account. New physical models are proposed for multiple systems.
Title: The rapidly evolving hypergiant IRC +10 420: High-resolution
bispectrum speckle-interferometry and dust-shell modelling
Authors: Blöcker, T.; Balega, Y.; Hofmann, K. -H.; Lichtenthäler,
J.; Osterbart, R.; Weigelt, G.
Bibcode: 1999A&A...348..805B
Altcode: 1999astro.ph..6473B
The hypergiant IRC +10 420 is a unique object
for the study of stellar evolution since it is the only object that
is believed to be witnessed in its rapid transition from the red
supergiant stage to the Wolf-Rayet phase. Its effective temperature
has increased by 1000-2000 K within only 20 yr. We present the first
speckle observations of IRC +10 420 with 73 mas
resolution. A diffraction-limited 2.11 mu m image was reconstructed from
6 m telescope speckle data using the bispectrum speckle-interferometry
method. The visibility function shows that the dust shell contributes ~
40% to the total flux and the unresolved central object ~ 60%. Radiative
transfer calculations have been performed to model both the spectral
energy distribution and visibility function. The grain sizes, a, were
found to be in accordance with a standard distribution function, n(a)
~ a(-3.5) , with a ranging between a_min = 0.005 mu m and a_max =
0.45 mu m. The observed dust shell properties cannot be fitted by
single-shell models but seem to require multiple components. At a
certain distance we considered an enhancement over the assumed 1/r{(x})
density distribution. The best model for both SED and visibility was
found for a dust shell with a dust temperature of 1000 K at its inner
radius of 69 R_{*}. At a distance of 308 R_{*} the density was enhanced
by a factor of 40 and and its density exponent was changed from x=2 to
x=1.7. The shell's intensity distribution was found to be ring-like. The
ring diameter is equal to the inner diameter of the hot shell ( ~ 69
mas). The diameter of the central star is ~ 1 mas. The assumption of a
hotter inner shell of 1200 K gives fits of almost comparable quality but
decreases the spatial extension of both shells' inner boundaries by ~
30% (with x=1.5 in the outer shell). The two-component model can be
interpreted in terms of a termination of an enhanced mass-loss phase
roughly 60 to 90 yr (for d=5 kpc) ago. The bolometric flux, F_bol,
is 8.17 * 10(-10) Wm(-2) corresponding to a central-star luminosity
of L/Lsun = 25 462 * (d/kpc)(2) .
Title: Bispectrum speckle interferometry of the Orion Trapezium stars:
detection of a close (33 mas) companion of Theta (1) ORI C
Authors: Weigelt, Gerd; Balega, Yuri; Preibisch, Thomas; Schertl,
Dieter; Schöller, Markus; Zinnecker, Hans
Bibcode: 1999A&A...347L..15W
Altcode: 1999astro.ph..6233W
We present bispectrum speckle interferometry observations with
the SAO 6 m telescope of the four brightest stars in the Orion
Trapezium. Diffraction-limited images with an unprecedented
resolution lambda /D of 57 mas and 76 mas were obtained in the H-
and K-band, respectively. The H and K images of Theta (1) Ori C (the
star responsible for the proplyds) show for the first time that Theta
(1) Ori C is a close binary with a separation of only ~ 33 mas (H-band
observation). The sub-arcsecond companions of Theta (1) Ori A and Theta
(1) Ori B reported by Petr et al. (1998) are confirmed. We use the
magnitudes and colors of the companions to derive information about
their stellar properties from the HR-diagram. In addition we briefly
discuss the multiplicity of the Trapezium stars. Considering both,
the visual and the spectroscopic companions of the 4 Trapezium stars,
there are at least 7 companions, i.e. at least 1.75 companions per
primary on average. This number is clearly higher than that found
for the low-mass stars in the Orion Nebula cluster as well as in the
field population. This suggests that a different mechanism is at work
in the formation of high-mass multiple systems in the dense Trapezium
cluster than for low-mass stars. Based on data collected at the SAO
6~m telescope in Russia.
Title: High-resolution speckle masking interferometry and radiative
transfer modeling of the oxygen-rich AGB star AFGL 2290
Authors: Gauger, A.; Balega, Y. Y.; Irrgang, P.; Osterbart, R.;
Weigelt, G.
Bibcode: 1999A&A...346..505G
Altcode: 1999astro.ph..4218G
We present the first diffraction-limited speckle masking observations
of the oxygen-rich AGB star AFGL 2290. The speckle
interferograms were recorded with the Russian 6 m SAO telescope. At
the wavelength 2.11 microns a resolution of 75 milli-arcsec (mas) was
obtained. The reconstructed diffraction-limited image reveals that
the circumstellar dust shell (CDS) of AFGL 2290
is at least slightly non-spherical. The visibility function shows
that the stellar contribution to the total 2.11 microns flux is
less than ~ 40%, indicating a rather large optical depth of the
circumstellar dust shell. The 2-dimensional Gaussian visibility fit
yields a diameter of AFGL 2290 at 2.11 microns of
43 masx51 mas, which corresponds to a diameter of 42 AUx50 AU for an
adopted distance of 0.98 kpc. Our new observational results provide
additional constraints on the CDS of AFGL 2290,
which supplement the information from the spectral energy distribution
(SED). To determine the structure and the properties of the CDS we have
performed radiative transfer calculations for spherically symmetric
dust shell models. The observed SED approximately at phase 0.2 can
be well reproduced at all wavelengths by a model with T_eff=2000 K,
a dust temperature of 800 K at the inner boundary r1, an
optical depth tau_ {V}=100 and a radius for the single-sized grains
of a_gr=0.1 microns . However, the 2.11 microns visibility of the
model does not match the observation. Exploring the parameter space,
we found that grain size is the key parameter in achieving a fit of
the observed visibility while retaining the match of the SED, at least
partially. Both the slope and the curvature of the visibility strongly
constrain the possible grain radii. On the other hand, the SED at longer
wavelengths, the silicate feature in particular, determines the dust
mass loss rate and, thereby, restricts the possible optical depths of
the model. With a larger grain size of 0.16 microns and a higher tau_
{V}=150, the observed visibility can be reproduced preserving the
match of the SED at longer wavelengths. Nevertheless, the model shows
a deficiency of flux at short wavelengths, which is attributed to the
model assumption of a spherically symmetric dust distribution, whereas
the actual structure of the CDS around AFGL 2290 is
in fact non-spherical. Our study demonstrates the possible limitations
of dust shell models which are constrained solely by the spectral
energy distribution, and emphasizes the importance of high spatial
resolution observations for the determination of the structure and the
properties of circumstellar dust shells around evolved stars. Based
on data collected at the 6~m telescope of the Special Astrophysical
Observatory in Russia
Title: The dynamical evolution of the fragmented, bipolar dust shell
around the carbon star IRC +10 216
Authors: Osterbart, R.; Blöcker, T.; Weigelt, G.; Balega, Y. Y.;
Men'shchikov, A. B.
Bibcode: 1999AGAb...15..100O
Altcode:
We present high-resolution J-, H-, and K-band observations and the
first H-K color image of the carbon star IRC +10 216. The images
were reconstructed from 6 m telescope speckle interferograms using
the bispectrum speckle interferometry method. The H image has the
unprecedented resolution of 70 mas. The H and K images consist
of several compact components within a 0.2'' radius and a fainter
asymmetric nebula. A comparison of our images from 1995, 1996, 1997,
and 1998 gives - almost like a movie of five frames - spectacular
insight to the dynamical evolution of the inner nebula. For instance,
the separation of the two brightest components A and B increased from
191 mas in 1995 to 265 mas in 1998. At the same time, component B is
fading and the components C and D become brighter. The X-shaped bipolar
structure of the nebula, most prominently present in the J-band image,
implies an asymmetric mass-loss. Such asymmetries are often present in
protoplanetary nebulae but are unexpected for AGB stars. IRC +10 216 is
thus likely to be very advanced in its AGB evolution, shortly before
turning into a protoplanetary nebula. The cometary shapes of A in the
H and J images and in the 0.79 μm and 1.06 μm HST images suggest
that the core of A is not the central star, but the southern lobe
of a bipolar structure. The position of the central star is probably
at or near the position of component B. If the star is at or near B,
then the components A, C, and D are likely to be located at the inner
boundary of the dust shell.
Title: Bispectrum speckle interferometry of the nucleus of NGC 1068
Authors: Wittkowski, M.; Balega, Y.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1999AGAb...15..128W
Altcode:
We present new K-band bispectrum speckle interferometry studies of
the nuclear region of the Seyfert 2 galaxy NGC 1068. The speckle
interferograms were obtained with the Russian 6 m telescope at three
different epochs. The decrease of the visibility function reported
earlier is confirmed by all our new measurements. Furthermore,
we find that the visibility function is asymmetric. Our results
are consistent with a model consisting of (a) a compact component
with an average FWHM size of 30 mas or 2 pc which is elongated along
position angle -20^o, (b) an unresolved component and (c)
an extended northern component. We determine the total flux of both
the compact component and the unresolved component to be 0.5 Jy. We
compare our K-band structures with maps obtained at other wavelengths
with similar angular resolutions and discuss the nature of the three
components mentioned above.
Title: Bispectrum speckle interferometry of the Orion Trapezium stars:
detection of a close (33 mas) companion of Theta^1Ori C
Authors: Weigelt, Gerd; Preibisch, Thomas; Schertl, Dieter; Balega,
Yuri; Zinnecker, Hans
Bibcode: 1999AGAb...15...98W
Altcode:
We present bispectrum speckle interferometry observations with
the SAO 6 m telescope of the four brightest stars in the Orion
Trapezium. Diffraction-limited images with an unprecedented resolution
lambda/D of 57 mas and 76 mas were obtained in the H- and K-band,
respectively. The H and K images of Theta^1Ori C (the star responsible
for the proplyds) show for the first time that Theta^1Ori C is a close
binary with a separation of only ~33 mas (H-band observation). The
sub-arcsecond companions of Theta^1Ori A and Theta^1Ori B reported by
Petr et al. (1998) are confirmed. We use the magnitudes and colors of
the companions to derive information about their stellar properties from
the HR-diagram and find them to be intermediate- or low-mass pre-main
sequence stars. In addition we briefly discuss the multiplicity of the
Trapezium stars. Considering both, the visual and the spectroscopic
companions of the 4 Trapezium stars, there are at least 7 companions,
i.e. at least 1.75 companions per primary on average. This number is
clearly higher than that found for the low-mass stars in the Orion
Nebula cluster as well as in the field population. This suggests that
a different mechanism is at work in the formation of high-mass multiple
systems in the dense Trapezium cluster than for low-mass stars.
Title: Diffraction-limited 76 mas speckle-masking interferometry of
the carbon star IRC + 10 216 and related AGB objects with the SAO
6 m telescope
Authors: Weigelt, G.; Blöcker, T.; Hofmann, K. -H.; Osterbart, R.;
Balega, Y. Y.; Fleischer, A. J.; Winters, J. M.
Bibcode: 1999IAUS..191..273W
Altcode: 1998astro.ph.11276W
We present high-resolution J-, H-, and K-band observations of the
carbon star IRC +10 216. The images were reconstructed from 6 m
telescope speckle interferograms using the speckle masking bispectrum
method. The H image has the unprecedented resolution of 70 mas. The
H and K images consist of at least five dominant components within
a 0.21 arcsec radius and a fainter asymmetric nebula. The J--, H--,
and K--band images seem to have an X-shaped bipolar structure. A
comparison of our images from 1995, 1996, 1997, and 1998 shows that the
separation of the two brightest components A and B increased from ~193
mas in 1995 to ~246 mas in 1998. The cometary shapes of component A in
the H and J images and the 0.79 microns and 1.06 microns HST images
suggest that the core of A is not the central star, but the southern
(nearer) lobe of the bipolar structure. The position of the central
star is probably at or near the position of component B, where the H--K
color has its largest value of H--K = 4.2. If the star is located at
or near B, then the components A, C, and D are located close to the
inner boundary of the dust shell at separations of ~200 mas ~30 AU
(projected distance) ~6 stellar radii for a distance of ~ 150 pc,
in agreement with our 2-dimensional radiative transfer modelling. In
addition to IRC +10 216 we studied the stellar disks and the dust
shells of several related objects. Angular resolutions of 24 mas at
700 nm or 57 mas 1.6 microns were achieved.
Title: Multiplicity of the massive stars in the Orion Nebula cluster
and implications on their formation mechanism
Authors: Preibisch, Thomas; Hofmann, Karl-Heinz; Weigelt, Gerd;
Zinnecker, Hans; Balega, Yuri
Bibcode: 1999AGAb...15...19P
Altcode:
We present bispectrum speckle interferometry observations of 13
bright Orion Nebula cluster member stars of spectral type O or
B. Diffraction-limited images with a resolution lambda/D of 75 mas in
the K'-band were obtained with the SAO 6 m telescope. In our speckle
images we find 8 visual companions in total. Using the flux ratios
of the resolved systems to estimate the masses of the companions,
we find that the systems generally have mass ratios below 1/2. The
distribution of mass ratios seems to be consistent with a companion mass
function similar to the field IMF. Considering both, the visual and
the spectroscopic companions of the 13 target stars, the total number
of companions is at least 14. Extrapolation with correction for the
unresolved systems suggests that there are at least 1.5 companions per
primary star on average. This number is clearly higher than the mean
number of ~0.5 companions per primary star found for the low-mass stars
in the Orion Nebula cluster as well as in the field population. This
suggests that a different mechanism is at work in the formation of
high-mass multiple systems in the dense Orion Nebula cluster than for
low-mass stars.
Title: Bispectrum speckle interferometry observations and radiative
transfer models of the red supergiant NML CYG
Authors: Blöcker, T.; Hofmann, K. -H.; Weigelt, G.; Balega, Y. Y.
Bibcode: 1999AGAb...15..100B
Altcode:
The star NML Cyg is one of the most prominent infrared objects of
the northern hemisphere. It was discovered by Neugebauer, Martz &
Leighton (1965) as an extremely red object. NML Cyg is a highly evolved
OH/IR supergiant of very large luminosity (spectral type M6 I) which
suffers from an enormeous mass-loss ( 1.5 ṡ 10^{-4} M_odot/yr) and is
highly enshrouded by dust. It is supposed to be among the most luminous
supergiants ( 5 ṡ 105 L_odot) in the Galaxy. We present
the first diffraction-limited 2.13 μm observations of NML Cyg with 73
mas resolution. The speckle interferograms were obtained with the 6 m
telescope at the Special Astrophysical Observatory. The two-dimensional
power spectra show an extended nebula. There is only marginal evidence
for deviations from spherical symmetry. The visibility function declines
towards the diffraction limit to 0.6. We performed radiative transfer
calculations assuming sphercial symmetry to model the spectral energy
distribution and 2.13 μm visibility function. Additionally we consider
mid-infrared visibility functions recently published by Monnier et
al. (1997). The observed dust shell properties do not appear to be
in accordance with standard single-shell models (uniform outflow)
but seem to require multiple components.
Title: High-resolution bispectrum speckle interferometry and
two-dimensional radiative transfer modeling of the Red Rectangle
Authors: Men'shchikov, A. B.; Balega, Y. Y.; Osterbart, R.; Weigelt, G.
Bibcode: 1998NewA....3..601M
Altcode:
We present the first diffraction-limited K-band image of the
Red Rectangle with 76 mas resolution, an H-band image with 75 mas
resolution, and an RG 715 filter image (∼ 800 nm wavelength) with 78
mas resolution (corresponding to 25 AU for a distance of 330 pc). The
H and K images were reconstructed from 6 m telescope speckle data and
the RG 715 image from 2.2 m telescope data using the speckle masking
bispectrum method. At all wavelengths the images show a compact, highly
symmetric bipolar nebula, suggesting a toroidal density distribution of
the circumstellar material. No direct light from the central binary can
be seen as it is obscured by a dust disk or circumbinary torus. Our
first high-resolution H-K color image of the nebula shows a broad
red plateau of H-K≈ 2m in the bright inner regions. The
optical and near-infrared images and the available photometric continuum
observations in a wide range of ultraviolet to centimeter wavelengths
enabled us to model the Red Rectangle in detail using a two-dimensional
radiative transfer code. Our model matches both the high-resolution
images and the spectral energy distribution of this object very well,
making the following picture much more certain. The central close binary
system with a total luminosity of 3000 L⊙ is embedded in
a very dense, compact circumbinary torus which has an average number
density <nH> ≈5×1012 cm-3,
an outer radius of the dense inner region of R≈30 AU (91 mas), and a
ρ∝r-2 density distribution. The full opening angle of the
bipolar outflow cavities in our model is 70°. By comparing the observed
and theoretical images, we derived an inclination angle of the torus
to the line of sight of 7°±1°. The radiative transfer calculations
show that the dust properties in the Red Rectangle are spatially
inhomogeneous. The modeling confirms that the idea of large grains in
the long-lived disk around the Red Rectangle (Jura et al., 1997 [ApJ,
474, 741]) is quantitatively consistent with the observations. In our
models, unusually large, approximately millimeter-sized grains dominate
the emission of the compact, massive torus. Models with smaller average
grain sizes can possibly be found in future studies, for instance, if it
turns out that the radio spectrum is not mainly caused by continuum dust
emission. Therefore, the large grains suggested by our models require
further confirmation by both new observations and radiative transfer
calculations. Assuming a dust-to-gas ratio ρd/ρg
of 0.005, the dense torus mass is 0.25 M⊙. The model gives
a lower limit of 0.0018 M⊙, for the mass of the large
particles, which produce a gray extinction of A≈ 28m,
towards the center. A much smaller mass of submicron-sized dust grains
is presumably located in the polar outflow cavities, their conical
surface layers, and in the outer low-density parts of the torus
(where ρ∝r-4, in the region of 30 AU≲r≲ 2000 AU
corresponding to 0.''09-6'').
Title: Diffraction-limited speckle-masking interferometry of the
red supergiant VY CMa
Authors: Wittkowski, M.; Langer, N.; Weigelt, G.
Bibcode: 1998A&A...340L..39W
Altcode: 1998astro.ph.11280W
We present the first diffraction-limited images of the mass-loss
envelope of the red supergiant star VY CMa. The two-dimensional optical
and NIR images were reconstructed from 3.6 m telescope speckle data
using bispectrum speckle interferometry. At the wavelengths ~ 0.8 mu m
(RG 780 filter), 1.28 mu m, and 2.17 mu m the diffraction-limited
resolutions of 46 mas, 73 mas, and 124 mas were achieved. All
images clearly show that the circumstellar envelope of VY CMa is
non-spherical. The RG 780, 1.28 mu m, and 2.17 mu m FWHM Gaußfit
diameters are 67 masx83 mas, 80 masx116 mas and 138 masx205 mas,
respectively, or 100 AUx125 AU, 120 AUx174 AU and 207 AUx308 AU
(for a distance of 1500 pc). We discuss several interpretations
for the asymmetric morphology. Combining recent results about the
angular momentum evolution of red supergiants and their pulsational
properties, we suggest that VY CMa\xspace is an
immediate progenitor of IRC +10 420, a post red
supergiant during its transformation into a Wolf-Rayet star. Based on
data collected at the European Southern Observatory, La Silla, Chile
Title: Interferometry with the Large Binocular Telescope
Authors: Angel, J. Roger P.; Hill, John M.; Strittmatter, Peter A.;
Salinari, Piero; Weigelt, Gerd
Bibcode: 1998SPIE.3350..881A
Altcode:
The Large Binocular Telescope has been designed for optical/IR
interferometry that combines high sensitivity and resolution. Key
scientific projects will be deep, wide field IR images of the Hubble
Deep Field, with nearly ten times the resolution of the Hubble
telescope, and the study of planets and dust in extra-solar systems,
from their formation onward. A basic requirement for interferometry of
faint objects is that the aberrations across the two 8.4m telescopes
be corrected for atmospheric phase errors. This will be done at
the telescopes' secondary mirrors, so as to preserve the very l
ow emissivity of the direct beam combination optics. Sodium lasers
projected co-axially from above each secondary will allow wavefront
sensing for correction of even the faintest objects. The two telescopes
are rigidly mounted close together on a single alt-azimuth mount,
to cover a large fraction of the uv plane in a single exposure,
with baselines continuous from 0 to 23 m. Field rotation during the
night completes the cover, to allow recovery of images with the full
resolution of a diffraction limited 23 m telescope. The beam combining
optics will be cryogenically cooled to maintain the very low thermal
background from only 3 warm reflections in total. For wide field
imaging, the beams will be combine and stabilized so that in a long
exposure every source across an approximate 1 arcminute field is
crossed by interference fringes. From a set of such exposures the
resultant deep image will have a resolution 0.02 arcsec in the 2.2
micrometers K band. For high contrast studies of exo-planetary systems,
a Bracewell nulling system will be used with superposition by division
of amplitude, for 99.99 percent suppression of the stellar radiation.
Title: 76mas speckle-masking interferometry of IRC+10216 with the
SAO 6m telescope: Evidence for a clumpy shell structure
Authors: Weigelt, G.; Balega, Y.; Bloecker, T.; Fleischer, A. J.;
Osterbart, R.; Winters, J. M.
Bibcode: 1998A&A...333L..51W
Altcode: 1998astro.ph..5022W
We present the first K(') -band image of the carbon star IRC+10216
with 76mas resolution. The diffraction-limited image was reconstructed
from 6m telescope speckle data using the speckle masking bispectrum
method. The image shows that the dust shell of IRC+10216 is extremely
clumpy. Five individual clouds within a 0farcs21 radius of the
central star have been resolved for the first time. On the basis
of consistent theoretical models we argue that these structures are
produced by circumstellar dust formation. The fragmentation of the
shell structure gives most likely direct evidence for an inhomogeneous
mass-loss process which may be interpreted in terms of large-scale
surface convection-cells (Schwarzschild \cite{Schwschil_75}) being a
common phenomenon for red giants.
Title: Diffraction-limited speckle masking interferometry of binary
stars with the SAO 6-m telescope
Authors: Schoeller, M.; Balega, I. I.; Balega, Y. Y.; Hofmann, K. -H.;
Reinheimer, T.; Weigelt, G.
Bibcode: 1998AstL...24..283S
Altcode: 1998PAZh...24..337S
Optical speckle masking observations of 32 binary and multiple
stars with the SAO 6-m telescope are presented. The resolution of the
reconstructed diffraction-limited images is 23 mas at 656 nm. Accurate
magnitude differences were first determined for most binaries. The
results for individual systems are compared with the available orbits
and with published photometric data. A new close visual component was
discovered in the multiple system ADS 784.
