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Author name code: nisenson
ADS astronomy entries on 2022-09-14
author:"Nisenson, Peter"
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Title: An Introduction to Optical Stellar Interferometry
Authors: Labeyrie, A.; Lipson, S. G.; Nisenson, P.
2014iosi.book.....L Altcode:
1. Introduction; 2 Basic concepts: a qualitative introduction;
3. Interference, diffraction and coherence; 4. Aperture synthesis;
5. Optical effects of the atmosphere; 6. Single-aperture techniques;
7. Intensity interferometry; 8. Amplitude interferometry: techniques
and instruments; 9. The hypertelescope; 10. Nulling and coronagraphy;
11. A sampling of interferometric science; 12. Future ground and space
projects; Appendices.
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Title: An Introduction to Optical Stellar Interferometry
Authors: Labeyrie, A.; Lipson, S. G.; Nisenson, P.
2006iosi.book.....L Altcode:
1. Introduction; 2 Basic concepts: a qualitative introduction;
3. Interference, diffraction and coherence; 4. Aperture synthesis;
5. Optical effects of the atmosphere; 6. Single-aperture techniques;
7. Intensity interferometry; 8. Amplitude interferometry: techniques
and instruments; 9. The hypertelescope; 10. Nulling and coronagraphy;
11. A sampling of interferometric science; 12. Future ground and space
projects; Appendices.
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Title: Precise Radial Velocities with an Upgraded Advanced Fiber
Optic Echelle (AFOE)
Authors: Walters, M. A.; Korzennik, S. G.; Nisenson, P.; Henry, G. W.
2006AAS...20721108W Altcode:
The Advanced Fiber Optic Echelle (AFOE) has been used to make
precise radial velocity (PRV) observations for some 12 years. The
AFOE spectrograph was initially designed as a test-bed for PRV
techniques for astroseismology and planet detection, and tried
to provide both short term and long term stability. The resulting
trade-offs between spectral resolution, range, and coverage led to
a low efficiency design. In order to optimize PRVs obtained with
the iodine cell technique, the spectrograph was recently upgraded,
increasing the throughput and spectral coverage while reducing the
maximum resolution and range. The instrument was also moved from the
60" Tillinghast telescope at the Fred Lawrence Whipple Observatory,
located at Mt. Hopkins (AZ), to the 100" Hooker telescope, located at
Mt. Wilson (CA). We describe the instrumental changes required for the
spectrograph upgrade as well as those needed to accommodate the 100"
telescope. <P />As a result of the instrumental changes, the data
configuration has changed significantly. One would like to be able
to combine radial velocities obtained before the upgrade with those
obtained after, but one must take care in doing so. We describe the
methodology developed to allow us to use all of the PRVs together. We
also detail the precision achieved for this technique, along with
the inherent precision of the upgraded configuration. <P />Finally,
we present the radial velocities we have obtained for HD 185395 as
an interesting example of our studies. This triple system shows large
radial velocity variations. We compare the RV variations with observed
photometric changes, and present period analyses for both data sets. <P
/>This work is funded by NASA/JPL/SIM (subcontract no. 1259554).
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Title: An Introduction to Astronomical Interferometry
Authors: Labeyrie, Antoine; Lipson, Stephen; Nisenson, Peter
2006iai..book.....L Altcode:
No abstract at ADS
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Title: Study of Coronagraphic Techniques
Authors: Tolls, V.; Nisenson, P.; Aziz, M. J.; Gonsalves, R. A.;
Korzennik, S. G.; Labeyrie, A.; Lyon, R. G.; Melnick, G. J.; Woodruff,
R. A.
2004AAS...20517104T Altcode: 2005BAAS...37..376T
Direct imaging of extra-solar planets is important for determining
the properties of individual planets and to study multi-planet
systems. Obtaining spectra of extra-solar planets enables us to
constrain the composition of planetary atmospheres and surfaces,
their climates, and their rotation periods. The techniques required to
isolate and detect an extra-solar planet next to its host star are quite
challenging and require significant improvement. SAO is setting up a
testbed to study coronagraphic techniques, starting with Labeyrie's
multi-step speckle reduction technique. This technique incorporates
a speckle phase corrector and second occulter for speckle light
suppression. The goal is to study this technique in the testbed for
its application in coronagraphic cameras. In addition, the testbed will
be used to characterize soft-edge occulters. Simulations of soft-edge
occulters with a Gaussian absorption profile show a promising reduction
of the flux in the core of the point spread function in coronagraphs. We
expect this to lead to a reduction in the inner working distance and
to an increase in contrast ratio compared to a Lyot coronagraph. The
occulters for the tests will be developed in Harvard's Department of
Engineering and Applied Sciences and by Lockheed-Martin Corp. This
poster will present the setup of SAO's testbed, simulations for all
developments, and first test results.
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Title: Calculating Velocity Shifts Between the Pre- and Post-Upgrade
AFOE Data Sets
Authors: Miller, J. K.; Korzennik, S. G.; Nisenson, P.
2003AAS...203.1710M Altcode: 2003BAAS...35.1235M
We present the results of our efforts to develop a procedure to
determine the velocity shifts between the pre- and post-upgrade
stellar reference spectra observed with the Advanced Fiber Optic Echelle
(AFOE). The AFOE spectrograph was upgraded to increase its efficiency in
measuring radial velocities by rearranging the physical set-up of the
optical system. While observing roughly the same wavelength range, the
post-upgrade spectra have a different ratio of wavelength to pixels and
gaps in the data where pieces of the spectrum were not projected onto
the CCD. These differences necessitated taking new stellar references
of each star system. All velocity measurements for a star are made
relative to this reference. However, there is an unknown velocity
shift between every pair of new and old stellar reference spectra
simply because they were observed on different nights. The differences
in the spectra prevent us from recalculating all of the velocities
relative to one reference or the other. To overcome this problem, we
have been developing a procedure that models the new stellar reference
with a parameterized function of the old reference, and the velocity
shift is one parameter of the model. We independently model each
wavelength range of the new spectrum that overlaps the old spectrum,
which gives us twelve measurements of the velocity shift. The spread in
these results gives us an idea of the precision of our calculations,
and our goal precision is ∼ 1 ms<SUP>-1</SUP>. <P />This work was
supported in part by the SAO intern program under NSF grant AST-9731923.
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Title: The ELODIE survey for northern extra-solar planets. II. A
Jovian planet on a long-period orbit around GJ 777 A
Authors: Naef, D.; Mayor, M.; Korzennik, S. G.; Queloz, D.; Udry,
S.; Nisenson, P.; Noyes, R. W.; Brown, T. M.; Beuzit, J. L.; Perrier,
C.; Sivan, J. P.
2003A&A...410.1051N Altcode: 2003astro.ph..6586N
We present radial-velocity measurements obtained with the ELODIE
and AFOE spectrographs for <ASTROBJ>GJ 777 A</ASTROBJ> (<ASTROBJ>HD
190360</ASTROBJ>), a metal-rich ([Fe/H] = 0.25) nearby (d = 15.9 pc)
star in a stellar binary system. A long-period low radial-velocity
amplitude variation is detected revealing the presence of a Jovian
planetary companion. Some of the orbital elements remain weakly
constrained because of the smallness of the signal compared to our
instrumental precision. The detailed orbital shape is therefore
not well established. We present our best fitted orbital solution:
an eccentric (e = 0.48) 10.7-year orbit. The minimum mass of the
companion is 1.33 M<SUB>Jup</SUB>. <P />Based on observations made
with the ELODIE echelle spectrograph mounted on the 1.93-m Telescope
at the Observatoire de Haute-Provence (CNRS) and with the AFOE
spectrograph mounted on the 1.5-m Telescope at the Fred Lawrence
Whipple Observatory (SAO). <P />The ELODIE and AFOE measurements
discussed in this paper are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/1051
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Title: Comparison of several coronagraphic approaches to the
Terrestrial Planet Finder
Authors: Ridgway, Stephen T.; Burrows, Christopher J.; Friedman,
Edward J.; Gezari, Daniel Y.; Harwit, Martin O.; Kaplan, Michael H.;
Kaylor, Larry; Lyon, Richard G.; Melnick, Gary J.; Nisenson, Peter;
Peterson, Lee D.; Spergel, David N.; Woodruff, Robert A.
2003ESASP.539..561R Altcode: 2003toed.conf..561R
Planetological and technical issues have led to a renewed interest
in visible coronographic concepts for a Terrestrial Planet Finder
mission. This has stimulated rapid development of new, generalized
coronagraphic techniques, including exotic apodizations and nulling
schemes. Hitherto, it has been difficult to compare different concepts,
owing to the complex interaction between details of the concepts and
instrument and mission parameters and optimization.
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Title: VizieR Online Data Catalog: ELODIE survey for northern
extra-solar planets. II. (Naef+, 2003)
Authors: Naef, D.; Mayor, M.; Korzennik, S. G.; Queloz, D.; Udry,
S.; Nisenson, P.; Noyes, R. W.; Brown, T. M.; Beuzit, J. L.; Perrier,
C.; Sivan, J. P.
2003yCat..34101051N Altcode:
Here are the 69 radial-velocity measurements of GJ 777A (HD 190360)
used for deriving the orbital solution of this star. These velocities
were obtained using the ELODIE echelle spectrograph mounted on the
1.93-m Telescope at Observatoire de Haute-Provence (France) and the
AFOE spectrograph mounted on the 1.5-m Telescope at the Fred Lawrence
Whipple Observatory (USA). <P />(1 data file).
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Title: Calculation of Optimized Apodizers for a Terrestrial Planet
Finder Coronagraphic Telescope
Authors: Gonsalves, R.; Nisenson, P.
