Author name code: jeffers
ADS astronomy entries on 2022-09-14
author:"Jeffers, Sandra V."
------------------------------------------------------------------------
Title: The CARMENES search for exoplanets around M dwarfs: Stable
radial-velocity variations at the rotation period of AD~Leonis --
A test case study of current limitations to treating stellar activity
Authors: Kossakowski, D.; Kürster, M.; Henning, Th.; Trifonov, T.;
Caballero, J. A.; Lafarga, M.; Bauer, F. F.; Stock, S.; Kemmer, J.;
Jeffers, S. V.; Amado, P. J.; Pérez-Torres, M.; Béjar, V. J. S.;
Cortés-Contreras, M.; Ribas, I.; Reiners, A.; Quirrenbach, A.;
Aceituno, J.; Baroch, D.; Cifuentes, C.; Dreizler, S.; Forcada,
J. S.; Hatzes, A.; Kaminski, A.; Montes, D.; Morales, J. C.; Pavlov,
A.; Peña, L.; Perdelwitz, V.; Reffert, S.; Revilla, D.; Rodríguez
López, C.; Rosich, A.; Sadegi, S.; Schöfer, P.; Schweitzer, A.;
Zechmeister, M.
Bibcode: 2022arXiv220905814K
Altcode:
Context: A challenge with radial-velocity (RV) data is disentangling
the origin of signals either due to a planetary companion or to
stellar activity. In fact, the existence of a planetary companion
has been proposed, as well as contested, around the relatively
bright, nearby M3.0V star AD Leo at the same period as the stellar
rotation of 2.23d. Aims: We further investigate the nature of this
signal. We introduce new CARMENES optical and near-IR RV data and an
analysis in combination with archival data taken by HIRES and HARPS,
along with more recent data from HARPS-N, GIANO-B, and HPF. Also,
we address the confusion concerning the binarity of AD Leo. Methods:
We consider possible correlations between the RVs and various stellar
activity indicators accessible with CARMENES. We applied models
within a Bayesian framework to determine whether a Keplerian model,
a red-noise quasi-periodic model using a Gaussian process, or a mixed
model would explain the observed data best. We also exclusively focus on
spectral lines potentially associated with stellar activity. Results:
The CARMENES RV data agree with the previously reported periodicity
of 2.23d, correlate with some activity indicators, and exhibit
chromaticity. However, when considering the entire RV data set,
we find that a mixed model composed of a stable and a variable
component performs best. Moreover, when recomputing the RVs using
only spectral lines insensitive to activity, there appears to be
some residual power at the period of interest. We therefore conclude
that it is not possible to determinedly prove that there is no planet
orbiting in synchronization with the stellar rotation given our data,
current tools, machinery, and knowledge of how stellar activity affects
RVs. We do rule out planets more massive than 27M_E (=0.084M_J). We
also exclude any binary companion around AD Leo with Msini > 3-6M_J
on orbital periods <14yr.
Title: Detailed stellar activity analysis and modelling of GJ
832. Reassessment of the putative habitable zone planet GJ 832c
Authors: Gorrini, P.; Astudillo-Defru, N.; Dreizler, S.; Damasso,
M.; Díaz, R. F.; Bonfils, X.; Jeffers, S. V.; Barnes, J. R.; Del
Sordo, F.; Almenara, J. -M.; Artigau, E.; Bouchy, F.; Charbonneau,
D.; Delfosse, X.; Doyon, R.; Figueira, P.; Forveille, T.; Haswell,
C. A.; López-González, M. J.; Melo, C.; Mennickent, R. E.; Gaisné,
G.; Morales Morales, N.; Murgas, F.; Pepe, F.; Rodríguez, E.; Santos,
N. C.; Tal-Or, L.; Tsapras, Y.; Udry, S.
Bibcode: 2022A&A...664A..64G
Altcode: 2022arXiv220607552G
Context. Gliese-832 (GJ 832) is an M2V star hosting a massive planet on
a decade-long orbit, GJ 832b, discovered by radial velocity (RV). Later,
a super Earth or mini-Neptune orbiting within the stellar habitable zone
was reported (GJ 832c). The recently determined stellar rotation period
(45.7 ± 9.3 days) is close to the orbital period of putative planet
c (35.68 ± 0.03 days).
Aims: We aim to confirm or dismiss
the planetary nature of the RV signature attributed to GJ 832c, by
adding 119 new RV data points, new photometric data, and an analysis
of the spectroscopic stellar activity indicators. Additionally, we
update the orbital parameters of the planetary system and search
for additional signals.
Methods: We performed a frequency
content analysis of the RVs to search for periodic and stable
signals. Radial velocity time series were modelled with Keplerians
and Gaussian process (GP) regressions alongside activity indicators
to subsequently compare them within a Bayesian framework.
Results: We updated the stellar rotational period of GJ 832 from
activity indicators, obtaining 37.5+1.4-1.5
days, improving the precision by a factor of 6. The new photometric
data are in agreement with this value. We detected an RV signal
near 18 days (FAP < 4.6%), which is half of the stellar rotation
period. Two Keplerians alone fail at modelling GJ 832b and a second
planet with a 35-day orbital period. Moreover, the Bayesian evidence
from the GP analysis of the RV data with simultaneous activity indices
prefers a model without a second Keplerian, therefore negating the
existence of planet c. Activity indices, photometric and RV
time series 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/cat/J/A+A/664/A64
Title: TOI-1468: A system of two transiting planets, a super-Earth
and a mini-Neptune, on opposite sides of the radius valley
Authors: Chaturvedi, P.; Bluhm, P.; Nagel, E.; Hatzes, A. P.;
Morello, G.; Brady, M.; Korth, J.; Molaverdikhani, K.; Kossakowski,
D.; Caballero, J. A.; Guenther, E. W.; Pallé, E.; Espinoza, N.;
Seifahrt, A.; Lodieu, N.; Cifuentes, C.; Furlan, E.; Amado, P. J.;
Barclay, T.; Bean, J.; Béjar, V. J. S.; Bergond, G.; Boyle, A. W.;
Ciardi, D.; Collins, K. A.; Collins, K. I.; Esparza-Borges, E.; Fukui,
A.; Gnilka, C. L.; Goeke, R.; Guerra, P.; Henning, Th.; Herrero, E.;
Howell, S. B.; Jeffers, S. V.; Jenkins, J. M.; Jensen, E. L. N.;
Kasper, D.; Kodama, T.; Latham, D. W.; López-González, M. J.;
Luque, R.; Montes, D.; Morales, J. C.; Mori, M.; Murgas, F.; Narita,
N.; Nowak, G.; Parviainen, H.; Passegger, V. M.; Quirrenbach, A.;
Reffert, S.; Reiners, A.; Ribas, I.; Ricker, G. R.; Rodríguez, E.;
Rodríguez-López, C.; Schlecker, M.; Schwarz, R. P.; Schweitzer, A.;
Seager, S.; Stefánsson, G.; Stockdale, C.; Tal-Or, L.; Twicken, J. D.;
Vanaverbeke, S.; Wang, G.; Watanabe, D.; Winn, J. N.; Zechmeister, M.
Bibcode: 2022arXiv220810351C
Altcode:
We report the discovery and characterization of two small transiting
planets orbiting the bright M3.0V star TOI-1468 (LSPM J0106+1913), whose
transit signals were detected in the photometric time series in three
sectors of the TESS mission. We confirm the e planetary nature of both
of them using precise radial velocity measurements from the CARMENES
and MAROON-X spectrographs, and supplement them with ground-based
transit photometry. A joint analysis of all these data reveals that
the shorter-period planet, TOI-1468 b ($P_{\rm b}$ = 1.88 d), has a
planetary mass of $M_{\rm b} = 3.21\pm0.24$ $M_{\oplus}$ and a radius
of $R_{\rm b} =1.280^{+0.038}_{-0.039} R_{\oplus}$, resulting in a
density of $\rho_{\rm b} = 8.39^{+ 1.05}_{- 0.92}$ g cm$^{-3}$, which
is consistent with a mostly rocky composition. For the outer planet,
TOI-1468 c ($P_{\rm c} = 15.53$ d), we derive a mass of $M_{\rm c}
= 6.64^{+ 0.67}_{- 0.68}$ $M_{\oplus}$, a radius of $R_{\rm c} =
2.06\pm0.04\,R_{\oplus}$, and a bulk density of $\rho_{c} = 2.00^{+
0.21}_{- 0.19}$ g cm$^{-3}$, which corresponds to a rocky core
composition with a H/He gas envelope. These planets are located on
opposite sides of the radius valley, making our system an interesting
discovery as there are only a handful of other systems with the same
properties. This discovery can further help determine a more precise
location of the radius valley for small planets around M dwarfs and,
therefore, shed more light on planet formation and evolution scenarios.
Title: The HD 260655 system: Two rocky worlds transiting a bright
M dwarf at 10 pc
Authors: Luque, R.; Fulton, B. J.; Kunimoto, M.; Amado, P. J.; Gorrini,
P.; Dreizler, S.; Hellier, C.; Henry, G. W.; Molaverdikhani, K.;
Morello, G.; Peña-Moñino, L.; Pérez-Torres, M.; Pozuelos, F. J.;
Shan, Y.; Anglada-Escudé, G.; Béjar, V. J. S.; Bergond, G.; Boyle,
A. W.; Caballero, J. A.; Charbonneau, D.; Ciardi, D. R.; Dufoer, S.;
Espinoza, N.; Everett, M.; Fischer, D.; Hatzes, A. P.; Henning, Th.;
Hesse, K.; Howard, A. W.; Howell, S. B.; Isaacson, H.; Jeffers, S. V.;
Jenkins, J. M.; Kane, S. R.; Kemmer, J.; Khalafinejad, S.; Kidwell,
R. C.; Kossakowski, D.; Latham, D. W.; Lillo-Box, J.; Lissauer, J. J.;
Montes, D.; Orell-Miquel, J.; Pallé, E.; Pollacco, D.; Quirrenbach,
A.; Reffert, S.; Reiners, A.; Ribas, I.; Ricker, G. R.; Rogers, L. A.;
Sanz-Forcada, J.; Schlecker, M.; Schweitzer, A.; Seager, S.; Shporer,
A.; Stassun, K. G.; Stock, S.; Tal-Or, L.; Ting, E. B.; Trifonov,
T.; Vanaverbeke, S.; Vanderspek, R.; Villaseñor, J.; Winn, J. N.;
Winters, J. G.; Zapatero Osorio, M. R.
Bibcode: 2022A&A...664A.199L
Altcode: 2022arXiv220410261L
We report the discovery of a multiplanetary system transiting the
M0 V dwarf HD 260655 (GJ 239, TOI-4599). The system consists of at
least two transiting planets, namely HD 260655 b, with a period of
2.77 d, a radius of Rb = 1.240 ± 0.023 R⊕,
a mass of Mb = 2.14 ± 0.34 M⊕, and a bulk
density of ρb = 6.2 ± 1.0 g cm−3, and HD
260655 c, with a period of 5.71 d, a radius of {R_c} = 1.533 -
0.046 + 0.051{R_ \oplus }, a mass of Mc =
3.09 ± 0.48 M⊕, and a bulk density of {ρ _c} = 4.7
- 0.8 + 0.9{{g}} g cm−3. The planets
have been detected in transit by the Transiting Exoplanet Survey
Satellite (TESS) mission and confirmed independently with archival
and new precise radial velocities obtained with the HIRES and CARMENES
instruments since 1998 and 2016, respectively. At a distance of 10 pc,
HD 260655 has become the fourth closest known multitransiting planet
system after HD 219134, LTT 1445 A, and AU Mic. Due to the apparent
brightness of the host star (J = 6.7 mag), both planets are among the
most suitable rocky worlds known today for atmospheric studies with
the James Webb Space Telescope, both in transmission and emission.
Title: Linking chromospheric activity and magnetic field properties
for late-type dwarf stars
Authors: Brown, E. L.; Jeffers, S. V.; Marsden, S. C.; Morin, J.;
Boro Saikia, S.; Petit, P.; Jardine, M. M.; See, V.; Vidotto, A. A.;
Mengel, M. W.; Dahlkemper, M. N.; the BCool Collaboration
Bibcode: 2022MNRAS.514.4300B
Altcode: 2022arXiv220503108B
Spectropolarimetric data allow for simultaneous monitoring of
stellar chromospheric $\log {R^{\prime }_{\rm {HK}}}$ activity and
the surface-averaged longitudinal magnetic field, Bl,
giving the opportunity to probe the relationship between large-scale
stellar magnetic fields and chromospheric manifestations of
magnetism. We present $\log {R^{\prime }_{\rm {HK}}}$ and/or
Bl measurements for 954 mid-F to mid-M stars derived
from spectropolarimetric observations contained within the PolarBase
database. Our magnetically active sample complements previous stellar
activity surveys that focus on inactive planet-search targets. We find
a positive correlation between mean $\log {R^{\prime }_{\rm {HK}}}$
and mean log |Bl|, but for G stars the relationship may
undergo a change between $\log {R^{\prime }_{\rm {HK}}}\sim -4.4$
and -4.8. The mean $\log {R^{\prime }_{\rm {HK}}}$ shows a similar
change with respect to the $\log {R^{\prime }_{\rm {HK}}}$ variability
amplitude for intermediately active G stars. We also combine our results
with archival chromospheric activity data and published observations
of large-scale magnetic field geometries derived using Zeeman-Doppler
Imaging. The chromospheric activity data indicate a slight under-density
of late-F to early-K stars with $-4.75\le \log {R^{\prime }_{\rm HK}}\le
-4.5$. This is not as prominent as the original Vaughan-Preston gap, and
we do not detect similar under-populated regions in the distributions
of the mean |Bl|, or the Bl and $\log {R^{\prime
}_{\rm HK}}$ variability amplitudes. Chromospheric activity, activity
variability, and toroidal field strength decrease on the main sequence
as rotation slows. For G stars, the disappearance of dominant toroidal
fields occurs at a similar chromospheric activity level as the change in
the relationships between chromospheric activity, activity variability,
and mean field strength.
Title: VizieR Online Data Catalog: GJ 832 stellar activity (Gorrini+,
2022)
Authors: Gorrini, P.; Astudillo-Defru, N.; Dreizler, S.; Damasso,
M.; Diaz, R. F.; Bonfils, X.; Jeffers, S. V.; Barnes, J. R.; Del
Sordo, F.; Almenara, J. -M.; Artigau, E.; Bouchy, F.; Charbonneau,
D.; Delfosse, X.; Doyon, R.; Figueira, P.; Forveille, T.; Haswell,
C. A.; Lopez-Gonzalez, M. J.; Melo, C.; Mennickent, R. E.; Gaisne,
G.; Morales, N.; Murgas, F.; Pepe, F.; Rodriguez, E.; Santos, N. C.;
Tal-Or, L.; Tsapras, Y.; Udry, S.
Bibcode: 2022yCat..36640064G
Altcode:
This work makes use of data from HARPS, the University College London
Echelle Spectrograph (UCLES) , and the Planet Finding Spectrograph
(PFS). HARPS data are available as raw images and reduced spectra,
while we accessed UCLES and PFS data only as RV time series. We used
a total of 227 RV data points for GJ 832. (3 data files).
Title: Exploring the magnetism of stars using TESS data
Authors: Soto, J. I.; Jeffers, S. V.; Schleicher, D. R. G.; Rosales,
J. A.
Bibcode: 2022BAAA...63...77S
Altcode:
Some aspects of the origin of magnetic activity in stars are still not
sufficiently understood. While initial investigations exploring the
relationship between the stellar rotation period and magnetic activity
indicated the possible existence of an active and an inactive branch,
with more recent data it is less clear whether these are two distinct
regimes. This could be a consequence of rotation-dependent dynamo
action, which produces magnetic fields that are involved in stellar
activity. In this study, we explore whether TESS data can be used to
derive stellar rotation periods using the Generalised Lomb-Scargle
and Wavelet methods, and test whether the two methods yield consistent
results.
Title: The CARMENES search for exoplanets around M dwarfs. Rotational
variation in activity indicators of Ross 318, YZ CMi, TYC 3529-1437-1,
and EV Lac
Authors: Schöfer, P.; Jeffers, S. V.; Reiners, A.; Zechmeister,
M.; Fuhrmeister, B.; Lafarga, M.; Ribas, I.; Quirrenbach, A.; Amado,
P. J.; Caballero, J. A.; Anglada-Escudé, G.; Bauer, F. F.; Béjar,
V. J. S.; Cortés-Contreras, M.; Alonso, E. Díez; Dreizler, S.;
Guenther, E. W.; Herbort, O.; Johnson, E. N.; Kaminski, A.; Kürster,
M.; Montes, D.; Morales, J. C.; Pedraz, S.; Tal-Or, L.
Bibcode: 2022A&A...663A..68S
Altcode: 2022arXiv220411685S
Context. The Calar Alto high-Resolution search for M dwarfs with
Exo-earths with Near-infrared and optical Échelle Spectrographs
(CARMENES) instrument is searching for periodic radial-velocity (RV)
variations of M dwarfs, which are induced by orbiting planets. However,
there are other potential sources of such variations, including
rotational modulation caused by stellar activity.
Aims: We
aim to investigate four M dwarfs (Ross 318, YZ CMi, TYC 3529-1437-1,
and EV Lac) with different activity levels and spectral sub-types. Our
goal is to compare the periodicities seen in 22 activity indicators
and the stellar RVs, and to examine their stability over time.
Methods: For each star, we calculated generalised Lomb-Scargle
periodograms of pseudo-equivalent widths of chromospheric lines,
indices of photospheric bands, the differential line width as a measure
of the width of the average photospheric absorption line, the RV, the
chromatic index that describes the wavelength dependence of the RV,
and parameters of the cross-correlation function. We also calculated
periodograms for subsets of the data and compared our results to TESS
photometry.
Results: We find the rotation periods of all four
stars to manifest themselves in the RV and photospheric indicators,
particularly the TiO 7050 index, whereas the chromospheric lines
show clear signals only at lower activity levels. For EV Lac and
TYC 3529-1437-1, we find episodes during which indicators vary with
the rotation period, and episodes during which they vary with half
the rotation period, similarly to photometric light curves.
Conclusions: The changing periodicities reflect the evolution of stellar
activity features on the stellar surface. We therefore conclude that
our results not only emphasise the importance of carefully analysing
indicators complementary to the RV in RV surveys, but they also suggest
that it is also useful to search for signals in activity indicators
in subsets of the dataset, because an activity signal that is present
in the RV may not be visible in the activity indicators all the time,
in particular for the most active stars.
Title: The CARMENES search for exoplanets around M
dwarfs. Benchmarking the impact of activity in high-precision radial
velocity measurements
Authors: Jeffers, S. V.; Barnes, J. R.; Schöfer, P.; Quirrenbach,
A.; Zechmeister, M.; Amado, P. J.; Caballero, J. A.; Fernández,
M.; Rodríguez, E.; Ribas, I.; Reiners, A.; Cardona Guillén, C.;
Cifuentes, C.; Czesla, S.; Hatzes, A. P.; Kürster, M.; Montes, D.;
Morales, J. C.; Pedraz, S.; Sadegi, S.
Bibcode: 2022A&A...663A..27J
Altcode: 2022arXiv220300415J
Context. Current exoplanet surveys using the radial velocity
(RV) technique are targeting M dwarfs because any habitable zone
terrestrial-mass planets will induce a high RV and orbit on shorter
periods than for more massive stars. One of the main caveats is
that M dwarfs show a wide range of activity levels from inactive
to very active, which can induce an asymmetry in the line profiles
and, consequently, a spurious RV measurement.
Aims: We aim
to benchmark the impact of stellar activity on high-precision RV
measurements using regular-cadence CARMENES visible and near-infrared
observations of the active M3.5 dwarf EV Lac.
Methods: We used the newly developed technique of low-resolution
Doppler imaging to determine the centre-of-light, or spot-induced
RV component, for eight observational epochs.
Results: We
confirm a statistically significant and strong correlation between
the independently measured centre-of-light and the chromatic index,
which is a measure of the amplitude variation with wavelength of
the RVs. We also find circular "closed-loop" relations of several
activity indices with RV for a subset of data that covers only several
rotation periods. We also investigate the implications of large phase
gaps in the periodograms of activity indicators. Finally, by removing
the spot-induced RV component we improve the planet-mass sensitivity
by a factor of at least three.
Conclusions: We conclude that
for active M stars, a regular-cadence observing strategy is the most
efficient way to identify and eliminate sources of correlated noise.
Title: Magnetism, rotation, and nonthermal emission in cool
stars. Average magnetic field measurements in 292 M dwarfs
Authors: Reiners, A.; Shulyak, D.; Käpylä, P. J.; Ribas, I.; Nagel,
E.; Zechmeister, M.; Caballero, J. A.; Shan, Y.; Fuhrmeister, B.;
Quirrenbach, A.; Amado, P. J.; Montes, D.; Jeffers, S. V.; Azzaro,
M.; Béjar, V. J. S.; Chaturvedi, P.; Henning, Th.; Kürster, M.;
Pallé, E.
Bibcode: 2022A&A...662A..41R
Altcode: 2022arXiv220400342R
Stellar dynamos generate magnetic fields that are of fundamental
importance to the variability and evolution of Sun-like and low-mass
stars, and for the development of their planetary systems. As a
key to understanding stellar dynamos, empirical relations between
stellar parameters and magnetic fields are required for comparison to
ab initio predictions from dynamo models. We report measurements of
surface-average magnetic fields in 292 M dwarfs from a comparison with
radiative transfer calculations; for 260 of them, this is the first
measurement of this kind. Our data were obtained from more than 15 000
high-resolution spectra taken during the CARMENES project. They reveal
a relation between average field strength, ⟨B⟩, and Rossby number,
Ro, resembling the well-studied rotation-activity relation. Among the
slowly rotating stars, we find that magnetic flux, ΦB,
is proportional to rotation period, P, and among the rapidly rotating
stars that average surface fields do not grow significantly beyond the
level set by the available kinetic energy. Furthermore, we find close
relations between nonthermal coronal X-ray emission, chromospheric
Hα and Ca H&K emission, and magnetic flux. Taken together,
these relations demonstrate empirically that the rotation-activity
relation can be traced back to a dependence of the magnetic dynamo on
rotation. We advocate the picture that the magnetic dynamo generates
magnetic flux on the stellar surface proportional to rotation rate with
a saturation limit set by the available kinetic energy, and we provide
relations for average field strengths and nonthermal emission that
are independent of the choice of the convective turnover time. We also
find that Ca H&K emission saturates at average field strengths of
⟨B⟩≈800 G while Hα and X-ray emission grow further with stronger
fields in the more rapidly rotating stars. This is in conflict with the
coronal stripping scenario predicting that in the most rapidly rotating
stars coronal plasma would be cooled to chromospheric temperatures. Table B.1 is only 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/662/A41
Title: The crucial role of surface magnetic fields for stellar
dynamos: ϵ Eridani, 61 Cygni A, and the Sun
Authors: Jeffers, S. V.; Cameron, R. H.; Marsden, S. C.; Boro Saikia,
S.; Folsom, C. P.; Jardine, M. M.; Morin, J.; Petit, P.; See, V.;
Vidotto, A. A.; Wolter, U.; Mittag, M.
Bibcode: 2022A&A...661A.152J
Altcode: 2022arXiv220107530J
Cool main-sequence stars, such as the Sun, have magnetic fields which
are generated by an internal dynamo mechanism. In the Sun, the dynamo
mechanism produces a balance between the amounts of magnetic flux
generated and lost over the Sun's 11-year activity cycle and it is
visible in the Sun's different atmospheric layers using multi-wavelength
observations. We used the same observational diagnostics, spanning
several decades, to probe the emergence of magnetic flux on the two
close by, active- and low-mass K dwarfs: 61 Cygni A and ϵ Eridani. Our
results show that 61 Cygni A follows the Solar dynamo with a regular
cycle at all wavelengths, while ϵ Eridani represents a more extreme
level of the Solar dynamo, while also showing strong Solar-like
characteristics. For the first time we show magnetic butterfly diagrams
for stars other than the Sun. For the two K stars and the Sun, the rate
at which the toroidal field is generated from surface poloidal field
is similar to the rate at which toroidal flux is lost through flux
emergence. This suggests that the surface field plays a crucial role in
the dynamos of all three stars. Finally, for ϵ Eridani, we show that
the two chromospheric cycle periods, of ∼3 and ∼13 years, correspond
to two superimposed magnetic cycles. The spectropolarimetic
data are available from the Polarbase data archive: http://polarbase.irap.omp.eu/.
Title: Topological changes in the magnetic field of LQ Hya during
an activity minimum
Authors: Lehtinen, J. J.; Käpylä, M. J.; Hackman, T.; Kochukhov, O.;
Willamo, T.; Marsden, S. C.; Jeffers, S. V.; Henry, G. W.; Jetsu, L.
Bibcode: 2022A&A...660A.141L
Altcode: 2019arXiv190911028L
Aims: Previous studies have related surface temperature maps,
obtained with the Doppler imaging (DI) technique, of LQ Hya with
long-term photometry. Here, we compare surface magnetic field maps,
obtained with the Zeeman Doppler imaging (ZDI) technique, with
contemporaneous photometry, with the aim of quantifying the star's
magnetic cycle characteristics.
Methods: We inverted Stokes IV
spectropolarimetry, obtained with the HARPSpol and ESPaDOnS instruments,
into magnetic field and surface brightness maps using a tomographic
inversion code that models high signal-to-noise ratio mean line profiles
produced by the least squares deconvolution (LSD) technique. The maps
were compared against long-term ground-based photometry acquired with
the T3 0.40 m Automatic Photoelectric Telescope (APT) at Fairborn
Observatory, which offers a proxy for the spot cycle of the star,
as well as with chromospheric Ca II H&K activity derived from
the observed spectra.
Results: The magnetic field and surface
brightness maps reveal similar patterns relative to previous DI and
ZDI studies: non-axisymmetric polar magnetic field structure, void of
fields at mid-latitudes, and a complex structure in the equatorial
regions. There is a weak but clear tendency of the polar structures
to be linked with a strong radial field and the equatorial ones
with the azimuthal field. We find a polarity reversal in the radial
field between 2016 and 2017 that is coincident with a spot minimum
seen in the long-term photometry, although the precise relation
of chromospheric activity to the spot activity remains complex
and unclear. The inverted field strengths cannot be easily related
with the observed spottedness, but we find that they are partially
connected to the retrieved field complexity.
Conclusions:
This field topology and the dominance of the poloidal field component,
when compared to global magnetoconvection models for rapidly rotating
young suns, could be explained by a turbulent dynamo, where differential
rotation does not play a major role (so-called 2 or 2 dynamos) and axi-
and non-axisymmetric modes are excited simultaneously. The complex
equatorial magnetic field structure could arise from the twisted
(helical) wreaths often seen in these simulations, while the polar
feature would be connected to the mostly poloidal non-axisymmetric
component that has a smooth spatial structure. The Johnson B-
and V-band differential photometry and the numerical time series
analysis results are only 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/660/A141
Based on observations made with the HARPSpol instrument on the ESO
3.6 m telescope at La Silla (Chile), under the programme IDs 084.D-0338,
086.D-0240 and 0100.D-0176.
Title: VizieR Online Data Catalog: Magnetic fields in 292 M
dwarfs. (Reiners+, 2022)
Authors: Reiners, A.; Shulyak, D.; Kaepylae, P. J.; Ribas, I.; Nagel,
E.; Zechmeister, M.; Caballero, J. A.; Shan, Y.; Fuhrmeister, B.;
Quirrenbach, A.; Amado, P. J.; Montes, D.; Jeffers, S. V.; Azzaro, M.;
Bejar, V. J. S.; Chaturvedi, P.; Henning, T.; Kuerster, M.; Palle, E.
Bibcode: 2022yCat..36620041R
Altcode:
The sample of stars used for our analysis, the number of spectra
co-added for each star, and the approximate S/N around λ=8700Å are
provided in Table B.1. (1 data file).
Title: VizieR Online Data Catalog: VRI photometry and radial velocity
of TOI-1759 (Espinoza+, 2022)
Authors: Espinoza, N.; Palle, E.; Kemmer, J.; Luque, R.; Caballero,
J. A.; Cifuentes, C.; Herrero, E.; Sanchez Bejar, V. J.; Stock, S.;
Molaverdikhani, K.; Morello, G.; Kossakowski, D.; Schlecker, M.; Amado,
P. J.; Bluhm, P.; Cortes-Contreras, M.; Henning, T.; Kreidberg, L.;
Kurster, M.; Lafarga, M.; Lodieu, N.; Morales, J. C.; Oshagh, M.;
Passegger, V. M.; Pavlov, A.; Quirrenbach, A.; Reffert, S.; Reiners,
A.; Ribas, I.; Rodriguez, E.; Lopez, C. R.; Schweitzer, A.; Trifonov,
T.; Chaturvedi, P.; Dreizler, S.; Jeffers, S. V.; Kaminski, A.;
Lopez-Gonzalez, M. J.; Lillo-Box, J.; Montes, D.; Nowak, G.; Pedraz,
S.; Vanaverbeke, S.; Zapatero Osorio, M. R.; Zechmeister, M.; Collins,
K. A.; Girardin, E.; Guerra, P.; Naves, R.; Crossfield, I. J. M.;
Matthews, E. C.; Howell, S. B.; Ciardi, D. R.; Gonzales, E.; Matson,
R. A.; Beichman, C. A.; Schlieder, J. E.; Barclay, T.; Vezie, M.;
Villasenor, J. N.; Daylan, T.; Mireies, I.; Dragomir, D.; Twicken,
J. D.; Jenkins, J.; Winn, J. N.; Latham, D.; Ricker, G.; Seager, S.
Bibcode: 2022yCat..51630133E
Altcode:
The 2 minutes cadence data were processed in the TESS Science Processing
Operations Center (SPOC) photometry and transit search pipelines at
NASA Ames Research Center, in Sectors 16 (2019 September to October),
17 (2019 October to November), and 24 (2020 April to May). Among
the observations, a transit of TOI-1759b in 2020 May 21 was captured by
three independent telescopes/observatories: the OAA telescope of the
Observatori Astronomic Albanya (Spain; precision of 1140ppm; R-filter
observations), the RCO telescope of the Grand-Pra Observatory (Valais
Sion, Switzerland; precision of 1080ppm; ip-filter observations),
and the OMC telescope of the Montcabrer Observatory (Barcelona,
Spain; precision of 1500ppm; Ic-filter observations). Long-term
photometric monitoring was also performed from the ground using the
0.8m Joan Oro telescope (TJO) at the Montsec Observatory in Lleida,
Spain and the 90cm telescope at the Sierra Nevada Observatory (SNO)
in R and V filter. We monitored TOI-1759 with the CARMENES 38
instrument located on the 3.5m telescope at the Calar Alto Observatory
in Almeria, Spain, from 2020 July 24 to 2021 January 17 (R=94600). (3 data files).
Title: Zeeman-Doppler imaging of five young solar-type stars
Authors: Willamo, T.; Lehtinen, J. J.; Hackman, T.; Käpylä, M. J.;
Kochukhov, O.; Jeffers, S. V.; Korhonen, H.; Marsden, S. C.
Bibcode: 2022A&A...659A..71W
Altcode: 2021arXiv211006729W
Context. The magnetic activity of the Sun changes with the solar
cycle. Similar cycles are found in other stars as well, but their
details are not known to a similar degree. Characterising stellar
magnetic cycles is important for the understanding of the stellar and
solar dynamos that are driving the magnetic activity.
Aims: We
present spectropolarimetric observations of five young, solar-type stars
and compare them to previous observations, with the aim to identify and
characterise stellar equivalents of the solar cycle.
Methods:
We use Zeeman-Doppler imaging (ZDI) to map the surface magnetic field
and brightness of our targets. The magnetic field is decomposed into
spherical harmonic expansions, from which we report the strengths of
the axisymmetric versus non-axisymmetric and poloidal versus toroidal
components, and we compare them to the Rossby numbers of the stars.
Results: We present five new ZDI maps of young, solar-type stars
from December 2017. Of special interest is the case of V1358 Ori,
which had gone through a polarity reversal between our observations and
earlier ones. A less evident polarity reversal might also have occurred
in HD 35296. There is a preference for a more axisymmetric field, and
possibly a more toroidal field, for the more active stars with lower
Rossby number, but a larger sample should be studied to draw any strong
conclusions from this. For most of the individual stars, the amounts
of toroidal and poloidal field have stayed on levels similar to those
in earlier observations.
Conclusions: We find evidence for a
magnetic polarity reversal having occurred in V1358 Ori. An interesting
target for future observations is χ1 Ori, which may have
a short magnetic cycle of a few years. The correlation between the
brightness maps and the magnetic field is mostly poor, which could
indicate the presence of small-scale magnetic features of different
polarities that cancel one another out and are thus not resolved in
our maps. The data for the magnetic field and brightness maps
of the stars are only 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/659/A71
Based on observations made with the HARPSpol instrument on the
ESO 3.6 m telescope in La Silla (Chile), under programme IDs 091.D-0836
and 0100.D-0176.
Title: VizieR Online Data Catalog: Light curve of the active star
LQ Hya (Lehtinen+, 2022)
Authors: Lehtinen, J. J.; Kaepylae, M. J.; Hackman, T.; Kochukhov, O.;
Willamo, T.; Marsden, S. C.; Jeffers, S. V.; Henry, G. W.; Jetsu, L.
Bibcode: 2022yCat..36600141L
Altcode:
Detailed time series analysis of B- and V-band photometry of the young
active solar-type star LQ Hya. These data characterise the starspot
evolution of the star and supplement an analysis of simultaneous
magnetic surface maps produced using the Zeeman Doppler imaging
method. The B- and V-band light curves are provided in the files
lqhya_b.dat and lqhya_v.dat as differential photometry against the
comparison star HD 82477. The light curves span from November 1987 to
February 2019. The numerical results of the light curve analysis are
given in the file res.dat. They have been derived using the continuous
period search (CPS) method, described in detail in Lehtinen et
al. (2011A&A...527A.136L, Cat. J/A+A/527/A136). (3 data files).
Title: A Transiting, Temperate Mini-Neptune Orbiting the M Dwarf
TOI-1759 Unveiled by TESS
Authors: Espinoza, Néstor; Pallé, Enric; Kemmer, Jonas; Luque,
Rafael; Caballero, José A.; Cifuentes, Carlos; Herrero, Enrique;
Sánchez Béjar, Víctor J.; Stock, Stephan; Molaverdikhani, Karan;
Morello, Giuseppe; Kossakowski, Diana; Schlecker, Martin; Amado,
Pedro J.; Bluhm, Paz; Cortés-Contreras, Miriam; Henning, Thomas;
Kreidberg, Laura; Kürster, Martin; Lafarga, Marina; Lodieu, Nicolas;
Morales, Juan Carlos; Oshagh, Mahmoudreza; Passegger, Vera M.; Pavlov,
Alexey; Quirrenbach, Andreas; Reffert, Sabine; Reiners, Ansgar; Ribas,
Ignasi; Rodríguez, Eloy; López, Cristina Rodríguez; Schweitzer,
Andreas; Trifonov, Trifon; Chaturvedi, Priyanka; Dreizler, Stefan;
Jeffers, Sandra V.; Kaminski, Adrian; López-González, María José;
Lillo-Box, Jorge; Montes, David; Nowak, Grzegorz; Pedraz, Santos;
Vanaverbeke, Siegfried; Zapatero Osorio, Maria R.; Zechmeister,
Mathias; Collins, Karen A.; Girardin, Eric; Guerra, Pere; Naves,
Ramon; Crossfield, Ian J. M.; Matthews, Elisabeth C.; Howell, Steve
B.; Ciardi, David R.; Gonzales, Erica; Matson, Rachel A.; Beichman,
Charles A.; Schlieder, Joshua E.; Barclay, Thomas; Vezie, Michael;
Villaseñor, Jesus Noel; Daylan, Tansu; Mireies, Ismael; Dragomir,
Diana; Twicken, Joseph D.; Jenkins, Jon; Winn, Joshua N.; Latham,
David; Ricker, George; Seager, Sara
Bibcode: 2022AJ....163..133E
Altcode: 2022arXiv220201240E
We report the discovery and characterization of TOI-1759 b, a temperate
(400 K) sub-Neptune-sized exoplanet orbiting the M dwarf TOI-1759
(TIC 408636441). TOI-1759 b was observed by TESS to transit in
Sectors 16, 17, and 24, with only one transit observed per sector,
creating an ambiguity regarding the orbital period of the planet
candidate. Ground-based photometric observations, combined with
radial-velocity measurements obtained with the CARMENES spectrograph,
confirm an actual period of 18.85019 ± 0.00014 days. A joint
analysis of all available photometry and radial velocities reveals a
radius of 3.17 ± 0.10 R ⊕ and a mass of 10.8 ± 1.5 M
⊕. Combining this with the stellar properties derived
for TOI-1759 (R ⋆ = 0.597 ± 0.015 R ⊙;
M ⋆ = 0.606 ± 0.020 M ⊙; T eff
= 4065 ± 51 K), we compute a transmission spectroscopic metric
(TSM) value of over 80 for the planet, making it a good target for
transmission spectroscopy studies. TOI-1759 b is among the top five
temperate, small exoplanets (T eq < 500 K, R
p < 4 R ⊕) with the highest TSM discovered to
date. Two additional signals with periods of 80 days and >200 days
seem to be present in our radial velocities. While our data suggest
both could arise from stellar activity, the later signal's source and
periodicity are hard to pinpoint given the ~200 days baseline of our
radial-velocity campaign with CARMENES. Longer baseline radial-velocity
campaigns should be performed in order to unveil the true nature of
this long-period signal.
Title: Discovery and mass measurement of the hot, transiting,
Earth-sized planet, GJ 3929 b
Authors: Kemmer, J.; Dreizler, S.; Kossakowski, D.; Stock,
S.; Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Collins,
K. A.; Espinoza, N.; Herrero, E.; Jenkins, J. M.; Latham, D. W.;
Lillo-Box, J.; Narita, N.; Pallé, E.; Reiners, A.; Ribas, I.;
Ricker, G.; Rodríguez, E.; Seager, S.; Vanderspek, R.; Wells, R.;
Winn, J.; Aceituno, F. J.; Béjar, V. J. S.; Barclay, T.; Bluhm, P.;
Chaturvedi, P.; Cifuentes, C.; Collins, K. I.; Cortés-Contreras, M.;
Demory, B. -O.; Fausnaugh, M. M.; Fukui, A.; Gómez Maqueo Chew, Y.;
Galadí-Enríquez, D.; Gan, T.; Gillon, M.; Golovin, A.; Hatzes, A. P.;
Henning, Th.; Huang, C.; Jeffers, S. V.; Kaminski, A.; Kunimoto,
M.; Kürster, M.; López-González, M. J.; Lafarga, M.; Luque,
R.; McCormac, J.; Molaverdikhani, K.; Montes, D.; Morales, J. C.;
Passegger, V. M.; Reffert, S.; Sabin, L.; Schöfer, P.; Schanche, N.;
Schlecker, M.; Schroffenegger, U.; Schwarz, R. P.; Schweitzer, A.;
Sota, A.; Tenenbaum, P.; Trifonov, T.; Vanaverbeke, S.; Zechmeister, M.
Bibcode: 2022A&A...659A..17K
Altcode: 2022arXiv220200970K
We report the discovery of GJ 3929 b, a hot Earth-sized planet orbiting
the nearby M3.5 V dwarf star, GJ 3929 (G 180-18, TOI-2013). Joint
modelling of photometric observations from TESS sectors 24 and 25
together with 73 spectroscopic observations from CARMENES and follow-up
transit observations from SAINT-EX, LCOGT, and OSN yields a planet
radius of Rb = 1.150 ± 0.040 R⊕, a mass of
Mb = 1.21 ± 0.42 M⊕, and an orbital period
of Pb = 2.6162745 ± 0.0000030 d. The resulting density
of ρb = 4.4 ± 1.6 g cm−3 is compatible with
the Earth's mean density of about 5.5 g cm−3. Due to the
apparent brightness of the host star (J = 8.7 mag) and its small size,
GJ 3929 b is a promising target for atmospheric characterisation with
the JWST. Additionally, the radial velocity data show evidence for
another planet candidate with P[c] = 14.303 ± 0.035 d, which
is likely unrelated to the stellar rotation period, Prot
= 122 ± 13 d, which we determined from archival HATNet and ASAS-SN
photometry combined with newly obtained TJO data. RV data and
stellar activity indices are only 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/659/A17
Title: VizieR Online Data Catalog: GJ 3929 b RVs and activity
indicators (Kemmer+, 2022)
Authors: Kemmer, J.; Dreizler, S.; Kossakowski, D.; Stock, S.;
Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Collins, K. A.;
Espinoza, N.; Herrero, E.; Jenkins, J. M.; Latham, D. W.; Lillo-Box,
J.; Narita, N.; Palle, E.; Reiners, A.; Ribas, I.; Ricker, G.;
Rodriguez, E.; Seager, S.; Vanderspek, R.; Wells, R.; Winn, J.;
Aceituno, F. J.; Bejar, V. J. S.; Barclay, T.; Bluhm, P.; Chaturvedi,
P.; Cifuentes, C.; Collins, K. I.; Cortes-Contreras, M.; Demory, B. O.;
Fausnaugh, M. M.; Fukui, A.; Gomez Maqueo Chew, Y.; Galadi-Enriquez,
D.; Gan, T.; Gillon, M.; Golovin, A.; Hatzes, A. P.; Henning, T.;
Huang, C.; Jeffers, S. V.; Kaminski, A.; Kunimoto, M.; Kurster,
M.; Lopez-Gonzalez, M. J.; Lafarga, M.; Luque, R.; McCormac, J.;
Molaverdikhani, K.; Montes, D.; Morales, J. C.; Passegger, V. M.;
Reffert, S.; Sabin, L.; Schoefer, P.; Schanche, N.; Schlecker,
M.; Schroffenegger, U.; Schwarz, R. P.; Schweitzer, A.; Sota, A.;
Tenenbaum, P.; Trifonov, T.; Vanaverbeke, S.; Zechmeister, M.
Bibcode: 2022yCat..36590017K
Altcode:
Radial velocities and activity indices of GJ 3929 acquired with CARMENES
(Quirrenbach et al., 2014, in Proc. SPIE, Vol. 9147, Ground-based and
Airborne Instrumentation for Astronomy V, 91471F), a high-resolution
precise echelle spectrograph mounted at the 3.5m telescope at the
Calar Alto Observatory in Spain. (1 data file).
Title: A multi-planetary system orbiting the early-M dwarf TOI-1238
Authors: González-Álvarez, E.; Zapatero Osorio, M. R.; Sanz-Forcada,
J.; Caballero, J. A.; Reffert, S.; Béjar, V. J. S.; Hatzes, A. P.;
Herrero, E.; Jeffers, S. V.; Kemmer, J.; López-González, M. J.;
Luque, R.; Molaverdikhani, K.; Morello, G.; Nagel, E.; Quirrenbach,
A.; Rodríguez, E.; Rodríguez-López, C.; Schlecker, M.; Schweitzer,
A.; Stock, S.; Passegger, V. M.; Trifonov, T.; Amado, P. J.; Baker,
D.; Boyd, P. T.; Cadieux, C.; Charbonneau, D.; Collins, K. A.; Doyon,
R.; Dreizler, S.; Espinoza, N.; Fűrész, G.; Furlan, E.; Hesse, K.;
Howell, S. B.; Jenkins, J. M.; Kidwell, R. C.; Latham, D. W.; McLeod,
K. K.; Montes, D.; Morales, J. C.; O'Dwyer, T.; Pallé, E.; Pedraz,
S.; Reiners, A.; Ribas, I.; Quinn, S. N.; Schnaible, C.; Seager, S.;
Skinner, B.; Smith, J. C.; Schwarz, R. P.; Shporer, A.; Vanderspek,
R.; Winn, J. N.
Bibcode: 2022A&A...658A.138G
Altcode: 2021arXiv211114602G
Context. The number of super-Earth and Earth-mass planet discoveries has
increased significantly in the last two decades thanks to the Doppler
radial velocity and planetary transit observing techniques. Either
technique can detect planet candidates on its own, but the power
of a combined photometric and spectroscopic analysis is unique for
an insightful characterization of the planets, which in turn has
repercussions for our understanding of the architecture of planetary
systems and, therefore, their formation and evolution.
Aims: Two
transiting planet candidates with super-Earth radii around the nearby
(d = 70.64 ± 0.06 pc) K7-M0 dwarf star TOI-1238 were announced by
NASA's Transiting Exoplanet Survey Satellite (TESS), which observed
the field of TOI-1238 in four different sectors. We aim to validate
their planetary nature using precise radial velocities taken with
the CARMENES spectrograph.
Methods: We obtained 55 CARMENES
radial velocity measurements that span the 11 months between 9 May
2020 and 5 April 2021. For a better characterization of the parent
star's activity, we also collected contemporaneous optical photometric
observations at the Joan Oró and Sierra Nevada observatories and
retrieved archival photometry from the literature. We performed a
combined TESS+CARMENES photometric and spectroscopic analysis by
including Gaussian processes and Keplerian orbits to account for the
stellar activity and planetary signals simultaneously.
Results:
We estimate that TOI-1238 has a rotation period of 40 ± 5 d based on
photometric and spectroscopic data. The combined analysis confirms the
discovery of two transiting planets, TOI-1238 b and c, with orbital
periods of 0.764597−0.000011+0.000013
d and 3.294736−0.000036+0.000034 d,
masses of 3.76−1.07+1.15 M⊕
and 8.32−1.88+1.90 M⊕, and
radii of 1.21−0.10+0.11 R⊕ and
2.11−0.14+0.14 R⊕. They orbit
their parent star at semimajor axes of 0.0137 ± 0.0004 au and 0.036 ±
0.001 au, respectively.The two planets are placed on opposite sides of
the radius valley for M dwarfs and lie between the star and the inner
border of TOI-1238's habitable zone. The inner super-Earth TOI-1238
b is one of the densest ultra-short-period planets ever discovered
(ρ = 11.7−3.4+4.2 g cm−3). The
CARMENES data also reveal the presence of an outer, non-transiting,
more massive companion with an orbital period and radial velocity
amplitude of ≥600 d and ≥70 m s−1, which implies a
likely mass of M ≥ 2 √(1− e2) MJup and a
separation ≥1.1 au from its parent star.
Title: Time evolution of magnetic activity cycles in young suns:
The curious case of κ Ceti
Authors: Boro Saikia, S.; Lüftinger, T.; Folsom, C. P.; Antonova,
A.; Alecian, E.; Donati, J. -F.; Guedel, M.; Hall, J. C.; Jeffers,
S. V.; Kochukhov, O.; Marsden, S. C.; Metodieva, Y. T.; Mittag, M.;
Morin, J.; Perdelwitz, V.; Petit, P.; Schmid, M.; Vidotto, A. A.
Bibcode: 2022A&A...658A..16B
Altcode: 2021arXiv211006000B
Context. A detailed investigation of the magnetic properties of young
Sun-like stars can provide valuable information on our Sun's magnetic
past and its impact on the early Earth.
Aims: We determine the
properties of the moderately rotating young Sun-like star κ Ceti's
magnetic and activity cycles using 50 yr of chromospheric activity data
and six epochs of spectropolarimetric observations.
Methods:
The chromospheric activity was determined by measuring the flux in
the Ca II H and K lines. A generalised Lomb-Scargle periodogram and
a wavelet decomposition were used on the chromospheric activity data
to establish the associated periodicities. The vector magnetic field
of the star was reconstructed using the technique of Zeeman Doppler
imaging on the spectropolarimetric observations.
Results:
Our period analysis algorithms detect a 3.1 yr chromospheric cycle in
addition to the star's well-known ~6 yr cycle period. Although the two
cycle periods have an approximate 1:2 ratio, they exhibit an unusual
temporal evolution. Additionally, the spectropolarimetric data analysis
shows polarity reversals of the star's large-scale magnetic field,
suggesting a ~10 yr magnetic or Hale cycle.
Conclusions: The
unusual evolution of the star's chromospheric cycles and their lack
of a direct correlation with the magnetic cycle establishes κ Ceti
as a curious young Sun. Such complex evolution of magnetic activity
could be synonymous with moderately active young Suns, which is an
evolutionary path that our own Sun could have taken.
Title: Coronal Mass Ejections and Type II Radio Emission Variability
during a Magnetic Cycle on the Solar-type Star ϵ Eridani
Authors: Ó Fionnagáin, Dúalta; Kavanagh, Robert D.; Vidotto,
Aline A.; Jeffers, Sandra V.; Petit, Pascal; Marsden, Stephen; Morin,
Julien; Golden, Aaron
Bibcode: 2022ApJ...924..115O
Altcode: 2021arXiv211102284F
We simulate possible stellar coronal mass ejection (CME) scenarios
over the magnetic cycle of ϵ Eridani (18 Eridani; HD 22049). We use
three separate epochs from 2008, 2011, and 2013, and estimate the
radio emission frequencies associated with these events. These stellar
eruptions have proven to be elusive, although a promising approach
to detect and characterize these phenomena are low-frequency radio
observations of potential type II bursts as CME-induced shocks propagate
through the stellar corona. Stellar type II radio bursts are expected
to emit below 450 MHz, similarly to their solar counterparts. We show
that the length of time these events remain above the ionospheric
cutoff is not necessarily dependent on the stellar magnetic cycle,
but more on the eruption location relative to the stellar magnetic
field. We find that these type II bursts would remain within the
frequency range of LOFAR for a maximum of 20-30 minutes post-eruption
for the polar CMEs (50 minutes for second harmonics). We find evidence
of slower equatorial CMEs, which result in slightly longer observable
windows for the 2008 and 2013 simulations. Stellar magnetic geometry
and strength have a significant effect on the detectability of these
events. We place the CMEs in the context of the stellar mass-loss rate
(27-48× solar mass-loss rate), showing that they can amount to 3%-50%
of the stellar wind mass-loss rate for ϵ Eridani. Continuous monitoring
of likely stellar CME candidates with low-frequency radio telescopes
will be required to detect these transient events.
Title: The CARMENES search for exoplanets around M dwarfs. Diagnostic
capabilities of strong K I lines for photosphere and chromosphere
Authors: Fuhrmeister, B.; Czesla, S.; Nagel, E.; Reiners, A.; Schmitt,
J. H. M. M.; Jeffers, S. V.; Caballero, J. A.; Shulyak, D.; Johnson,
E. N.; Zechmeister, M.; Montes, D.; López-Gallifa, Á.; Ribas, I.;
Quirrenbach, A.; Amado, P. J.; Galadí-Enríquez, D.; Hatzes, A. P.;
Kürster, M.; Danielski, C.; Béjar, V. J. S.; Kaminski, A.; Morales,
J. C.; Zapatero Osorio, M. R.
Bibcode: 2022A&A...657A.125F
Altcode: 2021arXiv211101552F
There are several strong K I lines found in the spectra of M dwarfs,
among them the doublet near 7700 Å and another doublet near 12 500
Å. We study these optical and near-infrared doublets in a sample of
324 M dwarfs, observed with CARMENES, the high-resolution optical and
near-infrared spectrograph at Calar Alto, and investigate how well the
lines can be used as photospheric and chromospheric diagnostics. Both
doublets have a dominant photospheric component in inactive stars
and can be used as tracers of effective temperature and gravity. For
variability studies using the optical doublet, we concentrate on
the red line component because this is less prone to artefacts from
telluric correction in individual spectra. The optical doublet lines
are sensitive to activity, especially for M dwarfs later than M5.0 V
where the lines develop an emission core. For earlier type M dwarfs,
the red component of the optical doublet lines is also correlated
with Hα activity. We usually find positive correlation for stars with
Hα in emission, while early-type M stars with Hα in absorption show
anti-correlation. During flares, the optical doublet lines can exhibit
strong fill-in or emission cores for our latest spectral types. On
the other hand, the near-infrared doublet lines very rarely show
correlation or anti-correlation to Hα and do not change line shape
significantly even during the strongest observed flares. Nevertheless,
the near-infrared doublet lines show notable resolved Zeeman splitting
for about 20 active stars which allows to estimate the magnetic fields
B. Full Table 2 is only 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/657/A125
Title: TOI-1201 b: A mini-Neptune transiting a bright and moderately
young M dwarf
Authors: Kossakowski, D.; Kemmer, J.; Bluhm, P.; Stock, S.; Caballero,
J. A.; Béjar, V. J. S.; Guillén, C. Cardona; Lodieu, N.; Collins,
K. A.; Oshagh, M.; Schlecker, M.; Espinoza, N.; Pallé, E.; Henning,
Th.; Kreidberg, L.; Kürster, M.; Amado, P. J.; Anderson, D. R.;
Morales, J. C.; Cartwright, S.; Charbonneau, D.; Chaturvedi, P.;
Cifuentes, C.; Conti, D. M.; Cortés-Contreras, M.; Dreizler, S.;
Galadí-Enríquez, D.; Guerra, P.; Hart, R.; Hellier, C.; Henze,
C.; Herrero, E.; Jeffers, S. V.; Jenkins, J. M.; Jensen, E. L. N.;
Kaminski, A.; Kielkopf, J. F.; Kunimoto, M.; Lafarga, M.; Latham,
D. W.; Lillo-Box, J.; Luque, R.; Molaverdikhani, K.; Montes, D.;
Morello, G.; Morgan, E. H.; Nowak, G.; Pavlov, A.; Perger, M.;
Quintana, E. V.; Quirrenbach, A.; Reffert, S.; Reiners, A.; Ricker,
G.; Ribas, I.; López, C. Rodríguez; Osorio, M. R. Zapatero; Seager,
S.; Schöfer, P.; Schweitzer, A.; Trifonov, T.; Vanaverbeke, S.;
Vanderspek, R.; West, R.; Winn, J.; Zechmeister, M.
Bibcode: 2021A&A...656A.124K
Altcode: 2021arXiv210909346K
We present the discovery of a transiting mini-Neptune around TOI-1201,
a relatively bright and moderately young early M dwarf (J ≈ 9.5
mag, ~600-800 Myr) in an equal-mass ~8 arcsecond-wide binary system,
using data from the Transiting Exoplanet Survey Satellite, along with
follow-up transit observations. With an orbital period of 2.49 d,
TOI-1201 b is a warm mini-Neptune with a radius of Rb =
2.415 ± 0.090 R⊕. This signal is also present in the
precise radial velocity measurements from CARMENES, confirming the
existence of the planet and providing a planetary mass of Mb
= 6.28 ± 0.88 M⊕ and, thus, an estimated bulk density
of 2.45−0.42+0.48 g cm−3. The
spectroscopic observations additionally show evidence of a signal
with a period of 19 d and a long periodic variation of undetermined
origin. In combination with ground-based photometric monitoring
from WASP-South and ASAS-SN, we attribute the 19 d signal to the
stellar rotation period (Prot = 19-23 d), although we
cannot rule out that the variation seen in photometry belongs to
the visually close binary companion. We calculate precise stellar
parameters for both TOI-1201 and its companion. The transiting
planet is anexcellent target for atmosphere characterization (the
transmission spectroscopy metric is 97−16+21)
with the upcoming James Webb Space Telescope. It is also feasible to
measure its spin-orbit alignment via the Rossiter-McLaughlin effect
using current state-of-the-art spectrographs with submeter per second
radial velocity precision. Additional data (i.e., stellar activity
indicators) are only 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/656/A124
Title: The CARMENES search for exoplanets around M dwarfs. Stellar
atmospheric parameters of target stars with SteParSyn
Authors: Marfil, E.; Tabernero, H. M.; Montes, D.; Caballero, J. A.;
Lázaro, F. J.; González Hernández, J. I.; Nagel, E.; Passegger,
V. M.; Schweitzer, A.; Ribas, I.; Reiners, A.; Quirrenbach, A.;
Amado, P. J.; Cifuentes, C.; Cortés-Contreras, M.; Dreizler, S.;
Duque-Arribas, C.; Galadí-Enríquez, D.; Henning, Th.; Jeffers,
S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; López-Gallifa, Á.;
Morales, J. C.; Shan, Y.; Zechmeister, M.
Bibcode: 2021A&A...656A.162M
Altcode: 2021arXiv211007329M
We determined effective temperatures, surface gravities, and
metallicities for a sample of 343 M dwarfs observed with CARMENES,
the double-channel, high-resolution spectrograph installed at the
3.5 m telescope at Calar Alto Observatory. We employed SteParSyn,
a Bayesian spectral synthesis implementation particularly designed to
infer the stellar atmospheric parameters of late-type stars following
a Markov chain Monte Carlo approach. We made use of the BT-Settl model
atmospheres and the radiative transfer code turbospectrum to compute a
grid of synthetic spectra around 75 magnetically insensitive Fe I and Ti
I lines plus the TiO γ and ϵ bands. To avoid any potential degeneracy
in the parameter space, we imposed Bayesian priors on Teff
and logg based on the comprehensive, multi-band photometric data
available for the sample. We find that this methodology is suitable down
to M7.0 V, where refractory metals such as Ti are expected to condense
in the stellar photospheres. The derived Teff, logg, and
[Fe/H] range from 3000 to 4200 K, 4.5 to 5.3 dex, and −0.7 to 0.2
dex, respectively. Although our Teff scale is in good
agreement with the literature, we report large discrepancies in the
[Fe/H] scales, which might arise from the different methodologies and
sets of lines considered. However, our [Fe/H] is in agreement with the
metallicity distribution of FGK-type stars in the solar neighbourhood
and correlates well with the kinematic membership of the targets in the
Galactic populations. Lastly, excellent agreement in Teff is
found for M dwarfs with interferometric angular diameter measurements,
as well as in the [Fe/H] between the components in the wide physical
FGK+M and M+M systems included in our sample. Full Tables
B.1-B.3 are only 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/656/A162
Title: Evolution of brightness and magnetic features of young
solar-type stars - I. The young G star HIP 89829
Authors: Perugini, G. M.; Marsden, S. C.; Waite, I. A.; Jeffers,
S. V.; Piskunov, N.; Shaw, N.; Burton, D. M.; Mengel, M. W.; Hughes,
J. E.; Hébrard, E. M.
Bibcode: 2021MNRAS.508.3304P
Altcode: 2021MNRAS.tmp.2515P
The evolution in latitude of sunspots is a key feature of the cyclic
solar dynamo. Here, we present the results of a spectroscopic and
spectropolarimetric monitoring campaign on the young (~20 Myr old)
early G star HIP 89829, in order to investigate potential evolution
in the distribution of the star's spots and magnetic features. Our
analysis of this G5V star spans eight epochs, from June 2010 to August
2015. The techniques of Doppler imaging and Zeeman-Doppler imaging were
used to create brightness maps for each epoch and magnetic maps for
two epochs. The brightness images show the star to have stable spot
features with two main spot latitudes - a polar spot, often seen on
young rapidly rotating stars such as this, and another highly unusual
group of large spot features around the 20° and 30° latitudes. These
lower spot latitudes appear to be rather stable over the 5 yr of
observations. We included a solar-type differential rotation law into
the imaging process and measured near-solid-body rotation for epochs
where sufficient data exist for this analysis. The magnetic features
show a dominant poloidal and a weaker toroidal magnetic field for both
Stokes V epochs, which is unusual for a star with a rapid rotation
period of 0.57 d. We conclude that HIP 89829 is an active young
solar-type star with long-lived spots and near-solid-body rotation.
Title: VizieR Online Data Catalog: ZDI maps of five young solar-type
stars (Willamo+, 2022)
Authors: Willamo, T.; Lehtinen, J. J.; Hackman, T.; Kapyla, M. J.;
Kochukhov, O.; Jeffers, S. V.; Korhonen, H.; Marsden, S. C.
Bibcode: 2021yCat..36590071W
Altcode:
We present Zeeman-Doppler imaging (ZDI) maps, containing surface maps
of the radial, meridional and azimuthal components of the magnetic
field, and the brightness of BE Cet, {chi}1 Ori, HD 29615,
HD 35296 and V1358 Ori. The epoch for the maps is December 2017. For
V1358 Ori we publish also one ZDI map from an earlier epoch, September
2013, which is specified in the filename. (7 data files).
Title: VizieR Online Data Catalog: KI diagnostic capabilities for
M dwarfs (Fuhrmeister+, 2022)
Authors: Fuhrmeister, B.; Czesla, S.; Nagel, E.; Reiners, A.; Schmitt,
J. H. M. M.; Jeffers, S. V.; Caballero, J. A.; Shulyak, D.; Johnson,
E. N.; Zechmeister, M.; Montes, D.; Lopez-Gallifa, A.; Ribas, I.;
Quirrenbach, A.; Amado, P. J.; Galadi-Enriquez, D.; Hatzes, A. P.;
Kuerster, M.; Danielski, C.; Bejar, V. J. S.; Kaminski, A.; Morales,
J. C.; Zapatero Osorio, M. R.
Bibcode: 2021yCat..36570125F
Altcode:
We measure the pseudo-equivalent width for pEW) of the KI doublet lines
in each stellar spectrum. The integration ranges for the lines and
the reference bands are found in Table 1 of the paper. For comparison
purposes we also measure pEW values of Halpha. From these measurements
we compute the mean pEW, the median absolute deviation (MAD) and
Pearson's correlation coefficients for the lines. (1 data file).
Title: VizieR Online Data Catalog: CARMENES stellar atmospheric
parameters (Marfil+, 2021)
Authors: Marfil, E.; Tabernero, H. M.; Montes, D.; Caballero, J. A.;
Lazaro, F. J.; Gonzalez Hernandez, J. I.; Nagel, E.; Passegger, V. M.;
Schweitzer, A.; Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.;
Cifuentes, C.; Cortes-Contreras, M.; Dreizler, S.; Duque-Arribas,
C.; Galadi-Enriquez, D.; Henning, T.; Jeffers, S. V.; Kaminski, A.;
Kurster, M.; Lafarga, M.; Lopez-Gallifa, A.; Morales, J. C.; Shan,
Y.; Zechmeister, M.
Bibcode: 2021yCat..36560162M
Altcode:
We present basic information of investigated M dwarfs, atomic data of
the selected TiI and FeI lines, wavelength ranges synthesised, and
the stellar atmospheric parameters (effective temperatures, surface
gravities, and metallicities) derived for the sample with SteParSyn. (3 data files).
Title: CARMENES and the Frontiers of High-Resolution Spectroscopy
for M dwarfs
Authors: Shan, Yutong; Reiners, Ansgar; Amado, Pedro J.; Béjar, Victor
J. S.; Caballero, Jose A.; Cifuentes, Carlos; Cortés-Contreras,
Miriam; Jeffers, Sandra V.; Marfil, Emilio; Montes, David; Nagel,
Evangelos; Passegger, Vera M.; Quirrenbach, Andreas; Ribas, Ignasi;
Schweitzer, Andreas; Tabernero, Hugo M.; Zechmeister, Mathias;
Carmenes Consortium
Bibcode: 2021plat.confE..93S
Altcode:
Comprehensive understanding of planets is predicated on detailed
descriptions of their parent stars. M dwarfs are prolific hosts
of planetary systems and form an important sample for the PLATO
mission. The prospect for characterizing M dwarfs to a level comparable
with Sun-like stars is bright, thanks to recent improvements in
atmosphere models and the growing availability of high-resolution
spectroscopic data. The CARMENES survey has produced high-quality,
R~90,000, multi-epoch spectra in the optical and NIR for hundreds of
nearby early- to late-M dwarfs. These spectra have been accurately
telluric-corrected and co-added to very high signal-to-noise, making
them suitable for identifying and modeling fine features intrinsic to
the star. The wavelength coverage (520 — 1710 nm) of the CARMENES
spectrograph is one of the widest in the industry and contains a large
variety of lines and features. Their resolved profiles are sensitive
to temperature, metallicity, elemental abundances, and exhibit
useful quantum effects. We give examples of recent applications
using CARMENES spectra to measure fundamental stellar parameters
and chemical compositions of M dwarf photospheres. We summarize how
lessons from CARMENES spectroscopy of cool dwarfs could inform target
selection and characterization efforts from ground-based facilities
for PLATO. (Contributed talk to PLATO mission conference, Oct 2021)
Title: Mapping magnetic activity indicators across the M dwarf domain
Authors: Lafarga, Marina; Ribas, Ignasi; Reiners, Ansgar; Quirrenbach,
Andreas; Amado, Pedro J.; Caballero, Jose A.; Azzaro, Marco;
Béjar, Víctor J. S.; Cortés-Contreras, Miriam; Dreizler, Stefan;
Hatzes, Artie P.; Henning, Thomas; Jeffers, Sandra V.; Kaminski,
A.; Kürster, Martin; Montes, David; Morales, Juan Carlos; Oshagh,
Mahmoud; Rodríguez-López, Cristina; Schöfer, Patrick; Schweitzer,
Andreas; Zechmeister, Mathias
Bibcode: 2021spc..confE...7L
Altcode:
Stellar activity poses one of the main obstacles for the detection and
characterisation of exoplanets around cool stars, as it can induce
radial velocity (RV) signals that can hide or mimic the presence of
companions. Several activity indicators are routinely used to identify
activity-related signals in RV measurements, but not all indicators
trace exactly the same effects, nor are any of them always effective
in all stars. In this work, we evaluate the performance of a set of
common spectroscopic activity indicators for 98 M dwarfs observed
with CARMENES. We find that different indicators behave differently
depending on the mass and activity level of the target star. In
addition, we also observe that stars at the low-mass end of the
sample show the lowest RV scatter, which could potentially hint at
different manifestations of activity compared to higher-mass stars,
as well as being better candidates for planet searches. Overall, our
results show that when assessing the origin of an RV signal, it is
critical to take into account a large set of indicators, or at least
the most effective ones considering the characteristics of the star,
as failing to do so may lead to false planet claims.
Title: The CARMENES search for exoplanets around M dwarfs. Not-so-fine
hyperfine-split vanadium lines in cool star spectra
Authors: Shan, Y.; Reiners, A.; Fabbian, D.; Marfil, E.; Montes,
D.; Tabernero, H. M.; Ribas, I.; Caballero, J. A.; Quirrenbach, A.;
Amado, P. J.; Aceituno, J.; Béjar, V. J. S.; Cortés-Contreras, M.;
Dreizler, S.; Hatzes, A. P.; Henning, Th.; Jeffers, S. V.; Kaminski,
A.; Kürster, M.; Lafarga, M.; Morales, J. C.; Nagel, E.; Pallé, E.;
Passegger, V. M.; Rodriguez-López, C.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2021A&A...654A.118S
Altcode: 2021arXiv210812442S
Context. M-dwarf spectra are complex and notoriously difficult to model,
posing challenges to understanding their photospheric properties and
compositions in depth. Vanadium (V) is an iron-group element whose
abundance supposedly closely tracks that of iron, but has origins that
are not completely understood.
Aims: Our aim is to characterize
a series of neutral vanadium atomic absorption lines in the 800-910
nm wavelength region of high signal-to-noise, high-resolution,
telluric-corrected M-dwarf spectra from the CARMENES survey. Many
of these lines are prominent and exhibit a distinctive broad and
flat-bottom shape, which is a result of hyperfine structure (HFS). We
investigate the potential and implications of these HFS split lines
for abundance analysis of cool stars.
Methods: With standard
spectral synthesis routines, as provided by the spectroscopy software
iSpec and the latest atomic data (including HFS) available from the
VALD3 database, we modeled these striking line profiles. We used them
to measure V abundances of cool dwarfs.
Results: We determined
V abundances for 135 early M dwarfs (M0.0 V to M3.5 V) in the CARMENES
guaranteed time observations sample. They exhibit a [V/Fe]-[Fe/H]
trend consistent with that derived from nearby FG dwarfs. The tight
(±0.1 dex) correlation between [V/H] and [Fe/H] suggests the potential
application of V as an alternative metallicity indicator in M dwarfs. We
also show hints that neglecting to model HFS could partially explain
the temperature correlation in V abundance measurements observed in
previous studies of samples involving dwarf stars with Teff
≲ 5300 K.
Conclusions: Our work suggests that HFS can impact
certain absorption lines in cool photospheres more severely than in
Sun-like ones. Therefore, we advocate that HFS should be carefully
treated in abundance studies in stars cooler than ~5000 K. On the other
hand, strong HFS split lines in high-resolution spectra present an
opportunity for precision chemical analyses of large samples of cool
stars. The V-to-Fe trends exhibited by the local M dwarfs continue
to challenge theoretical models of V production in the Galaxy. Full Table A.1 is only 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/654/A118
Title: Convective blueshift strengths of 810 F to M solar-type stars
Authors: Liebing, F.; Jeffers, S. V.; Reiners, A.; Zechmeister, M.
Bibcode: 2021A&A...654A.168L
Altcode: 2021arXiv210803859L
Context. The detection of Earth-mass exoplanets in the habitable zone
around solar-mass stars using the radial velocity technique requires
extremely high precision, on the order of 10 cm s−1. This
puts the required noise floor below the intrinsic variability of
even relatively inactive stars, such as the Sun. One such variable
is convective blueshift varying temporally, spatially, and between
spectral lines.
Aims: We develop a new approach for measuring
convective blueshift and determine the strength of convective blueshift
for 810 stars observed by the HARPS spectrograph, spanning spectral
types late-F, G, K, and early-M. We derive a model for infering
blueshift velocity for lines of any depth in later-type stars of
any effective temperature.
Methods: Using a custom list of
spectral lines, covering a wide range of absorption depths, we create
a model for the line-core shift as a function of line depth, commonly
known as the third signature of granulation. For this we utilize an
extremely-high-resolution solar spectrum (R ~ 1 000 000) to empirically
account for the nonlinear nature of the third signature. The solar
third signature is then scaled to all 810 stars. Through this we
obtain a measure of the convective blueshift relative to the Sun
as a function of stellar effective temperature.
Results: We
confirm the general correlation of increasing convective blueshift with
effective temperature and establish a tight, cubic relation between the
two that strongly increases for stars above ~5800 K. For stars between
~4100 and ~4700 K we show, for the first time, a plateau in convective
shift and a possible onset of a plateau for stars above 6000 K. Stars
below ~4000 K show neither blueshift nor redshift. We provide a table
that lists expected blueshift velocities for each spectral subtype
in the data set to quickly access the intrinsic noise floor through
convective blueshift for the radial velocity technique. Full
Table E.2 is only 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/654/A168
Title: A young spectroscopic binary in a quintuple system part of
the Local Association
Authors: Cardona Guillén, Carlos; Lodieu, Nicolas; Béjar, Víctor
J. S.; Baroch, David; Montes, David; Hoskin, Matthew J.; Jeffers,
Sandra V.; Murgas, Felipe; Tremblay, Pier-Emmanuel; Schöfer, Patrick;
Harbeck, Daniel; McCully, Curtis
Bibcode: 2021A&A...654A.134C
Altcode: 2021arXiv210901624C
Context. Double-lined spectroscopic (SB2) binaries allow us to obtain
a direct determination of the masses of their components, which is
essential to test stellar models. Although these objects only provide
a lower limit for the mass, they are more abundant than their eclipsing
counterparts as they are not as strongly limited by the inclination of
their orbit.
Aims: Our aim is to derive the orbital and physical
parameters of GJ 1284, a young SB2. We also revise the membership of
this system and its two wide co-moving companions, GJ 898 and GJ 897AB,
to a young moving group to assess, along with other youth indicators,
their age. Afterwards, we compare the results from these analyses
and the photometry of these systems with several pre-main-sequence
evolutionary models.
Methods: We use high-resolution spectra
to determine the radial velocity of each component of GJ 1284 and the
orbit of the system alongside its systemic velocity. Additionally,
we use TESS photometry to derive the rotational period of the GJ 1284
and its two wide companions.
Results: GJ 1284 is a binary
system located at approximately 16 pc with an eccentric orbit (e =
0.505) of 11.83 d period made up of an M2-M2.5 + M3-M3.5 with minimum
masses of M sin 3i = 0.141 ± 0.003 and 0.1189 ± 0.003
M⊙, respectively. The revised systemic velocity of γ =
0.84 ± 0.14 km s−1 suggests that it is a member of the
Local Association. The kinematics together with other activity and
youth indicators imply an age of 110-800 Myr for this system and its
two companions.
Conclusions: The isochronal ages derived from
the comparison of the photometry with several evolutionary models are
younger than the age estimated from the activity indicators for the
three co-moving systems. The masses for the components of GJ 1284,
derived from their luminosity and age using the different models,
are not consistent with the masses derived from the photometry,
except for the PARSEC models, but are compatible with dynamical
masses of double-lined eclipsing binaries with similar ages and
spectral types. The effect of magnetic activity in the form of spots
can reconcile to some extent the photometric and dynamical masses,
but is not considered in most of the evolutionary models.
Title: VizieR Online Data Catalog: TOI-1201 RV and activity index
(Kossakowski+, 2021)
Authors: Kossakowski, D.; Kemmer, J.; Bluhm, P.; Stock, S.; Caballero,
J. A.; Bejar, V. J. S.; Cardona Guillen, C.; Lodieu, N.; Collins,
K. A.; Oshagh, M.; Schlecker, M.; Espinoza, N.; Palle, E.; Henning,
Th.; Kreidberg, L.; Kuerster, M.; Amado, P. J.; Anderson, D. R.;
Morales, J. C.; Cartwright, S.; Charbonneau, D.; Chaturvedi, P.;
Cifuentes, C.; Conti, D. M.; Cortes-Contreras, M.; Dreizler, S.;
Galadi-Enriquez, D.; Guerra, P.; Hart, R.; Hellier, C.; Henze,
C.; Herrero, E.; Jeffers, S. V.; Jenkins, J. M.; Jensen, E. L. N.;
Kaminski, A.; Kielkopf, J. F.; Kunimoto, M.; Lafarga, M.; Latham,
D. W.; Lillo-Box, J.; Luque, R.; Molvaerdikhani, K.; Montes, D.;
Morello, G.; Morgan, E. H.; Nowak, G.; Pavlov, A.; Perger, M.;
Quintana, E. V.; Quirrenbach, A.; Reffert, S.; Reiners, A.; Ricker,
G.; Ribas, I.; Rodriguez Lopez, C.; Zapatero Osorio, M. R.; Seager,
S.; Schoefer, P.; Schweitzer, A.; Trifonov, T.; Vanaverbeke, S.;
Vanderspek, R.; West, R.; Winn, J.; Zechmeister, M.
Bibcode: 2021yCat..36560124K
Altcode:
High-resolution spectroscopy taken with the CARMENES VIS instrument
for the two M dwarfs in a binary system, TOI-1201 and its companion
(PM J02489-1432E). Likewise, the stellar activity indicators are output
from the SERVAL pipeline (Zechmeister et al. 2018A&A...609A..12Z),
namely, this entails the chromatic index (CRX), the differential line
width (dLW), the Halpha index, the Calcium triplet lines (CAIRT). The
photospheric TiO absorption band indices (at 7050Å, 8430Å, and 8860Å)
following Schoefer et al. (2019A&A...623A..44S, Cat. J/A+A/623/A44)
are included. Also, the cross-correlation function parameters,
as provided following Lafarga et al. (2020A&A...636A..36L,
Cat. J/A+A/636/A36), are included and these are: bisector velocity span
(BVS), contrast (CTR), and full width at half maximum (FWHM). Most
observations are simultaneously, however there are 33 data points for
TOI-1201 (Nov. 2019 - Feb. 2020) and 23 for PM J02489-1432E (Nov. 2019 -
Jan. 2020). (2 data files).