Title: High-resolution Speckle Imaging and Radiative Transfer Modeling
of the Red Rectangle
Authors: Osterbart, R.; Men'shchikov, A. B.; Weigelt, G.; Balega,
Y. Y.; Langer, N.
Bibcode: 1998AGAb...14..114O
Altcode: 1998AGM....14..P31O
We present diffraction-limited optical and NIR images of the Red
Rectangle reconstructed from ESO/MPG 2.2 m and SAO 6 m telescope
data. The unprecedented resolution of ~75 mas was achieved by applying
the speckle masking bispectrum method to the data. The bipolar structure
of the Red Rectangle is visible at all observed wavelengths. Two
bright compact lobes are present in the center of the nebula with a
separation of approximately 0.15^{''}. A dark dust lane totally obscures
the central close binary. This structure and the X-shape of the nebula
on larger scales are thought to be the result of a rather strong wind
clearing the polar cavities. Our 2D radiative transfer calculations
show that the bipolar appearance is caused by a very dense, compact
torus with an optical depth of A_V ~ 30 mag. From a comparison of
the observed and theoretical images, we derived an inclination angle
of 7^\circ for the torus. The model torus has a \rho \propto r^{-2}
dust density distribution between the inner boundary at ~ 6 AU and
R~ 16 AU (~ 50 mas), while at larger distances the density gradient
steepens to approximately \rho \propto r^{-4}. We derived a lower
limit for the total dust mass in the torus of ~ 2 10^{-3} M_\odot. The
radiative transfer calculations show that the best agreement with all
observational constraints can be found if the compact, massive torus
contains predominantly very large (millimeter-sized) grains. A much
smaller mass of normal (submicron-sized) grains must exist mainly in
the bipolar outflow regions.
Title: Diffraction-limited Bispectrum Speckle Interferometry of the
Carbon Star IRC +10 216 with the SAO 6 M telescope
Authors: Osterbart, R.; Bloecker, T.; Men'shchikov, A. B.; Weigelt,
G.; Balega, Y. Y.; Winters, J. M.
Bibcode: 1998AGAb...14..115O
Altcode: 1998AGM....14..P32O
We present the first H- and K-band images of the carbon star IRC
+10 216 with ~76 mas resolution. The images were reconstructed from
6 m telescope speckle data using the speckle masking bispectrum
method. Several individual components of the circumstellar dust shell
can be resolved at separations of approximately 100 to 200 mas from the
central object. The dust clouds are located inside a larger nebulosity
of a bipolar, X-shaped structure with an approximate NS polar axis. The
high-resolution images as well as the SED of the object are compared
with results of 2D radiative transfer calculations. The considerable
brightness of one of the clouds can be explained if we assume that the
central star is heavily obscured by circumstellar dust clouds. The
radius of the central object was determined to be approximately
25 mas. Our high-resolution observations obtained at different
epochs within the last 3 years suggest a dynamical evolution of the
resolved structures caused by the expansion of the dust shell. For
the interpretation of the resolved shell structures we compared our
observations with time-dependent model calculations for carbon-rich
circumstellar dust shells. The fragmentation of the dust shell can most
likely be interpreted as direct evidence for a mass-loss process of
extreme inhomogeneity, possibly caused by large-scale surface convection
cells (supergranulation) of red giants discussed by Schwarzschild.
Title: The hypergiant IRC +10 420: High-resolution speckle-masking
interferometry and dust-shell modelling
Authors: Bloecker, T.; Hofmann, K. -H.; Lichtenthaeler, J.; Osterbart,
R.; Weigelt, G.; Balega, Y. Y.
Bibcode: 1998AGAb...14..116B
Altcode: 1998AGM....14..P34B
The peculiar star IRC +10 420 is an outstanding object for the study of
stellar evolution. It is one of the brightest IRAS objects due its very
strong infrared excess by circumstellar dust and one of the warmest
stellar OH maser sources known. It exhibits large mass-loss rates,
typically of the order of several 10^{-4} M_{\odot}/yr, and, even
more importantly, its spectral type changed from F8 I_a^{+} in 1973
(Humphreys et al.\ 1973, ApJ 179, L49) to A-type today (Oudmaijer et
al. 1996, MNRAS 280, 1062) corresponding to an effective temperature
increase of 1000--2000 K within only 20 yr. Due to its distance,
large wind velocity and photometric history IRC +10 420 is most likely
a luminous hypergiant evolving off the RSG branch, therefore being
the only massive object observed up to now in its transition to the
Wolf-Rayet phase. We present the first diffraction-limited K-band
observations of IRC +10 420 with 76 mas resolution. The speckle
interferograms were obtained with the 6 m telescope at the Special
Astrophysical Observatory. The visibility shows an unresolved central
object and an extended dust shell. The dust shell contributes ~ 40 % to
the total flux. We performed radiative transfer calculations to model
the spectral energy distribution and visibility. The observed dust
shell properties cannot be fitted by single-shell models but require
the introduction of different temperature and density components.
Title: Diffraction-limited IR speckle masking observations of the
central regions of Seyfert galaxies
Authors: Wittkowski, M.; Balega, Y.; Beckert, T.; Duschl, W. J.;
Hoffman, K. -H.; Weigelt, G.
Bibcode: 1998IAUS..184..103W
Altcode:
We present first results of diffraction-limited NIR speckle masking
investigations of the nuclei of Seyfert galaxies with angular
resolutions of 100 mas. Using the K-band, we find compact structures
in NGC 4151 and NGC 1068 with sizes 2.5 pc. Assuming optically thin
synchrotron radiation from quasi-monoenergetic relativistic electrons,
we are able to derive characteristic parameters of the emitting source
(size, electron energy, electron density,magnetic field) from the
radio-NIR spectrum of the nucleus. We find that the synchrotron source
is much smaller than our angular resolution thus indicating that the
resolved structures in our NIR images are circumnuclear gas and dust.
Title: Interferometry with the Large Binocular Telescope
Authors: Zinnecker, H.; Hasinger, G.; Storm, J.; Weigelt, G.
Bibcode: 1998AGAb...14...92Z
Altcode: 1998AGM....14..L07Z
The Large Binocular Telescope (LBT), with its two 8.4m telescopes
separated by 14.4m (centre-to-centre), is scheduled to be ready
for interferometric observations in the combined beam by the year
2004. To be operational in this mode, adaptive optics wave front
correction must first be applied (using adaptive secondary mirrors)
to each of the two individual telescopes and then the optical path
length difference between the ``two eyes" needs to be measured
and corrected for in real time (fringe tracking). This will allow
the investigation of the structure of astronomical objects at 10
times the spatial resolution of the Hubble Space Telescope. First
observations are likely to concentrate on the near (2 \mum) or mid (10
\mum) infrared wavelength region. Science on the extragalactic side
includes deep imaging studies of the Hubble Deep Field, the Lockman
Hole, active galactic nuclei and their circumnuclear starbursts,
and of star formation in colliding/merging high-redshift galaxies. On
the galactic side, science with the LBT interferometer will focus on
obtaining true images of circumstellar/protoplanetary disks around
young stars and on direct imaging of giant planets in orbit around
many nearby stars. Differential astrometry at the 1 mas level over
a wide FOV (1-2 arcmin) in the the near-infrared should also become
possible, e.g. for proper motion measurements of distant Galactic halo
stars against some quasar reference. More about interferometry with
the LBT can be found in a recent article by Angel et al. accessible
at http://medusa.as.arizona.edu/lbtwww/tech/interf98.htm
Title: Diffraction-limited 76mas speckle masking observations of
the core of NGC 1068 with the SAO 6m telescope
Authors: Wittkowski, M.; Balega, Y.; Beckert, T.; Duschl, W. J.;
Hofmann, K. -H.; Weigelt, G.
Bibcode: 1998A&A...329L..45W
Altcode: 1997astro.ph.11254W
We present the first K-band bispectrum speckle interferometry of NGC1068
with an angular resolution of 76mas ( ~ 5.5pc). This angular resolution
allows us to attribute the measured flux to only one of the nuclear
sources seen at radio wavelengths. The observed decreasing visibility
function suggests that the dominant central core is probably not an
unresolved point source, but slightly resolved with a FWHM diameter
of ~ 30mas ~ 2pc for an assumed Gaussian intensity distribution. This
30mas object is possibly the nuclear torus and/or a scattering halo. We
discuss different contributions to the observed K band flux. Between
5GHz and the K-band the spectrum of this component is close to a nu
(1/3) proportionality. In addition to the standard interpretation
of a hot dust torus surrounding the nucleus of NGC1068, one cannot
exclude the possibility that a sizeable fraction of the nuclear flux
reaches us via a scattering halo. This then would allow us to determine
physical parameters of the nuclear source. Based on data collected at
the Special Astrophysical Observatory, Russia
Title: 75 MAS Speckle Imaging and Radiative Transfer Modeling of
the Red Rectangle
Authors: Osterbart, R.; Balega, Y. Y.; Langer, N.; Men'shchikov,
A. B.; Weigelt, G.
Bibcode: 1998IAUS..191P.519O
Altcode:
We present diffraction-limited optical and Near-IR images of the
Red Rectangle reconstructed from ESO/MPG 2.2 m and SAO 6 m telescope
data. The unprecedented resolution of about 75 mas was achieved by
applying the speckle masking bispectrum method to the data. The results
reveal a bipolar structure of the Red Rectangle over a wide range of
wavelengths. The nebula appears as two bright compact lobes (separation
~0.15^'') with a pronounced {X}-shaped structure. A dark dust lane
totally obscures the central close binary which has probably undergone
a common envelope phase. This structure is thought to be the result
of a rather strong wind clearing the polar cavities. Our 2D radiative
transfer calculations show that this appearance is due to a very dense,
compact torus with an optical depth of A_V ~30 mag. The full opening
angle of the bipolar outflow cavities in our model is 70^circ. From
a comparison of the observed and theoretical images, we derived an
inclination angle of 7^circ for the torus. The model torus has a rho
propto r^{-2} dust density distribution between the inner boundary at
~6 AU and R ~16 AU (~50 mas), while at larger distances, the density
gradient steepens approximately to rho propto r^{-4}. We derived a lower
limit for the total dust mass in the torus of ~2 10^{-3} M_odot. The
radiative transfer calculations also show that the dust properties
in the Red Rectangle are spatially very inhomogeneous. The compact,
massive torus contains predominantly very large (millimeter-sized)
grains, while a much smaller mass of normal (submicron-sized) grains
must exist mainly in the bipolar outflow regions.
Title: Diffraction-limited speckle masking observations of the Mira
variables R CAS and R Leo with the 6 M SAO telescope
Authors: Hofmann, K. -H.; Weigelt, G.; Balega, Y. Y.; Scholz, M.
Bibcode: 1998AGAb...14R.121K
Altcode: 1998AGM....14..P45K
We present the first diffraction-limited optical and infrared speckle
masking observations of Mira stars with the 6 m SAO telescope. A
resolution of 24 mas was achieved at 700 nm wavelength. The speckle
interferograms were recorded through various narrow-band interference
filters between 673 nm and 1045 nm covering strong and weak TiO
absorption bands and the continuum. Mira stars show substantial
variations of their angular size with wavelength caused by the
wavelength dependence of TiO opacity. Our reconstructions show that
the disk of R Cas is non-uniform and elongated. The size (elliptical
uniform disk fit) of the elongated disk is 35 mas x 40 mas in the
700 nm pseudo-continuum filter and 42 mas x 56 mas in the 714 nm TiO
absorption band filter. In the 1045 nm continuum image the disk of R
Cas shows no asymmetry and has a uniform disk diameter of 30 mas. The
goal of our Mira star project is to provide the basic observations for
a quantitative analysis of the photospheric structure of Mira variables
and thus to test Mira star models. We compare our observations of R
Cas and R Leo with the models of Bessell et al. (1996). Using the
E model series of Bessell et al. we find, for instance, for R Cas
a photospheric (Rosseland) radius of 380+/-70 R_{\odot} and a low
effective temperature of approximately 1900 K near minimum phase.
Title: Speckle masking imaging and radiative transfer modeling of
the oxygen-rich dust shells of AFGL 2290 and CIT 3
Authors: Irrgang, P.; Balega, Y. Y.; Gauger, A.; Osterbart, R.;
Schniggenberg, G.; Weigelt, G.
Bibcode: 1998IAUS..191P.408I
Altcode:
The extreme mass loss suffered by stars on the asymptotic giant branch
(AGB) substantially affects the appearance of these objects, which
is dominated by the development of opaque, massive, circumstellar
dust shells (CDS), and even more important, it determines the final
evolution to the planetary nebula stage. High spatial resolution
observations directly provide information on important properties
of CDS around AGB stars, such as the dimensions and geometry of the
shell, and thereby contribute strong constraints for the modeling
of the mechanisms and processes determining these circumstellar
environments. We present diffraction-limited speckle masking
observations of the oxygen-rich AGB stars AFGL 2290 (OH 39.7+1.5)
at 2.2 microns and of CIT 3 (OH 128.6-50.1) at 1.65 microns and 2.2
microns. The speckle interferograms were obtained with the SAO 6 m
telescope, and we achieved the diffraction-limited resolutions of 56
mas and 76 mas at 1.65 microns and 2.2 microns, respectively. The CDS
of AFGL 2290 is partially resolved and found to be slightly asymmetric
with a mean Gaussian FWHM diameter of ~42 mas. The azimuthally averaged
visibility yields an upper limit of ~25% for the stellar contribution
to the 2.2 microns flux, suggesting a rather high optical depth. We
have performed detailed radiative transfer calculations assuming a
spherically symmetric dust shell, and found that such models reproduce
either the observed spectral energy distribution, or the measured
visibility of AFGL 2290, but not both simultaneously. We interpret this
behaviour as being due to a non-spherical dust distribution supporting
the evidence from the speckle masking image reconstruction. The speckle
imaging results for CIT 3 indicate a more structured CDS compared to
AFGL 2290. The azimuthally averaged visibilities can only be well fitted
with a two-component model consisting of a partially resolved smaller
component and a fully resolved nebulosity, which is several times more
extended. The smaller component represents the hot innermost region
of the CDS, whereas the presence of the extended component might point
to a change of physical properties in the outflow.
Title: Speckle masking observations and radiative transfer modeling
of the oxygen-rich dust shells of AFGL 2290 and CIT 3
Authors: Gauger, A.; Irrgang, P.; Osterbart, R.; Schniggenberg, G.;
Weigelt, G.; Balega, Y. Y.
Bibcode: 1998AGAb...14..115G
Altcode: 1998AGM....14..P33G
High spatial resolution observations directly provide information
on important properties of circumstellar dust shells (CDS) around
asymptotic giant branch (AGB) stars, such as the dimensions and the
geometry of the shell, and therefore contribute strong constraints for
the radiative transfer modeling of these circumstellar environments. We
present the first diffraction-limited speckle masking observations of
the oxygen-rich AGB stars AFGL 2290 (OH 39.7+1.5) and CIT 3 (IRC+10011)
at near infrared wavelengths. The speckle interferograms were obtained
with the Russian SAO 6m telescope. We achieved the diffraction-limited
resolutions of 56 mas at 1.65 \mu m and 76 mas at 2.2 \mu m. The CDS of
AFGL 2290 is found to be slightly asymmetric with a mean Gaussian FWHM
diameter of ~ 42 mas at \lambda=2.2 \mu m. The derived visibility yields
an upper limit for the stellar flux contribution at 2.2 \mu m of ~ 40 %,
suggesting a rather high optical depth. We have found that radiative
transfer models assuming a spherically symmetric dust shell either
reproduce the observed spectral energy distribution, or the measured
visibility of AFGL 2290, but not both simultaneously. This behaviour
is interpreted as being due to a non-spherical dust distribution. The
observations of CIT 3 showed that its CDS has a two component structure:
a compact inner component with a Gaussian FWHM diameter of ~ 40 mas
at \lambda=2.2 \mu m, and a weaker nebulosity, which is several times
more extended.
Title: Diffraction-limited speckle masking observations of the Mira
variables R Cas and R Leo with the 6 m SAO telescope.
Authors: Hofmann, K. -H.; Weigelt, G.; Balega, Y. Y.; Scholz, M.
Bibcode: 1998AGAb...14Q.125H
Altcode: 1998AGM....14..P52H
No abstract at ADS
Title: High-resolution imaging of the bipolar nebula Red
Rectangle. Evidence for unstable mass transfer in a close binary
system.
Authors: Osterbart, R.; Langer, N.; Weigelt, G.
Bibcode: 1997A&A...325..609O
Altcode:
We present the first diffraction-limited speckle-masking bispectrum
observations of the central part of the Red Rectangle at optical
wavelengths (λ~656nm and λ~800nm). The results confirm infrared
observations which show that the object is a bipolar nebula. The dark
lane separating the two lobes is probably produced by an obscuring dust
disk slightly inclined with respect to the line of sight. The fainter
northern lobe appears not to be reddened by the disk. This implies an
upper limit of the outer disk radius of about 200AU. We propose that
the observed nebula is the result of recent mass ejection induced by
unstable mass transfer from an AGB star to a close companion.
Title: Speckle interferometry of the spectroscopic binaries Gliese
150.2 and 41 Draconis
Authors: Balega, I. I.; Balega, Yu. Yu.; Falcke, H.; Osterbart, R.;
Reinheimer, T.; Schöller, M.; Weigelt, G.
Bibcode: 1997AstL...23..172B
Altcode: 1997PAZh...23..199B
We present the first diffraction-limited, visible and infrared speckle
masking observations of the nearby spectroscopic binaries Gl 150.2 and
41 Dra performed with the 6-m telescope. Gl 150.2 is a pair of K0 and
M0 dwarfs with a magnitude difference of 2.49+-0.05 mag in the red. Its
orbital period is close to ten years. A preliminary apparent orbit
was derived for the pair 41 Dra with double-lined F7 V components
from six speckle measurements. The masses of the components of 41
Dra determined with an error of +-16% are 1.26 and 1.18msun. Their
absolute magnitudes, M_bol(a)=2.92 and M_bol(b) = 3.30, place them
0.8 mag above the main-sequence stars of the same spectral range.
Title: Interferometric Observations of Mira Stars
Authors: Hofmann, K. -H.; Balega, Y.; Scholz, M.; Weigelt, G.
Bibcode: 1997svlt.work..367H
Altcode:
No abstract at ADS
Title: Diffraction-limited speckle-masking observations of the Red
Rectangle and IRC+10216 with the 6 M telescope
Authors: Osterbart, R.; Balega, Y. Y.; Weigelt, G.; Langer, N.
Bibcode: 1997IAUS..180..362O
Altcode:
No abstract at ADS
Title: VizieR Online Data Catalog: Massive stars in I Zw 36
(Deharveng+ 1994)
Authors: Deharveng, J. -M.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Disney, M. J.; Jakobsen, P.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1997yCat..32880413D
Altcode:
We have observed the blue dwarf galaxy I Zw 36 with the f/96 relay
of the HST Faint Object Camera and have for the first time resolved
massive stars, using the broad band filters F175W, F342W, F430W and
F480LP. We have measured the fluxes of 143 of these objects and studied
their characteristics in color-magnitude diagrams. A few stars may be
red supergiants but their contribution to the integrated light is less
than 5% in the F430W filter. The F175W-F430W color of the integrated
stellar population is redder than expected from the current burst
of star formation, suggesting therefore the presence of an older
and unresolved underlying population. The ultraviolet measurements
combined with synthetic photometry calculations allow us to place the
massive stars in a bolometric magnitude vs. temperature diagram. In
this diagram, the stars are compared to evolutionary tracks for
different stellar masses. The current burst probably has an age less
than 12Myr. We infer an Initial Mass Function, with a power-law slope
in the range -1.7 to -2.6 for masses M>=20M⊙. This is
consistent with most of the values reported for sites of star formation
in the Galaxy and the Magellanic Clouds and does not support the view
of an IMF flattening at low metallicity. (1 data file).
Title: Speckle masking interferometry with the Large Binocular
Telescope
Authors: Reinheimer, T.; Hofmann, K. -H.; Scholler, M.; Weigelt, G.
Bibcode: 1997A&AS..121..191R
Altcode:
We present a method for interferometric imaging with the Large
Binocular Telescope (LBT) at optical and infrared wavelengths. For
example, at lambda = 550 nm a resolution of 6.1 mas can be obtained. The
uv-coverage is excellent due to the small distance between the two 8.4
m mirrors. We show laboratory and computer experiments of LBT speckle
masking interferometry. The raw data were produced by simulating light
propagation in the atmosphere, the LBT pupil function, earth rotation,
and photon noise. The generated data sets consist of up to 200,000
LBT interferograms per experiment with 200 to 2000 photoevents per
interferogram. 200,000 interferograms correspond to only 1.1 hours
observing time for a frame rate of 50 frames/sec. In the computer
simulations a Fried parameter of 40 cm was simulated which corresponds
to 0.35 arcsec seeing. Diffraction-limited images were reconstructed
from the various data sets by a modified version of the speckle
masking method (bispectral analysis, triple correlation method) and
the iterative building block method. The reconstructed images show
the dependence of the signal-to-noise ratio on photon noise and other
parameters. In one of the experiments the object was a compact cluster
of four stars and the interferograms consisted of only 200 photoevents
per interferogram. 200 photoevents per interferogram correspond to a
total $V$ magnitude ~14.3 for two 8 m telescopes, 20 msec exposure time
per interferogram, 5 nm filter bandwidth, and 10% quantum efficiency
of detector plus optics. In this experiment the magnitudes of the four
individual stars were 15.6, 15.8, 16.4, and 17.1. In a second experiment
a compact galaxy with total magnitude of 11.3 and magnitude ~14 of the
faintest resolution element was simulated and a diffraction-limited
image reconstructed successfully from only 200\,000 interferograms (1.1
hour observing time). Objects of about 18th magnitude can be observed
if observing time is increased and observations are made simultaneously
in many spectral channels. An advantage of speckle masking is that it
can be applied to objects fainter than 14th $V$ magnitude, whereas for
adaptive optics (with natural reference stars for wavefront sensing)
the object or the reference star has to be brighter than about 14th
magnitude. Diffraction-limited images of objects fainter than 18th
magnitude can be obtained by LBT speckle masking observations if
partial wavefront compensation (low-order adaptive optics) is achieved
by an artificial laser guide star system (\cite[Foy \& Labeyrie
1985]{Foy1985}; \cite[Fugate et al. 1991]{Fugate1991}; \cite[Primmerman
et al. 1991]{Primmerman1991})
Title: Speckle masking observations of the circumnuclear region of
NGC 1068 in the K-band.
Authors: Wittkowski, M.; Balega, Y.; Beckert, T.; Duschl, W. J.;
Hofmann, K. -H.; Weigelt, G.
Bibcode: 1997AGAb...13...64W
Altcode:
No abstract at ADS
Title: Speckle Masking Imaging of the Spectroscopic Binaries Gliese
150.2 and 41 Draconis
Authors: Balega, I.; Balega, Yu.; Falcke, H.; Osterbart, R.; Schöller,
M.; Weigelt, G.
Bibcode: 1997ASSL..223...73B
Altcode: 1997vdsf.conf...73B
No abstract at ADS
Title: Multi-Speckle Interferometric Imaging with the Vlti and the
LBT at Optical Wavelengths
Authors: Reinheimer, Th.; Hofmann, K. -H.; Schöller, M.; Weigelt, G.