2003PASP..115..706G Altcode: 2002astro.ph.10166G
One of two approaches to implementing NASA's Terrestrial Planet
Finder is to build a space telescope that utilizes the techniques
of coronagraphy and apodization to suppress diffraction and image
exoplanets. We present a method for calculation of a telescope's
apodizer that suppresses the sidelobes of the image of a star so
as to optimally detect an Earth-like planet. Given the shape of
a telescope's aperture and given a search region for a detector,
we solve an integral equation to determine an amplitude modulation
(an apodizer) that suppresses the star's energy in the focal plane
search region. The method is quite general and yields as special cases
the product apodizer reported by Nisenson & Papaliolios and the
prolate spheroidal apodizer of Kasdin et al. and Aime et al. We show
computer simulations of the apodizers and the corresponding point-spread
functions for various aperture-detector configurations.
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Title: Motions of Isolated G-Band Bright Points in the Solar
Photosphere
Authors: Nisenson, P.; van Ballegooijen, A. A.; de Wijn, A. G.;
Sütterlin, P.
2003ApJ...587..458N Altcode: 2002astro.ph.12306N
Magnetic elements on the quiet Sun are buffeted by convective flows
that cause lateral motions on timescales of minutes. The magnetic
elements can be observed as bright points (BPs) in the G band at 4305
Å. We present observations of BPs based on a long sequence of G-band
images recorded with the Dutch Open Telescope and postprocessed using
speckle-masking techniques. From these images we measured the proper
motions of isolated BPs and derived the autocorrelation function of
their velocity relative to the solar granulation pattern. The accuracy
of BP position measurements is estimated to be less than 23 km on
the Sun. The rms velocity of BPs (corrected for measurement errors)
is about 0.89 km s<SUP>-1</SUP>, and the correlation time of BP motions
is about 60 s. This rms velocity is about 3 times the velocity measured
using cork tracking, almost certainly due to the fact that isolated BPs
move more rapidly than clusters of BPs. We also searched for evidence
of vorticity in the motions of G-band BPs.
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Title: ExPO: a Discovery-class apodized square aperture exo-planet
imaging space telescope concept
Authors: Gezari, Daniel Y.; Nisenson, Peter; Papaliolios, Costas D.;
Melnick, Gary J.; Lyon, Richard G.; Harwit, Martin; Ridgway, Stephen
T.; Woodruff, Robert A.
2003SPIE.4860..302G Altcode:
The Extrasolar Planet Observatory (ExPO) is envisioned as a
Discovery-class space telescope for the direct detection and
characterization of extra-solar planets. ExPO would also demonstrate
the feasibility of a number of technologies which could be critical
to the ultimate success of the Terrestrial Planet Finder mission. ExPO
would detect a wide range of planet types in the visible and near IR,
and do spectrophotometry and spectroscopy on many of the detected
objects. The apoodized square aperture coronagraphic space telescope
is designed to resolve faint companions near much brighter point-like
sources by achieving very high dynamic range imaging at separations
as small as 0.1 arcsec.
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Title: Extra-solar planetary imager (ESPI) for space-based Jovian
planetary detection
Authors: Lyon, Richard G.; Gezari, Daniel Y.; Melnick, Gary J.;
Nisenson, Peter; Papaliolios, Costas D.; Ridgway, Stephen T.; Friedman,
Edward J.; Harwit, Martin; Graf, Paul
2003SPIE.4860...45L Altcode:
The Extra-Solar Planetary Imager (ESPI) is envisioned as a space based,
high dynamic range, visible imager capable of detecting Jovian like
planets. Initially proposed as a NASA Midex (NASA/Medium Class Explorer)
mission (PI:Gary Melnick), as a space-based 1.5 x 1.5 m2 Jacquinot
apodized square aperture telescope. The combination of apodization
and a square aperture telescope reduces the diffracted light from a
bright central source increasing the planetary to stellar contrast
over much of the telescope focal plane. As a result, observations of
very faint astronomical objects next to bright sources with angular
separations as small as 0.32 arcseconds become possible. This permits
a sensitive search for exo-planets in reflected light. ESPI is capable
of detecting a Jupiter-like planet in a relatively long-period orbit
around as many as 160 to 175 stars with a signal-to-noise ratio >
5 in observations lasting maximally 100 hours per star out to ~16
parsecs. We discuss the scientific ramifications, an overview of the
system design including apodizing a square aperture, signal to noise
issues and the effect of wavefront errors and the scalability of ESPI
with respect to NASA's Terrestrial Planet Finder mission.
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Title: The Extrasolar Planet Imager (ESPI)
Authors: Nisenson, P.; Melnick, G. J.; Geary, J.; Holman, M.;
Korzennik, S. G.; Noyes, R. W.; Papaliolios, C.; Sasselov, D. D.;
Fischer, D.; Gezari, D.; Lyon, R. G.; Gonsalves, R.; Hardesty, C.;
Harwit, M.; Marley, M. S.; Neufeld, D. A.; Ridgway, S. T.
2003ASPC..294..633N Altcode: 2002astro.ph.10046N
ESPI has been proposed for direct imaging and spectral analysis of
giant planets orbiting solar-type stars. ESPI extends the concept
suggested by Nisenson and Papaliolios (2001) for a square aperture
apodized telescope that has sufficient dynamic range to directly
detect extrasolar planets. With a 1.5-meter square mirror, ESPI can
deliver high dynamic range imagery as close as 0.3 arcseconds to bright
sources, permitting a sensitive search for extrasolar planets around
nearby stars and a study of their characteristics in reflected light.
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Title: High-Resolution Imaging of the Solar Photosphere Using
Simultaneous G-Band and Continuum Observations
Authors: van Ballegooijen, A. A.; Nisenson, P.
2002AAS...200.3801V Altcode: 2002BAAS...34..698V
Imaging of the Sun with ground-based telescopes requires accurate
correction for the effects of turbulence in the Earth's atmosphere
(“seeing"). An observed solar image is a convolution of a true
solar image with a point spread function (PSF) describing the seeing
effects. We present a new method for image reconstruction that uses
pairs of images taken at two nearby wavelengths (G-band, 430.5 nm,
and nearby continuum, 450.8 nm). Each image pair is taken strictly
simultaneously, so that the two images are affected by the same
PSF. A burst of 21 such image pairs is taken within a few seconds;
the sun does not change much during this time, but the seeing varies
randomly from one pair to the next. We determine the true solar images
(and 21 PSFs) by iterative deconvolution. The method is applied to
measurements obtained at the Dunn Solar Telescope (NSO/Sacramento
Peak) on November 2, 2001. Preliminary results from the analysis of
these data are presented. This work is supported by a grant from the
National Science Foundation.
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Title: The Extra-Solar Planet Imager (ESPI): A Proposed MIDEX Mission
Authors: Melnick, G. J.; Fischer, D.; Geary, J. C.; Gezari, D. Y.;
Hardesty, C.; Harwit, M.; Holman, M.; Korzennik, S. G.; Lyon, R. G.;
Marley, M. S.; McElroy, M. B.; Neufeld, D. A.; Nisenson, P.; Noyes,
R. W.; Papaliolios, C.; Ridgway, S. T.; Sasselov, D. D.
2001AAS...199.0910M Altcode: 2002BAAS...34..559M
ESPI is a project that has been proposed as a NASA MIDEX for direct
imaging and spectral analysis of giant planets orbiting solar-type
stars. ESPI extends the concept suggested by Nisenson and Papaliolios
(2001) for a square aperture apodized telescope that has sufficient
dynamic range to directly detect exo-planets. ESPI can deliver high
dynamic range imagery as close as 0.32 arcseconds to bright sources,
permitting a sensitive search for exoplanets around nearby stars and
a study of their characteristics in reflected light. It also permits
unique observations of many Galactic, extragalactic and cosmological
sources. The ESPI Survey will be conducted with a square 1.5 x 1.5-meter
telescope mirror, operated in conjunction with a Jacquinot apodization
mask that has a throughput of more than 30 percent. The system is
capable of detecting Jupiter-like planets in relatively long-period
orbits around as many as 160 to 175 stars with a signal-to-noise
ratio greater than 5. In addition to the survey, ESPI will also
study a few of the brightest discovered planets spectroscopically
and spectrophotometrically to distinguish ice giants like Uranus and
Neptune from gas giants like Jupiter and Saturn, and to determine
whether super-Earth and super-Venus planets exist. Nisenson, P. and
Papaliolios, C. 2001, ApJ, 548, L 201.
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Title: Analysis of High Contrast Imaging Techniques for Space Based
Direct Planetary Imaging
Authors: Lyon, R. G.; Gezari, D. Y.; Nisenson, P.
2001AAS...198.7709L Altcode: 2001BAAS...33..903L
The recent numerous detections of Jupiter and Saturn like planets in
has driven a resurgence in research of space based high contrast imaging
techniques for direct planetary imaging. Work is currently ongoing for
concepts for NASA's Terrestrial Planet Finder mission and a number of
study teams have been funded. The authors are members of one team. We
report on our ongoing investigations of a number of techniques for
direct detection and imaging of Earth-like planets around nearby stellar
sources. Herein, we give a quantitative analysis of these techniques and
compare and contrast them via computer simulations. The techniques we
will be reporting on are Bracewell Interferometry, Nisenson Apodized
Square Aperture, and Coronagraphic masking techniques. We parameterize
our results with respect to wavelength, aperture size, effects of
mirror speckle, both mid- and high-spatial frequency, detector and
photon noise as well pointing error.