Title: The CARMENES search for exoplanets around M
dwarfs. Spectroscopic orbits of nine M-dwarf multiple systems,
including two triples, two brown dwarf candidates, and one close
M-dwarf-white dwarf binary
Authors: Baroch, D.; Morales, J. C.; Ribas, I.; Béjar, V. J. S.;
Reffert, S.; Cardona Guillén, C.; Reiners, A.; Caballero, J. A.;
Quirrenbach, A.; Amado, P. J.; Anglada-Escudé, G.; Colomé, J.;
Cortés-Contreras, M.; Dreizler, S.; Galadí-Enríquez, D.; Hatzes,
A. P.; Jeffers, S. V.; Henning, Th.; Herrero, E.; Kaminski, A.;
Kürster, M.; Lafarga, M.; Lodieu, N.; López-González, M. J.;
Montes, D.; Pallé, E.; Perger, M.; Pollacco, D.; Rodríguez-López,
C.; Rodríguez, E.; Rosich, A.; Schöfer, P.; Schweitzer, A.; Shan,
Y.; Tal-Or, L.; Zechmeister, M.
Bibcode: 2021A&A...653A..49B
Altcode: 2021arXiv210514770B
Context. M dwarfs are ideal targets for the search of Earth-size
planets in the habitable zone using the radial velocity method,
and are attracting the attention of many ongoing surveys. One of the
expected results of these surveys is that new multiple-star systems
have also been found. This is the case also for the CARMENES survey,
thanks to which nine new double-line spectroscopic binary systems have
already been announced.
Aims: Throughout the five years of
the survey the accumulation of new observations has resulted in the
detection of several new multiple-stellar systems with long periods
and low radial-velocity amplitudes. Here we newly characterise the
spectroscopic orbits and constrain the masses of eight systems and
update the properties of a system that we had reported earlier.
Methods: We derived the radial velocities of the stars using
two-dimensional cross-correlation techniques and template matching. The
measurements were modelled to determine the orbital parameters of the
systems. We combined CARMENES spectroscopic observations with archival
high-resolution spectra from other instruments to increase the time
span of the observations and improve our analysis. When available,
we also added archival photometric, astrometric, and adaptive optics
imaging data to constrain the rotation periods and absolute masses
of the components.
Results: We determined the spectroscopic
orbits of nine multiple systems, eight of which are presented for
the first time. The sample is composed of five single-line binaries,
two double-line binaries, and two triple-line spectroscopic triple
systems. The companions of two of the single-line binaries, GJ 3626 and
GJ 912, have minimum masses below the stellar boundary, and thus could
be brown dwarfs. We found a new white dwarf in a close binary orbit
around the M star GJ 207.1, located at a distance of 15.79 pc. From a
global fit to radial velocities and astrometric measurements, we were
able to determine the absolute masses of the components of GJ 282 C,
which is one of the youngest systems with measured dynamical masses.
Title: The CARMENES search for exoplanets around M dwarfs. Planet
occurrence rates from a subsample of 71 stars
Authors: Sabotta, S.; Schlecker, M.; Chaturvedi, P.; Guenther,
E. W.; Muñoz Rodríguez, I.; Muñoz Sánchez, J. C.; Caballero,
J. A.; Shan, Y.; Reffert, S.; Ribas, I.; Reiners, A.; Hatzes, A. P.;
Amado, P. J.; Klahr, H.; Morales, J. C.; Quirrenbach, A.; Henning,
Th.; Dreizler, S.; Pallé, E.; Perger, M.; Azzaro, M.; Jeffers, S. V.;
Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Passegger, V. M.;
Zechmeister, M.
Bibcode: 2021A&A...653A.114S
Altcode: 2021arXiv210703802S
Context. The CARMENES exoplanet survey of M dwarfs has obtained more
than 18 000 spectra of 329 nearby M dwarfs over the past five years as
part of its guaranteed time observations (GTO) program.
Aims:
We determine planet occurrence rates with the 71 stars from the GTO
program for which we have more than 50 observations.
Methods:
We use injection-and-retrieval experiments on the radial-velocity
time series to measure detection probabilities. We include 27
planets in 21 planetary systems in our analysis.
Results:
We find 0.06−0.03+0.04 giant planets (100
M⊕ < Mpl sin i < 1000 M⊕)
per star in periods of up to 1000 d, but due to a selection bias this
number could be up to a factor of five lower in the whole 329-star
sample. The upper limit for hot Jupiters (orbital period of less than
10 d) is 0.03 planets per star, while the occurrence rate of planets
with intermediate masses (10 M⊕ < Mpl sin
i < 100 M⊕) is 0.18−0.05+0.07
planets per star. Less massive planets with 1 M⊕ <
Mpl sin i < 10 M⊕ are very abundant,
with an estimated rate of 1.32−0.31+0.33
planets per star for periods of up to 100 d. When considering only
late M dwarfs with masses M⋆ < 0.34 M⊙,
planets more massive than 10 M⊕ become rare. Instead,
low-mass planets with periods shorter than 10 d are significantly
overabundant.
Conclusions: For orbital periods shorter than
100 d, our results confirm the known stellar mass dependences from
the Kepler survey: M dwarfs host fewer giant planets and at least two
times more planets with Mpl sin i < 10 M⊕
than G-type stars. In contrast to previous results, planets around
our sample of very low-mass stars have a higher occurrence rate in
short-period orbits of less than 10 d. Our results demonstrate the
need to take into account host star masses in planet formation models.
Title: VizieR Online Data Catalog: Vanadium measurements for 135 M
dwarfs (Shan+, 2021)
Authors: Shan, Y.; Reiners, A.; Fabbian, D.; Marfil, E.; Montes,
D.; Tabernero, H. M.; Ribas, I.; Caballero, J. A.; Quirrenbach, A.;
Amado, P. J.; Aceituno, J.; Bejar, V. J. S.; Cortes-Contreras, M.;
Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski,
A.; Kuerster, M.; Lafarga, M.; Morales, J. C.; Nagel, E.; Palle, E.;
Passegger, V. M.; Rodriguez-Lopez, C.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2021yCat..36540118S
Altcode:
Table A1 presents the measured V abundances ([V/H]) for 135
nearby early-M dwarfs from the CARMENES GTO sample. Two sets
of measurements are given, which are based on two independently
measured sets of fundamental stellar parameters for this sample
(Schweitzer et al., 2019A&A...625A..68S, Cat. J/A+A/625/A68 and
Marfil et al., submitted). Rotational velocities from Reiners et
al. (2018A&A...612A..49R, Cat. J/A+A/612/A49) and disk kinematic
membership designations (Cortes-Contreras+ in prep) are also
included. (1 data file).
Title: VizieR Online Data Catalog: Convective blueshifts for
solar-type stars (Liebing+, 2021)
Authors: Liebing, F.; Jeffers, S. V.; Reiners, A.; Zechmeister, M.
Bibcode: 2021yCat..36540168L
Altcode:
We calculated the convective blueshift strength for 810 stars observed
by HARPS relative to a solar template. For each star we provide the
important parameters, details on the coadded spectrum and line-by-line
fit as well as the strength and uncertainty of the solar relative
convection strength. We further provide interpolated results for CBS
strength over a range of spectral types and corresponding RV values
from our model. (2 data files).
Title: The CARMENES search for exoplanets around M dwarfs. Mapping
stellar activity indicators across the M dwarf domain
Authors: Lafarga, M.; Ribas, I.; Reiners, A.; Quirrenbach, A.;
Amado, P. J.; Caballero, J. A.; Azzaro, M.; Béjar, V. J. S.;
Cortés-Contreras, M.; Dreizler, S.; Hatzes, A. P.; Henning, Th.;
Jeffers, S. V.; Kaminski, A.; Kürster, M.; Montes, D.; Morales,
J. C.; Oshagh, M.; Rodríguez-López, C.; Schöfer, P.; Schweitzer,
A.; Zechmeister, M.
Bibcode: 2021A&A...652A..28L
Altcode: 2021arXiv210513467L
Context. Stellar activity poses one of the main obstacles for the
detection and characterisation of small exoplanets around cool stars,
as it can induce radial velocity (RV) signals that can hide or mimic
the presence of planetary companions. Several indicators of stellar
activity are routinely used to identify activity-related signals in
RVs, but not all indicators trace exactly the same activity effects,
nor are any of them always effective in all stars.
Aims:
We evaluate the performance of a set of spectroscopic activity
indicators for M dwarf stars with different masses and activity
levels with the aim of finding a relation between the indicators
and stellar properties.
Methods: In a sample of 98 M dwarfs
observed with CARMENES, we analyse the temporal behaviour of RVs and
nine spectroscopic activity indicators: cross-correlation function
(CCF) full-width-at-half-maximum (FWHM), CCF contrast, CCF bisector
inverse slope (BIS), RV chromatic index (CRX), differential line width
(dLW), and indices of the chromospheric lines Hα and calcium infrared
triplet.
Results: A total of 56 stars of the initial sample
show periodic signals related to activity in at least one of these
ten parameters. RV is the parameter for which most of the targets
show an activity-related signal. CRX and BIS are effective activity
tracers for the most active stars in the sample, especially stars with
a relatively high mass, while for less active stars, chromospheric
lines perform best. FWHM and dLW show a similar behaviour in all mass
and activity regimes, with the highest number of activity detections
in the low-mass, high-activity regime. Most of the targets for which
we cannot identify any activity-related signals are stars at the
low-mass end of the sample (i.e. with the latest spectral types). These
low-mass stars also show the lowest RV scatter, which indicates that
ultracool M dwarfs could be better candidates for planet searches
than earlier types, which show larger RV jitter.
Conclusions:
Our results show that the spectroscopic activity indicators analysed
behave differently, depending on the mass and activity level of the
target star. This underlines the importance of considering different
indicators of stellar activity when studying the variability of RV
measurements. Therefore, when assessing the origin of an RV signal,
it is critical to take into account a large set of indicators, or at
least the most effective ones considering the characteristics of the
star, as failing to do so may lead to false planet claims. Full
Table A.1 is only 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/652/A28
Title: CARMENES input catalog of M dwarfs. VI. A time-resolved Ca
II H&K catalog from archival data
Authors: Perdelwitz, V.; Mittag, M.; Tal-Or, L.; Schmitt, J. H. M. M.;
Caballero, J. A.; Jeffers, S. V.; Reiners, A.; Schweitzer, A.;
Trifonov, T.; Ribas, I.; Quirrenbach, A.; Amado, P. J.; Seifert,
W.; Cifuentes, C.; Cortés-Contreras, M.; Montes, D.; Revilla, D.;
Skrzypinski, S. L.
Bibcode: 2021A&A...652A.116P
Altcode: 2021arXiv210706376P
Context. Radial-velocity (RV) jitter caused by stellar magnetic
activity is an important factor in state-of-the-art exoplanet
discovery surveys such as CARMENES. Stellar rotation, along with
heterogeneities in the photosphere and chromosphere caused by
activity, can result in false-positive planet detections. Hence,
it is necessary to determine the stellar rotation period and compare
it to any putative planetary RV signature. Long-term measurements of
activity indicators such as the chromospheric emission in the Ca II
H&K lines (RHK') enable the identification of
magnetic activity cycles.
Aims: In order to determine stellar
rotation periods and study the long-term behavior of magnetic activity
of the CARMENES guaranteed time observations (GTO) sample, it is
advantageous to extract RHK' time series from
archival data, since the CARMENES spectrograph does not cover the blue
range of the stellar spectrum containing the Ca II H&K lines.
Methods: We have assembled a catalog of 11 634 archival spectra
of 186 M dwarfs acquired by seven different instruments covering
the Ca II H&K regime: ESPaDOnS, FEROS, HARPS, HIRES, NARVAL,
TIGRE, and UVES. The relative chromospheric flux in these lines,
RHK', was directly extracted from the spectra
by rectification with PHOENIX synthetic spectra via narrow passbands
around the Ca II H&K line cores.
Results: The combination
of archival spectra from various instruments results in time series
for 186 stars from the CARMENES GTO sample. As an example of the use
of the catalog, we report the tentative discovery of three previously
unknown activity cycles of M dwarfs.
Conclusions: We conclude
that the method of extracting RHK^\prime with the use of
model spectra yields consistent results for different instruments
and that the compilation of this catalog will enable the analysis
of long-term activity time series for a large number of M dwarfs. Full Table 3 is only 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/652/A116
Title: VizieR Online Data Catalog: CARMENES time-resolved CaII
H&K catalog (Perdelwitz+, 2021)
Authors: Perdelwitz, V.; Mittag, M.; Tal-Or, L.; Schmitt, J. H. M. M.;
Caballero, J. A.; Jeffers, S. V.; Reiners, A.; Schweitzer, A.;
Trifonov, T.; Ribas, I.; Quirrenbach, A.; Amado, P. J.; Seifert,
W.; Cifuentes, C.; Cortes-Contreras, M.; Montes, D.; Revilla, D.;
Skrzypinski, S. L.
Bibcode: 2021yCat..36520116P
Altcode:
The time-resolved catalog is based on pipeline-reduced spectra
from seven different spectrographs: ESPADONS (Donati et
al., 1997MNRAS.291..658D; Petit et al., 2014PASP..126..469P,
Cat. J/PASP/126/469) FEROS (Kaufer et al., 1999Msngr..95....8K)
HARPS (Mayor et al., 2003Msngr.114...20M) HIRES (Vogt et al. 1994, in
Society of Photo-Optical Instrumentation Engineers (SPIE) Conference
Series, Vol. 2198, Instrumentation in Astronomy VIII, 362; Vogt 2002,
in Astronomical Society of the Pacific Conference Series, Vol. 270,
Astronomical Instrumentation and Astrophysics, 5) NARVAL (Petit et
al., 2014PASP..126..469P, Cat. J/PASP/126/469; Donati et al. 2006,
in Astronomical Society of the Pacific Conference Series, Vol. 358,
Solar Polarization 4, 362) TIGRE (Schmitt et al., 2004ANS...325...27W)
UVES (Dekker et al. 2000, in Society of Photo-Optical Instrumentation
Engineers (SPIE) Conference Series, Vol. 4008, Optical and IR Telescope
Instrumentation and Detectors, 534-545) The spectral rectification
and flux calibration is based on PHOENIX model atmospheres (Husser et
al., 2013A&A...553A...6H). (2 data files).
Title: Simultaneous photometric and CARMENES spectroscopic monitoring
of fast-rotating M dwarf GJ 3270. Discovery of a post-flare corotating
feature
Authors: Johnson, E. N.; Czesla, S.; Fuhrmeister, B.; Schöfer, P.;
Shan, Y.; Cardona Guillén, C.; Reiners, A.; Jeffers, S. V.; Lalitha,
S.; Luque, R.; Rodríguez, E.; Béjar, V. J. S.; Caballero, J. A.;
Tal-Or, L.; Zechmeister, M.; Ribas, I.; Amado, P. J.; Quirrenbach,
A.; Cortés-Contreras, M.; Dreizler, S.; Fukui, A.; López-González,
M. J.; Hatzes, A. P.; Henning, Th.; Kaminski, A.; Kürster, M.;
Lafarga, M.; Montes, D.; Morales, J. C.; Murgas, F.; Narita, N.;
Pallé, E.; Parviainen, H.; Pedraz, S.; Pollacco, D.; Sota, A.
Bibcode: 2021A&A...651A.105J
Altcode: 2021arXiv210407080J
Context. Active M dwarfs frequently exhibit large flares, which can
pose an existential threat to the habitability of any planet in orbit
in addition to making said planets more difficult to detect. M dwarfs
do not lose angular momentum as easily as earlier-type stars, which
maintain the high levels of stellar activity for far longer. Studying
young, fast-rotating M dwarfs is key to understanding their near
stellar environment and the evolution of activity.
Aims: We
study stellar activity on the fast-rotating M dwarf GJ 3270.
Methods: We analyzed dedicated high cadence, simultaneous, photometric
and high-resolution spectroscopic observations obtained with CARMENES of
GJ 3270 over 7.7 h, covering a total of eight flares of which two are
strong enough to facilitate a detailed analysis. We consult the TESS
data, obtained in the month prior to our own observations, to study
rotational modulation and to compare the TESS flares to those observed
in our campaign.
Results: The TESS data exhibit rotational
modulation with a period of 0.37 d. The strongest flare covered
by our observing campaign released a total energy of about 3.6 ×
1032 erg, putting it close to the superflare regime. This
flare is visible in the B,V, r, i, and z photometric bands, which
allows us to determine a peak temperature of about 10 000 K. The flare
also leaves clear marks in the spectral time series. In particular,
we observe an evolving, mainly blue asymmetry in chromospheric lines,
which we attribute to a post-flare, corotating feature. To our knowledge
this is the first time such a feature has been seen on a star other
than our Sun.
Conclusions: Our photometric and spectroscopic
time series covers the eruption of a strong flare followed up by a
corotating feature analogous to a post-flare arcadal loop on the Sun
with a possible failed ejection of material.
Title: VizieR Online Data Catalog: Activity indicators across the
M dwarf domain (Lafarga+, 2021)
Authors: Lafarga, M.; Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado,
P. J.; Caballero, J. A.; Azzaro, M.; Bejar, V. J. S.; Cortes-Contreras,
M.; Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.;
Kaminski, A.; Kuerster, M.; Montes, D.; Morales, J. C.; Oshagh, M.;
Rodriguez-Lopez, C.; Schoefer, P.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2021yCat..36520028L
Altcode:
Properties of the 98 sample stars. Values taken from the latest
version of the Carmencita database available at the time. We also
show the number of CARMENES VIS observations (before performing any
sigma-clipping or discarding any observations due to low S/N), the
number of different nights covered by the observations, their time span,
and their RV scatter, measured as the standard deviation (std) of the
corrected serval RVs (instrumental drift and nightly average corrected,
averaged same-night observations, and linear trend removed). (1
data file).
Title: An ultra-short-period transiting super-Earth orbiting the M3
dwarf TOI-1685
Authors: Bluhm, P.; Pallé, E.; Molaverdikhani, K.; Kemmer, J.; Hatzes,
A. P.; Kossakowski, D.; Stock, S.; Caballero, J. A.; Lillo-Box, J.;
Béjar, V. J. S.; Soto, M. G.; Amado, P. J.; Brown, P.; Cadieux, C.;
Cloutier, R.; Collins, K. A.; Collins, K. I.; Cortés-Contreras, M.;
Doyon, R.; Dreizler, S.; Espinoza, N.; Fukui, A.; González-Álvarez,
E.; Henning, Th.; Horne, K.; Jeffers, S. V.; Jenkins, J. M.; Jensen,
E. L. N.; Kaminski, A.; Kielkopf, J. F.; Kusakabe, N.; Kürster, M.;
Lafrenière, D.; Luque, R.; Murgas, F.; Montes, D.; Morales, J. C.;
Narita, N.; Passegger, V. M.; Quirrenbach, A.; Schöfer, P.; Reffert,
S.; Reiners, A.; Ribas, I.; Ricker, G. R.; Seager, S.; Schweitzer,
A.; Schwarz, R. P.; Tamura, M.; Trifonov, T.; Vanderspek, R.; Winn,
J.; Zechmeister, M.; Zapatero Osorio, M. R.
Bibcode: 2021A&A...650A..78B
Altcode: 2021arXiv210301016B
Dynamical histories of planetary systems, as well as the atmospheric
evolution of highly irradiated planets, can be studied by characterizing
the ultra-short-period planet population, which the TESS mission is
particularly well suited to discover. Here, we report on the follow-up
of a transit signal detected in the TESS sector 19 photometric time
series of the M3.0 V star TOI-1685 (2MASS J04342248+4302148). We confirm
the planetary nature of the transit signal, which has a period of
Pb = 0.6691403−0.0000021+0.0000023
d, using precise radial velocity measurements taken with the CARMENES
spectrograph. From the joint photometry and radial velocity analysis,
we estimate the following parameters for TOI-1685 b: a mass of
Mb = 3.78−0.63+0.63 M⊕,
a radius of Rb = 1.70−0.07+0.07
R⊕, which together result in a bulk density
of ρb = 4.21−0.82+0.95 g
cm−3, and an equilibrium temperature of Teq
= 1069−16+16 K. TOI-1685 b is the least dense
ultra-short-period planet around an M dwarf known to date. TOI-1685 b
is also one of the hottest transiting super-Earth planets with accurate
dynamical mass measurements, which makes it a particularly attractive
target for thermal emission spectroscopy. Additionally, we report with
moderate evidence an additional non-transiting planet candidate in the
system, TOI-1685 [c], which has an orbital period of Pc =
9.02−0.12+0.10 d.
Title: The CARMENES search for exoplanets around M dwarfs. Two
terrestrial planets orbiting G 264-012 and one terrestrial planet
orbiting Gl 393
Authors: Amado, P. J.; Bauer, F. F.; Rodríguez López, C.;
Rodríguez, E.; Cardona Guillén, C.; Perger, M.; Caballero, J. A.;
López-González, M. J.; Muñoz Rodríguez, I.; Pozuelos, F. J.;
Sánchez-Rivero, A.; Schlecker, M.; Quirrenbach, A.; Ribas, I.;
Reiners, A.; Almenara, J.; Astudillo-Defru, N.; Azzaro, M.; Béjar,
V. J. S.; Bohemann, R.; Bonfils, X.; Bouchy, F.; Cifuentes, C.;
Cortés-Contreras, M.; Delfosse, X.; Dreizler, S.; Forveille, T.;
Hatzes, A. P.; Henning, Th.; Jeffers, S. V.; Kaminski, A.; Kürster,
M.; Lafarga, M.; Lodieu, N.; Lovis, C.; Mayor, M.; Montes, D.;
Morales, J. C.; Morales, N.; Murgas, F.; Ortiz, J. L.; Pallé, E.;
Pepe, F.; Perdelwitz, V.; Pollaco, D.; Santos, N. C.; Schöfer, P.;
Schweitzer, A.; Ségransan, N. C.; Shan, Y.; Stock, S.; Tal-Or, L.;
Udry, S.; Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2021A&A...650A.188A
Altcode: 2021arXiv210513785A
We report the discovery of two planetary systems, namely G 264-012,
an M 4.0 dwarf with two terrestrial planets (Mb
sin i=2.50−0.30+0.29 M⊕
and Mc sin i=3.75−0.47+0.48
M⊕), and Gl 393, a bright M 2.0 dwarf with one terrestrial
planet (Mb sini = 1.71 ± 0.24M⊕). Although both
stars were proposed to belong to young stellar kinematic groups, we
estimate their ages to be older than about 700 Ma. The two planets
around G 264-012 were discovered using only radial-velocity (RV)
data from the CARMENES exoplanet survey, with estimated orbital
periods of 2.30 d and 8.05 d, respectively.Photometric monitoring and
analysis of activity indicators reveal a third signal present in the RV
measurements, at about 100 d,caused by stellar rotation. The planet
Gl 393 b was discovered in the RV data from the HARPS, CARMENES,
and HIRES instruments. Its identification was only possible after
modelling, with a Gaussian process (GP), the variability produced by
the magnetic activity of the star. For the earliest observations,
this variability produced a forest of peaks in the periodogram of
the RVs at around the 34 d rotation period determined from Kepler
data, which disappeared in the latestepochs. After correcting for
them with this GP model, a significant signal showed at a period
of 7.03 d. No significant signals in any of our spectral activity
indicators or contemporaneous photometry were found at any of the
planetary periods. Given the orbital and stellar properties, the
equilibrium temperatures of the three planets are all higher than that
for Earth. Current planet formation theories suggest that these two
systems represent a common type of architecture. This is consistent
with formation following the core accretion paradigm. Full Tables
B.1 and B.2 are only 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/650/A188
Title: VizieR Online Data Catalog: G 264-012 and Gl 393 radial
velocity curves (Amado+, 2021)
Authors: Amado, P. J.; Bauer, F. F.; Rodriguez Lopez, C.; Rodriguez,
E.; Cardona Guillen, C.; Perger, M.; Caballero, J. A.; Lopez-Gonzalez,
M. J.; Munoz-Rodriguez, I.; Pozuelos, F. J.; Sanchez-Rivero, A.;
Schlecker, M.; Quirrenbach, A.; Ribas, I.; Reiners, A.; Almenara,
J.; Astudillo-Defru, N.; Azzaro, M.; Bejar, V. J. S.; Bohemann, R.;
Bonfils, X.; Bouchy, F.; Cifuentes, C.; Cortes-Contreras, M.; Delfosse,
X.; Dreizler, S.; Forveille, T.; Hatzes, A. P.; Henning, T.; Jeffers,
S. V.; Kaminski, A.; Kuerster, M.; Lafarga, M.; Lodieu, N.; Lovis, C.;
Mayor, M.; Montes, D.; Morales, J. C.; Morales, N.; Murgas, F.; Ortiz,
J. L.; Palle, E.; Pepe, F.; Perdelwitz, V.; Pollaco, D.; Santos, N. C.;
Schoefer, P.; Schweitzer, A.; Segransan, N. C.; Shan, Y.; Stock, S.;
Tal-Or, L.; Udry, S.; Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2021yCat..36500188A
Altcode:
We tabulate the radial velocity (RV) time series (BJD) of the stars G
264-012 and Gl 393, the error of each RV measurement and the instrument
with which it was acquired. (2 data files).
Title: VizieR Online Data Catalog: GJ 1151 radial velocity curve
(Perger+, 2021)
Authors: Perger, M.; Ribas, I.; Anglada-Escude, G.; Morales, J. C.;
Amado, P. J.; Caballero, J. A.; Quirrenbach, A.; Reiners, A.; Bejar,
V. J. S.; Dreizler, S.; Galadi-Enriquez, D.; Hatzes, A. P.; Henning,
T.; Jeffers, S. V.; Kaminski, A.; Kuerster, M.; Lafarga, M.; Montes,
D.; Palle, E.; Rodriguez-Lopez, C.; Schweitzer, A.; Zapatero Osorio,
M. R.; Zechmeister, M.
Bibcode: 2021yCat..36499012P
Altcode:
CARMENES serval (CAR) and HARPS-N terra (HAN) radial velocities of GJ
1151. (1 data file).
Title: The CARMENES search for exoplanets around M dwarfs. No evidence
for a super-Earth in a 2-day orbit around GJ 1151
Authors: Perger, M.; Ribas, I.; Anglada-Escudé, G.; Morales, J. C.;
Amado, P. J.; Caballero, J. A.; Quirrenbach, A.; Reiners, A.; Béjar,
V. J. S.; Dreizler, S.; Galadí-Enríquez, D.; Hatzes, A. P.; Henning,
Th.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes,
D.; Pallé, E.; Rodríguez-López, C.; Schweitzer, A.; Zapatero Osorio,
M. R.; Zechmeister, M.
Bibcode: 2021A&A...649L..12P
Altcode: 2021arXiv210310216P
Context. The interaction between Earth-like exoplanets and the magnetic
field of low-mass host stars are considered to produce weak emission
signals at radio frequencies. A study using LOFAR data announced the
detection of radio emission from the mid M-type dwarf GJ 1151 that
could potentially arise from a close-in terrestrial planet. Recently,
the presence of a 2.5-M⊕ planet orbiting GJ 1151 with a
2-day period has been claimed using 69 radial velocities (RVs) from
the HARPS-N and HPF instruments.
Aims: We have obtained 70 new
high-precision RV measurements in the framework of the CARMENES M-dwarf
survey and use these data to confirm the presence of the claimed planet
and to place limits on possible planetary companions in the GJ 1151
system.
Methods: We analysed the periodicities present in the
combined RV data sets from all three instruments and calculated the
detection limits for potential planets in short-period orbits.
Results: We cannot confirm the recently announced candidate
planet and conclude that the 2-day signal in the HARPS-N and HPF
data sets is most probably produced by a long-term RV variability,
possibly arising from an outer planetary companion that has yet to
be constrained. We calculate a 99.9% significance detection limit of
1.50 m s−1 in the RV semi-amplitude, which places upper
limits of 0.7 M⊕ and 1.2 M⊕ on the minimum
masses of potential exoplanets with orbital periods of 1 and 5 days,
respectively. Table A.1 is only 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/649/L12
Title: Field linkage and magnetic helicity density
Authors: Lund, K.; Jardine, M.; Russell, A. J. B.; Donati, J. -F.;
Fares, R.; Folsom, C. P.; Jeffers, S. V.; Marsden, S. C.; Morin, J.;
Petit, P.; See, V.
Bibcode: 2021MNRAS.502.4903L
Altcode: 2021arXiv210211238L; 2021MNRAS.tmp..352L
The helicity of a magnetic field is a fundamental property that is
conserved in ideal MHD. It can be explored in the stellar context
by mapping large-scale magnetic fields across stellar surfaces using
Zeeman-Doppler imaging. A recent study of 51 stars in the mass range
0.1-1.34 M⊙ showed that the photospheric magnetic helicity
density follows a single power law when plotted against the toroidal
field energy, but splits into two branches when plotted against the
poloidal field energy. These two branches divide stars above and below
~0.5 M⊙. We present here a novel method of visualizing the
helicity density in terms of the linkage of the toroidal and poloidal
fields that are mapped across the stellar surface. This approach allows
us to classify the field linkages that provide the helicity density for
stars of different masses and rotation rates. We find that stars on the
lower mass branch tend to have toroidal fields that are non-axisymmetric
and so link through regions of positive and negative poloidal field. A
lower mass star may have the same helicity density as a higher mass
star, despite having a stronger poloidal field. Lower mass stars are
therefore less efficient at generating large-scale helicity.
Title: Multi-instrumental view of magnetic fields and activity of
ɛ Eridani with SPIRou, NARVAL, and TESS
Authors: Petit, P.; Folsom, C. P.; Donati, J. -F.; Yu, L.;
do Nascimento, J. -D.; Jeffers, S. V.; Marsden, S. C.; Morin, J.;
Vidotto, A. A.
Bibcode: 2021A&A...648A..55P
Altcode: 2021arXiv210102643P
Aims: We report on observations of the active K2 dwarf ɛ Eridani
based on contemporaneous SPIRou, NARVAL and TESS data obtained over
two months in late 2018, when the activity of the star was reported
to be in a non-cyclic phase.
Methods: Near-infrared (NIR)
spectropolarimetry was obtained using SPIRou over four nights in
late September, while visible spectropolarimetry was collected with
NARVAL over 20 nights, spread between 18 September and 07 November. We
first recovered the fundamental parameters of the target from both
visible and NIR spectral fitting. The large-scale magnetic field
was investigated from polarimetric data. From unpolarized spectra,
we estimated the total magnetic flux through Zeeman broadening of
magnetically sensitive NIR lines and the chromospheric emission using
the CaII H&K lines. The photometric monitoring, secured with TESS
between 19 October and 15 November, is modelled with pseudo-periodic
Gaussian process regression.
Results: Fundamental parameters
of ɛ Eridani derived from visible and NIR wavelengths provide us
with consistent results, which also agree with published values. We
report a progressive increase of macroturbulence towards larger NIR
wavelengths. Zeeman broadening of individual lines highlights an
unsigned surface magnetic field Bmono = 1.90 ± 0.13 kG,
with a filling factor f = 12.5 ± 1.7% (unsigned magnetic flux Bf =
237 ± 36 G). The large-scale magnetic field geometry, chromospheric
emission and broadband photometry display clear signs of non-rotational
evolution over the course of data collection. Characteristic decay times
deduced from the light curve and longitudinal field fall in the range
30-40 days, while the characteristic timescale of surface differential
rotation, as derived through the evolution of the magnetic geometry,
is equal to 57 ± 5 days. The large-scale magnetic field exhibits a
combination of properties not observed previously for ɛ Eridani, with
a surface field among the weakest previously reported, but this field
is also mostly axisymmetric, and is dominated by a toroidal component.
Title: Magnetic field and chromospheric activity evolution of HD
75332: a rapid magnetic cycle in an F star without a hot Jupiter
Authors: Brown, E. L.; Marsden, S. C.; Mengel, M. W.; Jeffers, S. V.;
Millburn, I.; Mittag, M.; Petit, P.; Vidotto, A. A.; Morin, J.; See,
V.; Jardine, M.; González-Pérez, J. N.; González-Pérez, J. N.;
BCool Collaboration
Bibcode: 2021MNRAS.501.3981B
Altcode: 2020arXiv201205407B; 2020MNRAS.tmp.3669B
Studying cool star magnetic activity gives an important insight into
the stellar dynamo and its relationship with stellar properties, as
well as allowing us to place the Sun's magnetism in the context of
other stars. Only 61 Cyg A (K5V) and τ Boo (F8V) are currently known
to have magnetic cycles like the Sun's, where the large-scale magnetic
field polarity reverses in phase with the star's chromospheric activity
cycles. τ Boo has a rapid ~240 d magnetic cycle, and it is not yet
clear whether this is related to the star's thin convection zone or
if the dynamo is accelerated by interactions between τ Boo and its
hot Jupiter. To shed light on this, we studied the magnetic activity
of HD 75332 (F7V) which has similar physical properties to τ Boo and
does not appear to host a hot Jupiter. We characterized its long-term
chromospheric activity variability over 53 yr and used Zeeman Doppler
Imaging to reconstruct the large-scale surface magnetic field for 12
epochs between 2007 and 2019. Although we observe only one reversal of
the large-scale magnetic dipole, our results suggest that HD 75332 has
a rapid ~1.06 yr solar-like magnetic cycle where the magnetic field
evolves in phase with its chromospheric activity. If a solar-like
cycle is present, reversals of the large-scale radial field polarity
are expected to occur at around activity cycle maxima. This would be
similar to the rapid magnetic cycle observed for τ Boo, suggesting
that rapid magnetic cycles may be intrinsic to late-F stars and related
to their shallow convection zones.
Title: Activity sensitive spectral lines of M dwarfs in the CARMENES
visible and near infrared spectral range: impact on radial velocity
determinations and stellar parameters determination
Authors: López-Gallifa, Álvaro; Montes, David; Labarga, Fernando;
Marfil, Emilo; Tabernero, Hugo M.; Caballero, José A.; Lafarga,
Marina; Jeffers, Sandra V.; Reiners, Ansgar; Ribas, Ignasi;
Quirrenbach, Andreas; Amado, Pedro J.
Bibcode: 2021csss.confE.138L
Altcode:
In this contribution we summarize our project devoted to identify
activity-sensitive spectral lines in the CARMENES visible and
near-infrared spectral range of M dwarfs. The aim is to contribute
to solve the problem of stellar activity in RV measurements to search
for exoplanets around these stars and in the determination of precise
stellar parameters. To identify lines with a significant chromospheric
contribution, apart from well known activity indicators (Na I D 1 D
2 He I D 3 Hα, and Ca II IRT lines, He I 10830 Å, Paγ and Paβ
lines), we have used the spectral subtraction technique using our
Python code iSTARMOD Labarga Montes 2020 choosing as reference the
spectrum of the star with lower activity. We confirm the new activity
sensitive lines by analysing the correlation with the other well known
activity indicators in the same spectra and their temporal evolution
in two particular active stars EV Lac (EV Lacertae, M 3.5) and YZ CMi
(YZ Canis Minoris, M 4.5). They are specially active stars with strong
flares and strong magnetic fields. In addition, we analyse line by line
the template spectrum (co added of all the individual spectra available)
of these two stars applying also the spectral subtraction using in this
case as reference star an inactive M dwarf star of similar spectral
type to search for magnetically sensitive lines, that is lines with
detectable Zeeman broadening. After this analysis on YZ CMi and EV Lac,
we have found 84 and 97 chromospheric activity-sensitive lines and
160 and 170 magnetically-sensitive spectral lines respectively. We are
now studying the impact of the elimination of the activity sensitive
spectral lines identified in this way on the RV determination using
cross correlation functions with weighted binary masks as in Lafarga
et al. (2020) and on the stellar parameters determination by spectral
synthesis as in Marfil et al. (2021).
Title: Stellar atmospheric parameters of CARMENES GTO M dwarfs with
spectral synthesis and SteParSyn
Authors: Marfil, Emilio; Tabernero, Hugo M.; Montes, David; Caballero,
Jose Antonio; Lazaro-Barrasa, Francisco Javier; González Hernández,
Jonay I.; Nagel, Evangelos; Passegger, Vera M.; Schweitzer, Andreas;
Ribas, Ignasi; Reiners, Ansgar; Quirrenbach, Andreas; Amado, Pedro
J.; Cifuentes, Carlos; Cortés-Contreras, Miriam; Dreizler, Stefan;
Duque-Arribas, Christian; Galadí-Enríquez, David; Henning, Thomas;
Jeffers, Sandra V.; Kaminski, Adrian; Kürster, Martin; Lafarga,
Marina; López-Gallifa, Álvaro; Morales, Juan Carlos; Shan, Yutong;
Zechmeister, Matthias
Bibcode: 2021csss.confE..19M
Altcode: 2021csss.confE.298M
We aim to review the spectral synthesis technique to derive the stellar
atmospheric parameters (Teff, log g, and [Fe/H]) of 348 M
dwarfs in light of the optical and near-infrared spectra obtained with
CARMENES, the high-resolution, double-channel spectrograph installed at
the 3.5 m telescope at the Calar Alto observatory (Spain). The analysis
relies on the SteParSyn code as the preferred MCMC implementation of
the spectral synthesis technique, along with 75 carefully selected,
magnetically insensitive, Fe I and Ti I lines plus the γ- and ϵ-TiO
bands synthesised with a grid of BT-Settl model atmospheres and the
turbospectrum code. To avoid potential degeneracies in the parameter
space, we impose a Bayesian prior on Teff and log g based
on comprehensive, multi-band photometric data available for the
sample. As a benchmark test in Teff, log g, and [Fe/H]
we place special emphasis on three special subsets in our sample,
namely 14 M dwarfs with interferometric angular diameter measurements,
15 M+M systems, and 7 wide physical binaries harbouring an FGK-type
primary with known metallicity.
Title: The Lines are Not Fine: Measuring Vanadium Abundances in M
dwarfs from Hyperfine-Split Lines
Authors: Shan, Yutong; Reiners, Ansgar; Fabbian, Damian; Marfil,
Emilio; Montes, David; Tabernero, Hugo M.; Ribas, Ignasi; Caballero,
Jose A.; Quirrenbach, Andreas; Amado, Pedro J.; Aceituno, J.; Bejar,
Victor J. S.; Cortes-Contreras, Miriam; Dreizler, Stefan; Hatzes,
Artie P.; Henning, Thomas; Jeffers, Sandra V.; Kaminski, Adrian;
Kürster, Martin; Lafarga, Marina; Morales, Juan Carlos; Nagel,
Evangelos; Rodriguez-Lopez, Cristina; Passegger, Vera M.; Schweitzer,
Andreas; Zechmeister, Mathias
Bibcode: 2021csss.confE.160S
Altcode:
Cool star atmospheres present challenges to chemical abundance
studies. To date, only a handful of elements have been quantified for
a handful of M dwarfs. In high-resolution spectra from the CARMENES
survey, we identify a series of dramatically hyperfine-split vanadium
features between 800 and 910 nm, which have strong and clean profiles
throughout the early M-dwarf range. These 'bucket-shaped' line regions
can be well-modeled with standard model atmospheres combined with
the latest atomic data from VALD. From these line regions, we measure
vanadium abundances for 140 nearby early M dwarfs in the CARMENES GTO
sample and confirm that they follow the same trend with metallicity
as the FG-type stars in the solar neighborhood, i.e., significantly
above predictions from galactic chemical evolution models. Exhibiting
a tight correlation with iron, vanadium abundances show promise
as a potential metallicity indicator for M dwarfs. We also present
evidence that several well-known chemical studies of K dwarfs have
systematically overestimated their vanadium abundances largely as a
result of neglecting to model hyperfine structure, a bias that worsens
with decreasing temperature. Our work highlights opportunities for
robust chemical analysis of cool stars afforded by high-quality spectra
redward of visible.
Title: Mapping stellar activity indicators across the M dwarf domain
Authors: Lafarga, Marina; Ribas, Ignasi; Reiners, Ansgar; Quirrenbach,
Andreas; Amado, Pedro J.; Caballero, Jose A.; Azzaro, Marco;
Béjar, Víctor J. S.; Cortés-Contreras, Miriam; Dreizler, Stefan;
Hatzes, Artie P.; Henning, Thomas; Jeffers, Sandra V.; Kaminski,
A.; Kürster, Martin; Montes, David; Morales, Juan Carlos; Oshagh,
Mahmoud; Rodríguez-López, Cristina; Schöfer, Patrick; Schweitzer,
Andreas; Zechmeister, Mathias
Bibcode: 2021csss.confE.184L
Altcode:
Despite stellar magnetic activity being present in most cool
stars, its effects on spectroscopic observations are still not
well understood. Several activity indicators are routinely used to
identify activity-related signals in radial velocity (RV) measurements,
but not all indicators trace exactly the same effects, nor are any
of them always effective in all stars. This poses one of the main
obstacles for the detection and characterisation of small exoplanets,
as magnetic activity biases RV signals. In this work, we analyse
the temporal behaviour of RVs and a set of spectroscopic indicators
for 98 M dwarfs observed with CARMENES, with the aim of finding a
relation between indicator performance and stellar properties. We find
periodic signals related to activity for 56 sample stars. The activity
indicators behave differently depending on the mass and activity level
of the target star, e.g., cross-correlation function bisector inverse
slope and chromatic index are effective activity tracers for the most
active stars in the sample, especially stars with relatively high mass,
while for less active stars, chromospheric lines perform best. Most of
the targets for which we cannot identify any activity-related signal
are stars at the low-mass end of the sample, where stars are fully
convective, and also show the lowest RV scatter. This could potentially
hint at different manifestations of activity compared to higher-mass
stars. Moreover, ultracool M dwarfs could be better candidates for
planet searches than earlier types, which display higher levels of RV
variability. Our results show that none of the indicators are effective
activity tracers for all stars. Therefore, an analysis of a large set
of indicators seems necessary to obtain a complete picture of stellar
activity variability. This becomes critical when assessing the origin
of RV signals, as not using the most effective indicators considering
the characteristics of the star may lead to false planet claims.
Title: A Deep Learning Approach to photospheric Parameters of CARMENES
Target Stars
Authors: Passegger, Vera Maria; Ordieres-Meré, Joaquin; Bello-García,
Antonio; Caballero, José Antonio; Schweitzer, Andreas; Amado, Pedro
J.; González-Marcos, Ana; Ribas, Ignasi; Reiners, Ansgar; Quirrenbach,
Andreas; Sarro, Luis M.; Solano, Enrique; Azzaro, Marco; Bauer, Florian
F.; Béjar, Victor J. S.; Cortés-Contreras, Miriam; Dreizler, Stefan;
Hatzes, Artie P.; Henning, Thomas; Jeffers, Sandra V.; Kaminski,
Adrian; Kürster, Martin; Lafarga, Marina; Marfil, Emilio; Montes,
David; Morales, Juan Carlos; Nagel, Evangelos; Tabernero, Hugo M.;
Zechmeister, Mathias
Bibcode: 2021csss.confE..71P
Altcode:
We construct an individual convolutional neural network architecture
for each of the four stellar parameters effective temperature (Teff),
surface gravity (log g), metallicity [M/H], and rotational velocity
(v sin i). The networks are trained on synthetic PHOENIX-ACES spectra,
showing small training and validation errors. We apply the trained
networks to the observed spectra of 283 M dwarfs observed with
CARMENES. Although the network models do very well on synthetic
spectra, we find large deviations from literature values especially
for metallicity, due to the synthetic gap.
Title: Chromospheric flux-flux relationships of the CARMENES active
RV-loud M Dwarfs
Authors: Labarga, Fernando; Montes, David; Lopez-Gallifa, Alvaro;
Caballero, Jose A.; Jeffers, Sandra V.; Reiners, Ansgar; Ribas,
Ignasi; Quirrenbach, Andreas; Amado, Pedro J.
Bibcode: 2021csss.confE.202L
Altcode:
The main objective of this work within CARMENES survey is the extraction
of all available information on the chromospheric activity and its
variability (rotational modulation, flares, etc.) using for that all
the chromospheric indicators included in the spectral range of the
spectrograph, ranging from visible (VIS), including the Na I D1, D2 He
I D3, and H lines to near-infrared (NIR) that include the Ca II IRT,
He I 10830 Å, Paschen a, Paschen b and Paschen d lines. We study in
detail the behavior of the flux-flux relationships of lines formed at
different chromosphere layers in order to a better understanding of the
magnetic activity of M-type dwarf stars. For this task we have selected
the CARMENES active RV-loud M Dwarfs (Tal-Or et al. 2018) and apply the
spectral subtraction technique using iSTARMOD to derive te equivalent
width (EW) of the chromospheric excess emission of the different lines
that is converted to surface flux using the c factor methodology defined
by Walkowicz et al. (2004) and implemented as Reiners & Basri
(2008), using the set of BT-Settl-CIFIST [Fe/H] = 0 synthetic spectra
as in Cifuentes et al. (2020). The ongoing results extends the frame
of the work done for FGK stars in Martinez-Arnáiz et al. (2011) and
confirms the non-universality of the flux-flux relationship presented
there, with two or more distinct chromospheric emitter populations.
Title: A nearby transiting rocky exoplanet that is suitable for
atmospheric investigation
Authors: Trifonov, T.; Caballero, J. A.; Morales, J. C.; Seifahrt, A.;
Ribas, I.; Reiners, A.; Bean, J. L.; Luque, R.; Parviainen, H.; Pallé,
E.; Stock, S.; Zechmeister, M.; Amado, P. J.; Anglada-Escudé, G.;
Azzaro, M.; Barclay, T.; Béjar, V. J. S.; Bluhm, P.; Casasayas-Barris,
N.; Cifuentes, C.; Collins, K. A.; Collins, K. I.; Cortés-Contreras,
M.; de Leon, J.; Dreizler, S.; Dressing, C. D.; Esparza-Borges, E.;
Espinoza, N.; Fausnaugh, M.; Fukui, A.; Hatzes, A. P.; Hellier, C.;
Henning, Th.; Henze, C. E.; Herrero, E.; Jeffers, S. V.; Jenkins,
J. M.; Jensen, E. L. N.; Kaminski, A.; Kasper, D.; Kossakowski, D.;
Kürster, M.; Lafarga, M.; Latham, D. W.; Mann, A. W.; Molaverdikhani,
K.; Montes, D.; Montet, B. T.; Murgas, F.; Narita, N.; Oshagh,
M.; Passegger, V. M.; Pollacco, D.; Quinn, S. N.; Quirrenbach, A.;
Ricker, G. R.; Rodríguez López, C.; Sanz-Forcada, J.; Schwarz, R. P.;
Schweitzer, A.; Seager, S.; Shporer, A.; Stangret, M.; Stürmer, J.;
Tan, T. G.; Tenenbaum, P.; Twicken, J. D.; Vanderspek, R.; Winn, J. N.
Bibcode: 2021Sci...371.1038T
Altcode: 2021arXiv210304950T
Spectroscopy of transiting exoplanets can be used to investigate their
atmospheric properties and habitability. Combining radial velocity
(RV) and transit data provides additional information on exoplanet
physical properties. We detect a transiting rocky planet with an
orbital period of 1.467 days around the nearby red dwarf star Gliese
486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii,
with uncertainties of 5%, as determined from RV data and photometric
light curves. The host star is at a distance of ~8.1 parsecs, has
a J-band magnitude of ~7.2, and is observable from both hemispheres
of Earth. On the basis of these properties and the planet’s short
orbital period and high equilibrium temperature, we show that this
terrestrial planet is suitable for emission and transit spectroscopy.
Title: A deep learning approach to photospheric parameters of CARMENES
target stars
Authors: Passegger, Vera Maria; Bello-García, Antonio; Ordieres-Meré,
Joaquin; Caballero, José Antonio; Schweitzer, Andreas; Amado, Pedro
J.; González-Marcos, Ana; Ribas, Ignasi; Reiners, Ansgar; Quirrenbach,
Andreas; Sarro, Luis M.; Solano, Enrique; Azzaro, Marco; Bauer, Florian
F.; Béjar, Victor J. S.; Cortés-Contreras, Miriam; Dreizler, Stefan;
Hatzes, Artie P.; Henning, Thomas; Jeffers, Sandra V.; Kaminski,
Adrian; Kürster, Martin; Lafarga, Marina; Marfil, Emilio; Montes,
David; Morales, Juan Carlos; Nagel, Evangelos; Tabernero, Hugo M.;
Zechmeister, Mathias
Bibcode: 2021csss.confE.312P
Altcode:
In the light of more and more new instrumentation to get a deeper
insight into the universe, tons of data are collected. While traditional
machine-learning methods have been used in processing stellar spectral
data, such large new datasets are better handled with Deep Learning (DL)
techniques. In this work, we present a Deep Convolutional Neural Network
(CNN) approach to derive fundamental stellar parameters (effective
temperature, surface gravity, metallicity and rotational velocity)
from high-resolution high signal-to-noise ratio spectra. We construct
an individual CNN architecture for each of the four parameters and
train them on synthetic PHOENIX-ACES spectra. After that, we apply
the trained networks to the observed spectra of 50 M dwarfs observed
with CARMENES. The CARMENES spectrograph, installed on the 3.5 m
telescope at the Calar Alto Observatory (Spain) has two channels,
covering the visible (0.52 to 0.96 µm, R = 96,400) and near-infrared
(0.96 to 1.71 µm, R = 80,600) spectral ranges. We compare our results
to literature values, and demonstrate that our method can be used
for stellar parameter determination without the need of having a huge
sample of stellar spectra with known parameters, because our networks
can be trained on synthetic spectra. Introducing Deep Transfer Learning
(DTL) in our approach allows us to transfer external knowledge about
the stellar parameters (e.g., from interferometry) to our training
set and therefore improve our results compared to literature.
Title: Field linkage and magnetic helicity density
Authors: Jardine, Moira; Lund, Kristin; Russell, Alexander; Donati,
Jean-Francois; Fares, Rim; Folsom, Colin; Jeffers, Sandra; Marsden,
Stephen; Morin, Julien; Pascal, Petit; See, Victor
Bibcode: 2021csss.confE.299J
Altcode:
Magnetic helicity is a fundamental property of magnetic fields that
measures the amount of linkage and twist of field lines within
a given volume. Since it is exactly conserved in ideal MHD and
highly conserved for high magnetic Reynolds numbers in general
\citep{Woltjer1958,Taylor1974}, helicity is an important factor
when attempting to understand how magnetic fields are generated and
evolve \citep[e.g.][]{Brandenburg2005,Chatterjee2011,Pipin2019}. Until
recently, this could only be measured for the Sun \citep[e.g. reviews
by][]{Demoulin2007,Demoulin2009}. We can, however, now map all three
components of the large-scale magnetic field at the surfaces of stars
using the spectropolarimetric technique of Zeeman-Doppler imaging
\citep{Semel1989}. These magnetic field maps now exist for a large
enough sample of stars that trends with stellar mass and rotation
period have become apparent \citep{donati2009}. In particular, it
appears that magnetic fields show different strengths and topologies in
the mass ranges above and below $\sim$ 0.5 M$_\odot$, which \textbf{is
believed to correspond to the onset of the transition from partially to
fully convective interiors}. Rapidly-rotating stars in the mass range
above $\sim$ 0.5 M$_\odot$ tend to have fields that are predominantly
toroidal \citep{Donati2008b}. The stronger the toroidal field, the more
likely it is to be axisymmetric \citep{See2015}. In the mass range
below $\sim$ 0.5 M$_\odot$, stars show predominantly axisymmetric
poloidal fields. For the lowest masses, however, a bimodal behaviour
is found, such that stars may have strong, predominantly axisymmetric
poloidal fields, or much weaker, non-axisymmetric poloidal fields
\citep{Donati2008b,Morin2008b,donati2009,Morin2010}.This difference in
magnetic fields in stars that are partially or fully convective is also
apparent in their photospheric helicity densities. Using observations
of 51 stars, \citet{Lund2020} found that the helicity density scales
with the toroidal energy according to $|\langle{h\,}\rangle|$ $\propto$
$\langle{\rm{B_{tor}}^2_{}\,\rangle}^{0.86\,\pm\,0.04}$. The scaling
with the poloidal energy is more complex, however, revealing two
groups with different behaviours. Specifically, stars less massive than
$\sim$ 0.5 M$_\odot$ appear to have an excess of poloidal energy when
compared to more massive stars with similar helicity densities. It
appears that stars with different internal structures and different
total magnetic energies may nonetheless generate magnetic fields with
the same helicity density at their surfaces. The aim of this paper is
to explore the nature of this division and the types of flux linkage
that support the measured helicity densities. In order to do that, we
have developed a novel method of visualising the linkages of different
field components across the surfaces of stars.
Title: The CARMENES search for exoplanets around M dwarfs. LP 714-47 b
(TOI 442.01): populating the Neptune desert
Authors: Dreizler, S.; Crossfield, I. J. M.; Kossakowski, D.; Plavchan,
P.; Jeffers, S. V.; Kemmer, J.; Luque, R.; Espinoza, N.; Pallé, E.;
Stassun, K.; Matthews, E.; Cale, B.; Caballero, J. A.; Schlecker, M.;
Lillo-Box, J.; Zechmeister, M.; Lalitha, S.; Reiners, A.; Soubkiou,
A.; Bitsch, B.; Zapatero Osorio, M. R.; Chaturvedi, P.; Hatzes, A. P.;
Ricker, G.; Vanderspek, R.; Latham, D. W.; Seager, S.; Winn, J.;
Jenkins, J. M.; Aceituno, J.; Amado, P. J.; Barkaoui, K.; Barbieri, M.;
Batalha, N. M.; Bauer, F. F.; Benneke, B.; Benkhaldoun, Z.; Beichman,
C.; Berberian, J.; Burt, J.; Butler, R. P.; Caldwell, D. A.; Chintada,
A.; Chontos, A.; Christiansen, J. L.; Ciardi, D. R.; Cifuentes, C.;
Collins, K. A.; Collins, K. I.; Combs, D.; Cortés-Contreras, M.;
Crane, J. D.; Daylan, T.; Dragomir, D.; Esparza-Borges, E.; Evans, P.;
Feng, F.; Flowers, E. E.; Fukui, A.; Fulton, B.; Furlan, E.; Gaidos,
E.; Geneser, C.; Giacalone, S.; Gillon, M.; Gonzales, E.; Gorjian,
V.; Hellier, C.; Hidalgo, D.; Howard, A. W.; Howell, S.; Huber, D.;
Isaacson, H.; Jehin, E.; Jensen, E. L. N.; Kaminski, A.; Kane, S. R.;
Kawauchi, K.; Kielkopf, J. F.; Klahr, H.; Kosiarek, M. R.; Kreidberg,
L.; Kürster, M.; Lafarga, M.; Livingston, J.; Louie, D.; Mann, A.;
Madrigal-Aguado, A.; Matson, R. A.; Mocnik, T.; Morales, J. C.;
Muirhead, P. S.; Murgas, F.; Nandakumar, S.; Narita, N.; Nowak,
G.; Oshagh, M.; Parviainen, H.; Passegger, V. M.; Pollacco, D.;
Pozuelos, F. J.; Quirrenbach, A.; Reefe, M.; Ribas, I.; Robertson,
P.; Rodríguez-López, C.; Rose, M. E.; Roy, A.; Schweitzer, A.;
Schlieder, J.; Shectman, S.; Tanner, A.; Şenavcı, H. V.; Teske, J.;
Twicken, J. D.; Villasenor, J.; Wang, S. X.; Weiss, L. M.; Wittrock,
J.; Yılmaz, M.; Zohrabi, F.
Bibcode: 2020A&A...644A.127D
Altcode: 2020arXiv201101716D
We report the discovery of a Neptune-like planet (LP 714-47 b, P =
4.05204 d, mb = 30.8 ± 1.5M⊕, Rb
= 4.7 ± 0.3 R⊕) located in the "hot Neptune
desert". Confirmation of the TESS Object of Interest (TOI 442.01)
was achieved with radial-velocity follow-up using CARMENES, ESPRESSO,
HIRES, iSHELL, and PFS, as well as from photometric data using TESS,
Spitzer, and ground-based photometry from MuSCAT2, TRAPPIST-South,
MONET-South, the George Mason University telescope, the Las Cumbres
Observatory Global Telescope network, the El Sauce telescope, the
TÜBİTAK National Observatory, the University of Louisville Manner
Telescope, and WASP-South. We also present high-spatial resolution
adaptive optics imaging with the Gemini Near-Infrared Imager. The low
uncertainties in the mass and radius determination place LP 714-47 b
among physically well-characterised planets, allowing for a meaningful
comparison with planet structure models. The host star LP 714-47 is
a slowly rotating early M dwarf (Teff = 3950 ± 51 K)
with a mass of 0.59 ± 0.02M⊙ and a radius of 0.58
± 0.02R⊙. From long-term photometric monitoring and
spectroscopic activity indicators, we determine a stellar rotation
period of about 33 d. The stellar activity is also manifested as
correlated noise in the radial-velocity data. In the power spectrum
of the radial-velocity data, we detect a second signal with a period
of 16 days in addition to the four-day signal of the planet. This
could be shown to be a harmonic of the stellar rotation period or the
signal of a second planet. It may be possible to tell the difference
once more TESS data and radial-velocity data are obtained. RV 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/cat/J/A+A/644/A127
Based on observations carried out at the Centro Astronómico
Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Junta
de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC),
on observations carried out at the European Southern Observatory
under ESO programme 0103.C-0152(A), and data collected with the 6.5
m Magellan Telescopes located at Las Campanas Observatory, Chile.
Title: The CARMENES M-dwarf planet survey
Authors: Quirrenbach, Andreas; CARMENES Consortium; Amado, P. J.;
Ribas, I.; Reiners, A.; Caballero, J. A.; Aceituno, J.; Alacid, J. M.;
Alonso-Floriano, F. J.; Anglada-Escudé, G.; Azzaro, M.; Baroch,
D.; Bauer, F. F.; Becerril, S.; Béjar, V. J. S.; Bluhm, P.; Calvo
Ortega, R.; Cardona Guillén, C.; Casasayas-Barris, N.; Chaturvedi, P.;
Cifuentes, C.; Colomé, J.; Conte, D.; Cortés-Contreras, M.; Czesla,
S.; Díez-Alonso, E.; Domínguez Fernández, A. J.; Dreizler, S.;
Duque-Arribas, C.; Espinoza, N.; Fuhrmeister, B.; Galadí-Enríquez,
D.; Gar´a Quintana, E.; González-Alvare, E.; González Cuesta,
z. L.; González Hernández, J. I.; Guenther, E. W.; de Guindos,
E.; Hatzes, A. P.; Henning, T.; Herbort, O.; Herrero, E.; Hintz,
D.; Iglesias-Pára, J.; Jeffers, S. V.; Johnson, E. N.; de Juan, E.;
Kaminski, A.; Kemmer, J.; Khaimova, J.; Khalafinejad, S.; Klahr, H.;
Kossakowski, D.; Kreidberg, L.; Kürster, M.; Labarga, F.; Lafarga, M.;
Lampón, M.; Lara, L. M.; Lillo-Box, J.; Lodieu, N.; López Gallifa,
A.; López González, M. J.; López-Puertas, M.; Luque, R.; Marfil,
E.; Martín-Ruiz, S.; Matthé, C.; Molaverdikhani, K.; Montes, D.;
Morales, J. C.; Morales-Calderóon, M.; Nagel, E.; Nortmann, L.; Nowak,
G.; Ofir, A.; Oshaghi, M.; Pallé, E.; Passegger, V. M.; Pavlov,
A.; Pedraz, S.; Perdelwitz, V.; Perger, M.; Reffert, S.; Revilla,
D.; Rodríguez, E.; Rodríguez López, C.; Sabotta, S.; Sadegi, S.;
Sairam, L.; Salz, M.; Sánchez-López, A.; Sanz-Forcada, J.; Sarkis,
P.; Schäfer, S.; Schiller, J.; Schlecker, M.; Schmitt, J. H. M. M.;
Schöfer, P.; Schweitzer, A.; Seiferta, W.; Shan, Y.; Shulyak, D.;
Skrzypinski, S. L.; Solano, E.; Soto, M. G.; Stahl, O.; Stangret, M.;
Stock, S. A.; Strachan, J. B. P.; Stuber, T.; Stürmer, J.; Tabernero,
H. M.; Tal-Or, L.; Tala-Pinto, M.; Trifonov, T.; Vanaverbeke, S.;
Yan, F.; Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2020SPIE11447E..3CQ
Altcode:
The CARMENES instrument consists of two cross-dispersed Échelle
spectrographs, which together cover the wavelength range from 5,200
to 17,100 Å. During its first five years of operation at the 3.5 m
telescope on Calar Alto, Spain, it has been used for a radial-velocity
survey of 365 M dwarfs, for follow-up radial-velocity observations
of transiting exoplanets, and for spectroscopic studies of exoplanet
atmospheres during transits. The CARMENES data have also yielded a
wealth of information on the fundamental parameters and activity of
M dwarfs. We provide an overview of the scientific results from the
main CARMENES survey in the years 2016 to 2020.
Title: The CARMENES search for exoplanets around M dwarfs. Three
temperate-to-warm super-Earths
Authors: Stock, S.; Nagel, E.; Kemmer, J.; Passegger, V. M.; Reffert,
S.; Quirrenbach, A.; Caballero, J. A.; Czesla, S.; Béjar, V. J. S.;
Cardona, C.; Díez-Alonso, E.; Herrero, E.; Lalitha, S.; Schlecker,
M.; Tal-Or, L.; Rodríguez, E.; Rodríguez-López, C.; Ribas, I.;
Reiners, A.; Amado, P. J.; Bauer, F. F.; Bluhm, P.; Cortés-Contreras,
M.; González-Cuesta, L.; Dreizler, S.; Hatzes, A. P.; Henning,
Th.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.;
López-González, M. J.; Montes, D.; Morales, J. C.; Pedraz, S.;
Schöfer, P.; Schweitzer, A.; Trifonov, T.; Zapatero Osorio, M. R.;
Zechmeister, M.
Bibcode: 2020A&A...643A.112S
Altcode: 2020arXiv201000474S
We announce the discovery of two planets orbiting the M dwarfs
GJ 251 (0.360 ± 0.015M⊙) and HD 238090 (0.578 ±
0.021M⊙) based on CARMENES radial velocity (RV) data. In
addition, we independently confirm with CARMENES data the existence
of Lalande 21185 b, a planet that has recently been discovered with
the SOPHIE spectrograph. All three planets belong to the class of
warm or temperate super-Earths and share similar properties. The
orbital periods are 14.24 d, 13.67 d, and 12.95 d and the minimum
masses are 4.0 ± 0.4 M⊕, 6.9 ± 0.9 M⊕,
and 2.7 ± 0.3 M⊕ for GJ 251 b, HD 238090 b, and Lalande
21185 b, respectively. Based on the orbital and stellar properties,
we estimate equilibrium temperatures of 351.0 ± 1.4 K for GJ 251 b,
469.6 ± 2.6 K for HD 238090 b, and 370.1 ± 6.8 K for Lalande 21185
b. For the latter we resolve the daily aliases that were present in
the SOPHIE data and that hindered an unambiguous determination of the
orbital period. We find no significant signals in any of our spectral
activity indicators at the planetary periods. The RV observations
were accompanied by contemporaneous photometric observations. We
derive stellar rotation periods of 122.1 ± 2.2 d and 96.7 ± 3.7
d for GJ 251 and HD 238090, respectively. The RV data of all three
stars exhibit significant signals at the rotational period or its
first harmonic. For GJ 251 and Lalande 21185, we also find long-period
signals around 600 d, and 2900 d, respectively, which we tentatively
attribute to long-term magnetic cycles. We apply a Bayesian approach to
carefully model the Keplerian signals simultaneously with the stellar
activity using Gaussian process regression models and extensively
search for additional significant planetary signals hidden behind
the stellar activity. Current planet formation theories suggest
that the three systems represent a common architecture, consistent
with formation following the core accretion paradigm. Tables
D.1-D.3 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/cat/J/A+A/643/A112
Title: VizieR Online Data Catalog: LP714-47 (TOI 442) radial velocity
curve (Dreizler+, 2020)
Authors: Dreizler, S.; Crossfield, I. J. M.; Kossakowski, D.; Plavchan,
P.; Jeffers, S. V.; Kemmer, J.; Luque, R.; Espinoza, N.; Palle, E.;
Stassun, K.; Matthews, E.; Cale, B.; Caballero, J. A.; Schlecker, M.;
Lillo-Box, J.; Zechmeister, M.; Lalitha, S.; Reiners, A.; Soubkiou,
A.; Bitsch, B.; Zapatero Osorio, M. R.; Chaturvedi, P.; Hatzes, A. P.;
Ricker, G.; Vanderspek, R.; Latham, D. W.; Seager, S.; Winn, J.;
Jenkins, J. M.; Aceituno, J.; Amado, P. J.; Barkaoui, K.; Barbieri, M.;
Batalha, N. M.; Bauer, F. F.; Benneke, B.; Benkhaldoun, Z.; Beichman,
C.; Berberian, J.; Burt, J.; Butler, R. P.; Caldwell, D. A.; Chintada,
A.; Chontos, A.; Christiansen, J. L.; Ciardi, D. R.; Cifuentes, C.;
Collins, K. A.; Collins, K. I.; Combs, D.; Cortes-Contreras, M.;
Crane, J. D.; Daylan, T.; Dragomir, D.; Esparza-Borges, E.; Evans,
P.; Feng, F.; Flowers, E. E.; Fukui, A.; Fulton, B.; Furlan, E.;
Gaidos, E.; Geneser, C.; Giacalone, S.; Gillon, M.; Gonzales, E.;
Gorjian, V.; Hellier, C.; Hidalgo, D.; Howard, A. W.; Howell, S.;
Huber, D.; Isaacson, H.; Jehin, E.; Jensen, E. L. N.; Kaminski, A.;
Kane, S. R.; Kawauchi, K.; Kielkopf, J. F.; Klahr, H.; Kosiarek,
M. R.; Kreidberg, L.; Kuerster, M.; Lafarga, M.; Livingston, J.;
Louie, D.; Mann, A.; Madrigal-Aguado, A.; Matson, R. A.; Mocnik,
T.; Morales, J. C.; Muirhead, P. S.; Murgas, F.; Nandakumar, S.;
Narita, N.; Nowak, G.; Oshagh, M.; Parviainen, H.; Passegger, V. M.;
Pollacco, D.; Pozuelos, F. J.; Quirrenbach, A.; Reefe, M.; Ribas, I.;
Robertson, P.; Rodriguez-Lopez, C.; Rose, M. E.; Roy, A.; Schweitzer,
A.; Schlieder, J.; Shectman, S.; Tanner, A.; Senavci, H. V.; Teske, J.;
Twicken, J. D.; Villasenor, J.; Wang, S. X.; Weiss, L. M.; Wittrock,
J.; Yilmaz, M.; Zohrabi, F.
Bibcode: 2020yCat..36440127D
Altcode:
High-resolution follow-up spectroscopy of the TESS planet candidates
is arranged by the TESS follow-up programme (TFOP), "Precise Radial
Velocities" SG4 subgroup. We obtained High-resolution follow-up
spectroscopy for LP714-47 with CARMENES-VIS, CARMENES-NIR, ESPRESSO,
HIRES, iSHELL, and PFS. The observations began at mid February 2019,
just after the announcement of the transiting planet candidate, and
ended in January 2020. In this period, we collected 102 spectra. The
spectral resolution and the number of spectra obtained by the individual
instruments are listed in Table 1 of the paper. The table contains
the time of observation as Barycentric Julian Date in units of days,
the measure radial velocities in unites of m/s, the measurement
uncertainties measured in m/s, and the instrument name. (1
data file).
Title: Discovery of a hot, transiting, Earth-sized planet and a second
temperate, non-transiting planet around the M4 dwarf GJ 3473 (TOI-488)
Authors: Kemmer, J.; Stock, S.; Kossakowski, D.; Kaminski, A.;
Molaverdikhani, K.; Schlecker, M.; Caballero, J. A.; Amado, P. J.;
Astudillo-Defru, N.; Bonfils, X.; Ciardi, D.; Collins, K. A.; Espinoza,
N.; Fukui, A.; Hirano, T.; Jenkins, J. M.; Latham, D. W.; Matthews,
E. C.; Narita, N.; Pallé, E.; Parviainen, H.; Quirrenbach, A.;
Reiners, A.; Ribas, I.; Ricker, G.; Schlieder, J. E.; Seager, S.;
Vanderspek, R.; Winn, J. N.; Almenara, J. M.; Béjar, V. J. S.;
Bluhm, P.; Bouchy, F.; Boyd, P.; Christiansen, J. L.; Cifuentes,
C.; Cloutier, R.; Collins, K. I.; Cortés-Contreras, M.; Crossfield,
I. J. M.; Crouzet, N.; de Leon, J. P.; Della-Rose, D. D.; Delfosse,
X.; Dreizler, S.; Esparza-Borges, E.; Essack, Z.; Forveille, Th.;
Figueira, P.; Galadí-Enríquez, D.; Gan, T.; Glidden, A.; Gonzales,
E. J.; Guerra, P.; Harakawa, H.; Hatzes, A. P.; Henning, Th.; Herrero,
E.; Hodapp, K.; Hori, Y.; Howell, S. B.; Ikoma, M.; Isogai, K.;
Jeffers, S. V.; Kürster, M.; Kawauchi, K.; Kimura, T.; Klagyivik,
P.; Kotani, T.; Kurokawa, T.; Kusakabe, N.; Kuzuhara, M.; Lafarga,
M.; Livingston, J. H.; Luque, R.; Matson, R.; Morales, J. C.; Mori,
M.; Muirhead, P. S.; Murgas, F.; Nishikawa, J.; Nishiumi, T.; Omiya,
M.; Reffert, S.; Rodríguez López, C.; Santos, N. C.; Schöfer, P.;
Schwarz, R. P.; Shiao, B.; Tamura, M.; Terada, Y.; Twicken, J. D.;
Ueda, A.; Vievard, S.; Watanabe, N.; Zechmeister, M.
Bibcode: 2020A&A...642A.236K
Altcode: 2020arXiv200910432K
We present the confirmation and characterisation of GJ 3473 b (G 50-16,
TOI-488.01), a hot Earth-sized planet orbiting an M4 dwarf star, whose
transiting signal (P = 1.1980035 ± 0.0000018 d) was first detected
by the Transiting Exoplanet Survey Satellite (TESS). Through a joint
modelling of follow-up radial velocity observations with CARMENES, IRD,
and HARPS together with extensive ground-based photometric follow-up
observations with LCOGT, MuSCAT, and MuSCAT2, we determined a precise
planetary mass, Mb = 1.86 ± 0.30 M⊕, and
radius, Rb = 1.264 ± 0.050 R⊕. Additionally,
we report the discovery of a second, temperate, non-transiting planet
in the system, GJ 3473 c, which has a minimum mass, Mc sin
i = 7.41 ± 0.91 M⊕, and orbital period, Pc
= 15.509 ± 0.033 d. The inner planet of the system, GJ 3473 b,
is one of the hottest transiting Earth-sized planets known thus
far, accompanied by a dynamical mass measurement, which makes it a
particularly attractive target for thermal emission spectroscopy. RV 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/cat/J/A+A/642/A236
Title: The CARMENES search for exoplanets around M dwarfs. Two
planets on opposite sides of the radius gap transiting the nearby
M dwarf LTT 3780
Authors: Nowak, G.; Luque, R.; Parviainen, H.; Pallé, E.;
Molaverdikhani, K.; Béjar, V. J. S.; Lillo-Box, J.; Rodríguez-López,
C.; Caballero, J. A.; Zechmeister, M.; Passegger, V. M.; Cifuentes,
C.; Schweitzer, A.; Narita, N.; Cale, B.; Espinoza, N.; Murgas, F.;
Hidalgo, D.; Zapatero Osorio, M. R.; Pozuelos, F. J.; Aceituno, F. J.;
Amado, P. J.; Barkaoui, K.; Barrado, D.; Bauer, F. F.; Benkhaldoun,
Z.; Caldwell, D. A.; Casasayas Barris, N.; Chaturvedi, P.; Chen, G.;
Collins, K. A.; Collins, K. I.; Cortés-Contreras, M.; Crossfield,
I. J. M.; de León, J. P.; Díez Alonso, E.; Dreizler, S.; El Mufti,
M.; Esparza-Borges, E.; Essack, Z.; Fukui, A.; Gaidos, E.; Gillon,
M.; Gonzales, E. J.; Guerra, P.; Hatzes, A.; Henning, Th.; Herrero,
E.; Hesse, K.; Hirano, T.; Howell, S. B.; Jeffers, S. V.; Jehin, E.;
Jenkins, J. M.; Kaminski, A.; Kemmer, J.; Kielkopf, J. F.; Kossakowski,
D.; Kotani, T.; Kürster, M.; Lafarga, M.; Latham, D. W.; Law, N.;
Lissauer, J. J.; Lodieu, N.; Madrigal-Aguado, A.; Mann, A. W.; Massey,
B.; Matson, R. A.; Matthews, E.; Montañés-Rodríguez, P.; Montes,
D.; Morales, J. C.; Mori, M.; Nagel, E.; Oshagh, M.; Pedraz, S.;
Plavchan, P.; Pollacco, D.; Quirrenbach, A.; Reffert, S.; Reiners,
A.; Ribas, I.; Ricker, G. R.; Rose, M. E.; Schlecker, M.; Schlieder,
J. E.; Seager, S.; Stangret, M.; Stock, S.; Tamura, M.; Tanner, A.;
Teske, J.; Trifonov, T.; Twicken, J. D.; Vanderspek, R.; Watanabe,
D.; Wittrock, J.; Ziegler, C.; Zohrabi, F.
Bibcode: 2020A&A...642A.173N
Altcode: 2020arXiv200301140N
We present the discovery and characterisation of two transiting
planets observed by the Transiting Exoplanet Survey Satellite
(TESS) orbiting the nearby (d⋆ ≈ 22 pc), bright (J
≈ 9 mag) M3.5 dwarf LTT 3780 (TOI-732). We confirm both planets
and their association with LTT 3780 via ground-based photometry and
determine their masses using precise radial velocities measured with
the CARMENES spectrograph. Precise stellar parameters determined
from CARMENES high-resolution spectra confirm that LTT 3780 is a
mid-M dwarf with an effective temperature of Teff = 3360
± 51 K, a surface gravity of log g⋆ = 4.81 ± 0.04
(cgs), and an iron abundance of [Fe/H] = 0.09 ± 0.16 dex, with an
inferred mass of M⋆ = 0.379 ± 0.016M⊙
and a radius of R⋆ = 0.382 ± 0.012R⊙. The
ultra-short-period planet LTT 3780 b (Pb = 0.77 d) with
a radius of 1.35-0.06+0.06 R⊕,
a mass of 2.34-0.23+0.24 M⊕, and a
bulk density of 5.24-0.81+0.94 g cm-3
joins the population of Earth-size planets with rocky, terrestrial
composition. The outer planet, LTT 3780 c, with an orbital period of
12.25 d, radius of 2.42-0.10+0.10 R⊕,
mass of 6.29-0.61+0.63 M⊕, and
mean density of 2.45-0.37+0.44 g cm-3
belongs to the population of dense sub-Neptunes. With the two planets
located on opposite sides of the radius gap, this planetary system
is anexcellent target for testing planetary formation, evolution,
and atmospheric models. In particular, LTT 3780 c is an ideal object
for atmospheric studies with the James Webb Space Telescope (JWST).