Bibcode: 1997svlt.work..387R
Altcode:
No abstract at ADS
Title: Infrared Interferometric Imaging with the Vlti in the
Multi-Speckle Mode with a Combination of the 8 M Uts and the 2 M ATS
Authors: Reinheimer, Th.; Weigelt, G.
Bibcode: 1997svlt.work..389R
Altcode:
No abstract at ADS
Title: Interferometric Studies of Late Phases of Stellar Evolution
Authors: Weigelt, G.; Balega, Y.; Hofmann, K. -H.; Langer, N.;
Osterbart, R.
Bibcode: 1997svlt.work..206W
Altcode:
No abstract at ADS
Title: HST/GHRS Observations of the Compact Slow Ejecta of Eta Carinae
Authors: Davidson, Kris; Ebbets, Dennis; Johansson, Sveneric; Morse,
Jon A.; Hamann, Fredrick W.; Balick, B.; Humphreys, R. M.; Weigelt,
G.; Frank, A.
Bibcode: 1997AJ....113..335D
Altcode:
We report spectroscopic observations of eta Car and adjacent gas with
an unprecedented combination of spatial and spectral resolution, 0.1
arcsec x 0.1 Angstroms. Radial velocities show that the bright objects
C and D, 0.2 arcsec from the star, are slow equatorial ejecta. The
narrow emission lines which fluctuate in the spectrum of the core
region are found to originate in C, D, and related gas. Our data and
earlier speckle observations suggest that either C and D were formed
long after the Great Eruption of eta Car had ceased, or else they have
been continuously accelerated outward since they were ejected. These
strange objects are essential components of the equatorial-debris
puzzle, which is crucial regarding the nature of this star and its
instability. Moreover, the observed bright narrow emission lines in
CD are excited by peculiar mechanisms that deserve more attention.
Title: First diffraction-limited speckle masking observations of
the Mira variable R CAS with the 6m SAO telescope.
Authors: Weigelt, G.; Balega, Y.; Hofmann, K. -H.; Scholz, M.
Bibcode: 1996A&A...316L..21W
Altcode:
We present the first diffraction-limited speckle masking observations
of a Mira star with the Russian 6m SAO telescope. At 700 and 714nm
wavelength a resolution of 1.22λ/D=30milli-arcsec was achieved. The
reconstructed true images are the images with the highest resolution
obtained up to now in this wavelength region. The speckle interferograms
of R Cas were recorded through interference filters with center
wavelength/bandwidth of 714nm/6nm (strong TiO band absorption) and
700nm/6nm (moderate TiO absorption). The two reconstructed images show
that the azimuthally averaged 700 and 714nm uniform-disk diameters of
R Cas are 36mas+/-2mas and 49mas+/-2mas, respectively. In the 700nm
and 714nm images the disks of R Cas are non-uniform and elongated
along position angle 52+/-7deg and 57+/-7deg, respectively. The
size (ellptical uniform disk fit) of the elongated disks is about
33.3masx38.7mas (axial ratio 0.86) in the 700nm pseudo-continuum filter
and 42.3masx55.6mas (axial ratio 0.76) in the 714nm TiO absorption
band filter. We discuss briefly theoretical aspects of these and
previous observations.
Title: Simultaneous optical speckle masking and NIR adaptive optics
imaging of the 126mas Herbig Ae/Be binary star NX Puppis.
Authors: Schoeller, M.; Brandner, W.; Lehmann, T.; Weigelt, G.;
Zinnecker, H.
Bibcode: 1996A&A...315..445S
Altcode: 1996astro.ph..6053S
We present simultaneous optical and near-infrared high angular
resolution observations of the close Herbig Ae/Be binary star NX Pup
which is associated with cometary globule 1. The reconstructed images
have a diffraction-limited resolution of 62mas in V, 75mas in R (speckle
masking reconstruction), and 115mas in H, 156mas in K (adaptive optics +
post-processing). Compared to previous results we were able to derive
better estimates on spectral type and luminosity and hence put better
constraints on the evolutionary status (mass & age) of NX Pup A
and B: with NX Pup A of spectral type F0-F2 we estimate the spectral
type of NX Pup B in the range F7-G4, masses of 2Msun_ and
1.6-1.9Msun_, respectively, and an age of 3-5Myr for both
stars. We discuss the implication of the new age determination on
the physical relation between NX Pup and the cometary globule. The
dynamical lifetime of =~10^6^yr for cometary globule 1 suggests
that cometary globule 1 and the nearby cometary globule 2 represent
transient phenomena and are left overs of a larger molecular cloud
which in turn was the parental cloud of NX Pup A and B and finally
got dispersed by photoevaporation. The IR excess of NX Pup A can be
modeled by a viscous accretion disk, which is cut off at =~20AU from
the star. NX Pup B has a smaller IR excess which indicates that there
is less circumstellar material present than around the primary.
Title: VizieR Online Data Catalog: UV photometry of NGC 6397
(Burgarella+ 1994)
Authors: Burgarella, D.; Paresce, F.; Meylan, G.; King, I. R.;
Greenfield, P.; Baxter, D.; Jedrzejewski, R.; Nota, A.; Albrecht, R.;
Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng,
J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.; Macchetto, F.;
Mackay, C. D.; Weigelt, G.
Bibcode: 1996yCat..32870769B
Altcode:
The core of the nearby and very concentrated globular cluster NGC 6397
has been imaged through the f/96-F140W, f/48-F140W, f/96-F210M and
f/48-F220W ultraviolet filters of the Faint Object Camera on board
the Hubble Space Telescope down to an ultraviolet limiting magnitude
of ~19. The most interesting objects in the field of view are six
very bright centrally concentrated, blue stragglers observed for the
first time in the UV. Using these and other data from ground-based
observations, we have been able to deduce from a comparison with
Kurucz's atmosphere models, temperatures of ~10000K and masses of
~1.6M⊙ for the four brightest ones, which is remarkably
close to twice the turn-off mass of NGC 6397. This finding supports the
idea that two-star mechanisms (collisions, mergers) are at the origin of
the blue stragglers in the core of NGC 6397. Since the central density
is very high, collisions between main sequence stars are frequent,
therefore providing the best formation mechanism. We have computed
the number of such collisions in the core of NGC 6397 and found it to
be of the same order as the number of bright blue stragglers observed
there. Thanks to the HST resolution, we have also been able to resolve
one object, previously classified as a yellow straggler, into a blend
of a blue straggler and three redder stars. (1 data file).
Title: Simultaneous optical speckle and ADONIS imaging of the 126
mas Herbig Ae/Be binary star NX Puppis.
Authors: Brandner, W.; Lehmann, T.; Schöller, M.; Weigelt, G.;
Zinnecker, H.
Bibcode: 1996Msngr..83...43B
Altcode:
The authors have obtained simultaneous high spatial resolution optical
speckle and near-infrared adaptive optics images of the 126 mas Herbig
Ae/Be binary star NX Pup and could derive accurate estimates for the
evolutionary status of both components. Furthermore, they were able to
decompose the overall spectral energy distribution into its constituent
parts, namely the contribution of the two stellar photospheres and
the infrared excess due to circumstellar material associated with
both stars.
Title: Speckle-masking imaging polarimetry of η Carinae: evidence
for an equatorial disk.
Authors: Falcke, H.; Davidson, K.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1996A&A...306L..17F
Altcode: 1996astro.ph..1119F
With our new speckle imaging polarimeter we have obtained the first
polarimetric images witharcsecond resolution of the Luminous
Blue Variable η Carinae in the Hα line. The polarization patterns at
the 3" scale match well earlier conventional imaging photometry and
can be interpreted as Mie scattering. In crosscorrelation-centered
images we detected in polarized light a bar in the NE part of the
equatorial plane of η Carinae. High-resolution 0.11" polarimetric
speckle reconstructions reveal a compact structure elongated in the
same direction which is consistent, in degree and position angle of the
polarisation, with the presence of a circumstellar, equatorial disk. The
degree of polarization of the previously discovered speckle objects and
the Hα arm is relatively low (~10%) and thus may indicate a position
within the equatorial plane. We also discovered a highly polarized
(20%-40%) bipolar structure along the major axis of the Homunculus
nebula which can be traced down to the sub-arcsecond scale. This is
probably the inner part of a bipolar outflow into the Homunculus.
Title: Is there a Dichromatic UV Laser in Eta Carinae?
Authors: Johansson, S.; Davidson, K.; Ebbets, D.; Weigelt, G.; Balick,
B.; Frank, A.; Hamann, F.; Humphreys, R. M.; Morse, J.; White, R. L.
Bibcode: 1996swhs.conf..361J
Altcode:
No abstract at ADS
Title: Diffraction-limited images of the Mira-type variable R Cas.
Authors: Hofmann, K. -H.; Balega, Y. Y.; Scholz, M.; Shkhagosheva,
Z. U.; Weigelt, G.
Bibcode: 1996BSAO...39...59H
Altcode:
The authors present the first diffraction-limited speckle masking
observations of the long-period variable star R Cas with the 6 m SAO
telescope. At 700 nm wavelength the resolution of the reconstructed
images is λ/D = 25 mas. Speckle interferograms were recorded
through interference filters with centre wavelength/bandwidth of 714
nm/6 nm (strong TiO absorption band) and 700 nm/6 nm (moderate TiO
absorption). The two reconstructed images show that the average 700
nm diameter of R Cas is 37±2 mas, while the average 714 nm diameter
is 50±3 mas. Both images show the elliptical shape with an axis ratio
of about 0.8.
Title: Speckle masking observations of R 64, the dense stellar core
of the OB association LH9 in the Large Magellanic Cloud.
Authors: Schertl, D.; Hofmann, K. -H.; Seggewiss, W.; Weigelt, G.
Bibcode: 1995A&A...302..327S
Altcode:
We present speckle masking observations of R 64 (=HD 32228; O9.5II:
+ WC5), the central object of the OB association LH9 in the Large
Magellanic Cloud. Two sets of speckle interferograms were taken to
select the Johnson V spectral band and the strong Wolf-Rayet emission
lines between 450 and 490nm. In the 6.4"x6.4" field of view 25 stellar
components were detected in R 64 with V magnitudes in the range 12.5 to
17.1 and down to a resolution of 0.12". The brightest star in the visual
component B is the only Wolf-Rayet star in R 64. The colour-magnitude
diagram of LH9, completed with the components of R 64, serves for
the discussion of the evolutionary state of the association. There is
evidence that the outer regions of LH9 are its youngest parts with an
upper age of about 5Myr, in accordance with estimates by Walborn &
Parker (1992). The WC5 star in the centre is most likely the product of
mass exchange in a massive close binary system with an age in excess
of 5Myr. The mass density in R 64 is about 250Msun_pc^-3^
for stars more massive than 5Msun_.
Title: Speckle masking observations of HD 97950 with 75 MAS
resolution: evolution of the stellar core of the starburst cluster
NGC 3603.
Authors: Hofmann, K. -H.; Seggewiss, W.; Weigelt, G.
Bibcode: 1995A&A...300..403H
Altcode:
We present diffraction-limited speckle masking observations of
the central object HD 97950 in the giant HII region and starburst
cluster NGC 3603. In the reconstructed images 28 stellar components
with V magnitudes in the range from 11.40 to 15.85 were detected in
the 6.3x6.3" (about 0.2x0.2pc) field of view. Four different filters
were used for the selection of distinct spectral regions comprising
Hα emission, the main Wolf-Rayet and Of-type emission lines, and two
continuum bands. The angular resolutions of the four reconstructed
images are 0.080" (RG695 filter), 0.075" (658nm), 0.079" (545nm),
and 0.174" (471nm). Two WN stars and two further stars with mild
WN-type characteristics were found. A colour-magnitude diagram has
been constructed. Isochrone fits taken from the new grids of stellar
models from Schaller et al. (1992), yield a cluster age of about
3.2Myr which is in accordance with the time-scale of Wolf-Rayet star
evolution and places NGC 3603 in the Carina nebula phase of young
stellar aggregates. The initial mass function IMF of HD 97950 has a
fairly steep slope of x=1.59, in contrast to other Local Group giant
HII regions and to starburst galaxies. HD 97950 has, compared to
the cores of extragalactic HII regions, a similar, but high number
ratio of WN to OB-type stars, indicating an instantaneous burst
of star formation. HD 97950 hosts OB-type stars with a total mass
of about 1000Msun_, corresponding to a mass density of
~10^5^Msun_/pc^3^. Thus, HD 97950 is even more compact than
R136a, the core of the giant HII region 30 Dor in the LMC.
Title: HST FOC Observations of Eta Carinae
Authors: Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Davidson, K.; Deharveng, J. M.; Disney,
M. J.; Jakobsen, P.; Kamperman, T. M.; King, I. R.; Macchetto, F.;
Mackay, C. D.; Paresce, F.; Baxter, D.; Greenfield, P.; Jedrzejewski,
R.; Nota, A.; Sparks, W. B.
Bibcode: 1995RMxAC...2...11W
Altcode:
No abstract at ADS
Title: Morphology and Kinematics of Eta Carinae
Authors: Duschl, W. J.; Hofmann, K. -H.; Rigaut, F.; Weigelt, G.
Bibcode: 1995RMxAC...2...17D
Altcode: 1994astro.ph.10090D
We present a high-resolution image of $\eta$~Car. Together with IR and
visual observations of the central arcsecond, we use this to discuss the
morphological structure of $\eta$~Car on the different length scales. We
identify three different structural components: a bipolar outflow,
an equatorial disk of streamers, and the speckle objects. We discuss
models for the kinematics of the whole complex, and propose observations
that could settle the question of the structure of $\eta$~Car.
Title: HST/FOS Spectroscopy of ETA Carinae: The Star Itself, and
Ejecta Within 0.3 Arcsec
Authors: Davidson, Kris; Ebbets, Dennis; Weigelt, Gerd; Humphreys,
Roberta M.; Hajian, Arsen R.; Walborn, Nolan R.; Rosa, Michael
Bibcode: 1995AJ....109.1784D
Altcode:
Ground-based spectroscopy of η Car includes at least four components
ABCD within a core region less than 0.4 across, and usually other
material as well. Using the Hubble Space Telescope (HSTs) Faint Object
Spectrograph (FOS), we have obtained separate data on component A and on
B+C+D. Object A is found to be the central star; this is the fist time
that the spectrum of the star η Car has been observed without a severe
contamination by surrounding ejecta.The spectrum is that of a hot dense
stellar wind with a mass-loss rate of the order of 10-3 solar
mass/yr. A more detailed nonspherical analysis of the data has not yet
been done. Objects BCD appear to be ejecta rather than companion stars,
since their combined spectrum has many forbidden lines with no sign
of any stellar spectrum different from that of A. Exitation mechanisms
in BCD are of great interest and deserve more theoretical study.
Title: High-resolution speckle masking observations of Ceres and Vesta
Authors: Schertl, D.; Grieger, F.; Hofmann, K. -H.; Mauder, W.;
Reinheimer, T.; Weghorn, H.; Weigelt, G.
Bibcode: 1995P&SS...43..313S
Altcode:
We present high-resolution speckle masking observations of the asteroids
Ceres and Vesta and a detailed description of the image processing
methods applied. The edges of the asteroid disks are reconstructed with
high signal-to-noise ratio. On the surface of Ceres very weak surface
features are visible. The Vesta image shows high-contrast features. At
the time of the observations, Ceres had an apparent angular diameter
of 0.74 arcsec (905 km) and Vesta 0.45 arcsec × 0.44 arcsec (539 km ×
519 km). For the reconstruction of the asteroid images it was necessary
to develop a new method for the compensation of the four-dimensional
photon bias in the average bispectrum of the speckle interferograms. The
dependence of the reconstruction on the photon bias compensation and
on the compensation of the speckle interferometry transfer function
is investigated to study the robustness of the method.
Title: Faint Object Camera Imaging and Spectroscopy of NGC 4151
Authors: Boksenberg, A.; Catchpole, R. M.; Macchetto, F.; Albrecht,
R.; Barbieri, C.; Blades, J. C.; Crane, P.; Deharveng, J. M.; Disney,
M. J.; Jakobsen, P.; Kampermann, T. M.; King, I. R.; Mackay, C. D.;
Paresce, F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski,
R.; Nota, A.; Sparks, W. B.
Bibcode: 1995ApJ...440..151B
Altcode:
We describe ultraviolet and optical imaging and spectroscopy within the
central few arcseconds of the Seyfert galaxy NGC 4151, obtained with
the Faint Object Camera on the Hubble Space Telescope. A narrowband
image including [O III] λ5007 shows a bright nucleus centered on a
complex biconical structure having apparent opening angle ~65^deg^ and
axis at position angle along 65^deg^-245^deg^; images in bands including
Lyman-α and C IV λ1550 and in the optical continuum near 5500 A, show
only the bright nucleus. In an off-nuclear optical long-slit spectrum
we find a high and a low radial velocity component within the narrow
emission lines. We identify the low-velocity component with the bright,
extended, knotty structure within the cones, and the high- velocity
component with more confined diffuse emission. Also present are strong
continuum emission and broad Balmer emission line components, which
we attribute to the extended point spread function arising from the
intense nuclear emission. Adopting the geometry pointed out by Pedlar
et al. (1993) to explain the observed misalignment of the radio jets
and the main optical structure we model an ionizing radiation bicone,
originating within a galactic disk, with apex at the active nucleus
and axis centered on the extended radio jets. We confirm that through
density bounding the gross spatial structure of the emission line
region can be reproduced with a wide opening angle that includes the
line of sight, consistent with the presence of a simple opaque torus
allowing direct view of the nucleus. In particular, our modelling
reproduces the observed decrease in position angle with distance from
the nucleus, progressing initially from the direction of the extended
radio jet, through our optical structure, and on to the extended
narrow-line region. We explore the kinematics of the narrow-line low-
and high-velocity components on the basis of our spectroscopy and
adopted model structure. For the low-velocity system both Keplerian
rotation and isotropic outflow (or outflow confined to the ionizing
cone) give plausible correspondence with our data. If interpreted as
rotation we show consistency with earlier determinations indicating
a central mass concentration of about 10^9^ M_sun_. The high-velocity
system kinematically conforms to radial outflow within the galaxy disk,
although this does not well reproduce the observed intensity structure.
Title: Resolution and evolution of the core of the giant HII region
NOC 3603
Authors: Hofmann, K. -H.; Weigelt, G.; Seggewiss, W.
Bibcode: 1995IAUS..163...43H
Altcode:
No abstract at ADS
Title: Diffraction-limited speckle masking observations of the Mira
variable R Cas with the 6-m SAO telescope
Authors: Hofmann, K. -H.; Balega, Y.; Scholz, M.; Weigelt, G.
Bibcode: 1995IAUS..176P..45H
Altcode:
No abstract at ADS
Title: Imaging with the VLT Interferometer in the multi-speckle mode.
Authors: Reinheimer, T.; Hofmann, K. -H.; Schöller, M.; Weigelt, G.
Bibcode: 1995svlt.confP..81R
Altcode:
The authors present computer and laboratory experiments of
interferometric imaging in the multi-speckle mode with arrays similar
to the ESO Very Large Telescope Interferometer. The multi-speckle
long-baseline interferograms consist of many speckles with interference
fringes in each speckle. Diffraction-limited images with about
1 milli-arcsec resolution were reconstructed by the speckle masking
method (triple correlation or bispectral processing) and the iterative
building block method.
Title: High-Resolution Imaging with the VLT at Optical Wavelengths
Authors: Weigelt, G.
Bibcode: 1995svlt.conf..415W
Altcode:
No abstract at ADS
Title: Limiting magnitude of speckle masking observations with
VLT telescopes.
Authors: Hofmann, K. -H.; Reinheimer, T.; Weigelt, G.
Bibcode: 1995svlt.confP..87H
Altcode:
The authors present computer simulations of high-resolution speckle
imaging with the ESO VLT 8 m telescope. The experiments show that
in nights of good seeing with r0 = 26 cm (≡0.4″
diffraction-limited (0.014″at λ = 500 nm) images of 17m
objects can be reconstructed by speckle masking plus building
block method from 100000 speckle interferograms recorded in 40 min
observing time. Additionally, a SNR comparison of actual astronomical
observations with computer simulations shows that computer simulations
yield very useful predictions of the quality of astronomical speckle
reconstruction.
Title: Diffraction-limited images of the Mira-type variable R Cas.
Authors: Hofmann, K. -H.; Balega, Y. Y.; Scholz, M.; Shkhagosheva,
Z. U.; Weigelt, G.
Bibcode: 1995BSAO...39...59H
Altcode:
No abstract at ADS
Title: Preliminary design document for the Visible High Angular
Resolution Camera (VHARC).
Authors: Weigelt, G.
Bibcode: 1994fvlt.conf...77W
Altcode:
No abstract at ADS
Title: Speckle masking observations of the young binary Z Canis
Majoris.
Authors: Barth, W.; Weigelt, G.; Zinnecker, H.
Bibcode: 1994A&A...291..500B
Altcode:
We present the first speckle masking observations of the pre-main
sequence binary system Z CMa at optical wavelengths (narrow-band
R filter and edge filter RG 610). The diffraction-limited images
confirm that Z CMa is a binary with a separation of 0.100+/-0.008"
at position angle 305+/-2deg. The intensity ratio of the stars is
7.2 for the narrow-band R filter and 7.7 for the RG610 filter. The
south-eastern component is the brighter component (i.e. the FU Ori
object), in agreement with the results of Koresko et al. (1991)
based on near-infrared speckle data. However, our optical detection
of the north-western component (the infrared companion) would
not have been expected according to Koresko et al.'s analysis. One
possible explanation could be scattered light. This agrees with recent
polarimetric evidence from Whitney et al. (1993) that scattering plays
a role in seeing the infrared companion. We discuss the possibility
that both components of the Z CMa system may be FU Ori objects.
Title: The W Ursae Majoris system ER Ori: a multiple star.
Authors: Goecking, K. -D.; Duerbeck, H. W.; Plewa, T.; Kaluzny, J.;
Schertl, D.; Weigelt, G.; Flin, P.
Bibcode: 1994A&A...289..827G
Altcode:
308 photoelectric and 29 spectroscopic observations of the W-type W UMa
system ER Ori are presented and analyzed. A cross-correlation method
was used to determine the radial velocity curves. The existence of a
third body was established by its presence in the cross-correlation
function. High-resolution speckle masking observations show that
this companion has a separation of 0.19" from the W UMa system,
is about 2.3mag fainter than the binary at maximum light, and is
very likely physically connected to the system. The (O-C)-diagram
of minimum times was re-analyzed. The light time effect caused by
the third body has only a marginal influence, indicating that its
orbital plane has an inclination close to 0deg. The presence of the
companion was taken into account in the synthetic light and radial
velocity curve study. This combined solution yields a mass ratio of
q=0.64 +/-0.08. The derived masses and radii indicate that ER Ori is
a slightly evolved W UMa system.