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Title: Detection of Earth-like Planets Using Apodized Telescopes
Authors: Nisenson, Peter; Papaliolios, Costas
2001ApJ...548L.201N Altcode: 2001astro.ph..1241N
The mission of NASA's Terrestrial Planet Finder (TPF) is to find
Earth-like planets orbiting other stars and characterize the atmospheres
of these planets using spectroscopy. Because of the enormous brightness
ratio between the star and the reflected light from the planet,
techniques must be found to reduce the brightness of the star. The
current favorite approach to doing this is with interferometry:
interfering the light from two or more separated telescopes with a
π phase shift, nulling out the starlight. While this technique can,
in principle, achieve the required dynamic range, building a space
interferometer that has the necessary characteristics poses immense
technical difficulties. In this paper, we suggest a much simpler
approach to achieving the required dynamic range. By simply adjusting
the transmissive shape of a telescope aperture, the intensity in large
regions around the stellar image can be reduced nearly to zero. This
approach could lead to construction of a TPF using conventional
technologies, requiring space optics on a much smaller scale than the
current TPF approach.
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Title: A New Technique for Terrestrial Planet Finding
Authors: Nisenson, P.; Papaliolios, C.
2000AAS...197.4909N Altcode: 2000BAAS...32Q1486N
The mission of NASA's Terrestrial Planet Finder (TPF) is to find
Earth-like planets orbiting other stars and characterize the
atmospheres of these planets using spectroscopy. Because of the
enormous brightness ratio between the star and the reflected light
from the planet, techniques must be found to reduce the brightness
of the star. The current favorite approach to doing this is with
infrared interferometry: interfering the light from two (or more)
separated telescopes with a pi/2 phase shift, nulling out the starlight
and allowing detection of the reflected light from the planet. While
this technique can, in principle, achieve the required dynamic range,
building a space interferometer that has the necessary characteristics
poses immense technical difficulties. In this paper, we suggest a much
simpler approach to achieving the required dynamic range. This approach
could lead to construction of a TPF that uses conventional technology
and operates in the visible, requiring space optics on a much smaller
scale than the current TPF approach. We wish to acknowledge support
for this work from an SVS subcontract (SVS Inc SUB-00-095) for TPF
studies to the Smithsonian Astrophysical Observatory.
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Title: Temperature, density and magnetic field structure of the
corona during the total eclipse of 1999 August 11
Authors: Habbal, S. R.; Johnson, J.; Nisenson, P.; Woo, R.; Fineschi,
S.; Esser, R.; Wood, C. H.; Hale, J.; Forman, M. A.; Johnson, J. A.;
Jabbour, J.
2000SPD....31.0235H Altcode: 2000BAAS...32..817H
The goal of the eclipse expedition of the Harvard-Smithsonian Center
for Astrophysics on 1999 August 11 to Ayn Diwar in Syria was to explore
the temperature, density and magnetic structure of the corona through
simultaneous imaging in the Fe X 6374, XIV 5303 and XI 7892 Angstroms
lines, the Hα 6563 Angstroms line, and the polarized brightness or
white light. Polarization measurements were made in the Fe XIV 5303
Angstroms and Hα 6563 Angstroms lines to yield the direction of the
coronal magnetic field. Inferences of the temperature distribution
were made from the three iron lines, while density profiles were
derived from the polarized brightness measurements. Supporting
space based observations were acquired with LASCO and UVCS on
SOHO. The comprehensive diagnostic resulting from the analysis of the
observations of the close-to-spherically symmetric corona of 1999
August 11 approaching solar maximum will be presented. Funding for
this research was provided by NSF grant ATM 9521733 to the Smithsonian
Astrophysical Observatory. We acknowledge the generous hospitality
and support bestowed upon the team by the Syrian Ministry of Higher
Education to conduct the experiment in Syria. The digitization of
the photographic film was made with the help of Dr. J. Thornton and
S. Sarafian from the Image Science Laboratory at Polaroid Corporation.
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Title: A High-Eccentricity Low-Mass Companion to HD 89744
Authors: Korzennik, Sylvain G.; Brown, Timothy M.; Fischer, Debra A.;
Nisenson, Peter; Noyes, Robert W.
2000ApJ...533L.147K Altcode: 2000astro.ph..3045K
HD 89744 is an F7 V star with a mass of 1.4 M<SUB>solar</SUB>, an
effective temperature of 6166 K, an age of 2.0 Gyr, and metallicity
[Fe/H]=0.18. The radial velocity of the star has been monitored
with the Advanced Fiber-Optic Echelle spectrograph at the Whipple
Observatory since 1996, and evidence has been found for a low-mass
companion. The data were complemented by additional data from the
Hamilton spectrograph at Lick Observatory during the companion's
periastron passage in the fall of 1999. As a result, we have
determined the star's orbital wobble to have a period P=256 days,
an orbital amplitude K=257 m s<SUP>-1</SUP>, and an eccentricity
e=0.7. From the stellar mass, we infer that the companion has a
minimum mass m<SUB>2</SUB>sini=7.2 M<SUB>J</SUB> in an orbit with a
semimajor axis a<SUB>2</SUB>=0.88 AU. The eccentricity of the orbit,
among the highest known for extrasolar planets, continues the trend
that extrasolar planets with semimajor axes greater than about 0.15 AU
tend to have much higher eccentricities than are found in our solar
system. The high metallicity of the parent star reinforces the trend
that parent stars of extrasolar planets tend to have high metallicity.
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Title: Evidence for Multiple Companions to υ Andromedae
Authors: Butler, R. Paul; Marcy, Geoffrey W.; Fischer, Debra A.;
Brown, Timothy M.; Contos, Adam R.; Korzennik, Sylvain G.; Nisenson,
Peter; Noyes, Robert W.
1999ApJ...526..916B Altcode:
The bright F8 V star υ Andromedae was previously reported to have
a 4.6 day Doppler velocity periodicity, consistent with having a
Jupiter-mass companion orbiting at 0.059 AU. Follow-up observations
by both the Lick and Advanced Fiber-Optic Echelle spectrometer (AFOE)
planet survey programs confirm this periodicity and reveal additional
periodicities at 241 and 1267 days. These periodicities are consistent
with Keplerian orbital motion and imply two additional companions
orbiting at 0.83 and 2.5 AU, with minimum (Msini) masses of 2.0 and
4.6 M<SUB>JUP</SUB>, respectively. Non-Keplerian explanations for the
observed Doppler velocity variations, including radial and nonradial
pulsations, rotational modulation of surface features, and stellar
magnetic cycles, are examined. These explanations seem unlikely
based on the observed photometric and chromospheric stability of the
star. This putative three-planet system is found to be dynamically
stable by both analytic techniques and numerical simulations. The
outer two companions both reside in eccentric orbits, as do all nine
known extrasolar planet candidates in distant orbits. If real, this
multiple-planet system is the first around a main-sequence star, and
its study should offer insights into planet formation, planet-planet
interactions, and the observed eccentricities of planetary orbits. <P
/>Based on observations obtained at Lick Observatory, operated by the
University of California, and at the Whipple Observatory, operated by
the Smithsonian Astrophysical Observatory.
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Title: Evidence for a system of planets orbiting Upsilon Andromedae.
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Holman, M. J.;
Contos, A.; Brown, T. M.
1999BAAS...31.1236N Altcode:
No abstract at ADS
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Title: An Upper Limit on the Reflected Light from the Planet Orbiting
the Star τ Bootis
Authors: Charbonneau, David; Noyes, Robert W.; Korzennik, Sylvain G.;
Nisenson, Peter; Jha, Saurabh; Vogt, Steven S.; Kibrick, Robert I.
1999ApJ...522L.145C Altcode: 1999astro.ph..7195C
The planet orbiting τ Boo at a separation of 0.046 AU could produce
a reflected light flux as bright as 1×10<SUP>-4</SUP> relative to
that of the star. A spectrum of the system will contain a reflected
light component which varies in amplitude and Doppler shift as the
planet orbits the star. Assuming the secondary spectrum is primarily
the reflected stellar spectrum, we can limit the relative reflected
light flux to be less than 5×10<SUP>-5</SUP>. This implies an upper
limit of 0.3 for the planetary geometric albedo near 480 nm, assuming a
planetary radius of 1.2 R<SUB>Jup</SUB>. This albedo is significantly
less than that of any of the giant planets of the solar system and is
not consistent with certain published theoretical predictions.
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Title: Evidence for a System of Planets Orbiting Upsilon Andromedae
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Holman, M. J.;
Contos, A.; Brown, T. M.
1999AAS...194.1404N Altcode: 1999BAAS...31..847N
Using the Advanced Fiber Optic Echelle (AFOE) spectrograph at SAO's
Whipple Observatory, we have monitored the radial velocity of Upsilon
Andromedae since September 1994. Similar observations were made by the
"Lick" group (P. Butler, G. Marcy, D. Fischer; see Paper 14.02).The AFOE
data show, in addition to the already known close-in “hot Jupiter”
in a 4.6-day circular orbit, two additional companions. The middle
companion has a well-defined orbit, with semi-major axis about
0.83 AU, period 243.5 days, eccentricity 0.22, and minimum mass
(M sin i) of 2 Jupiter masses. This is in very close agreement with
independent findings by the Lick group. The AFOE data alone do not
yield well-determined orbital parameters for the outer companion,
because the total observing span encompasses only about one period of
its orbit. However, the data are consistent with parameters derived
for that companion by the Lick group from data with a longer time span,
and when combined with the Lick data yield a semi-major axis of 2.5 AU,
orbital period of 1267 days, eccentricity of 0.41, and minimum mass
about 4.6 Jupiter masses. These results, independently obtained by two
different groups with different instruments and analysis methodologies,
together give strong indications that a true planetary “system” has
now been discovered around a star like our own. We have carried out
numerical integrations which show that this system can be stable, but
only for certain combinations of periods, masses, and eccentricities
of the outer two companions. The stability requirement thus provides
a prediction that can be tested as the orbital elements of the outer
companion are refined. In addition, it imposes an upper limit on the
actual planetary masses, and on the difference in orbital inclination of
the two outer planets. Finally, the numerical integrations imply that
the longitudes of periastron of the two outer companions are locked to
nearly the same value, in accord with the present observations. This
work was supported by NASA, NSF, and the Smithsonian Institution.