Title: The CARMENES search for exoplanets around M dwarfs. Rubidium
abundances in nearby cool stars
Authors: Abia, C.; Tabernero, H. M.; Korotin, S. A.; Montes, D.;
Marfil, E.; Caballero, J. A.; Straniero, O.; Prantzos, N.; Ribas,
I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; Béjar, V. J. S.;
Cortés-Contreras, M.; Dreizler, S.; Henning, Th.; Jeffers, S. V.;
Kaminski, A.; Kürster, M.; Lafarga, M.; López-Gallifa, Á.; Morales,
J. C.; Nagel, E.; Passegger, V. M.; Pedraz, S.; Rodríguez López,
C.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2020A&A...642A.227A
Altcode: 2020arXiv200900876A
Due to their ubiquity and very long main-sequence lifetimes, abundance
determinations in M dwarfs provide a powerful and alternative tool to
GK dwarfs to study the formation and chemical enrichment history of our
Galaxy. In this study, abundances of the neutron-capture elements Rb,
Sr, and Zr are derived, for the first time, in a sample of nearby M
dwarfs. We focus on stars in the metallicity range - 0.5 ≲ [Fe/H]
≲ +0.3, an interval poorly explored for Rb abundances in previous
analyses. To do this we use high-resolution, high-signal-to-noise-ratio,
optical and near-infrared spectra of 57 M dwarfs observed with
CARMENES. The resulting [Sr/Fe] and [Zr/Fe] ratios for most M dwarfs
are almost constant at about the solar value, and are identical to
those found in GK dwarfs of the same metallicity. However, for Rb we
find systematic underabundances ([Rb/Fe] < 0.0) by a factor two on
average. Furthermore, a tendency is found for Rb - but not for other
heavy elements (Sr, Zr) - to increase with increasing metallicity
such that [Rb/Fe] ≳ 0.0 is attained at metallicities higher than
solar. These are surprising results, never seen for any other heavy
element, and are difficult to understand within the formulation of
the s- and r-processes, both contributing sources to the Galactic
Rb abundance. We discuss the reliability of these findings for
Rb in terms of non-LTE (local thermodynamic equilibrium) effects,
stellar activity, or an anomalous Rb abundance in the Solar System,
but no explanation is found. We then interpret the full observed [Rb/Fe]
versus [Fe/H] trend within the framework of theoretical predictions from
state-of-the-art chemical evolution models for heavy elements, but a
simple interpretation is not found either. In particular, the possible
secondary behaviour of the [Rb/Fe] ratio at super-solar metallicities
would require a much larger production of Rb than currently predicted
in AGB stars through the s-process without overproducing Sr and Zr.
Title: The CARMENES search for exoplanets around M dwarfs. A deep
learning approach to determine fundamental parameters of target stars
Authors: Passegger, V. M.; Bello-García, A.; Ordieres-Meré, J.;
Caballero, J. A.; Schweitzer, A.; González-Marcos, A.; Ribas, I.;
Reiners, A.; Quirrenbach, A.; Amado, P. J.; Azzaro, M.; Bauer, F. F.;
Béjar, V. J. S.; Cortés-Contreras, M.; Dreizler, S.; Hatzes, A. P.;
Henning, Th.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga,
M.; Marfil, E.; Montes, D.; Morales, J. C.; Nagel, E.; Sarro, L. M.;
Solano, E.; Tabernero, H. M.; Zechmeister, M.
Bibcode: 2020A&A...642A..22P
Altcode: 2020arXiv200801186P
Existing and upcoming instrumentation is collecting large amounts
of astrophysical data, which require efficient and fast analysis
techniques. We present a deep neural network architecture to analyze
high-resolution stellar spectra and predict stellar parameters such as
effective temperature, surface gravity, metallicity, and rotational
velocity. With this study, we firstly demonstrate the capability of
deep neural networks to precisely recover stellar parameters from
a synthetic training set. Secondly, we analyze the application of
this method to observed spectra and the impact of the synthetic gap
(i.e., the difference between observed and synthetic spectra) on the
estimation of stellar parameters, their errors, and their precision. Our
convolutional network is trained on synthetic PHOENIX-ACES spectra
in different optical and near-infrared wavelength regions. For
each of the four stellar parameters, Teff, log g, [M/H],
and v sin i, we constructed a neural network model to estimate each
parameter independently. We then applied this method to 50 M dwarfs with
high-resolution spectra taken with CARMENES (Calar Alto high-Resolution
search for M dwarfs with Exo-earths with Near-infrared and optical
Échelle Spectrographs), which operates in the visible (520-960 nm)
and near-infrared wavelength range (960-1710 nm) simultaneously. Our
results are compared with literature values for these stars. They
show mostly good agreement within the errors, but also exhibit large
deviations in some cases, especially for [M/H], pointing out the
importance of a better understanding of the synthetic gap.
Title: VizieR Online Data Catalog: CARMENES VIS RVs of 3 M dwarfs
(Stock+, 2020)
Authors: Stock, S.; Nagel, E.; Kemmer, J.; Passegger, V. M.; Reffert,
S.; Quirrenbach, A.; Caballero, J. A.; Czesla, S.; Bejar, V. J. S.;
Cardona, C.; Diez-Alonso, E.; Herrero, E.; Lalitha, S.; Schlecker, M.;
Tal-Or, L.; Rodriguez, E.; Rodriguez-Lopez, C.; Ribas, I.; Reiners,
A.; Amado, P. J.; Bauer, F. F.; Bluhm, P.; Cortes-Contreras, M.;
Gonzalez-Cuesta, L.; Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers,
S. V.; Kaminski, A.; Kuerster, M.; Lafarga, M.; Lopez-Gonzalez, M. J.;
Montes, D.; Morales, J. C.; Pedraz, S.; Schoefer, P.; Schweitzer,
A.; Trifonov, T.; Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2020yCat..36430112S
Altcode:
We acquired spectra with CARMENES (Quirrenbach et al., 2014, in
Proc. SPIE, Vol. 9147, Ground-based and Airborne Instrumentation for
Astronomy V, 91471F), a high-resolution precise echelle spectrograph
mounted at the 3.5m telescope at the Calar Alto Observatory in Spain. (3 data files).
Title: VizieR Online Data Catalog: GJ 3473 (TOI-488) radial velocity
curve (Kemmer+, 2020)
Authors: Kemmer, J.; Stock, S.; Kossakowski, D.; Kaminski, A.;
Molaverdikhani, K.; Schlecker, M.; Caballero, J. A.; Amado, P. J.;
Astudillo-Defru, N.; Bonfils, X.; Ciardi, D.; Collins, K. A.; Espinoza,
N.; Fukui, A.; Hirano, T.; Jenkins, J. M.; Latham, D. W.; Matthews,
E. C.; Narita, N.; Palle, E.; Parviainen, H.; Quirrenbach, A.; Reiners,
A.; Ribas, I.; Ricker, G.; Schlieder, J. E.; Seager, S.; Vanderspek,
R.; Winn, J. N.; Almenara, J. M.; Bejar, V. J. S.; Bluhm, P.; Bouchy,
F.; Boyd, P.; Christiansen, J. L.; Cifuentes, C.; Cloutier, R.;
Collins, K. I.; Cortes-Contreras, M.; I. J. M., Crossfield; Crouzet,
N.; de, Leon J. P.; Della-Rose, D. D.; Delfosse, X.; Dreizler,
S.; Esparza-Borges, E.; Essack, Z.; Forveille, T.; Figueira, P.;
Galadi-Enriquez, D.; Gan, T.; Glidden, A.; Gonzales, E. J.; Guerra,
P.; Harakawa, H.; Hatzes, A. P.; Henning, T.; Herrero, E.; Hodapp,
K.; Hori, Y.; Howell, S. B.; Ikoma, M.; Isogai, K.; Jeffers, S. V.;
Kuerster, M.; Kawauchi, K.; Kimura, T.; Klagyivik, P.; Kotani, T.;
Kurokawa, T.; Kusakabe, N.; Kuzuhara, M.; Lafarga, M.; Livingston,
J. H.; Luqu!, E. R.; Mat Son, R.; Morales, J. C.; Mori, M.; Muirhead,
P. S.; Murgas, F.; Nishikawa, J.; Nishiumi, T.; Omiya, M.; Reffert,
S.; Rodriguez Lopez, C.; Santos, N. C.; Schoefer, P.; Schwarz, R. P.;
Shiao, B.; Tamura, M.; Terada, Y.; Twicken, J. D.; Ueda, A.; Vievard,
S.; Watanabe, N.; Zechmeister, M.
Bibcode: 2020yCat..36420236K
Altcode:
High-resolution follow-up spectroscopy of the TESS planet candidates
is arranged by the TESS follow-up programme (TFOP), "Precise Radial
Velocities" SG4 subgroup. We observed GJ 3473 with CARMENES. The
observations began at the end of March 2019, just after the announcement
of the transiting planet candidate, and ended in January 2020. In this
period, we collected 67 pairs of VIS and NIR spectra with exposure
times of about 30 min each. In the course of the Subaru IRD TESS
Intensive Follow-up Project (proposal S19A-069I), we observed GJ 3473
with the InfraRed Doppler spectrograph (IRD). A total of 56 frames were
acquired for GJ 3473 by IRD on 12 different nights between April 2019
and December 2019. GJ 3473 was also observed by the High Accuracy
Radial velocity Planet Searcher (HARPS). The 32 observations presented
here were taken between May 2019 and March 2020. (1 data file).
Title: The CARMENES search for exoplanets around M dwarfs. Convective
shift and starspot constraints from chromatic radial velocities
Authors: Baroch, D.; Morales, J. C.; Ribas, I.; Herrero, E.;
Rosich, A.; Perger, M.; Anglada-Escudé, G.; Reiners, A.; Caballero,
J. A.; Quirrenbach, A.; Amado, P. J.; Jeffers, S. V.; Cifuentes,
C.; Passegger, V. M.; Schweitzer, A.; Lafarga, M.; Bauer, F. F.;
Béjar, V. J. S.; Colomé, J.; Cortés-Contreras, M.; Dreizler, S.;
Galadí-Enríquez, D.; Hatzes, A. P.; Henning, Th.; Kaminski, A.;
Kürster, M.; Montes, D.; Rodríguez-López, C.; Zechmeister, M.
Bibcode: 2020A&A...641A..69B
Altcode: 2020arXiv200616608B
Context. Variability caused by stellar activity represents a challenge
to the discovery and characterization of terrestrial exoplanets and
complicates the interpretation of atmospheric planetary signals.
Aims: We aim to use a detailed modeling tool to reproduce the
effect of active regions on radial velocity measurements, which aids
the identification of the key parameters that have an impact on the
induced variability.
Methods: We analyzed the effect of stellar
activity on radial velocities as a function of wavelength by simulating
the impact of the properties of spots, shifts induced by convective
motions, and rotation. We focused our modeling effort on the active
star YZ CMi (GJ 285), which was photometrically
and spectroscopically monitored with CARMENES and the Telescopi Joan
Oró.
Results: We demonstrate that radial velocity curves
at different wavelengths yield determinations of key properties of
active regions, including spot-filling factor, temperature contrast,
and location, thus solving the degeneracy between them. Most notably,
our model is also sensitive to convective motions. Results indicate a
reduced convective shift for M dwarfs when compared to solar-type stars
(in agreement with theoretical extrapolations) and points to a small
global convective redshift instead of blueshift.
Conclusions:
Using a novel approach based on simultaneous chromatic radial velocities
and light curves, we can set strong constraints on stellar activity,
including an elusive parameter such as the net convective motion effect.
Title: The impact of unresolved magnetic spots on high-precision
radial velocity measurements
Authors: Lisogorskyi, M.; Boro Saikia, S.; Jeffers, S. V.; Jones,
H. R. A.; Morin, J.; Mengel, M.; Reiners, A.; Vidotto, A. A.; Petit, P.
Bibcode: 2020MNRAS.497.4009L
Altcode: 2020arXiv200712193L; 2020MNRAS.tmp.2273L
The Doppler method of exoplanet detection has been extremely successful,
but suffers from contaminating noise from stellar activity. In this
work, a model of a rotating star with a magnetic field based on the
geometry of the K2 star ɛ Eridani is presented and used to estimate
its effect on simulated radial velocity (RV) measurements. A number of
different distributions of unresolved magnetic spots were simulated on
top of the observed large-scale magnetic maps obtained from 8 yr of
spectropolarimetric observations. The RV signals due to the magnetic
spots have amplitudes of up to 10 m s-1, high enough to
prevent the detection of planets under 20 Earth masses in temperate
zones of solar-type stars. We show that the RV depends heavily on
spot distribution. Our results emphasize that understanding stellar
magnetic activity and spot distribution is crucial for the detection
of Earth analogues.
Title: The CARMENES search for exoplanets around M dwarfs. Variability
of the He I line at 10 830 Å
Authors: Fuhrmeister, B.; Czesla, S.; Hildebrandt, L.; Nagel, E.;
Schmitt, J. H. M. M.; Jeffers, S. V.; Caballero, J. A.; Hintz, D.;
Johnson, E. N.; Schöfer, P.; Zechmeister, M.; Reiners, A.; Ribas, I.;
Amado, P. J.; Quirrenbach, A.; Nortmann, L.; Bauer, F. F.; Béjar,
V. J. S.; Cortés-Contreras, M.; Dreizler, S.; Galadí-Enríquez,
D.; Hatzes, A. P.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.
Bibcode: 2020A&A...640A..52F
Altcode: 2020arXiv200609372F
The He I infrared (IR) triplet at 10 830 Å is known as an activity
indicator in solar-type stars and has become a primary diagnostic in
exoplanetary transmission spectroscopy. He I IR lines are a tracer
of the stellar extreme-ultraviolet irradiation from the transition
region and corona. We study the variability of the He I triplet lines
in a spectral time series of 319 M dwarf stars that was obtained with
the CARMENES high-resolution optical and near-infrared spectrograph
at Calar Alto. We detect He I IR line variability in 18% of our
sample stars, all of which show Hα in emission. Therefore, we find
detectable He I variability in 78% of the sub-sample of stars with
Hα emission. Detectable variability is strongly concentrated in the
latest spectral sub-types, where the He I lines during quiescence
are typically weak. The fraction of stars with detectable He I
variation remains lower than 10% for stars earlier than M3.0 V,
while it exceeds 30% for the later spectral sub-types. Flares are
accompanied by particularly pronounced line variations, including
strongly broadened lines with red and blue asymmetries. However,
we also find evidence for enhanced He I absorption, which is
potentially associated with increased high-energy irradiation levels
at flare onset. Generally, He I and Hα line variations tend to be
correlated, with Hα being the most sensitive indicator in terms
of pseudo-equivalent width variation. This makes the He I triplet
a favourable target for planetary transmission spectroscopy. Full Table 2 is 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/cat/J/A+A/640/A52
Title: The CARMENES search for exoplanets around M dwarfs. Measuring
precise radial velocities in the near infrared: The example of the
super-Earth CD Cet b
Authors: Bauer, F. F.; Zechmeister, M.; Kaminski, A.; Rodríguez
López, C.; Caballero, J. A.; Azzaro, M.; Stahl, O.; Kossakowski,
D.; Quirrenbach, A.; Becerril Jarque, S.; Rodríguez, E.; Amado,
P. J.; Seifert, W.; Reiners, A.; Schäfer, S.; Ribas, I.; Béjar,
V. J. S.; Cortés-Contreras, M.; Dreizler, S.; Hatzes, A.; Henning,
T.; Jeffers, S. V.; Kürster, M.; Lafarga, M.; Montes, D.; Morales,
J. C.; Schmitt, J. H. M. M.; Schweitzer, A.; Solano, E.
Bibcode: 2020A&A...640A..50B
Altcode: 2020arXiv200601684B
The high-resolution, dual channel, visible and near-infrared
spectrograph CARMENES offers exciting opportunities for stellar
and exoplanetary research on M dwarfs. In this work we address the
challenge of reaching the highest radial velocity precision possible
with a complex, actively cooled, cryogenic instrument, such as the
near-infrared channel. We describe the performance of the instrument
and the work flow used to derive precise Doppler measurements from
the spectra. The capability of both CARMENES channels to detect
small exoplanets is demonstrated with the example of the nearby
M5.0 V star CD Cet (GJ 1057), around which we announce a super-Earth
(4.0 ± 0.4 M⊕) companion on a 2.29 d orbit. Based
on observations collected at the Centro Astronómico Hispano Alemán
(CAHA) at Calar Alto, Almería, Spain, operated jointly by the Junta de
Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). Based on observations collected at the European Southern Observatory,
Paranal, Chile, under program 0103.C-0152(A), and La Silla, Chile,
under programs 072.C-0488(E) and 183.C-0437(A).
Title: Stellar atmospheric parameters of FGK-type stars (EW method)
and M-type stars (spectral synthesis) from high-resolution optical
and near-infrared CARMENES spectra
Authors: Marfil, E.; Tabernero, H. M.; Montes, D.; Caballero, J. A.;
Lázaro-Barrasa, F. J.; González Hernández, J. I.; Soto, M. G.;
Nagel, E.; Kaminski, A.; Reiners, A.; Ribas, I.; Quirrenbach, A.;
Amado, P. J.; Bauer, F. F.; Cortés-Contreras, M.; Dreizler, S.;
Jeffers, S. V.; Kürster, M.; Lafarga, M.; Morales, J. C.; Passegger,
V. M.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2020sea..confE.156M
Altcode:
We aim to review the equivalent width (EW) method and the spectral
synthesis technique to derive stellar atmospheric parameters of
FGKM-type stars in light of the optical and near-infrared spectra
obtained with CARMENES, the high-resolution, double-channel
spectrograph installed at the 3.5 m telescope at the Calar Alto
Observatory (Almería, Spain). On the one hand, we show the results
for 65 FGK-type stars observed with CARMENES and analysed with the
S TE P AR code, a Python implementation of the EW method, placing
special emphasis on the impact of the near-infrared wavelength region
on the parameter computations. On the other hand, we also highlight
the stellar atmospheric parameters obtained for the target M dwarfs in
the CARMENES Guaranteed Time Observations (GTO) programme by means of
the spectral synthesis technique as implemented in the SteParSyn code.
Title: Kinematics of M dwarfs in the CARMENES input catalogue
Authors: Cortés-Contreras, M.; Domínguez-Fernández, A. J.;
Caballero, J. A.; Montes, D.; Cardona, C.; Béjar, V. J. S.;
Cifuentes, C.; Tabernero, H. M.; Zapatero Osorio, M. R.; Bailer-Jones,
C. A. L. J.; Gallardo, I.; Jeffers, S. V.; Lafarga, M.; Lodieu, N.;
Schöfer, P.; Schweitzer, A.; Solano, E.; Ribas, I.; Reiners, A.;
Quirrenbach, A.; Amado, P. J.; Azzaro, M.; Hatzes, A. P.; Henning,
T.; Kürster, M.; Seifert, W.
Bibcode: 2020sea..confE.131C
Altcode:
We aim to determine the kinematics of the cool dwarfs in the CARMENES
input catalogue (Carmencita) and to identify young active stars, in
the frame of the targets characterization of the CARMENES exoplanet
survey. We compiled or computed proper motions and distances for 2191
M dwarfs and three K dwarfs, as well as radial velocities for 1475
single stars. With the derived Galactocentric velocities, we placed
the 1475 dwarfs into the different Galactic populations including
Eggen's young disc. We also associated over 300 stars to stellar
kinematic groups younger than 600 Ma. We compiled or measured pEW(Hα),
Prot, v sin i, X-rays, NUV and J magnitudes and defined five
spectral-type-dependent activity and rotation criteria that confirmed
young (t≤600 Ma) cool dwarfs satisfy. Among the 1475 dwarfs, we
identified 36 M0-M5 dwarfs that fulfill our youth criteria. Some of
them have not stellar kinematic group association but belong to the
Galactic young disc.
Title: Identifying activity-sensitive spectral lines in the CARMENES
VIS and NIR spectral range of M dwarfs
Authors: Montes, D.; López-Gallifa, A.; Labarga, F.; Caballero, J. A.;
Marfil, E.; Tabernero, H. M.; Lafarga, M.; Jeffers, S. V.; Ribas,
I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; CARMENES Consortium
Bibcode: 2020sea..confE.168M
Altcode:
We use visible and near-infrared CARMENES spectra of M dwarfs to search
for chromospheric activity-sensitive spectral lines in addition to
the well known Na I D1, D2 He I D3 , Hα, and Ca II IRT lines, He I
10830 Å, Paγ and Paβ lines. To identify lines with a significant
chromospheric contribution we have used the spectral subtraction
technique. We confirm the new activity-sensitive lines analysing the
correlation with the other well known activity indicators in the same
spectra and their temporal evolution in two particular active stars
with strong flares EV Lac and YZ CMi. In addition, we analyse line
by line the template spectrum (co-added of all the individual spectra
available) of these two stars using also the spectral subtraction to
search for magnetically-sensitive lines, that is lines with detectable
Zeeman broadening. These two selection of lines will be used to check
the influence in spectral region used to derive radial velocities (RV)
and help to solve the problem of stellar activity in RV measurements
to search for exoplanets around these stars.
Title: Precise mass and radius of a transiting super-Earth planet
orbiting the M dwarf TOI-1235: a planet in the radius gap?
Authors: Bluhm, P.; Luque, R.; Espinoza, N.; Pallé, E.; Caballero,
J. A.; Dreizler, S.; Livingston, J. H.; Mathur, S.; Quirrenbach,
A.; Stock, S.; Van Eylen, V.; Nowak, G.; López, E. D.; Csizmadia,
Sz.; Zapatero Osorio, M. R.; Schöfer, P.; Lillo-Box, J.; Oshagh, M.;
González-Álvarez, E.; Amado, P. J.; Barrado, D.; Béjar, V. J. S.;
Cale, B.; Chaturvedi, P.; Cifuentes, C.; Cochran, W. D.; Collins,
K. A.; Collins, K. I.; Cortés-Contreras, M.; Díez Alonso, E.; El
Mufti, M.; Ercolino, A.; Fridlund, M.; Gaidos, E.; García, R. A.;
Georgieva, I.; González-Cuesta, L.; Guerra, P.; Hatzes, A. P.;
Henning, Th.; Herrero, E.; Hidalgo, D.; Isopi, G.; Jeffers, S. V.;
Jenkins, J. M.; Jensen, E. L. N.; Kábath, P.; Kaminski, A.; Kemmer,
J.; Korth, J.; Kossakowski, D.; Kürster, M.; Lafarga, M.; Mallia,
F.; Montes, D.; Morales, J. C.; Morales-Calderón, M.; Murgas, F.;
Narita, N.; Passegger, V. M.; Pedraz, S.; Persson, C. M.; Plavchan,
P.; Rauer, H.; Redfield, S.; Reffert, S.; Reiners, A.; Ribas, I.;
Ricker, G. R.; Rodríguez-López, C.; Santos, A. R. G.; Seager, S.;
Schlecker, M.; Schweitzer, A.; Shan, Y.; Soto, M. G.; Subjak, J.;
Tal-Or, L.; Trifonov, T.; Vanaverbeke, S.; Vanderspek, R.; Wittrock,
J.; Zechmeister, M.; Zohrabi, F.
Bibcode: 2020A&A...639A.132B
Altcode: 2020arXiv200406218B
We report the confirmation of a transiting planet around the bright
weakly active M0.5 V star TOI-1235 (TYC 4384-1735-1, V ≈ 11.5 mag),
whose transit signal was detected in the photometric time series
of sectors 14, 20, and 21 of the TESS space mission. We confirm the
planetary nature of the transit signal, which has a period of 3.44
d, by using precise RV measurements with the CARMENES, HARPS-N,
and iSHELL spectrographs, supplemented by high-resolution imaging
and ground-based photometry. A comparison of the properties derived
for TOI-1235 b with theoretical models reveals that the planet has
a rocky composition, with a bulk density slightly higher than that
of Earth. In particular, we measure a mass of Mp = 5.9
± 0.6 M⊕ and a radius of Rp = 1.69 ± 0.08
R⊕, which together result in a density of ρp
= 6.7- 1.1+ 1.3 g cm-3. When compared
with other well-characterized exoplanetary systems, the particular
combination of planetary radius and mass places our discovery in the
radius gap, which is a transition region between rocky planets and
planets with significant atmospheric envelopes. A few examples of
planets occupying the radius gap are known to date. While the exact
location of the radius gap for M dwarfs is still a matter of debate,
our results constrain it to be located at around 1.7 R⊕
or larger at the insolation levels received by TOI-1235 b (~60
S⊕). This makes it an extremely interesting object for
further studies of planet formation and atmospheric evolution.
Title: The CARMENES search for exoplanets around M dwarfs. Dynamical
characterization of the multiple planet system GJ 1148 and prospects
of habitable exomoons around GJ 1148 b
Authors: Trifonov, T.; Lee, M. H.; Kürster, M.; Henning, Th.; Grishin,
E.; Stock, S.; Tjoa, J.; Caballero, J. A.; Wong, K. H.; Bauer, F. F.;
Quirrenbach, A.; Zechmeister, M.; Ribas, I.; Reffert, S.; Reiners,
A.; Amado, P. J.; Kossakowski, D.; Azzaro, M.; Béjar, V. J. S.;
Cortés-Contreras, M.; Dreizler, S.; Hatzes, A. P.; Jeffers, S. V.;
Kaminski, A.; Lafarga, M.; Montes, D.; Morales, J. C.; Pavlov, A.;
Rodríguez-López, C.; Schmitt, J. H. M. M.; Solano, E.; Barnes, R.
Bibcode: 2020A&A...638A..16T
Altcode: 2020arXiv200200906T
Context. GJ 1148 is an M-dwarf star hosting a planetary system composed
of two Saturn-mass planets in eccentric orbits with periods of 41.38
and 532.02 days.
Aims: We reanalyze the orbital configuration
and dynamics of the GJ 1148 multi-planetary system based on new precise
radial velocity measurements taken with CARMENES.
Methods: We
combined new and archival precise Doppler measurements from CARMENES
with those available from HIRES for GJ 1148 and modeled these data
with a self-consistent dynamical model. We studied the orbital
dynamics of the system using the secular theory and direct N-body
integrations. The prospects of potentially habitable moons around GJ
1148 b were examined.
Results: The refined dynamical analyses
show that the GJ 1148 system is long-term stable in a large phase-space
of orbital parameters with an orbital configuration suggesting apsidal
alignment, but not in any particular high-order mean-motion resonant
commensurability. GJ 1148 b orbits inside the optimistic habitable zone
(HZ). We find only a narrow stability region around the planet where
exomoons can exist. However, in this stable region exomoons exhibit
quick orbital decay due to tidal interaction with the planet.
Conclusions: The GJ 1148 planetary system is a very rare M-dwarf
planetary system consisting of a pair of gas giants, the inner of
which resides in the HZ. We conclude that habitable exomoons around
GJ 1148 b are very unlikely to exist.
Title: SERVAL: SpEctrum Radial Velocity AnaLyser
Authors: Zechmeister, M.; Reiners, A.; Amado, P. J.; Azzaro, M.;
Bauer, F. F.; Béjar, V. J. S.; Caballero, J. A.; Guenther, E. W.;
Hagen, H. -J.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Launhardt,
R.; Montes, D.; Morales, J. C.; Quirrenbach, A.; Reffert, S.; Ribas,
I.; Seifert, W.; Tal-Or, L. Wolthoff, V.
Bibcode: 2020ascl.soft06011Z
Altcode:
SERVAL calculates radial velocities (RVs) from stellar spectra. The
code uses least-squares fitting algorithms to derive the RVs and
additional spectral diagnostics. Forward modeling in pixel space is
used to properly weight pixel errors, and the stellar templates are
reconstructed from the observations themselves to make optimal use of
the RV information inherent in the stellar spectra.
Title: VizieR Online Data Catalog: M dwarfs HeI infrared triplet
variability (Fuhrmeister+, 2020)
Authors: Fuhrmeister, B.; Czesla, S.; Hildebrandt, L.; Nagel, E.;
Schmitt, J. H. M. M.; Jeffers, S. V.; Caballero, J. A.; Hintz, D.;
Johnson, E. N.; Schoefer, P.; Zechmeister, M.; Reiners, A.; Ribas,
I.; Amado, P. J.; Quirrenbach, A.; Nortmann, L.; Bauer, F. F.; Bejar,
V. J. S.; Cortes-Contreras, M.; Dreizler, S.; Galadi-Enriquez, D.;
Hatzes, A. P.; Kaminski, A.; Kuerster, M.; Lafarga, M.; Montes, D.
Bibcode: 2020yCat..36400052F
Altcode:
The HeI infrared (IR) triplet at 10830Å is known as an activity
indicator and has become a primary diagnostic in exoplanetary
transmission spectroscopy. The HeI IR lines are a tracer of the
stellar extreme-ultraviolet irradiation from the transition region
and corona. We study the variability of the HeI IR triplet lines in
spectral time series of 319 M dwarf stars, obtained with the CARMENES
spectrograph. We measure the pseudo-equivalent width (pEW) in each
stellar spectrum. The integration ranges for the line and the reference
bands are found in Table 1 of the paper. For comparison purposes
we also measure pEW values of Hα, the bluest CaII IR triplet line,
and the HeI D3 line. From these measurements we compute the
mean pEW, the median absolute deviation (MAD) and Pearson's correlation
coefficients for the lines. (1 data file).
Title: A multiplanet system of super-Earths orbiting the brightest
red dwarf star GJ 887
Authors: Jeffers, S. V.; Dreizler, S.; Barnes, J. R.; Haswell, C. A.;
Nelson, R. P.; Rodríguez, E.; López-Gonz‧lez, M. J.; Morales, N.;
Luque, R.; Zechmeister, M.; Vogt, S. S.; Jenkins, J. S.; Palle, E.;
Berdi ñas, Z. M.; Coleman, G. A. L.; Díaz, M. R.; Ribas, I.; Jones,
H. R. A.; Butler, R. P.; Tinney, C. G.; Bailey, J.; Carter, B. D.;
O'Toole, S.; Wittenmyer, R. A.; Crane, J. D.; Feng, F.; Shectman,
S. A.; Teske, J.; Reiners, A.; Amado, P. J.; Anglada-Escudé, G.
Bibcode: 2020Sci...368.1477J
Altcode: 2020arXiv200616372J
The closet exoplanets to the Sun provide opportunities for detailed
characterization of planets outside the Solar System. We report
the discovery, using radial velocity measurements, of a compact
multiplanet system of super-Earth exoplanets orbiting the nearby red
dwarf star GJ 887. The two planets have orbital periods of 9.3 and
21.8 days. Assuming an Earth-like albedo, the equilibrium temperature
of the 21.8-day planet is ~350 kelvin. The planets are interior to,
but close to the inner edge of, the liquid-water habitable zone. We
also detect an unconfirmed signal with a period of ~50 days, which
could correspond to a third super-Earth in a more temperate orbit. Our
observations show that GJ 887 has photometric variability below 500
parts per million, which is unusually quiet for a red dwarf.
Title: The CARMENES search for exoplanets around M dwarfs. The He
I infrared triplet lines in PHOENIX models of M 2-3 V stars
Authors: Hintz, D.; Fuhrmeister, B.; Czesla, S.; Schmitt,
J. H. M. M.; Schweitzer, A.; Nagel, E.; Johnson, E. N.; Caballero,
J. A.; Zechmeister, M.; Jeffers, S. V.; Reiners, A.; Ribas, I.; Amado,
P. J.; Quirrenbach, A.; Anglada-Escudé, G.; Bauer, F. F.; Béjar,
V. J. S.; Cortés-Contreras, M.; Dreizler, S.; Galadí-Enríquez,
D.; Guenther, E. W.; Hauschildt, P. H.; Kaminski, A.; Kürster, M.;
Lafarga, M.; López del Fresno, M.; Montes, D.; Morales, J. C.
Bibcode: 2020A&A...638A.115H
Altcode: 2020arXiv200506246H
The He I infrared (IR) line at a vacuum wavelength of 10 833 Å is a
diagnostic for the investigation of atmospheres of stars and planets
orbiting them. For the first time, we study the behavior of the He I
IR line in a set of chromospheric models for M-dwarf stars, whose much
denser chromospheres may favor collisions for the level population over
photoionization and recombination, which are believed to be dominant
in solar-type stars. For this purpose, we use published PHOENIX
models for stars of spectral types M2 V and M3 V and also compute new
series of models with different levels of activity following an ansatz
developed for the case of the Sun. We perform a detailed analysis of
the behavior of the He I IR line within these models. We evaluate the
line in relation to other chromospheric lines and also the influence
of the extreme ultraviolet (EUV) radiation field. The analysis of the
He I IR line strengths as a function of the respective EUV radiation
field strengths suggests that the mechanism of photoionization and
recombination is necessary to form the line for inactive models, while
collisions start to play a role in our most active models. Moreover,
the published model set, which is optimized in the ranges of the Na
I D2, Hα, and the bluest Ca II IR triplet line, gives an
adequate prediction of the He I IR line for most stars of the stellar
sample. Because especially the most inactive stars with weak He I IR
lines are fit worst by our models, it seems that our assumption of
a 100% filling factor of a single inactive component no longer holds
for these stars.
Title: The CARMENES search for exoplanets around M dwarfs. A
super-Earth planet orbiting HD 79211 (GJ 338 B)
Authors: González-Álvarez, E.; Zapatero Osorio, M. R.; Caballero,
J. A.; Sanz-Forcada, J.; Béjar, V. J. S.; González-Cuesta, L.;
Dreizler, S.; Bauer, F. F.; Rodríguez, E.; Tal-Or, L.; Zechmeister,
M.; Montes, D.; López-González, M. J.; Ribas, I.; Reiners, A.;
Quirrenbach, A.; Amado, P. J.; Anglada-Escudé, G.; Azzaro, M.;
Cortés-Contreras, M.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.;
Kaminski, A.; Kürster, M.; Lafarga, M.; Morales, J. C.; Pallé, E.;
Perger, M.; Schmitt, J. H. M. M.
Bibcode: 2020A&A...637A..93G
Altcode: 2020arXiv200313052G
Aims: We report on radial velocity time series for two M0.0
V stars, GJ 338 B and GJ 338 A, using the CARMENES spectrograph,
complemented by ground-telescope photometry from Las Cumbres and
Sierra Nevada observatories. We aim to explore the presence of small
planets in tight orbits using the spectroscopic radial velocity
technique.
Methods: We obtained 159 and 70 radial velocity
measurements of GJ 338 B and A, respectively, with the CARMENES
visible channel between 2016 January and 2018 October. We also
compiled additional relative radial velocity measurements from the
literature and a collection of astrometric data that cover 200 a of
observations to solve for the binary orbit.
Results: We found
dynamical masses of 0.64 ± 0.07 M⊙ for GJ 338 B and 0.69
± 0.07 M⊙ for GJ 338 A. The CARMENES radial velocity
periodograms show significant peaks at 16.61 ± 0.04 d (GJ 338 B) and
16.3-1.3+3.5 d (GJ 338 A), which have counterparts
at the same frequencies in CARMENES activity indicators and photometric
light curves. We attribute these to stellar rotation. GJ 338 B shows
two additional, significant signals at 8.27 ± 0.01 and 24.45 ± 0.02
d, with no obvious counterparts in the stellar activity indices. The
former is likely the first harmonic of the star's rotation, while we
ascribe the latter to the existence of a super-Earth planet with a
minimum mass of 10.27-1.38+1.47 M⊕
orbiting GJ 338 B. We have not detected signals of likely planetary
origin around GJ 338 A.
Conclusions: GJ 338 Bb lies inside
the inner boundary of the habitable zone around its parent star. It
is one of the least massive planets ever found around any member
of stellar binaries. The masses, spectral types, brightnesses,
and even the rotational periods are very similar for both stars,
which are likely coeval and formed from the same molecular cloud, yet
they differ in the architecture of their planetary systems. Full
Tables B.1-B.6 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/cat/J/A+A/637/A93
Title: The CARMENES search for exoplanets around M
dwarfs. Characterization of the nearby ultra-compact multiplanetary
system YZ Ceti
Authors: Stock, S.; Kemmer, J.; Reffert, S.; Trifonov, T.; Kaminski,
A.; Dreizler, S.; Quirrenbach, A.; Caballero, J. A.; Reiners,
A.; Jeffers, S. V.; Anglada-Escudé, G.; Ribas, I.; Amado, P. J.;
Barrado, D.; Barnes, J. R.; Bauer, F. F.; Berdiñas, Z. M.; Béjar,
V. J. S.; Coleman, G. A. L.; Cortés-Contreras, M.; Díez-Alonso, E.;
Domínguez-Fernández, A. J.; Espinoza, N.; Haswell, C. A.; Hatzes,
A.; Henning, T.; Jenkins, J. S.; Jones, H. R. A.; Kossakowski, D.;
Kürster, M.; Lafarga, M.; Lee, M. H.; López González, M. J.; Montes,
D.; Morales, J. C.; Morales, N.; Pallé, E.; Pedraz, S.; Rodríguez,
E.; Rodríguez-López, C.; Zechmeister, M.
Bibcode: 2020A&A...636A.119S
Altcode: 2020arXiv200201772S
Context. The nearby ultra-compact multiplanetary system YZ Ceti consists
of at least three planets, and a fourth tentative signal. The orbital
period of each planet is the subject of discussion in the literature
due to strong aliasing in the radial velocity data. The stellar
activity of this M dwarf also hampers significantly the derivation
of the planetary parameters.
Aims: With an additional 229
radial velocity measurements obtained since the discovery publication,
we reanalyze the YZ Ceti system and resolve the alias issues.
Methods: We use model comparison in the framework of Bayesian statistics
and periodogram simulations based on a method by Dawson and Fabrycky
to resolve the aliases. We discuss additional signals in the RV data,
and derive the planetary parameters by simultaneously modeling the
stellar activity with a Gaussian process regression model. To constrain
the planetary parameters further we apply a stability analysis on our
ensemble of Keplerian fits.
Results: We find no evidence for a
fourth possible companion. We resolve the aliases: the three planets
orbit the star with periods of 2.02 d, 3.06 d, and 4.66 d. We also
investigate an effect of the stellar rotational signal on the derivation
of the planetary parameters, in particular the eccentricity of the
innermost planet. Using photometry we determine the stellar rotational
period to be close to 68 d and we also detect this signal in the
residuals of a three-planet fit to the RV data and the spectral activity
indicators. From our stability analysis we derive a lower limit on the
inclination of the system with the assumption of coplanar orbits which
is imin = 0.9 deg. From the absence of a transit event with
TESS, we derive an upper limit of the inclination of imax =
87.43 deg.
Conclusions: YZ Ceti is a prime example of a system
where strong aliasing hindered the determination of the orbital
periods of exoplanets. Additionally, stellar activity influences
the derivation of planetary parameters and modeling them correctly
is important for the reliable estimation of the orbital parameters
in this specific compact system. Stability considerations then allow
additional constraints to be placed on the planetary parameters. Table B.1 is 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/cat/J/A+A/636/A119.
Title: The CARMENES search for exoplanets around M dwarfs. Radial
velocities and activity indicators from cross-correlation functions
with weighted binary masks
Authors: Lafarga, M.; Ribas, I.; Lovis, C.; Perger, M.; Zechmeister,
M.; Bauer, F. F.; Kürster, M.; Cortés-Contreras, M.; Morales,
J. C.; Herrero, E.; Rosich, A.; Baroch, D.; Reiners, A.; Caballero,
J. A.; Quirrenbach, A.; Amado, P. J.; Alacid, J. M.; Béjar, V. J. S.;
Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski,
A.; Montes, D.; Pedraz, S.; Rodríguez-López, C.; Schmitt, J. H. M. M.
Bibcode: 2020A&A...636A..36L
Altcode: 2020arXiv200307471L
Context. For years, the standard procedure to measure radial velocities
(RVs) of spectral observations consisted in cross-correlating the
spectra with a binary mask, that is, a simple stellar template that
contains information on the position and strength of stellar absorption
lines. The cross-correlation function (CCF) profiles also provide
several indicators of stellar activity.
Aims: We present a
methodology to first build weighted binary masks and, second, to
compute the CCF of spectral observations with these masks from which
we derive radial velocities and activity indicators. These methods
are implemented in a python code that is publicly available.
Methods: To build the masks, we selected a large number of sharp
absorption lines based on the profile of the minima present in high
signal-to-noise ratio (S/N) spectrum templates built from observations
of reference stars. We computed the CCFs of observed spectra and
derived RVs and the following three standard activity indicators:
full-width-at-half-maximum as well as contrast and bisector inverse
slope.
Results: We applied our methodology to CARMENES
high-resolution spectra and obtain RV and activity indicator time
series of more than 300 M dwarf stars observed for the main CARMENES
survey. Compared with the standard CARMENES template matching pipeline,
in general we obtain more precise RVs in the cases where the template
used in the standard pipeline did not have enough S/N. We also show
the behaviour of the three activity indicators for the active star YZ
CMi and estimate the absolute RV of the M dwarfs analysed using the CCF
RVs. Table A.1 is 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/cat/J/A+A/636/A36
Title: VizieR Online Data Catalog: Absolute radial velocities of
CARMENES M dwarfs (Lafarga+, 2020)
Authors: Lafarga, M.; Ribas, I.; Lovis, C.; Perger, M.; Zechmeister,
M.; Bauer, F. F.; Kuerster, M.; Cortes-Contreras, M.; Morales,
J. C.; Herrero, E.; Rosich, A.; Baroch, D.; Reiners, A.; Caballero,
J. A.; Quirrenbach, A.; Amado, P. J.; Alacid, J. M.; Bejar, V. J. S.;
Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski,
A.; Montes, D.; Pedraz, S.; Rodriguez-Lopez, C.; Schmitt, J. H. M. M.
Bibcode: 2020yCat..36360036L
Altcode:
Absolute radial velocities (RVs) of 323 M dwarf stars observed with
CARMENES. The RVs were computed using the cross-correlation function
(CCF) method with binary masks on CARMENES visual observations. The
RV values and uncertainties also take into account the gravitational
redshift and the convective blueshift of the stars. The gravitational
redshift is computed using mass and radius values from Schweitzer
et al., 2019A&A...625A..68S, Cat. J/A+A/625/A68. We consider the
convective blueshift to be 0+/-100m/s for all stars. (1 data file).
Title: VizieR Online Data Catalog: HD 79211 CARMENES radial velocities
(Gonzalez-Alvarez+, 2020)
Authors: Gonzalez-Alvarez, E.; Zapatero Osorio, M. R.; Caballero,
J. A.; Sanz-Forcada, J.; Bejar, V. J. S.; Gonzalez-Cuesta, L.;
Dreizler, S.; Bauer, F. F.; Rodriguez, E.; Tal-Or, L.; Zechmeister, M.;
Montes, D.; Lopez-Gonzalez, M. J.; Ribas, I.; Reiners, A.; Quirrenbach,
A.; Amado, P. J.; Anglada-Escude, G.; Azzaro, M.; Cortes-Contreras, M.;
Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Kuerster,
M.; Lafarga, M.; Morales, J. C.; Palle, E.; Perger, M.; Schmitt,
J. H. M. M.
Bibcode: 2020yCat..36370093G
Altcode:
Detailed CARMENES RV analysis of the M0.0 V stars GJ 338 A (HD 79210)
and GJ 338 B (HD 79211), a wide binary system with similar mass stellar
components. New RVs were obtained for each member of the stellar
binary using the CARMENES fibre-fed, echelle spectrograph. CARMENES
is installed at the 3.5m telescope of the Calar Alto Observatory in
Almeria (Spain). (6 data files).
Title: Measuring stellar magnetic helicity density
Authors: Lund, K.; Jardine, M.; Lehmann, L. T.; Mackay, D. H.; See,
V.; Vidotto, A. A.; Donati, J. -F.; Fares, R.; Folsom, C. P.; Jeffers,
S. V.; Marsden, S. C.; Morin, J.; Petit, P.
Bibcode: 2020MNRAS.493.1003L
Altcode: 2020arXiv200111749L; 2020MNRAS.tmp..292L
Helicity is a fundamental property of a magnetic field but to date
it has only been possible to observe its evolution in one star -
the Sun. In this paper, we provide a simple technique for mapping
the large-scale helicity density across the surface of any star using
only observable quantities: the poloidal and toroidal magnetic field
components (which can be determined from Zeeman-Doppler imaging) and
the stellar radius. We use a sample of 51 stars across a mass range of
0.1-1.34 M⊙ to show how the helicity density relates to
stellar mass, Rossby number, magnetic energy, and age. We find that the
large-scale helicity density increases with decreasing Rossby number
Ro, peaking at Ro ≃ 0.1, with a saturation or
decrease below that. For both fully and partially convective stars,
we find that the mean absolute helicity density scales with the mean
squared toroidal magnetic flux density according to the power law: |<
{h }> | ∝ < {{{B}_{tor}}^2_{} > }^{0.86 ± 0.04}. The scatter
in this relation is consistent with the variation across a solar cycle,
which we compute using simulations and observations across solar cycles
23 and 24, respectively. We find a significant decrease in helicity
density with age.
Title: Stellar atmospheric parameters of FGK-type stars from
high-resolution optical and near-infrared CARMENES spectra
Authors: Marfil, E.; Tabernero, H. M.; Montes, D.; Caballero, J. A.;
Soto, M. G.; González Hernández, J. I.; Kaminski, A.; Nagel, E.;
Jeffers, S. V.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Amado, P. J.
Bibcode: 2020MNRAS.492.5470M
Altcode: 2020arXiv200101495M; 2020MNRAS.tmp...64M
With the purpose of assessing classic spectroscopic methods on
high-resolution and high signal-to-noise ratio spectra in the
near-infrared wavelength region, we selected a sample of 65 F-,
G-, and K-type stars observed with CARMENES, the new, ultra-stable,
double-channel spectrograph at the 3.5 m Calar Alto telescope. We
computed their stellar atmospheric parameters (Teff, log g,
ξ, and [Fe/H]) by means of the STEPAR code, a PYTHON implementation
of the equivalent width method that employs the 2017 version of the
MOOG code and a grid of MARCS model atmospheres. We compiled four Fe I
and Fe II line lists suited to metal-rich dwarfs, metal-poor dwarfs,
metal-rich giants, and metal-poor giants that cover the wavelength
range from 5300 to 17 100 Å, thus substantially increasing the number
of identified Fe I and Fe II lines up to 653 and 23, respectively. We
examined the impact of the near-infrared Fe I and Fe II lines upon
our parameter determinations after an exhaustive literature search,
placing special emphasis on the 14 Gaia benchmark stars contained in
our sample. Even though our parameter determinations remain in good
agreement with the literature values, the increase in the number of Fe
I and Fe II lines when the near-infrared region is taken into account
reveals a deeper Teff scale that might stem from a higher
sensitivity of the near-infrared lines to Teff.
Title: VizieR Online Data Catalog: GJ 3512 radial velocity and light
curves (Morales+, 2019)
Authors: Morales, J. C.; Mustill, A. J.; Ribas, I.; Davies, M. B.;
Reiners, A.; Bauer, F. F.; Kossakowski, D.; Herrero, E.; Rodriguez,
E.; Lopez-Gonzalez, M. J.; Rodriguez-Lopez, C.; Bejar, V. J. S.;
Gonzalez-Cuesta, L.; Luque, R.; Palle, E.; Perger, M.; Baroch,
D.; Johansen, A.; Klahr, H.; Mordasini, C.; Anglada-Escude, G.;
Caballero, J. A.; Cortes-Contreras, M.; Dreizler, S.; Lafarga, M.;
Nagel, E.; Passegger, V. M.; Reffert, S.; Rosich, A.; Schweitzer,
A.; Tal-Or, L.; Trifonov, T.; Zechmeister, M.; Quirrenbach, A.;
Amado, P. J.; Guenther, E. W.; Hagen, H. -J.; Henning, T.; Jeffers,
S. V.; Kaminski, A.; Kurster, M.; Montes, D.; Seifert, W.; Abellan,
F. J.; Abril, M.; Aceituno, J.; Aceituno, F. J.; Alonso-Floriano,
F. J.; Ammler-von Eiff, M.; Antona, R.; Arroyo-Torres, B.; Azzaro,
M.; Barrado, D.; Becerril-Jarque, S.; Benitez, D.; Berdinas, Z. M.;
Bergond, G.; Brinkmoller, M.; Del Burgo, C.; Burn, R.; Calvo-Ortega,
R.; Cano, J.; Cardenas, M. C.; Cardona Guillen, C.; Carro, J.; Casal,
E.; Casanova, V.; Casasayas-Barris, N.; Chaturvedi, P.; Cifuentes,
C.; Claret, A.; Colome, J.; Czesla, S.; Diez-Alonso, E.; Dorda, R.;
Emsenhuber, A.; Fernandez, M.; Fernandez-Martin, A.; Ferro, I. M.;
Fuhrmeister, B.; Galadi-Enriquez, D.; Gallardo Cava, I.; Garcia Vargas,
M. L.; Garcia-Piquer, A.; Gesa, L.; Gonzalez-Alvarez, E.; Gonzalez
Hernandez, J. I.; Gonzalez-Peinado, R.; Guardia, J.; Guijarro, A.;
de Guindos, E.; Hatzes, A. P.; Hauschildt, P. H.; Hedrosa, R. P.;
Hermelo, I.; Hernandez Arabi, R.; Hernandez, Otero F.; Hintz, D.;
Holgado, G.; Huber, A.; Huke, P.; Johnson, E. N.; de Juan, E.; Kehr,
M.; Kemmer, J.; Kim, M.; Kluter, J.; Klutsch, A.; Labarga, F.; Labiche,
N.; Lalitha, S.; Lampon, M.; Lara, L. M.; Launhardt, R.; Lazaro,
F. J.; Lizon, J. -L.; Llamas, M.; Lodieu, N.; Lopez Del Fresno, M.;
Lopez Salas, J. F.; Lopez-Santiago, J.; Magan Madinabeitia, H.; Mall,
U.; Mancini, L.; Mandel, H.; Marfil, E.; Marin Molina, J. A.; Martin,
E. L.; Martin-Fernandez, P.; Martin-Ruiz, S.; Martinez-Rodriguez,
H.; Marvin, C. J.; Mirabet, E.; Moya, A.; Naranjo, V.; Nelson, R. P.;
Nortmann, L.; Nowak, G.; Ofir, A.; Pascual, J.; Pavlov, A.; Pedraz,
S.; Perez Medialde, A. D.; Perez-Calpena, A.; Perryman, M. A. C.;
Rabaza, O.; Ramon Ballesta, A.; Rebolo, R.; Redondo, P.; Rix, H. -W.;
Rodler, F.; Rodriguez Trinidad, A.; Sabotta, S.; Sadegi, S.; Salz,
M.; Sanchez-Blanco, E.; Sanchez Carrasco, M. A.; Sanchez-Lopez, A.;
Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schafer, S.; Schlecker,
M.; Schmitt, J. H. M. M.; Schofer, P.; Solano, E.; Sota, A.; Stahl, O.;
Stock, S.; Stuber, T.; Sturmer, J.; Suarez, J. C.; Tabernero, H. M.;
Tulloch, S. M.; Veredas, G.; Vico-Linares, J. I.; Vilardell, F.;
Wagner, K.; Winkler, J.; Wolthoff, V.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2020yCatp021036502M
Altcode:
These tables list the radial velocities measured with the
visual (VIS) and near-infrared (NIR) channels of the CARMENES
spectrograph (Quirrenbach et al. 2018SPIE10702E..0WQ), and the
stellar activity indices computed with SERVAL (Zechmeister et
al. 2018A&A...609A..12Z). Photometry obtained from the Montsec,
Sierra Nevada, and las Cumbres observatories is also listed here as
used in the paper. (4 data files).
Title: RedDots: a temperate 1.5 Earth-mass planet candidate in a
compact multiterrestrial planet system around GJ 1061
Authors: Dreizler, S.; Jeffers, S. V.; Rodríguez, E.; Zechmeister, M.;
Barnes, J. R.; Haswell, C. A.; Coleman, G. A. L.; Lalitha, S.; Hidalgo
Soto, D.; Strachan, J. B. P.; Hambsch, F. -J.; López-González,
M. J.; Morales, N.; Rodríguez López, C.; Berdiñas, Z. M.; Ribas,
I.; Pallé, E.; Reiners, A.; Anglada-Escudé, G.
Bibcode: 2020MNRAS.493..536D
Altcode: 2019arXiv190804717D; 2020MNRAS.tmp..235D
Small low-mass stars are favourable targets for the detection
of rocky habitable planets. In particular, planetary systems in
the solar neighbourhood are interesting and suitable for precise
characterization. The RedDots campaigns seek to discover rocky planets
orbiting nearby low-mass stars. The 2018 campaign targeted GJ 1061,
which is the 20th nearest star to the Sun. For three consecutive months
we obtained nightly, high-precision radial velocity measurements with
the HARPS spectrograph. We analysed these data together with archival
HARPS data. We report the detection of three planet candidates with
periods of 3.204 ± 0.001, 6.689 ± 0.005, and 13.03 ± 0.03 d,
which are close to 1:2:4 period commensurability. After several
considerations related to the properties of the noise and sampling,
we conclude that a fourth signal is most likely explained by stellar
rotation, although it may be due to a planet. The proposed three-planet
system (and the potential four-planet solution) is long-term dynamically
stable. Planet-planet gravitational interactions are below our current
detection threshold. The minimum masses of the three planets range from
1.4 ± 0.2 to 1.8 ± 0.3 M⊕. Planet d, with msin I = 1.64
± 0.24 M⊕, receives a similar amount of energy as Earth
receives from the Sun. Consequently it lies within the liquid-water
habitable zone of the star and has a similar equilibrium temperature
to Earth. GJ 1061 has very similar properties to Proxima Centauri but
activity indices point to lower levels of stellar activity.
Title: The CARMENES search for exoplanets around M
dwarfs. Photospheric parameters of target stars from high-resolution
spectroscopy. II. Simultaneous multi-wavelength range modeling of
activity insensitive lines (Corrigendum)
Authors: Passegger, V. M.; Schweitzer, A.; Shulyak, D.; Nagel, E.;
Hauschildt, P. H.; Reiners, A.; Amado, P. J.; Caballero, J. A.;
Cortés-Contreras, M.; Domínguez-Fernández, A. J.; Quirrenbach,
A.; Ribas, I.; Azzaro, M.; Anglada-Escudé, G.; Bauer, F. F.; Béjar,
V. J. S.; Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers, S. V.;
Kaminski, A.; Kürster, M.; Lafarga, M.; Martín, E. L.; Montes, D.;
Morales, J. C.; Schmitt, J. H. M. M.; Zechmeister, M.
Bibcode: 2020A&A...634C...2P
Altcode:
No abstract at ADS
Title: VizieR Online Data Catalog: YZ Ceti CARMENES and HARPS radial
velocity curve (Stock+, 2020)
Authors: Stock, S.; Kemmer, J.; Reffert, S.; Trifonov, T.; Kaminski,
A.; Dreizler, S.; Quirrenbach, A.; Caballero, J. A.; Reiners,
A.; Jeffers, S. V.; Anglada-Escude, G.; Ribas, I.; Amado, P. J.;
Barrado, D.; Barnes, J. R.; Bauer, F. F.; Berdinas, Z. M.; Bejar,
V. J. S.; Coleman, G. A. L.; Cortes-Contreras, M.; Diez-Alonso, E.;
Dominguez-Fernandez, A. J.; Espinoza, N.; Haswell, C. A.; Hatzes,
A.; Henning, T.; Jenkins, J. S.; Jones, H. R. A.; Kossakowski, D.;
Kuerster, M.; Lafarga, M.; Lee, M. H.; Lopez Gonzalez, M. J.; Montes,
D.; Morales, J. C.; Morales, N.; Palle, E.; Pedraz, S.; Rodriguez,
E.; Rodriguez-Lopez, C.; Zechmeister, M.
Bibcode: 2020yCat..36360119S
Altcode:
We acquired spectra with CARMENES (Quirrenbach et al., 2014, in
Proc. SPIE, Vol. 9147, Ground-based and Airborne Instrumentation for
Astronomy V, 91471F), a high-resolution precise echelle spectrograph
mounted at the 3.5m telescope at the Calar Alto Observatory in Spain. We
combined this data with 334 high-resolution spectra from HARPS, of which
59 were collected by the Red Dots program (Dreizler et al., 2019, arXiv
e-prints, arXiv:1908.04717) and the remaining by Astudillo-Defru et
al. (2017A&A...605L..11A, Cat. J/A+A/605/L11). (1 data file).
Title: Do Non-dipolar Magnetic Fields Contribute to Spin-down Torques?
Authors: See, Victor; Matt, Sean P.; Finley, Adam J.; Folsom, Colin P.;
Boro Saikia, Sudeshna; Donati, Jean-Francois; Fares, Rim; Hébrard,
Élodie M.; Jardine, Moira M.; Jeffers, Sandra V.; Marsden, Stephen C.;
Mengel, Matthew W.; Morin, Julien; Petit, Pascal; Vidotto, Aline A.;
Waite, Ian A.; BCool Collaboration
Bibcode: 2019ApJ...886..120S
Altcode: 2019arXiv191002129S
Main-sequence low-mass stars are known to spin down as a consequence
of their magnetized stellar winds. However, estimating the precise
rate of this spin-down is an open problem. The mass-loss rate, angular
momentum loss rate, and magnetic field properties of low-mass stars are
fundamentally linked, making this a challenging task. Of particular
interest is the stellar magnetic field geometry. In this work, we
consider whether non-dipolar field modes contribute significantly
to the spin-down of low-mass stars. We do this using a sample of
stars that have all been previously mapped with Zeeman-Doppler
imaging. For a given star, as long as its mass-loss rate is below
some critical mass-loss rate, only the dipolar fields contribute to
its spin-down torque. However, if it has a larger mass-loss rate,
higher-order modes need to be considered. For each star, we calculate
this critical mass-loss rate, which is a simple function of the field
geometry. Additionally, we use two methods of estimating mass-loss rates
for our sample of stars. In the majority of cases, we find that the
estimated mass-loss rates do not exceed the critical mass-loss rate;
hence, the dipolar magnetic field alone is sufficient to determine
the spin-down torque. However, we find some evidence that, at large
Rossby numbers, non-dipolar modes may start to contribute.
Title: The CARMENES search for exoplanets around M dwarfs. The He
I triplet at 10830 Å across the M dwarf sequence
Authors: Fuhrmeister, B.; Czesla, S.; Hildebrandt, L.; Nagel, E.;
Schmitt, J. H. M. M.; Hintz, D.; Johnson, E. N.; Sanz-Forcada, J.;
Schöfer, P.; Jeffers, S. V.; Caballero, J. A.; Zechmeister, M.;
Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Bauer, F. F.;
Béjar, V. J. S.; Cortés-Contreras, M.; Díez-Alonso, E.; Dreizler,
S.; Galadí-Enríquez, D.; Guenther, E. W.; Kaminski, A.; Kürster,
M.; Lafarga, M.; Montes, D.
Bibcode: 2019A&A...632A..24F
Altcode: 2019arXiv191100246F
The He I infrared (IR) triplet at 10 830 Å is an important activity
indicator for the Sun and in solar-type stars, however, it has rarely
been studied in relation to M dwarfs to date. In this study, we use the
time-averaged spectra of 319 single stars with spectral types ranging
from M0.0 V to M9.0 V obtained with the CARMENES high resolution
optical and near-infrared spectrograph at Calar Alto to study the
properties of the He I IR triplet lines. In quiescence, we find the
triplet in absorption with a decrease of the measured pseudo equivalent
width (pEW) towards later sub-types. For stars later than M5.0 V,
the He I triplet becomes undetectable in our study. This dependence
on effective temperature may be related to a change in chromospheric
conditions along the M dwarf sequence. When an emission in the triplet
is observed, we attribute it to flaring. The absence of emission during
quiescence is consistent with line formation by photo-ionisation
and recombination, while flare emission may be caused by collisions
within dense material. The He I triplet tends to increase in depth
according to increasing activity levels, ultimately becoming filled in;
however, we do not find a correlation between the pEW(He IR) and X-ray
properties. This behaviour may be attributed to the absence of very
inactive stars (LX/Lbol < -5.5) in our sample
or to the complex behaviour with regard to increasing depth and filling
in. Full Table 2 is 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/cat/J/A+A/632/A24
Title: Stellar activity analysis of Barnard's Star: very slow rotation
and evidence for long-term activity cycle
Authors: Toledo-Padrón, B.; González Hernández, J. I.;
Rodríguez-López, C.; Suárez Mascareño, A.; Rebolo, R.; Butler,
R. P.; Ribas, I.; Anglada-Escudé, G.; Johnson, E. N.; Reiners, A.;
Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Béjar, V. J. S.;
Morales, J. C.; Perger, M.; Jeffers, S. V.; Vogt, S.; Teske, J.;
Shectman, S.; Crane, J.; Díaz, M.; Arriagada, P.; Holden, B.; Burt,
J.; Rodríguez, E.; Herrero, E.; Murgas, F.; Pallé, E.; Morales,
N.; López-González, M. J.; Díez Alonso, E.; Tuomi, M.; Kiraga,
M.; Engle, S. G.; Guinan, E. F.; Strachan, J. B. P.; Aceituno, F. J.;
Aceituno, J.; Casanova, V. M.; Martín-Ruiz, S.; Montes, D.; Ortiz,
J. L.; Sota, A.; Briol, J.; Barbieri, L.; Cervini, I.; Deldem, M.;
Dubois, F.; Hambsch, F. -J.; Harris, B.; Kotnik, C.; Logie, L.;
Lopez, J.; McNeely, M.; Ogmen, Y.; Pérez, L.; Rau, S.; Rodríguez,
D.; Urquijo, F. S.; Vanaverbeke, S.
Bibcode: 2019MNRAS.488.5145T
Altcode: 2018arXiv181206712T; 2019MNRAS.tmp.1981T
The search for Earth-like planets around late-type stars using
ultrastable spectrographs requires a very precise characterization of
the stellar activity and the magnetic cycle of the star, since these
phenomena induce radial velocity (RV) signals that can be misinterpreted
as planetary signals. Among the nearby stars, we have selected Barnard's
Star (Gl 699) to carry out a characterization of these phenomena using
a set of spectroscopic data that covers about 14.5 yr and comes from
seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES,
APF, and PFS; and a set of photometric data that covers about 15.1 yr
and comes from four different photometric sources: ASAS, FCAPT-RCT,
AAVSO, and SNO. We have measured different chromospheric activity
indicators (H α, Ca II HK, and Na I D), as well as the full width
at half-maximum (FWHM), of the cross-correlation function computed
for a sub-set of the spectroscopic data. The analysis of generalized
Lomb-Scargle periodograms of the time series of different activity
indicators reveals that the rotation period of the star is 145 ±
15 d, consistent with the expected rotation period according to the
low activity level of the star and previous claims. The upper limit
of the predicted activity-induced RV signal corresponding to this
rotation period is about 1 m s-1. We also find evidence
of a long-term cycle of 10 ± 2 yr that is consistent with previous
estimates of magnetic cycles from photometric time series in other
M stars of similar activity levels. The available photometric data
of the star also support the detection of both the long-term and the
rotation signals.
Title: VizieR Online Data Catalog: HeI IR triplet measurements for
M dwarfs (Fuhrmeister+, 2019)
Authors: Fuhrmeister, B.; Czesla, S.; Hildebrandt, L.; Nagel, E.;
Schmitt, J. H. M. M.; Hintz, D.; Johnson, E. N.; Sanz-Forcada, J.;
Schoefer, P.; Jeffers, S. V.; Caballero, J. A.; Zechmeister, M.;
Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Bauer, F. F.;
Bejar, V. J. S.; Cortes-Contreras, M.; Diez-Alonso, E.; Dreizler,
S.; Galadi-Enriquez, D.; Guenther, E. W.; Kaminski, A.; Kuerster,
M.; Lafarga, M.; Montes, D.
Bibcode: 2019yCat..36320024F
Altcode:
We measure the pseudo-equivalent width (pEW) in the averaged stellar
spectra using a Voigt fit with four Voigt components to account for
neighbouring lines. The fit does not account for the bluest HeI triplet
component and treats the two redder components as one component as they
are totally blended for the used resolution of 80400. For comparison
purposes we give also pEW values of Hα, the bluest CaII IR triplet
line, and the HeI D3 line which were obtained by integration
over the line from the same spectra. As a further comparison for the
activity level of the star we give LX/Lbol values mostly taken from
the ROSAT all-sky survey. (1 data file).
Title: A giant exoplanet orbiting a very-low-mass star challenges
planet formation models
Authors: Morales, J. C.; Mustill, A. J.; Ribas, I.; Davies, M. B.;
Reiners, A.; Bauer, F. F.; Kossakowski, D.; Herrero, E.; Rodríguez,
E.; López-González, M. J.; Rodríguez-López, C.; Béjar, V. J. S.;
González-Cuesta, L.; Luque, R.; Pallé, E.; Perger, M.; Baroch,
D.; Johansen, A.; Klahr, H.; Mordasini, C.; Anglada-Escudé, G.;
Caballero, J. A.; Cortés-Contreras, M.; Dreizler, S.; Lafarga, M.;
Nagel, E.; Passegger, V. M.; Reffert, S.; Rosich, A.; Schweitzer,
A.; Tal-Or, L.; Trifonov, T.; Zechmeister, M.; Quirrenbach, A.;
Amado, P. J.; Guenther, E. W.; Hagen, H. -J.; Henning, T.; Jeffers,
S. V.; Kaminski, A.; Kürster, M.; Montes, D.; Seifert, W.; Abellán,
F. J.; Abril, M.; Aceituno, J.; Aceituno, F. J.; Alonso-Floriano,
F. J.; Ammler-von Eiff, M.; Antona, R.; Arroyo-Torres, B.; Azzaro,
M.; Barrado, D.; Becerril-Jarque, S.; Benítez, D.; Berdiñas, Z. M.;
Bergond, G.; Brinkmöller, M.; del Burgo, C.; Burn, R.; Calvo-Ortega,
R.; Cano, J.; Cárdenas, M. C.; Cardona Guillén, C.; Carro, J.; Casal,
E.; Casanova, V.; Casasayas-Barris, N.; Chaturvedi, P.; Cifuentes,
C.; Claret, A.; Colomé, J.; Czesla, S.; Díez-Alonso, E.; Dorda, R.;
Emsenhuber, A.; Fernández, M.; Fernández-Martín, A.; Ferro, I. M.;
Fuhrmeister, B.; Galadí-Enríquez, D.; Gallardo Cava, I.; García
Vargas, M. L.; Garcia-Piquer, A.; Gesa, L.; González-Álvarez,
E.; González Hernández, J. I.; González-Peinado, R.; Guàrdia,
J.; Guijarro, A.; de Guindos, E.; Hatzes, A. P.; Hauschildt, P. H.;
Hedrosa, R. P.; Hermelo, I.; Hernández Arabi, R.; Hernández Otero,
F.; Hintz, D.; Holgado, G.; Huber, A.; Huke, P.; Johnson, E. N.;
de Juan, E.; Kehr, M.; Kemmer, J.; Kim, M.; Klüter, J.; Klutsch,
A.; Labarga, F.; Labiche, N.; Lalitha, S.; Lampón, M.; Lara, L. M.;
Launhardt, R.; Lázaro, F. J.; Lizon, J. -L.; Llamas, M.; Lodieu,
N.; López del Fresno, M.; López Salas, J. F.; López-Santiago, J.;
Magán Madinabeitia, H.; Mall, U.; Mancini, L.; Mandel, H.; Marfil,
E.; Marín Molina, J. A.; Martín, E. L.; Martín-Fernández, P.;
Martín-Ruiz, S.; Martínez-Rodríguez, H.; Marvin, C. J.; Mirabet,
E.; Moya, A.; Naranjo, V.; Nelson, R. P.; Nortmann, L.; Nowak, G.;
Ofir, A.; Pascual, J.; Pavlov, A.; Pedraz, S.; Pérez Medialdea, D.;
Pérez-Calpena, A.; Perryman, M. A. C.; Rabaza, O.; Ramón Ballesta,
A.; Rebolo, R.; Redondo, P.; Rix, H. -W.; Rodler, F.; Rodríguez
Trinidad, A.; Sabotta, S.; Sadegi, S.; Salz, M.; Sánchez-Blanco,
E.; Sánchez Carrasco, M. A.; Sánchez-López, A.; Sanz-Forcada, J.;
Sarkis, P.; Sarmiento, L. F.; Schäfer, S.; Schlecker, M.; Schmitt,
J. H. M. M.; Schöfer, P.; Solano, E.; Sota, A.; Stahl, O.; Stock, S.;
Stuber, T.; Stürmer, J.; Suárez, J. C.; Tabernero, H. M.; Tulloch,
S. M.; Veredas, G.; Vico-Linares, J. I.; Vilardell, F.; Wagner, K.;
Winkler, J.; Wolthoff, V.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2019Sci...365.1441M
Altcode: 2019arXiv190912174M
Surveys have shown that super-Earth and Neptune-mass exoplanets are more
frequent than gas giants around low-mass stars, as predicted by the core
accretion theory of planet formation. We report the discovery of a giant
planet around the very-low-mass star GJ 3512, as determined by optical
and near-infrared radial-velocity observations. The planet has a minimum
mass of 0.46 Jupiter masses, very high for such a small host star,
and an eccentric 204-day orbit. Dynamical models show that the high
eccentricity is most likely due to planet-planet interactions. We use
simulations to demonstrate that the GJ 3512 planetary system challenges
generally accepted formation theories, and that it puts constraints
on the planet accretion and migration rates. Disk instabilities may
be more efficient in forming planets than previously thought.
Title: Erratum: The solar wind in time II: 3D stellar wind structure
and radio emission
Authors: Ó Fionnagáin, D.; Vidotto, A. A.; Petit, P.; Folsom,
C. P.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; do Nascimento,
J. -D.; BCool Collaboration
Bibcode: 2019MNRAS.487.3079O
Altcode: 2019MNRAS.tmp.1254O; 2019MNRAS.487.3079F
No abstract at ADS
Title: Planetary system around the nearby M dwarf GJ 357 including
a transiting, hot, Earth-sized planet optimal for atmospheric
characterization
Authors: Luque, R.; Pallé, E.; Kossakowski, D.; Dreizler, S.; Kemmer,
J.; Espinoza, N.; Burt, J.; Anglada-Escudé, G.; Béjar, V. J. S.;
Caballero, J. A.; Collins, K. A.; Collins, K. I.; Cortés-Contreras,
M.; Díez-Alonso, E.; Feng, F.; Hatzes, A.; Hellier, C.; Henning,
T.; Jeffers, S. V.; Kaltenegger, L.; Kürster, M.; Madden, J.;
Molaverdikhani, K.; Montes, D.; Narita, N.; Nowak, G.; Ofir, A.;
Oshagh, M.; Parviainen, H.; Quirrenbach, A.; Reffert, S.; Reiners,
A.; Rodríguez-López, C.; Schlecker, M.; Stock, S.; Trifonov, T.;
Winn, J. N.; Zapatero Osorio, M. R.; Zechmeister, M.; Amado, P. J.;
Anderson, D. R.; Batalha, N. E.; Bauer, F. F.; Bluhm, P.; Burke, C. J.;
Butler, R. P.; Caldwell, D. A.; Chen, G.; Crane, J. D.; Dragomir,
D.; Dressing, C. D.; Dynes, S.; Jenkins, J. M.; Kaminski, A.; Klahr,
H.; Kotani, T.; Lafarga, M.; Latham, D. W.; Lewin, P.; McDermott,
S.; Montañés-Rodríguez, P.; Morales, J. C.; Murgas, F.; Nagel,
E.; Pedraz, S.; Ribas, I.; Ricker, G. R.; Rowden, P.; Seager, S.;
Shectman, S. A.; Tamura, M.; Teske, J.; Twicken, J. D.; Vanderspeck,
R.; Wang, S. X.; Wohler, B.
Bibcode: 2019A&A...628A..39L
Altcode: 2019arXiv190412818L
We report the detection of a transiting Earth-size planet around GJ
357, a nearby M2.5 V star, using data from the Transiting Exoplanet
Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot,
Earth-sized planet (Teq = 525 ± 11 K) with a radius of
Rb = 1.217 ± 0.084 R⊕ and an orbital period
of Pb = 3.93 d. Precise stellar radial velocities from
CARMENES and PFS, as well as archival data from HIRES, UVES, and
HARPS also display a 3.93-day periodicity, confirming the planetary
nature and leading to a planetary mass of Mb = 1.84 ± 0.31
M⊕. In addition to the radial velocity signal for GJ 357
b, more periodicities are present in the data indicating the presence
of two further planets in the system: GJ 357 c, with a minimum mass
of Mc = 3.40 ± 0.46 M⊕ in a 9.12 d orbit,
and GJ 357 d, with a minimum mass of Md = 6.1 ± 1.0
M⊕ in a 55.7 d orbit inside the habitable zone. The host
is relatively inactive and exhibits a photometric rotation period of
Prot = 78 ± 2 d. GJ 357 b isto date the second closest
transiting planet to the Sun, making it a prime target for further
investigations such as transmission spectroscopy. Therefore, GJ 357 b
represents one of the best terrestrial planets suitable for atmospheric
characterization with the upcoming JWST and ground-based ELTs. RV 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/628/A39
Title: The CARMENES search for exoplanets around M
dwarfs. Photospheric parameters of target stars from high-resolution
spectroscopy. II. Simultaneous multiwavelength range modeling of
activity insensitive lines
Authors: Passegger, V. M.; Schweitzer, A.; Shulyak, D.; Nagel, E.;
Hauschildt, P. H.; Reiners, A.; Amado, P. J.; Caballero, J. A.;
Cortés-Contreras, M.; Domínguez-Fernández, A. J.; Quirrenbach,
A.; Ribas, I.; Azzaro, M.; Anglada-Escudé, G.; Bauer, F. F.; Béjar,
V. J. S.; Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers, S. V.;
Kaminski, A.; Kürster, M.; Lafarga, M.; Martín, E. L.; Montes, D.;
Morales, J. C.; Schmitt, J. H. M. M.; Zechmeister, M.
Bibcode: 2019A&A...627A.161P
Altcode: 2019arXiv190700807P
We present precise photospheric parameters of 282 M dwarfs
determined from fitting the most recent version of PHOENIX models to
high-resolution CARMENES spectra in the visible (0.52-0.96 μm) and NIR
wavelength range (0.96-1.71 μm). With its aim to search for habitable
planets around M dwarfs, several planets of different masses have
been detected. The characterization of the target sample is important
for the ability to derive and constrain the physical properties of any
planetary systems that are detected. As a continuation of previous work
in this context, we derived the fundamental stellar parameters effective
temperature, surface gravity, and metallicity of the CARMENES M-dwarf
targets from PHOENIX model fits using a χ2 method. We
calculated updated PHOENIX stellar atmosphere models that include a
new equation of state to especially account for spectral features
of low-temperature stellar atmospheres as well as new atomic and
molecular line lists. We show the importance of selecting magnetically
insensitive lines for fitting to avoid effects of stellar activity
in the line profiles. For the first time, we directly compare stellar
parameters derived from multiwavelength range spectra, simultaneously
observed for the same star. In comparison with literature values we
show that fundamental parameters derived from visible spectra and
visible and NIR spectra combined are in better agreement than those
derived from the same spectra in the NIR alone. Full Tables
B.1 and B.2 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/627/A161
Title: VizieR Online Data Catalog: Radial velocities of GJ 357
(Luque+, 2019)
Authors: Luque, R.; Palle, E.; Kossakowski, D.; Dreizler, S.; Kemmer,
J.; Espinoza, N.; Burt, J.; Anglada-Escude, G.; Bejar, V. J. S.;
Caballero, J. A.; Collins, K. A.; Collins, K. I.; Cortes-Contreras,
M.; Diez-Alonso, E.; Feng, F.; Hatzes, A.; Hellier, C.; Henning,
T.; Jeffers, S. V.; Kaltenegger, L.; Kuerster, M.; Madden, J.;
Molaverdikhani, K.; Montes, D.; Narita, N.; Nowak, G.; Ofir, A.;
Oshagh, M.; Parviainen, H.; Quirrenbach, A.; Reffert, S.; Reiners,
A.; Rodriguez-Lopez, C.; Schlecker, M.; Stock, S.; Trifonov, T.;
Winn, J. N.; Zapatero Osorio, M. R.; Zechmeister, M.; Amado, P. J.;
Anderson, D. R.; Batalha, N. E.; Bauer, F. F.; Bluhm, P.; Burke, C. J.;
Butler, R. P.; Caldwell, D. A.; Chen, G.; Crane, J. D.; Dragomir,
D.; Dressing, C. D.; Dynes, S.; Jenkins, J. M.; Kaminski, A.; Klahr,
H.; Kotani, T.; Lafarga, M.; Latham, D. W.; Lewin, P.; McDermott, S.;
Montanes-Rodriguez, P.; Morales, J. C.; Murgas, F.; Nagel, E.; Pedraz,
S.; Ribas, I.; Ricker, G. R.; Rowden, P.; Seager, S.; Shectman, S. A.;
Tamura, M.; Teske, J.; Twicken, J. D.; Vanderspeck, R.; Wang, S. X.;
Wohler, B.