Title: The massive star content of the blue dwarf galaxy IZw 36 from
Faint Object Camera observations
Authors: Deharveng, J. -M.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Disney, M. J.; Jakobsen, P.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1994A&A...288..413D
Altcode:
We have observed the blue dwarf galaxy IZw 36 with the f/96 relay of
the Faint Object Camera and have for the first time resolved massive
stars, using the broad band filters F175W, F342W, F430W and F480LP. We
have measured the fluxes of 143 of these objects and studied their
characteristics in color-magnitude diagrams. A few stars may be red
supergiants but their contribution to the integrated light is less than
5% in the F430W filter. The F175W-F430W color of the integrated stellar
population is redder than expected from the current burst of star
formation, suggesting therefore the presence of an older and unresolved
underlying population. The ultraviolet measurements combined with
synthetic photometry calculations allow us to place the massive stars
in a bolometric magnitude vs. temperature diagram. In this diagram,
the stars are compared to evolutionary tracks for different stellar
masses. The current burst probably has an age less than 12 Myr. We
infer an Initial Mass Function, with a power-law slope in the range
-1.7 to -2.6 for masses M>20Msun_. This is consistent
with most of the values reported for sites of star formation in the
Galaxy and the Magellanic Clouds and does not support the view of an
IMF flattening at low metallicity.
Title: HST observations of the core of globular cluster NGC 6397
Authors: Burgarella, D.; Paresce, F.; Meylan, G.; King, I. R.;
Greenfield, P.; Baxter, D.; Jedrzejewski, R.; Nota, A.; Albrecht, R.;
Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng,
J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.; Macchetto, F.;
Mackay, C. D.; Weigelt, G.
Bibcode: 1994A&A...287..769B
Altcode:
The core of the nearby and very concentrated globular cluster NGC
6397 has been imaged through the f/96-F140W, f/48-F140W, f/96-F210M,
and f/48-F220W ultraviolet filters of the Faint Object Camera on board
the Hubble Space Telescope down to an ultraviolet limiting magnitude
of ~19. The most interesting objects in the field of view are six
very bright, centrally concentrated, blue stragglers observed for the
first time in the UV. Using these and other data from ground-based
observations, we have been able to deduce from a comparison with
Kurucz's atmosphere models, temperatures of ~10000 K and masses of
~1.6Msun_ for the four brightest ones, which is remarkably
close to twice the turn-off mass of NGC 6397. This finding supports the
idea that two-star mechanisms (collisions, mergers) are at the origin of
the blue stragglers in the core of NGC 6397. Since the central density
is very high, collisions between main sequence stars are frequent,
therefore providing the best formation mechanism. We have computed
the number of such collisions in the core of NGC 6397 and found it to
be of the same order as the number of bright blue stragglers observed
there. Thanks to the HST resolution, we have also been able to resolve
one object, previously classified as a yellow straggler, into a blend
of a blue straggler and three redder stars.
Title: High resolution optical images of the starburst ring around
the Seyfert nucleus of NGC7469
Authors: Mauder, W.; Weigelt, G.; Appenzeller, I.; Wagner, S. J.
Bibcode: 1994A&A...285...44M
Altcode:
We present speckle masking observations of the core of the Seyfert plus
circumnuclear starburst hybrid galaxy NGC7469. High-resolution images
were obtained in three different wavelength bands. The images show a
ring-shaped emission region with a radius of about 1".3 (~ 400 pc at a
distance of 65 Mpc) consisting of about a dozen individual cloud-like
features. Near the center of the ring we find a bright unresolved source
superimposed on an extended and elongated structure extending about +/-
0".4 towards the PAs 50deg and 230deg.
Title: Optical interferometry in the multi-speckle mode
Authors: Reinheimer, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1994IAUS..158..373R
Altcode:
No abstract at ADS
Title: Speckle detection of the Z CMa infrared companion at optical
wavelengths
Authors: Weigelt, G.; Zinnecker, H.
Bibcode: 1994ASPC...62..323W
Altcode: 1994nesh.conf..323W
No abstract at ADS
Title: Interferometric imaging with arrays of large optical telescopes
in the multi-speckle mode
Authors: Reinheimer, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1993A&A...279..322R
Altcode:
We present a method for interferometric imaging with arrays of
large optical telescopes in the multi-speckle mode. The raw data
were produced by simulating light propagation in the atmosphere,
various pupil functions similar to the pupil function of the European
Southern Observatory (ESO) Very Large Telescope Interferometer (four
8-m telescopes), earth rotation, and photon noise. The generated
data sets consist of up to 48,000 interferograms per experiment
with 100 to 80,000 photoevents per interferogram. Since a Fried
parameter r0 smaller than the telescope diameter was chosen,
multi-speckle long-baseline interferograms were obtained which consist
of many speckles with interference fringes in each speckle. This
experimental condition is called the multi-speckle mode, which is
typical for interferometric imaging with large telescopes at optical
wavelengths. From the various data sets diffraction-limited images were
reconstructed by the speckle masking method (bispectral analysis) and
the iterative building block method. Image reconstruction is possible
without the use of non-redundant masks since speckle masking is a
generalization of phase closure imaging to highly redundant arrays (or
large optical telescopes). The reconstructed images show the dependence
of the signal-to-noise ratio on photon noise and other parameters. The
proposed method can also be applied to radio interferometric data
(especially, mm- or or sub-mm-observations).
Title: Faint Object Camera Far-Ultraviolet Objective Prism
Observations of 12 Z > 3 Quasars
Authors: Jakobsen, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1993ApJ...417..528J
Altcode:
We present the first results of an exploratory objective prism survey
of the far-ultraviolet (λλ1200-1800) spectra of high-redshift
quasars obtained with the Faint Object Camera on-board the Hubble
Space Telescope. The prime objective of this survey is to identify
one or more candidates among the known quasars at Ζem
> 3 with sufficient flux at far-ultraviolet wavelengths to enable
detailed follow-up observations of redshifted intergalactic He II λ304
absorption using the HST grating spectrographs FOC prism observations
of 12 prime candidates selected for redshift (Ζem
≃ 3.03-3.66), brightness (V ≲ 18.5) and the appearance of their
optical absorption spectra are presented and discussed. As anticipated
beforehand, cumulative neutral hydrogen Lyman continuum absorption from
the various classes of intervening absorption systems presents a serious
obstacle for observing high redshift quasars at extreme ultraviolet
rest energies. At our limiting sensitivity of Fλ ≃ 2-4 ×
10-16 ergs s-1 cm-2 Å-1,
10 of the 12 objects observed show no far-UV flux shortward of λ1800
observed wavelength. Two objects, Q0114-089 (UM 670; Ζem ≃
3.16) and Q1442+102 (OQ 172; Ζem = 3.53) are detected, but
only down to 330 Å and 345 Å rest wavelength. No object is reliably
detected at emitted He II λ304. The severity of the cumulative Lyman
continuum absorption is, however, such that these preliminary findings
are still statistically consistent with the hypothesis that luminous
quasars are intrinsically bright at extreme ultraviolet energies at
flux levels comparable to those suggested by extrapolation of the
power law continua seen at longer wavelengths. A larger number of
high-redshift quasars need to be observed in the far-UV before the
prospects for observing intergalactic He II λ304 absorption with HST
can be fully appraised.
Title: High Resolution Imaging of Galaxy Cores
Authors: Crane, P.; Stiavelli, M.; King, I. R.; Deharveng, J. M.;
Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Disney,
M. J.; Jakobsen, P.; Kamperman, T. M.; Machetto, F.; Mackay, C. D.;
Paresce, F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski,
R.; Nota, A.; Sparks, W. B.
Bibcode: 1993AJ....106.1371C
Altcode:
Surface photometry data obtained with the Faint Object Camera of the
Hubble Space Telescope in the cores of ten galaxies is presented. The
major results are: (i) none of the galaxies show truly "isothermal"
cores, (ii) galaxies with nuclear activity show very similar light
profiles, (iii) all objects show central mass densities > 10^3^M_sun_
pc^-3^, (iv) four of the galaxies (M87, NGC 3862, NGC 4594, NGC 6251)
show evidence for exceptional nuclear mass concentrations.
Title: Iterative image reconstruction from the bispectrum.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1993A&A...278..328H
Altcode:
We present iterative least-squares methods for reconstructing
diffraction-limited images from the object bispectrum obtained
by speckle masking (bispectral analysis) and from other Fourier
data. The theory and first astronomical speckle masking applications
are described. An approximation of the least-squares integral is derived
which makes it possible to calculate easily thousands of iterations with
images of 512x512 pixels. Various extensions of the basic method to the
simultaneous treatment of many object pixels are discussed. Finally,
applications of modified versions of the method to the Knox-Thompson
method, shearing interferometry, deconvolution of aberrated images,
optical long-baseline interferometry, radio interferometry (especially,
mm- and submm-interferometry) and other methods are discussed.
Title: SISTERS: a space interferometer for the search for terrestrial
exo-planets by rotation shearing
Authors: Bely, Pierre Y.; Burrows, Christopher J.; Roddier, Francois
J.; Weigelt, Gerd; Bernasconi, M. C.
Bibcode: 1993SPIE.1947...73B
Altcode:
A concept for a space-based interferometer dedicated to the detection
of extrasolar earth-like planets is presented. Detection is done in
the near infrared (10 micrometers ) where the expected star to planet
flux ratio is down to 10(superscript 6) compared to 10(superscript 10)
in the visible. The longer wavelength also makes is easier to avoid
light scatter due to optics micro-roughness. Parent star cancellation is
obtained with a rotation shearing interferometer working at its null on
axis. The interferometer is of the Fizeau configuration with an aperture
composed of twelve 1.2 meter mirrors on a 20 meter ring. This size,
which corresponds to a resolving power of 0.05 arcsecond, allows for
the investigation of about 30 candidate stars. The interferometer is
supported by a chemically rigidized structure deployed by inflation. All
optical elements are passively cooled to about 70 degrees Kelvin to
reduce the instrumental infrared background. The spacecraft is located
at the second Lagrangian point of the earth-sun system in order to
minimize attitude control and baffling requirements.
Title: HARDI-2: a high-angular-resolution deployable interferometer
for UV observations of nearby stars
Authors: Bely, Pierre Y.; Burrows, Christopher J.; Lamers, H. J.;
Roddier, Francois J.; Weigelt, Gerd
Bibcode: 1993SPIE.1947...84B
Altcode:
We describe a concept for an orbiting astronomical observatory which
will allow high spatial resolution far-UV observations of nearby
stars. The scientific goal is to study stellar activity and mass
loss using imaging and spectroscopy. Specific areas of study include
stellar surfaces, large scale magnetohydroynamic effects, interacting
binaries and stellar winds. The instrument is an interferometer with
an 8-meter baseline providing 3 milliarcseconds resolution at 1200
Angstrom. The interferometer configuration is of the Fizeau type which
affords excellent ultraviolet throughput because of the small number
of reflections. The collecting aperture is composed of six 0.6 meter
diameter elements distributed on a circle in such a way as lead to near
uniform u-v plan coverage when the instrument is rotated around the
line of sight. This will lead to excellent imaging capabilities. The
interferometer individual channels are kept coaligned and coherent
using the light of a nearby guide star. The supporting structure is
folded for launch and automatically deployed once on orbit. To minimize
disturbance torques and thermal shocks, the spacecraft will be located
on a high earth orbit or at the Lagrangian point.
Title: Detection of an Ultraviolet and Visible Counterpart of the
NGC 6624 X-Ray Burster
Authors: King, I. R.; Stanford, S. A.; Albrecht, R.; Barbieri, C.;
Blades, J. C.; Boksenberg, A.; Crane, P.; Disney, M. J.; Deharveng,
J. M.; Jakobsen, P.; Kamperman, T. M.; Macchetto, F.; Mackay, C. D.;
Paresce, F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski,
R.; Nota, A.; Sparks, W. B.; Sosin, C.
Bibcode: 1993ApJ...413L.117K
Altcode:
We have detected, in images taken with the HST FOC, the UV and optical
counterpart of the X-ray source 4U 1820-30 in the globular cluster
NGC 6624. Astrometric measurements place this object 2 sigma from
the X-ray position of 4U 1820-30. The source dominates a far-UV FOC
image and has the same flux at 1400 A as was seen through the large
IUE aperture by Rich et al. (1993). It has a B magnitude of 18.7 but
is not detected in V. It is 0.66 arcsec from the center of NGC 6624,
a fact that may change the interpretation of the P-average of the 11
minute binary orbit. The flux drops between 1400 and 4300 A at a rate
that is nearly as steep as that of a Rayleigh-Jeans curve. The flux is
far too large to come from the neutron star directly but could accord
with radiation from a heated accretion disk and/or the heated side of
the companion star.
Title: Astronomical speckle masking, speckle spectroscopy, and
long-baseline interferometry
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1993wprm.conf..188H
Altcode:
No abstract at ADS
Title: Interferometric Imaging with Arrays of Large Optical Telescopes
in the Multispeckle Mode
Authors: Reinheimer, T.; Hofmann, K. -H.; Schöller, M.; Weigelt, G.
Bibcode: 1993SPIE.1983..197R
Altcode:
No abstract at ADS
Title: Iterative Image Reconstruction from the Bispectrum of
Astronomical Speckle Interferograms
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1993SPIE.1983..203H
Altcode:
No abstract at ADS
Title: Compensation of Photon Noise Bias Terms in Speckle Masking
and Astronomical Applications
Authors: Mauder, W.; Hofmann, K. -H.; Weigelt, G.; Zeidler, P.
Bibcode: 1993SPIE.1983..331M
Altcode:
No abstract at ADS
Title: Compact subarcsec structures of the double nucleus of NGC
6240 revealed with HST.
Authors: Barbieri, C.; Rafanelli, P.; Schulz, H.; Albrecht, R.;
Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney,
M. J.; Jakobsen, P.; Kamperman, T. M.; King, I. R.; Macchetto, F.;
Mackay, C. D.; Paresce, F.; Weigelt, G.; Baxter, D.; Greenfield, P.;
Jedrzewski, R.; Nota, A.; Sparks, W. B.
Bibcode: 1993A&A...273....1B
Altcode:
We have used the Faint Object Camera on board of the Hubble Space
Telescope to obtain a high spatial resolution ultraviolet image of the
central region of NGC 6240. This image resolves the well known double
nucleus of the galaxy into several compact knots with sizes 0.1"-0.2"
(about 45-90 pc for H_0_ = 75 km s^-1^Mpc^-1^) and extended low surface
brightness emission. The northern (fainter) component B of the double
nucleus of the galaxy contains only one bright compact source while the
southern (brighter) component A consists of a string of bright knots
plus more conspicuous extended emission than B. Evidence is presented
that an appreciable fraction (if not all) of the compact emission is
continuum light. The distance between the compact sources in A and B
exceeds the distance between the corresponding 2 cm radio sources by
~0.5". A comparison with precise optical coordinates shows that the
compact sources do not coincide with the radio sources. Extinction
by molecular clouds between A and B might explain why there are no
counterparts of the radio sources visible at shorter wavelengths. The
presence of an elliptical bubble of size ~190 x 150 pc within
an emitting region on the southwest of A could be due to multiple
supernova explosions.
Title: A study of the W UMa system ER Ori, a triple star.
Authors: Goecking, K. -D.; Duerbeck, H. W.; Plewa, T.; Kałuzny, J.;
Schertl, D.; Weigelt, G.; Flin, P.
Bibcode: 1993AGAb....9..139G
Altcode:
No abstract at ADS
Title: Landolt-Börnstein: Numerical Data and Functional Relationships
in Science and Technology - New Series " Gruppe/Group 6 Astronomy and
Astrophysics " Volume 3 Voigt: Astronomy and Astrophysics. Extension
and Supplement to Volume 2 " Instruments, Methods, Solar System
Authors: Baars, J. W.; Beer, H.; Durrant, C. J.; Graser, U.; Guinot,
B.; Hoffmann, M.; Hopp, U.; Ip, W. -H.; Jessberger, E. K.; Klecker, B.;
Lemke, D.; Meisenheimer, K.; Möbius, E.; Palme, H.; Rahe, J.; Röser,
H. J.; Schubart, J.; Schwenn, R.; Solf, J.; Soltau, G.; Staubert,
R.; Stewart, R.; Trümper, J.; Vanysek, V.; Weigelt, G.; Wolf, R.
Bibcode: 1993lbor.book.....B
Altcode:
No abstract at ADS
Title: Discovery of an Optical Synchrotron Jet in 3C 264
Authors: Crane, P.; Peletier, R.; Baxter, D.; Sparks, W. B.;
Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Deharveng,
J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.; King, I. R.;
Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt, G.; Greenfield,
P.; Jedrzejewski, R.; Nota, A.
Bibcode: 1993ApJ...402L..37C
Altcode:
Observations with the Faint Object Camera on board the Hubble Space
Telescope have revealed a new optical jet in the core of the elliptical
galaxy NGC 3862 (3C 264). Morphologically, this jet is similar to
the synchrotron jets seen in other galaxies, as it shows knots and
bifurcations. The optical spectral index [-d log I(v)/d log v = α =
1.4] is also similar to that found in other jets. Thus, the nucleus
of NGC 3862 appears to contain the fifth known example of an optical
synchrotron jet. Since NGC 3862 is a typical radio-loud elliptical
galaxy, it seems likely that many nonthermal jets found in the radio
continuum may also have optical counterparts.
Title: SISTERS: a space interferometer for the search for terrestrial
exo-planets by rotation shearing.
Authors: Bely, P. -Y.; Burrows, C. J.; Roddier, F.; Weigelt, G.;
Bernasconi, Marco C.
Bibcode: 1992ESASP.354...99B
Altcode: 1992tsbi.rept...99B
A concept for a space-based interferometer dedicated to the detection
of extrasolar earth-like planets is presented. Detection is done in the
near infrared (10 μm) where the expected star to planet flux ratio is
down to 106 compared to 1010 in the visible. The
longer wavelength also makes it easier to avoid light scatter due to
optics micro-roughness. Parent star cancellation is obtained with a
rotation shearing interferometer working at its null on axis.
Title: HARDI: a high angular resolution deployable interferometer.
Authors: Bely, P. -Y.; Burrows, C. J.; Roddier, F.; Weigelt, G.
Bibcode: 1992ESASP.354..235B
Altcode: 1992tsbi.rept..235B
The authors describe a proposed orbiting interferometer covering
the UV, visible and near-IR spectral ranges. With a 6-meter baseline
and a collecting area equivalent to about a 1.4 meter diameter full
aperture, this instrument is intended to offer significant improvements
in resolution over the Hubble Space Telescope, and complement the new
generation of ground-based interferometers with much better limiting
magnitude and spectral coverage.
Title: High-resolution imaging of solar system objects with space
telescopes and ground-based telescopes
Authors: Schertl, D.; Weigelt, G.
Bibcode: 1992AdSpR..12k.157S
Altcode: 1992AdSpR..12..157S
The atmosphere of the earth restricts the resolution of conventional
astronomical imaging with ground-based telescopes to about 0.5
arcsec. Much higher resolution can be obtained by interferometric
imaging with space telescopes or large ground-based telescopes. We
will discuss the following methods: (a)High-resolution imaging with
ground-based telescopes and interferometers. We will discuss the
principle and astronomical applications of speckle interferometry, the
Knox-Thompson method, the nonredundant mask technique, speckle masking,
speckle spectroscopy and optical long-baseline interferometry. For
example, speckle imaging with a 3.6-m telescope yields a resolution of
0.03 arcsec. We will show speckle masking observations of NGC 3603, the
Seyfert galaxy NGC 1068, and of the asteroids Ceres and Vesta. Optical
long-baseline interferometry with the ESO Very Large Telescope will
yield the fantastic resolution of 0.001 arcsec. The limiting magnitude
of speckle imaging is about 18th magnitude. (b)High-resolution
imaging with the Hubble Space Telescope. We will discuss the principle
of the roll deconvolution technique. At λ ~ 140 nm roll deconvolution
imaging with the HST will yield a resolution of about 0.015 arcsec.
Title: HARDI: A high angular resolution deployable interferometer
for space
Authors: Bely, Pierre Y.; Burrows, Christopher; Roddier, Francois;
Weigelt, Gerd
Bibcode: 1992NASCP3066..114B
Altcode: 1992loui.rept..114B
We describe here a proposed orbiting interferometer covering the
UV, visible, and near-IR spectral ranges. With a 6-m baseline and a
collecting area equivalent to about a 1.4 m diameter full aperture,
this instrument will offer significant improvements in resolution
over the Hubble Space Telescope, and complement the new generation
of ground-based interferometers with much better limiting magnitude
and spectral coverage. On the other hand, it has been designed as a
considerably less ambitious project (one launch) than other current
proposals. We believe that this concept is feasible given current
technological capabilities, yet would serve to prove the concepts
necessary for the much larger systems that must eventually be flown. The
interferometer is of the Fizeau type. It therefore has a much larger
field (for guiding) better UV throughout (only 4 surfaces) than phased
arrays. Optimize aperture configurations and ideas for the cophasing and
coalignment system are presented. The interferometer would be placed
in a geosynchronous or sunsynchronous orbit to minimize thermal and
mechanical disturbances and to maximize observing efficiency.
Title: Imaging of Four Planetary Nebulae in the Magellanic Clouds
Using the Hubble Space Telescope Faint Object Camera
Authors: Blades, J. C.; Barlow, M. J.; Albrecht, R.; Barbieri, C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Paresce, F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski,
R.; Nota, A.; Osmer, S.; Sparks, W. B.
Bibcode: 1992ApJ...398L..41B
Altcode:
Using the Faint Object Camera on-board the Hubble Space Telescope,
we have obtained images of four planetary nebulae (PNe) in the
Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the
LMC. Each nebula was imaged through two narrow-band filters isolating
[O III] λ5007 and Hβ, for a nominal exposure time of 1000 s in
each filter. Significant detail is evident on the raw images and,
after deconvolution using the Richardson-Lucy algorithm, structures
as small as 0.06" are easily discernible. In [O III], SMC N5 shows a
circular ring structure, with a peak-to-peak diameter of 0.26" and a
FWHM of 0.35", while SMC N2 shows an elliptical ring structure with
a peak-to-peak diameter of 0.26" x 0.21" (FWHM 0.40" x 0.35"). The
expansion ages corresponding to the observed structures in SMC N2 and
N5 are of the order of 3000 yr. Such low ages appear more easy to
reconcile with helium-burning rather than hydrogen-burning central
star evolutionary tracks. LMC N201 is very compact, with a FWHM of
0.21" in Hβ. The Type I PN LMC N66 is a multipolar nebula, with the
brightest part having an extent of about 2" and with fainter structures
extending over 4". The [O III] image reveals structures unprecedented
for a planetary nebula, with several bright knots and faint loops
visible outside the two main bright lobes.
Title: Speckle masking observations of the Seyfert galaxy NGC 1386.
Authors: Mauder, W.; Appenzeller, I.; Hofmann, K. -H.; Wagner, S. J.;
Weigelt, G.; Zeidler, P.