---------------------------------------------------------
Title: A Second Bright Source Detected near SN 1987A
Authors: Nisenson, Peter; Papaliolios, Costas
1999ApJ...518L..29N Altcode: 1999astro.ph..4109N
Speckle interferometry observations, made just 30 and 38 days after
the explosion of SN 1987A (which was first seen in 1987 February 23),
showed evidence of a bright source separated from the SN by only 60
mas. The reprocessing of that data, using new image reconstruction
algorithms, has resulted in much cleaner images that not only clearly
show the bright spot reported in 1987 but also show a second spot on
the opposite side of the SN with a larger spatial separation. If the
spots were ejected from the SN, then the velocities of the spots are
relativistic; the second spot appears to be superluminal and must
be blueshifted. We explore the consequences of these results on the
geometry of the SN 1987A system, and we conclude that our observations
may well be evidence of relativistic jets emanating from the supernova.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Double star measurements 1995-1997
(Aristidi+ 1999)
Authors: Aristidi, E.; Prieur, J. -L.; Scardia, M.; Koechlin, L.;
Avila, R.; Carbillet, M.; Lopez, B.; Rabbia, Y.; Nisenson, P.;
Gezari, D.
1999yCat..41340545A Altcode:
We present speckle observations of 48 double and multiple stars observed
with the 2-meter “Telescope Bernard Lyot” (TBL) in December 1995,
January 1997 and June 1997. Angular separations, absolute position
angles and relative photometry result from these observations. New
orbital elements have been recalculated for 8 double stars. (2 data
files).
---------------------------------------------------------
Title: Speckle observations of double and multiple stars at PIC du
Midi: Measurements during 1995 and 1997 and new orbits
Authors: Aristidi, É.; Prieur, J. -L.; Scardia, M.; Koechlin,
L.; Avila, R.; Carbillet, M.; Lopez, B.; Rabbia, Y.; Nisenson, P.;
Gezari, D.
1999A&AS..134..545A Altcode:
We present speckle observations of 48 double and multiple stars observed
with the 2-meter “Télescope Bernard Lyot” (TBL) in December 1995,
January 1997 and June 1997. Angular separations, absolute position
angles and relative photometry result from these observations. New
orbital elements have been recalculated for 8 double stars. Based
on observations made with 2 m Telescope Bernard Lyot, Pic du Midi,
France. Tables 3 to 10 are only available in electronic form only
via the CDS at ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/Abstract.html. Figures 3 and 4 are only
available in electronic form via http://edpsciences.com
---------------------------------------------------------
Title: Doppler Imaging of Stellar Oscillations: Multi-Site
Observations of Epsilon Cephei
Authors: Kennelly, E. J.; Brown, T. M.; Ehrenfreund, P.; Foing,
B.; Hao, J.; Horner, S.; Korzennik, S.; Nisenson, P.; Noyes, R.;
Sonnentrucker, P.
1999ASPC..185..264K Altcode: 1999IAUCo.170..264K; 1999psrv.conf..264K
We investigate the oscillation properties of ɛ Cep using a series of
specialized techniques designed to extract and analyze time variations
in absorption line profiles. To obtain the necessary temporal coverage
for this investigation, multi-site observations were collected at
3 sites (China, France, Arizona) all equipped with high-resolution
echelle spectrographs. From these observations, we find evidence for
a very rich spectrum of modes in ɛ Cep.
---------------------------------------------------------
Title: Dynamics of Magnetic Elements in the Photosphere and the
Formation of Spicules
Authors: van Ballegooijen, A. A.; Nisenson, P.
1999ASPC..183...30V Altcode: 1999hrsp.conf...30V
We consider the proper motions of photospheric magnetic elements, and
the effects of these motions on flows at larger heights. We summarize
the results from recent analyses of high resolution G-band data obtained
at the Swedish Vacuum Solar Telescope (SVST) on La Palma. The G-band
images show small bright features which are known to correspond to
kilogauss magnetic fields. We measure the motions of these bright
points and find that the autocorrelation time of the bright point
velocity is about 100 s. From the observed continuum intensity images,
we derive a model of the granulation flow velocity as function of
time and position on the Sun. We use this flow model to simulate the
horizontal motions of photospheric magnetic elements, assuming that
the elements are passively advected by the granulation flow. We find
that this passive advection model is in reasonable agreement with the
observed spatial distribution of the G-band bright points. Finally, we
use potential-field modeling to extrapolate the magnetic and velocity
fields from the photosphere, where the flux tubes are well separated,
to a height of 1500 km in the chromosphere, where the flux tubes fill
the available volume due to the spreading out of the field lines. We
find that strong shear flows occur near separatrix surfaces where
neighboring flux tubes slide past each other in the chromosphere. We
propose that spicules are formed in these separatrix layers.
---------------------------------------------------------
Title: The Advanced Fiber-Optic Echelle (AFOE) and Extra-Solar
Planet Searches
Authors: Nisenson, P.; Contos, A.; Korzennik, S.; Noyes, R.; Brown, T.
1999ASPC..185..143N Altcode: 1999IAUCo.170..143N; 1999psrv.conf..143N
The Advanced Fiber-Optic Echelle (AFOE) is a fiber-fed bench-top
spectrograph specifically designed for precise radial velocity
observations. The AFOE is permanently located at the 1.5-m telescope
at Smithsonian's Whipple Observatory in Arizona and is regularly used
for monitoring exo-planet candidate stars and for asteroseismology
observations. In this paper, we discuss the status of the instrument,
as well as an upgrade to the instrument, a Fabry-Perot reference,
which may prove important both for the AFOE and for all precise radial
velocity (PRV) facilities.
---------------------------------------------------------
Title: The Planet Orbiting ρ Coronae Borealis
Authors: Noyes, R. W.; Contos, A. R.; Korzennik, S. G.; Nisenson,
P.; Brown, T. M.; Horner, S. D.
1999ASPC..185..162N Altcode: 1999IAUCo.170..162N; 1999psrv.conf..162N
Continuing precise radial velocity observations of ρ Coronae Borealis
have allowed the determination of updated parameters of the 40-day
orbit of its Jupiter-mass companion. This confirms the near-zero
eccentricity of the orbit, and provides improved predictions for the
times of possible transit of the companion in front of the star. The
new data provide more stringent upper limits to the mass of a possible
second companion to the system. The orbital parameters are discussed in
the light of several different scenarios for the origin and migration
of extra-solar giant planets.
---------------------------------------------------------
Title: Dynamics of Magnetic Flux Elements in the Solar Photosphere
Authors: van Ballegooijen, A. A.; Nisenson, P.; Noyes, R. W.; Löfdahl,
M. G.; Stein, R. F.; Nordlund, Å.; Krishnakumar, V.
1998ApJ...509..435V Altcode: 1998astro.ph..2359V
The interaction of magnetic fields and convection is investigated in
the context of the coronal heating problem. We study the motions of
photospheric magnetic elements using a time series of high-resolution
G-band and continuum filtergrams obtained at the Swedish Vacuum
Solar Telescope at La Palma. The G-band images show bright points
arranged in linear structures (“filigree”) located in the lanes
between neighboring granule cells. We measure the motions of these
bright points using an object tracking technique, and we determine
the autocorrelation function describing the temporal variation of
the bright point velocity. The correlation time of the velocity is
about 100 s. To understand the processes that determine the spatial
distribution of the bright points, we perform simulations of horizontal
motions of magnetic flux elements in response to solar granulation
flows. Models of the granulation flow are derived from the observed
granulation intensity images using a simple two-dimensional model
that includes both inertia and horizontal temperature gradients; the
magnetic flux elements are assumed to be passively advected by this
granulation flow. The results suggest that this passive advection model
is in reasonable agreement with the observations, indicating that on
a timescale of 1 hr the flux tubes are not strongly affected by their
anchoring at large depth. Finally, we use potential-field modeling
to extrapolate the magnetic and velocity fields to larger height. We
find that the velocity in the chromosphere can be locally enhanced at
the separatrix surfaces between neighboring flux tubes. The predicted
velocities are several km s<SUP>-1</SUP>, significantly larger than
those of the photospheric flux tubes. The implications of these results
for coronal heating are discussed.
---------------------------------------------------------
Title: Exoplanets or Dynamic Atmospheres? The Radial Velocity and
Line Shape Variations of 51 Pegasi and τ Bootis
Authors: Brown, Timothy M.; Kotak, Rubina; Horner, Scott D.;
J. Kennelly, Edward; Korzennik, Sylvain; Nisenson, P.; Noyes, Robert W.
1998ApJS..117..563B Altcode: 1998astro.ph..1166B
The stars 51 Pegasi and τ Bootis show radial velocity variations that
have been interpreted as resulting from companions with roughly Jovian
mass and orbital periods of a few days. Gray and Gray & Hatzes
reported that the radial velocity signal of 51 Peg is synchronous with
variations in the shape of the line λ6253 Fe I; thus, they argue that
the velocity signal arises not from a companion of planetary mass but
from dynamic processes in the atmosphere of the star, possibly nonradial
pulsations. Here we seek confirming evidence for line shape or strength
variations in both 51 Peg and τ Boo, using R = 50,000 observations
taken with the Advanced Fiber Optic Echelle. Because of our relatively
low spectral resolution, we compare our observations with Gray's line
bisector data by fitting observed line profiles to an expansion in terms
of orthogonal (Hermite) functions. To obtain an accurate comparison,
we model the emergent line profiles from rotating and pulsating stars,
taking the instrumental point-spread function into account. We describe
this modeling process in detail. We find no evidence for line profile or
strength variations at the radial velocity period in either 51 Peg or in
τ Boo. For 51 Peg, our upper limit for line shape variations with 4.23
day periodicity is small enough to exclude with 10 σ confidence the
bisector curvature signal reported by Gray & Hatzes; the bisector
span and relative line depth signals reported by Gray are also not seen,
but in this case with marginal (2 σ) confidence. We cannot, however,
exclude pulsations as the source of 51 Peg's radial velocity variation
because our models imply that line shape variations associated with
pulsations should be much smaller than those computed by Gray &
Hatzes; these smaller signals are below the detection limits both for
Gray & Hatzes's data and for our own. τ Boo's large radial velocity
amplitude and v sin i make it easier to test for pulsations in this
star. Again we find no evidence for periodic line shape changes, at a
level that rules out pulsations as the source of the radial velocity
variability. We conclude that the planet hypothesis remains the most
likely explanation for the existing data.