Bibcode: 2019yCat..36280039L
Altcode:
Radial velocities of GJ 357 from HIRES (Vogt et al., 1994, in
Proc. SPIE, Vol. 2198, 362), UVES (programs 072.C-0495, 078.C-0829,
and 173.C-0606), HARPS (Mayor et al., 2003Msngr.114...20M; programs
072.C-0488, 183.C-0437), CARMENES (Quirrenbach et al., 2016, in
Proc. SPIE, Vol. 9147,91471F; 2018, in Society of Photo-Optical
Instrumentation Engineers (SPIE) Conference Series, Vol. 10702,
107020W), and PFS (Crane et al., 2010aepr.confE..19C). (1 data
file).
Title: The CARMENES search for exoplanets around M dwarfs. Detection
of a mini-Neptune around LSPM J2116+0234 and refinement of orbital
parameters of a super-Earth around GJ 686 (BD+18 3421)
Authors: Lalitha, S.; Baroch, D.; Morales, J. C.; Passegger, V. M.;
Bauer, F. F.; Cardona Guillén, C.; Dreizler, S.; Oshagh, M.; Reiners,
A.; Ribas, I.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Béjar,
V. J. S.; Colomé, J.; Cortés-Contreras, M.; Galadí-Enríquez, D.;
González-Cuesta, L.; Guenther, E. W.; Hagen, H. -J.; Henning, T.;
Herrero, E.; Husser, T. -O.; Jeffers, S. V.; Kaminski, A.; Kürster,
M.; Lafarga, M.; Lodieu, N.; López-González, M. J.; Montes, D.;
Perger, M.; Rosich, A.; Rodríguez, E.; Rodríguez-López, C.; Schmitt,
J. H. M. M.; Tal-Or, L.; Zechmeister, M.
Bibcode: 2019A&A...627A.116L
Altcode: 2019arXiv190509075L
Although M dwarfs are known for high levels of stellar activity,
they are ideal targets for the search of low-mass exoplanets
with the radial velocity (RV) method. We report the discovery of a
planetary-mass companion around LSPM J2116+0234 (M3.0 V) and confirm
the existence of a planet orbiting GJ 686 (BD+18 3421; M1.0 V). The
discovery of the planet around LSPM J2116+0234 is based on CARMENES
RV observations in the visual and near-infrared channels. We confirm
the planet orbiting around GJ 686 by analyzing the RV data spanning
over two decades of observationsfrom CARMENES VIS, HARPS-N, HARPS,
and HIRES. We find planetary signals at 14.44 and 15.53 d in the
RV data for LSPM J2116+0234 and GJ 686, respectively. Additionally,
the RV, photometric time series, and various spectroscopic indicators
show hints of variations of 42 d for LSPM J2116+0234 and 37 d for GJ
686, which we attribute to the stellar rotation periods. The orbital
parameters of the planets are modeled with Keplerian fits together
with correlated noise from the stellar activity. A mini-Neptune with a
minimum mass of 11.8 M⊕ orbits LSPM J2116+0234 producing a
RV semi-amplitude of 6.19 m s-1, while a super-Earth of mass
6.6 M⊕ orbits GJ 686 and produces a RV semi-amplitude of
3.0 m s-1. Both LSPM J2116+0234 and GJ 686 have planetary
companions populating the regime of exoplanets with masses lower
than 15 M⊕ and orbital periods <20 d. Table
A.1 and A.2 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/627/A116
Title: The CARMENES search for exoplanets around M dwarfs. Two
temperate Earth-mass planet candidates around Teegarden's Star
Authors: Zechmeister, M.; Dreizler, S.; Ribas, I.; Reiners, A.;
Caballero, J. A.; Bauer, F. F.; Béjar, V. J. S.; González-Cuesta,
L.; Herrero, E.; Lalitha, S.; López-González, M. J.; Luque, R.;
Morales, J. C.; Pallé, E.; Rodríguez, E.; Rodríguez López, C.;
Tal-Or, L.; Anglada-Escudé, G.; Quirrenbach, A.; Amado, P. J.; Abril,
M.; Aceituno, F. J.; Aceituno, J.; Alonso-Floriano, F. J.; Ammler-von
Eiff, M.; Antona Jiménez, R.; Anwand-Heerwart, H.; Arroyo-Torres,
B.; Azzaro, M.; Baroch, D.; Barrado, D.; Becerril, S.; Benítez,
D.; Berdiñas, Z. M.; Bergond, G.; Bluhm, P.; Brinkmöller, M.;
del Burgo, C.; Calvo Ortega, R.; Cano, J.; Cardona Guillén, C.;
Carro, J.; Cárdenas Vázquez, M. C.; Casal, E.; Casasayas-Barris,
N.; Casanova, V.; Chaturvedi, P.; Cifuentes, C.; Claret, A.; Colomé,
J.; Cortés-Contreras, M.; Czesla, S.; Díez-Alonso, E.; Dorda, R.;
Fernández, M.; Fernández-Martín, A.; Fuhrmeister, B.; Fukui, A.;
Galadí-Enríquez, D.; Gallardo Cava, I.; Garcia de la Fuente, J.;
Garcia-Piquer, A.; García Vargas, M. L.; Gesa, L.; Góngora Rueda, J.;
González-Álvarez, E.; González Hernández, J. I.; González-Peinado,
R.; Grözinger, U.; Guàrdia, J.; Guijarro, A.; de Guindos, E.;
Hatzes, A. P.; Hauschildt, P. H.; Hedrosa, R. P.; Helmling, J.;
Henning, T.; Hermelo, I.; Hernández Arabi, R.; Hernández Castaño,
L.; Hernández Otero, F.; Hintz, D.; Huke, P.; Huber, A.; Jeffers,
S. V.; Johnson, E. N.; de Juan, E.; Kaminski, A.; Kemmer, J.; Kim,
M.; Klahr, H.; Klein, R.; Klüter, J.; Klutsch, A.; Kossakowski, D.;
Kürster, M.; Labarga, F.; Lafarga, M.; Llamas, M.; Lampón, M.; Lara,
L. M.; Launhardt, R.; Lázaro, F. J.; Lodieu, N.; López del Fresno,
M.; López-Puertas, M.; López Salas, J. F.; López-Santiago, J.;
Magán Madinabeitia, H.; Mall, U.; Mancini, L.; Mandel, H.; Marfil,
E.; Marín Molina, J. A.; Maroto Fernández, D.; Martín, E. L.;
Martín-Fernández, P.; Martín-Ruiz, S.; Marvin, C. J.; Mirabet,
E.; Montañés-Rodríguez, P.; Montes, D.; Moreno-Raya, M. E.;
Nagel, E.; Naranjo, V.; Narita, N.; Nortmann, L.; Nowak, G.; Ofir,
A.; Oshagh, M.; Panduro, J.; Parviainen, H.; Pascual, J.; Passegger,
V. M.; Pavlov, A.; Pedraz, S.; Pérez-Calpena, A.; Pérez Medialdea,
D.; Perger, M.; Perryman, M. A. C.; Rabaza, O.; Ramón Ballesta, A.;
Rebolo, R.; Redondo, P.; Reffert, S.; Reinhardt, S.; Rhode, P.; Rix,
H. -W.; Rodler, F.; Rodríguez Trinidad, A.; Rosich, A.; Sadegi, S.;
Sánchez-Blanco, E.; Sánchez Carrasco, M. A.; Sánchez-López, A.;
Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer, S.; Schmitt,
J. H. M. M.; Schöfer, P.; Schweitzer, A.; Seifert, W.; Shulyak, D.;
Solano, E.; Sota, A.; Stahl, O.; Stock, S.; Strachan, J. B. P.; Stuber,
T.; Stürmer, J.; Suárez, J. C.; Tabernero, H. M.; Tala Pinto, M.;
Trifonov, T.; Veredas, G.; Vico Linares, J. I.; Vilardell, F.; Wagner,
K.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2019A&A...627A..49Z
Altcode: 2019arXiv190607196Z
Context. Teegarden's Star is the brightest and one of the nearest
ultra-cool dwarfs in the solar neighbourhood. For its late spectral
type (M7.0 V), the star shows relatively little activity and is
a prime target for near-infrared radial velocity surveys such as
CARMENES.
Aims: As part of the CARMENES search for exoplanets
around M dwarfs, we obtained more than 200 radial-velocity measurements
of Teegarden's Star and analysed them for planetary signals.
Methods: We find periodic variability in the radial velocities of
Teegarden's Star. We also studied photometric measurements to rule
out stellar brightness variations mimicking planetary signals.
Results: We find evidence for two planet candidates, each with 1.1
M⊕ minimum mass, orbiting at periods of 4.91 and 11.4 d,
respectively. No evidence for planetary transits could be found in
archival and follow-up photometry. Small photometric variability is
suggestive of slow rotation and old age.
Conclusions: The two
planets are among the lowest-mass planets discovered so far, and they
are the first Earth-mass planets around an ultra-cool dwarf for which
the masses have been determined using radial velocities. Tables
D.1 and D.2 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/627/A49
Title: Magnetic fields in M dwarfs from the CARMENES survey
Authors: Shulyak, D.; Reiners, A.; Nagel, E.; Tal-Or, L.; Caballero,
J. A.; Zechmeister, M.; Béjar, V. J. S.; Cortés-Contreras, M.;
Martin, E. L.; Kaminski, A.; Ribas, I.; Quirrenbach, A.; Amado, P. J.;
Anglada-Escudé, G.; Bauer, F. F.; Dreizler, S.; Guenther, E. W.;
Henning, T.; Jeffers, S. V.; Kürster, M.; Lafarga, M.; Montes, D.;
Morales, J. C.; Pedraz, S.
Bibcode: 2019A&A...626A..86S
Altcode: 2019arXiv190412762S
Context. M dwarfs are known to generate the strongest magnetic fields
among main-sequence stars with convective envelopes, but we are still
lacking a consistent picture of the link between the magnetic fields
and underlying dynamo mechanisms, rotation, and activity.
Aims:
In this work we aim to measure magnetic fields from the high-resolution
near-infrared spectra taken with the CARMENES radial-velocity planet
survey in a sample of 29 active M dwarfs and compare our results
against stellar parameters.
Methods: We used the state-of-the-art
radiative transfer code to measure total magnetic flux densities from
the Zeeman broadening of spectral lines and filling factors.
Results: We detect strong kG magnetic fields in all our targets. In
16 stars the magnetic fields were measured for the first time. Our
measurements are consistent with the magnetic field saturation in stars
with rotation periods P < 4 d. The analysis of the magnetic filling
factors reveal two different patterns of either very smooth distribution
or a more patchy one, which can be connected to the dynamo state of
the stars and/or stellar mass.
Conclusions: Our measurements
extend the list of M dwarfs with strong surface magnetic fields. They
also allow us to better constrain the interplay between the magnetic
energy, stellar rotation, and underlying dynamo action. The high
spectral resolution and observations at near-infrared wavelengths are
the beneficial capabilities of the CARMENES instrument that allow us
to address important questions about the stellar magnetism.
Title: VizieR Online Data Catalog: CARMENES stars multi wavelength
measurements (Passegger+, 2019)
Authors: Passegger, V. M.; Schweitzer, A.; Shulyak, D.; Nagel, E.;
Hauschildt, P. H.; Reiners, A.; Amado, P. J.; Caballero, J. A.;
Cortes-Contreras, M.; Dominguez-Fernandez, A. J.; Quirrenbach,
A.; Ribas, I.; Azarro, M.; Anglada-Escude, G.; Bauer, F. F.; Bejar,
V. J. S.; Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers, S. V.;
Kaminski, A.; Kuerster, M.; Lafarga, M.; Martin, E. L.; Montes, D.;
Morales, J. C.; Schmidt, J. H. M. M.; Zechmeister, M.
Bibcode: 2019yCat..36270161P
Altcode:
We present basic photospheric parameters of 282 M dwarfs within
the CARMENES survey in the visible and near-infrared wavelength
ranges. In table_b1 we provide Carmencita identifier (Karmn), Simbad
name, equatorial coordinates, spectral type, rotational velocity,
assumed age, and an activity flag for each star in our sample. In
table_b2 we give effective temperature, surface gravity and [Fe/H]
for each star in different wavelength ranges (VIS+NIR, NIR, and VIS),
together with their errors. (2 data files).
Title: VizieR Online Data Catalog: LSPM J2116+0234 and GJ 686 radial
velocities (Lalitha+, 2019)
Authors: Lalitha, S.; Baroch, D.; Morales, J. C.; Passegger, V. M.;
Bauer, F. F.; Cardona Guillen, C.; Dreizler, S.; Oshagh, M.; Reiners,
A.; Ribas, I.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.;
Bejar, V. J. S.; Colome, J.; Cortes-Contreras, M.; Galadi-Enriquez,
D.; Gonzalez-Cuesta, L.; Guenther, E. W.; Hagen, H. -J.; Henning, T.;
Herrero, E.; Husser, T. -O.; Jeffers, S. V.; Kaminski, A.; Kuerster,
M.; Lafarga, M.; Lodieu, N.; Lopez-Gonzalez, M. J.; Montes, D.;
Perger, M.; Rosich, A.; Rodriguez, E.; Rodriguez-Lopez, C.; Schmitt,
J. H. M. M.; Tal-Or, L.; Zechmeister, M.
Bibcode: 2019yCat..36270116L
Altcode:
We analysed radial velocity data from the CARMENES NIR and VIS channels
for LSPM J2116+0234, and from CARMENES VIS channel, HARPS and HIRES for
GJ 686. All the RVs are corrected for barycentric motion and secular
acceleration. The CARMENES measurements were taken in the context
of the CARMENES search for exoplanets around M dwarfs. The CARMENES
instrument consists of two channels: the VIS channel obtains spectra
at a resolution of R=94600 in the wavelength range 520-960nm, while
the NIR channel yields spectra of R=80400 covering 960-1710nm. Both
channels are calibrated in wavelength with hollow-cathode lamps
and use temperature- and pressure-stabilized Fabry-Perot etalons
to interpolate the wavelength solution and simultaneously monitor
the spectrograph drift during nightly operations (Bauer et al.,
2015A&A...581A.117B). (2 data files).
Title: The CARMENES search for exoplanets around M dwarfs. Different
roads to radii and masses of the target stars
Authors: Schweitzer, A.; Passegger, V. M.; Cifuentes, C.; Béjar,
V. J. S.; Cortés-Contreras, M.; Caballero, J. A.; del Burgo,
C.; Czesla, S.; Kürster, M.; Montes, D.; Zapatero Osorio, M. R.;
Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; Aceituno, J.;
Anglada-Escudé, G.; Bauer, F. F.; Dreizler, S.; Jeffers, S. V.;
Guenther, E. W.; Henning, T.; Kaminski, A.; Lafarga, M.; Marfil,
E.; Morales, J. C.; Schmitt, J. H. M. M.; Seifert, W.; Solano, E.;
Tabernero, H. M.; Zechmeister, M.
Bibcode: 2019A&A...625A..68S
Altcode: 2019arXiv190403231S
Aims: We determine the radii and masses of 293 nearby, bright M
dwarfs of the CARMENES survey. This is the first time that such a large
and homogeneous high-resolution (R > 80 000) spectroscopic survey
has been used to derive these fundamental stellar parameters.
Methods: We derived the radii using Stefan-Boltzmann's law. We
obtained the required effective temperatures Teff from
a spectral analysis and we obtained the required luminosities L
from integrated broadband photometry together with the Gaia DR2
parallaxes. The mass was then determined using a mass-radius relation
that we derived from eclipsing binaries known in the literature. We
compared this method with three other methods: (1) We calculated
the mass from the radius and the surface gravity log g, which was
obtained from the same spectral analysis as Teff. (2) We
used a widely used infrared mass-magnitude relation. (3) We used a
Bayesian approach to infer stellar parameters from the comparison of
the absolute magnitudes and colors of our targets with evolutionary
models.
Results: Between spectral types M0 V and M7 V our radii
cover the range 0.1 R⊙ < R < 0.6 R⊙
with an error of 2-3% and our masses cover 0.09 ℳ⊙
< ℳ< 0.6ℳ⊙ with an error of 3-5%. We find
good agreement between the masses determined with these different
methods for most of our targets. Only the masses of very young
objects show discrepancies. This can be well explained with the
assumptions that we used for our methods. Table B.1 (stellar
parameters) is 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/625/A68
Title: VizieR Online Data Catalog: Teegarden's Star RV and Hα curves
(Zechmeister+, 2019)
Authors: Zechmeister, M.; Dreizler, M.; Ribas, I.; Reiners, A.;
Caballero, J. A.; Bauer, F. F.; Bejar, V. J. S.; Gonzalez-Cuesta, L.;
Herrero, E.; Lalitha, S.; Lopez-Gonzalez, M. J.; Luque, R.; Morales,
J. C.; Palle, E.; Rodriguez, E.; Rodriguez Lopez, C.; Tal-Or, L.;
Anglada-Escude, G.; Quirrenbach, A.; Amado, P. J.; Abril, M.; Aceituno,
F. J.; Aceituno, J.; Alonso-Floriano, F. J.; Ammler-von Eiff, M.;
Antona Jimenez, R.; Anwand-Heerwart, H.; Arroyo-Torres, B.; Azzaro,
M.; Baroch, D.; Barrado, D.; Becerril, S.; Benitez, D.; Berdinas,
Z. M.; Bergond, G.; Bluhm, P.; Brinkmoeller, M.; Del Burgo, C.; Calvo
Ortega, R.; Cano, J.; Cardona Guillen, C.; Carro, J.; Cardenas Vazquez,
M. C.; Casal, E.; Casasayas-Barris, N.; Casanova, V.; Chaturvedi, P.;
Cifuentes, C.; Claret, A.; Colome, J.; Cortes-Contreras, M.; Czesla,
S.; Diez-Alonso, E.; Dorda, R.; Fernandez, M.; Fernandez-Martin,
A.; Fuhrmeister, B.; Fukui, A.; Galadi-Enriquez, D.; Gallardo Cava,
I.; Garcia de La Fuente, J.; Garcia-Piquer, A.; Garcia Vargas, M. L.;
Gesa, L.; Gongora Rueda, J.; Gonzalez-Alvarez, E.; Gonzalez Hernandez,
J. I.; Gonzalez-Peinado, R.; Groezinger, U.; Guardia, J.; Guijarro,
A.; de Guindos, E.; Hatzes, A. P.; Hauschildt, P. H.; Hedrosa,
R. P.; Helmling, J.; Henning, T.; Hermelo, I.; Hernandez Arabi, R.;
Hernandez Castano, L.; Hernandez, Otero F.; Hintz, D.; Huke, P.;
Huber, A.; Jeffers, S. V.; Johnson, E. N.; de Juan, E.; Kaminski,
A.; Kemmer, J.; Kim, M.; Klahr, H.; Klein, R.; Klueter, J.; Klutsch,
A.; Kossakowski, D.; Kuerster, M.; Labarga, F.; Lafarga, M.; Llamas,
M.; Lampon, M.; Lara, L. M.; Launhardt, R.; Lazaro, F. J.; Lodieu,
N.; Lopez Del Fresno, M.; Lopez-Puertas, M.; Lopez Salas, J. F.;
Lopez-Santiago, J.; Magan Madinabeitia, H.; Mall, U.; Mancini, L.;
Mandel, H.; Marfil, E.; Marin Molina, J. A.; Maroto Fernandez, D.;
Martin, E. L.; Martin-Fernandez, P.; Martin-Ruiz, S.; Marvin, C. J.;
Mirabet, E.; Montanes-Rodriguez, P.; Montes, D.; Moreno-Raya, M. E.;
Nagel, E.; Naranjo, V.; Narita, N.; Nortmann, L.; Nowak, G.; Ofir,
A.; Oshagh, M.; Panduro, J.; Parviainen, H.; Pascual, J.; Passegger,
V. M.; Pavlov, A.; Pedraz, S.; Perez-Calpena, A.; Perez Medialdea,
D.; Perger, M.; Perryman, M. A. C.; Rabaza, O.; Ramon Ballesta,
A.; Rebolo, R.; Redondo, P.; Reffert, S.; Reinhardt, S.; Rhode, P.;
Rix, H. -W.; Rodler, F.; Rodriguez Trinidad, A.; Rosich, A.; Sadegi,
S.; Sanchez-Blanco, E.; Sanchez Carrasco, M. A.; Sanchez-Lopez, A.;
Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schaefer, S.; Schmitt,
J. H. M. M.; Schoefer, P.; Schweitzer, A.; Seifert, W.; Shulyak,
D.; Solano, E.; Sota, A.; Stahl, O.; Stock, S.; Strachan, J. B. P.;
Stuber, T.; Stuermer, J.; Suarez, J. C.; Tabernero, H. M.; Tala Pinto,
M.; Trifonov, T.; Veredas, G.; Vico Linares, J. I.; Vilardell, F.;
Wagner, K.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2019yCat..36270049Z
Altcode:
Time series for radial velocities and activity indicators of Teegarden's
Star from CARMENES VIS and NIR spectrograph are presented. See
Zechmeister et al. (2017A&A...609A..12Z) for a detailed description
of the parameters. (2 data files).
Title: Estimating Magnetic Filling Factors from Zeeman-Doppler
Magnetograms
Authors: See, Victor; Matt, Sean P.; Folsom, Colin P.; Boro Saikia,
Sudeshna; Donati, Jean-Francois; Fares, Rim; Finley, Adam J.; Hébrard,
Élodie M.; Jardine, Moira M.; Jeffers, Sandra V.; Lehmann, Lisa T.;
Marsden, Stephen C.; Mengel, Matthew W.; Morin, Julien; Petit, Pascal;
Vidotto, Aline A.; Waite, Ian A.; BCool Collaboration
Bibcode: 2019ApJ...876..118S
Altcode: 2019arXiv190305595S
Low-mass stars are known to have magnetic fields that are believed to
be of dynamo origin. Two complementary techniques are principally used
to characterize them. Zeeman-Doppler imaging (ZDI) can determine the
geometry of the large-scale magnetic field while Zeeman broadening
can assess the total unsigned flux including that associated with
small-scale structures such as spots. In this work, we study a
sample of stars that have been previously mapped with ZDI. We show
that the average unsigned magnetic flux follows an activity-rotation
relation separating into saturated and unsaturated regimes. We also
compare the average photospheric magnetic flux recovered by ZDI,
< {B}V> , with that recovered by Zeeman broadening
studies, < {B}I> . In line with previous studies,
< {B}V> ranges from a few % to ∼20% of <
{B}I> . We show that a power-law relationship between
< {B}V> and < {B}I> exists and that
ZDI recovers a larger fraction of the magnetic flux in more active
stars. Using this relation, we improve on previous attempts to estimate
filling factors, i.e., the fraction of the stellar surface covered with
magnetic field, for stars mapped only with ZDI. Our estimated filling
factors follow the well-known activity-rotation relation, which is in
agreement with filling factors obtained directly from Zeeman broadening
studies. We discuss the possible implications of these results for
flux tube expansion above the stellar surface and stellar wind models.
Title: VizieR Online Data Catalog: Radii and masses of the CARMENES
targets (Schweitzer+, 2019)
Authors: Schweitzer, A.; Passegger, V. M.; Cifuentes, C.; Bejar,
V. J. S.; Cortes-Contreras, M.; Caballero, J. A.; Del Burgo, C.;
Czesla, S.; Kuerster, M.; Montes, D.; Zapatero Osorio, M. R.;
Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; Aceituno,
J.; Anglada-Escude, G.; Bauer, F. F.; Dreizler, S.; Jeffers, S. V.;
Guenther, E. W.; Henning, T.; Kaminski, A.; Lafarga, M.; Marfil,
E.; Morales, J. C.; Schmitt, J. H. M. M.; Seifert, W.; Solano, E.;
Tabernero, H. M.; Zechmeister, M.
Bibcode: 2019yCat..36250068S
Altcode:
Table B1 contains the stellar parameters of our sample. The
sample consists of 293 nearby, bright M dwarfs with no known close
companions. Their metallicities spread around solar metallicity. Most
stars are inactive or mildly active and older than a few hundred million
years. However, known active or young stars are also included although
most of the analyses assume inactive main sequence stars. All parameters
are determined by us except where noted otherwise. (1 data file).
Title: Gliese 49: activity evolution and detection of a super-Earth. A
HADES and CARMENES collaboration
Authors: Perger, M.; Scandariato, G.; Ribas, I.; Morales, J. C.;
Affer, L.; Azzaro, M.; Amado, P. J.; Anglada-Escudé, G.; Baroch,
D.; Barrado, D.; Bauer, F. F.; Béjar, V. J. S.; Caballero, J. A.;
Cortés-Contreras, M.; Damasso, M.; Dreizler, S.; González-Cuesta,
L.; González Hernández, J. I.; Guenther, E. W.; Henning, T.;
Herrero, E.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga,
M.; Leto, G.; López-González, M. J.; Maldonado, J.; Micela, G.;
Montes, D.; Pinamonti, M.; Quirrenbach, A.; Rebolo, R.; Reiners, A.;
Rodríguez, E.; Rodríguez-López, C.; Schmitt, J. H. M. M.; Sozzetti,
A.; Suárez Mascareño, A.; Toledo-Padrón, B.; Zanmar Sánchez, R.;
Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2019A&A...624A.123P
Altcode: 2019arXiv190304808P
Context. Small planets around low-mass stars often show orbital periods
in a range that corresponds to the temperate zones of their host stars
which are therefore of prime interest for planet searches. Surface
phenomena such as spots and faculae create periodic signals in radial
velocities and in observational activity tracers in the same range,
so they can mimic or hide true planetary signals.
Aims: We
aim to detect Doppler signals corresponding to planetary companions,
determine their most probable orbital configurations, and understand
the stellar activity and its impact on different datasets.
Methods: We analyzed 22 yr of data of the M1.5 V-type star Gl 49
(BD+61 195) including HARPS-N and CARMENES spectrographs, complemented
by APT2 and SNO photometry. Activity indices are calculated from the
observed spectra, and all datasets are analyzed with periodograms and
noise models. We investigated how the variation of stellar activity
imprints on our datasets. We further tested the origin of the signals
and investigate phase shifts between the different sets. To search
for the best-fit model we maximize the likelihood function in a Markov
chain Monte Carlo approach.
Results: As a result of this study,
we are able to detect the super-Earth Gl 49b with a minimum mass of 5.6
M⊕. It orbits its host star with a period of 13.85 d at a
semi-major axis of 0.090 au and we calculate an equilibrium temperature
of 350 K and a transit probability of 2.0%. The contribution from the
spot-dominated host star to the different datasets is complex, and
includes signals from the stellar rotation at 18.86 d, evolutionary
timescales of activity phenomena at 40-80 d, and a long-term variation
of at least four years. Based on observations made with the Italian
TNG, operated on the island of La Palma, Spain; the CARMENES instrument
installed at the 3.5 m telescope of the Calar Alto Observatory,
Spain; the robotic APT2 located at Serra La Nave on Mt. Etna, Italy;
and the T90 telescope at Sierra Nevada Observatory, Spain.Full
Table A.1 is 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/624/A123
Title: VizieR Online Data Catalog: Gl 49 radial velocities and
activity indicators (Perger+, 2019)
Authors: Perger, M.; Scandariato, G.; Ribas, I.; Morales, J. C.;
Affer, L.; Azzaro, M.; Amado, P. J.; Anglada-Escude, G.; Baroch,
D.; Barrado, D.; Bauer, F. F.; Bejar, V. J. S.; Caballero, J. A.;
Cortes-Contreras, M.; Damasso, M.; Dreizler, S.; Gonzalez-Cuesta,
L.; Gonzalez Hernandez, J. I.; Guenther, E. W.; Henning, T.;
Herrero, E.; Jeffers, S. V.; Kaminski, A.; Kuerster, M.; Lafarga,
M.; Leto, G.; Lopez-Gonzalez, M. J.; Maldonado, J.; Micela, G.;
Montes, D.; Pinamonti, M.; Quirrenbach, A.; Rebolo, R.; Reiners, A.;
Rodriguez, E.; Rodriguez-Lopez, C.; Schmitt, J. H. M. M.; Sozzetti,
A.; Suarezmascareno, A.; Toledo-Padron, B.; Zanmar Sanchez, R.;
Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2019yCat..36240123P
Altcode:
Radial velocity and activity indicator time-series data of Gl 49
from HIRES, HARPS-N, and CARMENES instruments. We obtained 137
RVs from optical spectra of the HADES program. They were observed
over six seasons (S1 to S6) between 3 Sep 2012 and 11 Oct 2017 with
HARPS-N. We obtained spectroscopic observations with the CARMENES
instrument, installed since 2015 at the 3.51m telescope of the Calar
Alto Observatory in Spain. Gl 49 was also observed with the HIRES
instrument, installed since the late 1990s at the Keck I telescope
located in Hawaii, USA. (1 data file).
Title: The CARMENES search for exoplanets around M dwarfs. Period
search in Hα, Na I D, and Ca II IRT lines
Authors: Fuhrmeister, B.; Czesla, S.; Schmitt, J. H. M. M.; Johnson,
E. N.; Schöfer, P.; Jeffers, S. V.; Caballero, J. A.; Zechmeister,
M.; Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Bauer, F.;
Béjar, V. J. S.; Cortés-Contreras, M.; Díez Alonso, E.; Dreizler,
S.; Galadí-Enríquez, D.; Guenther, E. W.; Kaminski, A.; Kürster,
M.; Lafarga, M.; Montes, D.
Bibcode: 2019A&A...623A..24F
Altcode: 2019arXiv190105173F
We use spectra from CARMENES, the Calar Alto high-Resolution search
for M dwarfs with Exo-earths with Near-infrared and optical Echelle
Spectrographs, to search for periods in chromospheric indices in
16 M0-M2 dwarfs. We measure spectral indices in the Hα, the Ca
II infrared triplet (IRT), and the Na I D lines to study which of
these indices are best-suited to finding rotation periods in these
stars. Moreover, we test a number of different period-search algorithms,
namely the string length method, the phase dispersion minimisation,
the generalized Lomb-Scargle periodogram, and the Gaussian process
regression with quasi-periodic kernel. We find periods in four stars
using Hα and in five stars using the Ca II IRT, two of which have
not been found before. Our results show that both Hα and the Ca II
IRT lines are well suited for period searches, with the Ca II IRT
index performing slightly better than Hα. Unfortunately, the Na I D
lines are strongly affected by telluric airglow, and we could not find
any rotation period using this index. Further, different definitions
of the line indices have no major impact on the results. Comparing
the different search methods, the string length method and the phase
dispersion minimisation perform worst, while Gaussian process models
produce the smallest numbers of false positives and non-detections.
Title: Stellar atmospheric parameters of FGK-type stars from
high-resolution optical and near-infrared CARMENES spectra
Authors: Marfil, E.; Montes, D.; Tabernero, H. M.; Caballero, J. A.;
González Hernández, J. I.; Kaminski, A.; Simón-Díaz, S.; Jeffers,
S. V.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners, A.; Seifert,
W.; CARMENES Consortium
Bibcode: 2019hsax.conf..409M
Altcode:
With the aim of using classic spectroscopic methods with high resolution
and high signal-to-noise ratio in the NIR spectral window, we made a
selection of 66 FGK-type stars observed with CARMENES, the brand-new,
ultra-stable, double-channel spectrograph at the Spanish-German
3.5m Calar Alto telescope. These spectra are part of a CARMENES
stellar library. We applied the equivalent width method to derive
the spectroscopic stellar parameters (T_{eff}, log{g}, {ξ}_{micro},
and [Fe/H]) using the StePar code along with four new iron line lists
covering the whole CARMENES spectral range (550 - 1700 nm).
Title: The CARMENES search for exoplanets around M
dwarfs. Chromospheric modeling of M 2-3 V stars with PHOENIX
Authors: Hintz, D.; Fuhrmeister, B.; Czesla, S.; Schmitt, J. H. M. M.;
Johnson, E. N.; Schweitzer, A.; Caballero, J. A.; Zechmeister, M.;
Jeffers, S. V.; Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.;
Anglada-Escudé, G.; Bauer, F. F.; Béjar, V. J. S.; Cortés-Contreras,
M.; Dreizler, S.; Galadí-Enríquez, D.; Guenther, E. W.; Hauschildt,
P. H.; Kaminski, A.; Kürster, M.; Lafarga, M.; López del Fresno,
M.; Montes, D.; Morales, J. C.; Passegger, V. M.; Seifert, W.
Bibcode: 2019A&A...623A.136H
Altcode: 2019arXiv190203992H
Chromospheric modeling of observed differences in stellar activity
lines is imperative to fully understand the upper atmospheres of
late-type stars. We present one-dimensional parametrized chromosphere
models computed with the atmosphere code PHOENIX using an underlying
photosphere of 3500 K. The aim of this work is to model chromospheric
lines of a sample of 50 M2-3 dwarfs observed in the framework of the
CARMENES, the Calar Alto high-Resolution search for M dwarfs with
Exo-earths with Near-infrared and optical Echelle Spectrographs,
exoplanet survey. The spectral comparison between observed data and
models is performed in the chromospheric lines of Na I D2,
Hα, and the bluest Ca II infrared triplet line to obtain best-fit
models for each star in the sample. We find that for inactive stars a
single model with a VAL C-like temperature structure is sufficient to
describe simultaneously all three lines adequately. Active stars are
rather modeled by a combination of an inactive and an active model, also
giving the filling factors of inactive and active regions. Moreover, the
fitting of linear combinations on variable stars yields relationships
between filling factors and activity states, indicating that more
active phases are coupled to a larger portion of active regions on
the surface of the star.
Title: The CARMENES search for exoplanets around M dwarfs. Activity
indicators at visible and near-infrared wavelengths
Authors: Schöfer, P.; Jeffers, S. V.; Reiners, A.; Shulyak,
D.; Fuhrmeister, B.; Johnson, E. N.; Zechmeister, M.; Ribas, I.;
Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Anglada-Escudé,
G.; Bauer, F. F.; Béjar, V. J. S.; Cortés-Contreras, M.; Dreizler,
S.; Guenther, E. W.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes,
D.; Morales, J. C.; Pedraz, S.; Tal-Or, L.
Bibcode: 2019A&A...623A..44S
Altcode: 2019arXiv190108861S
Context. The Calar Alto high-Resolution search for M dwarfs with
Exo-earths with Near-infrared and optical Echelle Spectrographs
(CARMENES) survey is searching for Earth-like planets orbiting M dwarfs
using the radial velocity method. Studying the stellar activity of
the target stars is important to avoid false planet detections and to
improve our understanding of the atmospheres of late-type stars.
Aims: In this work we present measurements of activity indicators
at visible and near-infrared wavelengths for 331 M dwarfs observed
with CARMENES. Our aim is to identify the activity indicators that
are most sensitive and easiest to measure, and the correlations among
these indicators. We also wish to characterise their variability.
Methods: Using a spectral subtraction technique, we measured
pseudo-equivalent widths of the He I D3, Hα, He I λ10833
Å, and Pa β lines, the Na I D doublet, and the Ca II infrared triplet,
which have a chromospheric component in active M dwarfs. In addition,
we measured an index of the strength of two TiO and two VO bands,
which are formed in the photosphere. We also searched for periodicities
in these activity indicators for all sample stars using generalised
Lomb-Scargle periodograms.
Results: We find that the most
slowly rotating stars of each spectral subtype have the strongest Hα
absorption. Hα is correlated most strongly with He I D3,
whereas Na I D and the Ca II infrared triplet are also correlated
with Hα. He I λ10833 Å and Paβ show no clear correlations with
the other indicators. The TiO bands show an activity effect that does
not appear in the VO bands. We find that the relative variations of
Hα and He I D3 are smaller for stars with higher activity
levels, while this anti-correlation is weaker for Na I D and the Ca II
infrared triplet, and is absent for He I λ10833 Å and Paβ. Periodic
variation with the rotation period most commonly appears in the TiO
bands, Hα, and in the Ca II infrared triplet. The full version
of Table A.1 is 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/623/A44
Title: The rotationally modulated polarization of ξ Boo A
Authors: Cotton, Daniel V.; Evensberget, Dag; Marsden, Stephen C.;
Bailey, Jeremy; Zhao, Jinglin; Kedziora-Chudczer, Lucyna; Carter,
Bradley D.; Bott, Kimberly; Vidotto, Aline A.; Petit, Pascal; Morin,
Julien; Jeffers, Sandra V.
Bibcode: 2019MNRAS.483.1574C
Altcode: 2018arXiv181108534C; 2018MNRAS.tmp.3032C
We have observed the active star ξ Boo A (HD 131156A) with high
precision broadband linear polarimetry contemporaneously with circular
spectropolarimetry. We find both signals are modulated by the 6.43 d
rotation period of ξ Boo A. The signals from the two techniques are
0.25 out of phase, consistent with the broadband linear polarization
resulting from differential saturation of spectral lines in the
global transverse magnetic field. The mean magnitude of the linear
polarization signal is ∼4 ppm G-1 but its structure is
complex and the amplitude of the variations suppressed relative to the
longitudinal magnetic field. The result has important implications for
current attempts to detect polarized light from hot Jupiters orbiting
active stars in the combined light of the star and planet. In such
work stellar activity will manifest as noise, both on the time-scale
of stellar rotation, and on longer time-scales - where changes in
activity level will manifest as a baseline shift between observing runs.
Title: The solar wind in time - II. 3D stellar wind structure and
radio emission
Authors: Ó Fionnagáin, D.; Vidotto, A. A.; Petit, P.; Folsom,
C. P.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; do Nascimento,
J. -D.; BCool Collaboration
Bibcode: 2019MNRAS.483..873O
Altcode: 2018arXiv181105356F; 2018arXiv181105356O; 2018MNRAS.tmp.2994O
In this work, we simulate the evolution of the solar wind along its
main-sequence lifetime and compute its thermal radio emission. To study
the evolution of the solar wind, we use a sample of solar mass stars
at different ages. All these stars have observationally reconstructed
magnetic maps, which are incorporated in our 3D magnetohydrodynamic
simulations of their winds. We show that angular-momentum loss
and mass-loss rates decrease steadily on evolutionary time-scales,
although they can vary in a magnetic cycle time-scale. Stellar winds
are known to emit radiation in the form of thermal bremsstrahlung
in the radio spectrum. To calculate the expected radio fluxes from
these winds, we solve the radiative transfer equation numerically
from first principles. We compute continuum spectra across the
frequency range 100 MHz to 100 GHz and find maximum radio flux
densities ranging from 0.05 to 2.2 μJy. At a frequency of 1 GHz and
a normalized distance of d = 10 pc, the radio flux density follows
0.24 (Ω/Ω⊙)0.9 (d/[10pc])-2μJy,
where Ω is the rotation rate. This means that the best candidates
for stellar wind observations in the radio regime are faster rotators
within distances of 10 pc, such as κ1 Ceti (0.73 μJy) and
χ1 Ori (2.2 μJy). These flux predictions provide a guide
to observing solar-type stars across the frequency range 0.1-100 GHz
in the future using the next generation of radio telescopes, such as
ngVLA and Square Kilometre Array.
Title: The CARMENES search for exoplanets around M dwarfs. The
enigmatic planetary system GJ 4276: one eccentric planet or two
planets in a 2:1 resonance?
Authors: Nagel, E.; Czesla, S.; Schmitt, J. H. M. M.; Dreizler,
S.; Anglada-Escudé, G.; Rodríguez, E.; Ribas, I.; Reiners, A.;
Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Aceituno, J.; Béjar,
V. J. S.; Cortés-Contreras, M.; González-Cuesta, L.; Guenther, E. W.;
Henning, T.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga,
M.; López-González, M. J.; Montes, D.; Morales, J. C.; Passegger,
V. M.; Rodríguez-López, C.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2019A&A...622A.153N
Altcode: 2019arXiv190102367N
We report the detection of a Neptune-mass exoplanet around the M4.0
dwarf GJ 4276 (G 232-070) based on radial velocity (RV) observations
obtained with the CARMENES spectrograph. The RV variations of GJ
4276 are best explained by the presence of a planetary companion that
has a minimum mass of mb sin i ≈ 16 M⊕ on a
Pb = 13.35 day orbit. The analysis of the activity indicators
and spectral diagnostics exclude stellar induced RV perturbations
and prove the planetary interpretation of the RV signal. We show
that a circular single-planet solution can be excluded by means of
a likelihood ratio test. Instead, we find that the RV variations can
be explained either by an eccentric orbit or interpreted as a pair of
planets on circular orbits near a period ratio of 2:1. Although the
eccentric single-planet solution is slightly preferred, our statistical
analysis indicates that none of these two scenarios can be rejected
with high confidence using the RV time series obtained so far. Based
on the eccentric interpretation, we find that GJ 4276 b is the most
eccentric (eb = 0.37) exoplanet around an M dwarf with such
a short orbital period known today. Photometric measurements
and Table C.1 are 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/622/A153
Title: VizieR Online Data Catalog: Barnard's star radial velocity
curve (Ribas+, 2018)
Authors: Ribas, I.; Tuomi, M.; Reiners, A.; Butler, R. P.;
Morales, J. C.; Perger, M.; Dreizler, S.; Rodriguez-Lopez, C.;
Gonzalez Hernandez, J. I.; Rosich, A.; Feng, F.; Trifonov, T.; Vogt,
S. S.; Caballero, J. A.; Hatzes, A.; Herrero, E.; Jeffers, S. V.;
Lafarga, M.; Murgas, F.; Nelson, R. P.; Rodriguez, E.; Strachan,
J. B. P.; Tal-Or, L.; Teske, J.; Toledo-Padron, B.; Zechmeister, M.;
Quirrenbach, A.; Amado, P. J.; Azzaro, M.; Bejar, V. J. S.; Barnes,
J. R.; Berdinas, Z. M.; Burt, J.; Coleman, G.; Cortes-Contreras, M.;
Crane, J.; Engle, S. G.; Guinan, E. F.; Haswell, C. A.; Henning, T.;
Holden, B.; Jenkins, J.; Jones, H. R. A.; Kaminski, A.; Kiraga, M.;
Kurster, M.; Lee, M. H.; Lopez-Gonzalez, M. J.; Montes, D.; Morin, J.;
Ofir, A.; Palle, E.; Rebolo, R.; Reffert, S.; Schweitzer, A.; Seifert,
W.; Shectman, S. A.; Staab, D.; Street, R. A.; Suarez Mascareno, A.;
Tsapras, Y.; Wang, S. X.; Anglada-Escude, G.
Bibcode: 2019yCatp038056301R
Altcode:
An early analysis of archival radial-velocity datasets of Barnard's
star up to 2015 indicated the presence of at least one significant
signal, which had a period of about 230 days, but with rather poor
sampling. To elucidate its presence and nature we undertook an intensive
monitoring campaign with the CARMENES spectrometer, collecting precise
radial-velocity measurements on every possible night during 2016 and
2017. We also obtained overlapping observations with the European
Southern Observatory (ESO) HARPS and the HARPS-N instruments. The
combined Doppler monitoring of Barnard's star, including archival and
newly acquired observations, resulted in 771 radial-velocity epochs
(nightly averages), with typical individual precisions of 0.9-1.8m/s,
obtained over a timespan of more than 20 years from seven different
facilities, and yielded eight independent datasets. (4 data files).
Title: VizieR Online Data Catalog: Photometry & RV follow-up
observations of K2-18 (Sarkis+, 2018)
Authors: Sarkis, P.; Henning, T.; Kurster, M.; Trifonov, T.;
Zechmeister, M.; Tal-Or, L.; Anglada-Escude, G.; Hatzes, A. P.;
Lafarga, M.; Dreizler, S.; Ribas, I.; Caballero, J. A.; Reiners,
A.; Mallonn, M.; Morales, J. C.; Kaminski, A.; Aceituno, J.; Amado,
P. J.; Bejar, V. J. S.; Hagen, H. -J.; Jeffers, S.; Quirrenbach, A.;
Launhardt, R.; Marvin, C.; Montes, D.
Bibcode: 2019yCat..51550257S
Altcode:
We monitored the host star K2-18 for photometric variability with
the robotic 1.2 m twin-telescope STELLA on Tenerife (Strassmeier et
al. 2004AN....325..527S) and its wide-field imager WiFSIP. From 2017
February until 2017 June, we obtained blocks of four exposures in
Johnson B and four exposures in Cousins R over 33 nights. The exposure
time was 120 s in B and 60 s in R. We monitored K2-18 between 2016
December and 2017 June with CARMENES. CARMENES (Calar Alto search
for M dwarfs with Exo-earths with Near-infrared and optical Echelle
Spectrographs) is a pair of high-resolution echelle spectrographs
(Quirrenbach et al. 2014SPIE.9147E..1FQ) mounted on the 3.5 m telescope
of the Calar Alto Observatory (CAHA) in Spain. The VIS channel covers
the wavelength range from 0.52 to 0.96 μm and has a spectral resolution
R=94600 (Quirrenbach et al. 2016SPIE.9908E..12Q), with a demonstrated
precision similar to HARPS and better than Keck/HIRES (Trifonov et
al. 2018, J/A+A/609/A117). (3 data files).
Title: CARMENES input catalogue of M dwarfs. IV. New rotation periods
from photometric time series
Authors: Díez Alonso, E.; Caballero, J. A.; Montes, D.; de Cos Juez,
F. J.; Dreizler, S.; Dubois, F.; Jeffers, S. V.; Lalitha, S.; Naves,
R.; Reiners, A.; Ribas, I.; Vanaverbeke, S.; Amado, P. J.; Béjar,
V. J. S.; Cortés-Contreras, M.; Herrero, E.; Hidalgo, D.; Kürster,
M.; Logie, L.; Quirrenbach, A.; Rau, S.; Seifert, W.; Schöfer, P.;
Tal-Or, L.
Bibcode: 2019A&A...621A.126D
Altcode: 2018arXiv181003338D
Aims: The main goal of this work is to measure rotation periods
of the M-type dwarf stars being observed by the CARMENES exoplanet
survey to help distinguish radial-velocity signals produced by magnetic
activity from those produced by exoplanets. Rotation periods are also
fundamental for a detailed study of the relation between activity and
rotation in late-type stars.
Methods: We look for significant
periodic signals in 622 photometric time series of 337 bright, nearby M
dwarfs obtained by long-time baseline, automated surveys (MEarth, ASAS,
SuperWASP, NSVS, Catalina, ASAS-SN, K2, and HATNet) and for 20 stars
which we obtained with four 0.2-0.8 m telescopes at high geographical
latitudes.
Results: We present 142 rotation periods (73 new) from
0.12 d to 133 d and ten long-term activity cycles (six new) from 3.0
a to 11.5 a. We compare our determinations with those in the existing
literature; we investigate the distribution of Prot in the
CARMENES input catalogue, the amplitude of photometric variability,
and their relation to v sini and pEW(Hα); and we identify three
very active stars with new rotation periods between 0.34 d and
23.6 d. Tables A.1 and A.2, and tables of the photometric
measurements 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/621/A126
Title: Detection of He I λ10830 Å absorption on HD 189733 b with
CARMENES high-resolution transmission spectroscopy
Authors: Salz, M.; Czesla, S.; Schneider, P. C.; Nagel, E.; Schmitt,
J. H. M. M.; Nortmann, L.; Alonso-Floriano, F. J.; López-Puertas, M.;
Lampón, M.; Bauer, F. F.; Snellen, I. A. G.; Pallé, E.; Caballero,
J. A.; Yan, F.; Chen, G.; Sanz-Forcada, J.; Amado, P. J.; Quirrenbach,
A.; Ribas, I.; Reiners, A.; Béjar, V. J. S.; Casasayas-Barris, N.;
Cortés-Contreras, M.; Dreizler, S.; Guenther, E. W.; Henning, T.;
Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Lara, L. M.;
Molaverdikhani, K.; Montes, D.; Morales, J. C.; Sánchez-López, A.;
Seifert, W.; Zapatero Osorio, M. R.; Zechmeister, M.
Bibcode: 2018A&A...620A..97S
Altcode: 2018arXiv181202453S
We present three transit observations of HD 189733 b obtained with
the high-resolution spectrograph CARMENES at Calar Alto. A strong
absorption signal is detected in the near-infrared He I triplet at
10830 Å in all three transits. During mid-transit, the mean absorption
level is 0.88 ± 0.04% measured in a ±10 km s-1 range at
a net blueshift of - 3.5 ± 0.4 km s-1 (10829.84-10830.57
Å). The absorption signal exhibits radial velocities of + 6.5 ±
3.1 km s-1 and - 12.6 ± 1.0 km s-1 during
ingress and egress, respectively; all radial velocities are measured
in the planetary rest frame. We show that stellar activity related
pseudo-signals interfere with the planetary atmospheric absorption
signal. They could contribute as much as 80% of the observed signal
and might also affect the observed radial velocity signature, but
pseudo-signals are very unlikely to explain the entire signal. The
observed line ratio between the two unresolved and the third line
of the He I triplet is 2.8 ± 0.2, which strongly deviates from the
value expected for an optically thin atmospheres. When interpreted
in terms of absorption in the planetary atmosphere, this favors a
compact helium atmosphere with an extent of only 0.2 planetary radii
and a substantial column density on the order of 4 × 1012
cm-2. The observed radial velocities can be understood either
in terms of atmospheric circulation with equatorial superrotation
or as a sign of an asymmetric atmospheric component of evaporating
material. We detect no clear signature of ongoing evaporation, like pre-
or post-transit absorption, which could indicate material beyond the
planetary Roche lobe, or radial velocities in excess of the escape
velocity. These findings do not contradict planetary evaporation,
but only show that the detected helium absorption in HD 189733 b does
not trace the atmospheric layers that show pronounced escape signatures.
Title: The CARMENES search for exoplanets around M dwarfs. The warm
super-Earths in twin orbits around the mid-type M dwarfs Ross 1020
(GJ 3779) and LP 819-052 (GJ 1265)
Authors: Luque, R.; Nowak, G.; Pallé, E.; Kossakowski, D.; Trifonov,
T.; Zechmeister, M.; Béjar, V. J. S.; Cardona Guillén, C.;
Tal-Or, L.; Hidalgo, D.; Ribas, I.; Reiners, A.; Caballero, J. A.;
Amado, P. J.; Quirrenbach, A.; Aceituno, J.; Cortés-Contreras, M.;
Díez-Alonso, E.; Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers,
S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Morales,
J. C.; Passegger, V. M.; Schmitt, J. H. M. M.; Schweitzer, A.
Bibcode: 2018A&A...620A.171L
Altcode: 2018arXiv181007572L
We announce the discovery of two planetary companions orbiting
around the low-mass stars Ross 1020 (GJ 3779, M4.0V) and LP 819-052
(GJ 1265, M4.5V). The discovery is based on the analysis of CARMENES
radial velocity (RV) observations in the visual channel as part of
its survey for exoplanets around M dwarfs. In the case of GJ 1265,
CARMENES observations were complemented with publicly available Doppler
measurements from HARPS. The datasets reveal two planetary companions,
one for each star, that share very similar properties: minimum
masses of 8.0 ± 0.5 M⊕ and 7.4 ± 0.5 M⊕
in low-eccentricity orbits with periods of 3.023 ± 0.001 d and 3.651
± 0.001 d for GJ 3779 b and GJ 1265 b, respectively. The periodic
signals around 3 d found in the RV data have no counterpart in any
spectral activity indicator. Furthermore, we collected available
photometric data for the two host stars, which confirm that the
additional Doppler variations found at periods of approximately 95 d
can be attributed to the rotation of the stars. The addition of these
planets to a mass-period diagram of known planets around M dwarfs
suggests a bimodal distribution with a lack of short-period low-mass
planets in the range of 2-5 M⊕. It also indicates that
super-Earths (>5 M⊕) currently detected by RV and
transit techniques around M stars are usually found in systems dominated
by a single planet. The RV and formal uncertainties of GJ 3779
and GJ 1265 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/620/A171
Title: Direct evidence of a full dipole flip during the magnetic
cycle of a sun-like star
Authors: Boro Saikia, S.; Lueftinger, T.; Jeffers, S. V.; Folsom,
C. P.; See, V.; Petit, P.; Marsden, S. C.; Vidotto, A. A.; Morin,
J.; Reiners, A.; Guedel, M.; BCool Collaboration
Bibcode: 2018A&A...620L..11B
Altcode: 2018arXiv181111671B
Context. The behaviour of the large-scale dipolar field, during a
star's magnetic cycle, can provide valuable insight into the stellar
dynamo and associated magnetic field manifestations such as stellar
winds.
Aims: We investigate the temporal evolution of the
dipolar field of the K dwarf 61 Cyg A using spectropolarimetric
observations covering nearly one magnetic cycle equivalent to
two chromospheric activity cycles.
Methods: The large-scale
magnetic field geometry is reconstructed using Zeeman Doppler imaging,
a tomographic inversion technique. Additionally, the chromospheric
activity is also monitored.
Results: The observations provide
an unprecedented sampling of the large-scale field over a single
magnetic cycle of a star other than the Sun. Our results show that 61
Cyg A has a dominant dipolar geometry except at chromospheric activity
maximum. The dipole axis migrates from the southern to the northern
hemisphere during the magnetic cycle. It is located at higher latitudes
at chromospheric activity cycle minimum and at middle latitudes during
cycle maximum. The dipole is strongest at activity cycle minimum and
much weaker at activity cycle maximum.
Conclusions: The behaviour
of the large-scale dipolar field during the magnetic cycle resembles
the solar magnetic cycle. Our results are further confirmation that
61 Cyg A indeed has a large-scale magnetic geometry that is comparable
to the Sun's, despite being a slightly older and cooler K dwarf.
Title: VizieR Online Data Catalog: GJ 4276 radial velocity curve
(Nagel+, 2019)
Authors: Nagel, E.; Czesla, S.; Schmitt, J. H. M. M.; Dreizler,
S.; Anglada-Escude, G.; Rodriguez, E.; Ribas, I.; Reiners, A.;
Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Aceituno, J.; Bejar,
V. J. S.; Cortes-Contreras, M.; Gonzalez-Cuesta, L.; Guenther, E. W.;
Henning, T.; Jeffers, S. V.; Kaminski, A.; Kuerster, M.; Lafarga, M.;
Lopez-Gonzalez, M. J.; Montes, D.; Morales, J. C. Passegger V. M.;
Rodriguez-Lopez, C.; Schweitzer, A.; Zechmeister, M.
Bibcode: 2018yCat..36220153N
Altcode:
We analyzed radial velocity data from the CARMENES VIS channel. The
RVs are corrected for barycentric motion and secular acceleration. The
CARMENES measurements were taken in the context of the CARMENES search
for exoplanets around M dwarfs. The CARMENES instrument consists
of two channels: the VIS channel obtains spectra at a resolution of
R=94600 in the wavelength range 520-960nm, while the NIR channel yields
spectra of R=80400 covering 960-1710nm. Both channels are calibrated
in wavelength with hollow-cathode lamps and use temperature- and
pressure-stabilized Fabry-Perot etalons to interpolate the wavelength
solution and simultaneously monitor the spectrograph drift during
nightly operations (Bauer et al., 2015A&A...581A.117B). To
determine the stellar rotation period, we obtained V band photometry
with the T150 telescope located at the Sierra Nevada Observatory (SNO)
in Spain. (2 data files).
Title: VizieR Online Data Catalog: Planet-hosting solar-type stars
magnetic fields (Mengel+, 2017)
Authors: Mengel, M. W.; Marsden, S. C.; Carter, B. D.; Horner, J.;
King, R.; Fares, R.; Jeffers, S. V.; Petit, P.; Vidotto, A. A.; Morin,
J.; Bcool, C.
Bibcode: 2018yCat..74652734M
Altcode:
We present an investigation of the large-scale magnetic field of
19 additional solar-type stars for the BCool survey (Marsden et
al. 2014). We expanded our sample of planet-hosting stars by adding
the previously observed planet-host in the BCool survey. (5
data files).
Title: The CARMENES search for exoplanets around M dwarfs. Nine new
double-line spectroscopic binary stars
Authors: Baroch, D.; Morales, J. C.; Ribas, I.; Tal-Or, L.;
Zechmeister, M.; Reiners, A.; Caballero, J. A.; Quirrenbach, A.;
Amado, P. J.; Dreizler, S.; Lalitha, S.; Jeffers, S. V.; Lafarga, M.;
Béjar, V. J. S.; Colomé, J.; Cortés-Contreras, M.; Díez-Alonso,
E.; Galadí-Enríquez, D.; Guenther, E. W.; Hagen, H. -J.; Henning,
T.; Herrero, E.; Kürster, M.; Montes, D.; Nagel, E.; Passegger,
V. M.; Perger, M.; Rosich, A.; Schweitzer, A.; Seifert, W.
Bibcode: 2018A&A...619A..32B
Altcode: 2018arXiv180806895B
Context. The CARMENES spectrograph is surveying ∼300 M dwarf stars
in search for exoplanets. Among the target stars, spectroscopic binary
systems have been discovered, which can be used to measure fundamental
properties of stars.
Aims: Using spectroscopic observations, we
determine the orbital and physical properties of nine new double-line
spectroscopic binary systems by analysing their radial velocity
curves.
Methods: We use two-dimensional cross-correlation
techniques to derive the radial velocities of the targets, which are
then employed to determine the orbital properties. Photometric data from
the literature are also analysed to search for possible eclipses and
to measure stellar variability, which can yield rotation periods.
Results: Out of the 342 stars selected for the CARMENES survey, 9
have been found to be double-line spectroscopic binaries, with periods
ranging from 1.13 to ∼8000 days and orbits with eccentricities up
to 0.54. We provide empirical orbital properties and minimum masses
for the sample of spectroscopic binaries. Absolute masses are also
estimated from mass-luminosity calibrations, ranging between ∼0.1 and
∼0.6 M⊙.
Conclusions: These new binary systems
increase the number of double-line M dwarf binary systems with known
orbital parameters by 15%, and they have lower mass ratios on average.
Title: A candidate super-Earth planet orbiting near the snow line
of Barnard's star
Authors: Ribas, I.; Tuomi, M.; Reiners, A.; Butler, R. P.; Morales,
J. C.; Perger, M.; Dreizler, S.; Rodríguez-López, C.; González
Hernández, J. I.; Rosich, A.; Feng, F.; Trifonov, T.; Vogt, S. S.;
Caballero, J. A.; Hatzes, A.; Herrero, E.; Jeffers, S. V.; Lafarga, M.;
Murgas, F.; Nelson, R. P.; Rodríguez, E.; Strachan, J. B. P.; Tal-Or,
L.; Teske, J.; Toledo-Padrón, B.; Zechmeister, M.; Quirrenbach, A.;
Amado, P. J.; Azzaro, M.; Béjar, V. J. S.; Barnes, J. R.; Berdiñas,
Z. M.; Burt, J.; Coleman, G.; Cortés-Contreras, M.; Crane, J.;
Engle, S. G.; Guinan, E. F.; Haswell, C. A.; Henning, Th.; Holden,
B.; Jenkins, J.; Jones, H. R. A.; Kaminski, A.; Kiraga, M.; Kürster,
M.; Lee, M. H.; López-González, M. J.; Montes, D.; Morin, J.; Ofir,
A.; Pallé, E.; Rebolo, R.; Reffert, S.; Schweitzer, A.; Seifert,
W.; Shectman, S. A.; Staab, D.; Street, R. A.; Suárez Mascareño,
A.; Tsapras, Y.; Wang, S. X.; Anglada-Escudé, G.
Bibcode: 2018Natur.563..365R
Altcode: 2018arXiv181105955R
Barnard's star is a red dwarf, and has the largest proper motion
(apparent motion across the sky) of all known stars. At a distance of
1.8 parsecs1, it is the closest single star to the Sun; only
the three stars in the α Centauri system are closer. Barnard's star is
also among the least magnetically active red dwarfs known2,3
and has an estimated age older than the Solar System. Its properties
make it a prime target for planetary searches; various techniques with
different sensitivity limits have been used previously, including
radial-velocity imaging4-6, astrometry7,8 and
direct imaging9, but all ultimately led to negative or null
results. Here we combine numerous measurements from high-precision
radial-velocity instruments, revealing the presence of a low-amplitude
periodic signal with a period of 233 days. Independent photometric
and spectroscopic monitoring, as well as an analysis of instrumental
systematic effects, suggest that this signal is best explained
as arising from a planetary companion. The candidate planet around
Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times
that of Earth, orbiting near its snow line (the minimum distance from
the star at which volatile compounds could condense). The combination
of all radial-velocity datasets spanning 20 years of measurements
additionally reveals a long-term modulation that could arise from
a stellar magnetic-activity cycle or from a more distant planetary
object. Because of its proximity to the Sun, the candidate planet has
a maximum angular separation of 220 milliarcseconds from Barnard's
star, making it an excellent target for direct imaging and astrometric
observations in the future.
Title: VizieR Online Data Catalog: Radial velocities of GJ 3779 and
GJ 1265 (Luque+, 2018)
Authors: Luque, R.; Nowak, G.; Palle, E.; Kossakowski, D.; Trifonov,
T.; Zechmeister, M.; Bejar, V. J. S.; Cardona Guillen, C.; Tal-Or, L.;
Hidalgo, D.; Ribas, I.; Reiners, A.; Caballero, J. A.; Amado, P. J.;
Quirrenbach, A.; Aceituno, J.; Cortes-Contreras, M.; Diez-Alonso, E.;
Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers, S. V.; Kaminski,
A.; Kuerster, M.; Lafarga, M.; Montes, D.; Morales, J. C.; Passegger,
V. M.; Schmitt, J. H. M. M.; Schweitzer, A.
Bibcode: 2018yCat..36200171L
Altcode:
We analyzed radial velocity data from the CARMENES VIS channel for GJ
3779, and from the CARMENES VIS channel and HARPS for GJ 1265. All the
RVs are corrected for barycentric motion and secular acceleration. The
CARMENES measurements were taken in the context of the CARMENES search
for exoplanets around M dwarfs. The CARMENES instrument consists of two
channels: the VIS channel obtains spectra at a resolution of R=94600 in
the wavelength range 520-960nm, while the NIR channel yields spectra of
R=80400 covering 960-1710nm. Both channels are calibrated in wavelength
with hollow-cathode lamps and use temperature- and pressure-stabilized
Fabry-Perot etalons to interpolate the wavelength solution and
simultaneously monitor the spectrograph drift during nightly operations
(Bauer et al., 2015A&A...581A.117B). (2 data files).
Title: The CARMENES search for exoplanets around M dwarfs. A
Neptune-mass planet traversing the habitable zone around HD 180617
Authors: Kaminski, A.; Trifonov, T.; Caballero, J. A.; Quirrenbach,
A.; Ribas, I.; Reiners, A.; Amado, P. J.; Zechmeister, M.; Dreizler,
S.; Perger, M.; Tal-Or, L.; Bonfils, X.; Mayor, M.; Astudillo-Defru,
N.; Bauer, F. F.; Béjar, V. J. S.; Cifuentes, C.; Colomé, J.;
Cortés-Contreras, M.; Delfosse, X.; Díez-Alonso, E.; Forveille, T.;
Guenther, E. W.; Hatzes, A. P.; Henning, Th.; Jeffers, S. V.; Kürster,
M.; Lafarga, M.; Luque, R.; Mandel, H.; Montes, D.; Morales, J. C.;
Passegger, V. M.; Pedraz, S.; Reffert, S.; Sadegi, S.; Schweitzer,
A.; Seifert, W.; Stahl, O.; Udry, S.
Bibcode: 2018A&A...618A.115K
Altcode: 2018arXiv180801183K
Despite their activity, low-mass stars are of particular importance
for the search of exoplanets by the means of Doppler spectroscopy,
as planets with lower masses become detectable. We report on the
discovery of a planetary companion around HD 180617, a bright (J =
5.58 mag), low-mass (M = 0.45M⊙) star of spectral type
M2.5 V. The star, located at a distance of 5.9 pc, is the primary of
the high proper motion binary system containing vB 10, a star with
one of the lowest masses known in most of the twentieth century. Our
analysis is based on new radial velocity (RV) measurements made at
red-optical wavelengths provided by the high-precision spectrograph
CARMENES, which was designed to carry out a survey for Earth-like
planets around M dwarfs. The available CARMENES data are augmented
by archival Doppler measurements from HIRES and HARPS. Altogether,
the RVs span more than 16 yr. The modeling of the RV variations,
with a semi-amplitude of K = 2.85-0.25+0.16
m s-1, yields a Neptune-like planet with a minimum
mass of 12.2-1.4+1.0 M⊕ on a
105.90-0.10+0.09 d circumprimary orbit, which
is partly located in the host star's habitable zone. The analysis of
time series of common activity indicators does not show any dependence
on the detected RV signal. The discovery of HD 180617 b not only adds
information to a currently hardly filled region of the mass-period
diagram of exoplanets around M dwarfs, but the investigated system
becomes the third known binary consisting of M dwarfs and hosting
an exoplanet in an S-type configuration. Its proximity makes
it an attractive candidate for future studies. The RV data
(Table C.1) 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/618/A115
Title: The relation between stellar magnetic field geometry and
chromospheric activity cycles - II The rapid 120-day magnetic cycle
of τ Bootis
Authors: Jeffers, S. V.; Mengel, M.; Moutou, C.; Marsden, S. C.;
Barnes, J. R.; Jardine, M. M.; Petit, P.; Schmitt, J. H. M. M.; See,
V.; Vidotto, A. A.; BCool Collaboration
Bibcode: 2018MNRAS.479.5266J
Altcode: 2018arXiv180509769J; 2018MNRAS.tmp.1654J
One of the aims of the BCool programme is to search for cycles in other
stars and to understand how similar they are to the Sun. In this paper,
we aim to monitor the evolution of τ Boo's large-scale magnetic field
using high-cadence observations covering its chromospheric activity
maximum. For the first time, we detect a polarity switch that is in
phase with τ Boo's 120-day chromospheric activity maximum and its
inferred X-ray activity cycle maximum. This means that τ Boo has a
very fast magnetic cycle of only 240 days. At activity maximum τ Boo's
large-scale field geometry is very similar to the Sun at activity
maximum: it is complex and there is a weak dipolar component. In
contrast, we also see the emergence of a strong toroidal component
which has not been observed on the Sun, and a potentially overlapping
butterfly pattern where the next cycle begins before the previous one
has finished.
Title: VizieR Online Data Catalog: CARMENES input catalogue of M
dwarfs. IV. (Diez Alonso+ 2019)
Authors: Diez Alonso, E.; Caballero, J. A.; Montes, D.; de Cos Juez,
F. J.; Dreizler, S.; Dubois, F.; Jeffers, S. V.; Lalitha, S.; Naves,
R.; Reiners, A.; Ribas, I.; Vanaverbeke, S.; Amado, P. J.; Bejar,
V. J. S.; Cortes-Contreras, M.; Herrero, E.; Hidalgo, D.; Kuerster,
M.; Logie, L.; Quirrenbach, A.; Rau, S.; Seifert, W.; Schoefer, P.;
Tal-Or, L.
Bibcode: 2018yCat..36210126D
Altcode:
During guaranteed time observations (GTOs), the double-channel
CARMENES spectrograph has so far observed a sample of 336 bright,
nearby M dwarfs with the goal of detecting low-mass planets in their
habitable zone with the radial-velocity method (Quirrenbach et al.,
2015, in 18th Cambridge Workshop on Cool Stars, Stellar Systems, and
the Sun, Proceedings of the conference held at Lowell Observatory,
8-14 June 2014. Edited by G. van Belle and H.C. Harris., pp. 897-906;
Reiners et al., 2018, Cat. J/A+A/612/A49). Of these, 324 were presented
by Reiners et al. (2018, Cat. J/A+A/612/A49), three did not have enough
CARMENES observations at the time of preparing the spectral templates
for the study, and nine are new spectroscopic binaries (Baroch et
al., 2018, A&A, in prep, arXiv:1808.06895). Here, we investigate
the photometric variability of these 336 M dwarfs and of G 34-23 AB
(J01221+221AB), which Cortes-Contreras et al. (2017, Cat. J/A+A/597/A47)
found to be a close physical binary just before GTO start. This results
in a final sample size of 337 stars. (2 data files).
Title: VizieR Online Data Catalog: A Neptune-mass planet traversing
the habitable zone around HD 180617 (Kaminski+, 2018)
Authors: Kaminski, A.; Trifonov, T.; Caballero, J. A.; Quirrenbach,
A.; Ribas, I.; Reiners, A.; Amado, P. J.; Zechmeister, M.; Dreizler,
S.; Perger, M.; Tal-Or, L.; Bonfils, X.; Mayor, M.; Astudillo-Defru,
N.; Bauer, F. F.; Bejar, V. J. S.; Cifuentes, C.; Colome, J.;
Cortes-Contreras, M.; Delfosse, X.; Diez-Alonso, E.; Forveille, T.;
Guenther, E. W.; Hatzes, A. P.; Henning, Th.; Jeffers, S. V.; Kuerster,
M.; Lafarga, M.; Luque, R.; Mandel, H.; Montes, D.; Morales, J. C.;
Passegger, V. M.; Pedraz, S.; Reffert, S.; Sadegi, S.; Schweitzer,
A.; Seifert, W.; Stahl, O.; Udry, S.
Bibcode: 2018yCat..36180115K
Altcode:
We analyzed radial velocity data from the CARMENES VIS channel,
HIRES/Keck, and HARPS. All the RVs are corrected for barycentric
motion and secular acceleration. The CARMENES measurements were
taken in the context of the CARMENES search for exoplanets around
M dwarfs. The CARMENES instrument consists of two channels: the VIS
channel obtains spectra at a resolution of R=94600 in the wavelength
range 520-960nm, while the NIR channel yields spectra of R=80400
covering 960-1710nm. Both channels are calibrated in wavelength with
hollow-cathode lamps and use temperature- and pressure-stabilized
Fabry-Perot etalons to interpolate the wavelength solution and
simultaneously monitor the spectrograph drift during nightly operations
(Bauer et al., 2015A&A...581A.117B). (1 data file).
Title: Chromospheric activity catalogue of 4454 cool
stars. Questioning the active branch of stellar activity cycles
Authors: Boro Saikia, S.; Marvin, C. J.; Jeffers, S. V.; Reiners,
A.; Cameron, R.; Marsden, S. C.; Petit, P.; Warnecke, J.; Yadav, A. P.
Bibcode: 2018A&A...616A.108B
Altcode: 2018A&A...616A.108S; 2018arXiv180311123B
Context. Chromospheric activity monitoring of a wide range of cool
stars can provide valuable information on stellar magnetic activity
and its dependence on fundamental stellar parameters such as effective
temperature and rotation.
Aims: We compile a chromospheric
activity catalogue of 4454 cool stars from a combination of archival
HARPS spectra and multiple other surveys, including the Mount Wilson
data that have recently been released by the NSO. We explore the
variation in chromospheric activity of cool stars along the main
sequence for stars with different effective temperatures. Additionally,
we also perform an activity-cycle period search and investigate its
relation with rotation.
Methods: The chromospheric activity
index, S-index, was measured for 304 main-sequence stars from
archived high-resolution HARPS spectra. Additionally, the measured
and archived S-indices were converted into the chromospheric flux
ratio log RHK'. The activity-cycle periods were
determined using the generalised Lomb-Scargle periodogram to study
the active and inactive branches on the rotation - activity-cycle
period plane.
Results: The global sample shows that the
bimodality of chromospheric activity, known as the Vaughan-Preston
gap, is not prominent, with a significant percentage of the stars at
an intermediate-activity level around R'HK =
-4.75. Independently, the cycle period search shows that stars can lie
in the region intermediate between the active and inactive branch, which
means that the active branch is not as clearly distinct as previously
thought.
Conclusions: The weakening of the Vaughan-Preston
gap indicates that cool stars spin down from a higher activity
level and settle at a lower activity level without a sudden break
at intermediate activity. Some cycle periods are close to the solar
value between the active and inactive branch, which suggests that the
solar dynamo is most likely a common case of the stellar dynamo. Full Table A.1 is 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/616/A108
Title: VizieR Online Data Catalog: Cool stars chromospheric activity
catalog (Boro Saikia+, 2018)
Authors: Boro Saikia, S.; Marvin, C. J.; Jeffers, S. V.; Reiners,
A.; Cameron, R.; Marsden, S. C.; Petit, P.; Warnecke, J.; Yadav, A. P.
Bibcode: 2018yCat..36160108B
Altcode:
We tabulate chromospheric activity of cool stars determined from
CaII H and K lines. The catalogue is created by combining archival
HARPS spectra (Lovis et al. 2011, Cat. J/A+A/528/112, Bonfils et
al. 2013A&A...549A.109B) and multiple other surveys (Baliunas
et al. 1995ApJ...438..269B, Duncan et al. 1991ApJS...76..383D,
Cat. III/159, Arriagada et al. 2012, Cat. J/ApJS/200/15, Henry et
al. 1996, Cat. J/AJ/111/439, Gray et al. 2006, Cat. J/AJ/132/161, Hall
et al. 2009, Cat. J/AJ/138/312, Wright et al. 2004, Cat. J/ApJS/152/261,
Issacson & Fischer 2010, Cat. J/ApJ/725/875). The stellar properties
are taken from HIPPARCOS (Cat. I/239). (1 data file).
Title: The Solar Wind in Time II: can we detect radio emission from
young solar analogues?
Authors: Ó Fionnagáin, Dúalta; Vidotto, Aline; Petit, Pascal;
Folsom, Colin; Jeffers, Sandra; Marsden, Stephen; Morin, Julien;
do Nascimento, José-Dias, Jr.
Bibcode: 2018csss.confE..70O
Altcode:
The solar wind in the preset is well studied using remote and in
situ measurements. Not much is known about the evolution of the solar
wind over the lifetime of our star, posing the question, what was the
solar wind like over evolutionary timescales? To answer this question
we turn to solar-like stars that we can use as proxies for the solar
wind at different ages. There currently exists little information on
the winds of solar-like stars as observations are difficult to conduct
due to their rarefied nature which leads to diminished emissions. We
present 3D MHD simulations of a sample of solar analogues from which we
determine global wind parameters such as mass- and angular momentum-loss
rates. From our simulations we calculated the thermal bremsstrahlung
expected from these winds using a developed numerical tool, comparing
them to the sensitivities of current and future radio telescopes.