Bibcode: 1992A&A...264L...9M
Altcode:
We report high-resolution speckle masking observations of the Seyfert
galaxy NGC 1386. The Hα and RG 630 reconstructions show that the
spatially extended NLR of NGC 1386 consists of several knots distributed
in an elongated structure extending over more than 3". Some of the knots
are slightly resolved. The linear dimensions of these clouds ( >
15 pc) are comparable to the substructure found in NGC 1068. The cone
morphology suggests that the radiation characteristic of the nucleus is
asymmetric probably due to dust obscuration. The radial variation of the
emissivity measure implies a non-monotonic gradient of the gas density.
Title: Preliminary Analysis of an Ultraviolet Hubble Space Telescope
Faint Object Camera Image of the Center of M31
Authors: King, I. R.; Deharveng, J. M.; Albrecht, R.; Barbieri, C.;
Blades, J. C.; Boksenberg, A.; Crane, P.; Disney, M. J.; Jakobsen, P.;
Kamperman, T. M.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.; Stanford, S. A.
Bibcode: 1992ApJ...397L..35K
Altcode:
A 5161 s exposure was taken with the FOC on the central 44" of M31,
through a filter centered at 1750 A. Much of the light is redleak
from visible wavelengths, but nearly half of it is genuine UV. The
image shows the same central peak found earlier by Stratoscope, with
a somewhat steeper dropoff outside that peak. More than 100 individual
objects are seen, some pointlike and some slightly extended. We identify
them as post-asymptotic giant branch stars, some of them surrounded
by a contribution from their accompanying planetary nebulae. These
objects contribute almost a fifth of the total UV light, but fall far
short of accounting for all of it. We suggest that the remainder may
result from the corresponding evolutionary tracks in a population more
metal-rich than solar.
Title: Faint object camera observations of M 87 : the jet and nucleus.
Authors: Boksenberg, A.; Macchetto, F.; Albrecht, R.; Barbieri, C.;
Blades, J. C.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzjewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1992A&A...261..393B
Altcode:
Ultraviolet and optical images of the central region and jet of
the nearby elliptical galaxy M87 have been obtained with ~0.1
arcsec resolution in several spectral bands with the Faint Object
Camera (FOC) on the Hubble Space Telescope, including polarisation
images. Deconvolution enhances the contrast of the complex structure
and filamentary patterns in the jet already evident in the aberrated
images. Morphologically there is close similarity between the FOC images
of the extended jet and the best 2 cm radio maps obtained at similar
resolution, and the magnetic field vectors from the ultraviolet and
radio polarimetric data also correspond well. We observe structure in
the inner jet within a few tenths arcsec of the nucleus which also has
been well studied at radio wavelengths. Our ultraviolet and optical
photometry of regions along the jet shows little variation in spectral
index from the value 1.0 between markedly different regions and no
trend to a steepening spectrum with distance along the jet. The new
results strongly support the model for the jet in which there is no in
situ particle acceleration localized at strong shocks but electrons
accelerated at the nucleus propagate with low dissipation along the
inside of the jet and the observed synchrotron emission occurs primarily
in a boundary layer between the jet and its external medium. We observe
no evidence for a central star cluster. In the nucleus, our data show
the presence of an unresolved bright continuum source of optical to
ultraviolet spectral index ~1.4 and size <= 0.6 pc core radius (at
distance 16 Mpc), and an [O III]-emitting region of ~1.6 pc core radius.
Title: Report on the Lunar Interferometry Study Team (LIST)
activities.
Authors: Dainty, J. C.; Faucherre, M.; Greenaway, A. H.; Harris, A. I.;
Labeyrie, A.; Noordam, J. E.; Weigelt, G. P.; Beckers, J.; Lequeux,
J.; Fridlund, C. M.; Hawkyard, A.; Roussel, P. H.; Volonté, S.
Bibcode: 1992ESASP.344..259D
Altcode: 1992spai.rept..259D
During the first half of 1991, the Lunar Interferometry Study Team
(LIST) produced an Interim Report outlining a possible strategy for
the development of a lunar interferometry programme. The formulation
of an overall strategy for ESA towards lunar interferometry requires
further consideration before firm recommendations can be made. However,
it is clear at this early stage that there are three principal
elements in that strategy. (1) ESA should commence conceptual
studies for interferometers in readiness for their location on the
Moon in (a) the UV/visible/IR and (b) the sub-millimetre region. (2)
Considering the scientific benefit, technical readiness and realistic
timescale of a lunar interferometer, ESA should plan for at least one
"precursor" interferometer missions in space. (3) ESA should identify
key technologies of crucial importance to space-based interferometry
in general and lunar interferometry in particular, and support their
development by a variety of routes.
Title: Towards an ESA strategy for optical interferometry in
space. Recommendations of the ESA Space Interferometry Study Team
(SIST).
Authors: Noordam, J. E.; Bely, P. Y.; Faucherre, M.; Greenaway, A. H.;
Merkle, F.; Perryman, M. A. C.; Roussel, P. H.; Vakili, F.; Volonte,
S.; Weigelt, G. P.
Bibcode: 1992ESASP.344..255N
Altcode: 1992spai.rept..255N
In 1990, the Space Interferometry Study Team (SIST), a study group of
the European Space Agency, recommended the launch of a 100-m class
optical Space interferometer around the year 2005. The conclusions,
recommendations and target design parameters for such an interferometer
are summarised.
Title: Realtime Processing of Speckle Interferograms with Digital
Signal Processors
Authors: van Elst, M.; Weghorn, H.; Weigelt, G.
Bibcode: 1992ESOC...39..553V
Altcode: 1992hrii.conf..553V
No abstract at ADS
Title: Photon Bias Compensation in Speckle Interferometry and
Speckle Masking
Authors: Kerp, J.; Barth, W.; Hofmann, K. H.; Reinheimer, T.;
Weigelt, G.
Bibcode: 1992ESOC...39..269K
Altcode: 1992hrii.conf..269K
No abstract at ADS
Title: A Photon-Counting Method for Speckle Imaging
Authors: Mauder, M.; Weigelt, G.
Bibcode: 1992ESOC...39..611M
Altcode: 1992hrii.conf..611M
No abstract at ADS
Title: Photon bias compensation in triple correlation imaging and
observation of R 136.
Authors: Pehlemann, E.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1992A&A...256..701P
Altcode:
We report diffraction-limited speckle masking observations of the
central object R 136 in the 30 Doradus Nebula, and we describe a new
method for the compensation of the 4-dimensional photon bias terms in
the average bispectrum. More than 40 stellar components are present in
the 4.9" x 4.9" field of view of our reconstructed images. The closest
binaries found have separations between 0.03" and 0.05". Because
of the large number of photon events in our speckle interferograms,
it was not possible to apply photon counting techniques. Therefore,
the extended photon events caused various frequency-dependent bias
terms in the average image bispectrum. To overcome this influence of
photon noise, we have developed a new technique for the compensation
of the 4-dimensional photon bias terms in the bispectrum. We describe
the theory of the method and demonstrate its feasibility by various
image reconstruction experiments.
Title: Objective Prism Speckle Spectroscopy and Wideband Projection
Speckle Spectroscopy
Authors: Grieger, F.; Weigelt, G.
Bibcode: 1992ESOC...39..481G
Altcode: 1992hrii.conf..481G
No abstract at ADS
Title: Building Block Method - Image Reconstruction from the
Bispectrum Using an Iterative Algorithm
Authors: Hofmann, K. H.; Weigelt, G.
Bibcode: 1992ESOC...39..193H
Altcode: 1992hrii.conf..193H
No abstract at ADS
Title: Slit Speckle Spectroscopy
Authors: Weigelt, G.; Grieger, F.; Hofmann, K. H.; Pausenberger, R.
Bibcode: 1992ESOC...39..471W
Altcode: 1992hrii.conf..471W
No abstract at ADS
Title: High-Resolution Speckle Masking Observations of the Asteroids
Ceres and Vesta
Authors: Schertl, D.; Hofmann, K. H.; Weghorn, H.; Weigelt, G.
Bibcode: 1992ESOC...39..167S
Altcode: 1992hrii.conf..167S
No abstract at ADS
Title: Supernova Remnant / SNR Studies of Speckle Masking at Low
Light Levels
Authors: Barth, W.; Hofmann, K. H.; Weghorn, H.; Weigelt, G.
Bibcode: 1992ESOC...39..223B
Altcode: 1992hrii.conf..223B
No abstract at ADS
Title: High-Resolution Speckle Masking Observations of the Seyfert
Galaxy NGC1386
Authors: Zeidler, P.; Appenzeller, I.; Hofmann, K. H.; Mauder, W.;
Wagner, S.; Weigelt, G.
Bibcode: 1992ESOC...39...67Z
Altcode: 1992hrii.conf...67Z
No abstract at ADS
Title: Compensation of the Photon-Counting Hole in Triple Correlation
Processing - Laboratory Experiments
Authors: Cordel, A.; Hofmann, K. H.; Mauder, W.; Weigelt, G.
Bibcode: 1992ESOC...39..233C
Altcode: 1992hrii.conf..233C
No abstract at ADS
Title: Computer Simulations of Interferometric Imaging with the
VLT Interferometer
Authors: Reinheimer, T.; Hofmann, K. H.; Weigelt, G.
Bibcode: 1992ESOC...39..827R
Altcode: 1992hrii.conf..827R
No abstract at ADS
Title: High-Resolution Speckle Masking Observations of the Seyfert
Galaxy NGC1068
Authors: Hofmann, K. H.; Mauder, W.; Weigelt, G.
Bibcode: 1992ESOC...39...61H
Altcode: 1992hrii.conf...61H
No abstract at ADS
Title: Photon Bias Compensation in the Bispectrum and Speckle Masking
Observations of R:136
Authors: Pehlemann, E.; Hofmann, K. H.; Weigelt, G.
Bibcode: 1992ESOC...39...73P
Altcode: 1992hrii.conf...73P
No abstract at ADS
Title: High-resolution speckle masking observations of the asteroids
Ceres and Vesta
Authors: Schertl, D.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1992LIACo..30..363S
Altcode: 1992opps.conf..363S
No abstract at ADS
Title: High-Resolution Speckle Masking Observations of the Seyfert
Galaxy NGC1068
Authors: Hofmann, K. H.; Mauder, W.; Weigelt, G.
Bibcode: 1992pagn.conf..406H
Altcode:
No abstract at ADS
Title: High-Resolution Speckle Masking Observations of the Seyfert
Galaxy NGC1386
Authors: Zeidler, P.; Appenzeller, I.; Hofmann, K. H.; Mauder, W.;
Wagner, S.; Weigelt, G.
Bibcode: 1992pagn.conf..440Z
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: High-Resolution
Observations of the Central Object R136 in the 30 Doradus Nebula
Authors: Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Paresce, F.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.
Bibcode: 1991ApJ...378L..21W
Altcode:
R 136 is the luminous central object of the giant H II region 30 Doradus
in the Large Magellanic Cloud. We report on the first high- resolution
observations of RI 36 with the Faint Object Camera on board the Hubble
Space Telescope. The physical nature of the brightest component R136a
has been a matter of some controversy over the last few years. The
UV images obtained show that R136a is a very compact star cluster
consisting of more than eight stars within 0.7" diameter. From these
high-resolution images a mass upper limit can be derived for the most
luminous stars observed in R136.
Title: The Very Massive Objects R136A in the 30 Doradus Nebula,
NGC 3603 and Eta Carinae: Cycle 2
Authors: Weigelt, Gerd
Bibcode: 1991hst..prop.4073W
Altcode:
R136a is the core of the ionizing cluster NGC 2070 at the center of
the 30 Doradus nebula in the Large Magellanic Cloud. The interesting
question is whether R136 is a super- massive object or whether it is
a dense star cluster. We propose FOC imaging in order to solve the
question. The same observations are proposed in order to study the
nature HD 97950 AB in NGC 3603 and Eta Carinae. HD 97950 in NGC 3603
is probably of similar nature as R136.
Title: Blue stragglers in the core of the globular cluster 47 Tucanae
Authors: Paresce, F.; Shara, M.; Meylan, G.; Baxter, D.; Greenfield,
P.; Jedrzejewski, R.; Nota, A.; Sparks, W. B.; Albrecht, R.; Barbieri,
C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney,
M. J.; Jakobsen, P.; Kamperman, T. M.; King, I. R.; Macchetto, F.;
Mackay, C. D.; Weigelt, G.
Bibcode: 1991Natur.352..297P
Altcode:
High-resolution observations of the core of the globular cluster 47
Tucanae with the Faint Object Camera on the Hubble Space Telescope
reveal a high density of 'blue straggler' stars, occupying the upper
end of the main sequence from which all stars in the cluster should
have long since evolved. Their presence in the dense core supports the
hypothesis that they formed by stellar collision and coalescence, and,
as the heaviest objects in the cluster, have drifted to the core
Title: First Results from the Faint Object Camera: High-Resolution
Imaging of the Pluto-Charon System
Authors: Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.;
Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1991ApJ...374L..65A
Altcode:
The first observations of a solar system target with the Faint Object
Camera of the HST are reported. Observations of the Pluto-Charon
system were obtained in f/96 and f/288 mode. Pluto and Charon were
clearly resolved, and the observed separation and diameters are in
accordance with expectations. The f/96 data were astrometrically and
photometrically analyzed; preliminary results are presented.
Title: HST Observations of 3C 66B: A Double-stranded Optical Jet
Authors: Macchetto, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.; Miley, G. K.
Bibcode: 1991ApJ...373L..55M
Altcode:
The Faint Object Camera on the HST has imaged the central region of the
synchrotron jet in 3C 66B with ultra-high spatial resolutions. The
images have an angular resolution of 0.1'', corresponding to a
linear scale of about 40 pc. This is a factor of more than 12 better
linear resolution than previous optical images and more than 3 times
better than the best radio map obtained with the VLA. There is a
close correspondence between the general characteristics of the
smoothed optical image and the radio map, implying that the young
(<1000 yr) and old (>10^7^ yr) relativistic particles occupy
similar regions to within about 130 pc. Particularly intriguing is the
double-stranded filamentary nature of the jet which is clearly present
on the full-resolution images. This could reflect edge- brightening
effects due to enhanced radiation from a skinlike structure surrounding
the jet. A simple interpretation of the similarity of optical and
radio morphologies would imply that localized particle acceleration
occurs along the jet. However, the filamentary structure and filling
factor of the radiation would also be consistent with a model in which
the electrons are accelerated within the nucleus and are transported
along the jet in a channel having low magnetic field and consequent
low radiation losses.
Title: First Results from the Faint Object Camera: Images of the
Gravitational Lens System G2237+0305
Authors: Crane, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Bokensenberg, A.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.;
Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce,
F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota,
A.; Sparks, W. B.
Bibcode: 1991ApJ...369L..59C
Altcode:
Images of the gravitational lens system G2237+0305 have been obtained
with the Faint Object Camera on board the Hubble Space Telescope. A
preliminary analysis of these images is reported here and includes
measurements of the relative positions and magnitudes of the lensed
images of the QSO, and of the lensing galaxy. No evidence is found
for a fifth lensed image.
Title: Blue Stragglers in the Core of 47 Tucanae
Authors: Paresce, F.; Shara, M.; Meylan, G.; Macchetto, F.; Baxter,
D.; Blades, J. C.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.; Albrecht, R.; Barbieri, C.; Boksenberg, A.; Crane,
P.; Deharveng, J. M.; Disney, M. J.; Jacobsen, P.; Kamperman, T. M.;
King, I. R.; Mackay, C. D.; Weigelt, G.
Bibcode: 1991BAAS...23Q.948P
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: Observations of
PKS 0521-36
Authors: Macchetto, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1991ApJ...369L..55M
Altcode:
The Faint Object Camera on the Hubble Space Telescope was used to
observe the radio galaxy PKS 0521 - 36 which hosts a prominent radio
jet. Images of the jet show spatial structure comparable to VLA data
and significantly better than optical ground-based observations. The
jet structure is resolved at FOC resolution. In addition to the radio
knot, well resolved by the FOC, an extension of the jet toward the
nucleus is apparent. The rest of the jet does not show much clumpiness,
implying that the synchrotron electrons must be accelerated all along
the jet to account for the extent in the optical region.
Title: First Results from the Faint Object Camera: SN 1987A
Authors: Jakobsen, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.; Kirshner, R. P.; Panagia, N.
Bibcode: 1991ApJ...369L..63J
Altcode:
We present the first images of SN 1987A taken on day 1278 after
outburst with the Faint Object Camera on board the Hubble Space
Telescope. The supernova is well detected and resolved spatially in
three broadband ultraviolet exposures spanning the 1500-3800 A range
and in a narrow-band image centered on the [O III] λ5007 line. Simple
uniform disk fits to the profiles of SN 1987A yield an average angular
diameter of θ ~ 170 +/- 30 mas, corresponding to an average expansion
velocity of v ~ 6000 km s^-1^. The derived broadband ultraviolet fluxes,
when corrected for interstellar absorption, indicate a blue ultraviolet
spectrum corresponding to a color temperature near 13,000 K. The
luminosity of SN 1987A in the ultraviolet, L ~ 2 x 10^36^ ergs s^-1^,
is comparable to that emitted in the visible-through-infrared portion
of the spectrum. Finally, the narrow-band [O III] image reveals that the
circumstellar nebula known to surround SN 1987A has the shape of a thin,
tilted ring having a radius 0.20 pc and a thickness ~ 2 x 10^-2^ pc.
Title: First Results from the Faint Object Camera: Imaging the Core
of R Aquarii
Authors: Paresce, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.
Bibcode: 1991ApJ...369L..67P
Altcode:
The Faint Object Camera on the HST was pointed toward the symbiotic
long-period M7e Mira variable R Aquarii, and very high resolution
images of the inner core, mainly in the ionized oxygen emission lines
in the optical, are reported. Both images show bright arcs, knots,
and filaments superposed on a fainter, diffuse nebulosity extending
in a general SW-NE direction from the variable to the edge of the
field at 10 arcsec distance. The core is resolved in forbidden O
III 5007 A and forbidden O II 3727 A into at least two bright knots
of emission whose positions and structures are aligned with PA =
50 deg. The central knots appear to be the source of a continuous,
well-collimated, stream of material extending out to 3-4 arcsec in
the northern sector corresponding to a linear distance of about 1000
AU. The northern stream seems to bend around an opaque obstacle and form
a spiral before breaking up into wisps and knots. The southern stream is
composed of smaller, discrete parcels of emitting gas curving to the SE.
Title: Speckle lifetime and isoplanicity determinations: direct
measurements and derivation from turbulence and wind profiles.
Authors: Vernin, J.; Caccia, J. -L.; Weigelt, G.; Mueller, M.
Bibcode: 1991A&A...243..553V
Altcode:
Investigations of the lifetime of speckle interferograms and of
the space invariance or isoplanicity of speckle interferograms are
useful for optimizing high angular resolution imaging and for testing
existing and future astronomical observatory sites. In the periods
of Jan. 31 - Feb. 4 and Feb. 11-15, 1986, various measurements of
optical parameters of the atmosphere were made at the European Southern
Observatory, La Silla, Chile. At the 2.2-m telescope, measurements
of 23 speckle lifetimes τe and 10 isoplanicity angles θ
were performed. The methods used are described. Furthermore, several
turbulence profiles, CN2(h), and wind speed
profiles, V(h), have been obtained using different techniques which are
also described. Theoretical expressions allowing the calculation of
τe and θ from CN2(h) and V(h) are
presented. The calculated values of speckle lifetime and isoplanatic
angle are compared with direct correlation measurements. Good
agreement is found for the isoplanatic angle θ. For the speckle
lifetime τe, only partial agreement is found, i.e. very
good for one night, rather good for two nights, and very bad for the
last night. A possible explanation for the disagreement is presented.
Title: FOC / Faint Object Camera Images of the Gravitational Lens
System G:2237+0305
Authors: Crane, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.;
Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce,
F.; Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota,
A.; Sparks, W. B.
Bibcode: 1991fyho.conf..188C
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: High-Resolution
Observations of the Central Object R136 Of the 30 Doradus Nebula in
the LMC
Authors: Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Paresce, F.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.
Bibcode: 1991BAAS...23..828W
Altcode:
No abstract at ADS
Title: Foc/ Faint Object Camera Observations of R:136A in the
30-DORADUS Nebula
Authors: Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Paresce, F.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.
Bibcode: 1991fyho.conf..208W
Altcode:
No abstract at ADS
Title: Restoration of Images Degraded by Telescope Aberrations
Authors: Reinheimer, T.; Schertl, D.; Weigelt, G.
Bibcode: 1991fyho.conf..245R
Altcode:
No abstract at ADS
Title: A solar interferometric mission for ultrahigh resolution
imaging and spectroscopy: SIMURIS
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell, T.;
Foing, B. H.; Heyvaerts, J.; Lemaire, P.; Martić, M.; Muller, R.;
Porteneuve, J.; Roca Cortés, T.; Riehl, J.; Rutten, R.; Séchaud,
M.; Smith, P.; Thorne, A. P.; Title, A. M.; Vial, J. -C.; Visser,
H.; Weigelt, G.
Bibcode: 1991AdSpR..11a.383D
Altcode: 1991AdSpR..11..383D
SIMURIS is an interferometric investigation of the very fine structure
of the solar atmosphere from the photosphere to the corona. It was
proposed to ESA /1/, November 30 1989, for the Next Medium Size
Mission - M2, and accepted in February 1990 for an Assessment Study
in the context of the Space Station. The main scientific objectives
will be outlined, and the ambitious model payload featuring the Solar
Ultraviolet Network (SUN), a 2 m long monolithic array of 4 telescopes
of Ø20 cm, and the Imaging Fourier Transform Spectrometer (IFTS),
an UV and Visible Imaging Fourier Transform Spectrometer coupled to
a Ø40 cm Gregory, described.
Title: Solar physics at ultrahigh resolution from the space station
with the Solar Ultraviolet Network (SUN)
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell,
T.; Foing, B.; Heyvaerts, J.; Lemaire, P.; Martić, M.; Muller, R.;
Roca Cortés, T.; Riehl, J.; Rutten, R.; Title, A. M.; Vial, J. -C.;
Visser, H.; Weigelt, G.
Bibcode: 1991AdSpR..11e.267D
Altcode: 1991AdSpR..11..267D
The SUN experiment is a UV and visible Space Interferometer aimed at
ultra-high resolution in the solar atmosphere. It has been proposed
to ESA as part of the SIMURIS Mission Proposal which has recently
been accepted for an Assessment Study in the framework of the
Space Station. The 4 × 20 cm telescopes of the SUN linear array are
non-redundantly placed to cover a 2 m baseline, and the instrument makes
full use of stabilized interferometry potential, the 4 telescopes being
co-aligned and co-phased on a reference field on the sun. After a brief
outline of the scientific objectives, the concept of the instrument
is described, and its image reconstruction potential is illustrated.
Title: Deconvolution of Hubble Space Telescope Data: Computer
Simulations and Laboratory Experiments
Authors: Reinheimer, T.; Weigelt, G.