---------------------------------------------------------
Title: Study of Magnetic Structure in the Solar Photosphere and
Chromosphere
Authors: Noyes, Robert W.; Avrett, Eugene; Nisenson, Peter; Uitenbroek,
Han; van Ballegooijen, Adriaan
1998nasa.reptV....N Altcode:
This grant funded an observational and theoretical program to study the
structure and dynamics of the solar photosphere and low chromosphere,
and the spectral signatures that result. The overall goal is to learn
about mechanisms that cause heating of the overlying atmosphere, and
produce variability of solar emission in spectral regions important
for astrophysics and space physics. The program exploited two new
ground-based observational capabilities: one using the Swedish Solar
Telescope on La Palma for very high angular resolution observations
of the photospheric intensity field (granulation) and proxies of the
magnetic field (G-band images); and the other using the Near Infrared
Magnetograph at the McMath-Pierce Solar Facility to map the spatial
variation and dynamic behavior of the solar temperature minimum
region using infrared CO lines. We have interpreted these data using
a variety of theoretical and modelling approaches, some developed
especially for this project. Previous annual reports cover the work
done up to 31 May 1997. This final report summarizes our work for the
entire period, including the period of no-cost extension from 1 June
1997 through September 30 1997. In Section 2 we discuss observations
and modelling of the photospheric flowfields and their consequences
for heating of the overlying atmosphere, and in Section 3 we discuss
imaging spectroscopy of the CO lines at 4.67 mu.
---------------------------------------------------------
Title: The Oscillations of Tau Pegasi
Authors: Kennelly, E. J.; Brown, T. M.; Kotak, R.; Sigut, T. A. A.;
Horner, S. D.; Korzennik, S. G.; Nisenson, P.; Noyes, R. W.; Walker,
A.; Yang, S.
1998ApJ...495..440K Altcode:
We present extensive spectroscopic time series observations of the
multiperiodic, rapidly rotating, δ Scuti star τ Pegasi. Information
about the oscillations is contained within the patterns of line-profile
variation of the star's blended absorption-line spectrum. We introduce
the new technique of Doppler deconvolution with which to extract these
patterns by modeling the intrinsic stellar spectrum and the broadening
functions for each spectrum in the time series. Frequencies and modes
of oscillation are identified from the variations using the technique
of Fourier-Doppler imaging and a two-dimensional least-squares cleaning
algorithm. We find a rich mode spectrum with degrees up to l = 20 and
with frequencies below about 35 cycles day<SUP>-1</SUP>. Those modes
with the largest amplitudes have frequencies that lie within a narrow
band. We conclude that the observed spectrum can be explained if the
modes of τ Peg propagate in the prograde direction with l ~= |m| and
with frequencies that are about equal in the corotating frame of the
star. We discuss the implications of these results for the prospect
of δ Scuti seismology.
---------------------------------------------------------
Title: A Search for Line Shape and Depth Variations in 51 Pegasi
and τ Bootis
Authors: Brown, Timothy M.; Kotak, Rubina; Horner, Scott D.; Kennelly,
Edward J.; Korzennik, Sylvain; Nisenson, P.; Noyes, Robert W.
1998ApJ...494L..85B Altcode: 1997astro.ph.12279B
Spectroscopic observations of 51 Pegasi and τ Bootis show no periodic
changes in the shapes of their line profiles; these results for 51
Peg are in significant conflict with those reported by Gray &
Hatzes. Our detection limits are small enough to rule out nonradial
pulsations as the cause of the variability in τ Boo, but not in 51
Peg. The absence of line shape changes is consistent with these stars'
radial velocity variability arising from planetary mass companions.
---------------------------------------------------------
Title: Exoplanet Research with the Advanced Fiber Optic Echelle
Authors: Korzennik, S. G.; Brown, T. M.; Contos, A. R.; Horner, S.;
Jha, S.; Kennelly, T.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..154.1876K Altcode: 1998csss...10.1876K
The AFOE is a fiber-fed bench-top echelle spectrometer installed
at the Mt. Hopkins 1.5 m telescope for research in exoplanets,
asteroseismology, and other topics requiring precise radial velocity
measurements. Here we describe the instrumentation, observing programs,
and data reduction techniques for exoplanet research with the AFOE. We
also summarize recent results of our search for and characterization
of exoplanets. Further information on the AFOE can be found on the
Web at http://cfa-www.harvard.edu/afoe.
---------------------------------------------------------
Title: Temperatures of Cepheids from Line-Depth Ratios
Authors: Krockenberger, M.; Sasselov, D.; Noyes, R.; Korzennik, S.;
Nisenson, P.; Brown, T.; Kennelly, T.; Horner, S.
1998ASPC..154..791K Altcode: 1998csss...10..791K
We present observations of 11 Cepheids and 16 non-variable supergiants
with the Advanced Fiber Optics Echelle (AFOE) spectrograph. We measure
the effective temperatures of Cepheids and supergiants using spectral
line depth ratios and Kurucz's model atmospheres. For the Cepheids we
use the fact that the reddening is constant as a function of phase as an
additional constraint. We find errors in the mean temperature as small
as 10 K for the best sampled Cepheids. Our temperatures and surface
brightnesses disagree with the results of the Barnes-Evans method.
---------------------------------------------------------
Title: 51 Pegasi and Tau Bootis: Planets or Pulsations?
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Kotak, R.; Jha,
S.; Korzennik, S. G.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..135..206H Altcode: 1998hcsp.conf..206H
It has recently been suggested (Gray 1997) that the radial velocity
variations observed in the spectra of 51 Pegasi are the result of
stellar pulsations as opposed to the reflex motion due to an orbital
companion. The AFOE group has confirmed the radial velocity variations
in 51 Pegasi and t Bootis. Here we discuss the results of a search for
evidence of pulsations in the AFOE data for these two stars, as well
as attempt to clear up misconceptions regarding pulsations circulated
as a result of the current debate about the nature of the 51 Pegasi
radial velocity variations.
---------------------------------------------------------
Title: 51 Pegasi and Tau Bootis: Planets or Pulsations?
Authors: Horner, S. D.; Brown, T. M.; Kennedy, E. J.; Kotak, R.; Jha,
S.; Korzennik, S. G.; Krockenberger, M.; Nisenson, P.; Noyes, R. W.
1998ASPC..154.1860H Altcode: 1998csss...10.1860H
Using data from the AFOE and simulations of pulsating stars, we are able
to rule out pulsations as the cause of the radial velocity variations
seen in tau Bootis and conclude that it is unlikely that pulsations
are the cause of radial velocity variations seen in 51 Pegasi. Orbital
companions are still the most probable causes of the radial velocity
variations observed in these systems.
---------------------------------------------------------
Title: Asteroseismology of Procyon with the AFOE
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Korzennik,
S.; Nisenson, P.; Noyes, R. W.
1997AAS...191.4310H Altcode: 1997BAAS...29R1276H
The Advanced Fiber Optic Echelle (AFOE) is a bench-mounted,
fiber-fed echelle spectrograph designed for precision radial velocity
observations. Located at the 1.5m Tillinghast telescope at Whipple
Observatory, the AFOE is used to detect exoplanets and is involved in
several projects in asteroseismology, including asteroseismology of
Sun-like stars. Procyon has been a prime target for asteroseismology
of Sun-like stars due to its proximity and its spectral type
(F5 IV-V). Theory predicts that due to its low surface gravity
and inefficient surface convection, the amplitudes of its p-mode
pulsation modes should be relatively large, though still less than 1
m\ s(-1) . While the velocity of individual modes is extremely small,
observations of Procyon with the AFOE show excess power in the frequency
range between 0.5 to 1.5 MHz. This power may be the result of p-mode
oscillations on Procyon, and is consistent with previous results (Brown
et al. 1991). However, mode identification is required to interpret
the ramifications of the observations for the star's structure, which
is the goal of asteroseismology. These single-site data are limited
in frequency resolution, which may prevent clear identification of
individual modes.
---------------------------------------------------------
Title: Erratum: A Planet Orbiting the Star Rho Coronae Borealis:
Authors: Noyes, Robert W.; Jha, Saurabh; Korzennik, Sylvain G.;
Krockenberger, Martin; Nisenson, Peter; Brown, Timothy M.; Kennelly,
Edward J.; Horner, Scott D.
1997ApJ...487L.195N Altcode:
In the Letter, “A Planet Orbiting the Star ρ Coronae Borealis”
by Robert W. Noyes, Saurabh Jha, Sylvain G. Korzennik, Martin
Krockenberger, Peter Nisenson, Timothy M. Brown, Edward J. Kennelly,
and Scott D. Horner (ApJ, 483, L111 [1997]), a software error caused
the sign of the reported radial velocity variations of ρ Coronae
Borealis to be reversed. This error has no effect on the period,
amplitude, or eccentricity of the derived orbit and thus does not
affect the main conclusion of the paper. However, the longitude ω
of periastron reported in Table 1 is off by 180°, and the predicted
time of a possible planetary transit T<SUB>transit</SUB> is off by
approximately 1/2 period. The correct values are ω = 30° +/- 74°
and T<SUB>transit</SUB> = 2,450,657.88 +/- 0.54 HJD.