Github
Zenodo
Title: CARMENES: high-resolution spectra and precise radial velocities
in the red and infrared
Authors: Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners, A.;
Caballero, J. A.; Seifert, W.; Aceituno, J.; Azzaro, M.; Baroch, D.;
Barrado, D.; Bauer, F.; Becerril, S.; Bèjar, V. J. S.; Benítez,
D.; Brinkmöller, M.; Cardona Guillén, C.; Cifuentes, C.; Colomé,
J.; Cortés-Contreras, M.; Czesla, S.; Dreizler, S.; Frölich, K.;
Fuhrmeister, B.; Galadí-Enríquez, D.; González Hernández, J. I.;
González Peinado, R.; Guenther, E. W.; de Guindos, E.; Hagen, H. -J.;
Hatzes, A. P.; Hauschildt, P. H.; Helmling, J.; Henning, Th.; Herbort,
O.; Hernández Castaño, L.; Herrero, E.; Hintz, D.; Jeffers, S. V.;
Johnson, E. N.; de Juan, E.; Kaminski, A.; Klahr, H.; Kürster,
M.; Lafarga, M.; Sairam, L.; Lampón, M.; Lara, L. M.; Launhardt,
R.; López del Fresno, M.; López-Puertas, M.; Luque, R.; Mandel,
H.; Marfil, E. G.; Martín, E. L.; Martín-Ruiz, S.; Mathar, R. J.;
Montes, D.; Morales, J. C.; Nagel, E.; Nortmann, L.; Nowak, G.; Pallé,
E.; Passegger, V. -M.; Pavlov, A.; Pedraz, S.; Pérez-Medialdea, D.;
Perger, M.; Rebolo, R.; Reffert, S.; Rodríguez, E.; Rodríguez López,
C.; Rosich, A.; Sabotta, S.; Sadegi, S.; Salz, M.; Sánchez-López,
A.; Sanz-Forcada, J.; Sarkis, P.; Schäfer, S.; Schiller, J.; Schmitt,
J. H. M. M.; Schöfer, P.; Schweitzer, A.; Shulyak, D.; Solano, E.;
Stahl, O.; Tala Pinto, M.; Trifonov, T.; Zapatero Osorio, M. R.; Yan,
F.; Zechmeister, M.; Abellán, F. J.; Abril, M.; Alonso-Floriano,
F. J.; Ammler-von Eiff, M.; Anglada-Escudé, G.; Anwand-Heerwart, H.;
Arroyo-Torres, B.; Berdiñas, Z. M.; Bergondy, G.; Blümcke, M.; del
Burgo, C.; Cano, J.; Carro, J.; Cárdenas, M. C.; Casal, E.; Claret,
A.; Díez-Alonso, E.; Doellinger, M.; Dorda, R.; Feiz, C.; Fernández,
M.; Ferro, I. M.; Gaisné, G.; Gallardo, I.; Gálvez-Ortiz, M. C.;
García-Piquer, A.; García-Vargas, M. L.; Garrido, R.; Gesa, L.;
Gómez Galera, V.; González-Álvarez, E.; González-Cuesta, L.;
Grohnert, S.; Grözinger, U.; Guàrdia, J.; Guijarro, A.; Hedrosa,
R. P.; Hermann, D.; Hermelo, I.; Hernández Arabí, R.; Hernández
Hernando, F.; Hidalgo, D.; Holgado, G.; Huber, A.; Huber, K.; Huke,
P.; Kehr, M.; Kim, M.; Klein, R.; Klüter, J.; Klutsch, A.; Labarga,
F.; Labiche, N.; Lamert, A.; Laun, W.; Lázaro, F. J.; Lemke, U.;
Lenzen, R.; Llamas, M.; Lizon, J. -L.; Lodieu, N.; López González,
M. J.; López-Morales, M.; López Salas, J. F.; López-Santiago,
J.; Magán Madinabeitia, H.; Mall, U.; Mancini, L.; Marín Molina,
J. A.; Martínez-Rodríguez, H.; Maroto Fernández, D.; Marvin, C. J.;
Mirabet, E.; Moreno-Raya, M. E.; Moya, A.; Mundt, R.; Naranjo, V.;
Panduro, J.; Pascual, J.; Pérez-Calpena, A.; Perryman, M. A. C.;
Pluto, M.; Ramón, A.; Redondo, P.; Reinhart, S.; Rhode, P.; Rix,
H. -W.; Rodler, F.; Rohloff, R. -R.; Sánchez-Blanco, E.; Sánchez
Carrasco, M. A.; Sarmiento, L. F.; Schmidt, C.; Storz, C.; Strachan,
J. B. P.; Stürmer, J.; Suárez, J. C.; Tabernero, H. M.; Tal-Or, L.;
Tulloch, S. M.; Ulbrich, R. -G.; Veredas, G.; Vico Linares, J. L.;
Vidal-Dasilva, M.; Vilardell, F.; Wagner, K.; Winkler, J.; Wolthoff,
V.; Xu, W.; Zhao, Z.
Bibcode: 2018SPIE10702E..0WQ
Altcode:
The design and construction of CARMENES has been presented at previous
SPIE conferences. It is a next-generation radial-velocity instrument at
the 3.5m telescope of the Calar Alto Observatory, which was built by a
consortium of eleven Spanish and German institutions. CARMENES consists
of two separate échelle spectrographs covering the wavelength range
from 0.52 to 1.71μm at a spec-tral resolution of R < 80,000, fed by
fibers from the Cassegrain focus of the telescope. CARMENES saw "First
Light" on Nov 9, 2015. During the commissioning and initial operation
phases, we established basic performance data such as throughput and
spectral resolution. We found that our hollow-cathode lamps are suitable
for precise wavelength calibration, but their spectra contain a number
of lines of neon or argon that are so bright that the lamps cannot be
used in simultaneous exposures with stars. We have therefore adopted
a calibration procedure that uses simultaneous star / Fabry Pérot
etalon exposures in combination with a cross-calibration between the
etalons and hollow-cathode lamps during daytime. With this strategy
it has been possible to achieve 1-2 m/s precision in the visible and
5-10 m/s precision in the near-IR; further improvements are expected
from ongoing work on temperature control, calibration procedures
and data reduction. Comparing the RV precision achieved in different
wavelength bands, we find a "sweet spot" between 0.7 and 0.8μm, where
deep TiO bands provide rich RV information in mid-M dwarfs. This is
in contrast to our pre-survey models, which predicted comparatively
better performance in the near-IR around 1μm, and explains in
part why our near-IR RVs do not reach the same precision level as
those taken with the visible spectrograph. We are now conducting a
large survey of 340 nearby M dwarfs (with an average distance of only
12pc), with the goal of finding terrestrial planets in their habitable
zones. We have detected the signatures of several previously known or
suspected planets and also discovered several new planets. We find
that the radial velocity periodograms of many M dwarfs show several
significant peaks. The development of robust methods to distinguish
planet signatures from activity-induced radial velocity jitter is
therefore among our priorities. Due to its large wavelength coverage,
the CARMENES survey is generating a unique data set for studies of M
star atmospheres, rotation, and activity. The spectra cover important
diagnostic lines for activity (H alpha, Na I D1 and D2, and the Ca II
infrared triplet), as well as FeH lines, from which the magnetic field
can be inferred. Correlating the time series of these features with
each other, and with wavelength-dependent radial velocities, provides
excellent handles for the discrimination between planetary companions
and stellar radial velocity jitter. These data are also generating
new insight into the physical properties of M dwarf atmospheres, and
the impact of activity and flares on the habitability of M star planets.
Title: The CARMENES search for exoplanets around M dwarfs. Wing
asymmetries of Hα, Na I D, and He I lines
Authors: Fuhrmeister, B.; Czesla, S.; Schmitt, J. H. M. M.; Jeffers,
S. V.; Caballero, J. A.; Zechmeister, M.; Reiners, A.; Ribas, I.;
Amado, P. J.; Quirrenbach, A.; Béjar, V. J. S.; Galadí-Enríquez,
D.; Guenther, E. W.; Kürster, M.; Montes, D.; Seifert, W.
Bibcode: 2018A&A...615A..14F
Altcode: 2018arXiv180110372F
Stellar activity is ubiquitously encountered in M dwarfs and often
characterised by the Hα line. In the most active M dwarfs, Hα is found
in emission, sometimes with a complex line profile. Previous studies
have reported extended wings and asymmetries in the Hα line during
flares. We used a total of 473 high-resolution spectra of 28 active
M dwarfs obtained by the CARMENES (Calar Alto high-Resolution search
for M dwarfs with Exo-Earths with Near-infrared and optical Echelle
Spectrographs) spectrograph to study the occurrence of broadened
and asymmetric Hα line profiles and their association with flares,
and examine possible physical explanations. We detected a total of
41 flares and 67 broad, potentially asymmetric, wings in Hα. The
broadened Hα lines display a variety of profiles with symmetric
cases and both red and blue asymmetries. Although some of these
line profiles are found during flares, the majority are at least not
obviously associated with flaring. We propose a mechanism similar to
coronal rain or chromospheric downward condensations as a cause for
the observed red asymmetries; the symmetric cases may also be caused by
Stark broadening. We suggest that blue asymmetries are associated with
rising material, and our results are consistent with a prevalence of
blue asymmetries during the flare onset. Besides the Hα asymmetries,
we find some cases of additional line asymmetries in He I D3,
Na I D lines, and the He I line at 10 830 Å taken all simultaneously
thanks to the large wavelength coverage of CARMENES. Our study shows
that asymmetric Hα lines are a rather common phenomenon in M dwarfs
and need to be studied in more detail to obtain a better understanding
of the atmospheric dynamics in these objects.
Title: The CARMENES search for exoplanets around M
dwarfs. Photospheric parameters of target stars from high-resolution
spectroscopy
Authors: Passegger, V. M.; Reiners, A.; Jeffers, S. V.; Wende-von Berg,
S.; Schöfer, P.; Caballero, J. A.; Schweitzer, A.; Amado, P. J.;
Béjar, V. J. S.; Cortés-Contreras, M.; Hatzes, A. P.; Kürster,
M.; Montes, D.; Pedraz, S.; Quirrenbach, A.; Ribas, I.; Seifert, W.
Bibcode: 2018A&A...615A...6P
Altcode: 2018arXiv180202946P
Context. The new CARMENES instrument comprises two high-resolution
and high-stability spectrographs that are used to search for habitable
planets around M dwarfs in the visible and near-infrared regime via the
Doppler technique.
Aims: Characterising our target sample is
important for constraining the physical properties of any planetary
systems that are detected. The aim of this paper is to determine
the fundamental stellar parameters of the CARMENES M-dwarf target
sample from high-resolution spectra observed with CARMENES. We also
include several M-dwarf spectra observed with other high-resolution
spectrographs, that is CAFE, FEROS, and HRS, for completeness.
Methods: We used a χ2 method to derive the stellar
parameters effective temperature Teff, surface gravity logg,
and metallicity [Fe/H] of the target stars by fitting the most recent
version of the PHOENIX-ACES models to high-resolution spectroscopic
data. These stellar atmosphere models incorporate a new equation
of state to describe spectral features of low-temperature stellar
atmospheres. Since Teff, logg, and [Fe/H] show degeneracies,
the surface gravity is determined independently using stellar
evolutionary models.
Results: We derive the stellar parameters
for a total of 300 stars. The fits achieve very good agreement between
the PHOENIX models and observed spectra. We estimate that our method
provides parameters with uncertainties of σTeff = 51 K,
σlog g = 0.07, and σ[Fe/H] = 0.16, and show
that atmosphere models for low-mass stars have significantly improved
in the last years. Our work also provides an independent test of
the new PHOENIX-ACES models, and a comparison for other methods using
low-resolution spectra. In particular, our effective temperatures agree
well with literature values, while metallicities determined with our
method exhibit a larger spread when compared to literature results. Full Table A.1 is 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/615/A6
Title: VizieR Online Data Catalog: 324 CARMENES M dwarfs velocities
(Reiners+, 2018)
Authors: Reiners, A.; Zechmeister, M.; Caballero, J. A.; Ribas, I.;
Morales, J. C.; Jeffers, S. V.; Schofer, P.; Tal-Or, L.; Quirrenbach,
A.; Amado, P. J.; Kaminski, A.; Seifert, W.; Abril, M.; Aceituno,
J.; Alonso-Floriano, F. J.; Ammler-von Eiff, M.; Antona, R.;
Anglada-Escude, G.; Anwand-Heerwart, H.; Arroyo-Torres, B.; Azzaro,
M.; Baroch, D.; Barrado, D.; Bauer, F. F.; Becerril, S.; Bejar,
V. J. S.; Benitez, D.; Berdinas, Z. M.; Bergond, G.; Blumcke, M.;
Brinkmoller, M.; Del Burgo, C.; Cano, J.; Cardenas Vazquez, M. C.;
Casal, E.; Cifuentes, C.; Claret, A.; Colome, J.; Cortes-Contreras,
M.; Czesla, S.; Diez-Alonso, E.; Dreizler, S.; Feiz, C.; Fernandez, M.;
Ferro, I. M.; Fuhrmeister, B.; Galadi-Enriquez, D.; Garcia-Piquer, A.;
Garcia Vargas, M. L.; Gesa, L.; Gomez Galera, V.; Gonzalez Hernandez,
J. I.; Gonzalez-Peinado, R.; Grozinger, U.; Grohnert, S.; Guardia,
J.; Guenther, E. W.; Guijarro, A.; de Guindos, E.; Gutierrez-Soto,
J.; Hagen, H. -J.; Hatzes, A. P.; Hauschildt, P. H.; Hedrosa,
R. P.; Helmling, J.; Henning, T.; Hermelo, I.; Hernandez Arabi, R.;
Hernandez Castano, L.; Hernandez Hernando, F.; Herrero, E.; Huber, A.;
Huke, P.; Johnson, E. N.; de Juan, E.; Kim, M.; Klein, R.; Kluter,
J.; Klutsch, A.; Kurster, M.; Lafarga, M.; Lamert, A.; Lampon, M.;
Lara, L. M.; Laun, W.; Lemke, U.; Lenzen, R.; Launhardt, R.; Lopez
Del Fresno, M.; Lopez-Gonzalez, J.; Lopez-Puertas, M.; Lopez Salas,
J. F.; Lopez-Santiago, J.; Luque, R.; Magan Madinabeitia, H.; Mall,
U.; Mancini, L.; Mandel, H.; Marfil, E.; Marin Molina, J. A.; Maroto
Fernandez, D.; Martin, E. L.; Martin-Ruiz, S.; Marvin, C. J.; Mathar,
R. J.; Mirabet, E.; Montes, D.; Moreno-Raya, M. E.; Moya, A.; Mundt,
R.; Nagel, E.; Naranjo, V.; Nortmann, L.; Nowak, G.; Ofir, A.; Oreiro,
R.; Palle, E.; Panduro, J.; Pascual, J.; Passegger, V. M.; Pavlov,
A.; Pedraz, S.; Perez-Calpena, A.; Perez Medialdea, D.; Perger,
M.; Perryman, M. A. C.; Pluto, M.; Rabaza, O.; Ramon, A.; Rebolo,
R.; Redondo, P.; Reffert, S.; Reinhart, S.; Rhode, P.; Rix, H. -W.;
Rodler, F.; Rodriguez, E.; Rodriguez-Lopez, C.; Rodriguez Trinidad,
A.; Rohloff, R. -R.; Rosich, A.; Sadegi, S.; Sanchez-Blanco, E.;
Sanchez Carrasco, M. A.; Sanchez-Lopez, A.; Sanz-Forcada, J.; Sarkis,
P.; Sarmiento, L. F.; Schafer, S.; Schmitt, J. H. M. M.; Schiller, J.;
Schweitzer, A.; Solano, E.; Stahl, O.; Strachan, J. B. P.; Sturmer,
J.; Suarez, J. C.; Tabernero, H. M.; Tala, M.; Trifonov, T.; Tulloch,
S. M.; Ulbrich, R. G.; Veredas, G.; Vico Linares, J. I.; Vilardell,
F.; Wagner, K.; Winkler, J.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero
Osorio, M. R.
Bibcode: 2018yCat..36120049R
Altcode:
As part of the GTO agreement, we provide early access to one CARMENES
spectrum for each of our sample targets (Table B.1). They can be
downloaded from the CARMENES GTO Data Archive (Caballero et al., 2016,
in Observatory Operations: Strategies, Processes, and Systems VI,
Proc. SPIE, 9910, 99100E) (http://carmenes.cab.inta-csic.es) (1
data file).
Title: CARMENES input catalogue of M dwarfs. III. Rotation and
activity from high-resolution spectroscopic observations
Authors: Jeffers, S. V.; Schöfer, P.; Lamert, A.; Reiners, A.;
Montes, D.; Caballero, J. A.; Cortés-Contreras, M.; Marvin, C. J.;
Passegger, V. M.; Zechmeister, M.; Quirrenbach, A.; Alonso-Floriano,
F. J.; Amado, P. J.; Bauer, F. F.; Casal, E.; Diez Alonso, E.; Herrero,
E.; Morales, J. C.; Mundt, R.; Ribas, I.; Sarmiento, L. F.
Bibcode: 2018A&A...614A..76J
Altcode: 2018arXiv180202102J
CARMENES is a spectrograph for radial velocity surveys of M
dwarfs with the aim of detecting Earth-mass planets orbiting in the
habitable zones of their host stars. To ensure an optimal use of the
CARMENES guaranteed time observations, in this paper we investigate
the correlation of activity and rotation for approximately 2200 M
dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present
new high-resolution spectroscopic observations with FEROS, CAFE,
and HRS of approximately 500 M dwarfs. For each new observation, we
determined its radial velocity and measured its Hα activity index and
its rotation velocity. Additionally, we have multiple observations of
many stars to investigate if there are any radial velocity variations
due to multiplicity. The results of our survey confirm that early-M
dwarfs are Hα inactive with low rotational velocities and that
late-M dwarfs are Hα active with very high rotational velocities. The
results of this high-resolution analysis comprise the most extensive
catalogue of rotation and activity in M dwarfs currently available. Based on observations made at the Calar Alto Observatory, Spain, the
European Southern Observatory, La Silla, Chile and McDonald Observatory,
USA.Tables A.1-A.3 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/614/A76
Title: VizieR Online Data Catalog: Photospheric parameters of CARMENES
stars (Passegger+, 2018)
Authors: Passegger, V. M.; Reiners, A.; Jeffers, S. V.; Wende-von Berg,
S.; Schaefer, P.; Caballero, J. A.; Schweitzer, A.; Amado, P. J.;
Bejar, V. J. S.; Cortes-Contreras, M.; Hatzes, A. P.; Kuerster, M.;
Montes, D.; Pedraz, S.; Quirrenbach, A.; Ribas, I.; Seifert, W.
Bibcode: 2018yCat..36150006P
Altcode:
We present basic astronomical parameters of 300 M dwarfs within
the CARMENES survey. For each star, we provide Carmencita identifier
(Karmn), Simbad name, equatorial coordinates, spectral type, effective
temperature, surface gravity, metallicity, rotational velocity, stellar
mass, CaII emission flag and instrument with which the spectrum was
obtained. (2 data files).
Title: The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass
Planet in the Temperate Zone of the Nearby K2-18
Authors: Sarkis, Paula; Henning, Thomas; Kürster, Martin; Trifonov,
Trifon; Zechmeister, Mathias; Tal-Or, Lev; Anglada-Escudé, Guillem;
Hatzes, Artie P.; Lafarga, Marina; Dreizler, Stefan; Ribas, Ignasi;
Caballero, José A.; Reiners, Ansgar; Mallonn, Matthias; Morales,
Juan C.; Kaminski, Adrian; Aceituno, Jesús; Amado, Pedro J.; Béjar,
Victor J. S.; Hagen, Hans-Jürgen; Jeffers, Sandra; Quirrenbach,
Andreas; Launhardt, Ralf; Marvin, Christopher; Montes, David
Bibcode: 2018AJ....155..257S
Altcode: 2018arXiv180500830S; 2018arXiv180500830P
K2-18 is a nearby M2.5 dwarf, located at 34 pc and hosting a transiting
planet that was first discovered by the K2 mission and later confirmed
with Spitzer Space Telescope observations. With a radius of ∼2 R
⊕ and an orbital period of ∼33 days, the planet lies in
the temperate zone of its host star and receives stellar irradiation
similar to that of Earth. Here we perform radial velocity follow-up
observations with the visual channel of CARMENES with the goal of
determining the mass and density of the planet. We measure a planetary
semi-amplitude of K b ∼ 3.5 {{m}} {{{s}}}-1
and a mass of M b ∼ 9 M ⊕, yielding a bulk
density around {ρ }b∼ 4 {{g}} {cm}}-3. This
indicates a low-mass planet with a composition consistent with a solid
core and a volatile-rich envelope. A signal at 9 days was recently
reported using radial velocity measurements taken with the HARPS
spectrograph. This was interpreted as being due to a second planet. We
see a weaker, time- and wavelength-dependent signal in the CARMENES
data set and thus favor stellar activity for its origin. K2-18 b joins
the growing group of low-mass planets detected in the temperate zone
of M dwarfs. The brightness of the host star in the near-infrared
makes the system a good target for detailed atmospheric studies with
the James Webb Space Telescope.
Title: The CARMENES search for exoplanets around M
dwarfs. Radial-velocity variations of active stars in visual-channel
spectra
Authors: Tal-Or, L.; Zechmeister, M.; Reiners, A.; Jeffers, S. V.;
Schöfer, P.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Caballero,
J. A.; Aceituno, J.; Bauer, F. F.; Béjar, V. J. S.; Czesla,
S.; Dreizler, S.; Fuhrmeister, B.; Hatzes, A. P.; Johnson, E. N.;
Kürster, M.; Lafarga, M.; Montes, D.; Morales, J. C.; Reffert, S.;
Sadegi, S.; Seifert, W.; Shulyak, D.
Bibcode: 2018A&A...614A.122T
Altcode: 2018arXiv180302338T
Context. Previous simulations predicted the activity-induced
radial-velocity (RV) variations of M dwarfs to range from 1 cm
s-1 to 1 km s-1, depending on various stellar
and activity parameters.
Aims: We investigate the observed
relations between RVs, stellar activity, and stellar parameters of M
dwarfs by analyzing CARMENES high-resolution visual-channel spectra
(0.5-1μm), which were taken within the CARMENES RV planet survey
during its first 20 months of operation.
Methods: During this
time, 287 of the CARMENES-sample stars were observed at least five
times. From each spectrum we derived a relative RV and a measure of
chromospheric Hα emission. In addition, we estimated the chromatic
index (CRX) of each spectrum, which is a measure of the RV wavelength
dependence.
Results: Despite having a median number of only
11 measurements per star, we show that the RV variations of the
stars with RV scatter of >10 m s-1 and a projected
rotation velocity v sin i > 2 km s-1 are caused mainly
by activity. We name these stars "active RV-loud stars" and find their
occurrence to increase with spectral type: from 3% for early-type M
dwarfs (M0.0-2.5 V) through 30% for mid-type M dwarfs (M3.0-5.5 V)
to >50% for late-type M dwarfs (M6.0-9.0 V). Their RV-scatter
amplitude is found to be correlated mainly with v sin i. For about
half of the stars, we also find a linear RV-CRX anticorrelation, which
indicates that their activity-induced RV scatter is lower at longer
wavelengths. For most of them we can exclude a linear correlation
between RV and Hα emission.
Conclusions: Our results are
in agreement with simulated activity-induced RV variations in M
dwarfs. The RV variations of most active RV-loud M dwarfs are likely
to be caused by dark spots on their surfaces, which move in and out of
view as the stars rotate. The data presented in Figs. 5 and A.1
are only available in electronic form 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/614/A122
Title: The CARMENES search for exoplanets around M
dwarfs. High-resolution optical and near-infrared spectroscopy of
324 survey stars
Authors: Reiners, A.; Zechmeister, M.; Caballero, J. A.; Ribas,
I.; Morales, J. C.; Jeffers, S. V.; Schöfer, P.; Tal-Or, L.;
Quirrenbach, A.; Amado, P. J.; Kaminski, A.; Seifert, W.; Abril, M.;
Aceituno, J.; Alonso-Floriano, F. J.; Ammler-von Eiff, M.; Antona,
R.; Anglada-Escudé, G.; Anwand-Heerwart, H.; Arroyo-Torres, B.;
Azzaro, M.; Baroch, D.; Barrado, D.; Bauer, F. F.; Becerril,
S.; Béjar, V. J. S.; Benítez, D.; Berdinas, Z. M.; Bergond,
G.; Blümcke, M.; Brinkmöller, M.; del Burgo, C.; Cano, J.;
Cárdenas Vázquez, M. C.; Casal, E.; Cifuentes, C.; Claret, A.;
Colomé, J.; Cortés-Contreras, M.; Czesla, S.; Díez-Alonso, E.;
Dreizler, S.; Feiz, C.; Fernández, M.; Ferro, I. M.; Fuhrmeister, B.;
Galadí-Enríquez, D.; Garcia-Piquer, A.; García Vargas, M. L.; Gesa,
L.; Gómez Galera, V.; González Hernández, J. I.; González-Peinado,
R.; Grözinger, U.; Grohnert, S.; Guàrdia, J.; Guenther, E. W.;
Guijarro, A.; de Guindos, E.; Gutiérrez-Soto, J.; Hagen, H. -J.;
Hatzes, A. P.; Hauschildt, P. H.; Hedrosa, R. P.; Helmling, J.;
Henning, Th.; Hermelo, I.; Hernández Arabí, R.; Hernández Castaño,
L.; Hernández Hernando, F.; Herrero, E.; Huber, A.; Huke, P.; Johnson,
E. N.; de Juan, E.; Kim, M.; Klein, R.; Klüter, J.; Klutsch, A.;
Kürster, M.; Lafarga, M.; Lamert, A.; Lampón, M.; Lara, L. M.;
Laun, W.; Lemke, U.; Lenzen, R.; Launhardt, R.; López del Fresno,
M.; López-González, J.; López-Puertas, M.; López Salas, J. F.;
López-Santiago, J.; Luque, R.; Magán Madinabeitia, H.; Mall, U.;
Mancini, L.; Mandel, H.; Marfil, E.; Marín Molina, J. A.; Maroto
Fernández, D.; Martín, E. L.; Martín-Ruiz, S.; Marvin, C. J.;
Mathar, R. J.; Mirabet, E.; Montes, D.; Moreno-Raya, M. E.; Moya, A.;
Mundt, R.; Nagel, E.; Naranjo, V.; Nortmann, L.; Nowak, G.; Ofir,
A.; Oreiro, R.; Pallé, E.; Panduro, J.; Pascual, J.; Passegger,
V. M.; Pavlov, A.; Pedraz, S.; Pérez-Calpena, A.; Pérez Medialdea,
D.; Perger, M.; Perryman, M. A. C.; Pluto, M.; Rabaza, O.; Ramón,
A.; Rebolo, R.; Redondo, P.; Reffert, S.; Reinhart, S.; Rhode, P.;
Rix, H. -W.; Rodler, F.; Rodríguez, E.; Rodríguez-López, C.;
Rodríguez Trinidad, A.; Rohloff, R. -R.; Rosich, A.; Sadegi, S.;
Sánchez-Blanco, E.; Sánchez Carrasco, M. A.; Sánchez-López, A.;
Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer, S.; Schmitt,
J. H. M. M.; Schiller, J.; Schweitzer, A.; Solano, E.; Stahl, O.;
Strachan, J. B. P.; Stürmer, J.; Suárez, J. C.; Tabernero, H. M.;
Tala, M.; Trifonov, T.; Tulloch, S. M.; Ulbrich, R. G.; Veredas, G.;
Vico Linares, J. I.; Vilardell, F.; Wagner, K.; Winkler, J.; Wolthoff,
V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2018A&A...612A..49R
Altcode: 2017arXiv171106576R
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to
search for any orbiting planets. In this paper, we present the survey
sample by publishing one CARMENES spectrum for each M dwarf. These
spectra cover the wavelength range 520-1710 nm at a resolution of
at least R >80 000, and we measure its RV, Hα emission, and
projected rotation velocity. We present an atlas of high-resolution
M-dwarf spectra and compare the spectra to atmospheric models. To
quantify the RV precision that can be achieved in low-mass stars over
the CARMENES wavelength range, we analyze our empirical information
on the RV precision from more than 6500 observations. We compare our
high-resolution M-dwarf spectra to atmospheric models where we determine
the spectroscopic RV information content, Q, and signal-to-noise
ratio. We find that for all M-type dwarfs, the highest RV precision can
be reached in the wavelength range 700-900 nm. Observations at longer
wavelengths are equally precise only at the very latest spectral types
(M8 and M9). We demonstrate that in this spectroscopic range, the large
amount of absorption features compensates for the intrinsic faintness
of an M7 star. To reach an RV precision of 1 m s-1 in very
low mass M dwarfs at longer wavelengths likely requires the use of a 10
m class telescope. For spectral types M6 and earlier, the combination
of a red visual and a near-infrared spectrograph is ideal to search
for low-mass planets and to distinguish between planets and stellar
variability. At a 4 m class telescope, an instrument like CARMENES has
the potential to push the RV precision well below the typical jitter
level of 3-4 m s-1.
Title: VizieR Online Data Catalog: Radial-velocity of CARMENES M
dwarfs (Tal-Or+, 2018)
Authors: Tal-Or, L.; Zechmeister, M.; Reiners, A.; Jeffers, S. V.;
Schoefer, P.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Caballero,
J. A.; Aceituno, J.; Bauer, F. F.; Bejar, V. J. S.; Czesla, S.;
Dreizler, S.; Fuhrmeister, B.; Hatzes, A. P.; Johnson, E. N.; Kurster,
M.; Lafarga, M.; Montes, D.; Morales, J. C.; Reffert, S.; Sadegi,
S.; Seifert, W.; Shulyak, D.
Bibcode: 2018yCat..36140122T
Altcode:
The catalogue contains the data presented in Figures 5 and A.1 of the
source paper. (2 data files).
Title: The CARMENES search for exoplanets around M dwarfs . First
visual-channel radial-velocity measurements and orbital parameter
updates of seven M-dwarf planetary systems
Authors: Trifonov, T.; Kürster, M.; Zechmeister, M.; Tal-Or,
L.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Ribas, I.;
Reiners, A.; Reffert, S.; Dreizler, S.; Hatzes, A. P.; Kaminski, A.;
Launhardt, R.; Henning, Th.; Montes, D.; Béjar, V. J. S.; Mundt,
R.; Pavlov, A.; Schmitt, J. H. M. M.; Seifert, W.; Morales, J. C.;
Nowak, G.; Jeffers, S. V.; Rodríguez-López, C.; del Burgo, C.;
Anglada-Escudé, G.; López-Santiago, J.; Mathar, R. J.; Ammler-von
Eiff, M.; Guenther, E. W.; Barrado, D.; González Hernández, J. I.;
Mancini, L.; Stürmer, J.; Abril, M.; Aceituno, J.; Alonso-Floriano,
F. J.; Antona, R.; Anwand-Heerwart, H.; Arroyo-Torres, B.; Azzaro,
M.; Baroch, D.; Bauer, F. F.; Becerril, S.; Benítez, D.; Berdiñas,
Z. M.; Bergond, G.; Blümcke, M.; Brinkmöller, M.; Cano, J.; Cárdenas
Vázquez, M. C.; Casal, E.; Cifuentes, C.; Claret, A.; Colomé,
J.; Cortés-Contreras, M.; Czesla, S.; Díez-Alonso, E.; Feiz, C.;
Fernández, M.; Ferro, I. M.; Fuhrmeister, B.; Galadí-Enríquez, D.;
Garcia-Piquer, A.; García Vargas, M. L.; Gesa, L.; Gómez Galera,
V.; González-Peinado, R.; Grözinger, U.; Grohnert, S.; Guàrdia,
J.; Guijarro, A.; de Guindos, E.; Gutiérrez-Soto, J.; Hagen,
H. -J.; Hauschildt, P. H.; Hedrosa, R. P.; Helmling, J.; Hermelo, I.;
Hernández Arabí, R.; Hernández Castaño, L.; Hernández Hernando,
F.; Herrero, E.; Huber, A.; Huke, P.; Johnson, E.; de Juan, E.; Kim,
M.; Klein, R.; Klüter, J.; Klutsch, A.; Lafarga, M.; Lampón, M.;
Lara, L. M.; Laun, W.; Lemke, U.; Lenzen, R.; López del Fresno, M.;
López-González, M. J.; López-Puertas, M.; López Salas, J. F.;
Luque, R.; Magán Madinabeitia, H.; Mall, U.; Mandel, H.; Marfil,
E.; Marín Molina, J. A.; Maroto Fernández, D.; Martín, E. L.;
Martín-Ruiz, S.; Marvin, C. J.; Mirabet, E.; Moya, A.; Moreno-Raya,
M. E.; Nagel, E.; Naranjo, V.; Nortmann, L.; Ofir, A.; Oreiro, R.;
Pallé, E.; Panduro, J.; Pascual, J.; Passegger, V. M.; Pedraz,
S.; Pérez-Calpena, A.; Pérez Medialdea, D.; Perger, M.; Perryman,
M. A. C.; Pluto, M.; Rabaza, O.; Ramón, A.; Rebolo, R.; Redondo,
P.; Reinhardt, S.; Rhode, P.; Rix, H. -W.; Rodler, F.; Rodríguez,
E.; Rodríguez Trinidad, A.; Rohloff, R. -R.; Rosich, A.; Sadegi, S.;
Sánchez-Blanco, E.; Sánchez Carrasco, M. A.; Sánchez-López, A.;
Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer, S.; Schiller,
J.; Schöfer, P.; Schweitzer, A.; Solano, E.; Stahl, O.; Strachan,
J. B. P.; Suárez, J. C.; Tabernero, H. M.; Tala, M.; Tulloch, S. M.;
Veredas, G.; Vico Linares, J. I.; Vilardell, F.; Wagner, K.; Winkler,
J.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2018A&A...609A.117T
Altcode: 2017arXiv171001595T
Context. The main goal of the CARMENES survey is to find Earth-mass
planets around nearby M-dwarf stars. Seven M dwarfs included in the
CARMENES sample had been observed before with HIRES and HARPS and
either were reported to have one short period planetary companion (GJ
15 A, GJ 176, GJ 436, GJ 536 and GJ 1148) or are multiple planetary
systems (GJ 581 and GJ 876).
Aims: We aim to report new precise
optical radial velocity measurements for these planet hosts and test
the overall capabilities of CARMENES.
Methods: We combined our
CARMENES precise Doppler measurements with those available from HIRES
and HARPS and derived new orbital parameters for the systems. Bona-fide
single planet systems were fitted with a Keplerian model. The multiple
planet systems were analyzed using a self-consistent dynamical model
and their best fit orbits were tested for long-term stability.
Results: We confirm or provide supportive arguments for planets around
all the investigated stars except for GJ 15 A, for which we find that
the post-discovery HIRES data and our CARMENES data do not show a
signal at 11.4 days. Although we cannot confirm the super-Earth planet
GJ 15 Ab, we show evidence for a possible long-period (Pc =
7030-630+970 d) Saturn-mass (mcsini
= 51.8M⊕) planet around GJ 15 A. In addition, based
on our CARMENES and HIRES data we discover a second planet around
GJ 1148, for which we estimate a period Pc = 532.6 days,
eccentricity ec = 0.342 and minimum mass mcsini =
68.1M⊕.
Conclusions: The CARMENES optical radial
velocities have similar precision and overall scatter when compared
to the Doppler measurements conducted with HARPS and HIRES. We
conclude that CARMENES is an instrument that is up to the challenge
of discovering rocky planets around low-mass stars. Based on
observations collected at the European Organisation for Astronomical
Research in the Southern Hemisphere under ESO programmes 072.C-0488,
072.C-0513, 074.C-0012, 074.C-0364, 075.D-0614, 076.C-0878, 077.C-0364,
077.C-0530, 078.C-0044, 078.C-0833, 079.C-0681, 183.C-0437, 60.A-9036,
082.C-0718, 183.C-0972, 085.C-0019, 087.C-0831, 191.C-0873. The
appendix tables 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/609/A117
Title: The influence of convective blueshift on radial velocities
of F, G, and K stars
Authors: Bauer, F. F.; Reiners, A.; Beeck, B.; Jeffers, S. V.
Bibcode: 2018A&A...610A..52B
Altcode:
Context. Apparent radial velocity (RV) signals induced by stellar
surface features such as spots and plages can result in a false planet
detection or hide the presence of an orbiting planet. Our ability
to detect rocky exoplanets is currently limited by our understanding
of such stellar signals.
Aims: We model RV variations caused
by active regions on the stellar surface of typical exoplanet-hosting
stars of spectral type F, G, and K. We aim to understand how the stellar
magnetic field strength, convective blueshift, and spot temperatures
can influence RV signals caused by active regions.
Methods:
We use magneto-hydrodynamic (MHD) simulations for stars with spectral
types F3V, a G2V, and a K5V. We quantify the impact of the magnetic
field strength inside active regions on the RV measurement using the
magnetic and non-magnetic FeI lines at 6165 Å and 6173 Å. We also
quantify the impact of spot temperature and convective blueshift on
the measured RV values.
Results: Increasing the magnetic field
strength increases the efficiency to suppress convection in active
regions which results in an asymmetry between red- and blueshifted
parts of the RV curves. A stronger suppression of convection also
leads to an observed increase in RV amplitude for stronger magnetic
fields. The MHD simulations predict convective motions to be faster
in hotter stars. The suppression of faster convection leads to a
stronger RV amplitude increase in hotter stars when the magnetic
field is increased. While suppression of convection increases the
asymmetry in RV curves,c a decreasing spot temperature counteracts
this effect. When using observed temperatures for dark spots in our
simulations we find that convective blueshift effects are negligible.
Title: The open flux evolution of a solar-mass star on the main
sequence
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Donati, J. -F.; Boro
Saikia, S.; Fares, R.; Folsom, C. P.; Jeffers, S. V.; Marsden, S. C.;
Morin, J.; Petit, P.; BCool Collaboration
Bibcode: 2018MNRAS.474..536S
Altcode: 2017MNRAS.474..536S; 2017arXiv171103904S
Magnetic activity is known to be correlated to the rotation period for
moderately active main-sequence solar-like stars. In turn, the stellar
rotation period evolves as a result of magnetized stellar winds that
carry away angular momentum. Understanding the interplay between
magnetic activity and stellar rotation is therefore a central task
for stellar astrophysics. Angular momentum evolution models typically
employ spin-down torques that are formulated in terms of the surface
magnetic field strength. However, these formulations fail to account
for the magnetic field geometry, unlike those that are expressed in
terms of the open flux, i.e. the magnetic flux along which stellar
winds flow. In this work, we model the angular momentum evolution
of main-sequence solar-mass stars using a torque law formulated in
terms of the open flux. This is done using a potential field source
surface model in conjunction with the Zeeman-Doppler magnetograms of
a sample of roughly solar-mass stars. We explore how the open flux of
these stars varies with stellar rotation and choice of source surface
radii. We also explore the effect of field geometry by using two methods
of determining the open flux. The first method only accounts for the
dipole component while the second accounts for the full set of spherical
harmonics available in the Zeeman-Doppler magnetogram. We find only a
small difference between the two methods, demonstrating that the open
flux, and indeed the spin-down, of main-sequence solar-mass stars is
likely dominated by the dipolar component of the magnetic field.
Title: Spectrum radial velocity analyser (SERVAL). High-precision
radial velocities and two alternative spectral indicators
Authors: Zechmeister, M.; Reiners, A.; Amado, P. J.; Azzaro, M.;
Bauer, F. F.; Béjar, V. J. S.; Caballero, J. A.; Guenther, E. W.;
Hagen, H. -J.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Launhardt,
R.; Montes, D.; Morales, J. C.; Quirrenbach, A.; Reffert, S.; Ribas,
I.; Seifert, W.; Tal-Or, L.; Wolthoff, V.
Bibcode: 2018A&A...609A..12Z
Altcode: 2017arXiv171010114Z; 2017A&A...609A..12Z
Context. The CARMENES survey is a high-precision radial velocity (RV)
programme that aims to detect Earth-like planets orbiting low-mass
stars.
Aims: We develop least-squares fitting algorithms to
derive the RVs and additional spectral diagnostics implemented in the
SpEctrum Radial Velocity AnaLyser (SERVAL), a publicly available python
code.
Methods: We measured the RVs using high signal-to-noise
templates created by coadding all available spectra of each star. We
define the chromatic index as the RV gradient as a function of
wavelength with the RVs measured in the echelle orders. Additionally,
we computed the differential line width by correlating the fit residuals
with the second derivative of the template to track variations in the
stellar line width.
Results: Using HARPS data, our SERVAL code
achieves a RV precision at the level of 1 m/s. Applying the chromatic
index to CARMENES data of the active star YZ CMi, we identify apparent
RV variations induced by stellar activity. The differential line width
is found to be an alternative indicator to the commonly used full
width half maximum.
Conclusions: We find that at the red optical
wavelengths (700-900 nm) obtained by the visual channel of CARMENES,
the chromatic index is an excellent tool to investigate stellar active
regions and to identify and perhaps even correct for activity-induced
RV variations.
Title: The CARMENES search for exoplanets around M dwarfs. HD147379 b:
A nearby Neptune in the temperate zone of an early-M dwarf
Authors: Reiners, A.; Ribas, I.; Zechmeister, M.; Caballero, J. A.;
Trifonov, T.; Dreizler, S.; Morales, J. C.; Tal-Or, L.; Lafarga,
M.; Quirrenbach, A.; Amado, P. J.; Kaminski, A.; Jeffers, S. V.;
Aceituno, J.; Béjar, V. J. S.; Guàrdia, J.; Guenther, E. W.; Hagen,
H. -J.; Montes, D.; Passegger, V. M.; Seifert, W.; Schweitzer, A.;
Cortés-Contreras, M.; Abril, M.; Alonso-Floriano, F. J.; Ammler-von
Eiff, M.; Antona, R.; Anglada-Escudé, G.; Anwand-Heerwart, H.;
Arroyo-Torres, B.; Azzaro, M.; Baroch, D.; Barrado, D.; Bauer,
F. F.; Becerril, S.; Benítez, D.; Berdiñas, Z. M.; Bergond, G.;
Blümcke, M.; Brinkmöller, M.; del Burgo, C.; Cano, J.; Cárdenas
Vázquez, M. C.; Casal, E.; Cifuentes, C.; Claret, A.; Colomé, J.;
Czesla, S.; Díez-Alonso, E.; Feiz, C.; Fernández, M.; Ferro, I. M.;
Fuhrmeister, B.; Galadí-Enríquez, D.; Garcia-Piquer, A.; García
Vargas, M. L.; Gesa, L.; Gómez Galera, V.; González Hernández,
J. I.; González-Peinado, R.; Grözinger, U.; Grohnert, S.; Guijarro,
A.; de Guindos, E.; Gutiérrez-Soto, J.; Hatzes, A. P.; Hauschildt,
P. H.; Hedrosa, R. P.; Helmling, J.; Henning, Th.; Hermelo, I.;
Hernández Arabí, R.; Hernández Castaño, L.; Hernández Hernando,
F.; Herrero, E.; Huber, A.; Huke, P.; Johnson, E. N.; de Juan, E.; Kim,
M.; Klein, R.; Klüter, J.; Klutsch, A.; Kürster, M.; Labarga, F.;
Lamert, A.; Lampón, M.; Lara, L. M.; Laun, W.; Lemke, U.; Lenzen,
R.; Launhardt, R.; López del Fresno, M.; López-González, M. J.;
López-Puertas, M.; López Salas, J. F.; López-Santiago, J.; Luque,
R.; Magán Madinabeitia, H.; Mall, U.; Mancini, L.; Mandel, H.;
Marfil, E.; Marín Molina, J. A.; Maroto Fernández, D.; Martín,
E. L.; Martín-Ruiz, S.; Marvin, C. J.; Mathar, R. J.; Mirabet, E.;
Moreno-Raya, M. E.; Moya, A.; Mundt, R.; Nagel, E.; Naranjo, V.;
Nortmann, L.; Nowak, G.; Ofir, A.; Oreiro, R.; Pallé, E.; Panduro,
J.; Pascual, J.; Pavlov, A.; Pedraz, S.; Pérez-Calpena, A.; Pérez
Medialdea, D.; Perger, M.; Perryman, M. A. C.; Pluto, M.; Rabaza,
O.; Ramón, A.; Rebolo, R.; Redondo, P.; Reffert, S.; Reinhart, S.;
Rhode, P.; Rix, H. -W.; Rodler, F.; Rodríguez, E.; Rodríguez-López,
C.; Rodríguez Trinidad, A.; Rohloff, R. -R.; Rosich, A.; Sadegi,
S.; Sánchez-Blanco, E.; Sánchez Carrasco, M. A.; Sánchez-López,
A.; Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer, S.;
Schmitt, J. H. M. M.; Schiller, J.; Schöfer, P.; Solano, E.; Stahl,
O.; Strachan, J. B. P.; Stürmer, J.; Suárez, J. C.; Tabernero, H. M.;
Tala, M.; Tulloch, S. M.; Ulbrich, R. -G.; Veredas, G.; Vico Linares,
J. I.; Vilardell, F.; Wagner, K.; Winkler, J.; Wolthoff, V.; Xu, W.;
Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2018A&A...609L...5R
Altcode: 2017arXiv171205797R
We report on the first star discovered to host a planet detected by
radial velocity (RV) observations obtained within the CARMENES survey
for exoplanets around M dwarfs. HD 147379 (V = 8.9 mag, M = 0.58 ±
0.08 M⊙), a bright M0.0 V star at a distance of 10.7 pc,
is found to undergo periodic RV variations with a semi-amplitude of
K = 5.1 ± 0.4 m s-1 and a period of P = 86.54 ± 0.06
d. The RV signal is found in our CARMENES data, which were taken
between 2016 and 2017, and is supported by HIRES/Keck observations
that were obtained since 2000. The RV variations are interpreted
as resulting from a planet of minimum mass mP sin i =
25 ± 2 M⊕, 1.5 times the mass of Neptune, with an
orbital semi-major axis a = 0.32 au and low eccentricity (e <
0.13). HD 147379 b is orbiting inside the temperate zone around the
star, where water could exist in liquid form. The RV time-series and
various spectroscopic indicators show additional hints of variations
at an approximate period of 21.1 d (and its first harmonic), which
we attribute to the rotation period of the star. RV data
(Table A.1) 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/609/L5
Title: VizieR Online Data Catalog: HD147379 b velocity curve
(Reiners+, 2018)
Authors: Reiners, A.; Ribas, I.; Zechmeister, M.; Caballero, J. A.;
Trifonov, T.; Dreizler, S.; Morales, J. C.; Tal-Or, L.; Lafarga,
M.; Quirrenbach, A.; Amado, P. J.; Kaminski, A.; Jeffers, S. V.;
Aceituno, J.; Bejar, V. J. S.; Guardia, J.; Guenther, E. W.; Hagen,
H. -J.; Montes, D.; Passegger, V. M.; Seifert, W.; Schweitzer, A.;
Cortes-Contreras, M.; Abril, M.; Alonso-Floriano, F. J.; Ammler-von
Eiff, M.; Antona, R.; Anglada-Escude, G.; Anwand-Heerwart, H.;
Arroyo-Torres, B.; Azzaro, M.; Baroch, D.; Barrado, D.; Bauer, F. F.;
Becerril, S.; Benitez, D.; Berdinas, Z. M.; Bergond, G.; Bluemcke,
M.; Brinkmoeller, M.; Del Burgo, C.; Cano, J.; Cardenas Vazquez,
M. C.; Casal, E.; Cifuentes, C.; Claret, A.; Colome, J.; Czesla, S.;
Diez-Alonso, E.; Feiz, C.; Fernandez, M.; Ferro, I. M.; Fuhrmeister,
B.; Galadi-Enriquez, D.; Garcia-Piquer, A.; Garcia Vargas, M. L.; Gesa,
L.; Gomez Galera, V.; Gonzalez Hernandez, J. I.; Gonzalez-Peinado,
R.; Groezinger, U.; Grohnert, S.; Guijarro, A.; de Guindos, E.;
Gutierrez-Soto, J.; Hatzes, A. P.; Hauschildt, P. H.; Hedrosa,
R. P.; Helml!, Ing J.; H Enning, Th.; Hermelo, I.; Hernandez Arabi,
R.; Hernandez Castano, L.; Hernandez Hernando, F.; Herrero, E.;
Huber, A.; Huke, P.; Johnson, E. N.; de Juan, E.; Kim, M.; Klein,
R.; Klueter, J.; Klutsch, A.; Kuerster, M.; Labarga, F.; Lamert, A.;
Lampon, M.; Lara, L. M.; Laun, W.; Lemke, U.; Lenzen, R.; Launhardt,
R.; Lopez Del Fresno, M.; Lopez-Gonzalez, M. J.; Lopez-Puertas, M.;
Lopez Salas, J. F.; Lopez-Santiago, J.; Luque, R.; Magan Madinabeitia,
H.; Mall, U.; Mancini, L.; Mandel, H.; Marfil, E.; Marin Molina,
J. A.; Maroto Fernandez, D.; Martin, E. L.; Martin-Ruiz, S.; Marvin,
C. J.; Mathar, R. J.; Mirabet, E.; Moreno-Raya, M. E.; Moya, A.;
Mundt, R.; Nagel, E.; Naranjo, V.; Nortmann, L.; Nowak, G.; Ofir, A.;
Oreiro, R.; Palle, E.; Panduro, J.; Pascual, J.; Pavlov, A.; Pedraz,
S.; Perez-Calpena, A.; Perez Medialdea, D.; Perger, M.; Perryman,
M. A. C.; Pluto, M.; Rabaza, O.; Ramon, A.; Rebolo, R.; Redondo,
P.; Reffert, S.; Reinhart, S.; Rhode, P.; Rix, H. -W.; Rodler, F.;
Rodriguez, E.; Rodriguez-Lopez, C.; Rodriguez Trinidad, A.; Rohloff,
R. -R.; Rosich, A.; ! Sadegi, S.; Sanchez-Blanco, E.; Sanchez Carrasco,
M. A.; Sanchez-Lopez, A.; Sanz-Forcada, J.; Sarkis, P.; Sarmiento,
L. F.; Schaefer, S.; Schmitt, J. H. M. M.; Schiller, J.; Schoefer,
P.; Solano, E.; Stahl, O.; Strachan, J. B. P.; Stuermer, J.; Suarez,
J. C.; Tabernero, H. M.; Tala, M.; Tulloch, S. M.; Ulbrich, R. -G.;
Veredas, G.; Vico Linares, J. I.; Vilardell, F.; Wagner, K.; Winkler,
J.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2017yCat..36099005R
Altcode:
We analyzed data from the CARMENES VIS channel and HIRES/Keck. The
CARMENES measurements were taken in the context of the CARMENES search
for exoplanets around M dwarfs. The CARMENES instrument consists of two
channels: the VIS channel obtains spectra at a resolution of R=94600 in
the wavelength range 520-960nm, while the NIR channel yields spectra of
R=80400 covering 960-1710nm. Both channels are calibrated in wavelength
with hollow-cathode lamps and use temperature- and pressure-stabilized
Fabry-Perot etalons to interpolate the wavelength solution and
simultaneously monitor the spectrograph drift during nightly operations
(Bauer et al., 2015A&A...581A.117B). (1 data file).
Title: VizieR Online Data Catalog: CARMENES radial velocity curves
of 7 M-dwarf (Trifonov+, 2018)
Authors: Trifonov, T.; Kuerster, M.; Zechmeister, M.; Tal-Or, L.;
Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners,
A.; Reffert, S.; Dreizler, S.; Hatzes, A. P.; Kaminski, A.; Launhardt,
R.; Henning, T.; Montes, D.; Bejar, V. J. S.; Mundt, R.; Pavlov,
A.; Schmitt, J. H. M. M.; Seifert, W.; Morales, J. C.; Nowak, G.;
Jeffers, S. V.; Rodriguez-Lopez, C.; Del Burgo, C.; Anglada-Escude,
G.; Lopez-Santiago, J.; Mathar, R. J.; Ammler-von Eiff, M.; Guenther,
E. W.; Barrado, D.; Gonzalez Hernandez, J. I.; Mancini, L.; Stuermer,
J.; Abril, M.; Aceituno, J.; Alonso-Floriano, F. J.; Antona, R.;
Anwand-Heerwart, H.; Arroyo-Torres, B.; Azzaro, M.; Baroch, D.;
Bauer, F. F.; Becerril, S.; Benitez, D.; Berdinas, Z. M.; Bergond,
G.; Bluemcke, M.; Brinkmoeller, M.; Cano, J.; Cardenas Vazquez, M. C.;
Casal, E.; Cifuentes, C.; Claret, A.; Colome, J.; Cortes-Contreras, M.;
Czesla, S.; Diez-Alonso, E.; Feiz, C.; Fernandez, M.; Ferro, I. M.;
Fuhrmeister, B.; Galadi-Enriquez, D.; Garcia-Piquer, A.; Garcia
Vargas, M. L.; Gesa, L.; Gomez Galera, V.; Gonzalez-Peinado, R.;
Groezinger, U.; Grohnert, S.; Guardia, J.; Guijarro, A.; de Guindos,
E.; Gutierrez-Soto, J.; Hagen, H. -J.; Hauschildt, P. H.; Hedrosa,
R. P.; Helmling, J.; Hermelo, I.; Hernandez Arabi, R.; Hernandez
Castano, L.; Hernandez Hernando, F.; Herrero, E.; Huber, A.; Huke, P.;
Johnson, E.; de Juan, E.; Kim, M.; Klein, R.; Klueter, J.; Klutsch, A.;
Lafarga, M.; Lampon, M.; Lara, L. M.; Laun, W.; Lemke, U.; Lenzen,
R.; Lopez Del Fresno, M.; Lopez-Gonzalez, J.; Lopez-Puertas, M.;
Lopez Salas, J. F.; Luque, R.; Magan Madinabeitia, H.; Mall, U.;
Mandel, H.; Marfil, E.; Marin Molina, J. A.; Maroto Fernandez, D.;
Martin, E. L.; Martin-Ruiz, S.; Marvin, C. J.; Mirabet, E.; Moya,
A.; Moreno-Raya, M. E.; Nagel, E.; Naranjo, V.; Nortmann, L.; Ofir,
A.; Oreiro, R.; Palle, E.; Panduro, J.; Pascual, J.; Passegger,
V. M.; Pedraz, S.; Perez-Calpena, A.; Perez Medialdea, D.; Perger,
M.; Perryman, M. A. C.; Pluto, M.; Rabaza, O.; Ramon, A.; Rebolo,
R.; Redondo, P.; Reinhardt, S.; Rhode, P.; Rix, H. -W.; Rodler, F.;
Rodriguez, E.; Rodriguez Trinidad, A.; Rohlo, R. -R.; Rosich, A.;
Sadegi, S.; Sanchez-Blanco, E.; Sanchez Carrasco, M. A.; Sanchez-Lopez,
A.; Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schaefer, S.;
Schiller, J.; Schoefer, P.; Schweitzer, A.; Solano, E.; Stahl, O.;
Strachan, J. B. P.; Suarez, J. C.; Tabernero, H. M.; Tala, M.; Tulloch,
S. M.; Veredas, G.; Vico Linares, J. I.; Vilardel, F.; Wagner, K.;
Winkler, J.; Woltho, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.
Bibcode: 2017yCat..36090117T
Altcode:
The two CARMENES spectrographs are grism cross-dispersed, white pupil,
echelle spectrograph working in quasi-Littrow mode using a two-beam,
two-slice image slicer. The visible spectrograph covers the wavelength
range from 0.52um to 1.05um with 61 orders, a resolving power of
R=94600, and a mean sampling of 2.8 pixels per resolution element. The data presented in this paper were taken during the early phase
of operation of the CARMENES visible-light spectrograph. (8
data files).
Title: Surprisingly different star-spot distributions on the near
equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
Authors: Barnes, J. R.; Jeffers, S. V.; Haswell, C. A.; Jones,
H. R. A.; Shulyak, D.; Pavlenko, Ya. V.; Jenkins, J. S.
Bibcode: 2017MNRAS.471..811B
Altcode: 2017arXiv170603979B
We aim to understand how stellar parameters such as mass and rotation
impact the distribution of star-spots on the stellar surface. To this
purpose, we have used Doppler imaging to reconstruct the surface
brightness distributions of three fully convective M dwarfs with
similar rotation rates. We secured high cadence spectral time series
observations of the 5.5 au separation binary GJ 65, comprising GJ 65A
(M5.5V, Prot = 0.24 d) and GJ 65B (M6V, Prot
= 0.23 d). We also present new observations of GJ 791.2A (M4.5V,
Prot = 0.31 d). Observations of each star were made on two
nights with UVES, covering a wavelength range from 0.64 - 1.03μm. The
time series spectra reveal multiple line distortions that we interpret
as cool star-spots and which are persistent on both nights suggesting
stability on the time-scale of 3 d. Spots are recovered with resolutions
down to 8.3° at the equator. The global spot distributions for GJ
791.2A are similar to observations made a year earlier. Similar high
latitude and circumpolar spot structure is seen on GJ 791.2A and GJ
65A. However, they are surprisingly absent on GJ 65B, which instead
reveals more extensive, larger, spots concentrated at intermediate
latitudes. All three stars show small amplitude latitude-dependent
rotation that is consistent with solid body rotation. We compare
our measurements of differential rotation with previous Doppler
imaging studies and discuss the results in the wider context of other
observational estimates and recent theoretical predictions.
Title: The solar proxy κ1 Cet and the planetary
habitability around the young Sun
Authors: do Nascimento, J. -D.; Vidotto, A. A.; Petit, P.; Folsom,
C.; Porto de Mello, G. F.; Meibom, S.; Abrevaya, X. C.; Ribas, I.;
Castro, M.; Marsden, S. C.; Morin, J.; Jeffers, S. V.; Guinan, E.;
Bcool Collaboration
Bibcode: 2017IAUS..328..338D
Altcode:
Among the solar proxies, κ1 Cet, stands out as potentially
having a mass very close to solar and a young age. We report magnetic
field measurements and planetary habitability consequences around this
star, a proxy of the young Sun when life arose on Earth. Magnetic
strength was determined from spectropolarimetric observations and
we reconstruct the large-scale surface magnetic field to derive the
magnetic environment, stellar winds, and particle flux permeating the
interplanetary medium around κ1 Cet. Our results show
a closer magnetosphere and mass-loss rate 50 times larger than the
current solar wind mass-loss rate when Life arose on Earth, resulting
in a larger interaction via space weather disturbances between the
stellar wind and a hypothetical young-Earth analogue, potentially
affecting the habitability. Interaction of the wind from the young
Sun with the planetary ancient magnetic field may have affected the
young Earth and its life conditions.
Title: Efficient scheduling of astronomical observations. Application
to the CARMENES radial-velocity survey
Authors: Garcia-Piquer, A.; Morales, J. C.; Ribas, I.; Colomé, J.;
Guàrdia, J.; Perger, M.; Caballero, J. A.; Cortés-Contreras, M.;
Jeffers, S. V.; Reiners, A.; Amado, P. J.; Quirrenbach, A.; Seifert, W.
Bibcode: 2017A&A...604A..87G
Altcode: 2017arXiv170706052G
Context. Targeted spectroscopic exoplanet surveys face the challenge
of maximizing their planet detection rates by means of careful
planning. For a large planet survey, the number of possible observation
combinations, I.e., the sequence of observations night after night,
both in total time and amount of targets, is enormous.
Aims:
Sophisticated scheduling tools and the improved understanding of
the exoplanet population are employed to investigate an efficient
and optimal way to plan the execution of observations. This is
applied to the CARMENES instrument, which is an optical and infrared
high-resolution spectrograph that has started a survey of about 300
M-dwarf stars in search of terrestrial exoplanets.
Methods:
We used evolutionary computation techniques to create an automatic
scheduler that minimizes the idle periods of the telescope and
distributes the observations among all the targets using configurable
criteria. We simulated the case of the CARMENES survey with a realistic
sample of targets, and we estimated the efficiency of the planning tool
both in terms of telescope operations and planet detection.
Results: Our scheduling simulations produce plans that use about 99%
of the available telescope time (including overheads) and optimally
distribute the observations among the different targets. Under such
conditions, and using current planet statistics, the optimized plan
using this tool should allow the CARMENES survey to discover about 65%
of the planets with radial-velocity semi-amplitudes greater than 1
ms-1 when considering only photon noise.
Conclusions:
The simulations using our scheduling tool show that it is possible to
optimize the survey planning by minimizing idle instrument periods and
fulfilling the science objectives in an efficient manner to maximize
the scientific return.
Title: The relation between stellar magnetic field geometry and
chromospheric activity cycles - I. The highly variable field of ɛ
Eridani at activity minimum
Authors: Jeffers, S. V.; Boro Saikia, S.; Barnes, J. R.; Petit, P.;
Marsden, S. C.; Jardine, M. M.; Vidotto, A. A.; BCool Collaboration
Bibcode: 2017MNRAS.471L..96J
Altcode: 2017arXiv171009227J
The young and magnetically active K dwarf ɛ Eridani exhibits a
chromospheric activity cycle of about 3 yr. Previous reconstructions
of its large-scale magnetic field show strong variations at yearly
epochs. To understand how ɛ Eridani's large-scale magnetic field
geometry evolves over its activity cycle, we focus on high-cadence
observations spanning 5 months at its activity minimum. Over this
time-span, we reconstruct three maps of ɛ Eridani's large-scale
magnetic field using the tomographic technique of Zeeman-Doppler
imaging. The results show that at the minimum of its cycle, ɛ
Eridani's large-scale field is more complex than the simple dipolar
structure of the Sun and 61 Cyg A at minimum. Additionally, we observe
a surprisingly rapid regeneration of a strong axisymmetric toroidal
field as ɛ Eridani emerges from its S-index activity minimum. Our
results show that all stars do not exhibit the same field geometry
as the Sun, and this will be an important constraint for the dynamo
models of active solar-type stars.
Title: Surface magnetism of cool stars
Authors: Kochukhov, O.; Petit, P.; Strassmeier, K. G.; Carroll, T. A.;
Fares, R.; Folsom, C. P.; Jeffers, S. V.; Korhonen, H.; Monnier,
J. D.; Morin, J.; Rosén, L.; Roettenbacher, R. M.; Shulyak, D.
Bibcode: 2017AN....338..428K
Altcode: 2016arXiv161203388K
Magnetic fields are essential ingredients of many physical processes in
the interiors and envelopes of cool stars. Yet their direct detection
and characterization is notoriously difficult, requiring high-quality
observations and advanced analysis techniques. Significant progress has
been recently achieved by several types of direct magnetic field studies
on the surfaces of cool, active stars. In particular, complementary
techniques of field topology mapping with polarization data and
total magnetic flux measurements from intensity spectra have been
systematically applied to different classes of active stars, leading
to interesting and occasionally controversial results. In this paper,
we summarize the current status of direct magnetic field studies of cool
stars and investigations of surface inhomogeneities caused by the field,
based on the material presented at the Cool Stars 19 splinter session.
Title: Recovering planet radial velocity signals in the presence of
starspot activity in fully convective stars
Authors: Barnes, J. R.; Jeffers, S. V.; Anglada-Escudé, G.; Haswell,
C. A.; Jones, H. R. A.; Tuomi, M.; Feng, F.; Jenkins, J. S.; Petit, P.
Bibcode: 2017MNRAS.466.1733B
Altcode: 2016arXiv161200906B
Accounting for stellar activity is a crucial component of the search
for ever-smaller planets orbiting stars of all spectral types. We use
Doppler imaging methods to demonstrate that starspot-induced radial
velocity variability can be effectively reduced for moderately rotating,
fully convective stars. Using starspot distributions extrapolated from
sunspot observations, we adopt typical M dwarf starspot distributions
with low contrast spots to synthesize line profile distortions. The
distortions are recovered using maximum entropy regularized fitting and
the corresponding stellar radial velocities are measured. The procedure
is demonstrated that for a late-M star harbouring an orbiting planet
in the habitable zone. The technique is effective for stars with v sin
I = 1-10km s-1, reducing the stellar noise contribution
by factors of nearly an order of magnitude. With a carefully chosen
observing strategy, the technique can be used to determine the stellar
rotation period and is robust to uncertainties such as unknown stellar
inclination. While demonstrated for late-type M stars, the procedure
is applicable to all spectral types.
Title: Studying stellar spin-down with Zeeman-Doppler magnetograms
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Donati, J. -F.; Boro
Saikia, S.; Fares, R.; Folsom, C. P.; Hébrard, É. M.; Jeffers, S. V.;
Marsden, S. C.; Morin, J.; Petit, P.; Waite, I. A.; BCool Collaboration
Bibcode: 2017MNRAS.466.1542S
Altcode: 2017arXiv170501835S
Magnetic activity and rotation are known to be intimately linked
for low-mass stars. Understanding rotation evolution over the stellar
lifetime is therefore an important goal within stellar astrophysics. In
recent years, there has been increased focus on how the complexity
of the stellar magnetic field affects the rate of angular-momentum
loss from a star. This is a topic that Zeeman-Doppler imaging (ZDI),
a technique that is capable of reconstructing the large-scale magnetic
field topology of a star, can uniquely address. Using a potential field
source surface model, we estimate the open flux, mass-loss rate and
angular-momentum-loss rates for a sample of 66 stars that have been
mapped with ZDI. We show that the open flux of a star is predominantly
determined by the dipolar component of its magnetic field for our choice
of source surface radius. We also show that, on the main sequence,
the open flux, mass-loss and angular-momentum-loss rates increase
with decreasing Rossby number. The exception to this rule is stars
less massive than 0.3 M⊙. Previous work suggests that
low-mass M dwarfs may possess either strong, ordered and dipolar fields
or weak and complex fields. This range of field strengths results in
a large spread of angular-momentum-loss rates for these stars and has
important consequences for their spin-down behaviour. Additionally,
our models do not predict a transition in the mass-loss rates at the
so-called wind-dividing line noted from Lyα studies.
Title: The energy budget of stellar magnetic fields: comparing
non-potential simulations and observations
Authors: Lehmann, L. T.; Jardine, M. M.; Vidotto, A. A.; Mackay,
D. H.; See, V.; Donati, J. -F.; Folsom, C. P.; Jeffers, S. V.; Marsden,
S. C.; Morin, J.; Petit, P.
Bibcode: 2017MNRAS.466L..24L
Altcode: 2016arXiv161008314L
The magnetic geometry of the surface magnetic fields of more than 55
cool stars have now been mapped using spectropolarimetry. In order to
better understand these observations, we compare the magnetic field
topology at different surface scale sizes of observed and simulated
cool stars. For ease of comparison between the high-resolution
non-potential magnetofrictional simulations and the relatively
low-resolution observations, we filter out the small-scale field in
the simulations using a spherical harmonics decomposition. We show
that the large-scale field topologies of the solar-based simulations
produce values of poloidal/toroidal fields and fractions of energy in
axisymmetric modes which are similar to the observations. These global
non-potential evolution model simulations capture key magnetic features
of the observed solar-like stars through the processes of surface
flux transport and magnetic flux emergence. They do not, however,
reproduce the magnetic field of M-dwarfs or stars with dominantly
toroidal field. Furthermore, we analyse the magnetic field topologies
of individual spherical harmonics for the simulations and discover
that the dipole is predominately poloidal, while the quadrupole shows
the highest fraction of toroidal fields. Magnetic field structures
smaller than a quadrupole display a fixed ratio between the poloidal
and toroidal magnetic energies.
Title: BP Piscium: its flaring disc imaged with
SPHERE/ZIMPOL★
Authors: de Boer, J.; Girard, J. H.; Canovas, H.; Min, M.; Sitko,
M.; Ginski, C.; Jeffers, S. V.; Mawet, D.; Milli, J.; Rodenhuis, M.;
Snik, F.; Keller, C. U.
Bibcode: 2017MNRAS.466L...7D
Altcode: 2016arXiv161006609D
Whether BP Piscium (BP Psc) is either a pre-main sequence T Tauri
star at d ≈ 80 pc, or a post-main sequence G giant at d ≈ 300
pc is still not clear. As a first-ascent giant, it is the first to
be observed with a molecular and dust disc. Alternatively, BP Psc
would be among the nearest T Tauri stars with a protoplanetary disc
(PPD). We investigate whether the disc geometry resembles typical PPDs,
by comparing polarimetric images with radiative transfer models. Our
Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet
REsearch (SPHERE)/Zurich IMaging Polarimeter (ZIMPOL) observations
allow us to perform polarimetric differential imaging, reference star
differential imaging, and Richardson-Lucy deconvolution. We present the
first visible light polarization and intensity images of the disc of
BP Psc. Our deconvolution confirms the disc shape as detected before,
mainly showing the southern side of the disc. In polarized intensity
the disc is imaged at larger detail and also shows the northern side,
giving it the typical shape of high-inclination flared discs. We explain
the observed disc features by retrieving the large-scale geometry with
MCMAX radiative transfer modelling, which yields a strongly flared
model, atypical for discs of T Tauri stars.
Title: Characterizing the CARMENES input catalogue of M dwarfs with
low-resolution spectroscopy: metallicity
Authors: Alonso-Floriano, F. J.; Montes, D.; Tabernero, H. M.;
Caballero, J. A.; González-Peinado, R.; Cortés-Contreras, M.; Llamas,
M.; González-Hernández, J. I.; Klutsch, A.; Morales, J. C.; Mundt,
R.; Jeffers, S. V.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners,
A.; Seifert, W.; CARMENES Consortium
Bibcode: 2017hsa9.conf..487A
Altcode:
In this contribution we summarise our science preparation activities
to complete the CARMENES (http://carmenes.caha.es/) input catalogue of
M dwarfs using low-resolution spectroscopy to derive spectral indices
sensible to spectral type, gravity and metallicity as well as the level
of chromospheric activity. We provide here all this information for 181
stars in addition to the 727 stars already published in Alonso-Floriano
et al. (2015). We have developed a calibration of the M-dwarfs
metallicity (Alonso-Floriano et al. 2016) using physical binaries
composed of an F-, G- or K-dwarf primary and an M-dwarf secondary that
allows us to provide the metallicity for all these M dwarfs.
Title: Carmencita, the CARMENES Cool dwarf Information and daTa
Archive
Authors: Caballero, J. A.; Cortés-Contreras, M.; Alonso-Floriano,
F. J.; Montes, D.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners,
A.; Abellán, F. J.; Béjar, V. J. S.; Brinkmoller, M.; Czesla,
S.; Dorda, R.; Gallardo, I.; Hidalgo, D.; Holgado, G.; Fedriani,
R.; González-Alvarez, E.; Jeffers, S. V.; Kim, M.; Klutsch, A.;
Lamert, A.; Llamas, M.; López-Santiago, J.; Martínez-Rodríguez,
H.; Morales, J. C.; Passegger, V. M.; Schofer, P.; Zechmeister, M.
Bibcode: 2017hsa9.conf..496C
Altcode:
CARMENES, the new ultra-stable high-resolution spectrograph at the 3.5 m
Calar Alto telescope and the only one in its category that covers from
0.52 to 1.71μm in one shot, started its guaranteed time observations
(GTO) in January 2016. Under GTO, CARMENES is monitoring approximately
300 selected M dwarfs for at least three years with the aim of finding
rocky planets, perhaps habitable, orbiting around them. Those 300 GTO
stars are the brightest and latest single M dwarfs observable from
Calar Alto, which are carefully picked up from the CARMENES input
catalogue, dubbed ''Carmencita'': CARMENES Cool star Information
and daTa Archive. For each of the over 2200 M dwarfs in Carmencita,
a team of German and Spanish astronomers involving PhD, MSc and BSc
students has collected a large amount of information, compiled from
the literature or measured by us with new data: accurate astrometry,
spectral typing, photometry in 19 bands from the ultraviolet to the
mid-infrared, rotational and radial velocities, X-ray count rates
and hardness ratios, close and wide multiplicity data, kinematics,
derived stellar parameters... The private online catalogue, including
preparatory science observations (i.e., high-resolution imaging,
low-and high-resolution spectroscopy), will be eventually public as
a CARMENES legacy.
Title: CARMENES input catalogue of M dwarfs: High-resolution imaging
with FastCam
Authors: Cortés-Contreras, M.; Béjar, V. J. S.; Caballero, J. A.;
Gauza, B.; Montes, D.; Alonso-Floriano, F. J.; Jeffers, S. V.; Morales,
J. C.; Reiners, A.; Ribas, I.; Schofer, P.; Quirrenbach, A.; Amado,
P. J.; Mundt, R.; Seifert, W.; CARMENES Consortium; del Burgo, Carlos
Bibcode: 2017hsa9.conf..497C
Altcode:
In this contribution we summarise our science preparation activities to
complete the CARMENES input catalogue of M dwarfs using low-resolution
spectroscopy to derive spectral indices sensible to spectral type,
gravity and metallicity as well as the level of chromospheric
activity. We provide here all this information for 181 stars in
addition to the 727 stars already published in Alonso-Floriano et
al. (2015). We have developed a calibration of the M-dwarfs metallicity
(Alonso-Floriano et al. 2016) using physical binaries composed of an
F-, G- or K-dwarf primary and an M-dwarf secondary that allows us to
provide the metallicity for all these M dwarfs.
Title: A BCool survey of the magnetic fields of planet-hosting
solar-type stars
Authors: Mengel, M. W.; Marsden, S. C.; Carter, B. D.; Horner, J.;
King, R.; Fares, R.; Jeffers, S. V.; Petit, P.; Vidotto, A. A.; Morin,
J.; BCool Collaboration
Bibcode: 2017MNRAS.465.2734M
Altcode: 2016arXiv161107604M
We present a spectropolarimetric snapshot survey of solar-type
planet-hosting stars. In addition to 14 planet-hosting stars observed
as part of the BCool magnetic snapshot survey, we obtained magnetic
observations of a further 19 planet-hosting solar-type stars in order to
see if the presence of close-in planets had an effect on the measured
surface magnetic field (|Bℓ|). Our results indicate
that the magnetic activity of this sample is congruent with that of
the overall BCool sample. The effects of the planetary systems on the
magnetic activity of the parent star, if any, are too subtle to detect
compared to the intrinsic dispersion and correlations with rotation,
age and stellar activity proxies in our sample. Four of the 19 newly
observed stars, two of which are subgiants, have unambiguously detected
magnetic fields and are future targets for Zeeman-Doppler mapping.
Title: Magnetic fields on young, moderately rotating Sun-like stars -
II. EK Draconis (HD 129333)
Authors: Waite, I. A.; Marsden, S. C.; Carter, B. D.; Petit, P.;
Jeffers, S. V.; Morin, J.; Vidotto, A. A.; Donati, J. -F.; BCool
Collaboration
Bibcode: 2017MNRAS.465.2076W
Altcode: 2016arXiv161107751W
The magnetic fields, activity and dynamos of young solar-type stars
can be empirically studied using time series of spectropolarimetric
observations and tomographic imaging techniques such as Doppler imaging
and Zeeman-Doppler imaging. In this paper, we use these techniques to
study the young Sun-like star EK Draconis (SpType: G1.5V, HD 129333)
using ESPaDOnS at the Canada-France-Hawaii Telescope and NARVAL at the
Télescope Bernard Lyot. This multi-epoch study runs from late 2006
until early 2012. We measure high levels of chromospheric activity
indicating an active, and varying, chromosphere. Surface brightness
features were constructed for all available epochs. The 2006/2007
and 2008 data show large spot features appearing at intermediate
latitudes. However, the 2012 data indicate a distinctive polar
spot. We observe a strong, almost unipolar, azimuthal field during
all epochs, which is similar to that observed on other Sun-like
stars. Using magnetic features, we determined an average equatorial
rotational velocity, Ωeq, of ∼2.50 ± 0.08 rad d-
1. High levels of surface differential rotation were measured
with an average rotational shear, ΔΩ, of {∼ }0.27_{-0.26}^{+0.24}
rad d- 1. During an intensively observed 3-month period,
from 2006 December until 2007 February, the magnetic field went
from predominantly toroidal (∼80 per cent) to a more balanced
poloidal-toroidal (∼40-60 per cent) field. Although the large-scale
magnetic field evolved over the epochs of our observations, no polarity
reversals were found in our data.