Bibcode: 1991rhis.conf...88R
Altcode:
No abstract at ADS
Title: The Very Massive Objects R136A in the 30 Doradus Nebula,
NGC 3603 and Eta Carinae: Cycle 1 Observations
Authors: Weigelt, Gerd
Bibcode: 1990hst..prop.3305W
Altcode:
R136a is the core of the ionizing cluster NGC 2070 at the center of
the 30 Doradus nebula in the Large Magellanic Cloud. The interesting
question is whether R136 is a supermassive object or whether it is a
dense star cluster. We propose FOC f/288 imaging and roll deconvolution
in order to solve the question. Roll deconvolution of FOC f/288 data
can yield exactly diffraction-limited resolution, for example, 0.02"
at lambda = 200 nm. The same observations are proposed in order to
study the nature HD 97950 AB in NGC 3603 and Eta Carinae. HD 97950
in NGC 3603 is probably of similar nature as R136. Objective prism
observations are proposed in order to perform speckle spectroscopy of
R136a and HD 97950 AB. Speckle interferometry observations (object
autocorrelations) show that all 3 objects can be resolved with the
ST. Only FOC f/288 measurements can yield the required resolution
since only in the case of f/288 data the pixel size is small enough.
Title: Image reconstruction from the bispectrum using an iterative
algorithm and applications of the method to astronomical objects
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1990SPIE.1351..522H
Altcode:
An algorithm is presented which facilitates the iterative reconstruction
of diffraction-limited images of astronomical objects with some
experimental results. A simulation of 300 1D speckle interferograms
of a star cluster is employed to demonstrate the reconstructed image
generated by the iterative algorithm after 800 steps. The results
are compared to an image reconstructed by means of the traditional
recursive method, and the iterative method is found to yield images
of higher quality.
Title: First Result from the Faint Object Camera: Images of the
Gravitational Lens System G2237 + 0305
Authors: Crane, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenburg, A.; Deharveng, J.; Disney, M. J.; Jakobsen, P.; Kamperman,
T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1990BAAS...22R1280C
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: Imaging the Core
of R Aquarii
Authors: Paresce, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksensburg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Macchetto, F.; Mackay, C. D.;
Weigelt, G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.;
Sparks, W. B.
Bibcode: 1990BAAS...22R1275P
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: Supernova 1987A
Authors: Jakobsen, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksenberg, A.; Crane, P.; Deharveng, J.; Disney, M. J.; Kamperman,
Y.; King, I. R.; Macchetto, F.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W.; Kirshner, R. P.; Panagia, N.
Bibcode: 1990BAAS...22.1275J
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: High Resolution
Imaging of the Pluto-Charon System
Authors: Albrecht, R.; Barbieri, C.; Baxter, D.; Blades, J. C.;
Boksensberg, A.; Crane, P.; Deharveng, J.; Disney, M. J.; Greenfield,
P.; Jakobsen, P.; Jedrzejewski, R.; Kamperman, T.; King, I. R.;
Macchetto, F.; Mackay, C. D.; Nota, A.; Paresce, F.; Sparks, W. B.;
Weigelt, G.
Bibcode: 1990BAAS...22.1279A
Altcode:
No abstract at ADS
Title: First Results from the Faint Object Camera: Observations
of PKS0521-36
Authors: Macchetto, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.;
Boksensburg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen,
P.; Kamperman, T. M.; King, I. R.; Mackay, C. D.; Paresce, F.; Weigelt,
G.; Baxter, D.; Greenfield, P.; Jedrzejewski, R.; Nota, A.; Sparks,
W. B.
Bibcode: 1990BAAS...22.1280M
Altcode:
No abstract at ADS
Title: A proposed medium-term strategy for optical interferometry
in space. Report to the ESA astronomy working group by the ESA Space
Interferometry Study Team (SIST).
Authors: Noordam, J. E.; Bely, P. Y.; Faucherre, M.; Greenaway, A. H.;
Merkle, F.; Perryman, M. A. C.; Roussel, P. H.; Vakili, F.; Volonté,
S.; Weigelt, G. P.
Bibcode: 1990pmso.book.....N
Altcode:
This report provides a summary of the scientific arguments leading
to the requirements for space interferometry, both in terms of its
astronomical objectives, and in view of the possibilities attainable
from the ground. It is shown that, at optical wavelengths, space
missions will be driven by the requirement to achieve diffraction
limited images beyond the magnitude limits achievable from the
ground. At ultraviolet and infrared wavelengths, similar considerations
naturally apply but, in addition, other fundamental physical atmospheric
properties enhance further the justification to go to space. It
is shown that several issues, albeit important to the efficiency
and applicability of both ground and space-based interferometry,
are not critical to the scientific case and technological issues
facing space interferometry. Amongst these topics are discussions of
image reconstruction techniques (speckle, phase closure, etc.), and
aperture distribution (redundant, non-redundant). Image restoration
techniques and other technical issues have made rapid advances in
the context of radio aperture synthesis and VLBI techniques, and,
in this field, optical interferometry will be well placed to exploit
these advances. There has also been considerable progress in methods,
theory and results of speckle imaging from the ground.
Title: A proposed medium-term strategy for optical interferometry
in space: Report to the ESA astronomy working group by the ESA Space
Interferometry Study Team (SIST)
Authors: Noordam, J. E.; Bely, P. Y.; Faucherre, M.; Greenaway, A. H.;
Merkle, F.; Perryman, M. A. C.; Roussel, P. H.; Vakili, F.; Volonte,
S.; Weigelt, G. P.
Bibcode: 1990pmts.rept.....N
Altcode:
The scientific arguments leading to the requirements for space
interferometry, both in terms of its astronomical objectives, and in
view of the possibilities attainable from the ground, are presented. It
is shown that, at optical wavelengths, space missions will be driven
by the requirement to achieve diffraction limited images beyond the
magnitude limits achievable from the ground. The Fizeau and Michelson
type interferometers are outlined. Above 15 to 20 m baselines, the
Michelson interferometer configuration emerges as a preferred candidate,
in particular in view of its less strict alignment tolerances. A system
level study is proposed to define the detailed design of a 100 m class
interferometer for launch around 2005.
Title: VLT interferometer: proposed implementation
Authors: Beckers, Jacques M.; Enard, Daniel; Faucherre, Michel; Merkle,
Fritz; di Benedetto, G. P.; Braun, R.; Foy, R.; Genzel, R.; Koechlin,
Laurent; Weigelt, Gerd
Bibcode: 1990SPIE.1236..108B
Altcode:
The Very Large Telescope Interferometer (VLTI) is one of the operating
modes of the VLT. In addition to consisting of the four stationary
8 m diameter telescopes, it includes a number of movable Auxiliary
Telescopes which both complement the (u, v) plane coverage of the large
telescopes and provide a powerful interferometric facility by itself
(available 100% of the time). The authors describe the current plans
for the implementation of the VLTI. These plans will be finalized
after the choice of the VLT site in 1990.
Title: Image reconstruction from the bispectrum using an iterative
algorithm and applications of the method to astronomical objects.
Authors: Hofmann, K. H.; Weigelt, G.
Bibcode: 1990SPIE.1319..444H
Altcode:
The atmosphere of the earth restricts the resolution of conventional
astrophotography to " 1 arcsec. Much higher resolution can be obtained
by interferometric speckle techniques. Bispectrum analysis'3 (also
called speckle masking) of many speckle interferograms (short-exposure
photographs; exposure time ,,o.o5 sec) yields diffraction-limited images
with, for example, 0.02 arcsec resolution for a 5-rn telescope. After
the first processing steps of speckle masking the object bispectrurn
o()(u,v) is obtained up to the cut-off frequency of the telescope. From
the object bispectrum a diffraction-limited image of the object can
be reconstructed (a) by using the conventional recursive method2 (the
Fourier phase of the object is extracted recursively from O()(u,v) )
or (b) by using an iterative image reconstruction algorithm presented
in this paper. The iterative algorithm searches for the high-resolution
image which has the best agreement with the measured object bispectrum.
Title: High Resolution Solar Physics from the Space Station with
Interferometric Techniques: The Solar Ultraviolet Network (SUN) -
Instrument &Objectives
Authors: Damé, L.; Acton, L.; Bruner, M.; Connes, P.; Cornwell, T.;
Foing, B.; Heyvaerts, J.; Jalin, R.; Lemaire, Ph.; Martic, M.; Moreau,
B.; Muller, R.; Roca Cortés, T.; Riehl, J.; Rutten, R.; Title, A. M.;
Vial, J. -C.; Visser, H.; Weigelt, G.
Bibcode: 1990PDHO....7..262D
Altcode: 1990dysu.conf..262D; 1990ESPM....6..262D
No abstract at ADS
Title: Speckle masking, speckle spectroscopy and optical aperture
synthesis
Authors: Weigelt, G.
Bibcode: 1990mtia.book..113W
Altcode:
No abstract at ADS
Title: Optics in complex systems. Proceedings.
Authors: Lanzl, F.; Preuss, H. -J.; Weigelt, G.
Bibcode: 1990SPIE.1319.....L
Altcode:
ICO-15 focuses on the present frontiers of optics. Optics today is
generally part of a larger system including mechanical, electrical,
and information-processing subsystems. The optimum design of the
overall system has to take into account aspects of all of these
subsystems. ICO-15 covers the fundamental limitations of optics and
emphasizes the system point of view.
Title: Objective prism speckle spectroscopy and wideband projection
speckle spectroscopy.
Authors: Grieger, F.; Weigelt, G.
Bibcode: 1990SPIE.1319..440G
Altcode:
The angular resolution of conventional astronomical spectroscopy
is limited to about 1 aresec by the turbulent atmosphere. Much
higher resolution can be obtained by (a) objective prism speckle
spectroscopy1, which yields diffraction-limited objective prism spectra,
and by (b) wideband projection speckle spectroscopy1, which yields
spectrally dispersed 1-dimensional projections of the object, i. e.,
object/spectrum reconstructions O(x,X) or O(x,y,X).
Title: Optical long-baseline interferometry in astronomy.
Authors: Reinheimer, T.; Weigelt, G.
Bibcode: 1990SPIE.1319..678R
Altcode:
Optical long-baseline interferometry can yield images and spectra
with fascinating angular resolution. For example, at a wavelength of
500 nm and with a baseline of lOOm a resolution of 10 arcsec can be
obtained. We have studied the dependence of the SNR in the reconstructed
image on the diluted pupil function, on wavefront aberrations and on
photon noise in the interferograms.
Title: HARDI: a high angular resolution deployable interferometer
for space
Authors: Bely, Pierre Y.; Burrows, Christopher; Roddier, Francois;
Weigelt, Gerd
Bibcode: 1989SPIE.1130...92B
Altcode:
The present orbiting interferometer proposal for operation in the
UV, visible, and near-IR spectral ranges employs a 6-m baseline and
a collecting area equivalent to an approximately 1.4-m diameter
aperture. The instrument, which is of Fizeau type and therefore
possesses better UV throughput than phased arrays, is projected
to be able to furnish resolutions superior to those of the Hubble
Space Telescope, as well as to complement prospective ground-based
interferometers with its greater limiting magnitude and spectral
coverage. A single launch will suffice to place the system in GEO or
sun-synchronous orbit, in order to minimize thermal and mechanical
disturbances and maximize observing efficiency.
Title: Aperture synthesis in space
Authors: Faucherre, Michel; Greenaway, Alan H.; Merkle, Fritz; Noordam,
Jan E.; Perryman, M. A.; Roussel, Philippe; Vakili, Farrokh; Volonte,
Serge; Weigelt, Gerd
Bibcode: 1989SPIE.1130..101F
Altcode:
The principles of optical aperture synthesis (OAS), which can yield
images of much higher resolution than current ground observations,
are essentially those of radio astronomy, and may be used in either
space- or ground-based studies of the stellar envelopes around Be
stars, the internal dynamics of active galaxies, etc. An account is
presently given of possible OAS instrument configurations; it is shown
that a large field of view can be achieved, so that the instrument
may be calibrated on bright stars during the observation of faint
sources. Mission concepts for a 'monostructure' OAS instrument of
about 30-m size are examined.
Title: Speckle imaging and speckle spectroscopy
Authors: Weigelt, Gerd
Bibcode: 1989SPIE.1130..148W
Altcode:
The 'bispectrum' or 'triple correlation processing' speckle-masking
method yields diffraction-limited images despite atmospheric image
degradation and telescope aberrations; the limiting magnitude
is approximately 18. An account is presently given of the theory
and applications of speckle masking. High-resolution images and
resolution-element spectra can be simultaneously obtained by objective
prism speckle spectroscopy and projection speckle spectroscopy
methods. The application of speckle masking to coherent arrays of
telescopes is noted to be able to yield, in the case of the 4 x 8 m
ESO Very Large Telescope, an angular resolution of 2.0 milliarcsec.
Title: Speckle Masking Observations of NGC1068 and NGC7469
Authors: Hofmann, K. H.; Mauder, W.; Weigelt, G.
Bibcode: 1989ESOC...32...35H
Altcode: 1989eag..work...35H
No abstract at ADS
Title: Profiles of a Key Programme: Gravitational Lensing
Authors: Surdej, J.; Arnaud, J.; Borgeest, U.; Djorgovski, S.;
Fleischmann, F.; Hammer, F.; Hutsemekers, D.; Kayser, R.; Le Fevre,
O.; Nottale, L.; Magain, P.; Meylan, G.; Refsdal, S.; Remy, M.;
Shaver, P.; Smette, A.; Swings, J. P.; Vanderriest, C.; van Drom,
E.; Véron-Cetty, M.; Véron, P.; Weigelt, G.
Bibcode: 1989Msngr..55....8S
Altcode: 1989Mgr....55....8S
Prior to Professor van der Laan's enquiry, in the March 1988 issue
of the Messenger, on the general interest among astronomers from the
European community to possibly participate in Key Programmes (KPs)
at the European 80uthern Observatory, at least three distinct groups
(including more than half of the above authors) were already involved
in the study of "gravitational lensing" effects (see box on pages
10-11). Observations were being performed with the help of various
telescopes on La 8illa as weil as at other observatories (VLA, CFHT,
Palomar, Kitt Peak, etc.).
Title: Speckle Masking, Speckle Spectroscopy, and Optical Aperture
Synthesis
Authors: Weigelt, G.
Bibcode: 1989ASIC..274..191W
Altcode: 1989dli..conf..191W
No abstract at ADS
Title: Speckle spectroscopy.
Authors: Grieger, F.; Fleischmann, F.; Weigelt, G.
Bibcode: 1989AGAb....2...30G
Altcode: 1989amt..conf...30G
No abstract at ADS
Title: Interferometric Imaging in Optical Astronomy
Authors: Weigelt, Gerd
Bibcode: 1989LNP...333..283W
Altcode: 1989egao.conf..283W
The atmosphere of the earth restricts the resolution of conventional
astronomical imaging to about 1. Much higher resolution can be obtained
by speckle methods. Speckle interferometry, the Knox-Thompson method
and the speckle masking method (bispectrum or triple correlation
processing) yield diffraction-limited resolution in spite of image
degradation by the atmosphere and telescope aberrations. For example,
with the ESO 3.6-m telescope a resolution of 0.028 is attained at
a wavelength of 400 nm. The limiting magnitude is about 18. We will
outline the theory behind the three methods. High-resolution images
and simultaneously the spectrum of each resolution element can be
obtained by the objective prism speckle spectroscopy and projection
speckle spectroscopy methods. Finally, we will discuss the application
of speckle masking to coherent arrays of telescopes. A very interesting
example is the 4x8-m ESO VLT, which should yield the fantastic angular
resolution of about 2 milli-arcsec.
Title: Speckle masking observations of NGC 3603, Eta Carinae, and
NGC 1068.
Authors: Eckert, J.; Hofmann, K. -H.; Mauder, W.; Schertl, D.; Weghorn,
H.; Weigelt, G.
Bibcode: 1989AGAb....2...31E
Altcode: 1989amt..conf...31E; 1989MitAG...2...31E
No abstract at ADS
Title: Speckle masking observation of eta Carinae.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1988A&A...203L..21H
Altcode:
The authors have performed speckle masking bispectrum observations
of η Carinae at λ ≡ 850 nm with the 2.2-m ESO/MPG telescope. The
reconstructed diffraction-limited image shows that η Carinae consists
of one dominant star and three fainter star-like objects at separations
of 0.21arcsec, 0.18arcsec, and 0.11arcsec. The three faint objects
are ≡12-times fainter than the dominant star. The diameter of all
four objects is <0.03arcsec.
Title: Speckle masking observations of the central object in NGC 3603,
Eta Carinae, and the Seyfert galaxies NGC 7469 and NGC 1068.
Authors: Baier, G.; Eckert, J.; Hofmann, K. -H.; Mauder, W.; Schertl,
D.; Weghorn, H.; Weigelt, G.
Bibcode: 1988Msngr..52...11B
Altcode: 1988Mgr....52...11B
Speckle masking bispectrum processing yields diffraction-limited
images in spite of image degradation by the atmosphere and by telescope
aberrations. For example, with the ESO 3.6-m telescope a resolution of
0:'028 can be obtained at λ - 400 nm. The limiting magnitude is - 18^m.
Title: Speckle masking.
Authors: Baier, G.; Eckert, J.; Hofmann, K. -H.; Mauder, W.; Schertl,
D.; Weghorn, H.; Weigelt, G.
Bibcode: 1988ESOC...29..151B
Altcode: 1988hrii.conf..151B
Speckle masking (bispectrum or triple correlation processing)
yields diffraction-limited images in spite of image degradation by
the atmosphere and by telescope aberrations. For example, with the
ESO 3.6-m telescope a resolution of 0.028arcsec can be obtained at λ
≡ 400 nm. The limiting magnitude is ≡18m. The authors
discuss various modifications of speckle masking and show applications
to the central object in NGC 3603, η Carinae, and the Seyfert galaxies
NGC 7469 and NGC 1068.
Title: Objective prism speckle spectroscopy and wideband projection
speckle spectroscopy.
Authors: Grieger, F.; Fleischmann, F.; Weigelt, G.
Bibcode: 1988ESOC...29..225G
Altcode: 1988hrii.conf..225G
The authors have investigated two different types of speckle
spectroscopy: (1) objective prism speckle spectroscopy, which yields
diffraction-limited objective prism spectra, and (2) wideband projection
speckle spectroscopy, which yields spectrally dispersed 1-dimensional
projections of the object, i.e., object/spectrum reconstructions O(x,λ)
or O(x,y,λ). The great advantage of the projection speckle spectroscopy
method is (1) that it can be applied to general objects and (2) that
O(x,λ) can be obtained for λ ≡ 350 nm to 900 nm simultaneously.
Title: An Entry Level Interferometer for Space
Authors: Bely, P. Y.; Burrows, C.; Roddier, F.; Weigelt, G.
Bibcode: 1988soae.conf....6B
Altcode:
No abstract at ADS
Title: Triple shearing interferometry and shearing spectroscopy.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1988ESOC...29..267H
Altcode: 1988hrii.conf..267H
No abstract at ADS
Title: Speckle masking with coherent arrays.
Authors: Reinheimer, T.; Fleischmann, F.; Grieger, F.; Weigelt, G.
Bibcode: 1988ESOC...29..581R
Altcode: 1988hrii.conf..581R
The authors show computer simulations of speckle masking with coherent
arrays of telescopes. High resolution images can be obtained by speckle
masking in spite of gaps in the optical transfer function. The authors
have investigated the dependence of the signal-to-noise ratio in the
reconstructed image on the number of photon events per interferogram and
on the pupil function (redundant, partially redundant and non-redundant
pupil functions). At the end of the paper the authors briefly describe
the present status of their 16-telescope interferometer.
Title: Optical parameters of the atmosphere.
Authors: Müller, M.; Baier, G.; Helm, S.; Weigelt, G.
Bibcode: 1988ESOC...29..553M
Altcode: 1988hrii.conf..553M
Various measurements of optical parameters of the atmosphere were
performed with the authors' speckle camera mounted at the 2.2-m ESO/MPG
telescope. The advantage of speckle interferograms is the fact that many
different atmospheric parameters can be derived from them: for example,
seeing angle, intensity profile of long-exposure images, image motion,
speckle life time, isoplanicity, etc. Since the authors have performed
a large number of measurements of each parameter, correlations between
these parameters and with meteorological conditions (e.g., humidity,
pressure, wind speed and jet streams) can be studied.
Title: Aperture Synthesis in Space - Overview and Results from the
ESA Study Group
Authors: Faucherre, M.; Greenaway, A. H.; Merkle, F.; Noordam, J. E.;
Perryman, M. A. C.; Roussel, P.; Vakili, F.; Volonte, S.; Weigelt,
G. P.
Bibcode: 1988dli..conf..389F
Altcode:
No abstract at ADS
Title: Speckle Masking Speckle Spectroscopy and Optical Aperture
Synthesis
Authors: Weigelt, G.
Bibcode: 1988dli..conf..191W
Altcode:
No abstract at ADS
Title: ISIS: Image reconstruction experiments and comparison of
various array configurations
Authors: Reinheimer, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1987ESASP.273...41R
Altcode: 1987ois..work...41R
The application of speckle masking (triple correlation processing)
to coherent, telescope arrays in space is introduced. True
diffraction-limited images are obtained since speckle masking is
the solution of the phase problem in speckle interferometry. For
example, a 14 m array can yield a resolution of 0.004 arcsec at 200 nm
wavelength. Resolution of 0.000001 arcsec can be obtained with a 40 km
array at 200nm. Computer simulations of optical aperture synthesis by
speckle masking are shown. Simulations of a two-dimensional ring-shaped
array and of a linear one-dimensional array are described. The
dependence of the signal-to-noise ratio in the reconstructed image on
photon noise is discussed.
Title: ISIS: imaging speckle interferometer in space
Authors: Weigelt, Gerd
Bibcode: 1987ESASP.273...69W
Altcode: 1987ois..work...69W
The author proposes the construction of a large multiple-mirror
interferometer in space. For example, at λ ≡ 100 nm and with a
baseline of 20 m, a resolution of 0arcsec.001 can be obtained. The
following three interferometer types are very attractive: (a)
linear 14-m array (launched by the Space Shuttle), (b) 2-dimensional,
deployable 20 m array, and (c) array of 6 to 20 free-flying telescopes
with baselines up to 40 km and resolution of 10-6arcsec
at λ ≡ 200 nm. The limiting magnitude of optical long-baseline
interferometry in space is ≡24m or even fainter.
Title: ISIS: image reconstruction methods and signal-to-noise ratio
investigations
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1987ESASP.273...37H
Altcode:
In this paper the signal-to-noise ratio of the two image reconstruction
methods optical phase-closure imaging and speckle masking (triple
correlation) are discussed. The results show that (1) phase-closure
imaging yields images with higher signal-to-noise ratio than speckle
masking for bright objects and that (2) speckle masking yields images
with higher signal-to-noise ratio than phase-closure imaging for
faint objects.