---------------------------------------------------------
Title: A Planet Orbiting the Star ρ Coronae Borealis
Authors: Noyes, Robert W.; Jha, Saurabh; Korzennik, Sylvain G.;
Krockenberger, Martin; Nisenson, Peter; Brown, Timothy M.; Kennelly,
Edward J.; Horner, Scott D.
1997ApJ...483L.111N Altcode: 1997astro.ph..4248N
We report the discovery of near-sinusoidal radial velocity variations
of the G0V star ρ CrB, with period 39.6 days and amplitude 67 m
s<SUP>-1</SUP>. These variations are consistent with the existence
of an orbital companion in a circular orbit. Adopting a mass of 1.0
M<SUB>solar</SUB> for the primary, the companion has minimum mass
about 1.1 Jupiter masses and orbital radius about 0.23 AU. Such an
orbital radius is too large for tidal circularization of an initially
eccentric orbit during the lifetime of the star, and hence we suggest
that the low eccentricity is primordial, as would be expected for a
planet formed in a dissipative circumstellar disk.
---------------------------------------------------------
Title: A Radial Velocity Search for p-Mode Pulsations in η Bootis
Authors: Brown, Timothy M.; Kennelly, Edward J.; Korzennik, Sylvain
G.; Nisenson, Peter; Noyes, Robert W.; Horner, Scott D.
1997ApJ...475..322B Altcode:
The subgiant η Boo (G5 IV) has been reported to show p-mode pulsations,
as evidenced by variations in the equivalent width of its hydrogen
Balmer lines (reported by Kjeldsen et al.). In an attempt to confirm
this report, we observed η Boo's radial velocity with the AFOE
spectrograph for a total of 22 hours spread over seven successive
nights in 1995 March. We find no evidence for the presence of excess
power at the frequencies reported by Kjeldsen et al.; our upper limit
corresponds to typical mode amplitudes of 0.5 m s<SUP>-1</SUP>, about 3
times smaller than the velocity amplitudes they inferred. Signals with
amplitudes larger than 0.5 m s<SUP>-1</SUP> may be present at other
frequencies within the 0-1000 μHz range, but evidence for such signals
is scanty, and typical mode amplitudes greater than 1.5 m s<SUP>-1</SUP>
are clearly inconsistent with our observations.
---------------------------------------------------------
Title: The AFOE Program of Extra-Solar Planet Research
Authors: Noyes, R.; Jha, S.; Korzennik, S.; Krockenberger, M.;
Nisenson, P.; Brown, T.; Kennelly, E.; Horner, S.
1997ASPC..119..119N Altcode: 1997pbss.conf..119N
No abstract at ADS
---------------------------------------------------------
Title: A radial velocity search for p-modes in Procyon.
Authors: Brown, T. M.; Kennelly, E. J.; Noyes, R. W.; Korzennik,
S. G.; Nisenson, P.; Horner, S. D.; Catala, C.
1996BAAS...28..917B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The oscillation modes of ɛ Cep and τ Peg.
Authors: Horner, S. D.; Kennelly, E. J.; Brown, T. M.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Yang, S.; Walker, A. R.
1996BAAS...28..916H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Oscillation Modes of epsilon CEP and tau Peg
Authors: Horner, S. D.; Kennelly, E. J.; Brown, T. M.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Yang, S.; Walker, A.
1996AAS...188.5901H Altcode: 1996BAAS...28Q.917H
Asteroseismology of delta Scuti stars offers an attractive prospect for
determining the interior properties of main sequence and slightly more
evolved A- and F-type stars. Here we present detailed identifications
of oscillation modes in the rapidly rotating delta Scuti stars epsilon
Cep and tau Peg based on extensive observations carried out at two
North American sites. Using cross-correlation and Fourier techniques
we analyze the line-profile variations and the variations in the
line-profile moments. A solution to the mode spectrum is sought using
a genetic-based search algorithm and a line profile simulation model
to reproduce the observed variations.
---------------------------------------------------------
Title: Use of Temperature-Sensitive Line Ratios for Stellar Seismology
Authors: Noyes, R. W.; Korzennik, S. G.; Krockenberger, M.; Nisenson,
P.; Brown, T.; Kennelly, T.; Horner, S.
1996AAS...188.5906N Altcode: 1996BAAS...28..918N
The line depths of virtually all stellar spectral lines are sensitive
to small changes in stellar temperature T<SUB>eff</SUB> induced by
pulsations, with varying degrees (and signs) depending on the mean
T<SUB>eff</SUB> and the line ionization and excitation state. For
large-amplitude pulsators, such as Cepheids, temperatures obtained
from individual line pairs are sufficiently accurate and invariant
to reddening to play an important role in distance measurements. For
small-amplitude pulsators, this technique is inadequate. However,
by combining the information from a very large number of spectral
lines recorded with high spectral resolution, such as can be provided
by a cross-dispersed echelle spectrograph, it should be possible to
measure temperature changes to a precision considerably greater than
can be obtained by comparing single pairs of lines. We explore this
possibility by using a grid of synthetic stellar spectra to provide the
run of temperature sensitivity as a function of wavelength throughout
the spectrum, and make specific application to spectra obtained with
the Advanced Fiber Optic Echelle (AFOE) spectrograph.
---------------------------------------------------------
Title: A Radial Velocity Search for p-modes in Procyon
Authors: Brown, T. M.; Kennelly, E. J.; Noyes, R. W.; Korzennik,
S. G.; Nisenson, P.; Horner, S. D.; Catala, C.
1996AAS...188.5902B Altcode: 1996BAAS...28R.917B
Procyon (alpha CMi F5 IV) has long been a promising candidate for
detection of solar-like p-modes. Although several authors have reported
evidence for low-amplitude (<= 10) m/s pulsations in this star,
none of the existing observations are conclusive. A clear detection
of such pulsations would be a significant step for asteroseismology
of Sun-like stars, allowing refined estimates of the star's properties
and paving the way for the study of fainter stars of similar spectral
type. Identification of oscillation modes in subgiants like Procyon is
expected to be difficult, however, because both the amplitudes and the
frequency separations of the modes are expected to be small. To address
these difficulties, we organized a joint observing campaign involving
the AFOE spectrograph located at the Whipple Observatory (Mt. Hopkins,
AZ) and the MUSICOS spectrograph located at Pic du Midi. Both
instruments are capable of providing Doppler measurements with the
required precision of a few m/s, and the 7 hour longitude separation
between them allows the acquisition of relatively long uninterrupted
data strings. In the event, bad weather prevented more than sporadic
observations from Pic du Midi. At Mt. Hopkins, however, we obtained
good observations on each of 6 consecutive nights 3-8 Feb 1996, for
a total of 47 h of observing time. We discuss here the interpretation
of this data set in terms of possible p-mode oscillations.
---------------------------------------------------------
Title: HD 3346
Authors: Noyes, R.; Korzennik, S.; Nisenson, P.; Jha, S.;
Krockenberger, M.; Brown, T.; Kennelly, T.; Rowland, C.; Horner, S.
1996IAUC.6316....1N Altcode: 1996IAUC.6316Q...1N
R. Noyes, S. Korzennik, P. Nisenson, S. Jha, and M. Krockenberger,
Smithsonian Astrophysical Observatory; T. Brown, T. Kennelly, and
C. Rowland, High Altitude Observatory; and S. Horner, Pennsylvania State
University, report the detection of large short- term radial-velocity
variations in the K5 III star HD 3346 = HR 152. Irregularly spaced
observations were made with the Advanced Fiber Optic Echelle (AFOE)
spectrometer at the 1.5-m telescope of the Whipple Observatory during
the last quarters of 1993, 1994, and 1995, with more intensive
observations in December 1995 and February 1996. A long-period
radial-velocity variation similar to that already reported by McClure
et al. (1985, PASP 97, 740) is seen with amplitude of order 500 m/s
and period of order 650 days. This is consistent with a companion to HD
3346 at orbital distance about 2.5 AU. If the mass of HD 3346 is 5 solar
masses, then this already-reported companion would have projected mass
m sin i about 60 Jupiter masses. The AFOE data reveal the presence of
shorter- term radial-velocity variations superimposed on the 650-day
variation. The amplitude of the variations is in the range 150-300
m/s. Near-nightly observations in December 1995 and February 1996 show
the variations to be consistent with those produced by a second orbital
companion. The window function of the data would allow for its period
to be near 14, 18, 24, or 40 days. Such a short period would imply that
the second companion's orbit would have a semimajor axis between 0.2 and
0.4 AU; the amplitude of the variation implies that (again, if HD 3346
has a mass of 5 solar masses) this second companion has m sin i about
10 Jupiter masses. Acoustic pulsations may be an alternative source of
the short-term radial-velocity variations. However, the fundamental
period of acoustic pulsations in giants is expected to be only a few
days; the present data could be explained by acoustic pulsations only
if the star has a mass much lower than suggested by standard stellar-
evolution theory. Spurious signals due to rotation of starspots appear
to be unlikely because of the low reported rotational velocity for HD
3346. A definitive period for the short-period radial-velocity variation
may be determinable if other contemporaneous precise radial-velocity
observations of this star exist or can be obtained before the star
disappears behind the sun for this observing season.
---------------------------------------------------------
Title: Estimating the Cramer-Rao Bound for Astronomical Observations:
Application to the Richardson-Lucy Algorithm
Authors: Zaccheo, T. S.; Gonsalves, R. A.; Nisenson, P.; Ebstein, S. M.
1996ApJ...458..742Z Altcode:
This work addresses the problem of assigning confidence intervals to
restored data obtained by applying the Richardson-Lucy algorithm to
astronomical observations. The proposed solution is to estimate the
Cramér-Rao bound, which describes the minimum obtainable mean square
error associated with a given estimate of a parameter. This paper
presents a compact method for describing the bound for Richardson-Lucy
estimates. It was developed based on previously described bounds for
linear restoration techniques such as Wiener filter estimates. Both one-
and two-dimensional examples are presented.