Title: CARMENES input catalogue of M dwarfs. II. High-resolution
imaging with FastCam
Authors: Cortés-Contreras, M.; Béjar, V. J. S.; Caballero, J. A.;
Gauza, B.; Montes, D.; Alonso-Floriano, F. J.; Jeffers, S. V.; Morales,
J. C.; Reiners, A.; Ribas, I.; Schöfer, P.; Quirrenbach, A.; Amado,
P. J.; Mundt, R.; Seifert, W.
Bibcode: 2017A&A...597A..47C
Altcode: 2016arXiv160808145C; 2016A&A...597A..47C
Aims: We search for low-mass companions of M dwarfs and
characterize their multiplicity fraction with the purpose of helping
in the selection of the most appropriate targets for the CARMENES
exoplanet survey.
Methods: We obtained high-resolution images
in the I band with the lucky imaging instrument FastCam at the 1.5 m
Telescopio Carlos Sánchez for 490 mid- to late-M dwarfs. For all the
detected binaries, we measured angular separations, position angles,
and magnitude differences in the I band. We also calculated the
masses of each individual component and estimated orbital periods,
using the available magnitude and colour relations for M dwarfs
and our own MJ-spectral type and mass-MI
relations. To avoid biases in our sample selection, we built a
volume-limited sample of M0.0-M5.0 dwarfs that is complete up to 86%
within 14 pc.
Results: From the 490 observed stars, we detected
80 companions in 76 systems, of which 30 are new discoveries. Another
six companion candidates require additional astrometry to confirm
physical binding. The multiplicity fraction in our observed sample
is 16.7 ± 2.0%. The bias-corrected multiplicity fraction in our
volume-limited sample is 19.5 ± 2.3% for angular separations of
0.2 to 5.0 arcsec (1.4-65.6 au), with a peak in the distribution of
the projected physical separations at 2.5-7.5 au. For M0.0-M3.5 V
primaries, our search is sensitive to mass ratios higher than 0.3
and there is a higher density of pairs with mass ratios over 0.8
compared to those at lower mass ratios. Binaries with projected
physical separations shorter than 50 au also tend to be of equal
mass. For 26 of our systems, we estimated orbital periods shorter than
50 a, 10 of which are presented here for the first time. We measured
variations in angular separation and position angle that are due to
orbital motions in 17 of these systems. The contribution of binaries
and multiples with angular separations shorter than 0.2 arcsec,
longer than 5.0 arcsec, and of spectroscopic binaries identified from
previous searches, although not complete, may increase the multiplicity
fraction of M dwarfs in our volume-limited sample to at least 36%. Tables A.1-A.6 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/597/A47
Title: The connection between stellar activity cycles and magnetic
field topology
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Donati, J. -F.; Boro
Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C. P.; Gregory, S. G.;
Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.;
do Nascimento, J. D.; Petit, P.; Waite, I. A.
Bibcode: 2016MNRAS.462.4442S
Altcode: 2016MNRAS.tmp.1129S; 2016arXiv161003737S
Zeeman-Doppler imaging (ZDI) has successfully mapped the large-scale
magnetic fields of stars over a large range of spectral types,
rotation periods and ages. When observed over multiple epochs, some
stars show polarity reversals in their global magnetic fields. On
the Sun, polarity reversals are a feature of its activity cycle. In
this paper, we examine the magnetic properties of stars with existing
chromospherically determined cycle periods. Previous authors have
suggested that cycle periods lie on multiple branches, either in the
cycle period-Rossby number plane or the cycle period-rotation period
plane. We find some evidence that stars along the active branch show
significant average toroidal fields that exhibit large temporal
variations while stars exclusively on the inactive branch remain
dominantly poloidal throughout their entire cycle. This lends credence
to the idea that different shear layers are in operation along each
branch. There is also evidence that the short magnetic polarity switches
observed on some stars are characteristic of the inactive branch while
the longer chromospherically determined periods are characteristic
of the active branch. This may explain the discrepancy between the
magnetic and chromospheric cycle periods found on some stars. These
results represent a first attempt at linking global magnetic field
properties obtained from ZDI and activity cycles.
Title: No Evidence for Activity Correlations in the Radial Velocities
of Kapteyn’s Star
Authors: Anglada-Escudé, G.; Tuomi, M.; Arriagada, P.; Zechmeister,
M.; Jenkins, J. S.; Ofir, A.; Dreizler, S.; Gerlach, E.; Marvin, C. J.;
Reiners, A.; Jeffers, S. V.; Butler, R. Paul; Vogt, S. S.; Amado,
P. J.; Rodríguez-López, C.; Berdiñas, Z. M.; Morin, J.; Crane,
J. D.; Shectman, S. A.; Díaz, M. R.; Sarmiento, L. F.; Jones, H. R. A.
Bibcode: 2016ApJ...830...74A
Altcode: 2015arXiv150609072A
Stellar activity may induce Doppler variability at the level of a few
m s-1 which can then be confused by the Doppler signal of
an exoplanet orbiting the star. To first order, linear correlations
between radial velocity measurements and activity indices have been
proposed to account for any such correlation. The likely presence of two
super-Earths orbiting Kapteyn’s star was reported in Anglada-Escudé
et al., but this claim was recently challenged by Robertson et al.,
who argued for evidence of a rotation period (143 days) at three times
the orbital period of one of the proposed planets (Kapteyn’s b, P =
48.6 days) and the existence of strong linear correlations between
its Doppler signal and activity data. By re-analyzing the data using
global statistics and model comparison, we show that such a claim is
incorrect given that (1) the choice of a rotation period at 143 days
is unjustified, and (2) the presence of linear correlations is not
supported by the data. We conclude that the radial velocity signals of
Kapteyn’s star remain more simply explained by the presence of two
super-Earth candidates orbiting it. We note that analysis of time series
of activity indices must be executed with the same care as Doppler time
series. We also advocate for the use of global optimization procedures
and objective arguments, instead of claims based on residual analyses
which are prone to biases and incorrect interpretations.
Title: A solar-like magnetic cycle on the mature K-dwarf 61 Cygni A
(HD 201091)
Authors: Boro Saikia, S.; Jeffers, S. V.; Morin, J.; Petit, P.;
Folsom, C. P.; Marsden, S. C.; Donati, J. -F.; Cameron, R.; Hall,
J. C.; Perdelwitz, V.; Reiners, A.; Vidotto, A. A.
Bibcode: 2016A&A...594A..29B
Altcode: 2016arXiv160601032B
Context. The long-term monitoring of magnetic cycles in cool stars is a
key diagnostic in understanding how dynamo generation and amplification
of magnetic fields occur in stars similar in structure to the Sun.
Aims: We investigated the temporal evolution of a possible magnetic
cycle of 61 Cyg A. The magnetic cycle is determined from 61 Cyg A's
large-scale field over its activity cycle using spectropolarimetric
observations and compared to the solar large-scale magnetic field.
Methods: We used the tomographic technique of Zeeman Doppler imaging
(ZDI) to reconstruct the large-scale magnetic geometry of 61 Cyg A
over multiple observational epochs spread over a time span of nine
years. We investigated the time evolution of the different components
of the large-scale field and compared it with the evolution of the
star's chromospheric activity by measuring the flux in three different
chromospheric indicators: Ca II H&K, Hα and Ca II infrared triplet
lines. We also compared our results with the star's coronal activity
using XMM-Newton observations.
Results: The large-scale magnetic
geometry of 61 Cyg A exhibits polarity reversals in both poloidal and
toroidal field components, in phase with its chromospheric activity
cycle. We also detect weak solar-like differential rotation with
a shear level similar to that of the Sun. During our observational
time span of nine years, 61 Cyg A exhibits solar- like variations in
its large-scale field geometry as it evolves from minimum activity
to maximum activity and vice versa. During its activity minimum in
epoch 2007.59, ZDI reconstructs a simple dipolar geometry which becomes
more complex when it approaches activity maximum in epoch 2010.55. The
radial field flips polarity and reverts back to a simple geometry in
epoch 2013.61. The field is strongly dipolar and the evolution of the
dipole component of the field is reminiscent of solar behaviour. The
polarity reversal of the large-scale field indicates a magnetic cycle
that is in phase with the chromospheric and coronal cycle.
Title: VizieR Online Data Catalog: CARMENES input catalogue of M
dwarfs II (Cortes-Contreras+ 2017)
Authors: Cortes-Contreras, M.; Bejar, V. J. S.; Caballero, J. A.;
Gauza, B.; Montes, D.; Alonso-Floriano, F. J.; Jeffers, S. V.; Morales,
J. C.; Reiners, A.; Ribas, I.; Schoefer, P.; Quirrenbach, A.; Amado,
P. J.; Mundt, R.; Seifert, W.
Bibcode: 2016yCat..35970047C
Altcode:
From the 490 observed stars, we detected 80 companions in 76 systems, of
which 30 are new discoveries. Another six companion candidates require
additional astrometry to confirm physical binding. (6 data files).
Title: Measurements Of Absolute Ca II H And K Flux In FGKM Stars
Authors: Marvin, Christopher; Reiners, A.; Anglada-Escudé, G.;
Jeffers, S.; Boro-Saikia, S.
Bibcode: 2016csss.confE...8M
Altcode:
M dwarfs are the most numerous stars in the universe, yet they still
lack absolute chromospheric Ca II H and K (R'_HK) calibrations to
effectively compare their activity with FGK stars. We scale high-S/N,
high-resolution template spectra, obtained by co-adding multiple HARPS
spectra of the same star, to PHOENIX stellar atmosphere models, and
obtain chromospheric line measurements of Ca II H & K in physical
units of 106 M dwarfs. We also derive new Mt. Wilson S-index to R'_HK
conversions appropriate for cooler stars, ranging from 0.82 <=
B-V <= 2.00. We establish a chromospheric activity database by
combining archival data of FGK stars and using our technique to extend
absolute chromospheric measurements to M dwarfs. Our results show that
using model atmospheres provides a reliable way to scale uncalibrated
spectra and also estimate photospheric flux for M dwarfs, but note
that accurate stellar parameter determination is essential to compare
chromospheric emission of different spectral types.
Title: Acne at The Bottom Of The Main Sequence
Authors: Barnes, John; Haswell, C.; Jenkins, J.; Jeffers, S.; Jones,
H. R. A.; Lohr, M.; Pavlenko, Y.
Bibcode: 2016csss.confE..10B
Altcode:
Starspots are an important manifestation of stellar activity and
yet their distribution patterns on the lowest mass stars is not well
known. Time series spectra of fully convective M dwarfs taken in the
red-optical with UVES reveal numerous line profile distortions which are
interpreted as starspots. We derive Doppler images for four M4.5V - M9V
stars and find that contrast ratios corresponding to photosphere-spot
temperature differences of only 200-300 K are sufficient to model
the timeseries spectra. Although more starspot structure is found
at high latitudes, spots are reconstructed at a range of phases and
latitudes with mean spot filling factors of only a few per cent. The
occurrence of low-contrast spots at predominantly high latitudes is
in general likely to be responsible for the low amplitude photometric
variability seen in late-M dwarfs. The recovered starspot patterns
are used to assess their effect on precision radial velocity surveys
aimed at detecting planets around this population of stars.
Title: VizieR Online Data Catalog: Stellar magnetism, age and rotation
(Vidotto+, 2014)
Authors: Vidotto, A. A.; Gregory, S. G.; Jardine, M.; Donati, J. F.;
Petit, P.; Morin, J.; Folsom, C. P.; Bouvier, J.; Cameron, A. C.;
Hussain, G.; Marsden, S.; Waite, I. A.; Fares, R.; Jeffers, S.;
Do Nascimento, J. D. Jr
Bibcode: 2016yCat..74412361V
Altcode:
The stars considered in this study consist of 73 late-F, G, K and M
dwarf stars, in the PMS to MS phases. All have had their large-scale
surface magnetic fields reconstructed using the ZDI technique, with some
having been observed at multiple epochs. File table1.dat contains
the objects in our sample. Columns are: star name, spectral type,
mass, radius, rotation period, Rossby number, age, X-ray luminosity,
X-ray-to-bolometric luminosity ratio, average large-scale unsigned
surface magnetic field and its observation epoch (year and month). The
measurement errors associated to these quantities are described in
Appendix A. References for the values compiled in this table are
shown in the last column, in the format presented by CDS and SAO/NASA
ADS, except for Petit2014, Folsom2014 and Waite2014, which were in
preparation by the time of writing. (1 data file).
Title: A terrestrial planet candidate in a temperate orbit around
Proxima Centauri
Authors: Anglada-Escudé, Guillem; Amado, Pedro J.; Barnes, John;
Berdiñas, Zaira M.; Butler, R. Paul; Coleman, Gavin A. L.; de La
Cueva, Ignacio; Dreizler, Stefan; Endl, Michael; Giesers, Benjamin;
Jeffers, Sandra V.; Jenkins, James S.; Jones, Hugh R. A.; Kiraga,
Marcin; Kürster, Martin; López-González, María J.; Marvin,
Christopher J.; Morales, Nicolás; Morin, Julien; Nelson, Richard P.;
Ortiz, José L.; Ofir, Aviv; Paardekooper, Sijme-Jan; Reiners, Ansgar;
Rodríguez, Eloy; Rodríguez-López, Cristina; Sarmiento, Luis F.;
Strachan, John P.; Tsapras, Yiannis; Tuomi, Mikko; Zechmeister, Mathias
Bibcode: 2016Natur.536..437A
Altcode: 2016arXiv160903449A
At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α
Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun’s closest
stellar neighbour and one of the best-studied low-mass stars. It has
an effective temperature of only around 3,050 kelvin, a luminosity of
0.15 per cent of that of the Sun, a measured radius of 14 per cent of
the radius of the Sun and a mass of about 12 per cent of the mass of
the Sun. Although Proxima is considered a moderately active star, its
rotation period is about 83 days (ref. 3) and its quiescent activity
levels and X-ray luminosity are comparable to those of the Sun. Here
we report observations that reveal the presence of a small planet
with a minimum mass of about 1.3 Earth masses orbiting Proxima with
a period of approximately 11.2 days at a semi-major-axis distance of
around 0.05 astronomical units. Its equilibrium temperature is within
the range where water could be liquid on its surface.
Title: CARMENES: an overview six months after first light
Authors: Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Mundt,
R.; Reiners, A.; Ribas, I.; Seifert, W.; Abril, M.; Aceituno, J.;
Alonso-Floriano, F. J.; Anwand-Heerwart, H.; Azzaro, M.; Bauer, F.;
Barrado, D.; Becerril, S.; Bejar, V. J. S.; Benitez, D.; Berdinas,
Z. M.; Brinkmöller, M.; Cardenas, M. C.; Casal, E.; Claret, A.;
Colomé, J.; Cortes-Contreras, M.; Czesla, S.; Doellinger, M.;
Dreizler, S.; Feiz, C.; Fernandez, M.; Ferro, I. M.; Fuhrmeister,
B.; Galadi, D.; Gallardo, I.; Gálvez-Ortiz, M. C.; Garcia-Piquer,
A.; Garrido, R.; Gesa, L.; Gómez Galera, V.; González Hernández,
J. I.; Gonzalez Peinado, R.; Grözinger, U.; Guàrdia, J.; Guenther,
E. W.; de Guindos, E.; Hagen, H. -J.; Hatzes, A. P.; Hauschildt,
P. H.; Helmling, J.; Henning, T.; Hermann, D.; Hernández Arabi, R.;
Hernández Castaño, L.; Hernández Hernando, F.; Herrero, E.; Huber,
A.; Huber, K. F.; Huke, P.; Jeffers, S. V.; de Juan, E.; Kaminski,
A.; Kehr, M.; Kim, M.; Klein, R.; Klüter, J.; Kürster, M.; Lafarga,
M.; Lara, L. M.; Lamert, A.; Laun, W.; Launhardt, R.; Lemke, U.;
Lenzen, R.; Llamas, M.; Lopez del Fresno, M.; López-Puertas, M.;
López-Santiago, J.; Lopez Salas, J. F.; Magan Madinabeitia, H.; Mall,
U.; Mandel, H.; Mancini, L.; Marin Molina, J. A.; Maroto Fernández,
D.; Martín, E. L.; Martín-Ruiz, S.; Marvin, C.; Mathar, R. J.;
Mirabet, E.; Montes, D.; Morales, J. C.; Morales Muñoz, R.; Nagel,
E.; Naranjo, V.; Nowak, G.; Palle, E.; Panduro, J.; Passegger, V. M.;
Pavlov, A.; Pedraz, S.; Perez, E.; Pérez-Medialdea, D.; Perger,
M.; Pluto, M.; Ramón, A.; Rebolo, R.; Redondo, P.; Reffert, S.;
Reinhart, S.; Rhode, P.; Rix, H. -W.; Rodler, F.; Rodríguez, E.;
Rodríguez López, C.; Rohloff, R. R.; Rosich, A.; Sanchez Carrasco,
M. A.; Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer,
S.; Schiller, J.; Schmidt, C.; Schmitt, J. H. M. M.; Schöfer,
P.; Schweitzer, A.; Shulyak, D.; Solano, E.; Stahl, O.; Storz, C.;
Tabernero, H. M.; Tala, M.; Tal-Or, L.; Ulbrich, R. -G.; Veredas, G.;
Vico Linares, J. I.; Vilardell, F.; Wagner, K.; Winkler, J.; Zapatero
Osorio, M. -R.; Zechmeister, M.; Ammler-von Eiff, M.; Anglada-Escudé,
G.; del Burgo, C.; Garcia-Vargas, M. L.; Klutsch, A.; Lizon, J. -L.;
Lopez-Morales, M.; Ofir, A.; Pérez-Calpena, A.; Perryman, M. A. C.;
Sánchez-Blanco, E.; Strachan, J. B. P.; Stürmer, J.; Suárez, J. C.;
Trifonov, T.; Tulloch, S. M.; Xu, W.
Bibcode: 2016SPIE.9908E..12Q
Altcode:
The CARMENES instrument is a pair of high-resolution (R> 80,000)
spectrographs covering the wavelength range from 0.52 to 1.71 μm,
optimized for precise radial velocity measurements. It was installed
and commissioned at the 3.5m telescope of the Calar Alto observatory
in Southern Spain in 2015. The first large science program of CARMENES
is a survey of 300 M dwarfs, which started on Jan 1, 2016. We present
an overview of all subsystems of CARMENES (front end, fiber system,
visible-light spectrograph, near-infrared spectrograph, calibration
units, etalons, facility control, interlock system, instrument control
system, data reduction pipeline, data flow, and archive), and give an
overview of the assembly, integration, verification, and commissioning
phases of the project. We show initial results and discuss further
plans for the scientific use of CARMENES.
Title: OCTOCAM: a fast multi-channel imager and spectrograph proposed
for the Gemini Observatory
Authors: de Ugarte Postigo, A.; Roming, P.; Thöne, C. C.; van der
Horst, A. J.; Pope, S.; García Vargas, M. L.; Sánchez-Blanco, E.;
Maldonado Medina, M.; Content, R.; Snik, F.; Killough, R.; Winters,
G.; Persson, K.; Jeffers, S.; Riva, A.; Bianco, A.; Zanutta, A.
Bibcode: 2016SPIE.9908E..40D
Altcode:
OCTOCAM has been proposed to the Gemini Observatory as a workhorse
imager and spectrograph that will fulfill the needs of a large number of
research areas in the 2020s. It is based on the use of high-efficiency
dichroics to divide the incoming light in eight different channels, four
optical and four infrared, each optimized for its wavelength range. In
its imaging mode, it will observe a field of 3'x3' simultaneously in g,
r, i, z, Y, J, H, and KS bands. It will obtain long-slit spectroscopy
covering the range from 3700 to 23500 Å with a resolution of 4000 and
a slit length of 3 arcminutes. To avoid slit losses, the instrument
it will be equipped with an atmospheric dispersion corrector for
the complete spectral range. Thanks to the use of state of the art
detectors, OCTOCAM will allow high time-resolution observations and
will have negligible overheads in classical observing modes. It will
be equipped with a unique integral field unit that will observe in
the complete spectral range with an on-sky coverage of 9.7"x6.8",
composed of 17 slitlets, 0.4" wide each. Finally, a state-of-the-art
polarimetric unit will allow us to obtain simultaneous full Stokes
spectropolarimetry of the range between 3700 and 22000 Å.
Title: Carmencita, The CARMENES Input Catalogue of Bright, Nearby
M Dwarfs
Authors: Caballero, J. A.; Cortés-Contreras, M.; Alonso-Floriano,
F. J.; Montes, D.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners,
A.; Abellan, F. J.; Béjar, V. J. S.; Brinkmöller, M.; Czesla, S.;
Dorda, R.; Gallardo, I.; González-Álvarez, E.; Hidalgo, D.; Holgado,
G.; Jeffers, S. V.; Kim, M.; Klutsch, A.; Lamert, A.; Llamas, M.;
López-Santiago, J.; Martínez-Rodríguez, H.; Morales, J. C.; Mundt,
R.; Passegger, V. M.; Schöfer, P.; Seifert, W.; Zechmeister, M.
Bibcode: 2016csss.confE.148C
Altcode:
CARMENES, the brand-new, Spanish-German, two-channel, ultra-stabilised,
high-resolution spectrograph at the 3.5 m Calar Alto telescope,
started its science survey on 01 Jan 2016. In one shot, it covers
from 0.52 to 1.71 μm with resolution R = 94,600 (λ < 0.96 μm)
and 80,400 (λ > 0.96 μm). During guaranteed time observations,
CARMENES carries out the programme for which the instrument was
designed: radial-velocity monitoring of bright, nearby, low-mass
dwarfs with spectral types be- tween M0.0 V and M9.5 V. Carmencita is
the "CARMEN(ES) Cool dwarf Information and daTa Archive", our input
catalogue, from which we select the about 300 targets being observed
during guaranteed time. Besides that, Carmencita is perhaps the most
comprehensive database of bright, nearby M dwarfs ever built, as
well as a useful tool for forthcoming exo-planet hunters: ESPRESSO,
HPF, IRD, SPIRou, TESS or even PLATO. Carmencita contains dozens of
parameters measured by us or compiled from the literature for about
2,200 M dwarfs in the solar neighbourhood brighter than J = 11.5 mag:
accurate coordinates, spectral types, photometry from ultraviolet to
mid-infrared, parallaxes and spectro-photometric distances, rotational
and radial velocities, Hα pseudo-equivalent widths, X-ray count rates
and hardness ratios, close and wide multiplicity data, proper motions,
Galactocentric space velocities, metallicities, full references,
homogeneously derived astrophysical parameters, and much more. In my
talk at Cool Stars 19, I explained how we build Carmencita standing
on the shoulders of giants and observing with 2-m class telescopes,
and produce a dozen MSc theses and several PhD theses in the process
(http://carmenes.caha.es).
Title: What Can We Learn About Stellar Activity Cycles From ZDI?
Authors: See, Victor; Jardine, M.; Vidotto, A.; Donati, J. -F.; Boro
Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C.; Gregory, S.; Hussain,
G.; Jeffers, S.; Marsden, S.; Morin, J.; Moutou, C.; do Nascimento,
J. D.; Petit, P.; Waite, I.; +BCool Collaboration
Bibcode: 2016csss.confE..25S
Altcode:
It is known that activity cycles, similar to the 11 year cycle of
the Sun, can exist on other stars. Previous work suggests that stars
may lie on two branches in a cycle period vs rotation period diagram
though there is no definitive explanation for why this should be the
case. Fundamentally, activity cycles occur as a result of the underlying
dynamo. Indeed, a great deal has been learnt about the Sun's activity
cycle by studying how its magnetic field evolves over each activity
cycle. In the same way, we should be able to learn about the activity
cycles of other stars by studying their magnetic field properties. In
this talk, I will present new insights into stellar activity cycles
by analysing the magnetic maps of stars that are known to present
activity cycles. I will show that stars along each of the branches
appear to have different magnetic field topologies.
Title: Photospheric Acne at The Bottom of the Main-Sequence: Doppler
Images of M4.5 - M9V Stars
Authors: Barnes, John R.; Haswell, Carole A.; Jeffers, Sandra V.;
Jones, Hugh R. A.; Pavlenko, Yakiv V.; Lohr, Marcus E.; Jenkins,
James S.
Bibcode: 2016csss.confE.132B
Altcode:
Starspots are an important manifestation of stellar activity and
yet their distribution patterns on the lowest mass stars is notwell
known. Time series spectra of fullyconvective M dwarfs taken in
the red-optical with UVES reveal numerous line profiledistortions
which are interpreted as starspots. New Doppler images of HU Del
(GJ 791.2A; M4.5V), BL Ceti (GJ 65A; M5.5V)and UV Ceti (GJ 65B;
M6V) attwoepochs separated by three nights are presented. We find
that contrastratioscorrespondingto photosphere-spot temperature
differences of only 100-400 Kare sufficient to model the time series
spectra of M4.5V - M9Vstars. Starspotsare reconstructed at a range of
phases and latitudes with mean spot filling factors of only a few per
cent.The distribution and low-contrast of the spots/spot-groups that we
recover are likely to be responsible for the low amplitudephotometric
variability seen in late-M dwarfs. The stability of the spot patterns
in the two sets of timeseries observationsenables us to measure the
latitude dependent differential rotation, which we find to be consistent
with zero.
Title: The evolving magnetic topology of τ Boötis
Authors: Mengel, M. W.; Fares, R.; Marsden, S. C.; Carter, B. D.;
Jeffers, S. V.; Petit, P.; Donati, J. -F.; Folsom, C. P.; BCool
Collaboration
Bibcode: 2016MNRAS.459.4325M
Altcode: 2016MNRAS.tmp..723F; 2016arXiv160402501M
We present six epochs of spectropolarimetric observations of the
hot-Jupiter-hosting star τ Boötis that extend the exceptional previous
multiyear data set of its large-scale magnetic field. Our results
confirm that the large-scale magnetic field of τ Boötis varies
cyclicly, with the observation of two further magnetic reversals;
between 2013 December and 2014 May and between 2015 January and
March. We also show that the field evolves in a broadly solar-type
manner in contrast to other F-type stars. We further present new
results which indicate that the chromospheric activity cycle and the
magnetic activity cycles are related, which would indicate a very rapid
magnetic cycle. As an exemplar of long-term magnetic field evolution,
τ Boötis and this long-term monitoring campaign presents a unique
opportunity for studying stellar magnetic cycles.
Title: Spectroscopic Characterisation of CARMENES Target Candidates
from FEROS, CAFE and HRS High-Resolution Spectra
Authors: Passegger, Vera Maria; Reiners, Ansgar; Jeffers, Sandra V.;
Wende, Sebastian; Schöfer, Patrick; Amado, Pedro J.; Caballero, Jose
A.; Montes, David; Mundt, Reinhard; Ribas, Ignasi; Quirrenbach, Andreas
Bibcode: 2016csss.confE.109P
Altcode: 2016csss.confE.108P; 2016arXiv160708738P
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths
with Near-infrared and optical Échelle Spectrographs) started a new
planet survey on M-dwarfs in January this year. The new high-resolution
spectrographs are operating in the visible and near-infrared at Calar
Alto Observatory. They will perform high-accuracy radial-velocity
measurements (goal 1 m s-1) of about 300 M-dwarfs with the aim to
detect low-mass planets within habitable zones. We characterised the
candidate sample for CARMENES and provide fundamental parameters for
these stars in order to constrain planetary properties and understand
star-planet systems. Using state-of-the-art model atmospheres
(PHOENIX-ACES) and χ2-minimization with a downhill-simplex method
we determine effective temperature, surface gravity and metallicity
[Fe/H] for high-resolution spectra of around 480 stars of spectral
types M0.0-6.5V taken with FEROS, CAFE and HRS. We find good agreement
between the models and our observed high-resolution spectra. We show
the performance of the algorithm, as well as results, parameter and
spectral type distributions for the CARMENES candidate sample, which
is used to define the CARMENES target sample. We also present first
preliminary results obtained from CARMENES spectra.
Title: Temporal variability of the wind from the star τ Boötis
Authors: Nicholson, B. A.; Vidotto, A. A.; Mengel, M.; Brookshaw,
L.; Carter, B.; Petit, P.; Marsden, S. C.; Jeffers, S. V.; Fares,
R.; BCool Collaboration
Bibcode: 2016MNRAS.459.1907N
Altcode: 2016MNRAS.tmp..521N; 2016arXiv160309242N
We present new wind models for τ Boötis (τ Boo), a
hot-Jupiter-host-star whose observable magnetic cycles makes it
a uniquely useful target for our goal of monitoring the temporal
variability of stellar winds and their exoplanetary impacts. Using
spectropolarimetric observations from May 2009 to January 2015, the
most extensive information of this type yet available, to reconstruct
the stellar magnetic field, we produce multiple 3D magnetohydrodynamic
stellar wind models. Our results show that characteristic changes in
the large-scale magnetic field as the star undergoes magnetic cycles
produce changes in the wind properties, both globally and locally at the
position of the orbiting planet. Whilst the mass loss rate of the star
varies by only a minimal amount (∼4 per cent), the rates of angular
momentum loss and associated spin-down time-scales are seen to vary
widely (up to ∼140 per cent), findings consistent with and extending
previous research. In addition, we find that temporal variation in the
global wind is governed mainly by changes in total magnetic flux rather
than changes in wind plasma properties. The magnetic pressure varies
with time and location and dominates the stellar wind pressure at the
planetary orbit. By assuming a Jovian planetary magnetic field for τ
Boo b, we nevertheless conclude that the planetary magnetosphere can
remain stable in size for all observed stellar cycle epochs, despite
significant changes in the stellar field and the resulting local space
weather environment.
Title: The Magnetic Field Geometry of Cool Stars
Authors: See, Victor; Jardine, Moira; Vidotto, Aline; Donati,
Jean-Francois; Folsom, Colin; Boro Saikia, Sudeshna; Bouvier, Jerome;
Fares, Rim; Gregory, Scott; Hussain, Gaitee; Jeffers, Sandra; Marsden,
Stephen; Morin, Julien; Moutou, Claire; do Nascimento, Jose-Dias,
Jr.; Petit, Pascal; Rosen, Lisa; Waite, Ian
Bibcode: 2016csss.confE..82S
Altcode:
Zeeman-Doppler imaging has been used to map the large-scale surface
magnetic fields of cool stars across a wide range of stellar masses
and rotation periods. The derived field geometries are surprising,
with many stars showing strong azimuthal fields that are not observed
on the Sun. In this poster, using 100 magnetic maps of over 50 stars,
we present results showing how the magnetic field geometry of cool stars
varies as a function of fundamental parameters. The stellar mass, and
hence internal structure, critically influences the field geometry,
although this is modified by the stellar rotation rate. We discuss
the implications of these results for dynamo theory and the nature of
stellar magnetic activity.
Title: Hunting For Strong Magnetic Fields In Rapidly Rotating Sun-Like
Stars With Stokes-I Observations
Authors: Shulyak, Denis; Malo, Lison; Reiners, Ansgar; Kochukhov,
Oleg; Jeffers, Sandra; Piskunov, Nikolai
Bibcode: 2016csss.confE.118S
Altcode:
Stars with convective envelopes can generate strong magnetic fields
through rotationally driven dynamos. Theory suggests that the
maximum
magnetic field strength depends on the energy budget
stored in
the stellar convective shell and can reach values
of several kilogauss
in fastest rotating stars. We test this
predictions by measuring
total magnetic flux and polarization
in a sample of sun-like stars
that rotate close to the activity
saturation limit.
We detect average magnetic flux densities of
several hundred G in several of our targets,with the strongest field
of about 1 kG in a K type star V383 Lac showing that young sun-like
starscan produce average fields on the kG level.
Title: The evolution of surface magnetic fields in young solar-type
stars - I. The first 250 Myr
Authors: Folsom, C. P.; Petit, P.; Bouvier, J.; Lèbre, A.; Amard,
L.; Palacios, A.; Morin, J.; Donati, J. -F.; Jeffers, S. V.; Marsden,
S. C.; Vidotto, A. A.
Bibcode: 2016MNRAS.457..580F
Altcode: 2016arXiv160100684F
The surface rotation rates of young solar-type stars vary rapidly
with age from the end of the pre-main sequence through the early main
sequence. Important changes in the dynamos operating in these stars
may result from this evolution, which should be observable in their
surface magnetic fields. Here we present a study aimed at observing
the evolution of these magnetic fields through this critical time
period. We observed stars in open clusters and stellar associations
of known ages, and used Zeeman Doppler imaging to characterize their
complex magnetic large-scale fields. Presented here are results for 15
stars, from five associations, with ages from 20 to 250 Myr, masses
from 0.7 to 1.2 M⊙, and rotation periods from 0.4 to 6
d. We find complex large-scale magnetic field geometries, with global
average strengths from 14 to 140 G. There is a clear trend towards
decreasing average large-scale magnetic field strength with age,
and a tight correlation between magnetic field strength and Rossby
number. Comparing the magnetic properties of our zero-age main-sequence
sample to those of both younger and older stars, it appears that the
magnetic evolution of solar-type stars during the pre-main sequence
is primarily driven by structural changes, while it closely follows
the stars' rotational evolution on the main sequence.
Title: Magnetic Field and Wind of Kappa Ceti: Toward the Planetary
Habitability of the Young Sun When Life Arose on Earth
Authors: do Nascimento, J. -D., Jr.; Vidotto, A. A.; Petit, P.;
Folsom, C.; Castro, M.; Marsden, S. C.; Morin, J.; Porto de Mello,
G. F.; Meibom, S.; Jeffers, S. V.; Guinan, E.; Ribas, I.
Bibcode: 2016ApJ...820L..15D
Altcode: 2016arXiv160303937D
We report magnetic field measurements for κ1 Cet, a proxy
of the young Sun when life arose on Earth. We carry out an analysis
of the magnetic properties determined from spectropolarimetric
observations and reconstruct the large-scale surface magnetic field
to derive the magnetic environment, stellar winds, and particle flux
permeating the interplanetary medium around {κ }1 Cet. Our
results show a closer magnetosphere and mass-loss rate of \dot{M}=9.7×
{10}-13 {M}⊙ \quad {{{yr}}}-1, I.e.,
a factor of 50 times larger than the current solar wind mass-loss rate,
resulting in a larger interaction via space weather disturbances
between the stellar wind and a hypothetical young-Earth analogue,
potentially affecting the planet’s habitability. Interaction of the
wind from the young Sun with the planetary ancient magnetic field may
have affected the young Earth and its life conditions.
Title: Could a change in magnetic field geometry cause the break in
the wind-activity relation?
Authors: Vidotto, A. A.; Donati, J. -F.; Jardine, M.; See, V.; Petit,
P.; Boisse, I.; Boro Saikia, S.; Hébrard, E.; Jeffers, S. V.; Marsden,
S. C.; Morin, J.
Bibcode: 2016MNRAS.455L..52V
Altcode: 2015arXiv150908751V
Wood et al. suggested that mass-loss rate is a function of X-ray
flux (dot{M}∝ F_x^{1.34}) for dwarf stars with Fx
≲ Fx,6 ≡ 106 erg cm-2
s-1. However, more active stars do not obey this
relation. These authors suggested that the break at Fx,6
could be caused by significant changes in magnetic field topology
that would inhibit stellar wind generation. Here, we investigate this
hypothesis by analysing the stars in Wood et al. sample that had their
surface magnetic fields reconstructed through Zeeman-Doppler Imaging
(ZDI). Although the solar-like outliers in the dot{M} - Fx
relation have higher fractional toroidal magnetic energy, we do
not find evidence of a sharp transition in magnetic topology at
Fx,6. To confirm this, further wind measurements and ZDI
observations at both sides of the break are required. As active stars
can jump between states with highly toroidal to highly poloidal fields,
we expect significant scatter in magnetic field topology to exist
for stars with Fx ≳ Fx,6. This strengthens
the importance of multi-epoch ZDI observations. Finally, we show that
there is a correlation between Fx and magnetic energy, which
implies that dot{M} - magnetic energy relation has the same qualitative
behaviour as the original dot{M} - Fx relation. No break
is seen in any of the Fx - magnetic energy relations.
Title: A maximum entropy approach to detect close-in giant planets
around active stars
Authors: Petit, P.; Donati, J. -F.; Hébrard, E.; Morin, J.; Folsom,
C. P.; Böhm, T.; Boisse, I.; Borgniet, S.; Bouvier, J.; Delfosse,
X.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Barnes, J. R.
Bibcode: 2015A&A...584A..84P
Altcode: 2015arXiv150300180P
Context. The high spot coverage of young active stars is responsible
for distortions of spectral lines that hamper the detection of
close-in planets through radial velocity methods.
Aims: We
aim to progress towards more efficient exoplanet detection around
active stars by optimizing the use of Doppler imaging in radial
velocity measurements.
Methods: We propose a simple method
to simultaneously extract a brightness map and a set of orbital
parameters through a tomographic inversion technique derived from
classical Doppler mapping. Based on the maximum entropy principle,
the underlying idea is to determine the set of orbital parameters that
minimizes the information content of the resulting Doppler map. We
carry out a set of numerical simulations to perform a preliminary
assessment of the robustness of our method, using an actual Doppler
map of the very active star HR 1099 to produce a realistic synthetic
data set for various sets of orbital parameters of a single planet in
a circular orbit.
Results: Using a simulated time series of
50 line profiles affected by a peak-to-peak activity jitter of 2.5
km s-1, in most cases we are able to recover the radial
velocity amplitude, orbital phase, and orbital period of an artificial
planet down to a radial velocity semi-amplitude of the order of the
radial velocity scatter due to the photon noise alone (about 50 m
s-1 in our case). One noticeable exception occurs when the
planetary orbit is close to co-rotation, in which case significant
biases are observed in the reconstructed radial velocity amplitude,
while the orbital period and phase remain robustly recovered.
Conclusions: The present method constitutes a very simple way to extract
orbital parameters from heavily distorted line profiles of active stars,
when more classical radial velocity detection methods generally fail. It
is easily adaptable to most existing Doppler imaging codes, paving the
way towards a systematic search for close-in planets orbiting young,
rapidly-rotating stars.
Title: The energy budget of stellar magnetic fields
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Donati, J. -F.; Folsom,
C. P.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Gregory, S. G.;
Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.;
do Nascimento, J. D.; Petit, P.; Rosén, L.; Waite, I. A.
Bibcode: 2015MNRAS.453.4301S
Altcode: 2015arXiv150801403S
Spectropolarimetric observations have been used to map stellar magnetic
fields, many of which display strong bands of azimuthal fields that
are toroidal. A number of explanations have been proposed to explain
how such fields might be generated though none are definitive. In this
paper, we examine the toroidal fields of a sample of 55 stars with
magnetic maps, with masses in the range 0.1-1.5 M⊙. We find
that the energy contained in toroidal fields has a power-law dependence
on the energy contained in poloidal fields. However the power index is
not constant across our sample, with stars less and more massive than
0.5 M⊙ having power indices of 0.72 ± 0.08 and 1.25 ±
0.06, respectively. There is some evidence that these two power laws
correspond to stars in the saturated and unsaturated regimes of the
rotation-activity relation. Additionally, our sample shows that strong
toroidal fields must be generated axisymmetrically. The latitudes at
which these bands appear depend on the stellar rotation period with
fast rotators displaying higher latitude bands than slow rotators. The
results in this paper present new constraints for future dynamo studies.
Title: Starspot Distributions on Fully Convective M Dwarfs:
Implications for Radial Velocity Planet Searches
Authors: Barnes, J. R.; Jeffers, S. V.; Jones, H. R. A.; Pavlenko,
Ya. V.; Jenkins, J. S.; Haswell, C. A.; Lohr, M. E.
Bibcode: 2015ApJ...812...42B
Altcode: 2015arXiv150905284B
Since M4.5-M9 dwarfs exhibit equatorial rotation velocities of the
order of 10 km s-1 on average, radial velocity surveys
targeting this stellar population will likely need to find methods to
effectively remove starspot jitter. We present the first high resolution
Doppler images of the M4.5 dwarf, GJ 791.2A, and the M9 dwarf, LP
944-20. The time series spectra of both objects reveal numerous line
profile distortions over the rotation period of each star, which we
interpret as starspots. The transient distortions are modeled with
spot/photosphere contrast ratios that correspond to model atmosphere
temperature differences of {T}{phot}-{T}{spot}
= 300 and 200 K. GJ 791.2A is a fully convective star with v sin i =
35.1 km s-1. Although we find more starspot structure at
high latitudes, we reconstruct spots at a range of phases and latitudes
with a mean spot filling of ∼3%. LP 944-20 is one of the brightest
known late-M dwarfs, with spectral type M9V and v sin i = 30.8 km
s-1. Its spectral time series exhibits two dominant transient
line distortions that are reconstructed as high latitude spots, while
a mean spot filling factor of only 1.5% is found. The occurrence of
low-contrast spots at predominantly high latitudes, which we see in
both targets here, is, in general, likely to be responsible for the low
amplitude photometric variability seen in late-M dwarfs. For GJ 791.2A,
the radial velocities induced by the starspot features yield an rms
velocity variability of 138 m s-1, which can be reduced by a
factor of 1.9 using our reconstructed surface brightness distributions.
Title: Coronal magnetic field and wind of an aging K-type star
Authors: Réville, Victor; Brun, Allan Sacha; Strugarek, Antoine;
Jeffers, Sandra; Folsom, Colin; Marsden, Stephen C.; Petit, Pascal
Bibcode: 2015IAUGA..2249564R
Altcode:
Created at the base of the convective envelope by a nonlinear dynamo
process, the large scale magnetic field of a star evolves with
its rotational history. Beyond the photosphere, magnetic processes
heat the corona above one million Kelvin hence driving a magnetized
wind responsible for the braking of main sequence stars. Hence a
feedback loop tie those processes. Development of Zeeman-Doppler
imaging through spectropolarimetry allows to precisely describe the
surface magnetic field of a large sample of stars. Thus the study of
the coronal structure and magnetic field with age, magnetochoronology,
has developed to extend and complete gyrochronology. We propose a study
of the corona and the wind of a sample of K-type stars of different
age to follow the evolution of its properties from 20 Myr to 8 Gyr
thanks to a set of 3D MHD simulations with the PLUTO code constrained
by spectropolarimetric maps of the surface magnetic field obtained
by the BCool consortium. To perform those simulations we developed a
coherent framework to assess various stellar parameters such as the
equilibrium coronal temperature driving the wind. Those assumptions
have consequences on UV emissions, wind terminal speed and mass loss
that impact planetary systems that could potentially host life.
Title: Hunt for magnetic cycles in solar-type stars using
spectropolarimetric observations
Authors: Boro Saikia, Sudeshna; Jeffers, Sandra; Petit, Pascal;
Marsden, Stephen
Bibcode: 2015IAUGA..2256700B
Altcode:
Magnetic cycles in solar-type stars detected using spectropolarimetric
observations together with chromospheric activity cycles, provide
important insights into magnetic field regeneration and amplification
in stars other than the Sun. We investigate the variability of the
large-scale magnetic field of two solar-type stars 61 Cyg A and HN
Peg using spectropolarimetric observations. Zeeman Doppler imaging
is used to reconstruct the large-scale magnetic field over multiple
epochs to understand how the large-scale field varies with chromospheric
activity cycle. We report the first detection of polarity reversals of
the large-scale field in phase with its chromospheric activity cycle
for the K5V dwarf 61 Cyg A. The magnetic geometry of the G0V dwarf HN
Peg however do not exhibit any polarity reversal, but exhibits a very
rapidly varying magnetic field with strong azimuthal component.
Title: Long-term evolution of the large-scale magnetic fields of
cool stars
Authors: Vidotto, Aline; Gregory, Scott; Jardine, Moira; Donati,
Jean-Francois; Petit, Pascal; Morin, Julien; Folsom, Colin; Bouvier,
Jerome; Cameron, Andrew; Hussain, Gaitee; Marsden, Stephen; Waite,
Ian; Fares, Rim; Jeffers, Sandra; do Nascimento, Jose, Jr.
Bibcode: 2015IAUGA..2232877V
Altcode:
We investigate how the large-scale surface magnetic fields of cool
dwarf stars, reconstructed using the Zeeman-Doppler Imaging (ZDI)
technique, vary with age, rotation period, Rossby number and X-ray
emission. Our sample consists of 104 magnetic maps of 76 stars,
from accreting pre-main sequence to main-sequence objects, spanning
ages from ~1 Myr to ~10 Gyr. For non-accreting dwarfs we empirically
find that the unsigned average large-scale surface magnetic field
relates to age as age-0.65. This relation has a similar
power dependency to that identified in the seminal work of Skumanich
(1972). We also find in our data evidence for a linear-type dynamo, in
which the surface field is linearly dependent on the rotation rate. The
trends we find for large-scale stellar magnetism from ZDI studies are
consistent with the trends found from Zeeman broadening measurements,
which are sensitive to the unsigned large- and small-scale magnetic
field. These similarities indicate that the fields recovered from
both techniques are coupled to each other, suggesting that small-
and large-scale fields could share the same dynamo field generation
processes. Our results are relevant for investigations of rotational
evolution of low-mass stars and give important observational constraints
for stellar dynamo studies.
Title: CARMENES input catalogue of M dwarfs. I. Low-resolution
spectroscopy with CAFOS
Authors: Alonso-Floriano, F. J.; Morales, J. C.; Caballero, J. A.;
Montes, D.; Klutsch, A.; Mundt, R.; Cortés-Contreras, M.; Ribas,
I.; Reiners, A.; Amado, P. J.; Quirrenbach, A.; Jeffers, S. V.
Bibcode: 2015A&A...577A.128A
Altcode: 2015arXiv150207580A
Context. CARMENES is a stabilised, high-resolution, double-channel
spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed
for radial-velocity surveys of M dwarfs with potentially habitable
Earth-mass planets.
Aims: We prepare a list of the brightest,
single M dwarfs in each spectral subtype observable from the northern
hemisphere, from which we will select the best planet-hunting targets
for CARMENES.
Methods: In this first paper on the preparation
of our input catalogue, we compiled a large amount of public data and
collected low-resolution optical spectroscopy with CAFOS at the 2.2
m Calar Alto telescope for 753 stars. We derived accurate spectral
types using a dense grid of standard stars, a double least-squares
minimisation technique, and 31 spectral indices previously defined by
other authors. Additionally, we quantified surface gravity, metallicity,
and chromospheric activity for all the stars in our sample.
Results: We calculated spectral types for all 753 stars, of which
305 are new and 448 are revised. We measured pseudo-equivalent
widths of Hα for all the stars in our sample, concluded that
chromospheric activity does not affect spectral typing from our
indices, and tabulated 49 stars that had been reported to be young
stars in open clusters, moving groups, and stellar associations. Of
the 753 stars, two are new subdwarf candidates, three are T Tauri
stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many
of the 261 investigated dwarfs in the range M4.0-8.0 V are among the
brightest stars known in their spectral subtype.
Conclusions:
This collection of low-resolution spectroscopic data serves as
a candidate target list for the CARMENES survey and can be highly
valuable for other radial-velocity surveys of M dwarfs and for studies
of cool dwarfs in the solar neighbourhood. Full Tables A.1,
A.2, and A.3 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/577/A128
Title: Magnetic fields on young, moderately rotating Sun-like stars -
I. HD 35296 and HD 29615
Authors: Waite, I. A.; Marsden, S. C.; Carter, B. D.; Petit, P.;
Donati, J. -F.; Jeffers, S. V.; Boro Saikia, S.
Bibcode: 2015MNRAS.449....8W
Altcode: 2015arXiv150205788W
Observations of the magnetic fields of young solar-type stars provide
a way to investigate the signatures of their magnetic activity and
dynamos. Spectropolarimetry enables the study of these stellar magnetic
fields and was thus employed at the Télescope Bernard Lyot and the
Anglo-Australian Telescope to investigate two moderately rotating
young Sun-like stars, namely HD 35296 (V119 Tau, HIP 25278) and
HD 29615 (HIP 21632). The results indicate that both stars display
rotational variation in chromospheric indices consistent with their
spot activity, with variations indicating a probable long-term
cyclic period for HD 35296. Additionally, both stars have complex,
and evolving, large-scale surface magnetic fields with a significant
toroidal component. High levels of surface differential rotation were
measured for both stars. For the F8V star HD 35296 a rotational shear
of ΔΩ = 0.22^{+0.04}_{-0.02} rad d- 1 was derived from the
observed magnetic profiles. For the G3V star HD 29615, the magnetic
features indicate a rotational shear of ΔΩ = 0.48_{-0.12}^{+0.11}
rad d- 1, while the spot features, with a distinctive polar
spot, provide a much lower value of ΔΩ of 0.07_{-0.03}^{+0.10} rad
d- 1. Such a significant discrepancy in shear values between
spot and magnetic features for HD 29615 is an extreme example of the
variation observed for other lower mass stars. From the extensive and
persistent azimuthal field observed for both targets, it is concluded
that a distributed dynamo operates in these moderately rotating Sun-like
stars, in marked contrast to the Sun's interface-layer dynamo.
Title: CARMENES science preparation. High-resolution spectroscopy
of M dwarfs
Authors: Montes, D.; Caballero, J. A.; Jeffers, S.; Alonso-Floriano,
F. J.; Mundt, R.; CARMENES Consortium; del Burgo, Carlos
Bibcode: 2015hsa8.conf..605M
Altcode:
To ensure an efficient use of CARMENES observing time, and the
highest chances of success, it is necessary first to select the most
promising targets. To achieve this, we are observing 500 M dwarfs
at high-resolution (R = 30,000-48,000), from which we determine the
projected rotational velocity vsin{i} with an accuracy better than
0.5-0.2 km/s and radial-velocity stability better than 0.2-0.1 km/s. Our
aim is to have at least two spectra at different epochs of the final
300 CARMENES targets. Our observations with FEROS at ESO/MPG 2.2 m
La Silla, CAFE at 2.2 m Calar Alto and HRS at Hobby Eberly Telescope
allow us to identify single- and double-line spectroscopic binaries
and, especially, fast rotators, which should be discarded from the
target list for exoplanet searches. Here we present preliminary results.
Title: VizieR Online Data Catalog: BCool survey of solar-type stars
(Marsden+ 2014)
Authors: Marsden, S. C.; Petit, P.; Jeffers, S. V.; Morin, J.; Fares,
R.; Reiners, A.; Do Nascimento, J. -D., Jr.; Auriere, M.; Bouvier,
J.; Carter, B. D.; Catala, C.; Dintrans, B.; Donati, J. -F.; Gastine,
T.; Jardine, M.; Konstantinova-Antova, R.; Lanoux, J.; Lignieres, F.;
Morgenthaler, A.; Ramirez-Velez, J. C.; Theado, S.; Van Grootel, V.;
BCool Collaboration
Bibcode: 2015yCat..74443517M
Altcode:
The goal of the BCool spectropolarimetric survey is to observe as many
of the bright (V<~9.0) solar-type stars as possible to further our
understanding of the magnetic activity of cool stars. In this first
paper, we present the spectropolarimetric snapshots of 170 solar-type
stars that we have observed starting in 2006 until 2013 as part of
the BCool survey. (5 data files).
Title: Analysis of combined radial velocities and activity of BD+20
1790: evidence supporting the existence of a planetary companion
Authors: Hernán-Obispo, M.; Tuomi, M.; Gálvez-Ortiz, M. C.; Golovin,
A.; Barnes, J. R.; Jones, H. R. A.; Kane, S. R.; Pinfield, D.; Jenkins,
J. S.; Petit, P.; Anglada-Escudé, G.; Marsden, S. C.; Catalán, S.;
Jeffers, S. V.; de Castro, E.; Cornide, M.; Garcés, A.; Jones, M. I.;
Gorlova, N.; Andreev, M.
Bibcode: 2015A&A...576A..66H
Altcode: 2015arXiv150205223H
Context. In a previous paper we reported a planetary companion to the
young and very active K5Ve star BD+20 1790. We found that this star
has a high level of stellar activity (log Rprime_HK =-3.7)
that manifests in a plethora of phenomena (starspots, prominences,
plages, large flares). Based on a careful study of these activity
features and a deep discussion and analysis of the effects of the
stellar activity on the radial velocity measurements, we demonstrated
that the presence of a planet provided the best explanation for the
radial velocity variations and all the peculiarities of this star. The
orbital solution resulted in a close-in massive planet with a period
of 7.78 days. However, a paper by Figueira et al. (2010, A&A, 513,
L8) questioned the evidence for the planetary companion.
Aims:
This paper aims to more rigorously assess the nature of the radial
velocity measurements with an expanded data set and new methods
of analysis.
Methods: We have employed Bayesian methods to
simultaneously analyse the radial velocity and activity measurements
based on a combined data set that includes new and previously published
observations.
Results: We conclude that the Bayesian analysis and
the new activity study support the presence of a planetary companion
to BD+20 1790. A new orbital solution is presented, after removing
the two main contributions of stellar jitter, one that varies with
the photometric period (2.8 days) and another that varies with the
synodic period of the star-planet system (4.36 days). We present a new
method to determine these jitter components, considering them as second
and third signals in the system. A discussion on possible star-planet
interaction is included, based on the Bayesian analysis of the activity
indices, which indicates that they modulate with the synodic period. We
propose two different sources for flare events in this system: one
related to the geometry of the system and the relative movement of
the star and planet, and a second one purely stochastic source that
is related to the evolution of stellar surface active regions. Also,
we observe for the first time the magnetic field of the star, from
spectropolarimetric data. See Acknowledgements.Table of the
radial velocities is 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/576/A66
Title: VizieR Online Data Catalog: CARMENES input catalogue of M
dwarfs. I (Alonso-Floriano+, 2015)
Authors: Alonso-Floriano, F. J.; Morales, J. C.; Caballero, J. A.;
Montes, D.; Klutsch, A.; Mundt, R.; Cortes-Contreras, M.; Ribas, I.;
Reiners, A.; Amado, P. J.; Quirrenbach, A.; Jeffers, S. V.
Bibcode: 2015yCat..35770128A
Altcode:
List of 753 late-type stars, mostly M dwarfs, observed with the
low-resolution optical spectrograph CAFOS at the 2.2m Calar Alto
telescope for the preparation of the CARMENES input catalogue
(http://carmenes.caha.es/). We provide basic data, observation
parameters, spectral-typing indices, zeta metallicity index, Hα
pseudo-equivalent width, spectral type from the literature, and our
accurate adopted spectral type. (4 data files).
Title: VizieR Online Data Catalog: BD+20 1790 radial velocities and
photometry (Hernan-Obispo+, 2015)
Authors: Hernan-Obispo, M.; Tuomi, M.; Galvez-Ortiz, M. C.; Golovin,
A.; Barnes, J. R.; Jones, H. R. A.; Kane, S. R.; Pinfield, D.; Jenkins,
J. S.; Petit, P.; Anglada-Escude, G.; Marsden, S. C.; Catalan, S.;
Jeffers, S. V.; de Castro, E.; Cornide, M.; Garces, A.; Jones, M. I.;
Gorlova, N.; Andreev, M.
Bibcode: 2015yCat..35760066H
Altcode: 2015yCat..35769066H
This paper presents the simultaneously Bayesian analysis of the
radial velocity and activity indices for the K5Ve star BD+20 1790,
that was proposed to host a close-in massive planet by Hernan-Obispo
(2010A&A...512A..45H, Cat. J/A+A/512/A45). We present a new
orbital solution after removing the two main contributions of the
stellar jitter, one related with the photometric period (2.8 days) and
a second one related with the synodic period of the star+planet system
(4.26 days). The radial velocities listed are nightly averaged,
and were taked using different spectrographs. The photometric
table shows only the data taken at Terskol Observatory. Photometric
data from ASAS (All Sky Automated Survey) of BD+20 1790 can be obtained
at http://www.astroew.edu.pl/asas (2 data files).
Title: Variable magnetic field geometry of the young sun HN Pegasi
(HD 206860)
Authors: Boro Saikia, S.; Jeffers, S. V.; Petit, P.; Marsden, S.;
Morin, J.; Folsom, C. P.
Bibcode: 2015A&A...573A..17B
Altcode: 2014arXiv1410.8307B
Context. The large-scale magnetic field of solar-type stars
reconstructed from their spectropolarimetric observations provide
important insight into their underlying dynamo processes.
Aims:
We aim to investigate the temporal variability of the large-scale
surface magnetic field and chromospheric activity of a young solar
analogue, the G0 dwarf HN Peg.
Methods: The large-scale surface
magnetic field topology is reconstructed using Zeeman Doppler imaging
at six observational epochs covering seven years. We also investigated
the chromospheric activity variations by measuring the flux in the
line cores of the three chromospheric activity indicators: Ca II HK,
Hα, and the Ca II IRT lines.
Results: The magnetic topology of
HN Peg shows a complex and variable geometry. While the radial field
exhibits a stable positive polarity magnetic region at the poles at
each observational epoch, the azimuthal field is strongly variable
in strength, where a strong band of positive polarity magnetic field
is present at equatorial latitudes. This field disappears during the
middle of our timespan, reappearing again during the last two epochs of
observations. The mean magnetic field derived from the magnetic maps
also follow a similar trend to the toroidal field, with the field
strength at a minimum in epoch 2009.54. Summing the line of sight
magnetic field over the visible surface at each observation, HN Peg
exhibits a weak longitudinal magnetic field (Bl) ranging
from -14 G to 13 G, with no significant long-term trend, although
there is significant rotational variability within each epoch. Those
chromospheric activity indicators exhibit more long-term variations over
the time span of observations, where the minimal is observed in Epoch
2008.71. Tables 3 and 4 are available in electronic form at http://www.aanda.org
Title: Preparation of the CARMENES Input Catalogue: Low- and
High-resolution Spectroscopy of M dwarfs
Authors: Alonso-Floriano, F. J.; Montes, D.; Caballero, J. A.;
Klutsch, A.; Jeffers, S.; Reiners, A.; Zechmeister, M.; Lamert, A.;
Passegger, V. M.; Mundt, R.; Amado, P. J.; Berdinas, Z. M.; Casal, E.;
Cortés-Contreras, M.; Morales, J. C.; Ribas, I.; Rodríguez-López,
C.; Quirrenbach, A.
Bibcode: 2015csss...18..796A
Altcode:
The identification of the most promising targets for exoplanet hunting
is a crucial first step to ensure an efficient use of the CARMENES
guaranteed time. To achieve this, we obtained low-resolution (R ∼
1500) spectra of 752 M (and late K) dwarfs mostly fainter than J =
9 mag with CAFOS. For all of them, we derived spectral types with 0.5
subtypes accuracy. We also studied metallicity and surface gravity
through spectral indices, and activity from pEW(Hα). Next, we observed
over 600 M dwarfs at higher resolution (R = 30 000-48 000) with FEROS,
CAFE and HRS. We determined rotational velocities, v sin{i} (±0.2-0.5
km s^{-1}), and radial velocities, V_r (±0.1-0.2 km s^{-1}), of the
observed stars. From our observations, we identified high-activity,
low-metallicity and low-gravity stars, single- and double-lined
spectroscopic binaries and, specially, fast rotators, which should be
discarded from any target list for exoplanet searches. Here we present
preliminary results.
Title: Surprising detection of an equatorial dust lane on the AGB
star IRC+10216
Authors: Jeffers, S. V.; Min, M.; Waters, L. B. F. M.; Canovas,
H.; Pols, O. R.; Rodenhuis, M.; de Juan Ovelar, M.; Keller, C. U.;
Decin, L.
Bibcode: 2014A&A...572A...3J
Altcode: 2014arXiv1412.5063J
Aims: Understanding the formation of planetary nebulae remains
elusive because in the preceding asymptotic giant branch (AGB)
phase these stars are heavily enshrouded in an optically thick dusty
envelope.
Methods: To further understand the morphology of
the circumstellar environments of AGB stars we observe the closest
carbon-rich AGB star IRC+10216 in scattered light.
Results:
When imaged in scattered light at optical wavelengths, IRC+10216
surprisingly shows a narrow equatorial density enhancement, in contrast
to the large-scale spherical rings that have been imaged much further
out. We use radiative transfer models to interpret this structure
in terms of two models: firstly, an equatorial density enhancement,
commonly observed in the more evolved post-AGB stars, and secondly,
in terms of a dust rings model, where a local enhancement of mass-loss
creates a spiral ring as the star rotates.
Conclusions: We
conclude that both models can be used to reproduce the dark lane in
the scattered light images, which is caused by an equatorially density
enhancement formed by dense dust rather than a bipolar outflow as
previously thought. We are unable to place constraints on the formation
of the equatorial density enhancement by a binary system. Final
reduced images (FITS) are 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/572/A3Based
on observations made with the William Herschel Telescope operated on the
island of La Palma by the Isaac Newton Group in the Spanish Observatorio
del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
Title: A BCool magnetic snapshot survey of solar-type stars
Authors: Marsden, S. C.; Petit, P.; Jeffers, S. V.; Morin, J.; Fares,
R.; Reiners, A.; do Nascimento, J. -D.; Aurière, M.; Bouvier, J.;
Carter, B. D.; Catala, C.; Dintrans, B.; Donati, J. -F.; Gastine, T.;
Jardine, M.; Konstantinova-Antova, R.; Lanoux, J.; Lignières, F.;
Morgenthaler, A.; Ramìrez-Vèlez, J. C.; Théado, S.; Van Grootel,
V.; BCool Collaboration
Bibcode: 2014MNRAS.444.3517M
Altcode: 2013arXiv1311.3374M
We present the results of a major high-resolution spectropolarimetric
BCool project magnetic survey of 170 solar-type stars. Surface
magnetic fields were detected on 67 stars, with 21 classified as
mature solar-type stars, a result that increases by a factor of 4 the
number of mature solar-type stars on which magnetic fields have been
observed. In addition, a magnetic field was detected for 3 out of 18
of the subgiant stars surveyed. For the population of K-dwarfs, the
mean value of |Bl| (|Bl|mean) was also
found to be higher (5.7 G) than |Bl|mean measured
for the G-dwarfs (3.2 G) and the F-dwarfs (3.3 G). For the sample as
a whole, |Bl|mean increases with rotation rate
and decreases with age, and the upper envelope for |Bl|
correlates well with the observed chromospheric emission. Stars with a
chromospheric S-index greater than about 0.2 show a high magnetic field
detection rate and so offer optimal targets for future studies. This
survey constitutes the most extensive spectropolarimetric survey of
cool stars undertaken to date, and suggests that it is feasible to
pursue magnetic mapping of a wide range of moderately active solar-type
stars to improve our understanding of their surface fields and dynamos.
Title: The effects of stellar winds on the magnetospheres and
potential habitability of exoplanets
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Petit, P.; Marsden,
S. C.; Jeffers, S. V.; do Nascimento, J. D.
Bibcode: 2014A&A...570A..99S
Altcode: 2014arXiv1409.1237S
Context. The principle definition of habitability for exoplanets is
whether they can sustain liquid water on their surfaces, i.e. that they
orbit within the habitable zone. However, the planet's magnetosphere
should also be considered, since without it, an exoplanet's atmosphere
may be eroded away by stellar winds.
Aims: The aim of this
paper is to investigate magnetospheric protection of a planet from
the effects of stellar winds from solar-mass stars.
Methods:
We study hypothetical Earth-like exoplanets orbiting in the host
star's habitable zone for a sample of 124 solar-mass stars. These are
targets that have been observed by the Bcool Collaboration. Using
two wind models, we calculate the magnetospheric extent of each
exoplanet. These wind models are computationally inexpensive and
allow the community to quickly estimate the magnetospheric size of
magnetised Earth-analogues orbiting cool stars.
Results: Most
of the simulated planets in our sample can maintain a magnetosphere
of ~5 Earth radii or larger. This suggests that magnetised Earth
analogues in the habitable zones of solar analogues are able to
protect their atmospheres and is in contrast to planets around young
active M dwarfs. In general, we find that Earth-analogues around
solar-type stars, of age 1.5 Gyr or older, can maintain at least a
Paleoarchean Earth sized magnetosphere. Our results indicate that
planets around 0.6-0.8 solar-mass stars on the low activity side of
the Vaughan-Preston gap are the optimum observing targets for habitable
Earth analogues. Appendix A is available in electronic form at http://www.aanda.org
Title: ɛ Eridani: an active K dwarf and a planet hosting star?. The
variability of its large-scale magnetic field topology
Authors: Jeffers, S. V.; Petit, P.; Marsden, S. C.; Morin, J.; Donati,
J. -F.; Folsom, C. P.
Bibcode: 2014A&A...569A..79J
Altcode:
The young K-dwarf ɛ Eridani is an example of a young active
planet hosting star that has shown over long-term monitoring of
its chromospheric emission to exhibit cyclic magnetic activity. In
this paper, we investigate how ɛ Eridani's large-scale magnetic
field geometry evolves over the timescale of its S-index cycle using
spectropolarimetric observations and the technique of Zeeman-Doppler
imaging. Our observations comprise six epochs secured over a time period
of nearly seven years, with each almost yearly observational epoch
showing a dramatic change in the large-scale magnetic field topology,
with no stable regions. The poloidal field varies from strongly dipolar
to mono-polar and the toroidal field is non-existent to begin with and
then emerges to dominate the magnetic field energy before disappearing
and re-emerging again. A potential cycle is detected in the poloidal
field, but further observations are needed to confirm this. Based
on observations made with Telescope Bernard Lyot (TBL, Pic du Midi,
France) of the Observatoire Midi-Pyrenees, which is operated by the
Institut National des Sciences de l'Univers of the Centre National de
la Recherche Scientifique (CNRS) of France.
Title: Two planets around Kapteyn's star: a cold and a temperate
super-Earth orbiting the nearest halo red dwarf.
Authors: Anglada-Escude, G.; Arriagada, P.; Tuomi, M.; Zechmeister,
M.; Jenkins, J. S.; Ofir, A.; Dreizler, S.; Gerlach, E.; Marvin,
C. J.; Reiners, A.; Jeffers, S. V.; Butler, R. P.; Vogt, S. S.; Amado,
P. J.; Rodriguez-Lopez, C.; Berdinas, Z. M.; Morin, J.; Crane, J. D.;
Shectman, S. A.; Thompson, I. B.; Diaz, M.; Rivera, E.; Sarmiento,
L. F.; Jones, H. R. A.
Bibcode: 2014MNRAS.443L..89A
Altcode: 2014arXiv1406.0818A
Exoplanets of a few Earth masses can be now detected around
nearby low-mass stars using Doppler spectroscopy. In this Letter,
we investigate the radial velocity variations of Kapteyn's star,
which is both a sub-dwarf M-star and the nearest halo object to the
Sun. The observations comprise archival and new HARPS (High Accuracy
Radial velocity Planet Searcher), High Resolution Echelle Spectrometer
(HIRES) and Planet Finder Spectrograph (PFS) Doppler measurements. Two
Doppler signals are detected at periods of 48 and 120 d using likelihood
periodograms and a Bayesian analysis of the data. Using the same
techniques, the activity indices and archival All Sky Automated
Survey (ASAS-3) photometry show evidence for low-level activity
periodicities of the order of several hundred days. However, there
are no significant correlations with the radial velocity variations on
the same time-scales. The inclusion of planetary Keplerian signals in
the model results in levels of correlated and excess white noise that
are remarkably low compared to younger G, K and M dwarfs. We conclude
that Kapteyn's star is most probably orbited by two super-Earth mass
planets, one of which is orbiting in its circumstellar habitable zone,
becoming the oldest potentially habitable planet known to date. The
presence and long-term survival of a planetary system seem a remarkable
feat given the peculiar origin and kinematic history of Kapteyn's
star. The detection of super-Earth mass planets around halo stars
provides important insights into planet-formation processes in the
early days of the Milky Way.
Title: On the effects of stellar winds on exoplanetary magnetospheres
Authors: See, V.; Jardine, M.; Vidotto, A. A.; Petit, P.; Marsden,
S. C.; Jeffers, S. V.
Bibcode: 2014IAUS..302..251S
Altcode:
The habitable zone is the range of orbital distances from a host
star in which an exoplanet would have a surface temperature suitable
for maintaining liquid water. This makes the orbital distance of
exoplanets an important variable when searching for extra-solar Earth
analogues. However, the orbital distance is not the only important
factor determining whether an exoplanet is potentially suitable for
life. The ability of an exoplanet to retain an atmosphere is also
vital since it helps regulate surface temperatures. One mechanism by
which a planetary atmosphere can be lost is erosion due to a strong
stellar wind from the host star. The presence of a magnetosphere
can help to shield a planetary atmosphere from this process. Using a
simple stellar wind model, we present the impact that stellar winds
might have on magnetospheric sizes of exoplanets. This is done with
the aim of further constraining the parameter space in which we look
for extra-solar Earth analogues.
Title: A Bcool spectropolarimetric survey of over 150 solar-type stars
Authors: Marsden, Stephen; Petit, Pascal; Jeffers, Sandra; do
Nascimento, Jose-Dias; Carter, Bradley; Brown, Carolyn
Bibcode: 2014IAUS..302..138M
Altcode: 2013arXiv1310.6507M
As part of the Bcool project, over 150 solar-type stars chosen mainly
from planet search databases have been observed between 2006 and 2013
using the NARVAL and ESPaDOnS spectropolarimeters on the Telescope
Bernard Lyot (Pic du Midi, France) and the Canada France Hawaii
Telescope (Mauna Kea, USA), respectively. These single ``snapshot''
observations have been used to detect the presence of magnetic fields
on 40% of our sample, with the highest detection rates occurring
for the youngest stars. From our observations we have determined the
mean surface longitudinal field (or an upper limit for stars without
detections) and the chromospheric surface fluxes, and find that the
upper envelope of the absolute value of the mean surface longitudinal
field is directly correlated to the chromospheric emission from the
star and increases with rotation rate and decreases with age.
Title: High-resolution spectropolarimetry of κ Cet: A proxy for
the young Sun
Authors: do Nascimento, J. D.; Petit, P.; Castro, M.; de Mello,
G. F. Porto; Jeffers, S. V.; Marsden, S. C.; Ribas, I.; Guinan,
E.; Guinan
Bibcode: 2014IAUS..302..142D
Altcode: 2013arXiv1310.7620D
κ1 Cet (HD 20630, HIP 15457, d = 9.16 pc, V = 4.84)
is a dwarf star approximately 30 light-years away in the equatorial
constellation of Cetus. Among the solar proxies studied in the Sun in
Time, κ1 Cet stands out as potentially having a mass very
close to solar and a young age. On this study, we monitored the magnetic
field and the chromospheric activity from the Ca II H & K lines of
κ1 Cet. We used the technique of Least-Square-Deconvolution
(LSD, Donati et al. 1997) by simultaneously extracting the information
contained in all 8,000 photospheric lines of the echelogram (for
a linelist matching an atmospheric model of spectral type K1). To
reconstruct a reliable magnetic map and characterize the surface
differential rotation of κ1 Cet we used 14 exposures spread
over 2 months, in order to cover at least two rotational cycles (Prot
~9.2 days). The Least Square deconvolution (LSD) technique was applied
to detect the Zeeman signature of the magnetic field in each of our
14 observations and to measure its longitudinal component. In order
to reconstruct the magnetic field geometry of κ1 Cet,
we applied the Zeeman Doppler Imaging (ZDI) inversion method. ZDI
revealed a structure in the radial magnetic field consisting of a
polar magnetic spot. On this study, we present the fisrt look results
of a high-resolution spectropolarimetric campaign to characterize the
activity and the magnetic fields of this young solar proxy.
Title: The large scale magnetic field of the G0 dwarf HD 206860
(HN Peg)
Authors: Saikia, Sudeshna Boro; Jeffers, Sandra V.; Petit, Pascal;
Marsden, Stephen; Morin, Julien; Reiners, Ansgar; Reiners
Bibcode: 2014IAUS..302..146S
Altcode:
HD 206860 is a young planet (HN Peg b) hosting star of spectral type G0V
and it has a potential debris disk around it. In this work we measure
the longitudinal magnetic field of HD 206860 using spectropolarimetric
data and we measure the chromospheric activity using Ca II H&K,
H-alpha and Ca II infrared triplet lines.
Title: CARMENES instrument overview
Authors: Quirrenbach, A.; Amado, P. J.; Caballero, J. A.; Mundt,
R.; Reiners, A.; Ribas, I.; Seifert, W.; Abril, M.; Aceituno, J.;
Alonso-Floriano, F. J.; Ammler-von Eiff, M.; Antona Jiménez, R.;
Anwand-Heerwart, H.; Azzaro, M.; Bauer, F.; Barrado, D.; Becerril, S.;
Béjar, V. J. S.; Benítez, D.; Berdiñas, Z. M.; Cárdenas, M. C.;
Casal, E.; Claret, A.; Colomé, J.; Cortés-Contreras, M.; Czesla,
S.; Doellinger, M.; Dreizler, S.; Feiz, C.; Fernández, M.; Galadí,
D.; Gálvez-Ortiz, M. C.; García-Piquer, A.; García-Vargas, M. L.;
Garrido, R.; Gesa, L.; Gómez Galera, V.; González Álvarez, E.;
González Hernández, J. I.; Grözinger, U.; Guàrdia, J.; Guenther,
E. W.; de Guindos, E.; Gutiérrez-Soto, J.; Hagen, H. -J.; Hatzes,
A. P.; Hauschildt, P. H.; Helmling, J.; Henning, T.; Hermann, D.;
Hernández Castaño, L.; Herrero, E.; Hidalgo, D.; Holgado, G.;
Huber, A.; Huber, K. F.; Jeffers, S.; Joergens, V.; de Juan, E.;
Kehr, M.; Klein, R.; Kürster, M.; Lamert, A.; Lalitha, S.; Laun,
W.; Lemke, U.; Lenzen, R.; López del Fresno, Mauro; López Martí,
B.; López-Santiago, J.; Mall, U.; Mandel, H.; Martín, E. L.;
Martín-Ruiz, S.; Martínez-Rodríguez, H.; Marvin, C. J.; Mathar,
R. J.; Mirabet, E.; Montes, D.; Morales Muñoz, R.; Moya, A.; Naranjo,
V.; Ofir, A.; Oreiro, R.; Pallé, E.; Panduro, J.; Passegger, V. -M.;
Pérez-Calpena, A.; Pérez Medialdea, D.; Perger, M.; Pluto, M.;
Ramón, A.; Rebolo, R.; Redondo, P.; Reffert, S.; Reinhardt, S.; Rhode,
P.; Rix, H. -W.; Rodler, F.; Rodríguez, E.; Rodríguez-López, C.;
Rodríguez-Pérez, E.; Rohloff, R. -R.; Rosich, A.; Sánchez-Blanco,
E.; Sánchez Carrasco, M. A.; Sanz-Forcada, J.; Sarmiento, L. F.;
Schäfer, S.; Schiller, J.; Schmidt, C.; Schmitt, J. H. M. M.; Solano,
E.; Stahl, O.; Storz, C.; Stürmer, J.; Suárez, J. C.; Ulbrich,
R. G.; Veredas, G.; Wagner, K.; Winkler, J.; Zapatero Osorio, M. R.;
Zechmeister, M.; Abellán de Paco, F. J.; Anglada-Escudé, G.; del
Burgo, C.; Klutsch, A.; Lizon, J. L.; López-Morales, M.; Morales,
J. C.; Perryman, M. A. C.; Tulloch, S. M.; Xu, W.
Bibcode: 2014SPIE.9147E..1FQ
Altcode:
This paper gives an overview of the CARMENES instrument and of the
survey that will be carried out with it during the first years of
operation. CARMENES (Calar Alto high-Resolution search for M dwarfs
with Exoearths with Near-infrared and optical Echelle Spectrographs)
is a next-generation radial-velocity instrument under construction
for the 3.5m telescope at the Calar Alto Observatory by a consortium
of eleven Spanish and German institutions. The scientific goal of the
project is conducting a 600-night exoplanet survey targeting ~ 300 M
dwarfs with the completed instrument. The CARMENES instrument consists
of two separate echelle spectrographs covering the wavelength range
from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by
fibers from the Cassegrain focus of the telescope. The spectrographs
are housed in vacuum tanks providing the temperature-stabilized
environments necessary to enable a 1 m/s radial velocity precision
employing a simultaneous calibration with an emission-line lamp
or with a Fabry-Perot etalon. For mid-M to late-M spectral types,
the wavelength range around 1.0 μm (Y band) is the most important
wavelength region for radial velocity work. Therefore, the efficiency
of CARMENES has been optimized in this range. The CARMENES instrument
consists of two spectrographs, one equipped with a 4k x 4k pixel CCD
for the range 0.55 - 1.05 μm, and one with two 2k x 2k pixel HgCdTe
detectors for the range from 0.95 - 1.7μm. Each spectrograph will
be coupled to the 3.5m telescope with two optical fibers, one for
the target, and one for calibration light. The front end contains a
dichroic beam splitter and an atmospheric dispersion corrector, to
feed the light into the fibers leading to the spectrographs. Guiding
is performed with a separate camera; on-axis as well as off-axis
guiding modes are implemented. Fibers with octagonal cross-section
are employed to ensure good stability of the output in the presence
of residual guiding errors. The fibers are continually actuated to
reduce modal noise. The spectrographs are mounted on benches inside
vacuum tanks located in the coudé laboratory of the 3.5m dome. Each
vacuum tank is equipped with a temperature stabilization system
capable of keeping the temperature constant to within +/-0.01°C
over 24 hours. The visible-light spectrograph will be operated near
room temperature, while the near-IR spectrograph will be cooled to
~ 140 K. The CARMENES instrument passed its final design review in
February 2013. The MAIV phase is currently ongoing. First tests at
the telescope are scheduled for early 2015. Completion of the full
instrument is planned for the fall of 2015. At least 600 useable
nights have been allocated at the Calar Alto 3.5m Telescope for the
CARMENES survey in the time frame until 2018. A data base of M stars
(dubbed CARMENCITA) has been compiled from which the CARMENES sample
can be selected. CARMENCITA contains information on all relevant
properties of the potential targets. Dedicated imaging, photometric,
and spectroscopic observations are underway to provide crucial data
on these stars that are not available in the literature.