Title: Astronomical speckle masking: image reconstruction by cross
triple correlation
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1987ApOpt..26.2011H
Altcode:
A new, modified version of speckle masking that is based on cross
triple correlation processing (or cross bispectrum processing) instead
of autotriple correlation processing is proposed. The advantage of
cross triple correlation processing is the fact that undesired photon
bias terms in the average bispectrum of the speckle interferograms
are overcome completely. Computer simulations (astronomical magnitude
about 16 mag) that illustrate the feasibility of the method are shown.
Title: Optical long-baseline interferometry and aperture synthesis
by speckle masking
Authors: Reinheimer, T.; Weigelt, G.
Bibcode: 1987A&A...176L..17R
Altcode:
The application of speckle masking to coherent telescope arrays
can yield images with very high angular resolution. True images are
obtained since speckle masking is a solution of the phase problem in
speckle interferometry. For example, a 1-km array on earth can yield
a resolution of 10-4arcsec at λ ≡ 500 nm. The fantastic
resolution of 10-6arcsec can be obtained with a 40-km array
in space at λ ≡ 200 nm. The authors show computer simulations of
optical aperture synthesis by speckle masking. They describe simulations
with a 10-telescope and a 4-telescope array (ESO VLT). Photon noise
in the interferograms was simulated in all experiments.
Title: High-resolution astronomical imaging by roll deconvolution
of Space Telescope data
Authors: Mueller, M.; Weigelt, G.
Bibcode: 1987A&A...175..312M
Altcode:
Summary. Roll deconvolution is a speckle method that can improve
the resolution of the 2.4-m Hubble Space Telescope (H ST) at
short UV wavelengths. A diffraction-limited image can be digitally
reconstructed from two aberration-degraded images recorded at two
different roll angles of the HST. The reconstruction is performed
by complex inverse filtering of the two degraded images. We show
optical-digital simulations that illustrate how the signal-to-noise
ratio of the reconstruction depends on photon noise, on the structure
of the point-spread function and on other parameters. The roll
deconvolution technique can be applied to HST data recorded with the
f/288- mode of the Faint Object Camera. At = 140 nm a resolution of
0015 can be obtained. Key words: space vehicles - image processing -
instruments - interferometry - spectroscopy
Title: Speckle interferometric observations of Pluto and its moon
Charon on seven different nights
Authors: Baier, G.; Weigelt, G.
Bibcode: 1987A&A...174..295B
Altcode:
We have performed speckle interferometric observations of Pluto and
its moon Charon on seven different nights. The measured separations
varied from 0".20 to 0".86. The speckle data were recorded with the
2.2-m telescope at the Calar Alto Observatory in Spain. For these
measurements 87000 speckle interferograms were reduced digitally. The
resolution of the observations is 0".07. The data from July 12 were
used to study the size of Pluto and Charon.
Title: Speckle masking - Overcoming atmospheric image degradation
in optical astronomy
Authors: Weigelt, G.
Bibcode: 1987KlBer..30...15W
Altcode:
The fundamental principles and performance of the optical speckle
masking technique developed by Weigelt (1977) and Weigelt and Wirnitzer
(1983) are briefly characterized. The method makes it possible to
obtain astronomical images with diffraction-limited resolution down
to a limiting magnitude of about 20 mag. The resolution possible with
speckle masking is found to be about 30 marcsec for a 3.6-m telescope,
100 microarcsec for a 1-km-baseline ground interferometric array,
and 1 microarcsec (at wavelength 200 nm) for a 40-km-baseline space
array. Sample images, computer simulations of aperture synthesis,
and a model of a space array are shown.
Title: Triple Shearing Interferometry and Shearing Spectroscopy
Authors: Hofmann, K. H.; Weigelt, G.
Bibcode: 1987iia..conf...83H
Altcode:
No abstract at ADS
Title: Image Reconstruction from Long Baseline Interferograms by
Speckle Masking
Authors: Hofmann, K. H.; Reinheimer, T.; Weigelt, G.
Bibcode: 1987iia..conf..157H
Altcode:
No abstract at ADS
Title: High-resolution astronomical imaging by triple correlation
processing.
Authors: Weigelt, G.
Bibcode: 1987SPIE..828....8W
Altcode:
The atmosphere of the earth restricts the resolution of conventional
astrophotography to about 1 arcsec. Much higher resolution can be
obtained by using speckle methods. The speckle masking method (triple
correlation method) yields images of general astronomical objects with
diffraction-limited resolution, for example, 0.03 arcsec resolution
for a 3.6-m telescope. A 1-km telescope array on the earth would yield
images with 10-4arcsec resolution. With a 40-km array in
space a fantastic resolution of 10-6arcsec can be achieved at
λ ≡200 nm. The author shows speckle masking observations of NGC 3603
and Eta Carinae and computer simulations of optical aperture synthesis.
Title: Hochauflösende Abbildungsmethoden bei UV-, sichtbaren und
IR-Wellenlängen
Authors: Weigelt, G.
Bibcode: 1987MitAG..68..157W
Altcode:
No abstract at ADS
Title: Erfordernisse und Möglichkeiten räumlicher Auflösung
Authors: Weigelt, G.
Bibcode: 1987MitAG..68..141W
Altcode:
No abstract at ADS
Title: High-resolution astronomical imaging by photon-counting
speckle masking.
Authors: Schertl, D.; Fleischmann, F.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1987SPIE..808...38S
Altcode:
Speckle masking is a triple correlation method that can reconstruct
diffraction-limited images from astronomical speckle interferograms. The
obtained resolution is about 30 times higher than the resolution of
conventional astronomical photography. In this paper we describe
a photon-counting version of speckle masking that can be applied
to speckle interferograms consisting of a small number of photon
events. We show computer simulations which illustrate the feasibility
of the method. Finally, we compare photon-counting speckle masking with
four-dimensional bispectrum processing, tomographic speckle masking,
cross-triple correlation processing and bispectrum processing of
photon-counting speckle interferograms.
Title: Speckle Masking and Speckle Spectroscopy
Authors: Weigelt, G.; Hofman, K. H.
Bibcode: 1987iia..conf...43W
Altcode:
No abstract at ADS
Title: Image reconstruction from long-baseline interferograms.
Authors: Reinheimer, T.; Hofmann, K. -H.; Weigelt, G.
Bibcode: 1987SPIE..808...35R
Altcode:
During the last few years it has been shown that speckle
masking observations with large single-dish telescopes can yield
diffraction-limited images in spite of image degradation by the
atmosphere and by telescope aberrations. Much higher resolution
can be obtained if the Coude beams of many telescopes are combined
coherently in a central station and if the obtained long-baseline
speckle interferograms are evaluated by speckle masking. For example,
a 10-km array on earth can yield images with the fascinating resolution
of 10 arcsec. Labeyrie has for the first time shown that it is possible
to combine the Coude beams of two telescopes coherently.
Title: High angular resolution shearing spectroscopy and triple
shearing interferometry
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1986ApOpt..25.4280H
Altcode:
Shearing spectroscopy is a new method which can simultaneously yield
high spatial and spectral resolution in spite of telescope aberrations
and image degradation caused by the atmosphere. Especially attractive
is the application of shearing spectroscopy to large astronomical space
telescopes. The method is an extension of shearing interferometry. The
principle of shearing spectroscopy and laboratory experiments are
described. Two different methods have been studied for reconstructing
true images and objective prism spectra from shearing data: holographic
shearing interferometry, and a new method called triple shearing
interferometry. Triple shearing interferometry is in some respects
related to the phase closure method in radio interferometry.
Title: Imaging speckle interferometer in space: image reconstruction
by speckle masking.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1986JOSAA...3.1908H
Altcode: 1986OSAJ....3.1908H; 1986JOSAA...3.1908W
The authors propose the construction of a large multiple-mirror
interferometer in space. For example, at λ ≡ 100 nm and with a
baseline of 20 m, a resolution of 0.001 sec of arc can be obtained. At
short UV wavelengths a multiple-mirror interferometer will produce
speckle interferograms caused by aberrations and deformations
of the interferometer. From the speckle interferograms true
diffraction-limited images can be reconstructed by various speckle
methods. The speckle-masking method (triple correlation) is attractive
since it yields true images with high signal-to-noise ratio. The
limiting magnitude of interferometry in space is about 24.
Title: Speckle masking observation of the central object in the
giant H II region NGC 3603.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1986A&A...167L..15H
Altcode:
The authors report the first reconstruction of a true
diffraction-limited image of the central object HD 97950 AB in NGC
3603. The image has been reconstructed by a 4-dimensional version
of speckle masking (triple correlation processing). Speckle masking
is a solution of the phase problem in speckle interferometry. The
reconstructed image shows that HD 97950 AB consists of 4 stars
(V-magnitudes 11.7, 11.7, 11.7 and 12.2; separations relative to A1:
0.78arcsec, 0.37arcsec and 0.34arcsec).
Title: R 136 a et l'objet central de la région H II géante NGC
3603 résolu par interférometrie holographique des tavelures.
Authors: Weigelt, G.; Baier, G.; Ladebeck, R.
Bibcode: 1986LAstr.100..346W
Altcode:
No abstract at ADS
Title: Eta Carinae resolved by speckle interferometry.
Authors: Weigelt, G.; Ebersberger, J.
Bibcode: 1986A&A...163L...5W
Altcode:
The authors have performed digital speckle interferometric observations
of Eta Carinae at λ ≡ 820 nm and λ ≡ 850 nm with the 3.6-m and
2.2-m telescope at ESO. Four starlike components (stars or gas clouds)
were resolved for the first time. The diameter of all 4 components is
<0arcsec.03. The field size of the reconstructed autocorrelation is
≡0arcsec.8. The separations of the components A2, A3 and A4 relative
to the brightest component A1 are 0arcsec.18, 0arcsec.22 and 0arcsec.09,
respectively.
Title: High resolution speckle methods for overcoming image
degradation caused by the atmosphere and telescope aberrations.
Authors: Weigelt, G.; Baier, G.; Ebersberger, J.; Fleischmann, F.;
Hofmann, K. -H.; Ladebeck, R.
Bibcode: 1986OptEn..25..706W
Altcode:
Analytical techniques are described for using speckle interferometry
(SI) obtain 0.03 arcsec resolution images of stellar objects. SI
proceeds by computing the ensemble average power spectrum of all
speckle interferograms, compensating for the photon bias in the
spectrum and for the SI transfer function, and calculating the object
autocorrelations from the object power spectrum. Techniques employed for
holographic SI, speckle masking to obtain diffraction-limited images,
and speckle spectroscopy are defined. Photon-counting techniques
and autocorrelations and image reconstruction from long-baseline and
multiple-mirror interferometry are also defined. Sample SI images are
provided of numerous stellar objects, including the asteroids Juno and
Amphitrite, Pluto and is moon Charon, spectroscopic and Hyades double
stars, and the gravitational lens quasar PG 1115+080A.
Title: Speckle interferometry of spectroscopic and Hyades binary
stars.
Authors: Ebersberger, J.; Weigelt, G.; Orellana, R. B.
Bibcode: 1986A&AS...64..131E
Altcode:
We report on 39 high-resolution speckle observations of 18
spectroscopic, 9 Hyades and 7 other binary stars. Measurements were
performed with the Danish 1.5-m and the ESO 3.6-m telescope at La
Silla, Chile.
Title: Optical parameters of the atmosphere and high-resolution
long-exposure imaging.
Authors: Weigelt, G.; Baier, G.; Helm, S.; Mueller, M.; Wurm, C.
Bibcode: 1986ESOC...24..215W
Altcode: 1986vlt..work..215W
The investigation of optical parameters of the atmosphere is
important for site selection for future large telescopes. From speckle
interferograms many different parameters can be derived. The authors
have studied the following optical parameters for many different nights:
(1) long-exposure point-spread function, (2) image motion of speckle
interferograms (short-exposure images), (3) temporal variation of
the size (FWHM) of speckle interferograms, (4) differential image
motion between the two Airy disks of two 5-cm apertures at a distance
of 30 cm (and calibration measurements for the ESO seeing monitor),
(5) speckle life time, (6) isoplanicity of speckle interferograms
(space variance of speckle interferograms).
Title: Image Reconstruction from Speckle Interferograms Recorded
with a Laboratory Segmented-Mirror Telescope
Authors: Hofmann, K. -H.; Koch, R.; Weigelt, G.
Bibcode: 1986MitAG..67..430H
Altcode:
No abstract at ADS
Title: Speckle masking, speckle spectroscopy and optical aperture
synthesis.
Authors: Weigelt, G.; Hofmann, K. -H.; Reinheimer, T.
Bibcode: 1986ESOC...24..289W
Altcode: 1986vlt..work..289W
Speckle masking is a solution of the phase problem in speckle
interferometry. Therefore, diffraction-limited images can be
reconstructed by speckle masking in spite of image degradation by the
atmosphere and telescope aberrations. Speckle masking observations
with one of the 8-m telscopes of the ESO-VLT can yield high-resolution
images with 0.01arcsec resolution. The limiting magnitude of speckle
interferometry and of speckle masking is about 20m. Speckle
spectroscopy is a speckle method that yields diffraction-limited
objective prism spectra. The coherent combination of the 4 beams of
the 4 VLT telescopes yields long-baseline speckle interferograms. The
authors show by digital simulation that images with 0.001arcsec
resolution can be reconstructed from VLT long-baseline interferograms by
speckle masking. They compare the 25 m-25 m-25 m redundant array with
the 25 m-75 m-50 m nonredundant array. The 25 m-25 m-25 m redundant
array yields much higher SNR.
Title: Speckle Interferometry of T Tauri Stars and Related Objects
Authors: Baier, G.; Bastian, U.; Keller, E.; Mundt, R.; Weigelt, G.
Bibcode: 1985A&A...153..278B
Altcode:
The authors have performed speckle interferometric observations of
5 T Tauri stars and 3 related objects. The main motivation for this
work is to measure known close double stars and to search for new close
double stars which can be used for mass determinations. The authors have
resolved the known double stars V649 Ori (separation = 1arcsec.41) and
S CrA (separation = 1arcsec.37). The measurements of the stars CO Ori,
UX Tau A, DQ Tau, HR 6000, HR 5999, and TY CrA show that these stars
cannot be double stars with a separation larger than 0arcsec.09 and a
magnitude difference smaller than 2 - 3m. Furthermore the
angular diameter of the stars is smaller than 0arcsec.09.
Title: Speckle interferometry of the central object in the giant
HII region NGC 3603.
Authors: Baier, G.; Ladebeck, R.; Weigelt, G.
Bibcode: 1985A&A...151...61B
Altcode:
The central object of the giant H II region NGC 3603 is the dense
star cluster HD 97950. In various papers it has been discussed that
this object may be of similar nature as the luminous central object R
136a of the 30 Doradus nebula in the Large Magellanic Cloud. Speckle
interferometric observations of the dominating core AB of HD 97950
have been performed. It is found that HD 97950AB consists of at least
four stars. The component B is a single star at a resolution of 0.09
arcsec. The component A is a close triple star. The separations of A2,
A3 and B relative to A1 were measured to be 0.366 arcsec, 0.332 arcsec,
and 0.779 arcsec, respectively. The autocorrelation of AB contains a
true, diffraction-limited image of the triple star A1-A2-A3.
Title: R 136a in the 30 Doradus nebula resolved by holographic
speckle interferometry.
Authors: Weigelt, G.; Baier, G.
Bibcode: 1985A&A...150L..18W
Altcode:
The authors have performed digital speckle interferometry observations
of R 136, the luminous central object in the 30 Doradus nebula. It was
possible to reconstruct a diffraction-limited true image of R 136a by
using R 136b and R 136c as the deconvolution keys (holographic speckle
interferometry). The reconstructed image shows for the first time that
R 136a is a dense star cluster consisting of 8 stars within a diameter
of 1arcsec (at λ ≡ 710 nm). The dominating objects are three stars
of almost identical magnitudes with separations of 0.10arcsec and
0.48arcsec. The reconstructed image has a resolution of 0.09arcsec.
Title: R 136a and the central object in the giant H II region NGC
3603 resolved by holographic speckle interferometry.
Authors: Weigelt, G.; Baier, G.; Ladebeck, R.
Bibcode: 1985Msngr..40....4W
Altcode:
No abstract at ADS
Title: Imaging Speckle Interferometer (ISI) in space: digital
simulations ofimage reconstruction and photon noise.
Authors: Hofmann, K. H.; Weigelt, G.
Bibcode: 1985ESASP.226..145H
Altcode: 1985koas.coll..145H
Image reconstruction for the Imaging Speckle Interferometer (ISI)
a space-based multiple mirror interferometer which can produce
high-resolution images is discussed. At short UV wavelengths a multiple
mirror interferometer produces speckle interferograms caused by
aberrations of the interferometer. From the speckle interferograms true
images can easily be reconstructed with the speckle masking method. In
speckle masking no point source is required near the object. Digital
simulations of image reconstruction from ISI data, in which various
multiple mirror pupil functions and various amounts of photon noise
(1000 to 10 photons per pixel) were simulated are shown. Speckle
spectroscopy with ISI, and image reconstruction from 2-telescope
interferograms are considered.
Title: TRIO: a kilometric array stabilized by solar sails.
Authors: Labeyrie, A.; Authier, B.; de Graauw, T.; Kibblewhite, E.;
Weigelt, G.
Bibcode: 1985ESASP.226...27L
Altcode: 1985koas.coll...27L
A spaceborne optical array (TRIO) consisting of 2 to 4 telescopes
spaced up to 1000 m apart, at Lagrange point 5 of the Earth-Moon
trajectory is described. For kilometric baselines and variable
aperture patterns allowing image reconstructions, TRIO has free flying
telescopes and a focal station. Small solar sails point and stabilize
the system. Electrostatic mounts support the telescopes. Many apertures
can be utilized in later versions.
Title: Speckle interferometry, image reconstruction by speckle
masking, speckle spectroscopy, multiple-mirror interferometry.
Authors: Weigelt, G.; Baier, G.; Ebersberger, J.; Fleischmann, F.;
Hofmann, K. -H.; Ladebeck, R.
Bibcode: 1985SPIE..556..238W
Altcode:
The authors discuss various high-resolution speckle methods which can
overcome image degradation caused by the atmosphere and telescope
aberrations. All methods yield diffraction-limited resolution, for
example 0.03arcsec for a 3.6 m telescope. The authors show various
astronomical applications of speckle interferometry, observations of
asteroids, Pluto/Charon, double stars and the gravitational-lens triple
quasar. Speckle interferometry can yield a true diffraction-limited
image if there is a point source (reference star) in the isoplanatic
neighbourhood of the object (holographic speckle interferometry). The
authors show an application of holographic speckle interferometry
to the central object R136a of the 30 Doradus nebula in the Large
Magellanic Cloud. A true diffraction-limited image of R136a has been
reconstructed. The image shows that R136a consists of 8 stars. Speckle
masking is a triple correlation method which yields diffraction-limited
images of general astronomical objects. A point source near the
object is not required. The authors describe an application of speckle
masking to the central object in the giant H II region NGC 3603. The
reconstructed image shows that this central object is a star cluster of
4 stars with magnitudes 11m, 12m, 13m
and 13m.
Title: Roll deconvolution of Space Telescope data: inverse filtering
of two speckle interferograms.
Authors: Müller, M.; Weigelt, G.
Bibcode: 1985SPIE..556..270M
Altcode:
Roll deconvolution is a speckle method that can improve the resolution
of the 2.4 m Hubble Space Telescope (HST) at short UV wavelengths. A
diffraction-limited image can digitally be reconstructed from two
degraded images recorded at two different roll angles of the HST. The
reconstruction is performed by complex inverse filtering of the two
degraded images. In digital simulations the authors have investigated
how the signal-to-noise ratio of the reconstruction depends on photon
noise (104 to 50 photon counts per pixel), on the structure
and size of the point spread function (caused by aberrations) and
other parameters.
Title: Isoplanicity and lifetime of stellar speckle interferograms.
Authors: Ebersberger, J.; Weigelt, G.
Bibcode: 1985AcOpt..32..793E
Altcode:
No abstract at ADS
Title: Roll deconvolution of space telescope data
Authors: Walter, M.; Weigelt, G.
Bibcode: 1985AdSpR...5c.169W
Altcode: 1985AdSpR...5..169W
Roll deconvolution is a speckle method that can improve the resolution
of the 2.4m Space Telescope at short UV wavelengths. In digital
simulations we have investigated the dependence of the signal-to-noise
ratio of the reconstruction on photon noise (104 to
10 photons per pixel), the object size, the telescope point spread
function and guiding errors.
Title: PM. 08 Trio: A Kilometric Optical Array Controlled by Solar
Sails
Authors: Labeyrie, A.; Authier, B.; Boit, J. L.; de Graauw, T.;
Kibblewhite, E.; Koechlin, L.; Rabout, P.; Weigelt, G.
Bibcode: 1984BAAS...16..828L
Altcode:
Concepts studied for ESA's TRIO project are presented: system control
in the vicinity of the L5 Lagrangian point, pointing and alignment
procedures, sky coverage optical train, image reconstruction through
aperture synthesis, scattered light contamination of the coudé beams,
algorithms for stabilizing drifting fringes in computer memory,
limiting magnitudes.
Title: Interferometría estelar Speckle aplicada a la determinación
de dobles espectroscópicas
Authors: Orellana, R. B.; Weigelt, G.
Bibcode: 1984BAAA...30..186O
Altcode:
La técnica de Interferometría Speckle permite, a través de
métodos del análisis de Fourier, obtener imágenes estelares con una
resolución próxima al límite por difracción del telescopio, a partir
de imágenes registradas con determinado grado de degradación. Se
discuten dos técnicas de análisis, una analógica (óptica)
y la otra digital, efectuando una comparación de ambas en base
a la resolución final alcanzada para la separación y ángulo de
posición. Se discute la flexibilidad y la velocidad de procesamiento
en ambos casos. Se presentan resultados experimentales de unas diez
dobles espectroscópicas, habiéndose obtenido una resolución para
la separación de 0".03. Todos los registros fueron obtenidos con el
telescopio de 3.6 m del ESO (Chile).
Title: Specle Interferometrie von T Tauri-Sternen und verwandten
Objekten
Authors: Baier, G.; Keller, E.; Weigelt, G.; Bastian, U.; Mundt, R.
Bibcode: 1984MitAG..62..241B
Altcode:
No abstract at ADS
Title: Photon-counting speckle interferometry of Pluto's moon Charon
in 5 different nights.
Authors: Baier, G.; Weigelt, G.
Bibcode: 1984anop.conf...36B
Altcode:
No abstract at ADS
Title: Speckle interferometry, speckle masking, speckle spectroscopy
and speckle frame selection
Authors: Weigelt, G.
Bibcode: 1984vlti.conf..337W
Altcode: 1984IAUCo..79..337W
High-resolution speckle imaging which is made possible by a very large
telescope (VLT) is discussed. It is shown that various speckle methods
can yield a resolution of about 0.01 arcsec with a 8-m to 10-m VLT and
that the usefulness of the methods depends on the achievable limiting
magnitude. The seeing-dependent limiting magnitudes that are possible
with speckle interferometry, speckle masking, and speckle spectroscopy
are considered. Speckle interferometry results of faint objects,
R136a, Pluto/Charon, and the gravitational-lens quasar PG1115 + 080 A,
as well as speckle masking measurements of some close spectroscopic
double stars are presented.