---------------------------------------------------------
Title: A Radial Velocity Search for p-mode Pulsations in eta Bootis
Authors: Noyes, R. W.; Korzennik, S. G.; Nisenson, P.; Brown, T. M.;
Kennelly, E. J.; Horner, S. D.
1995AAS...18710211N Altcode: 1995BAAS...27.1429N
Kjeldsen et al. 1994 (Astron. J 109, 1313 ) have reported the presence
of p-mode pulsations in Balmer line equivalent widths measured in
the spectrum of eta Boo (G5 IV); they give accurate frequencies for
13 modes of oscillation, and estimate velocity amplitudes for these
modes of typically 1.6 m/s. We report here time-series observations of
the radial velocity of eta Boo obtained with the Advanced Fiber Optic
Echelle (AFOE) spectrograph. In March 1995 we obtained 555 spectra
of eta Boo for a total of 21.6 hours of observing time spread over
7 consecutive nights. The radial velocity time series clearly shows
the night-to-night orbital motion of eta Boo; the residual velocities
after removing this motion are typically 10 m/s for single spectra,
a value that is roughly consistent with shot noise limits. The power
spectrum of the time series shows no evidence for Kjeldsen et al.'s
frequencies. With 95 % confidence, we can rule out the presence of these
13 frequencies with typical amplitudes of 0.5 m/s or more. The spectrum
is consistent with pure photon noise, but also with the presence of
pulsations having other frequencies (not those given by Kjeldsen et
al.) and with typical amplitudes as large as about 1.5 m/s. Possible
explanations for the discrepancy between the two results are (a) an
incorrect conversion between the amplitudes of equivalent width and
Doppler pulsations, and (b) a fluke in the noise behavior of one or
both observations.
---------------------------------------------------------
Title: Determining the AFOE's Radial Velocity Precision with Solar
Observations
Authors: Horner, S. D.; Brown, T. M.; Kennelly, E. J.; Noyes, R. W.;
Korzennik, S. G.; Nisenson, P.; Krockenberger, M.
1995AAS...187.7006H Altcode: 1995BAAS...27.1380H
The Advanced Fiber Optic Echelle (AFOE) is an instrument designed
for high precision radial velocity observations to detect extra-solar
planets and study stellar structure through asteroseismology. A 320 mu
m optical fiber is used to obtain solar observations during the day to
determine the precision of the instrument, and to study the relationship
between stellar activity and measured radial velocities. Here we
present the results of our analysis of solar data to determine the
short and long term radial velocity precision of the AFOE.
---------------------------------------------------------
Title: Molecular H 2 Emission in HH 47A: Hubble Space Telescope GHRS
and FOC Observations
Authors: Curiel, Salvador; Raymond, John C.; Wolfire, Mark; Hartigan,
Patrick; Morse, Jon; Schwartz, Richard D.; Nisenson, Peter
1995ApJ...453..322C Altcode:
We present Hubble Space Telescope ultraviolet observations of the bow
shock at the end of the HH 47 stellar jet obtained with the Goddard High
Resolution Spectrograph (GHRS) and the Faint Object Camera (FOC). The
GHRS spectrum shows three prominent emission lines of H<SUB>2</SUB>
which are produced by Lyα fluorescence and one line that we cannot
identify. Fluorescence from Lyman alpha generated in the bow shock and
Mach disk of HH 47A can account for the observed H<SUB>2</SUB> line
fluxes provided that the H<SUB>2</SUB> absorbs about one-third of these
Lyman alpha photons. We find that our FOC image of HH 47A is made up
of about 70% hydrogen two-photon continuum and about 30% fluorescent
H<SUB>2</SUB> emission. This image closely resembles optical [S II]
and Hα images of HH 47A but differs significantly from H<SUB>2</SUB>
images of the region taken at near-infrared wavelengths. This is because
the two-photon continuum and the Lyα photons which drive H<SUB>2</SUB>
fluorescence both originate in the Hα-emitting gas, and the Lyα mean
free path is small. <P />The presence of molecular hydrogen in HH 47A
is difficult to understand. If the H<SUB>2</SUB> forms in a dense
region between the bow shock and the Mach disk, then the emission
should be significantly more blueshifted than observed. Models that
excite H<SUB>2</SUB> using C-shocks or magnetic precursors assume that
molecular hydrogen exists in the preshock gas of HH 47A. However, this
gas lies within the wake of a previous high-velocity ejection from
the star and is exposed to ionizing radiation from the Gum Nebula,
so we would not expect to find any H<SUB>2</SUB> in this region. <P
/>Numerical calculations indicate that the UV H<SUB>2</SUB> line
emission may be produced by either reformed H<SUB>2</SUB> molecules in
the region between the bow shock and the Mach disk or from a C-shock
or magnetic precursor, while the near-infrared H<SUB>2</SUB> emission
observed in HH 47A arises mainly from C-shock or magnetic precursor
along the wings of the bow shock. We propose that the scenario that
best explains the current results is one in which the HH 47A bow shock
is running into a clump of molecular gas which could be either comoving
with the preshock gas or nearly stationary with respect to the ambient
cloud, primary on its more distant face.
---------------------------------------------------------
Title: 51 Pegasi
Authors: Mayor, M.; Queloz, D.; Marcy, G.; Butler, P.; Noyes, R.;
Korzennik, S.; Krockenberger, M.; Nisenson, P.; Brown, T.; Kennelly,
T.; Rowland, C.; Horner, S.; Burki, G.; Burnet, M.; Kunzli, M.
1995IAUC.6251....1M Altcode:
M. Mayor and D. Queloz, Geneva Observatory, have reported the discovery
of a Jupiter-mass object in orbit around the solar-type star 51 Peg. The
announcement was made in Florence on Oct. 6 at the Ninth "Cambridge"
Workshop on "Cool Stars, Stellar Systems, and the Sun". The claim is
based on 18 months of precise Doppler measurements made with the ELODIE
spectrograph of the Observatoire de Haute-Provence. The parameters
of the orbital motion are as follows: P = 4.2293 +/- 0.0011 days,
e = 0 (assumed), K = 0.059 +/- 0.003 km/s, T0 = 2449797.773 +/-
0.036. The minimum mass of the companion is 0.47 +/- 0.02 Jupiter
mass. Alternative explanations for the radial-velocity variation
(pulsation or spot rotation) seem to be ruled out by the absence of any
significant corresponding photometric variation. Following the Oct. 6
announcement, confirmation of the 4.2-day radial-velocity variation
was obtained in mid-October by G. Marcy and P. Butler (San Francisco
State University, University of California at Berkeley) at the Lick
Observatory, as well as by a joint team from the Harvard-Smithsonian
Center for Astrophysics (R. Noyes, S. Korzennik, M. Krockenberger and
P. Nisenson), the High Altitude Observatory (T. Brown, T. Kennelly and
C. Rowland) and Pennsylvania State University (S. Horner). G. Burki,
M. Burnet and M. Kuenzli, Geneva Observatory and Lausanne University,
communicate: "Intensive photometric monitoring of 51 Peg has been
carried out at the European Southern Observatory. There is no evidence
for eclipses in the system. The rms of the V magnitude (on 17 nights)
is 0.037, two comparison stars being used. A 4.2-day photometric
variability larger than 0.002 mag can be ruled out."
---------------------------------------------------------
Title: Nightly Variations of Nonradial Oscillations in the Delta
Scuti Star upsilon Ursae Majoris
Authors: Korzennik, S. G.; Noyes, R. W.; Brown, T.; Nisenson, P.;
Horner, S.
1995ApJ...443L..25K Altcode:
We obtained spectra of the rapidly rotating Delta Scuti star
upsilon UMa with the Advanced Fiber Optic Echelle Spectrometer
(AFOE) on five successive nights in 1993 April, at a cadence of one
spectrum every 5 minutes over time periods averaging 4 hours on each
night. Cross-correlations of the spectra with a template spectrum from
a slowly rotating star of similar spectral type yielded the pattern
of features propagating across the lines, averaged over all spectral
lines recorded. The spacing of the features in wavelength and their
speed of motion across the line profile depend on the azimuthal order
m and frequency v of propagating oscillation modes. Using a Doppler
imaging analysis, we computed nightly absolute value of m-v diagrams;
these show several resolved modes with effective azimuthal order m
ranging from about 2 up to about 11, and frequencies between 130 and
170 microHz (i.e., periods between 2.1 and 1.6 hours). We identify
the observed modes as propagating prograde modes; the corresponding
retrograde modes are not observed. Viewed in a frame corotating
with the star with rotation speed of 116 km/s as derived from these
data, modes with m approximately 7 and with m approximately 11 have
approximately the same frequency (70 microHz). However, their relative
amplitude changes substantially from night to night, suggesting that
(1) the coherence time of the modes is not longer than about 1 day, or
(2) a possible coupling between modes of similar intrinsic frequencies
causes an alternating pattern of modal amplitude, or (3) beats are being
observed between unresolved modes of similar wavelength and frequency.
---------------------------------------------------------
Title: Estimating the Cramer-Rao Bound for Restored Astronomical
Observations
Authors: Zaccheo, T. S.; Gonsalves, R. A.; Ebstein, S. M.; Nisenson, P.
1995ApJ...439L..43Z Altcode:
This work addresses the problem of assigning confidence intervals to
estimated photometry data obtained from astronomical observations. The
proposed solution is to estimate the Cramer-Rao bound, which is an
analytical expression that describes the minimum obtainable mean square
error associated with a given estimate of a parameter. This Letter
presents a compact and simple form for the bound associated with a
linear estimator such as a Wiener filter estimator. A prescription
for estimating the variance associated with each element in a
restored object was developed using an analytical model for observed
data corrupted by either Poisson or Gaussian noise. Both one- and
two-dimensional examples are presented.