Title: VizieR Online Data Catalog: PolarBase catalogue of stellar
spectra (Petit+, 2014)
Authors: Petit, P.; Louge, T.; Theado, S.; Paletou, F.; Manset, N.;
Morin, J.; Marsden, S. C.; Jeffers, S. V.
Bibcode: 2014yCat..61260469P
Altcode:
We list the stellar spectroscopic and spectropolarimetric observations
available in the PolarBase data base. For each star equatorial
coordinates, first Julian date of observation, last Julian date
of observation, number of observations are given, and a detection
diagnosis of polarized signatures (in cross-correlated pseudo-line
profiles) are given. (1 data file).
Title: Stellar magnetism: empirical trends with age and rotation
Authors: Vidotto, A. A.; Gregory, S. G.; Jardine, M.; Donati, J. F.;
Petit, P.; Morin, J.; Folsom, C. P.; Bouvier, J.; Cameron, A. C.;
Hussain, G.; Marsden, S.; Waite, I. A.; Fares, R.; Jeffers, S.;
do Nascimento, J. D.
Bibcode: 2014MNRAS.441.2361V
Altcode: 2014arXiv1404.2733V
We investigate how the observed large-scale surface magnetic
fields of low-mass stars (∼0.1-2 M⊙), reconstructed
through Zeeman-Doppler imaging, vary with age t, rotation and X-ray
emission. Our sample consists of 104 magnetic maps of 73 stars,
from accreting pre-main sequence to main-sequence objects (1 Myr
≲ t ≲ 10 Gyr). For non-accreting dwarfs we empirically find
that the unsigned average large-scale surface field is related to
age as t-0.655 ± 0.045. This relation has a similar
dependence to that identified by Skumanich, used as the basis for
gyrochronology. Likewise, our relation could be used as an age-dating
method (`magnetochronology'). The trends with rotation we find for the
large-scale stellar magnetism are consistent with the trends found from
Zeeman broadening measurements (sensitive to large- and small-scale
fields). These similarities indicate that the fields recovered from
both techniques are coupled to each other, suggesting that small-
and large-scale fields could share the same dynamo field generation
processes. For the accreting objects, fewer statistically significant
relations are found, with one being a correlation between the unsigned
magnetic flux and rotation period. We attribute this to a signature
of star-disc interaction, rather than being driven by the dynamo.
Title: VizieR Online Data Catalog: Kapteyn's star spectroscopic
measurements (Anglada-Escude+ 2014)
Authors: Anglada-Escude, G.; Arriagada, P.; Tuomi, M.; Zechmeister,
M.; Jenkins, J. S.; Ofir, A.; Dreizler, S.; Gerlach, E.; Marvin,
C. J.; Reiners, A.; Jeffers, S. V.; Butler, R. P.; Vogt, S. S.; Amado,
P. J.; Rodriguez-Lopez, C.; Berdinas, Z. M.; Morin, J.; Crane, J. D.;
Shectman, S. A.; Thompson, I. B.; Diaz, M.; Rivera, E.; Sarmiento,
L. F.; Jones, H. R. A.
Bibcode: 2014yCat..74439089A
Altcode:
Time-series of spectroscopic measurements used in the paper. Median
value and a perspective acceleration were subtracted to each RVs set
(Ins. 1 is HARPS, 2 is HIRES, 3 is PFS). Measurements of the FWHM,
BIS of the cross-correlation profiles and measurements of the S-index
are provided for HARPS data only. Uncertainty in the FWHM is 2.5 times
the uncertainty in BIS. Check (2012ApJS..200...15A), for more detailed
definitions of the measurements and their uses. (1 data file).
Title: PolarBase: A Database of High-Resolution Spectropolarimetric
Stellar Observations
Authors: Petit, P.; Louge, T.; Théado, S.; Paletou, F.; Manset, N.;
Morin, J.; Marsden, S. C.; Jeffers, S. V.
Bibcode: 2014PASP..126..469P
Altcode: 2014arXiv1401.1082P
PolarBase is an evolving data base that contains all stellar
data collected with the ESPaDOnS and NARVAL high-resolution
spectropolarimeters, in their reduced form, as soon as they become
public. As of early 2014, observations of 2,000 stellar objects
throughout the Hertzsprung-Russell diagram are available. Intensity
spectra are available for all targets, and the majority of the
observations also include simultaneous spectra in circular or linear
polarization, with the majority of the polarimetric measurements being
performed only in circularly polarized light (Stokes V). Observations
are associated with a cross-correlation pseudo-line profile in all
available Stokes parameters, greatly increasing the detectability
of weak polarized signatures. Stokes V signatures are detected
for more than 300 stars of all masses and evolutionary stages, and
linear polarization is detected in 35 targets. The detection rate in
Stokes V is found to be anti-correlated with the stellar effective
temperature. This unique set of Zeeman detections offers the first
opportunity to run homogeneous magnetometry studies throughout
the H-R diagram. The web interface of PolarBase is available at
http://polarbase.irap.omp.eu.
Title: Precision radial velocities of 15 M5-M9 dwarfs
Authors: Barnes, J. R.; Jenkins, J. S.; Jones, H. R. A.; Jeffers,
S. V.; Rojo, P.; Arriagada, P.; Jordán, A.; Minniti, D.; Tuomi, M.;
Pinfield, D.; Anglada-Escudé, G.
Bibcode: 2014MNRAS.439.3094B
Altcode: 2014arXiv1401.5350B; 2014MNRAS.tmp..340B
We present radial velocity measurements of a sample of M5V-M9V
stars from our Red-Optical Planet Survey, operating at 0.652-1.025
μm. Radial velocities for 15 stars, with rms precision down to 2.5
m s-1 over a week-long time-scale, are achieved using
thorium-argon reference spectra. We are sensitive to planets with
mpsin i ≥ 1.5 M⊕ (3 M⊕ at 2σ)
in the classical habitable zone, and our observations currently rule
out planets with mpsin i > 0.5 MJ at 0.03 au
for all our targets. A total of 9 of the 15 targets exhibit rms < 16
m s-1, which enables us to rule out the presence of planets
with mpsin i > 10 M⊕ in 0.03 au orbits. Since
the mean rotation velocity is of the order of 8 km s-1 for
an M6V star and 15 km s-1 for M9V, we avoid observing only
slow rotators that would introduce a bias towards low axial inclination
(i ≪ 90°) systems, which are unfavourable for planet detection. Our
targets with the highest v sin i values exhibit radial velocities
significantly above the photon-noise-limited precision, even after
accounting for v sin i. We have therefore monitored stellar activity via
chromospheric emission from the Hα and Ca II infrared triplet lines. A
clear trend of log10(LHα/Lbol) with
radial velocity rms is seen, implying that significant starspot activity
is responsible for the observed radial velocity precision floor. The
implication that most late M dwarfs are significantly spotted, and hence
exhibit time varying line distortions, indicates that observations to
detect orbiting planets need strategies to reliably mitigate against
the effects of activity-induced radial velocity variations.
Title: Modelling the hidden magnetic field of low-mass stars
Authors: Lang, P.; Jardine, M.; Morin, J.; Donati, J. -F.; Jeffers,
S.; Vidotto, A. A.; Fares, R.
Bibcode: 2014MNRAS.439.2122L
Altcode: 2014MNRAS.tmp..292L; 2014arXiv1401.4545L
Zeeman-Doppler imaging is a spectropolarimetric technique that is
used to map the large-scale surface magnetic fields of stars. These
maps in turn are used to study the structure of the stars' coronae and
winds. This method, however, misses any small-scale magnetic flux whose
polarization signatures cancel out. Measurements of Zeeman broadening
show that a large percentage of the surface magnetic flux may be
neglected in this way. In this paper we assess the impact of this
`missing flux' on the predicted coronal structure and the possible
rates of spin-down due to the stellar wind. To do this we create a
model for the small-scale field and add this to the Zeeman-Doppler maps
of the magnetic fields of a sample of 12 M dwarfs. We extrapolate this
combined field and determine the structure of a hydrostatic, isothermal
corona. The addition of small-scale surface field produces a carpet of
low-lying magnetic loops that covers most of the surface, including the
stellar equivalent of solar `coronal holes' where the large-scale field
is opened up by the stellar wind and hence would be X-ray dark. We show
that the trend of the X-ray emission measure with rotation rate (the
so-called `activity-rotation relation') is unaffected by the addition
of small-scale field, when scaled with respect to the large-scale
field of each star. The addition of small-scale field increases the
surface flux; however, the large-scale open flux that governs the
loss of mass and angular momentum in the wind remains unaffected. We
conclude that spin-down times and mass-loss rates calculated from
surface magnetograms are unlikely to be significantly influenced by
the neglect of small-scale field.
Title: Is it possible to detect planets around young active G and
K dwarfs?
Authors: Jeffers, S. V.; Barnes, J. R.; Jones, H. R. A.; Reiners,
A.; Pinfield, D. J.; Marsden, S. C.
Bibcode: 2014MNRAS.438.2717J
Altcode: 2013arXiv1311.3617J; 2014MNRAS.tmp..112J
Theoretical predictions suggest that the distribution of planets in
very young stars could be very different to that typically observed
in Gyr old systems that are the current focus of radial velocity
surveys. However, the detection of planets around young stars is
hampered by the increased stellar activity associated with young stars,
the signatures of which can bias the detection of planets. In this
paper, we place realistic limitations on the possibilities for detecting
planets around young active G and K dwarfs. The models of stellar
activity based on tomographic imaging of the G dwarf HD 141943 and the
K1 dwarf AB Dor also include contributions from plage and many small
random starspots. Our results show that the increased stellar activity
levels present on young solar-type stars strongly impacts the detection
of Earth-mass and Jupiter-mass planets and that the degree of activity
jitter is directly correlated with stellar v sin i. We also show that
for G and K dwarfs, the distribution of activity in individual stars
is more important than the differences in induced radial velocities
as a function of spectral type. We conclude that Jupiter-mass planets
can be detected close-in around fast-rotating young active stars,
Neptune-mass planets around moderate rotators and that Super-Earths
are only detectable around very slowly rotating stars. The effects
of an increase in stellar activity jitter by observing younger stars
can be compensated for by extending the observational base-line to at
least 100 epochs.
Title: Imaging the circumstellar environment of the young T Tauri
star SU Aurigae
Authors: Jeffers, S. V.; Min, M.; Canovas, H.; Rodenhuis, M.; Keller,
C. U.
Bibcode: 2014A&A...561A..23J
Altcode: 2013arXiv1311.4832J
The circumstellar environments of classical T Tauri stars are
challenging to directly image because of their high star-to-disk
contrast ratio. One method to overcome this is by using imaging
polarimetry where scattered and consequently polarised starlight from
the star's circumstellar disk can be separated from the unpolarised
light of the central star. We present images of the circumstellar
environment of SU Aur, a classical T Tauri star at the transition of T
Tauri to Herbig stars. The images directly show that the disk extends
out to 500 AU with an inclination angle of ~50°. Using interpretive
models, we derived very small grains in the surface layers of its disk,
with a very steep size- and surface-density distribution. Additionally,
we resolved a large and extended nebulosity in our images that is most
likely a remnant of the prenatal molecular cloud. The position angle
of the disk, determined directly from our images, rules out a polar
outflow or jet as the cause of this large-scale nebulosity.
Title: Three-dimensional magnetic and abundance mapping of the cool
Ap star HD 24712 . I. Spectropolarimetric observations in all four
Stokes parameters
Authors: Rusomarov, N.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Makaganiuk, V.; Rodenhuis, M.;
Snik, F.; Stempels, H. C.; Valenti, J. A.
Bibcode: 2013A&A...558A...8R
Altcode: 2013arXiv1306.0997R
Context. High-resolution spectropolarimetric observations provide
simultaneous information about stellar magnetic field topologies and
three-dimensional distributions of chemical elements. High-quality
spectra in the Stokes IQUV parameters are currently available for very
few early-type magnetic chemically peculiar stars. Here we present
analysis of a unique full Stokes vector spectropolarimetric data
set, acquired for the cool magnetic Ap star HD 24712 with a recently
commissioned spectropolarimeter.
Aims: The goal of our work
is to examine the circular and linear polarization signatures inside
spectral lines and to study variation of the stellar spectrum and
magnetic observables as a function of rotational phase.
Methods:
HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO
telescope over a period of 2010-2011. We achieved full rotational phase
coverage with 43 individual Stokes parameter observations. The resulting
spectra have a signal-to-noise ratio of 300-600 and resolving power
exceeding 105. The multiline technique of least-squares
deconvolution (LSD) was applied to combine information from the
spectral lines of Fe-peak and rare earth elements.
Results: We
used the HARPSPol spectra of HD 24712 to study the morphology of the
Stokes profile shapes in individual spectral lines and in LSD Stokes
profiles corresponding to different line masks. From the LSD Stokes V
profiles we measured the longitudinal component of the magnetic field,
⟨Bz⟩, with an accuracy of 5-10 G. We also determined the
net linear polarization from the LSD Stokes Q and U profiles. Combining
previous ⟨Bz⟩ measurements with our data allowed us to
determine an improved rotational period of the star, Prot
= 12.45812 ± 0.00019 d. We also measured the longitudinal
magnetic field from the cores of Hα and Hβ lines. The analysis of
⟨Bz⟩ measurements showed no evidence for a significant
radial magnetic field gradient in the atmosphere of HD 24712. We used
our ⟨Bz⟩ and net linear polarization measurements to
determine parameters of the dipolar magnetic field topology. We found
that magnetic observables can be reasonably well reproduced by the
dipolar model, although significant discrepancies remain at certain
rotational phases. We discovered rotational modulation of the Hα
core and related it to a non-uniform surface distribution of rare
earth elements. Based on observations collected at the European
Southern Observatory, Chile (ESO programs 084.D-0338, 085.D-0296,
086.D-0240).Figure 3 and Appendix A are available in electronic form
at http://www.aanda.org
Title: CARMENES at PPVI. High-Resolution Spectroscopy of M Dwarfs
with FEROS, CAFE and HRS
Authors: Alonso-Floriano, F. J.; Montes, D.; Jeffers, S.; Caballero,
J. A.; Zechmeister, M.; Mundt, R.; Reiners, A.; Amado, P. J.; Casal,
E.; Cortés-Contreras, M.; Modroño, Z.; Ribas, I.; Rodríguez-López,
C.; Quirrenbach, A.
Bibcode: 2013prpl.conf2K021A
Altcode:
To ensure an efficient use of CARMENES observing time, and the
highest chances of success, it is necessary first to select the most
promising targets. To achieve this, we are observing ~500 M dwarfs
at high-resolution (R = 30,000-48,000), from which we determine the
projected rotational velocity vsini with an accuracy better than 0.5-0.2
km/s and radial-velocity stability better than 0.2-0.1 km/s. Our aim
is to have at least two spectra at different epochs of the final 300
CARMENES targets. Our observations with FEROS at ESO/MPG 2.2m La Silla
, CAFE at 2.2m Calar Alto and HRS at Hobby Eberly Telescope allow
us to identify single- and double-line spectroscopic binaries and,
especially, fast rotators, which should be discarded from the target
list for exoplanet searches. Here we present preliminary results.
Title: CARMENES at PPVI. CARMENCITA Herbs and Spices to Help you
Prepare a Genuine Target Sample
Authors: Caballero, J. A.; Cortés-Contreras, M.; Alonso-Floriano,
F. J.; López-Santiago, J.; Klutsch, A.; Montes, D.; Morales, J. C.;
Abellán de Paco, F. J.; Amado, P. J.; Béjar, V. J. S.; Jeffers,
S.; Mundt, R.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Zechmeister, M.
Bibcode: 2013prpl.conf2K020C
Altcode:
CARMENCITA, the CARMENES Cool star Information and daTa Archive,
is the M-dwarf database from where we will choose our best target
sample. As part of our guaranteed time observations, about 300 late-type
M dwarfs will be monitored by CARMENES from Calar Alto during over 600
nights. CARMENCITA currently catalogues over 2000 carefully-selected
M dwarfs northern of delta > -23 deg. For each star, we tabulate
dozens of parameters (accurate astrometry, spectral typing, photometry
in 20 bands from the ultraviolet to the mid-infrared, rotational and
radial velocities, X-ray count rates and hardness ratios, close and
wide multiplicity data and many more) compiled from the literature or
measured by us with new data. The private on-line catalogue, including
preparatory science observations (i.e., high-resolution imaging, low-
and high-resolution spectroscopy), will be eventually public as a
CARMENES legacy.
Title: The color dependent morphology of the post-AGB star HD 161796
Authors: Min, M.; Jeffers, S. V.; Canovas, H.; Rodenhuis, M.; Keller,
C. U.; Waters, L. B. F. M.
Bibcode: 2013A&A...554A..15M
Altcode: 2013arXiv1303.1704M
Context. Many protoplanetary nebulae show strong asymmetries in their
surrounding shells, pointing to asymmetries during the mass loss
phase. Questions concerning the origin and the onset of deviations
from spherical symmetry are important for our understanding of the
evolution of these objects. Here we focus on the circumstellar shell of
the post-AGB star HD 161796.
Aims: We aim to detect signatures of
an aspherical outflow, and to derive its properties.
Methods: We
used the imaging polarimeter the Extreme Polarimeter (ExPo), a visitor
instrument at the William Herschel Telescope, to accurately image the
dust shell surrounding HD 161796 in various wavelength filters. Imaging
polarimetry allows us to separate the faint, polarized, light that comes
from circumstellar material from the bright, unpolarized, light from
the central star.
Results: The shell around HD 161796 is highly
aspherical. A clear signature of an equatorial density enhancement can
be seen. This structure is optically thick at short wavelengths and
changes its appearance to optically thin at longer wavelengths. In the
classification of the two different appearances of planetary nebulae
from HST images it changes from being classified as DUst-Prominent
Longitudinally-EXtended (DUPLEX) at short wavelengths to star-obvious
low-level-elongated (SOLE) at longer wavelengths. This strengthens
the interpretation that these two appearances are manifestations of
the same physical structure. Furthermore, we find that the central
star is hotter than often assumed and the relatively high observed
reddening is a consequence of circumstellar rather than interstellar
extinction. Based on observations made with the William Herschel
Telescope operated on the island of La Palma by the Isaac Newton Group
in the Spanish Observatorio del Roque de los Muchachos of the Instituto
de Astrofsicaŋsica de Canarias.
Title: Are there tangled magnetic fields on HgMn stars?
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
Bibcode: 2013A&A...554A..61K
Altcode: 2013arXiv1304.6717K
Context. Several recent spectrophotometric studies failed to detect
significant global magnetic fields in late-B HgMn chemically peculiar
stars, but some investigations have suggested the presence of strong
unstructured or tangled fields in these objects.
Aims: We used
detailed spectrum synthesis analysis to search for evidence of tangled
magnetic fields in high-quality observed spectra of eight slowly
rotating HgMn stars and one normal late-B star. We also evaluated
recent sporadic detections of weak longitudinal magnetic fields in
HgMn stars based on the moment technique.
Methods: Our spectrum
synthesis code calculated the Zeeman broadening of metal lines in HARPS
spectra, assuming an unstructured, turbulent magnetic field. A simple
line formation model with a homogeneous radial field distribution was
applied to assess compatibility between previous longitudinal field
measurements and the observed mean circular polarization signatures.
Results: Our analysis of the Zeeman broadening of magnetically
sensitive spectral lines reveals no evidence of tangled magnetic fields
in any of the studied HgMn or normal stars. We infer upper limits
of 200-700 G for the mean magnetic field modulus - much smaller than
the field strengths implied by studies based on differential magnetic
line intensification and quadratic field diagnostics. The new HARPSpol
longitudinal field measurements for the extreme HgMn star HD 65949 and
the normal late-B star 21 Peg are consistent with zero at a precision of
3-6 G. Re-analysis of our Stokes V spectra of the spotted HgMn star HD
11753 shows that the recent moment technique measurements retrieved from
the same data are incompatible with the lack of circular polarization
signatures in the spectrum of this star.
Conclusions: We conclude
that there is no evidence for substantial tangled magnetic fields on
the surfaces of studied HgMn stars. We cannot independently confirm
the presence of very strong quadratic or marginal longitudinal fields
for these stars, so results from the moment technique are likely to be
spurious. Based on observations collected at the European Southern
Observatory, Chile (ESO programmes 084.D-0338, 085.D-0296, 086.D-0240).
Title: Periodic variability of spotted M dwarfs in WTS
Authors: Goulding, N. T.; Barnes, J. R.; Pinfield, D. J.; del Burgo,
C.; Kovács, G.; Birkby, J.; Hodgkin, S.; Catalán, S.; Sipőcz, B.;
Jones, H. R. A.; Jeffers, S. V.; Nefs, S.
Bibcode: 2013EPJWC..4701006G
Altcode:
We present an analysis of the photometric variability of M dwarfs in
the WFCAM Transit Survey, selected from spectral types inferred by
their WTS and SDSS colours, with periods detected using a Lomb-Scargle
Periodogram Analisys. We estimate population membership of these objects
from their tangential velocities and photometric parralaxes. Examples
of M dwarfs with variable light curve morphologuies are found. We
discuss possible causes for this and make use of models of spotted
stars in our interpretation of the results.
Title: Realistic limitations of detecting planets around young
active stars
Authors: Jeffers, S. V.; Barnes, J. R.; Jones, H.; Pinfield, D.
Bibcode: 2013EPJWC..4709002J
Altcode:
Current planet hunting methods using the radial velocity method
are limited to observing middle-aged main-sequence stars where
the signatures of stellar activity are much less than on young
stars that have just arrived on the main-sequence. In this work we
apply our knowledge from the surface imaging of these young stars to
place realistic limitations on the possibility of detecting orbiting
planets. In general we find that the magnitude of the stellar jitter
is directly proportional to the stellar vsini. For G and K dwarfs,
we find that it is possible, for models with high stellar activity
and low stellar vsini, to be able to detect a 1 MJupiter
mass planet within 50 epochs of observations and for the M dwarfs it
is possible to detect a habitable zone Earth-like planet in 10s of
observational epochs.
Title: Red Optical Planet Survey: A radial velocity search for low
mass M dwarf planets
Authors: Barnes, J. R.; Jenkins, J. S.; Jones, H. R. A.; Rojo, P.;
Arriagada, P.; Jordán, A.; Minniti, D.; Tuomi, M.; Jeffers, S. V.;
Pinfield, D.
Bibcode: 2013EPJWC..4705002B
Altcode:
We present radial velocity results from our Red Optical Planet Survey
(ROPS), aimed at detecting low-mass planets orbiting mid-late M
dwarfs. The ∼10 ms-1 precision achieved over 2 consecutive
nights with the MIKE spectrograph at Magellan Clay is also found on
week long timescales with UVES at VLT. Since we find that UVES is
expected to attain photon limited precision of order 2 ms-1
using our novel deconvolution technique, we are limited only by the
(≤10 ms-1) stability of atmospheric lines. Rocky planet
frequencies of η⊕ = 0.3-0.7 lead us to expect high planet
yields, enabling determination of η⊕ for the uncharted
mid-late M dwarfs with modest surveys.
Title: Radial velocity signatures of Zeeman broadening
Authors: Reiners, A.; Shulyak, D.; Anglada-Escudé, G.; Jeffers,
S. V.; Morin, J.; Zechmeister, M.; Kochukhov, O.; Piskunov, N.
Bibcode: 2013A&A...552A.103R
Altcode: 2013arXiv1301.2951R
Stellar activity signatures such as spots and plages can significantly
limit the search for extrasolar planets. Current models of
activity-induced radial velocity (RV) signals focus on the impact
of temperature contrast in spots according to which they predict the
signal to diminish toward longer wavelengths. The Zeeman effect on RV
measurements counteracts this: the relative importance of the Zeeman
effect on RV measurements should grow with wavelength because the
Zeeman displacement itself grows with λ, and because a magnetic and
cool spot contributes more to the total flux at longer wavelengths. In
this paper, we model the impact of active regions on stellar RV
measurements including both temperature contrast in spots and line
broadening by the Zeeman effect. We calculate stellar line profiles
using polarized radiative transfer models including atomic and molecular
Zeeman splitting over large wavelength regions from 0.5 to 2.3 μm. Our
results show that the amplitude of the RV signal caused by the Zeeman
effect alone can be comparable to that caused by temperature contrast;
a spot magnetic field of ~1000 G can produce a similar RV amplitude
as a spot temperature contrast of ~1000 K. Furthermore, the RV signal
caused by cool and magnetic spots increases with wavelength, in contrast
to the expectation from temperature contrast alone. We also calculate
the RV signal caused by variations in average magnetic field strength
from one observation to the next, for example due to a magnetic cycle,
but find it unlikely that this can significantly influence the search
for extrasolar planets. As an example, we derive the RV amplitude
of the active M dwarf AD Leo as a function of wavelength using data
from the HARPS spectrograph. Across this limited wavelength range, the
RV signal does not diminish at longer wavelengths but shows evidence
for the opposite behavior, consistent with a strong influence of the
Zeeman effect. We conclude that the RV signal of active stars does not
vanish at longer wavelength but sensitively depends on the combination
of spot temperature and magnetic field; in active low-mass stars,
it is even likely to grow with wavelength.
Title: Magnetically Controlled Accretion on the Classical T Tauri
Stars GQ Lupi and TW Hydrae
Authors: Johns-Krull, Christopher M.; Chen, Wei; Valenti, Jeff A.;
Jeffers, Sandra V.; Piskunov, Nikolai E.; Kochukhov, Oleg; Makaganiuk,
V.; Stempels, H. C.; Snik, Frans; Keller, Christoph; Rodenhuis, M.
Bibcode: 2013ApJ...765...11J
Altcode: 2013arXiv1301.3182J
We present high spectral resolution (R ≈ 108, 000) Stokes V
polarimetry of the classical T Tauri stars (CTTSs) GQ Lup and TW Hya
obtained with the polarimetric upgrade to the HARPS spectrometer on
the ESO 3.6 m telescope. We present data on both photospheric lines
and emission lines, concentrating our discussion on the polarization
properties of the He I emission lines at 5876 Å and 6678 Å. The He
I lines in these CTTSs contain both narrow emission cores, believed
to come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large-scale
magnetospheric accretion flow. We detect strong polarization in the
narrow component of the two He I emission lines in both stars. We
observe a maximum implied field strength of 6.05 ± 0.24 kG in the
5876 Å line of GQ Lup, making it the star with the highest field
strength measured in this line for a CTTS. We find field strengths in
the two He I lines that are consistent with each other, in contrast to
what has been reported in the literature on at least one star. We do
not detect any polarization in the broad component of the He I lines
on these stars, strengthening the conclusion that they form over a
substantially different volume relative to the formation region of
the narrow component of the He I lines.
Title: Multiple views of magnetism in cool stars
Authors: Morin, J.; Jardine, M.; Reiners, A.; Shulyak, D.; Beeck,
B.; Hallinan, G.; Hebb, L.; Hussain, G.; Jeffers, S. V.; Kochukhov,
O.; Vidotto, A.; Walkowicz, L.
Bibcode: 2013AN....334...48M
Altcode: 2013csss...17...48M; 2012arXiv1208.3338M
Magnetic fields are regarded as a crucial element for our understanding
of stellar physics. They can be studied with a variety of methods which
provide complementary - and sometimes contradictory - information about
the structure, strength and dynamics of the magnetic field and its role
in the evolution of stars. Stellar magnetic fields can be investigated
either with direct methods based on the Zeeman effect or through the
observation of activity phenomena resulting from the interaction of
the field with the stellar atmosphere. In this Cool Stars 17 Splinter
Session we discussed the results obtained by the many ongoing studies
of stellar activity and direct studies of surface magnetic fields,
as well as the state-of-the-art techniques on which they are based. We
show the strengths and limitations of the various approaches currently
used and point out their evolution as well as the interest of coupling
various magnetism and activity proxies.
Title: Observing Circumstellar Neighbourhoods with the Extreme
Polarimeter
Authors: Rodenhuis, M.; Canovas, H.; Jeffers, S. V.; Min, M.; Keller,
C. U.
Bibcode: 2013ASPC..470..407R
Altcode:
The study of circumstellar environments at ever higher contrasts has
generated considerable interest in recent years. One method to increase
the contrast is to observe the linearly polarized light scattered by
the circumstellar material while suppressing the unpolarized stellar
flux. This paper presents some sample imaging polarimetry results
obtained with the Extreme Polarimeter (ExPo). ExPo operates in the
visible part of the spectrum, and currently achieves a polarimetric
sensitivity of 10-4. Despite the demise of the Utrecht
Astronomical Institute, where this instrument was developed, the
instrument is still being used and upgraded. It has now moved to the
Leiden Observatory.
Title: HARPS Spectropolarimetry of the Classical T Tauri Stars GQ
Lup and TW Hya
Authors: Johns-Krull, Christopher M.; Chen, W.; Valenti, J. A.;
Jeffers, S. V.; Piskunov, N. E.; Kochukhov, O.; Makaganiuk, V.;
Stempels, H. C.; Snik, F.; Keller, C.; Rodenhuis, M.
Bibcode: 2013AAS...22125614J
Altcode:
We present high spectral resolution Stokes V polarimetery of the
Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with
the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m
telescope. We present data on both photospheric lines and emission
lines, concentrating our discussion on the polarization properties
of the He I emission lines at 5876 A and 6678 A. The He I lines
in both these CTTS contain both narrow emission cores, believed to
come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large
scale magnetospheric accretion flow. We detect strong polarization in
the narrow component of both the He I emission lines in both stars. We
observe a maximum implied field strength of 5.8 +/- 0.3 kG in the 5876
A line of GQ Lup, the highest field strength measured to date in this
line for a CTTS. We find field strengths in the two He I lines that
are consistent with each other, unlike what has been reported in the
literature on at least one star. We do not detect any polarization in
the broad component of the He I lines on these stars, strengthening
the conclusion that they form over a substantially different volume
relative the formation region of the narrow component of the He I lines.
Title: J-band variability of M dwarfs in the WFCAM Transit Survey
Authors: Goulding, N. T.; Barnes, J. R.; Pinfield, D. J.; Kovács, G.;
Birkby, J.; Hodgkin, S.; Catalán, S.; Sipőcz, B.; Jones, H. R. A.;
Del Burgo, C.; Jeffers, S. V.; Nefs, S.; Gálvez-Ortiz, M. C.; Martin,
E. L.
Bibcode: 2012MNRAS.427.3358G
Altcode: 2012arXiv1211.5288G
We present an analysis of the photometric variability of M dwarfs in the
Wide Field Camera (WFCAM) Transit Survey. Although periodic light-curve
variability in low mass stars is generally dominated by photospheric
star spot activity, M dwarf variability in the J band has not been
as thoroughly investigated as at visible wavelengths. Spectral type
estimates for a sample of over 200 000 objects are made using spectral
type-colour relations, and over 9600 dwarfs (J < 17) with spectral
types later than K7 were found. The light curves of the late-type
sample are searched for periodicity using a Lomb-Scargle periodogram
analysis. A total of 68 periodic variable M dwarfs are found in the
sample with periods ranging from 0.16 to 90.33 d, with amplitudes in
the range of ∼0.009 to ∼0.115 in the J band. We simulate active
M dwarfs with a range of latitude-independent spot coverages and
estimate a periodically variable fraction of 1-3 per cent for stars
where spots cover more than 10 per cent of the star's surface. Our
simulated spot distributions indicate that operating in the J band,
where spot contrast ratios are minimized, enables variability in only
the most active of stars to be detected. These findings affirm the
benefits of using the J band for planetary transit searches compared
to visible bands. We also serendipitously find a ΔJ > 0.2 mag
flaring event from an M4V star in our sample.
Title: The Exoplanet Characterization Observatory (EChO): performance
model EclipseSim and applications
Authors: van Boekel, Roy; Benneke, Björn; Heng, Kevin; Hu, Renyu;
Madhusudhan, Nikku; Quanz, Sascha; Bétrémieux, Yan; Bouwman, Jeroen;
Chen, Guo; Decin, Leen; de Kok, Remco; Glauser, Adrian; Güdel,
Manuel; Hauschildt, Peter; Henning, Thomas; Jeffers, Sandra; Jin,
Sheng; Kaltenegger, Lisa; Kerschbaum, Franz; Krause, Oliver; Lammer,
Helmut; Luntzer, Armin; Meyer, Michael; Miguel, Yamila; Mordasini,
Christoph; Ottensamer, Roland; Rank-Lueftinger, Theresa; Reiners,
Ansgar; Reinhold, Timo; Schmid, Hans Martin; Snellen, Ignas; Stam,
Daphne; Sun, Zhao; Vandenbussche, Bart
Bibcode: 2012SPIE.8442E..1FV
Altcode:
We present EclipseSim, a radiometric model for exoplanet transit
spectroscopy that allows easy exploration of the fundamental
performance limits of any space-based facility aiming to perform such
observations. It includes a library of stellar model atmosphere spectra
and can either approximate exoplanet spectra by simplified models, or
use any theoretical or observed spectrum, to simulate observations. All
calculations are done in a spectrally resolved fashion and the
contributions of the various fundamental noise sources are budgeted
separately, allowing easy assessment of the dominant noise sources,
as a function of wavelength. We apply EclipseSim to the Exoplanet
Characterization Observatory (EChO), a proposed mission dedicated to
exoplanet transit spectroscopy that is currently in competition for
the M3 launch slot of ESA’s cosmic vision programme. We show several
case studies on planets with sizes in the super-Earth to Jupiter range,
and temperatures ranging from the temperate to the ≍1500K regime,
demonstrating the power and versatility of EChO. EclipseSim is publicly
available.*
Title: CARMENES. I: instrument and survey overview
Authors: Quirrenbach, Andreas; Amado, Pedro J.; Seifert, Walter;
Sánchez Carrasco, Miguel A.; Mandel, Holger; Caballero, Jose A.;
Mundt, Reinhard; Ribas, Ignasi; Reiners, Ansgar; Abril, Miguel;
Aceituno, Jesus; Alonso-Floriano, Javier; Ammler-von Eiff, Matthias;
Anglada-Escude, Guillem; Antona Jiménez, Regina; Anwand-Heerwart,
Heiko; Barrado y Navascués, David; Becerril, Santiago; Bejar,
Victor; Benitez, Daniel; Cardenas, Concepcion; Claret, Antonio;
Colome, Josep; Cortés-Contreras, Miriam; Czesla, Stefan; del Burgo,
Carlos; Doellinger, Michaela; Dorda, R.; Dreizler, Stefan; Feiz,
Carmen; Fernandez, Matilde; Galadi, David; Garrido, Rafael; González
Hernández, Jonay; Guardia, Josep; Guenther, Eike; de Guindos, Enrique;
Gutiérrez-Soto, Juan; Hagen, Hans J.; Hatzes, Artie; Hauschildt,
Peter; Helmling, Jens; Henning, Thomas; Herrero, Enrique; Huber,
Armin; Huber, Klaus; Jeffers, Sandra; Joergens, Viki; de Juan,
Enrique; Kehr, M.; Klutsch, Alexis; Kürster, Martin; Lalitha, S.;
Laun, Werner; Lemke, Ulrike; Lenzen, Rainer; Lizon, Jean-Louis; López
del Fresno, Mauro; López-Morales, Mercedes; López-Santiago, Javier;
Mall, Ulrich; Martin, Eduardo; Martín-Ruiz, Susana; Mirabet, Eduard;
Montes, David; Morales, Juan Carlos; Morales Muñoz, Rafael; Moya,
Andres; Naranjo, Vianak; Oreiro, Raquel; Pérez Medialdea, David;
Pluto, Michael; Rabaza, Ovidio; Ramon, Alejandro; Rebolo, Rafael;
Reffert, Sabine; Rhode, Petra; Rix, Hans-Walter; Rodler, Florian;
Rodríguez, Eloy; Rodríguez López, Cristina; Rodríguez Pérez,
Emilio; Rodriguez Trinidad, A.; Rohloff, Ralf-Reiner; Sánchez-Blanco,
Ernesto; Sanz-Forcada, Jorge; Schäfer, Sebastian; Schiller, Jörg;
Schmidt, Christof; Schmitt, Jürgen; Solano, Enrique; Stahl, Otmar;
Storz, Clemens; Stürmer, Julian; Suarez, Juan Carlos; Thiele, Ulrich;
Ulbrich, Rainer; Vidal-Dasilva, Manuela; Wagner, Karl; Winkler,
Johannes; Xu, Wenli; Zapatero Osorio, Maria Rosa; Zechmeister, Mathias
Bibcode: 2012SPIE.8446E..0RQ
Altcode:
CARMENES (Calar Alto high-Resolution search for M dwarfs with
Exo-earths with Near-infrared and optical Echelle Spectrographs)
is a next-generation instrument for the 3.5m telescope at the Calar
Alto Observatory, built by a consortium of eleven Spanish and German
institutions. The CARMENES instrument consists of two separate
échelle spectrographs covering the wavelength range from 0.55 μm
to 1.7 μm at a spectral resolution of R = 82, 000, fed by fibers
from the Cassegrain focus of the telescope. Both spectrographs are
housed in temperature-stabilized vacuum tanks, to enable a long-term
1 m/s radial velocity precision employing a simultaneous calibration
with Th-Ne and U-Ne emission line lamps. CARMENES has been optimized
for a search for terrestrial planets in the habitable zones (HZs)
of low-mass stars, which may well provide our first chance to study
environments capable of supporting the development of life outside the
Solar System. With its unique combination of optical and near-infrared
´echelle spectrographs, CARMENES will provide better sensitivity for
the detection of low-mass planets than any comparable instrument, and
a powerful tool for discriminating between genuine planet detections
and false positives caused by stellar activity. The CARMENES survey
will target 300 M dwarfs in the 2014 to 2018 time frame.
Title: The extreme polarimeter: design, performance, first results
and upgrades
Authors: Rodenhuis, M.; Canovas, H.; Jeffers, S. V.; de Juan Ovelar,
Maria; Min, M.; Homs, L.; Keller, C. U.
Bibcode: 2012SPIE.8446E..9IR
Altcode: 2012arXiv1211.6300R
Well over 700 exoplanets have been detected to date. Only a handful of
these have been observed directly. Direct observation is extremely
challenging due to the small separation and very large contrast
involved. Imaging polarimetry offers a way to decrease the contrast
between the unpolarized starlight and the light that has become
linearly polarized after scattering by circumstellar material. This
material can be the dust and debris found in circumstellar disks, but
also the atmosphere or surface of an exoplanet. We present the design,
calibration approach, polarimetric performance and sample observation
results of the Extreme Polarimeter, an imaging polarimeter for the
study of circumstellar environments in scattered light at visible
wavelengths. The polarimeter uses the beam-exchange technique, in
which the two orthogonal polarization states are imaged simultaneously
and a polarization modulator is swaps the polarization states of the
two beams before the next image is taken. The instrument currently
operates without the aid of Adaptive Optics. To reduce the effects
of atmospheric seeing on the polarimetry, the images are taken at
a frame rate of 35 fps, and large numbers of frames are combined to
obtain the polarization images. Four successful observing runs have
been performed using this instrument at the 4.2 m William Herschel
Telescope on La Palma, targeting young stars with protoplanetary disks
as well as evolved stars surrounded by dusty envelopes. In terms of
fractional polarization, the instrument sensitivity is better than
10-4. The contrast achieved between the central star and
the circumstellar source is of the order 10-6. We show that
our calibration approach yields absolute polarization errors below 1%.
Title: Constraining the circumbinary envelope of Z Canis Majoris
via imaging polarimetry
Authors: Canovas, H.; Min, M.; Jeffers, S. V.; Rodenhuis, M.; Keller,
C. U.
Bibcode: 2012A&A...543A..70C
Altcode: 2012arXiv1205.3784C
Context. Z CMa is a complex binary system composed of a Herbig Be
and an FU Ori star. The Herbig star is surrounded by a dust cocoon of
variable geometry, and the whole system is surrounded by an infalling
envelope. Previous spectropolarimetric observations have reported a
preferred orientation of the polarization angle, perpendicular to the
direction of a very extended, parsec-sized jet associated with the
Herbig star.
Aims: The variability in the amount of polarized
light has been associated to changes in the geometry of the dust cocoon
that surrounds the Herbig star. We aim to constrain the properties of
Z CMa by means of imaging polarimetry at optical wavelengths.
Methods: Using ExPo, a dual-beam imaging polarimeter that operates at
optical wavelengths, we have obtained imaging (linear) polarimetric
data of Z CMa. Our observations were secured during the return to
quiescence after the 2008 outburst.
Results: We detect three
polarized features over Z CMa. Two of these features are related to
the two jets reported in this system: the large jet associated to the
Herbig star, and the micro-jet associated to the FU Ori star. Our
results suggest that the micro-jet extends to a distance ten times
longer than reported in previous studies. The third feature suggests the
presence of a hole in the dust cocoon that surrounds the Herbig star
of this system. According to our simulations, this hole can produce
a pencil beam of light that we see scattered off the low-density
envelope surrounding the system. Based on observations made with
the William Herschel Telescope operated on the island of La Palma by
the Isaac Newton Group in the Spanish Observatorio del Roque de los
Muchachos of the Instituto de Astrofísica de Canarias.
Title: Red Optical Planet Survey: a new search for habitable earths
in the southern sky
Authors: Barnes, J. R.; Jenkins, J. S.; Jones, H. R. A.; Rojo, P.;
Arriagada, P.; Jordán, A.; Minniti, D.; Tuomi, M.; Jeffers, S. V.;
Pinfield, D.
Bibcode: 2012MNRAS.424..591B
Altcode: 2012arXiv1204.6283B
We present the first results from our Red Optical Planet Survey to
search for low-mass planets orbiting late-type dwarfs (M5.5V-M9V)
in their habitable zones. Our observations with the red arm of the
Magellan Inamori Kyocera Echelle spectrograph (0.5-0.9 μm) at the
6.5-m Magellan Clay telescope at Las Campanas Observatory indicate
that ≥92 per cent of the flux lies beyond 0.7 μm. We use a novel
approach that is essentially a hybrid of the simultaneous iodine and
ThAr methods for determining precision radial velocities. We apply least
squares deconvolution to obtain a single high signal-to-noise ratio
(S/N) stellar line for each spectrum and cross-correlate against the
simultaneously observed telluric line profile, which we derive in the
same way. Utilizing the 0.62-0.90 μm region, we have achieved
an rms precision of 10 ms-1 for an M5.5V spectral type
star with spectral S/N ∼ 160 on 5-min time-scales. By M8V spectral
type, a precision of ∼30 ms-1 at S/N = 25 is suggested,
although more observations are needed. An assessment of our errors
and scatter in the radial velocity points hints at the presence of
stellar radial velocity variations. Of our sample of seven stars, two
show radial velocity signals at 6σ and 10σ of the cross-correlation
uncertainties. We find that chromospheric activity (via Hα variation)
does not have an impact on our measurements and are unable to determine
a relationship between the derived photospheric line profile morphology
and radial velocity variations without further observations. If the
signals are planetary in origin, our findings are consistent with
estimates of Neptune mass planets that predict a frequency of 13-27
per cent for early M dwarfs. Our current analysis indicates the we
can achieve a sensitivity that is equivalent to the amplitude induced
by a 6 M⊕ planet orbiting in the habitable zone. Based
on simulations, we estimate that <10 M⊕ habitable
zone planets will be detected in a new stellar mass regime, with
≤20 epochs of observations. Higher resolution and greater instrument
stability indicate that photon-limited precisions of 2 ms-1
are attainable on moderately rotating M dwarfs (with vsin i≤ 5 km
s-1) using our technique.
Title: HARPS spectropolarimetry of classical T Tauri stars
Authors: Johns-Krull, C. M.; Valenti, J. A.; Jeffers, S. V.; Piskunov,
N. E.; Kochukhov, O.; Keller, C.; Snik, F.; Rodenhuis, M.; Makaganiuk,
V.; Stempels, H.
Bibcode: 2012AIPC.1429...43J
Altcode:
We present high spectral resolution Stokes V polarimetery of the
Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with
the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m
telescope. We present data on both photospheric lines and emission
lines, concentrating our discussion on the polarization properties
of the He I emission lines at 5876 A and 6678 A. The He I lines
in both these CTTS contain both narrow emission cores, believed to
come from near the accretion shock region on these stars, and broad
emission components which may come from either a wind or the large
scale magnetospheric accretion flow. We detect strong polarization in
the narrow component of both the He I emission lines in both stars. We
observe a maximum implied field strength of 5.8 +/- 0.3 kG in the 5876
A˚ line of GQ Lup, the highest field strength measured to date in
this line for a CTTS. We find field strengths in the two He I lines
that are consistent with each other, unlike what has been reported in
the literature on at least one star. We do not detect any polarization
in the broad component of the He I lines on these stars, strengthening
the conclusion that they form over a substantially different volume
relative the formation region of the narrow component of the He I lines.
Title: Magnetism, chemical spots, and stratification in the HgMn
star ϕ Phoenicis
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
Bibcode: 2012A&A...539A.142M
Altcode: 2011arXiv1111.6065M
Context. Mercury-manganese (HgMn) stars have been considered as
non-magnetic and non-variable chemically peculiar (CP) stars for a
long time. However, recent discoveries of the variability in spectral
line profiles have suggested an inhomogeneous surface distribution
of chemical elements in some HgMn stars. From the studies of other
CP stars it is known that magnetic field plays a key role in the
formation of surface spots. All attempts to find magnetic fields in
HgMn stars have yielded negative results.
Aims: In this study,
we investigate the possible presence of a magnetic field in ϕ Phe
(HD 11753) and reconstruct surface distribution of chemical elements
that show variability in spectral lines. We also test a hypothesis
that a magnetic field is concentrated in chemical spots and look into
the possibility that some chemical elements are stratified with depth
in the stellar atmosphere.
Methods: Our analysis is based on
high-quality spectropolarimetric time-series observations, covering
a full rotational period of the star. Spectra were obtained with the
HARPSpol at the ESO 3.6-m telescope. To increase the sensitivity of
the magnetic field search, we employed the least-squares deconvolution
(LSD) technique. Using Doppler imaging code INVERS10, we reconstructed
surface chemical distributions by utilising information from
multiple spectral lines. The vertical stratification of chemical
elements was calculated with the DDAFit program.
Results:
Combining information from all suitable spectral lines, we set an
upper limit of 4 G on the mean longitudinal magnetic field. For
chemical spots, an upper limit on the longitudinal field varies
between 8 and 15 G. We confirmed the variability of Y, Sr, and Ti
and detected variability in Cr lines. Stratification analysis showed
that Y and Ti are not concentrated in the uppermost atmospheric
layers.
Conclusions: Our spectropolarimetric observations
rule out the presence of a strong, globally-organised magnetic field
in ϕ Phe. This implies an alternative mechanism of spot formation,
which could be related to a non-equilibrium atomic diffusion. However,
the typical time scales of the variation in stratification predicted
by the recent time-dependent diffusion models exceed significantly
the spot evolution time-scale reported for ϕ Phe. Based on
observations collected at the European Southern Observatory, Chile
(ESO programme 084.D-0338). Figures 9-12 are available in electronic
form at http://www.aanda.org
Title: Dynamical and collisional evolution of Halley-type comets
Authors: van der Helm, E.; Jeffers, S. V.
Bibcode: 2012Icar..218..448V
Altcode:
The number of observed Halley-type comets is hundreds of times
less than predicted by models (Levison, H.F., Dones, L., Duncan,
M.J. [2001]. Astron. J. 121, 2253-2267). In this paper we investigate
the impact of collisions with planetesimals on the evolution of
Halley-type comets. First we compute the dynamical evolution of
a sub-set of 21 comets using the MERCURY integrator package over
100 Myr. The dynamical lifetime is determined to be of the order of
105-106 years in agreement with previous work. The
collisional probability of Halley-type comets colliding with known
asteroids, a simulated population of Kuiper-belt objects, and planets,
is calculated using a modified, Öpik-based collision code. Our results
show that the catastrophic disruption of the cometary nucleus has a
very low probability of occurring, and disruption through cumulative
minor impacts is concluded to be negligible. The dust mantle formed from
ejected material falling back to the comet’s surface is calculated to
be less than a few centimeters thick, which is insignificant compared
to the mantle formed by volatile depletion, while planetary encounters
were found to be a negligible disruption mechanism.
Title: Direct imaging of a massive dust cloud around R Coronae
Borealis
Authors: Jeffers, S. V.; Min, M.; Waters, L. B. F. M.; Canovas, H.;
Rodenhuis, M.; de Juan Ovelar, M.; Chies-Santos, A. L.; Keller, C. U.
Bibcode: 2012A&A...539A..56J
Altcode: 2012arXiv1203.1265J
We present recent polarimetric images of the highly variable star R CrB
using ExPo and archival WFPC2 images from the HST. We observed R CrB
during its current dramatic minimum where it decreased more than 9 mag
due to the formation of an obscuring dust cloud. Since the dust cloud is
only in the line-of-sight, it mimics a coronograph allowing the imaging
of the star's circumstellar environment. Our polarimetric observations
surprisingly show another scattering dust cloud at approximately 1.3''
or 2000 AU from the star. We find that to obtain a decrease in the
stellar light of 9 mag and with 30% of the light being reemitted
at infrared wavelengths (from R CrB's SED) the grains in R CrB's
circumstellar environment must have a very low albedo of approximately
0.07%. We show that the properties of the dust clouds formed around R
CrB are best fitted using a combination of two distinct populations of
grains size. The first are the extremely small 5 nm grains, formed in
the low density continuous wind, and the second population of large
grains (~0.14 μm) which are found in the ejected dust clouds. The
observed scattering cloud, not only contains such large grains, but
is exceptionally massive compared to the average cloud. Based on
observations made with the William Herschel Telescope operated on the
island of La Palma by the Isaac Newton Group in the Spanish Observatorio
del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
Title: Innovative Imaging of Young Stars: First Light ExPo
Observations
Authors: Jeffers, S. V.; Canovas, H.; Keller, C. U.; Min, M.;
Rodenhuis, M.
Bibcode: 2011ASPC..448...15J
Altcode: 2011csss...16...15J
We have developed an innovative imaging polariemter, ExPo, that excels
in the imaging of the circumstellar environments of young stars. The
basic physics that ExPo exploits is that starlight reflected from a
star's circumstellar environment becomes linearly polarised, making
it easily separable from unpolarised starlight. Our preliminary
results, from the William Herschel Telescope in La Palma, show that
ExPo has successfully detected several known protoplanetary disks out
to a much larger distance and at a finer resolution than previously
observed. ExPo has also made a significant number of new detections
of protoplanetary disks and stellar outflows. We use innovative data
analysis techniques, related to speckle interferometry, to detect the
innermost parts of the disk to much closer than any other techniques
operating at visible wavelengths. In this paper I present highlights
of ExPo's first light observations.
Title: New Insights into Stellar Magnetism from the Spectropolarimetry
in All Four Stokes Parameters
Authors: Kochukhov, O.; Snik, F.; Piskunov, N.; Jeffers, S. V.;
Keller, C. U.; Makaganiuk, V.; Valenti, J. A.; Johns-Krull, C. M.;
Rodenhuis, M.; Stempels, H. C.
Bibcode: 2011ASPC..448..245K
Altcode: 2011csss...16..245K
Development of high-resolution spectropolarimetry has stimulated a
major progress in our understanding of the magnetism and activity of
late-type stars. During the last decade magnetic fields were discovered
and mapped for various types of active stars using spectropolarimetric
methods. However, these observations and modeling attempts are
inherently incomplete since they are based on the interpretation of the
stellar circular polarization alone. Taking advantage of the recently
commissioned HARPS polarimeter, we obtained the first systematic
observations of cool active stars in all four Stokes parameters. Here we
report detection of the magnetically induced linear polarization in the
RS CVn binary HR 1099 and phase-resolved full Stokes vector observations
of varepsilon Eri. For the latter star we measured the field strength
with the precision of ∼0.1 G over a complete rotation cycle and
reconstructed the global field topology with the help of magnetic
Doppler imaging. Our observations of the inactive solar-like star α
Cen A indicate the absence of the global field stronger than 0.2 G.
Title: Observational Evidence for a Non Solar-Type Dynamo Operating
in Late-Type Stars
Authors: Jeffers, S. V.; Donati, J.
Bibcode: 2011ASPC..449..285J
Altcode:
We present high-resolution images of the young rapidly rotating
G0 dwarf HD 171488 using both Stokes I and Stokes V data taken
over four epochs. Using the good phase coverage of our data we
measure differential rotation for each epoch. The results show the
highest measurements of differential rotation ever measured using
Zeeman-Doppler imaging techniques. We also find that the differential
rotation measurement obtained from Stokes V data is approximately
the same as that derived from the Stokes I data and that they show no
temporal evolution. Other measurements of differential rotation using
both brightness and magnetic data have been made for the K1 V AB Dor
where there is a large variation between the two data sets. For AB
Dor this indicates that magnetic regions are not anchored at the same
depth in the convective zone, and therefore do not experience the same
shear. The marginal difference in the differential rotation measurements
for Stokes I and V data and the absense of any temporal evolution for
HD 171488 further supports the existence of a non solar-type dynamo,
as HD 171488 has a much thinner convective zone than AB Dor.
Title: Data Reduction Approach for the Extreme Polarimeter
Authors: Canovas, H.; Rodenhuis, M.; Jeffers, S. V.; Keller, C. U.
Bibcode: 2011ASPC..449...79C
Altcode:
ExPo (Extreme Polarimeter) is an imaging polarimeter that we are
building at Utrecht University, The Netherlands. It will detect
polarized light from circumstellar disks and extrasolar planets,
initially at the 4.2 m WHT and later at other telescopes. We have
developed a data reduction approach that minimizes the influence of
instrumental and atmospherical effects by using a partially transmitting
coronagraph focal-plane mask. The approach has been tested with a
laboratory simulator and an ExPo prototype.
Title: Simulating Polarized Light from Exoplanets
Authors: Jeffers, S. V.; Miesen, N.; Rodenhuis, M.; Keller, C. U.;
Canovas, H.
Bibcode: 2011ASPC..449..391J
Altcode:
In Utrecht we are building an imaging polarimeter, ExPo (Extreme
Polarimeter), to image circumstellar disk and characterize extra-solar
planets. To test and calibrate ExPo, we have built a laboratory-based
simulator that mimicks a star with a Jupiter-like exoplanet as seen by
the 4.2 m William-Herschel Telescope. The star and planet are simulated
using two single-mode fibres in close proximity that are fed with a
broadband arc lamp. The unpolarized star has a flux of 1011
photons s-1, to simulate a mv=0 star, and the planet is
partially linearly polarized, with a flux of as little as 102
photons s-1 to simulate reflected star light with a contrast
ratio of as much as 10-9. The telescope is simulated with
two lenses, and seeing can be included with a rotating glass plate
covered with hairspray, while dispersion is approximated with a wedge
prism. These are the first realistic laboratory simulations of imaging
polarimetry for exoplanet detection and characterization.
Title: Design and Prototype Results of the ExPo Imaging Polarimeter
Authors: Rodenhuis, M.; Canovas, H.; Jeffers, S.; Keller, C.
Bibcode: 2011ASPC..449...33R
Altcode:
We present the design and prototype laboratory results of ExPo, an
imaging polarimeter for the study of circumstellar disks and possibly
exoplanet detection currently under development at the University of
Utrecht. The instrument is designed to achieve a contrast ratio of
10-9 between the unpolarized starlight and the polarized
source. First light is scheduled for the second half of 2008 at the
4.2 m William Herschel telescope at La Palma. The instrument is based
on the dual beam-exchange technique, simultaneously imaging the two
orthogonal polarization states. It employs a ferro-electric liquid
crystal retarder and a single electron-multiplying camera for fast
modulation of the polarization. The instrument operates in the visible
and has a field of view of (20″ × 20″).
Title: No magnetic field in the spotted HgMn star μ Leporis
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
Bibcode: 2011A&A...534L..13K
Altcode: 2011arXiv1110.0829K
Context. Chemically peculiar stars of the mercury-manganese (HgMn)
type represent a new class of spotted late-B stars, in which evolving
surface chemical inhomogeneities are apparently unrelated to the
presence of strong magnetic fields but are produced by some hitherto
unknown astrophysical mechanism.
Aims: The goal of this study
is to perform a detailed line profile variability analysis and carry
out a sensitive magnetic field search for one of the brightest HgMn
stars - μ Lep.
Methods: We acquired a set of very high-quality
intensity and polarization spectra of μ Lep with the HARPSpol
polarimeter. These data were analyzed with the multiline technique
of least-squares deconvolution in order to extract information on
the magnetic field and line profile variability.
Results:
Our spectra show very weak but definite variability in the lines
of Sc, all Fe-peak elements represented in the spectrum of μ Lep,
as well as Y, Sr, and Hg. Variability might also be present in the
lines of Si and Mg. Anomalous profile shapes of Ti ii and Y ii lines
suggest a dominant axisymmetric distribution of these elements. At
the same time, we found no evidence of the magnetic field in μ Lep,
with the 3σ upper limit of only 3 G for the mean longitudinal magnetic
field. This is the most stringent upper limit on the possible magnetic
field derived for a spotted HgMn star.
Conclusions: The very
weak variability detected for many elements in the spectrum μ Lep
suggests that low-contrast chemical inhomogeneities may be common in
HgMn stars and that they have not been recognized until now due to the
limited precision of previous spectroscopic observations and a lack
of time-series data. The null result of the magnetic field search
reinforces the conclusion that formation of chemical spots in HgMn
stars is not magnetically driven. Based on observations collected
at the European Southern Observatory, Chile (ESO programs 084.D-0338,
086.D-0240).
Title: The search for magnetic fields in mercury-manganese stars
Authors: Makaganiuk, Vitalii; Kochukhov, Oleg; Piskunov, Nikolai;
Jeffers, Sandra V.; Johns-Krull, Christopher M.; Keller, Christoph
U.; Rodenhuis, Michiel; Snik, Frans; Stempels, Henricus C.; Valenti,
Jeff A.
Bibcode: 2011IAUS..272..202M
Altcode:
Mercury-manganese (HgMn) stars were considered to be non-magnetic,
showing no evidence of surface spots. However, recent investigations
revealed that some stars in this class possess an inhomogeneous
distribution of chemical elements on their surfaces. According to
our current understanding, the most probable mechanism of spot
formation involves magnetic fields. Taking the advantage of a
newly-built polarimeter attached to the HARPS spectrometer at the
ESO 3.6m-telescope, we performed a high-precision spectropolarimetric
survey of a large group of HgMn stars. The main purpose of this study
was to find out how typical it is for HgMn stars to have weak magnetic
fields. We report no magnetic field detection for any of the studied
objects, with a typical precision of the longitudinal field measurements
of 10 G and down to 1 Gauss for some of the stars. We conclude that HgMn
stars lack large-scale magnetic fields typical of spotted magnetic Ap
stars and probably lack any fields capable of creating and sustaining
chemical spots. Our study confirms that alongside the magnetically
altered atomic diffusion, there must be other structure formation
mechanism operating in the atmospheres of late-B main sequence stars.
Title: Data-reduction techniques for high-contrast imaging
polarimetry. Applications to ExPo
Authors: Canovas, H.; Rodenhuis, M.; Jeffers, S. V.; Min, M.; Keller,
C. U.
Bibcode: 2011A&A...531A.102C
Altcode: 2011arXiv1105.2961C
Context. Imaging polarimetry is a powerful tool for detecting and
characterizing exoplanets and circumstellar environments. Polarimetry
allows a separation of the light coming from an unpolarized source
such as a star and the polarized source such as a planet or a
protoplanetary disk. Future facilities like SPHERE at the VLT or
EPICS at the E-ELT will incorporate imaging polarimetry to detect
exoplanets. The Extreme Polarimeter (ExPo) is a dual-beam imaging
polarimeter that can currently reach contrast ratios of 105,
enough to characterize circumstellar environments.
Aims: We
present the data-reduction steps for a dual-beam imaging polarimeter
that can reach contrast ratios of 105.
Methods: The
data obtained with ExPo at the William Herschel Telescope (WHT) are
analyzed. Instrumental artifacts and noise sources are discussed for
an unpolarized star and for a protoplanetary disk (AB Aurigae).
Results: The combination of fast modulation and dual-beam techniques
allows us to minimize instrumental artifacts. A proper data processing
and alignment of the images is fundamental when dealing with high
contrasts. Imaging polarimetry proves to be a powerful method to
resolve circumstellar environments even without a coronagraph mask or
an adaptive optics system.
Title: EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide
Campaign
Authors: Meech, K. J.; A'Hearn, M. F.; Adams, J. A.; Bacci, P.; Bai,
J.; Barrera, L.; Battelino, M.; Bauer, J. M.; Becklin, E.; Bhatt,
B.; Biver, N.; Bockelée-Morvan, D.; Bodewits, D.; Böhnhardt, H.;
Boissier, J.; Bonev, B. P.; Borghini, W.; Brucato, J. R.; Bryssinck,
E.; Buie, M. W.; Canovas, H.; Castellano, D.; Charnley, S. B.;
Chen, W. P.; Chiang, P.; Choi, Y. -J.; Christian, D. J.; Chuang,
Y. -L.; Cochran, A. L.; Colom, P.; Combi, M. R.; Coulson, I. M.;
Crovisier, J.; Dello Russo, N.; Dennerl, K.; DeWahl, K.; DiSanti,
M. A.; Facchini, M.; Farnham, T. L.; Fernández, Y.; Florén,
H. G.; Frisk, U.; Fujiyoshi, T.; Furusho, R.; Fuse, T.; Galli, G.;
García-Hernández, D. A.; Gersch, A.; Getu, Z.; Gibb, E. L.; Gillon,
M.; Guido, E.; Guillermo, R. A.; Hadamcik, E.; Hainaut, O.; Hammel,
H. B.; Harker, D. E.; Harmon, J. K.; Harris, W. M.; Hartogh, P.;
Hashimoto, M.; Häusler, B.; Herter, T.; Hjalmarson, A.; Holland,
S. T.; Honda, M.; Hosseini, S.; Howell, E. S.; Howes, N.; Hsieh,
H. H.; Hsiao, H. -Y.; Hutsemékers, D.; Immler, S. M.; Jackson, W. M.;
Jeffers, S. V.; Jehin, E.; Jones, T. J.; de Juan Ovelar, M.; Kaluna,
H. M.; Karlsson, T.; Kawakita, H.; Keane, J. V.; Keller, L. D.;
Kelley, M. S.; Kinoshita, D.; Kiselev, N. N.; Kleyna, J.; Knight,
M. M.; Kobayashi, H.; Kobulnicky, H. A.; Kolokolova, L.; Kreiny, M.;
Kuan, Y. -J.; Küppers, M.; Lacruz, J. M.; Landsman, W. B.; Lara,
L. M.; Lecacheux, A.; Levasseur-Regourd, A. C.; Li, B.; Licandro,
J.; Ligustri, R.; Lin, Z. -Y.; Lippi, M.; Lis, D. C.; Lisse, C. M.;
Lovell, A. J.; Lowry, S. C.; Lu, H.; Lundin, S.; Magee-Sauer, K.;
Magain, P.; Manfroid, J.; Mazzotta Epifani, E.; McKay, A.; Melita,
M. D.; Mikuz, H.; Milam, S. N.; Milani, G.; Min, M.; Moreno, R.;
Mueller, B. E. A.; Mumma, M. J.; Nicolini, M.; Nolan, M. C.; Nordh,
H. L.; Nowajewski, P. B.; Odin Team; Ootsubo, T.; Paganini, L.;
Perrella, C.; Pittichová, J.; Prosperi, E.; Radeva, Y. L.; Reach,
W. T.; Remijan, A. J.; Rengel, M.; Riesen, T. E.; Rodenhuis, M.;
Rodríguez, D. P.; Russell, R. W.; Sahu, D. K.; Samarasinha, N. H.;
Sánchez Caso, A.; Sandqvist, A.; Sarid, G.; Sato, M.; Schleicher,
D. G.; Schwieterman, E. W.; Sen, A. K.; Shenoy, D.; Shi, J. -C.;
Shinnaka, Y.; Skvarc, J.; Snodgrass, C.; Sitko, M. L.; Sonnett, S.;
Sosseini, S.; Sostero, G.; Sugita, S.; Swinyard, B. M.; Szutowicz,
S.; Takato, N.; Tanga, P.; Taylor, P. A.; Tozzi, G. -P.; Trabatti,
R.; Trigo-Rodríguez, J. M.; Tubiana, C.; de Val-Borro, M.; Vacca,
W.; Vandenbussche, B.; Vaubaillion, J.; Velichko, F. P.; Velichko,
S. F.; Vervack, R. J., Jr.; Vidal-Nunez, M. J.; Villanueva, G. L.;
Vinante, C.; Vincent, J. -B.; Wang, M.; Wasserman, L. H.; Watanabe,
J.; Weaver, H. A.; Weissman, P. R.; Wolk, S.; Wooden, D. H.; Woodward,
C. E.; Yamaguchi, M.; Yamashita, T.; Yanamandra-Fischer, P. A.; Yang,
B.; Yao, J. -S.; Yeomans, D. K.; Zenn, T.; Zhao, H.; Ziffer, J. E.
Bibcode: 2011ApJ...734L...1M
Altcode: 2011arXiv1106.0367K
Earth- and space-based observations provide synergistic information
for space mission encounters by providing data over longer timescales,
at different wavelengths and using techniques that are impossible with
an in situ flyby. We report here such observations in support of the
EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and
dark, and exhibited a very rapidly changing rotation period. Prior to
the onset of activity, the period was ~16.4 hr. Starting in 2010 August
the period changed from 16.6 hr to near 19 hr in December. With respect
to dust composition, most volatiles and carbon and nitrogen isotope
ratios, the comet is similar to other Jupiter-family comets. What
is unusual is the dominance of CO2-driven activity near
perihelion, which likely persists out to aphelion. Near perihelion the
comet nucleus was surrounded by a large halo of water-ice grains that
contributed significantly to the total water production.
Title: Chemical spots in the absence of magnetic field in the binary
HgMn star 66 Eridani
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
Bibcode: 2011A&A...529A.160M
Altcode: 2011arXiv1102.4661M
Context. According to our current understanding, a subclass of the
upper main-sequence chemically peculiar stars, called mercury-manganese
(HgMn), is non-magnetic. Nevertheless, chemical inhomogeneities were
recently discovered on their surfaces. At the same time, no global
magnetic fields stronger than 1-100 G are detected by systematic
studies.
Aims: The goals of our study are to search for a
magnetic field in the HgMn binary system 66 Eri and to investigate
chemical spots on the stellar surfaces of both components.
Methods: Our analysis is based on high-quality spectropolarimetric
time-series observations obtained during 10 consecutive nights with
the HARPSpol instrument at the ESO 3.6-m telescope. To increase the
sensitivity of the magnetic field search we employed a least-squares
deconvolution (LSD). We used spectral disentangling to measure radial
velocities and study the line profile variability. Chemical spot
geometry was reconstructed using multi-line Doppler imaging.
Results: We report a non-detection of magnetic field in 66 Eri, with
error bars 10-24 G for the longitudinal field. Circular polarization
profiles also do not indicate any signatures of complex surface
magnetic fields. For a simple dipolar field configuration we estimated
an upper limit of the polar field strength to be 60-70 G. For the
HgMn component we found variability in spectral lines of Ti, Ba,
Y, and Sr with the rotational period equal to the orbital one. The
surface maps of these elements reconstructed with the Doppler imaging
technique show a relative underabundance on the hemisphere facing the
secondary component. The contrast of chemical inhomogeneities ranges
from 0.4 for Ti to 0.8 for Ba. Based on observations collected
at the European Southern Observatory, Chile (ESO program 084.D-0338).
Title: First Detection of Linear Polarization in the Line Profiles
of Active Cool Stars
Authors: Kochukhov, O.; Makaganiuk, V.; Piskunov, N.; Snik, F.;
Jeffers, S. V.; Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.;
Valenti, J. A.
Bibcode: 2011ApJ...732L..19K
Altcode: 2011arXiv1103.6028K
The application of high-resolution spectropolarimetry has led to major
progress in understanding the magnetism and activity of late-type
stars. During the last decade, magnetic fields have been discovered and
mapped for many types of active cool stars using spectropolarimetric
data. However, these observations and modeling attempts are
fundamentally incomplete since they are based on the interpretation of
the circular polarization alone. Taking advantage of the newly built
HARPS polarimeter, we have obtained the first systematic observations
of several cool active stars in all four Stokes parameters. Here we
report the detection of magnetically induced linear polarization for
the primary component of the very active RS CVn binary HR 1099 and
for the moderately active K dwarf ɛ Eri. For both stars the amplitude
of linear polarization signatures is measured to be ~10-4
of the unpolarized continuum, which is approximately a factor of 10
lower than for circular polarization. This is the first detection of
the linear polarization in line profiles of cool active stars. Our
observations of the inactive solar-like star α Cen A show neither
circular nor linear polarization above the level of ~10-5,
indicating the absence of a net longitudinal magnetic field stronger
than 0.2 G. Based on observations obtained at the European Southern
Observatory (ESO programs 083.D-1000(A) and 084.D-0338(A)).
Title: The HARPS Polarimeter
Authors: Snik, F.; Kochukhov, O.; Piskunov, N.; Rodenhuis, M.; Jeffers,
S.; Keller, C.; Dolgopolov, A.; Stempels, E.; Makaganiuk, V.; Valenti,
J.; Johns-Krull, C.
Bibcode: 2011ASPC..437..237S
Altcode: 2010arXiv1010.0397S
We recently commissioned the polarimetric upgrade of the HARPS
spectrograph at ESO's 3.6-m telescope at La Silla, Chile. The HARPS
polarimeter is capable of full Stokes spectropolarimetry with large
sensitivity and accuracy, taking advantage of the large spectral
resolution and stability of HARPS. In this paper we present the
instrument design and its polarimetric performance. The first HARPSpol
observations show that it can attain a polarimetric sensitivity
of ∼10-5 (after addition of many lines) and that no
significant instrumental polarization effects are present.
Title: The effect of M dwarf starspot activity on low-mass planet
detection thresholds
Authors: Barnes, J. R.; Jeffers, S. V.; Jones, H. R. A.
Bibcode: 2011MNRAS.412.1599B
Altcode: 2010arXiv1011.1125B; 2011MNRAS.tmp..309B
In light of the growing interest in searching for low mass, rocky
planets, we investigate the impact of starspots on radial velocity
searches for earth-mass planets in orbit about M dwarf stars. Since
new surveys targeting M dwarfs will likely be carried out at infrared
wavelengths, a comparison between V and Y band starspot-induced jitter
is made, indicating a reduction of up to an order of magnitude when
observing in the Y band. The exact reduction in jitter is dependent
on the photosphere to spot contrast ratio, with greater improvements
at smaller contrasts. We extrapolate a model used to describe
solar spot distributions to simulate the spot patterns that we expect
to find on M dwarfs. Under the assumption that M dwarfs are near or
fully convective, we randomly place starspots on the stellar surface,
simulating different levels of spot coverage. Line profiles distorted
by spots are derived and are used to investigate the starspot-induced
jitter. By making assumptions about the degree of spot activity,
detection limits for earth-mass planets in habitable zones are simulated
for between 10 and 500 observation epochs. We find that ≤50 epochs
are required to detect 1-2 ? planets (with <1 per cent false alarm
probability) orbiting slowly rotating 0.1 and 0.2 M⊙
stars. This sensitivity decreases when typical rotation velocities and
activity levels for each stellar mass/spectral type are considered. No
detections of below 20 ? planets are expected for ≤500 observations
for the most active stars with v sin i≥ 20 km s-1 and
dark spots.
Title: HARPSpol — The New Polarimetric Mode for HARPS
Authors: Piskunov, N.; Snik, F.; Dolgopolov, A.; Kochukhov, O.;
Rodenhuis, M.; Valenti, J.; Jeffers, S.; Makaganiuk, V.; Johns-Krull,
C.; Stempels, E.; Keller, C.
Bibcode: 2011Msngr.143....7P
Altcode:
The HARPS spectrograph can now perform a full polarisation analysis
of spectra. It has been equipped with a polarimetric unit, HARPSpol,
which was jointly designed and produced by Uppsala, Utrecht and Rice
Universities and by the STScI. Here we present the new instrument,
demonstrate its polarisation capabilities and show the first scientific
results.
Title: Observations of non-solar-type dynamo processes in stars with
shallow convective zones
Authors: Jeffers, S. V.; Donati, J. -F.; Alecian, E.; Marsden, S. C.
Bibcode: 2011MNRAS.411.1301J
Altcode: 2010MNRAS.tmp.1830J
The magnetic field topology and differential rotation are fundamental
signatures of the dynamo processes that generate the magnetic activity
observed in the Sun and solar-type stars. To investigate how these
dynamo processes evolve in stars with shallow convective zones,
we present high-resolution spectropolarimetric observations of the
young GO dwarf HD 171488 over three epochs. Using the Zeeman-Doppler
tomographic imaging technique, we have reconstructed surface brightness
images that are dominated by polar and high-latitude starspots and a
magnetic field topology that shows large-scale radial and azimuthal
magnetic field components. Over the time-span of our observations,
we do not observe a reversal of the magnetic field polarity as has
been observed in other solar-type stars with shallow convective
zones. The phase coverage of our data was sufficient to determine
the differential rotation for two epochs where in conjunction with
previous work, we conclude that there is no evidence for the temporal
evolution of differential rotation. Spectropolarimetric observations
were obtained, from 2007 May 21-26, 2007 November 8-13 and 2008 May
26-30 with the NARVAL echelle spectropolarimeter at the Telescope
Bernard Lyot (Observatoire du Pic du Midi, France).