Title: A skeletonizing photon-counting technique for stellar speckle
interferometry; application to speckle data of a gravitational
lens quasar.
Authors: Baier, G.; Weigelt, G.
Bibcode: 1984anop.conf...34B
Altcode:
No abstract at ADS
Title: Roll deconvolution of Space Telescope data; investigation of
the influence of photon noise.
Authors: Walter, M.; Weigelt, G.
Bibcode: 1984anop.conf...40W
Altcode:
No abstract at ADS
Title: Speckle spectroscopy.
Authors: Stork, W.; Weigelt, G.
Bibcode: 1984anop.conf...32S
Altcode:
No abstract at ADS
Title: Triple correlation theory and applications of the
speckle-masking method.
Authors: Lohmann, A. W.; Weigelt, G.; Wirnitzer, B.
Bibcode: 1984anop.conf...28L
Altcode:
No abstract at ADS
Title: New site testing techniques.
Authors: Ebersberger, J.; Weigelt, G.
Bibcode: 1984ESOC...18..185E
Altcode: 1984stfl.work..185E
The derivation of desired atmospheric parameters from speckle
interferograms is discussed, and measurements of long-exposure point
spread functions, speckle life time and other atmospheric parameters
are illustrated. The most important atmospheric parameters for site
testing are the long-exposure point spread function, the speckle
life time, and the distribution of the atmospheric layers. Other
important parameters include the size of the isoplanatic field and
the average power spectrum of speckle interferograms and shearing
interferograms. Two different types of telescopes are useful for
site testing measurements. A 0.3 m site testing telescope produces
scintillation measurements and image motion measurements, and a 0.7 m
or 1.2 m site testing telescope produces speckle interferograms. More
information can be extracted from speckle interferograms than from
image motion data, and measurements of image motion, size and shape
of the long-exposure point spread function, the speckle life time,
isoplanicity, and the average power spectrum of speckle interferograms
can be obtained. Pupil images recorded with a 0.7 m or 1.2 m telescope
can provide the distribution of atmospheric layers. The recording and
evaluation of speckle data in addition to the classical site testing
data is suggested.
Title: Derivation of atmospheric parameters from speckle
interferograms.
Authors: Ebersberger, J.; Weigelt, G.
Bibcode: 1984anop.conf...44E
Altcode:
No abstract at ADS
Title: Photon-counting speckle interferometry of T Tauri stars.
Authors: Baier, G.; Bastian, U.; Keller, E.; Mundt, R.; Weigelt, G.
Bibcode: 1984anop.conf...38B
Altcode:
No abstract at ADS
Title: Shearing spectroscopy.
Authors: Hofmann, K. -H.; Weigelt, G.
Bibcode: 1984anop.conf...42H
Altcode:
No abstract at ADS
Title: High-resolution astronomical imaging with the speckle masking
method.
Authors: Stork, W.; Weigelt, G.; Wirnitzer, B.
Bibcode: 1984anop.conf...26S
Altcode:
No abstract at ADS
Title: Speckle masking in astronomy: triple correlation theory and
applications.
Authors: Lohmann, A. W.; Weigelt, G.; Wirnitzer, B.
Bibcode: 1983ApOpt..22.4028L
Altcode:
Due to the turbulent atmosphere the resolution of conventional
astrophotography is limited to ≡1 sec of arc. However, the
speckle-masking method can yield diffraction-limited resolution, i.e.,
0.03 sec of arc with a 3.6-m telescope. Speckle masking yields true
images of general astronomical objects. No point source is required in
the isoplanatic field of the object. The authors present the theory of
speckle masking; it makes use of triple correlations and their Fourier
counterparts, the bispectra. They show algorithms for the recovery of
the object from genuine astronomical bispectra data.
Title: Speckle interferometry observations of Pluto's moon Charon
Authors: Hetterich, N.; Weigelt, G.
Bibcode: 1983A&A...125..246H
Altcode:
A photon-counting speckle interferometric study of Pluto and its
moon, Charon, has used 12,000 speckle interferograms to yield position
angles. In order to solve such measurements' inherent 180-deg ambiguity,
a long exposure photograph of the speckle data on the second night of
observation was calculated. Due to the motion of Charon, the position
angle changed from 188 to 170 deg, while the separation changed from
0.63 to 0.95 arcsec.
Title: Image reconstruction by the speckle-masking method.
Authors: Weigelt, G.; Wirnitzer, B.
Bibcode: 1983OptL....8..389W
Altcode:
Speckle masking is a method for reconstructing high-resolution images
of general astronomical objects from stellar speckle interferograms. In
speckle masking no unresolvable star is required within the isoplanatic
patch of the object. The authors present digital applications of
speckle masking to close spectroscopic double stars. The speckle
interferograms were recorded with the European Southern Observatory's
3.6-m telescope. Diffraction-limited resolution (0.03 arcsec) was
achieved, which is about 30 times higher than the resolution of
conventional astrophotography.
Title: Speckle Site Testing
Authors: Weigelt, G.
Bibcode: 1983ESOC...17..263W
Altcode: 1983vlt..work..263W
The author suggests to perform site testing for the Very Large
Telescope (VLT) with two or three transportable, light weight 1.2 m
telescopes. These telescopes should record speckle interferograms and
pupil images. From these raw data most of the interesting atmospheric
parameters can be derived easily.
Title: High-resolution imaging with ESO's Very Large Telescope
Authors: Weigelt, G.
Bibcode: 1983ESOC...17..121W
Altcode: 1983vlt..work..121W
High resolution speckle interferometry, speckle masking and speckle
spectroscopy with the European Southern Observatory's planned Very
Large Telescope (VLT) are discussed. These methods are noted to yield
exactly diffraction-limited resolution, lambda/D; so that 0.01-arcsec
resolution is obtainable in the case of an aperture diameter, D, of 10
m, and 0.0005 arcsec resolution is achievable in the case of an array
with a baseline, D, of 200 m. Limiting magnitude, seeing dependence,
influence of aberration, and influence of dome seeing, are illustrated
for various high resolution measurements. The suggested construction
of a three-telescope array has the advantage of additional use for
long baseline speckle work, as well as three-telescope intensity
interferometry.
Title: Speckle interferometry observations of the asteroids Juno
and Amphitrite
Authors: Baier, G.; Weigelt, G.
Bibcode: 1983A&A...121..137B
Altcode:
Digital speckle interferometry of the asteroids Juno and Amphitrite has
been performed. The speckle interferograms were recorded with the Danish
1.5 m telescope at the European Southern Observatory. The measurements
show that both asteroids have elliptical shapes. The diameters of Juno
were measured to be 230 km + or - 20 km (0.26 arcsec), and 288 km +
or - 20 km (0.32 arcsec) on December 24, 1979, at 6 h 10 min UT, and
the diameters of Amphitrite were 160 km + or - 30 km (0.11 arcsec) and
255 km + or - 30 km (0.17 arcsec) on April 4, 1981, at 8 h 30 min UT.
Title: Digital speckle interferometry of Juno, Amphitrite and Pluto's
moon Charon
Authors: Baier, G.; Hetterich, N.; Weigelt, G.
Bibcode: 1982Msngr..30...23B
Altcode:
Digital speckle interferometric observations of the 9th and 11th
magnitude asteroids Juno and Amphitrite and of the 16th magnitude
moon of Pluto, Charon, are reported. Results are also reported for
the 11th magnitude Seyfert galaxy NGC 1068, the 12.7th magnitude
quasar 3 C 273, and the 16.2 magnitude triple QSO PG 1115+080. The
observational technique consists of Fourier analyses of large numbers
of short-exposure photographs, i.e., speckle interferograms, to produce
high resolution autocorrelated imagery. Short exposures are used to
retain high resolution features. Image intensifiers with a gain of
300,000 were part of the equipment, together with a photon-counting
mode capability. A total of 1450 speckle interferograms were produced
for Juno, 1776 for Amphitrite, and 15,000 for Charon. A method for
image reconstruction involving speckle masking is described, together
with high resolution speckle spectroscopy.
Title: Speckle interferometry and related techniques with advanced
technology optical telescope
Authors: Weigelt, G.
Bibcode: 1982SPIE..332..284W
Altcode:
Speckle interferometry techniques are especially attractive with
large future telescopes. For example, a 10m telescope can yield an
angular resolution of 0.01 arc sec in spite of image degradation by
the atmosphere. The limiting magnitude of speckle interferometry is
about 20m. We intend to discuss the following aspects of
speckle methods: (a) The influence of telescope aberrations on speckle
interferometry measurements. We show laboratory simulations of speckle
interferometry with severe stationary telescope aberrations. (b)
Roll deconvolution: a method for reconstructing high-resolution
images from Space Teles-cope data. In the case of the 2.4m Space
Telescope a resolution of about 0.01 arc sec can be achieved. (c)
The reconstruction of direct images (instead of autocorrelations)
from speckle interfero-grams. Applications on data recorded with large
telescopes are discussed. Reconstruction of high-resolution objective
prism spectra with the speckle spectroscopy method.
Title: Coherent arrays of separate optical telescopes in space
project TRIO.
Authors: Labeyrie, A.; Kibblewhite, J.; de Graauw, T.; Noordam, J.;
Weigelt, G.; Roussel, H.
Bibcode: 1982vlbi.conf..477L
Altcode: 1983vlbi.conf..477L
In space, 3 or more telescopes can be stabilized for coherent imaging
at optical wavelengths, providing angular resolutions in the range
10-4 to 10-5 arc-second. TRIO is one such
instrument, currently studied by ESA. In its initial configuration,
it incorporates a pair of one-meter telescopes and a central station
where both light beams are recombined. A second step will be the
expansion into a N-telescope array, spanning several kilometers.
Title: Physikalisches Institut, Angewandte Optik. Jahresbericht
für 1981.
Authors: Weigelt, G.
Bibcode: 1982MitAG..56..111W
Altcode:
No abstract at ADS
Title: Speckle interferometry, speckle holography, speckle
spectroscopy, and reconstruction of high-resolution images from
Space Telescope data.
Authors: Weigelt, G.
Bibcode: 1981siha.conf...95W
Altcode: 1982siha.conf...95W
No abstract at ADS
Title: Physikalisches Institut, Angewandte Optik. Jahresbericht
für 1980.
Authors: Weigelt, G. P.
Bibcode: 1981MitAG..53..115W
Altcode:
No abstract at ADS
Title: Spekle interferometry and speckle holography; techniques
and limitations.
Authors: Weigelt, G.
Bibcode: 1983LowOB...9..144W
Altcode: 1981LowOB...9..144W; 1983IAUCo..62..144W; 1983LowOB.167..144W
The author discusses speckle interferometry and speckle holography
measurements of double and triple stars. Speckle holography with the
ESO 3.6 m telescope yielded direct images with a resolution of 0.03 arc
second (diffraction limit). Finally the author discusses the speckle
rotation method, which can be used to reconstruct high-resolution
images from Space Telescope data.
Title: Landolt-Börnstein. Numerical data and functional
relationships in science and technology. New series. Group VI:
Astronomy, astrophysics and space research. Volume_2. Astronomy and
astrophysics. Extension and supplement to Volume_1. Subvolume a:
methods - constants - solar system.
Authors: Hellwege, K. -H.; Schaifers, K.; Voigt, H. H.; Wolf, R.;
Durrant, C. J.; Behr, A.; West, R. M.; Solf, J.; Weigelt, G.; Schmahl,
G.; Staubert, R.; Trümper, J.; Lemke, D.; Hachenberg, O.; Enslin, H.;
Fricke, W.; Bruzek, A.; Gondolatsch, F.; Ip, W. -H.; Axford, W. I.;
Schubart, J.; Jessberger, E. K.; Rahe, J.; Fechtig, H.; Leinert, C.;
Grün, E.; Pilipp, W.; Scholer, M.; Palme, H.; Suess, H. E.; Zeh,
H. D.; Kirsten, T.
Bibcode: 1981lndf.book.....H
Altcode:
No abstract at ADS
Title: Interferometric methods in optical astronomy
Authors: Weigelt, G.
Bibcode: 1981cto..conf...28W
Altcode:
No abstract at ADS
Title: Spatial and temporal properties of speckle interferograms
Authors: Weigelt, G. P.
Bibcode: 1980AIPC...65..731W
Altcode:
In order to investigate the spatial structure of a three-dimensional
speckle intensity distribution, we have studied the intensity
correlation function of two arbitrary points in a 3-D-speckle field. The
result is an extension of the lateral autocorrelation function of
speckle interferograms first derived by L. I. Goldfischer. Speckle
interferograms will fluctuate temporally if the random object
(rough surface or air turbulence) varies in time. The temporal
properties of speckle interferograms are important for various
applications. Therefore we have developed a method for measuring the
''life time'' of speckles. We record the temporal behaviour of the
speckles with a 16mm-movie camera. The life time is determining by
measuring the average crosscorrelation of adjacent frames on the
16mm-motion picture films. We used this method to measure the life
time of stellar speckle interferograms. Based on these studies it
was possible to perform speckle interferometry measurements of rather
faint astronomical objects.
Title: Physikalisches Institut, Angewandte Optik. Jahresbericht
für 1979.
Authors: Weigelt, G.
Bibcode: 1980MitAG..49..107W
Altcode:
No abstract at ADS
Title: Stellar speckle interferometry and speckle holography at low
light levels.
Authors: Weigelt, G. P.
Bibcode: 1980SPIE..243..103W
Altcode:
A brief review of speckle interferometry and speckle holography
techniques is presented, along with examples of each. The application
of speckle interferometry to the observation of objects near
a point source, i.e., the reconstruction of direct images from
speckle interferograms, is discussed, as is the application of the
technique for observing faint astronomical objects, such as galactic
nuclei and quasars, by measuring the single photon events in speckle
interferograms. The two types of measurements were performed using
the ESO 3.6 m telescope and other telescopes. The techniques have
been used to overcome atmospheric image degradation completely,
making the resolution of the speckle measurements about 30 times
higher than that of ordinary astrophotography. Speckle interferometry
up to 14th magnitude has been achieved, and the measurements yielded
high resolution autocorrelations of the objects. Direct images were
deconvolved using the speckle holography technique.
Title: Optical processing of statistical data.
Authors: Bohm, H.; Lohmann, A. W.; Weigelt, G. P.
Bibcode: 1980SPIE..232..191B
Altcode: 1980SPIE..231..191B
No abstract at ADS
Title: Spatial and temporal properties of speckle interferograms.
Authors: Weigelt, G. P.
Bibcode: 1980ofd..conf..731W
Altcode:
No abstract at ADS
Title: Image restoration of Space Telescope photographs
Authors: Lohmann, A. W.; Weigelt, G. P.
Bibcode: 1980aust.conf..353L
Altcode:
Image deconvolution techniques used for improving the spatial resolution
of the Space Telescope photographs down to about 0.015 arc-seconds
are described.
Title: Speckle interferometry measurements of astronomical objects
with simulated multiple mirror telescopes.
Authors: Bialetzki, J.; Weigelt, G. P.
Bibcode: 1980Optik..55..199B
Altcode:
No abstract at ADS
Title: Applications of digital and optical-digital stellar speckle
interferometry
Authors: Baier, G.; Ebersberger, J.; Lohmann, A.; Weigelt, G.
Bibcode: 1980SPIE..264...58B
Altcode: 1981SPIE..264...58B
The various applications of digital and optical/digital stellar
speckle interferometry are examined. The following applications are
investigated: (1) measurements of close binary stars; (2) dependence
of the signal-to-noise ratio of the reconstructed autocorrelation
on the exposure time of the speckle interferograms and on the number
of processed speckle interferograms; and (3) measurement of the red
giant Omicron Ceti. The advantage of stellar speckle interferometry
over conventional astrophotography is shown to lie in its higher
resolution. The advantage of optical processing is its higher speed
when a large number of images has to be processed. The advantage of
digital processing is its higher photometric accuracy and the high
flexibility of the digital computer.
Title: Speckle Interferometry and Speckle Holography with the
1.5-METER and 3.6-METER ESO Telescopes
Authors: Ebersberger, J.; Weigelt, G.
Bibcode: 1979Msngr..18...24E
Altcode:
That great arch-enemy of all observing astronomers, the seeing, can be
pacified with a method called speckle interferometry. For some years
it has provided us with "real" pictures of close binary systems and
even of the surfaces of some stars, e. g. the well-publicized image
of Betelgeuze. So far, however, the speckle techniquewhich is based
on very short exposures and very long focallengths-has been limited
to comparatively bright objects. Drs. Johannes Ebersberger and
Gerd Weigelt, from the Physics Institute of the Erlangen-Nürnberg
University, Fed. Rep. of Germany, review recent speckle work at La
Silla. It will be good news to many that they are reasonably confident
that objects of magnitude 16 or even fainter may soon be within reach
of speckle interferometry!
Title: Physikalisches Institut, Angewandte Optik. Jahresbericht
für 1978.
Authors: Weigelt, G.
Bibcode: 1979MitAG..46...99W
Altcode: 1979MitAG..46...99.
No abstract at ADS
Title: Speckle interferometry and image reconstruction
Authors: Weigelt, G. P.
Bibcode: 1979hars.proc...33W
Altcode: 1979IAUCo..50...33W
The modifications of speckle interferometry which yields
the autocorrelation of astronomical objects with diffraction
resolution (i.e., 0.02 arc sec) and a 5 m telescope aperture are
investigated. Three image reconstruction methods, (1) speckle holography
for image reconstruction of objects near an unresolvable point source,
(2) speckle masking for image reconstruction of binary stars, and (3)
phase flipping for image reconstruction of centro-symmetric objects,
are examined. A specific example describing the application of speckle
holography to the binary star Zeta Cancri A-B and the triple star ADS
3358 A-B-C is given, employing a 1.8 m telescope. The exposure time,
resolution, brightness limit and isoplanicity for speckle techniques are
also examined, correlating optically neighborhood speckle interferograms
on a 16 mm motion picture film, recorded at 64 frames/sec.
Title: Restoration of Images Degraded by the Atmosphere or Telescope
Aberrations
Authors: Weigelt, G.
Bibcode: 1979ipia.coll..422W
Altcode:
No abstract at ADS
Title: High-resolution astrophotography new isoplanicity measurements
and speckle holography applications.
Authors: Weigelt, G. P.
Bibcode: 1979AcOpt..26.1351W
Altcode:
No abstract at ADS
Title: Speckle holography measurements of the stars Zeta Cancri and
ADS 3358
Authors: Weigelt, G. P.
Bibcode: 1978ApOpt..17.2660W
Altcode:
The use of speckle holography in astronomical studies makes it possible
to achieve angular resolution levels which are considerably better
than those possible in conventional astrophotography. A description
is presented of the first application of speckle holography to actual
astronomical objects. An image was reconstructed of the double star Zeta
Cancri A-B using Zeta Cancri C (located 6 arc seconds apart from A-B)
as reference star. An image of the close double star in the triple
system of ADS 3358 was also reconstructed and an image was obtained
of the complete triple system of ADS 3358 A-B-C by generalizing the
image processing procedure of speckle holography. Speckle holography
is a modification of speckle interferometry. In both techniques
high-resolution information is decoded from speckle interferograms by
autocorrelating speckle interferograms.
Title: Speckle interferometry measurements of 12 binary stars.
Authors: Weigelt, G. P.
Bibcode: 1978A&A....68L...5W
Altcode:
Binary-star measurements by speckle interferometry are reported. The
measurements were performed with a 1-m telescope and with
a 1.8-m telescope. The faintest resolved binary star was ADS
2630 (8.9/9.3 mag; probably the faintest binary star measured by
speckle interferometry). The autocorrelation of this binary star was
reconstructed from only 40 speckle interferograms. The spectroscopic
binary Alpha Aur (separation about 0.06 arcsec) was resolved with the
1.8-m telescope. Four of the measured binary stars were Hyades binaries.
Title: Speckle interferometry with a 1 m-telescope.
Authors: Weigelt, G. P.
Bibcode: 1978A&A....67L..11W
Altcode:
A speckle interferometer was constructed and used for binary star
measurements. The speckle interferometry measurements were performed
with a telescope of relatively small aperture (1 m - telescope of Hoher
List observatory, West Germany). 30 speckle interferograms per binary
star were found to be sufficient to obtain good autocorrelations.
Title: Astronomical speckle interferometry and speckle holography.
Authors: Weigelt, G. P.
Bibcode: 1978ohm..conf..551W
Altcode:
No abstract at ADS
Title: Image reconstruction from astronomical speckle interferograms.
Authors: Lohmann, A. W.; Weigelt, G. P.
Bibcode: 1978otf..conf..479L
Altcode:
Three modifications of speckle interferometry - speckle holography,
speckle masking, and phase flipping - are described, and speckle
interferometric observations of double stars, obtained with a telescope
with 1-meter aperture, are presented. Speckle interferometry,
a method proposed in 1970, is used to obtain higher resolution in
astrophotography than can be obtained by ordinary procedures. Speckle
holography can yield images of multiple stars and objects of any
shape if there is an unresolvable star within the isoplanatic
neighborhood. Speckle masking can be used to reconstruct images of
double stars and similar double objects. Phase flipping can be applied
to star disks when there is no unresolvable reference star within the
isoplanatic neighborhood and to some other symmetric objects. Properties
of speckle interferograms are considered.
Title: Modified astronomical speckle interferometry ``speckle
masking''
Authors: Weigelt, G. P.
Bibcode: 1977OptCo..21...55W
Altcode:
A simple method (speckle masking) for the reconstruction of real
images from astronomical speckle photographs is described. This method
is applicable to a restricted class of objects that includes double
stars. Double stars are the object most frequently observed with speckle
interferometry techniques. Certain other kinds of objects can also be
investigated by the speckle masking method, which should work also at
low light levels. Theory and laboratory experiments are presented.
Title: Speckle-Interferometrie. II. Ergebnisse und Möglichkeiten.
Authors: Lohmann, A.; Reinecke, M.; Ruder, H.; Weigelt, G.
Bibcode: 1977S&W....16..284L
Altcode:
No abstract at ADS
Title: Extended speckle interferometry.
Authors: Weigelt, G. P.
Bibcode: 1975oopg.conf..173W
Altcode:
No abstract at ADS
Title: Extended Speckle interferometry
Authors: Weigelt, G. P.
Bibcode: 1975oopg.meet..173W
Altcode:
Speckle interferometry was invented by Labeyrie (1970). The new
approach when used in the form of a modification introduced by Liu
and Lohmann (1973) makes it possible to obtain high-resolution images
of astronomical objects. It is pointed out that the extended Speckle
interferometry is very similar to Fourier holography. A description is
given of the basic relations of Speckle interferometry, as invented,
and of the characteristics of the extended Speckle interferometry.
Title: Large field speckle interferometry.
Authors: Weigelt, G. P.
Bibcode: 1975Optik..43..111W
Altcode:
No abstract at ADS