Title: The search for magnetic fields in mercury-manganese stars
Authors: Makaganiuk, V.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.;
Johns-Krull, C. M.; Keller, C. U.; Rodenhuis, M.; Snik, F.; Stempels,
H. C.; Valenti, J. A.
Bibcode: 2011A&A...525A..97M
Altcode: 2010arXiv1010.3931M
Context. A subclass of the upper main-sequence chemically peculiar
stars, mercury-manganese (HgMn) stars were traditionally considered to
be non-magnetic, showing no evidence of variability in their spectral
line profiles. However, discoveries of chemical inhomogeneities on
their surfaces imply that this assumption should be investigated. In
particular, spectroscopic time-series of AR Aur, α And, and five other
HgMn stars indicate the presence of chemical spots. At the same time,
no signatures of global magnetic fields have been detected.
Aims: We attempt to understand the physical mechanism that causes the
formation of chemical spots in HgMn stars and gain insight into the
potential magnetic field properties at their surfaces; we performed a
highly sensitive search for magnetic fields for a large set of HgMn
stars.
Methods: With the aid of a new polarimeter attached
to the HARPS spectrometer at the ESO 3.6 m-telescope, we obtained
high-quality circular polarization spectra of 41 single and double HgMn
stars. Using a multi-line analysis technique on each star, we co-added
information from hundreds of spectral lines to ensure significantly
greater sensitivity to the presence of magnetic fields, including very
weak fields.
Results: For the 47 individual objects studied,
including six components of SB2 systems, we do not detect any magnetic
fields at greater than the 3σ level. The lack of detection in the
circular polarization profiles indicates that if strong fields are
present on these stars, they must have complex surface topologies. For
simple global fields, our detection limits imply upper limits to the
fields present of 2-10 Gauss in the best cases.
Conclusions:
We conclude that HgMn stars lack large-scale magnetic fields, which
is typical of spotted magnetic Ap stars, of sufficient strength to
form and sustain the chemical spots observed on HgMn stars. Our study
confirms that in addition to magnetically altered atomic diffusion,
there exists another differentiation mechanism operating in the
atmospheres of late-B main sequence stars that can produce compositional
inhomogeneities on their surfaces. Based on observations collected
at the European Southern Observatory, Chile (ESO programs 083.D-1000,
084.D-0338, 085.D-0296).Figure 5 is only available in electronic form
at http://www.aanda.org
Title: Multi-Spacecraft Analysis with Generic Visualization Tools
Authors: Mukherjee, J.; Vela, L.; Gonzalez, C.; Jeffers, S.
Bibcode: 2010AGUFMSM31A1849M
Altcode:
To handle the needs of scientists today and in the future, software
tools are going to have to take better advantage of the currently
available hardware. Specifically, computing power, memory, and disk
space have become cheaper, while bandwidth has become more expensive due
to the explosion of online applications. To overcome these limitations,
we have enhanced our Southwest Data Display and Analysis System
(SDDAS) to take better advantage of the hardware by utilizing threads
and data caching. Furthermore, the system was enhanced to support a
framework for adding data formats and data visualization methods without
costly rewrites. Visualization tools can speed analysis of many common
scientific tasks and we will present a suite of tools that encompass the
entire process of retrieving data from multiple data stores to common
visualizations of the data. The goals for the end user are ease of
use and interactivity with the data and the resulting plots. The data
can be simultaneously plotted in a variety of formats and/or time and
spatial resolutions. The software will allow one to slice and separate
data to achieve other visualizations. Furthermore, one can interact
with the data using the GUI or through an embedded language based on
the Lua scripting language. The data presented will be primarily from
the Cluster and Mars Express missions; however, the tools are data
type agnostic and can be used for virtually any type of data.
Title: Imaging polarimetry of circumstellar environments with the
Extreme Polarimeter
Authors: Rodenhuis, M.; Canovas, H.; Jeffers, S. V.; Min, M.; Keller,
C. U.
Bibcode: 2010lyot.confE..20R
Altcode:
Three successful observation campaigns have been conducted with
the Extreme Polarimeter, an imaging polarimeter for the study of
circumstellar environments in scattered light at visible wavelengths. A
contrast ratio between the central star and the circumstellar source
of 10-5 can be achieved with polarimetry, with a Lyot coronograph
capable of increasing this contrast by several orders of magnitude. The
instrument currently operates without an adaptive optics system. An
Adaptive Optics system under development for ExPo is expected to
increase the contrast further. The polarimeter uses the dual-beam
exchange technique, in which the two orthogonal polarisation states
are imaged simultaneously after which a polarisation modulator is used
to swap the polarisation states of the two beams before the next image
is taken. The imaging polarimetry technique developed with ExPo will
be used in the polarimetry arm of the EPICS exoplanet characterisation
instrument proposed for the E-ELT. Here we present the results from the
first observation campaigns, highlighting observations of protoplanetary
disks around several young stars. Systematic effects that limit the
polarimetric sensitivity, and the strategies we employ to overcome
them, are discussed in detail. In particular, the advantages of the
dual-beam exchange polarimetry method are demonstrated.
Title: Imaging polarimetry of protoplanetary disks: feasibility
and usability
Authors: Min, M.; Jeffers, S. V.; Rodenhuis, M.; Canovas, H.; Buenzli,
E.; Keller, C. U.; Waters, L. B. F. M.; Dominik, C.
Bibcode: 2010lyot.confE..34M
Altcode:
Imaging polarimetry is one of the most promising tools to map the
structure of faint protoplanetary disks. In this contribution we
discuss the feasibility of imaging polarimetry of protoplanetary
disks and the usability to answer the scientific questions in the
field. From the theoretical side we do this by simulations of disks of
various geometries and dust properties. We model the expected signal and
detailed predictions for current and upcoming imaging polarimeters. This
way we can address the question what the diagnostic value of polarimetry
is for the structure of the disk and the characteristics of the grains
in it. We compare extremely fluffy aggregated grains and compact
homogeneous grains and show that their expected signal is significantly
different. In combination with infrared/mm observations this could
allow us to obtain grain properties in addition to mapping of the
disk geometry. From the observational side we address the issues by
discussing some of the early results from the Extreme Polarimeter
(ExPo). ExPo is a sensitive imaging polarimeter designed to be a
pathfinding instrument for the large imaging polarimetry projects
planned for the VLT and the ELT. Already it proves to be a pioneering
instrument in the field of imaging polarimetry of circumstellar matter.
Title: Light scattering in circumstellar disks
Authors: Min, M.; Jeffers, S. V.
Bibcode: 2010els..conf..166M
Altcode:
No abstract at ADS
Title: Do young Suns undergo magnetic reversals?
Authors: Marsden, Stephen C.; Jeffers, Sandra V.; Donati,
Jean-Francois; Mengel, Matthew W.; Waite, Ian A.; Carter, Brad D.
Bibcode: 2010IAUS..264..130M
Altcode:
A key part of the modern-day regenerative solar magnetic dynamo is the
reversal of the Sun's global magnetic field every eleven years. However,
recent theoretical models indicate that young-rapidly rotating Sun-like
stars may not always undergo full magnetic reversals, but instead may
sometimes undergo “attempted” reversals where the magnetic field
declines in strength only to return with the same polarity. Using the
technique of Zeeman Doppler imaging we have mapped the magnetic field
topology of a small sample of young Sun-like stars at multiple epochs,
and present tentative evidence of an “attempted” magnetic field
reversal on one of our stars.
Title: Polarimetric Measurements of Protoplanetary Disks with ExPo
Authors: Canovas, H.; Rodenhuis, M.; Jeffers, S. V.; Keller, C. U.
Bibcode: 2009AIPC.1158..381C
Altcode:
Polarimetry is a powerful tool for detecting and characterizing
exoplanets and protoplanetary disks as light scattered from
circumstellar material is linearly polarized. We present the first
light results of ExPo (Extreme Polarimeter) [1], a sensitive imaging
polarimeter developed at Utrecht University that works in the
visible part of the spectrum. Our first light observations at the
4.2-meter William Herschel Telescope (WHT) show that ExPo can reach
the high-contrast ratios that are necessary to observe protoplanetary
disks. We present images of the protoplanetary disks around the Herbig
Ae star AB Aurigae and the T Tauri star SU Aurigae. Our results show
the power of polarimetry for future projects e.g. the ZIMPOL arm of
SPHERE, and the EPOL part of EPICS.
Title: Why are Some A Stars Magnetic, while Most are Not?
Authors: Wade, G. A.; Silvester, J.; Bale, K.; Johnson, N.; Power, J.;
Aurière, M.; Ligniéres, F.; Dintrans, B.; Donati, J. -F.; Hui Bon
Hoa, A.; Mouillet, D.; Naseri, S.; Paletou, F.; Petit, P.; Rincon, F.;
Toque, N.; Bagnulo, S.; Folsom, C. P.; Landstreet, J. D.; Gruberbauer,
M.; Lueftinger, T.; Jeffers, S. V.; Lèbre, A.; Marsden, S. C.
Bibcode: 2009ASPC..405..499W
Altcode:
A small fraction of intermediate-mass main sequence (A and B type)
stars have strong, organised magnetic fields. The large majority
of such stars, however, show no evidence for magnetic fields, even
when observed with very high precision. In this paper we describe a
simple model, motivated by qualitatively new observational results,
that provides a natural physical explanation for the small fraction
of observed magnetic stars.
Title: Differential Rotation on Early G Dwarfs
Authors: Jeffers, S. V.; Donati, J. -F.
Bibcode: 2009ASPC..405..523J
Altcode:
In this paper we present the latest results in our long-term program
to understand how differential rotation depends on fundamental stellar
parameters such as spectral type, mass and radius. In this paper we
focus on early G dwarf spectral types by presenting our latest surface
brightness image and differential rotation measurement for the GOV dwarf
HD 171488 (age = 30 to 50 Myr, period = 1.33 d) and compare with the
differential rotation measurements obtained using the same techniques
for LQ Lup (G2V, 25Myr, p=0.31 d) and R58 (G2V, 35Myr, p=0.57 d).
Title: An analytical model to demonstrate the reliability of
reconstructed `active longitudes'.
Authors: Jeffers, S. V.; Keller, C. U.
Bibcode: 2009AIPC.1094..664J
Altcode: 2009csss...15..664J
Photometric light curves show apparent spot concentrations separated
by 180 degrees in longitude that are commonly referred to as `active
longitudes'. These spot concentrations have been observed to change in
strength resulting in the `flip-flop' effect. We use a simple analytical
model to calculate the light curve of a star with an arbitrary spot
pattern to show that `active longitudes' are a likely consequence of
the limited information content contained in a light curve. We also
show that the same effects apply to heavily spotted stars.
Title: High levels of surface differential rotation on the young G0
dwarf HD171488
Authors: Jeffers, S. V.; Donati, J. -F.
Bibcode: 2008MNRAS.390..635J
Altcode: 2008MNRAS.tmp.1065J
We present high-resolution images of the young, rapidly rotating G0
dwarf HD171488, using both Stokes I and Stokes V data. The observations
were secured with the MuSiCoS spectropolarimeter at Telescope
Bernard Lyot from 2005 May 31 to June 10. The photospheric surface
brightness distributions show a strong and slightly decentred polar
cap that dominates over weak high- and low-latitude spot features. The
large-scale magnetic field topology shows a strong ring of anticlockwise
azimuthal field with a latitudinal dependence on polarity and large
regions of radial field with negative polarity at all latitudes. Using
the good phase coverage of our data, we measure the differential
rotation on HD171488. The results indicate that the equator laps the
pole every 12 days for brightness data and 13 days for magnetic data,
which is the highest measurement of differential rotation obtained
using Zeeman-Doppler imaging techniques. Spectropolarimetric
observations were obtained, from 2005 May 31 to June 10, with the
MuSiCoS echelle spectropolarimeter at the Telescope Bernard Lyot
(Observatoire du Pic du Midi, France). E-mail: s.v.jeffers@uu.nl
Title: The upgrade of HARPS to a full-Stokes high-resolution
spectropolarimeter
Authors: Snik, Frans; Jeffers, Sandra; Keller, Christoph; Piskunov,
Nikolai; Kochukhov, Oleg; Valenti, Jeff; Johns-Krull, Christopher
Bibcode: 2008SPIE.7014E..0OS
Altcode: 2008SPIE.7014E..22S
We present the design of a compact module that converts the HARPS
instrument at the 3.6-m telescope at La Silla to a full-Stokes
high-resolution spectropolarimeter. The polarimeter will replace the
obsolete Iodine cell inside the HARPS Cassegrain adapter. Utilizing
the two fibers going into the spectrograph, two dual-beam systems
can be positioned in the beam: one with a rotating superachromatic
quarter-wave plate for circular polarimetry and one with a rotating
superachromatic half-wave plate for linear polarimetry. A large
polarimetric precision is ensured by the beam-exchange technique
and a minimal amount of instrumental polarization. The polarimeter,
in combination with the ultra-precise HARPS spectrograph, enables
unprecedented observations of stellar magnetic fields and circumstellar
material without compromising the successful planet-finding program.
Title: The Extreme Polarimeter (ExPo): design of a sensitive imaging
polarimeter
Authors: Rodenhuis, M.; Canovas, H.; Jeffers, S. V.; Keller, C. U.
Bibcode: 2008SPIE.7014E..6TR
Altcode: 2008SPIE.7014E.227R
The Extreme Polarimeter (ExPo) is approaching its first deployment
at the 4.2 m William Herschel Telescope at La Palma. This imaging
polarimeter, developed at the Astronomical Institute of Utrecht
University, aims to study circumstellar material at a contrast
ratio with the central star of 10-9. Working at visible
wavelengths, it will provide an inner working angle down to 0.5
arcsec and a field of view of 20 arcsec diameter. ExPo employs a
dual beam-exchange technique based on polarimeter designs for solar
studies. A partially transmitting coronagraph mask placed in the first
focus reduces the light of the star. The beam is modulated using three
ferro-electric liquid crystals in a Pancharatnam configuration, then
split in a polarizing beamsplitter. Both beams are re-imaged onto
the same Electron-Multiplying CCD camera. We present the design of
the ExPo instrument, highlighting the elements that are critical to
the polarimetric performance. Some prototype laboratory experiments
demonstrating the instrument concept are discussed. These have been
performed using our realistic exoplanet laboratory simulator.
Title: Design of a laboratory simulator to test exoplanet imaging
polarimetry
Authors: Jeffers, S. V.; Miesen, N.; Rodenhuis, M.; Keller, C. U.
Bibcode: 2008SPIE.7014E..7BJ
Altcode: 2008SPIE.7014E.239J
Research on extrasolar planets is one of the most rapidly advancing
fields of astrophysics. In just over a decade since the discovery of
the first extra-solar planet orbiting around 51 Pegasi, 289 extrasolar
planets have been discovered. This breakthrough is the result of
the development of a wide range of new observational techniques
and facilities for the detection and characterisation of extrasolar
planets. In Utrecht we are building the Extreme Polarimeter (ExPo)
to image extra-solar planets and circumstellar environments using
polarimetry at contrast ratio of 10-9. To test and calibrate
ExPo, we have built a laboratory-based simulator that mimics a star
with a Jupiter-like exoplanet as seen by the 4.2m William Herschel
Telescope. The star and planet are simulated using two single-mode
fibres in close proximity that are fed with a broadband arc lamp with a
contrast ratio down to 10-9. The planet is partially linearly
polarized. The telescope is simulated with two lenses, and seeing can
be included with a rotating glass plate covered with hairspray. In this
paper we present the scientific requirements and the simulator design.
Title: Next Generation Science Analysis Tools for the Desktop
Authors: Mukherjee, J.; Gonzalez, C.; Vela, L.; Jeffers, S.
Bibcode: 2008AGUSMSM21A..06M
Altcode:
With the coming evolution of a more inclusive and extensive heliophysics
data environment, the need for tools which can make use of them is far
greater. Furthermore, average desktop computers are becoming extremely
powerful. Most modern computers are equipped with multiple processors,
or at the very least, multiple cores to offer significant advantages
over the computers of just a few years back. However, due to the effort
involved, very little software is able to take full advantage of these
new technologies. We have developed software which marries the latest
in desktop advancements with certain aspects of the up and coming
data environment. Our current focus is visualization and prototype
tools that have been written to more easily download, visualize, and
manipulate data. For this paper, we will discuss the architecture of
the system and how this can make for more effective science along with
our plans for the future.
Title: Weak magnetic fields in Ap/Bp stars. Evidence for a dipole
field lower limit and a tentative interpretation of the magnetic
dichotomy
Authors: Aurière, M.; Wade, G. A.; Silvester, J.; Lignières, F.;
Bagnulo, S.; Bale, K.; Dintrans, B.; Donati, J. F.; Folsom, C. P.;
Gruberbauer, M.; Hui Bon Hoa, A.; Jeffers, S.; Johnson, N.; Landstreet,
J. D.; Lèbre, A.; Lueftinger, T.; Marsden, S.; Mouillet, D.; Naseri,
S.; Paletou, F.; Petit, P.; Power, J.; Rincon, F.; Strasser, S.;
Toqué, N.
Bibcode: 2007A&A...475.1053A
Altcode: 2007arXiv0710.1554A
Aims:We investigated a sample of 28 well-known
spectroscopically-identified magnetic Ap/Bp stars, with weak,
poorly-determined or previously undetected magnetic fields. The
aim of this study is to explore the weak part of the magnetic field
distribution of Ap/Bp stars.
Methods: Using the MuSiCoS and
NARVAL spectropolarimeters at Télescope Bernard Lyot (Observatoire
du Pic du Midi, France) and the cross-correlation technique Least
Squares Deconvolution (LSD), we obtained 282 LSD Stokes V signatures
of our 28 sample stars, in order to detect the magnetic field and
to infer its longitudinal component with high precision (median
σ=40 G).
Results: For the 28 studied stars, we obtained
27 detections of Stokes V Zeeman signatures from the MuSiCoS
observations. Detection of the Stokes V signature of the 28th star
(HD 32650) was obtained during science demonstration time of the new
NARVAL spectropolarimeter at Pic du Midi. This result clearly shows
that when observed with sufficient precision, all firmly classified
Ap/Bp stars show detectable surface magnetic fields. Furthermore,
all detected magnetic fields correspond to longitudinal fields which
are significantly greater than some tens of G. To better characterise
the surface magnetic field intensities and geometries of the sample,
we phased the longitudinal field measurements of each star using
new and previously-published rotational periods, and modeled them to
infer the dipolar field intensity (B_d, measured at the magnetic pole)
and the magnetic obliquity (β). The distribution of derived dipole
strengths for these stars exhibits a plateau at about 1 kG, falling off
to larger and smaller field strengths. Remarkably, in this sample of
stars selected for their presumably weak magnetic fields, we find only
2 stars for which the derived dipole strength is weaker than 300 G. We
interpret this “magnetic threshold” as a critical value necessary
for the stability of large-scale magnetic fields, and develop a simple
quantitative model that is able to approximately reproduce the observed
threshold characteristics. This scenario leads to a natural explanation
of the small fraction of intermediate-mass magnetic stars. It may also
explain the near-absence of magnetic fields in more massive B and O-type
stars. Based on data obtained using the Télescope Bernard Lyot
at Observatoire du Pic du Midi, CNRS and Université Paul Sabatier,
France. Figures 7 to 32 are only available in electronic form at
http://www.aanda.org Table 3 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/475/1053
Title: Why are some A stars magnetic, while most are not?
Authors: Wade, G. A.; Silvester, J.; Bale, K.; Johnson, N.; Power, J.;
Aurière, M.; Ligniéres, F.; Dintrans, B.; Donati, J. -F.; Bon Hoa,
A. Hui; Mouillet, D.; Naseri, S.; Paletou, F.; Petit, P.; Rincon, F.;
Toque, N.; Bagnulo, S.; Folsom, C. P.; Landstreet, J. D.; Gruberbauer,
M.; Lueftinger, T.; Jeffers, S.; Lèbre, A.; Marsden, S.
Bibcode: 2007arXiv0712.3614W
Altcode:
A small fraction of intermediate-mass main sequence (A and B type)
stars have strong, organised magnetic fields. The large majority
of such stars, however, show no evidence for magnetic fields, even
when observed with very high precision. In this paper we describe a
simple model, motivated by qualitatively new observational results,
that provides a natural physical explanation for the small fraction
of observed magnetic stars.
Title: Magnetic fields and accretion flows on the classical T Tauri
star V2129 Oph
Authors: Donati, J. -F.; Jardine, M. M.; Gregory, S. G.; Petit, P.;
Bouvier, J.; Dougados, C.; Ménard, F.; Collier Cameron, A.; Harries,
T. J.; Jeffers, S. V.; Paletou, F.
Bibcode: 2007MNRAS.380.1297D
Altcode: 2007MNRAS.tmp..760D; 2007arXiv0709.1414D
From observations collected with the ESPaDOnS spectropolarimeter, we
report the discovery of magnetic fields at the surface of the mildly
accreting classical T Tauri star (cTTS) V2129 Oph. Zeeman signatures
are detected, both in photospheric lines and in the emission lines
formed at the base of the accretion funnels linking the disc to the
protostar, and monitored over the whole rotation cycle of V2129 Oph. We
observe that rotational modulation dominates the temporal variations
of both unpolarized and circularly polarized line profiles. We
reconstruct the large-scale magnetic topology at the surface of V2129
Oph from both sets of Zeeman signatures simultaneously. We find it
to be rather complex, with a dominant octupolar component and a weak
dipole of strengths 1.2 and 0.35 kG, respectively, both slightly tilted
with respect to the rotation axis. The large-scale field is anchored in
a pair of 2-kG unipolar radial field spots located at high latitudes
and coinciding with cool dark polar spots at photospheric level. This
large-scale field geometry is unusually complex compared to those of
non-accreting cool active subgiants with moderate rotation rates. As an illustration, we provide a first attempt at modelling the
magnetospheric topology and accretion funnels of V2129 Oph using
field extrapolation. We find that the magnetosphere of V2129 Oph
must extend to about 7R* to ensure that the footpoints
of accretion funnels coincide with the high-latitude accretion
spots on the stellar surface. It suggests that the stellar magnetic
field succeeds in coupling to the accretion disc as far out as the
corotation radius, and could possibly explain the slow rotation of V2129
Oph. The magnetospheric geometry we derive qualitatively reproduces the
modulation of Balmer lines and produces X-ray coronal fluxes typical
of those observed in cTTSs. Based on observations obtained at
the Canada-France-Hawaii Telescope (CFHT) which is operated by the
National Research Council of Canada, the Institut National des Sciences
de l'Univers of the Centre National de la Recherche Scientifique of
France, and the University of Hawaii. E-mail: donati@ast.obs-mip.fr
(J-FD); mmj@st-andrews.ac.uk (MMJ); sg64@st-andrews.ac.uk (SGG);
petit@ast.obs-mip.fr (PP); jerome.bouvier@obs.ujf-grenoble.fr
(JB); catherine.dougados@obs.ujf-grenoble.fr (CD);
francois.menard@obs.ujf-grenoble.fr (FM); acc4@st-andrews.ac.uk
(ACC); th@astro.ex.ac.uk (TJH); s.v.jeffers@phys.uu.nl (SVJ);
fpaletou@ast.obs-mip.fr (FP)
Title: VizieR Online Data Catalog: Magnetic fields in Ap/Bp stars
(Auriere+, 2007)
Authors: Auriere, M.; Wade, G. A.; Silvester, J.; Lignieres, F.;
Bagnulo, S.; Bale, K.; Dintrans, B.; Donati, J. F.; Folsom, C. P.;
Gruberbauer, M.; Hui Bon Hoa, A.; Jeffers, S.; Johnson, N.; Landstreet,
J. D.; Lebre, A.; Lueftinger, T.; Marsden, S.; Mouillet, D.; Naseri,
S.; Paletou, F.; Petit, P.; Power, J.; Rincon, F.; Strasser, S.;
Toque, N.
Bibcode: 2007yCat..34751053A
Altcode:
We have investigated a sample of 28 well-known
spectroscopically-identified magnetic Ap/Bp stars, with weak,
poorly-determined or previously undetected magnetic fields. The
aim of this study is to explore the weak part of the magnetic
field distribution of Ap/Bp stars. Using the MuSiCoS and NARVAL
spectropolarimeters at Telescope Bernard Lyot (Observatoire du Pic
du Midi, France) and the cross-correlation technique Least Squares
Deconvolution (LSD), we have obtained 282 LSD Stokes $V$ signatures of
our 28 sample stars, in order to detect the magnetic field and to infer
its longitudinal component with high precision (median sigma=40G). (2 data files).
Title: Science Goals of the Extreme Polarimeter (ExPo)
Authors: Jeffers, S. V.; Keller, C. U.; Rodenhuis, M.; Miesen, N.
Bibcode: 2007lyot.confE..42J
Altcode:
To advance our understanding of the formation, evolution and structure
of extra-solar planetary systems we are building a high-precision
imaging polarimeter (ExPo). ExPo will initially be located at the 4.2m
William Herschel Telescope on La Palma. We will use polarimetric
techniques similar to those developed for high-precision solar
polarimetry to reach a sensitivity of 10^-5, to polarimetrically
image and characterize planets and protoplanetary debris discs. I will
present a review of the proposed data analysis techniques and science
goals that will be achievable using the significant improvement in
polarimetric imaging capabilities.
Title: Magnetic activity on AB Doradus: temporal evolution of
star-spots and differential rotation from 1988 to 1994
Authors: Jeffers, S. V.; Donati, J. -F.; Collier Cameron, A.
Bibcode: 2007MNRAS.375..567J
Altcode: 2007MNRAS.tmp.1492J; 2006astro.ph.10259J
Surface brightness maps for the young K0 dwarf AB Doradus are
reconstructed from archival data sets for epochs spanning from 1988
to 1994. By using the signal-to-noise ratio enhancement technique of
least-squares deconvolution, our results show a greatly increased
resolution of spot features than obtained in previously published
surface brightness reconstructions. These images show that for the
exception of epoch 1988.96, the star-spot distributions are dominated
by a long-lived polar cap, and short-lived low to high-latitude
features. The fragmented polar cap at epoch 1988.96 could indicate a
change in the nature of the dynamo in the star. For the first time we
measure differential rotation for epochs with sufficient phase coverage
(1992.05, 1993.89, 1994.87). These measurements show variations on a
time-scale of at least 1 year, with the strongest surface differential
rotation ever measured for AB Dor occurring in 1994.86. In conjunction
with previous investigations, our results represent the first long-term
analysis of the temporal evolution of differential rotation on active
stars.
Title: A Spectro-Polarimetric Survey of the Coolest Magnetic Ap Stars
Authors: Johnson, N.; Wade, G. A.; Allen, A.; Folsom, C.; Welland,
M.; Aurière, M.; Donati, J. -F.; Jeffers, S.; Lignires, F.; Marsden,
S.; Mouillet, D.; Paletou, F.; Petit, P.; Toqué, N.; Bagnulo, S.;
Landstreet, J. D.; Lüftinger, T.; Ryabchikova, T.
Bibcode: 2006ASPC..358..393J
Altcode:
This article describes the first results of a systematic
spectro-polarimetric survey of the coolest magnetic Ap stars, undertaken
with the MuSiCoS spectro-polarimeter, with the aim of clarifying the
magnetic field and atmospheric characteristics of these enigmatic
objects.
Title: Modelling Eclipsing Binaries with Dense Spot Coverage
Authors: Jeffers, S. V.
Bibcode: 2006Ap&SS.304..153J
Altcode: 2006Ap&SS.tmp...96J
To synthesise images of stellar photospheres with high spot filling
factors, we model an extrapolated solar size distribution of
spots on an immaculate SV Cam. These models of starspot coverage
show that the primary star is peppered with a large number of
subresolution spots. Using these model starspot distributions we
generate a photometric lightcurve, which is then used as input to an
maximum-entropy eclipse mapping code, that is based on chi-squared
minimisation. I solve for the system parameters to show the effect of
dense spot coverage on the derived system parameters, and show that
surface brightness distributions reconstructed from these lightcurves
have distinctive spots on the primary star at its quadrature points. It
is concluded that two-spot modelling or chi-squared minimisation
techniques are more susceptible to spurious structures being
generated by systematic errors, arising from incorrect assumptions
about photospheric surface brightness, than simple Fourier analysis
of the light-curves.
Title: Dense Spot Coverage and Polar Caps on SV Cam
Authors: Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R.;
Aufdenberg, J. P.
Bibcode: 2006Ap&SS.304..371J
Altcode: 2006Ap&SS.tmp..109J
We have used spectrophotometric data from nine Hubble Space Telescope
orbits to eclipse-map the primary component of the RS CVn binary SV
Cam. From these observations and its HIPPARCOS parallax we find that
the surface flux in the eclipsed low-latitude region is about 30 % lower
than computed from the best fitting PHOENIX model atmosphere. This flux
deficit can only be accounted for if about a third of the primary's
surface is covered with unresolved spots. Even when we extend the
spottedness from the eclipsed region to the entire surface, there
still remains an unaccounted flux deficit. This remaining flux deficit
is explained by the presence of a large polar spot extending down to
latitude 42 ±6 °.
Title: Hubble Space Telescope observations of SV Cam - II. First
derivative light-curve modelling using PHOENIX and ATLAS model
atmospheres
Authors: Jeffers, S. V.; Aufdenberg, J. P.; Hussain, G. A. J.;
Collier Cameron, A.; Holzwarth, V. R.
Bibcode: 2006MNRAS.367.1308J
Altcode: 2006MNRAS.tmp..249J; 2006astro.ph..2048J
The variation of the specific intensity across the stellar disc is
an essential input parameter in surface brightness reconstruction
techniques such as Doppler imaging, where the relative intensity
contributions of different surface elements are important in detecting
star-spots. We use PHOENIX and ATLAS model atmospheres to model
light curves derived from high precision (signal-to-noise ratio ~=
5000) Hubble Space Telescope (HST) data of the eclipsing binary SV
Cam (F9V+K4V), where the variation of specific intensity across the
stellar disc will determine the contact points of the binary system
light curve. For the first time, we use χ2 comparison fits
to the first derivative profiles to determine the best-fitting model
atmosphere. We show the wavelength dependence of the limb darkening and
that the first derivative profile is sensitive to the limb-darkening
profile very close to the limb of the primary star. It is concluded that
there is only a marginal difference (<1σ) between the χ2
comparison fits of the two model atmospheres to the HST light curve
at all wavelengths. The usefulness of the second derivative of the
light curve for measuring the sharpness of the primary's limb is
investigated, but we find that the data are too noisy to permit a
quantitative analysis.
Title: Hubble Space Telescope observations of SV Cam - I. The
importance of unresolved star-spot distributions in light-curve
fitting
Authors: Jeffers, S. V.; Barnes, J. R.; Collier Cameron, A.; Donati,
J. -F.
Bibcode: 2006MNRAS.366..667J
Altcode: 2006MNRAS.tmp...64J; 2006astro.ph..2050J
We have used maximum entropy eclipse-mapping to recover images of the
visual surface brightness distribution of the primary component of the
RS CVn eclipsing binary SV Cam, using high-precision photometry data
obtained during three primary eclipses with Space Telescope Imaging
Spectrograph aboard the Hubble Space Telescope (HST). These were
augmented by contemporaneous ground-based photometry secured around
the rest of the orbit. The goal of these observations was to determine
the filling factor and size distribution of star-spots too small to
be resolved by Doppler imaging. The information content of the final
image and the fit to the data were optimized with respect to various
system parameters using the χ2 landscape method, using
an eclipse-mapping code that solves for large-scale spot coverage. It
is only with the unprecedented photometric precision of the HST data
(0.00015mag) that it is possible to see strong discontinuities at
the four contact points in the residuals of the fit to the light
curve. These features can only be removed from the residual light curve
by the reduction of the photospheric temperature, to synthesize high
unresolvable spot coverage, and the inclusion of a polar spot. We show
that this spottedness of the stellar surface can have a significant
impact on the determination of the stellar binary parameters and the
fit to the light curve by reducing the secondary radius from 0.794
+/- 0.009 to 0.727 +/- 0.009Rsolar. This new technique
can also be applied to other binary systems with high-precision
spectrophotometric observations.
Title: Spurious `active longitudes' in parametric models of heavily
spotted eclipsing binaries
Authors: Jeffers, S. V.
Bibcode: 2005MNRAS.359..729J
Altcode: 2005astro.ph..4637J; 2005MNRAS.tmp..319J
In this paper, the size distributions of starspots extrapolated from
the case of the Sun are modelled on the eclipsing binary SV Cam to
synthesize images of stellar photospheres with high spot filling
factors. These spot distributions pepper the primary's surface
with spots, many of which are below the resolution capabilities of
eclipse-mapping and Doppler-imaging techniques. The light curves
resulting from these modelled distributions are used to determine the
limitations of image reconstruction from photometric data. Surface
brightness distributions reconstructed from these light curves show
distinctive spots on the primary star at its quadrature points. It
is concluded that two-spot modelling or chi-squared minimization
techniques are more susceptible to spurious structures being
generated by systematic errors, arising from incorrect assumptions
about photospheric surface brightness, than simple Fourier analysis
of the light curves.
Title: Dense spot coverage and polar caps on SV Cam
Authors: Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R.;
Aufdenberg, J. P.; Hussain, G. A. J.
Bibcode: 2005ESASP.560..669J
Altcode: 2005csss...13..669J
No abstract at ADS
Title: Direct Evidence for a Polar Spot on SV Camelopardalis
Authors: Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R.;
Aufdenberg, J. P.; Hussain, G. A. J.
Bibcode: 2005ApJ...621..425J
Altcode: 2005astro.ph..1671J
We have used spectrophotometric data from the Hubble Space Telescope
(HST) to eclipse-map the primary component of the RS CVn binary SV
Cam over nine HST orbits. We find from these observations and the
Hipparcos parallax that the surface flux in the eclipsed low-latitude
region of the primary is about 30% lower than that computed from a
PHOENIX model atmosphere at the effective temperature that best fits
the spectral energy distribution of the eclipsed flux. This can only
be accounted for if about a third of the primary's surface is covered
with unresolved dark starspots. Extending this to the full surface of
the primary, we find that, even taking into account this spot-filling
factor, there is an additional flux deficit on the primary star. This
can only be explained if there is a large polar spot on the primary star
extending from the pole to latitude 48deg+/-6deg.
Title: Surface brightness distributions of late-type stars
Authors: Jeffers, Sandra Victoria
Bibcode: 2005PhDT.......129J
Altcode:
The aim of this work has been to increase our understanding of the
surface brightness distributions of late-type stars through Doppler
imaging and eclipse mapping techniques. Combining spectroscopic
and photometric observations with the technique of Doppler Imaging,
I have reconstructed surface images of the G2V star He 699 (for 08
October 2000), which show high latitude and polar structures. In the
case of the KOV star AB Dor, the Doppler images for January 1992 and
November 1993 show a large polar cap with small dark features also
present at intermediate to high latitudes. As the phase sampling of
the observations was insufficient to apply the sheared-image method it
was not possible to detect any differential rotation. In the second
part of my thesis I determine the surface brightness distribution of
the primary component of the RS CVn eclipsing binary SV Cam. I have
used extrapolated size distributions of sunspots to an active star
to synthesize images of stellar photospheres with high spot filling
factors. The resulting surface images, reconstructed with the Maximum
Entropy eclipse mapping technique, show large spurious spot features
at the quadrature points. It is concluded that two-spot modelling or
chi-squared minimisation techniques are more susceptible to spurious
structures being generated by systematic errors, arising from incorrect
assumptions about photospheric surface brightness, than simple Fourier
analysis of the light-curves. Spectrophotometric data from 9 HST orbits,
observed in November 2001, have been used to eclipse-map the primary
component of SV Cam. In combination with its HIPPAR- COS parallax it
is found that the surface flux in the eclipsed low-latitude region
is about 30% lower than computed from the best fitting PHOENIX model
atmosphere. This flux deficit can only be accounted for if about a third
of the primary's surface is covered with unresolved spots. However,
when the spottedness from the eclipsed region is applied to the entire
surface of the primary star, there still remains an unaccounted flux
deficit. The remaining flux deficit is explained by the presence of a
large polar spot extending down to latitude 48+/-6°. When the Maximum
Entropy eclipse mapping technique is used to fit SV Cam's lightcurve,
the observed minus computed residuals show strong spurious peaks at
the quadrature points. It is only possible to reduce these peaks with
the addition of a polar cap and the reduction of the primary star's
temperature, to account for the star being peppered with unresolvable
spots. Motivated by this result we investigate the limb darkening of
the primary component of SV Cam. The wavelength dependence of the
limb darkening is analysed by sub-dividing the HST lightcurve into
10 bands of equal emission flux. Flux variations between the first
and fourth contact of the primary eclipse indicate that the limb
darkening decreases towards longer wavelengths, in accordance with
published limb darkening laws. Comparing fits of ATLAS and PHOENIX
model atmospheres we find a wavelength dependence of the best fitting
model. Due to its smooth cutoff at the stellar limb, the spherical
geometry of the PHOENIX model atmosphere gives the best fit during
partial eclipse. Between the second and third contact the difference
between spherical and plane-parallel geometry is less important.
Title: Rotational periods of four roAp stars
Authors: Ryabchikova, T.; Wade, G. A.; Aurière, M.; Bagnulo, S.;
Donati, J. -F.; Jeffers, S. V.; Johnson, N.; Landstreet, J. D.;
Lignières, F.; Lueftinger, T.; Marsden, S.; Mouillet, D.; Paletou,
F.; Petit, P.; Reegen, P.; Silvester, J.; Strasser, S.; Toque, N.
Bibcode: 2005A&A...429L..55R
Altcode:
Forty-five new measurements of the mean longitudinal magnetic fields
and mean equivalent widths of 4 roAp stars have obtained using the
MuSiCoS spectropolarimeter at Pic du Midi observatory. These new
high-precision data have been combined with archival measurements
in order to constrain the rotational periods of HD 12098, HD 24712
= HR 1217, HD 122970 and HD 176232 = 10 Aql. We report a revised
rotational period for HD 24712 (Prot = 12.45877 ±
0.00016 d, crucial for interpretation of upcoming MOST observations
of this star), new rotational periods for HD 12098 and HD 122970
(Prot=5.460 ± 0.001 d and Prot=3.877 ± 0.001
d, respectively) and evidence for an extremely long period for HD
176232. Table 1 is only available in electonic 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/429/L55
Title: Substellar companions and isolated planetary-mass objects
from protostellar disc fragmentation
Authors: Rice, W. K. M.; Armitage, P. J.; Bonnell, I. A.; Bate, M. R.;
Jeffers, S. V.; Vine, S. G.
Bibcode: 2003MNRAS.346L..36R
Altcode: 2003astro.ph.10679R
Self-gravitating protostellar discs are unstable to fragmentation
if the gas can cool on a time-scale that is short compared
with the orbital period. We use a combination of hydrodynamic
simulations and N-body orbit integrations to study the long-term
evolution of a fragmenting disc with an initial mass ratio to
the star of Mdisc/M*= 0.1. For a disc that
is initially unstable across a range of radii, a combination of
collapse and subsequent accretion yields substellar objects with
a spectrum of masses extending (for a Solar-mass star) up to ~0.01
Msolar. Subsequent gravitational evolution ejects most of
the lower mass objects within a few million years, leaving a small
number of very massive planets or brown dwarfs in eccentric orbits
at moderately small radii. Based on these results, systems such as HD
168443 - in which the companions are close to or beyond the deuterium
burning limit - appear to be the best candidates to have formed via
gravitational instability. If massive substellar companions originate
from disc fragmentation, while lower-mass planetary companions originate
from core accretion, the metallicity distribution of stars which host
massive substellar companions at radii of ~1 au should differ from
that of stars with lower mass planetary companions.
Title: Dynamo processes and activity cycles of the active stars AB
Doradus, LQ Hydrae and HR 1099
Authors: Donati, J. -F.; Collier Cameron, A.; Semel, M.; Hussain,
G. A. J.; Petit, P.; Carter, B. D.; Marsden, S. C.; Mengel, M.;
López Ariste, A.; Jeffers, S. V.; Rees, D. E.
Bibcode: 2003MNRAS.345.1145D
Altcode:
In this paper, we present new brightness and magnetic surface images of
the young K0 dwarfs AB Doradus and LQ Hydrae, and of the K1 subgiant
of the RS CVn system HR 1099 (=V711 Tauri), reconstructed from
Zeeman-Doppler imaging spectropolarimetric observations collected
at the Anglo-Australian Telescope during five observing campaigns
(totalling 50 nights), from 1998 January to 2002 January. Along with
the older images of the same stars (published in previous papers),
our complete data set represents the first long-term series on temporal
fluctuations of magnetic topologies of very active stars. All of
the magnetic images presented here indicate that large regions with
predominantly azimuthal magnetic fields are continuously present at
the surfaces of these stars. We take this as further evidence that the
underlying dynamo processes that produce them are probably distributed
throughout the entire convective zone (and not confined at its base,
as in the Sun). We speculate that the radial and azimuthal field
maps that we recover correspond, respectively, to the poloidal and
toroidal components of the large-scale dynamo field. We find, in
particular, that some signatures, for instance the relative fraction
of magnetic energy stored in the large-scale poloidal and toroidal
field components, and the polarity of the axisymmetric component of
the field, are variable with time, and provide potentially fruitful
diagnostics for investigating magnetic cycles in active stars other
than the Sun. We report here the detection of partial polarity switches
in some of the axisymmetric field components of two of our programme
stars (AB Dor and LQ Hya), suggesting that the dynamo operating in
these stars may be cyclic.
Title: Latitude Distribution of Star-spots on the G Dwarf He 699
Authors: Jeffers, S. V.; Barnes, J. R.; Cameron, A. D.
Bibcode: 2003csss...12..916J
Altcode:
We analyse the latitude distribution of star-spots on the rapidly
rotating G dwarf He 699. An image was reconstructed from data taken
with the William Herschel Telescope on La Palma on 2000 October 08. The
predominant magnetic field structure is a decentred polar spot at high
latitude, with smaller low latitude features also present. This result
was verified by independent reconstructions using even numbered and
odd numbered spectra. This work confirms and extends that of Barnes
et al.,(2001,MNRAS,326,1057) and provides further evidence that there
is a correlation between the presence of low latitude features and the
amplitude of the photometric lightcurve. It is also a further step in
the search for activity cycles on young G dwarfs.
Title: Theoretical calculation of the cratering on Ida, Mathilde,
Eros and Gaspra
Authors: Jeffers, S. V.; Asher, D. J.
Bibcode: 2003MNRAS.343...56J
Altcode:
The main influences on crater size distributions are investigated by
deriving results for the four example target objects, (951) Gaspra,
(243) Ida, (253) Mathilde and (433) Eros. The dynamical history of
each of these asteroids is modelled using the MERCURY numerical
integrator. An efficient, Öpik-type, collision code enables the
distribution of impact velocities and the overall impact probability
to be found. When combined with a crater scaling law and an impactor
size distribution, using a Monte Carlo method, this yields a crater
size distribution. The cratering time-scale is longer for Ida than
either Gaspra or Mathilde, though it is harder to constrain for Eros
due to the chaotic variation of its orbital elements. The slopes of
the crater size distribution are in accord with observations.
Title: Archival of time-series data at SWRI, MSSL, AND IRF
Authors: Mukherjee, J.; Kalla, L.; Chilson, C.; Jeffers, S.;
Gonzalez, C.
Bibcode: 2003AdSpR..31.1327M
Altcode:
No abstract at ADS
Title: Data Fusion of Multi-Spacecraft Data Using the Example of
Plasma Gradients
Authors: Wüest, M. P.; Jahn, J.; Jeffers, S.
Bibcode: 2002AGUFMSA22A..11W
Altcode:
In coming years we will see an explosion in our need to routinely
perform a complex multi-viewpoint data analysis of space physics
data sets. Orchestrated multi-spacecraft measurements open access
to new physical quantities not accessible with single spacecraft,
and they remove spatio-temporal ambiguities. Our ability to
appropriately analyze data from three-dimensional spacecraft
formations and the proper ingestion of those data into models is
currently underdeveloped. Providing comprehensive data fusion tools
for these new data sets is necessary in order to utilize these data
effectively. We are presenting our system, currently under development,
which is designed to give full access to the three-dimensionality of the
space environment by calculating gradients, divergences and curls from
measurement of vector and scalar quantities performed simultaneously
by identical instruments on multiple satellites. On the local level
this allows to obtain spatial or temporal scales at high resolution
and on a global level this reduces the amount of data considerably
and facilitates the interface with global numerical models.
Title: Theoretical cratering rates on Ida, Mathilde, Eros and Gaspra
Authors: Jeffers, S. V.; Asher, D. J.; Bailey, M. E.
Bibcode: 2002ESASP.500..863J
Altcode: 2002acm..conf..863J
We investigate the main influences on crater size distributions, by
deriving results for the four example target objects, (951) Gaspra,
(243) Ida, (253) Mathilde and (433) Eros. The dynamical history of
each of these asteroids is modelled using the MERCURY (Chambers 1999)
numerical integrator. The use of an efficient, Öpik-type, collision
code enables the calculation of a velocity histogram and the probability
of impact. This when combined with a crater scaling law and an impactor
size distribution, through a Monte Carlo method, results in a crater
size distribution. The resulting crater probability distributions are
in good agreement with observed crater distributions on these asteroids.
Title: The latitude distribution of star-spots on He 699
Authors: Jeffers, S. V.; Barnes, J. R.; Collier Cameron, A.
Bibcode: 2002MNRAS.331..666J
Altcode:
In this paper, the latitude distribution of star-spots is analysed for
the rapidly rotating G dwarf He 699. An image has been reconstructed
from data taken with the William Herschel Telescope on La Palma on 2000
October 8. The predominant magnetic field structure is a decentred
polar spot at high latitude, with smaller low-latitude features
also present. This result is verified by independent reconstructions
using even- and odd-numbered spectra. This work confirms and extends
that of Barnes et al., and provides further evidence that there is
a correlation between the presence of low-latitude features and the
amplitude of the photometric light curve. It is also a further step
in the search for activity cycles on young G dwarfs.
Title: Gradient determination in multi-spacecraft missions
Authors: Jahn, J.; Wüest, M.; Jeffers, S.
Bibcode: 2002cosp...34E2721J
Altcode: 2002cosp.meetE2721J
The first multi-spacecraft missions dedicated to perform simultaneous
multi-point measurements of space plasmas are flying in orbit. However,
data analysis techniques do not yet properly take advantage of the
three-dimensionality of these new data sets. Present data analysis
continues to treat those data as isolated single- point measurements
which are combined only on the level of multi-panel time series
displays. A few methods have been described in the literature on
how to specifically exploit the three-dimensionality of these new
measurements. Here, we report on an implementation of these methods
to determine spatial gradients and vorticity. The implementation is
spacecraft or instrument independent, but for development and testing
of the implementation will use data from the Cluster mission.
Title: Near-Earth object velocity distributions and consequences
for the Chicxulub impactor
Authors: Jeffers, S. V.; Manley, S. P.; Bailey, M. E.; Asher, D. J.
Bibcode: 2001MNRAS.327..126J
Altcode:
An Öpik-based geometric algorithm is used to compute impact
probabilities and velocity distributions for various near-Earth object
(NEO) populations. The resulting crater size distributions for the Earth
and Moon are calculated by combining these distributions with assumed
NEO size distributions and a selection of crater scaling laws. This
crater probability distribution indicates that the largest craters on
both the Earth and the Moon are dominated by comets. However, from a
calculation of the fractional probabilities of iridium deposition, and
the velocity distributions at impact of each NEO population, the only
realistic possibilities for the Chicxulub impactor are a short-period
comet (possibly inactive) or a near-Earth asteroid. For these classes
of object, sufficiently large impacts have mean intervals of 100 and
300Myr respectively, slightly favouring the cometary hypothesis.
Title: Spectral analysis of the low-gravity extreme helium stars
LSS 4357, LS II+33.5 deg and LSS 99
Authors: Jeffery, C. S.; Hamill, Peter J.; Harrison, Paul M.; Jeffers,
Sandra V.
Bibcode: 1998A&A...340..476J
Altcode:
We have carried out quantitative analyses of three very low surface
gravity extreme helium stars with very similar spectra. Their effective
temperatures of ~ 16 000K fill a gap in a nearly continuous sequence
of extreme helium stars all having similar luminosity-to-mass ratios,
but extending from effective temperatures around 12 000 K to more than
20 000 K. Because of the low surface gravities and extremely rich
line spectra, the model atmosphere calculations have been reviewed,
and large-scale spectral synthesis techniques have been introduced
to the analyses for the first time. In addition to the high carbon
and nitrogen abundances usually seen in extreme helium stars, two of
the programme stars have extremely high oxygen abundances, comparable
with or greater than their carbon abundances. Based on observations
obtained at the European Southern Observatory, La Silla, Chile.
Title: The Determination of Absolute Luminosities of Circumstellar
Envelopes Around Be Stars
Authors: Stiff, T.; Jeffers, S.
Bibcode: 1989BAAS...21.1197S
Altcode:
No abstract at ADS
Title: Absolute Spectrophotometry of Be Stars
Authors: Stiff, T.; Jeffers, S.
Bibcode: 1987pbes.coll..211S
Altcode: 1987IAUCo..92..211S
Absolute spectrophotometric data have been obtained for a sample of
Be stars. The data have been corrected for differential atmospheric
extinction, instrumental response, and interstellar extinction and
calibrated in terms of absolute flux. Absolute Hα and Hβ fluxes have
been determined.
Title: Absolute spectrophotometry of Be and B stars.
Authors: Stiff, T.; Jeffers, S.
Bibcode: 1986JRASC..80..286S
Altcode:
No abstract at ADS
Title: Stellar Spectrophotometry with a Microcomputer Based
Intensified Silicon Vidicon
Authors: Jeffers, S.; Stiff, T.
Bibcode: 1986IAUS..118..453J
Altcode:
The authors report on the spectrophotometric performance of the
intensified, silicon vidicon detector (RCA 4804H) when used with a
low dispersion spectrograph.
Title: On the spectral variability of the extreme Of star, HD 151804.
Authors: Jeffers, S.; Weller, W. G.
Bibcode: 1986svss.conf..153J
Altcode:
This paper discusses spectrophotometric observations made with a
sensitive multi-channel detector and illustrates the kind of work that
can be done with a well-equipped small telescope in a good location.
Title: On the wavelength dependence of atmospheric extinction.
Authors: Jeffers, S.; Stiff, T.
Bibcode: 1985JRASC..79..238J
Altcode:
No abstract at ADS
Title: Short-term line-profile variability of gamma 2 Velorum -
evidence fora compact companion ?
Authors: Jeffers, S.; Stiff, T.; Weller, W. G.
Bibcode: 1985AJ.....90.1852J
Altcode:
Observational data are presented which show that the line profile of
the emission complex at λ465 nm (C III-IV) in γ2Velorum
varies on a time scale of a few minutes. The observed variability
occurs on the blue wing of the profile. This phenomenon is interpreted
as arising from the presence of a neutron star within the extended
envelope of the WC8 star. The suggested model requires the neutron star
to be periodically eclipsed. The predicted maximum orbital period of
the neutron star about the WC8 star is ≡5.4 days. The absence of a
hard X-ray flux from γ2Velorum and its significance for
the proposed model is discussed.
Title: Spectrophotometric catalogue of southern Wolf-Rayet stars.
Authors: Jeffers, S.; Weller, W. G.
Bibcode: 1985A&AS...61..173J
Altcode:
Spectrophotometric observations of 10 Galactic Wolf-Rayet stars obtained
at 350-500 nm (7-A resolution) and 450-750 nm (15-A resolution) using
the 60-cm Toronto reflector at Las Campanas Observatory during May-June
1974 are reported. The data-reduction procedures are described, and
the results are presented in tables and in spectrophotometric plots
including line identifications.
Title: HD 152408
Authors: Jeffers, S.; Weller, W. G.
Bibcode: 1985IAUC.4087....2J
Altcode: 1985IAUC.4087....0J
S. Jeffers, York University, Ontario; and W. G. Weller, Cerro Tololo
Interamerican Observatory, communicate: "Analysis of low- dispersion
spectra (360-500 nm, delta-lambda = 0.9 nm) obtained on six consecutive
nights (1974 May 30-June 4) shows remarkable and repeatable spectral
variability. The spectra obtained on the first two nights are very
similar with H-beta, He II 468.6-nm and N III 463.4-nm of comparable
strength relative to continuum. On June 1 He II 468.6-nm is reduced
by a factor of 3, N III by a factor of 2--both lines being broadened
by a factor of 2. Strong absorptions appear shortward of H-beta at
-2400 and 4000 km/s. On June 2 the spectrum is identical to that on
June 1. On June 3 the spectrum is identical to that on May 31, and on
June 4 the spectrum is identical to that on June 1. This regularity
suggests that a periodicity may be present with P < 1 day. More
observations are urged."
Title: Short Term Variability of γ2 Velorum-evidence
for a Compact Companion?
Authors: Stiff, T.; Jeffers, S.; Weller, W. G.
Bibcode: 1985BAAS...17..511S
Altcode:
No abstract at ADS
Title: Astronomical spectrophotometry using a cooled, intensified,
silicon vidicon detector.
Authors: Jeffers, S.; Stiff, T.; Weller, W. G.
Bibcode: 1984SPIE..445..199J
Altcode:
The performance and astronomical calibrations of a cooled intensified
silicon vidicon detector are described. The spectrometer comprises a
standard grating, classification dispersion spectrograph (22.4 nm/mm
in the first order, 11.2 nm/mm in the second order). Measurements of
differential extinction have been obtained from observations of the
spectrophotometric standard HR 4295 (mv = 2.37, A1V). Astronomical
observations using a 60-cm telescope indicate that the spectra
of 12.5 magnitude stars may be obtained with an S/N of 10 with a
one-hour integration. After corrections for differential extinction
and instrumental response, the agreement between derived and published
relative intensities is 3 percent.
Title: Direct imaging and photometry with an intensified silicon
vidicon detector
Authors: Jeffers, S.
Bibcode: 1982JRASC..76...19J
Altcode:
Direct imagery has been obtained by means of an intensified silicon
vidicon at the Cassegrain focus of a 60-cm telescope. These data are
presented and discussed together with an assessment of the photometric
capabilities of the detector. The detective quantum efficiency of the
detector is estimated to be 5 percent.
Title: Intensifier silicon vidicon spectrophotometer for line profile
studies in astronomy
Authors: Jeffers, S.; Weller, W. G.
Bibcode: 1981ApOpt..20..665J
Altcode:
The design and performance characteristics of a moderate
spectrophotometer for astronomical observations are described. The
spectrophotometer employs an intensifier silicon vidicon as
detector. The operating characteristics of the detector have been
evaluated and optimized. In astronomical use, the spectrophotometer is
capable of recording line profiles of stars of visual magnitude = 3.74
with a spectral resolution of 0.15 nm and SNR = 50 in an integration
time of 10 sec when used with a 60-cm telescope.
Title: On the linearity of electronography
Authors: Jeffers, S.
Bibcode: 1980A&A....92..196J
Altcode:
Absolute sensitometry of the electronographic emulsions XM, G5, and
L4 is reported for 5-35 KV range of incident electron energies. All
these emulsions are found to exhibit nonlinear response to the incident
electron flux. For a given electron energy, the emulsion characteristic
curve can be fitted to an equation of the form D = Ds(1 -
e exp -AE), where D = density, Ds = saturation density, A =
average area of developed grain, and E = exposure. This is in agreement
with the predictions of the single hit theory of electronography.
Title: Short term variability of line strengths in some Of and
WR stars.
Authors: Weller, W. G.; Jeffers, S.
Bibcode: 1979IAUS...83...27W
Altcode:
Short time scale variability is analyzed using the spectra of 10 Of
and 13 WR stars (stellar lines resolved), taken with an SIT Vidicon and
covering 150 nm at a dispersion of .3 nm per channel and instrumental
FWHM of 3 channels. Spectral features were reduced by defining two
centered, rectangular 'filters' having widths of 1.5 and 6.0 nm, with
the ratio of the fluxes in these pass bands defining a line strength
parameter. On time scales less than one hour there is a general lack
of variability in Of and WN stars and the presence of such in WC
stars. It is suggested that the later the subclass, the more likely
is variability, but no inference of periodic activity is drawn.
Title: Halpha variability of Nova Vulpeculae 1976.
Authors: Weller, W. G.; Jeffers, S.
Bibcode: 1978PASP...90..686W
Altcode:
Photoelectric spectra at Ha of Nova Vulpeculae 1976 were obtained on
six nights during October/November 1976. On one night a time series
(At 3 mins) of 27 spectra was obtained. Evidence is presented for
variability in the profile of Ha on a time scale of 1 hour and also
from night to night. Key words: spectroscopy-nova-spectral variability
Title: Novel spectrophotometer for the investigation of short term
variability in stellar spectra.
Authors: Stiff, T.; Jeffers, S.
Bibcode: 1978ApOpt..17.1811S
Altcode:
A variety of astronomical objects (e.g., O(f) stars, B(e) stars, optical
counterparts of X-ray sources, etc.) exhibit emission line spectra. For
some of these objects the emission line strengths are suspected as
being variable (and possibly periodic) over time scales as short as
minutes or less. A spectrophotometer has been built whose output signal
is a measure of the line strength only. The spectrophotometer is used
to look at the emission feature and the adjacent continuum in rapid
succession by means of magnetic modulation of the electron image of the
optical spectrum in an image tube, thus generating a modulated signal
which is detected with a lock-in amplifier. This detection technique
essentially subtracts off an instrumental dark current signal due to sky
background and the signal due to the continuum of the star giving a real
time measure of the line strength only. The design of the instrument,
its laboratory calibration, and some preliminary observational data
are presented.
Title: Spectrophotometry using an intensifier silicon vidicon.
Authors: Weller, W.; Herbst, W.; Jeffers, S.
Bibcode: 1977PASP...89..935W
Altcode:
A spectrometer has been assembled from a small-grating spectrograph
and a commercially available intensifier silicon vidicon detector
system. The spectrometer exhibits stability of response and linearity
suitable for spectrophotometry and evidence is presented that
spectrophotometric accuracy (within i 0.01 magnitude) is achieved even
on nights of low quality. A spectrum of such quality of the Of star
9 Sge is presented. The absolute photometry of Kuan and Kuhi (1976)
obtained for several points in the spectral region 420-560 nm has been
used for calibration and allows absolute measurements of line strengths
to be made. Key words: spectrophotometry-intensifier silicon vidicon
Title: Photoelectric spectroscopy of nova Vulpeculae 1976.
Authors: Jeffers, S.; Weller, W. G.
Bibcode: 1977JRASC..71..402J
Altcode:
No abstract at ADS
Title: Spectrophotometry at York University.
Authors: Weller, W. G.; Jeffers, S.
Bibcode: 1977JRASC..71..402W
Altcode:
No abstract at ADS
Title: On the nature of H 1-36 (3U 1746-37?).
Authors: Purton, C. R.; Jeffers, S.; Weller, W.
Bibcode: 1977JRASC..71R.406P
Altcode:
No abstract at ADS
Title: Comet West (1975n)
Authors: Herald, D.; Gilmore, A. C.; Kilmartin, P. M.; Gans, D. J.;
Candy, M. P.; Giclas, H. L.; Kantz, M. L.; Milet, B.; Webber, J. C.;
Snyder, L. E.; Crutcher, R. M.; Swenson, G. W.; Barth, C.; Lawrence,
G.; Weller, W.; Jeffers, S.; Danylewych, L.; Swings, J. P.; Fehrenbach,
C.; McCrosky, R. E.; Schwartz, G.; Leibowitz, E. M.; Rosenkrantz, M.;
Levite, A.; Rokoske, T. L.; Young, J.; Farrell, J. A.; di Cicco, D.;
Bortle, J.; Ney, E. P.; Merrill, K. M.; Neff, J. S.; Ketelsen, D. A.;
Smith, V. V.; Morris, C. S.; Hale, A.; Maley, P.; Mayo, M. J.; Nissen,
W. I.; Simmons, K.; Truxton, J.
Bibcode: 1976IAUC.2928....1H
Altcode:
The following precise positions have been reported: 1976 UT R. A. (1950)
Decl. m2 Observer Jan. 1.45451 21 09 09.09 -35 03 28.0 Herald 3.39227 21
12 28.31 -34 46 22.5 10.5 Gilmore 9.52569 21 23 42.78 -33 47 45.3 Gans
9.53819 21 23 43.93 -33 47 34.3 " Feb. 15.50417 22 59 36.36 -20 42 11.6
Candy 16.50417 23 02 28.53 -19 48 32.3 " Mar. 6.53507 21 43 11.33 + 6 51
25.2 Giclas 10.17433 21 28 10.35 + 8 37 33.0 Milet 10.19701 21 28 05.64
+ 8 38 03.4 " 10.53490 21 26 55.62 + 8 46 10.3 Giclas 11.17024 21 24
54.17 + 9 00 13.6 Milet 11.18054 21 24 52.22 + 9 00 27.5 " 13.53142 21
18 13.01 + 9 46 55.5 Giclas 15.52031 21 13 31.48 +10 20 21.0 " D. Herald
(Kambah, near Canberra). Correction to IAUC 2910. A. C. Gilmore
(Carter Observatory). Measurer: P. M. Kilmartin. D. J. Gans and
M. P. Candy (Perth Observatory, Bickley). H. L. Giclas (Lowell
Observatory). Measurer: M. L. Kantz. B. Milet (Nice Observatory). Double
tail > 15o in length. J. C. Webber, L. E. Snyder, R. M. Crutcher and
G. W. Swenson, University of Illinois, report the detection, using the
37-m radio telescope at the Vermilion River Observatory, of OH emission
at 1667 MHz. The peak intensity of this line on Mar. 12, 13 and 14
was 0.15 Jy with full width at half height of 3.9 km/s. C. Barth
and G. Lawrence, University of Colorado, report that ultraviolet
observations (range 1250-1700 A) from a NASA Aerobee rocket launched
on Mar. 5.48 UT show the principal emissions to be O I 1304 A, C I
1561 A and 1657 A and the fourth positive bands of CO. The vibrational
population of the CO bands was determined. W. Weller, S. Jeffers and
L. Danylewych, York University, report that spectroscopic observations
(ranges 3800-5000 A and 4400-6000 A, resolution 10 A) obtained on
Mar. 11.40 UT using an intensifier silicon vidicon spectrometer showed
the band systems of C2 (Delta-nu = 0, +1 and -1) and CN (Delta-nu =
0). Preliminary analysis of C2 (Delta-nu = 0 and +1) gives a vibrational
temperature of 5400 +/- 200 K and a rotational temperature of 3200
+/- 100 K. The CN/C2 ratio appears weaker than in comet 1973 XII at
similar heliocentric distance. Observations by J. P. Swings, European
Southern Observatory, on Mar. 12.41 UT describe strong CN (0,0), CH,
C2 (1,0) and C2 (0,1) emission and medium-strength C3, CN (0,1) and C2
(2,0) on a weak to very weak continuum. C. Fehrenbach, Observatoire
de Haute Provence, also mentions the well developed emissions due
to C2, CN and CH, with C3 somewhat less intense; continuous emission
was also detected from the nucleus. R. E. McCrosky and G. Schwartz,
Harvard College Observatory, report that observations (5200-7000 A)
on Mar. 18.4 UT using the echelle spectrograph and an image tube on
the 155-cm reflector confirm the presence of H-alpha emission (cf. IAUC
2927) shifted ~ 20 km/s blueward of solar-absorption H-alpha. Na I was
still very strong. Reporting on the tail spectrum, E. M. Leibowitz,
M. Rosenkrantz and A. Levite, Wise Observatory, mention the 6-0,
7-0, 8-0 and 9-0 bands of H2O+, extending about 7' from the head on
Mar. 11.1 UT. Traces of the 10-0 system were possibly present, but the
5-0 bands were missing. Photographs obtained by T. L. Rokoske, Boone,
North Carolina; J. Young, Wrightwood, California; J. A. Farrell, Los
Alamos, New Mexico; and D. di Cicco, Waltham, Massachusetts, show that
the synchronic bands (cf. IAUC 2924) were present as early as Mar. 4.4
UT but that by Mar. 9.5 they had become very weak. J. Bortle, Brooks
Observatory, reports further visual observations of tail structure:
Mar. 12.41 UT, 11o long in p.a. 293o (gas), 12o.5 in 310o and 26o.5
in 320o (dust); 14.40, 9o in 288o (gas), streamer in 306o and 10o in
315o (dust); 18.40, 5o.5 in 297o (in bright moonlight). E. P. Ney
and K. M. Merrill, O'Brien Observatory, University of Minnesota,
report the following visual and infrared magnitudes, obtained on
Mar. 10.8 UT with a diaphragm of 20": V = +4.8, R = +4.4, I = +4.1;
1.2 um, +3.4; 1.6 um, +3.0; 2.2 um, + 2.4; 3.5 um, -0.7; 4.8 um, -2.7;
8.5 um, -5.2; 10.6 um, -6.1; 12.5 um, -6.2; 18 um, -6.8. J. S. Neff,
D. A. Ketelsen and V. V. Smith, University of Iowa, report that drift
scans on Mar. 11.5 UT show that the intensity in a band centered
on the C2 5100 A emission was about twice that of the continuum in
a similar band near 5250 A. Further selected total visual magnitude
estimates: Mar. 6.46 UT, 1.4 (C. S. Morris, West Lafayette, Indiana,
8 x 52 elbow telescope); 7.51, 1.3 (A. Hale, Alamogordo, New Mexico,
naked eye); 9.47, 2.0 (P. Maley, Houston, Texas, 7 x 35 binoculars);
10.46, 1.9 (Maley); 12.41, 1.9 (Bortle, 10 x 50 binoculars); 12.50,
2.3 (M. J. Mayo, Mount Wilson, California, 7 x 35 binoculars); 13.45,
1.6 (W. I. Nissen, Arlington, Virginia, naked eye); 13.52, 2.4 (Mayo);
14.40, 2.1 (Bortle); 14.44, 2.5 (K. Simmons, Jacksonville, Florida,
naked eye); 15.56, 2.7 (Mayo and J. Truxton, Agoura, California);
17.4, 3.2 (Maley); 18.40, 3.1 (Bortle).
Title: Rapid Variations in Emission Line Strengths in the Early
Stages of Nova Cygni 1975
Authors: Weller, W.; Jeffers, S.
Bibcode: 1975BAAS....7..509W
Altcode:
No abstract at ADS
Title: Nova Cygni 1975
Authors: Harevich, V.; Bocharov, A. N.; Shugarov, S. Yu.;
Vsekhsvyatskij, S. K.; Shefer, Y.; Kukarkin, B. V.; Aksenov, E. P.;
Alksne, Z.; Platais, I.; Samus, N. N.; Vidal, N. V.; Liller, W.;
Margrave, T. E.; Doolittle, J. H.; French, H.; Kirshner, R.; Maley,
P.; Koch, R. H.; Ambruster, C. W.; Hull, A. B.; de Vaucouleurs, G.;
Tomkin, J.; Campbell, B.; Jeffers, S.; Weller, W.
Bibcode: 1975IAUC.2839....1H
Altcode:
The following early independent discoveries have been reported:
Aug. 29.64 UT, mv = 2.5 (V. Harevich, Eniseysk, U.S.S.R.); 29.69, 2.5
(A. N. Bocharov, Gophitskoye, U.S.S.R.); 29.72, 2.8 (S. Yu. Shugarov,
Sternberg Astronomical Institute; correction to IAUC 2826); 29.73,
2 (S. K. Vsekhsvyatskij, Kiev Observatory); 29.78, 3 (Y. Shefer,
Kfar-Saba, Israel; correction to IAUC 2826). B. V. Kukarkin and
E. P. Aksenov, Sternberg Astronomical Institute, report further
prediscovery observations: Aug. 5.91 UT, V = 15.95 (Z. Alksne
and I. Platais, Radioastrophysica1 Observatory, Riga); 8.01,
B = 17.6 (Alksne and Platais); 12.98, B = 17.0 (N. N. Samus,
Sternberg Astronomical Institute); 24.94, R = 13.5 (Alksne and
Platais). N. V. Vidal and W. Liller, Center for Astrophysics, report
that inspection of Harvard patrol plates taken between 1898 and 1975
Aug. 10 did not show any object down to about magnitude 15.5 within
+/- 0'.5 of the position of the nova. The following photoelectric
observations have been reported: 1975 UT V B - V U - B Observer
Sept. 6.368 5.60 +0.45 -0.58 Margrave & Doolittle 6.405 5.67 +0.44
-0.60 " 6.431 5.63 +0.44 -0.57 " 8.383 6.09 +0.42 -0.60 " 9 6.21 +0.38
-0.60 French 10 6.35 +0.35 -0.63 " 10.330 6.41 +0.36 -0.56 Margrave
& Doolittle 11.304 6.47 +0.37 -0.56 " 12.264 6.51 +0.33 -0.48 "
13.264 6.63 +0.32 -0.48 " 14.283 6.80 +0.31 -0.48 " 15.415 6.86 +0.27
-0.47 " T. E. Margrave and J. H. Doolittle (Blue Mountain Observatory,
University of Montana). Accuracy 0.03 in V, 0.02 in B-V, 0.04 in
U-B. Comparison stars HR 7949 and 8162 and other UBV standards. Eight
B and V measures during Sept. 6.358-6.434 UT are consistent to 0.01
with a periodic variation of amplitude 0.06 magnitude and period 3.2
hr (Tempesti, IAUC 2834). A corresponding series of U measures gave
no conclusive evidence of variation. H. French (Kitt Peak National
Observatory). Accuracy 0.06 in V, 0.01 in B-V and U-B. Communicated by
R. Kirshner. P. Maley, Houston, Texas, provides the following recent
visual magnitude estimates: Sept. 17.17 UT, 6.8; 18.07, 7.0; 19.12, 7.1;
20.08, 7.0; 21.12, 7.1; 22.12, 7.1; 23.14, 7.2; 24.12, 7.2. R. H. Koch
and C. W. Ambruster, Flower and Cook Observatory, report that they
observed further light minima on Sept. 14.173, 15.142 and 15.292 UT
and light maxima on Sept. 14.237 and 15.20. The amplitudes are 0.11
magnitude in yellow, 0.13 magnitude in blue. Preliminary ephemeris:
primary light minimum = 1975 Sept. 10.0705 UT + 0.2738E. A 'bump'
before primary minimum developed between Sept. 14.30 and 15.08 and
caused an apparent momentary lengthening of the period to 0.2797
day. A. B. Hull finds no polarization variations greater than
0.05 percent and 1o during the cycle (in three bandpasses). G. de
Vaucouleurs, Department of Astronomy, University of Texas at Austin,
writes that the visual maximum was magnitude 1.80 +/- 0.05 on Aug. 30.85
UT and that extrapolation of the light curve indicates that the nova
may be expected to reach V = 8.0, 9.0 and 10.0 on or about Sept. 30,
Oct. 30 and Dec. 15, respectively. From the rate of decay he finds
(m-M)_V = 12.05 and MV_ = -10.25 (at maximum). He suggests that (m-M)
should be corrected by -3.2E = -1.45 +/- 0.3 for absorption [where the
color excess E(B-V) was inferred from interstellar line intensities
measured by J. Tomkin at McDonald Observatory near maximum light]; thus
the distance is 1.3 +/- 0.2 kpc. B. Campbell, David Dunlap Observatory,
reports that spectrum scans on Sept. 5.2-5.3 UT show variations in
all four emission peaks of H-alpha on a timescale of 1 hr. The total
intensity of H-alpha was found to vary on a similar timescale during
Sept. 7.2-7.3. In the range 6000-7000 A on both dates the continuum
was about 3.7 magnitudes below the peaks of H-alpha and was also
variable. S. Jeffers and W. Weller, Physics Department, York University,
Downsview, Ontario, report: "Low-resolution time-resolved (Delta-t =
2 min) spectra (instrumental full width at half height 16 A) obtained
with an intensifier silicon vidicon spectrometer on a 60-cm reflector
on Sept. 3.1, 4.1, 5.1, 7.3 and 8.2 UT show striking night-to-night and
short-term variability. Both line strengths and profiles are affected,
especially the Balmer lines and C III 4650 A. Night-to-night changes
in the Balmer lines appear to be in the relative strengths of at least
three and possibly four components, possibly associated with various
shell ejections. Time-resolved spectra on Sept. 5.1 show variations
in the peak intensity of H-beta and H-gamma of about 6 percent on
timescales of 2-6 min. The growth of C III 4650 A can be seen relative
to the Fe II spectrum on timescales of 15-30 min. The line blend at
5010 A shows no measurable variation on the same spectra."
Title: Short-Term Spectral Variability of γ^{2} Velorum. Photometric
Observations
Authors: Sanyal, A.; Weller, W.; Jeffers, S.
Bibcode: 1974ApJ...187L..31S
Altcode:
Photometric observations of 2 Vel using a narrow-band interference
filter centered on He II X4686 have been obtained. Analysis of these
data shows short-period variability with a period of 154 + 35 5. This is
consistent with our previously reported spectrum-scanner observations
showing short-term variability with a period of 200 1 50 5. Subject
headings: WoIf-Rayet stars - spectrum variables - photometry
Title: Short time spectral variability of gamma 2 Velorum.
Authors: Sanyal, A.; Jeffers, S.; Weller, W.
Bibcode: 1973BAAS....5..475S
Altcode:
No abstract at ADS
Title: Short Period Spectral Variations in γ2 Velorum
Authors: Jeffers, S.; Weller, W.; Sanyal, A.
Bibcode: 1973NPhS..243..109J
Altcode: 1973Natur.243..109J
γ2 Velorum is a spectroscopic binary with a Wolf-Rayet (WC8)
and a 091 star1 as companions. Ganesh and Bappu2
have found a period of 78.5 d for the system. Perrine3
reported variations in the shapes of the HeI emission lines of
γ2 Velorum during May and June 1919 in a time period of
days. Smith4 confirmed Perrine's observations in 1953.
Title: gamma 2 Velorum.
Authors: Jeffers, S.; Weller, W.; Sanyal, A.; Madore, B.
Bibcode: 1973IAUC.2531....1J
Altcode:
No abstract at ADS
Title: gamma 2 Velorum.
Authors: Jeffers, S.; Weller, W.; Sanyal, A.
Bibcode: 1973IAUC.2495....1J
Altcode:
No abstract at ADS
Title: Relative Detective Quantum Efficiency Measurements of Four
Astronomical Emulsions when Used With a New Developer
Authors: Jeffers, S.
Bibcode: 1971A&A....15..221J
Altcode:
Relative detective quantum efficiency measurements have been made on
four emulsions (IIa-0, 103a-0, lla-D, llIa-J) when used with their
recommended developers and with MWP 2 developer. Th both cases,
the densities giving optimum detective quantum efficiency have been
determined. A significant improvement in detective quantum efficiency
is found for 103a-0 and ffia-J emulsions. Key words: photographic
emulsion - developer - granularity - detective quantum efficiency
Title: Relative detective quantum efficiency measurements of some
emulsions when used with a new developer for astronomical plates.
Authors: Jeffers, S.
Bibcode: 1971JRASC..65..176J
Altcode:
No abstract at ADS
Title: Direct Photography with a Carnegie Image Tube
Authors: Jeffers, S.
Bibcode: 1970JRASC..64..121J
Altcode:
No abstract at ADS