---------------------------------------------------------
Title: First 2.2 micron Results From the IOTA Interferometer
Authors: Dyck, H. M.; Benson, J. A.; Carleton, N. P.; Coldwell,
C.; Lacasse, M. G.; Nisenson, P.; Panasyuk, A.; Papaliolios, C.;
Pearlman, M. R.; Reasenberg, R. D.; Traub, W. A.; Xu, A.; Predmore,
C. R.; Schloerb, F. P.; Gibson, D. M.
1995AJ....109..378D Altcode:
We present the first infrared fringe visibility measurements made
with the Infrared Optical Telescope Array on Mt. Hopkins. Effective
temperatures are derived for RX Boo, RS Cnc, and Beta Peg. RX Boo is
the coolest small-amplitude variable giant star to have an effective
temperature determination. We compare the size of its photosphere
at infrared wavelengths with the sizes of its SiO and H20 radio
emission regions. We also discuss initial performance parameters for
the interferometer.
---------------------------------------------------------
Title: The AFOE: A Spectrograph for Precision Doppler Studies
Authors: Brown, Timothy M.; Noyes, Robert W.; Nisenson, Peter;
Korzennik, Sylvain G.; Horner, Scott
1994PASP..106.1285B Altcode:
The Advanced Fiber Optic Echelle (AFOE) is a fiber-fed echelle
spectrograph designed for the measurement of stellar Doppler
shifts. Using a 2k x 2k CCD detector, it samples about 55% of the
wavelength range between 450 nm and 700 nm (20 echelle orders) at a
single shot, with spectral resolution R = 32000 to 70000 at 500 nm,
depending on the slit width employed. The AFOE employs a number of
devices to assure that the calibrations necessary for accurate Doppler
measurements can be properly performed. The most important of these
are: (1) coupling to the telescope via a double-scrambling optical
fiber system; (2) continuous calibration of the wavelength scale and
point-spread function by means of an atomic emission lamp entering the
spectrograph via a separate fiber and/or a molecular iodine absorption
cell; (3) availability of fiber-coupled sunlight for regular calibration
against the solar spectrum; (4) appropriate mechanical design and active
thermal control, yielding good mechanical stability. The AFOE is coupled
to the Tillinghast 1.5-m telescope at the F. L. Whipple Observatory. It
presently achieves S/N = 500 in the continuum near 500 nm in 60s when
observing Arcturus (alpha-Boo, m_V = -0.04). This noise level sets
a limit of about 0.7 ms^-1 to the Doppler precision attainable in
this length of observing time. Currently, our actual frame-to-frame
repeatability is worse than the photon noise limited value by about a
factor of 3 for this bright star, and about 1.5 for stars with m_V =
4. Work is continuing to refine data processing methods so that the
ultimate noise limit may be approached more closely, and to improve
the spectrograph's relatively low efficiency. (SECTION: Astronomical
Instrumentation )
---------------------------------------------------------
Title: Current status of the IOTA interferometer
Authors: Carleton, Nathaniel P.; Traub, Wesley A.; Lacasse, Marc G.;
Nisenson, Peter; Pearlman, Michael R.; Reasenberg, Robert D.; Xu,
Xinqi; Coldwell, Charles M.; Panasyuk, Alexander; Benson, James A.;
Papaliolios, Costas; Predmore, Read; Schloerb, F. P.; Dyck, H. M.;
Gibson, David M.
1994SPIE.2200..152C Altcode: 1994aisi.conf..152C
The first two telescopes of the Infrared-Optical Telescope Array
(IOTA) project are now in place and yielding data at the Smithsonian
Institution's F. L. Whipple Observatory on Mt. Hopkins, near Tucson,
Arizona. The IOTA collectors are 45 cm in diameter, and may be moved to
various stations in an L-shaped configuration with a maximum baseline of
38 m. A third collector will be added as soon as funding permits. Each
light-collector assembly consists of a siderostat feeding a stationary
afocal Cassegrain telescope that produces a 10-X reduced parallel beam,
which is in turn directed vertically downward by a piezo-driven active
mirror that stabilizes the ultimate image position. The reduced beams
enter an evacuated envelope and proceed to the corner of the array,
where they are turned back along one arm for path compensation. The
delay line, in one beam, consists of two parts: one dihedral
reflector positioned in a slew-and-clamp mode to give the major part
of the desired delay; and a second dihedral mounted on an air-bearing
carriage to provide the variable delay that is needed. After delay,
the beams exit from the vacuum and are directed by dichroic mirrors
into the infrared beam-combination and detection system. The visible
light passes on to another area, to the image-tracker detectors and
the visible-light combination and detection system. The beams are
combined in pupil-plane mode on beam splitters. The combined IR beams
are conveyed to two cooled single-element InSb detectors. The combined
visible-light beams are focussed by lenslet arrays onto multimode
optical fibers that lead to the slit of a specially-designed prism
spectrometer. For the visible mode, the delay line is run at several
wavelengths on one side of the zero- path point, so that several cycles
of interference occur across the spectrum. First results were obtained
with the IR system, giving visibilities for several K and M stars,
using 2.2 micrometers radiation on a N-S baseline of 21.2 m. From
these measurements we obtained preliminary estimates of effective
stellar diameters in the K band.
---------------------------------------------------------
Title: High Resolution Measurements from HST Power Spectra
Authors: Nisenson, P.; Falco, E.; Gonsalves, R.; Ebstein, S.
1994rhis.conf..337N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Cramér-Rao Bound - Accuracy of HST Image Restoration
Authors: Gonsalves, R. A.; Zaccheo, T. S.; Ebstein, S. M.; Nisenson, P.
1994rhis.conf..343G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Power Spectral Analysis of HST Gravitational Lens Images
Authors: Nisenson, P.; Falco, E.
1993AAS...183.7208N Altcode: 1993BAAS...25.1403N
Gravitationally lensed QSO's have become important astronomical tools
for a wide range of astrophysical problems. They provide tests of
General Relativity and act as probes of intergalactic matter. They
may allow direct estimates of the Hubble constant from time delay
measurements and could be used to estimate dark matter in galactic
halos. HST (PC) images of gravitational lens systems should provide
improved measurement of positions and fluxes of the QSO images, and
may allow detection and possible characterization of the lensing
galaxies. However, the HST point spread function makes accurate
parameter extraction more difficult. We have found that measurements
made from the power spectra of these relatively simple objects provides
improved accuracy and, in some cases, the discovery of features not
obvious in the raw (or deconvolved) images.
---------------------------------------------------------
Title: Cramer-Rao Bound on Object Estimation from HST Imagery
Authors: Gonsalves, Robert A.; Zaccheo, Scott; Ebstein, Steven M.;
Nisenson, P.
1993AAS...18311302G Altcode: 1993BAAS...25.1459G
When creating an enhanced image or estimating an object's parameters, it
is important to establish the error associated with the processing. The
Cramer-Rao bound is a tool to calculate the error. It gives the
minimum variance that can be achieved by any estimation technique;
when the technique is maximum likelihood, the estimator asymptotically
approaches the bound, as the number of observations becomes large. We
calculate the bound for HST WF/PC imagery and show how it can be used
as an adjoint to any enhancement or estimation algorithm. The bound
is sensitive to the accuracy of the point-spread function (PSF). We
show results for an improved estimation of the PSF.
---------------------------------------------------------
Title: Nightly Variations of Non-Radial Oscillations in the Delta
Scuti Star upsilon UMa
Authors: Korzennik, S.; Noyes, R.; Brown, T.; Nisenson, P.; Horner, S.
1993AAS...183.8405K Altcode: 1993BAAS...25.1423K
We observed the rapidly rotating Delta Scuti star upsilon UMa with the
Advanced Fiber Optic Echelle (AFOE) spectrometer at the Mt. Hopkins
1.5-m telescope on 5 successive nights in April 1993. Spectra covering
a total of 730 Angstroms were obtained at a 5-min cadence over about 4
hours on each night. The rotationally-broadened profiles of unblended
strong lines clearly show previously-seen “bumps" propagating from
the blue side to the red side of the lines. We isolated moving features
for each individual spectrum by subtracting the spectrum from the mean
spectrum for that night, normalizing to the latter. We then calculated
the cross-correlation function between each difference spectrum and
a standard template spectrum, which was a very high signal-to-noise
spectrum of a slowly-rotating star (Procyon) of similar spectral type,
obtained with the same instrument. The cross-correlation combines
the information from all the bumps moving across all spectral lines
(including rotationally-blended lines) into a single function of
displacement from line center, thereby significantly increasing
the signal-to-noise ratio of the moving features. Analysis of
the time-series of cross-correlation functions yields the rate of
propagation of features and their separation in velocity, which may be
interpreted in terms of effective azimuthal wavenumber and oscillation
frequency. Modes are identified by remapping the cross-correlation
functions in terms of longitude and performing two-dimensional Fourier
transforms. For each night a different modal pattern was found, usually
with several modes. The modes have effective azimuthal order m ranging
from about 2 up to about 12, and frequencies between 120 and 170 uHz
(i.e., 2.3 to 1.6 hours), with frequency gradually increasing with
increasing m. The relative amplitude of the different modes changes
substantially from night to night, suggesting either that the coherence
time of the modes is not longer than about a day, or that beats are
being observed between modes of similar wavelength and frequency.
---------------------------------------------------------
Title: Speckle Observations of Mira's Companion
Authors: Karovska, M.; Nisenson, P.; Beletic, J.
1993ApJ...402..311K Altcode:
We present the first speckle interferometric observations of Mira's hot
companion. The companion accretes mass from Mira's wind and provides
an excellent opportunity for studying the accretion processes in
detached binaries. The separation between the components of the system
is crucial for accurate determination of the accretion rate onto the
companion. Speckle measurements of the separation made at three epochs
since 1983 with much higher precision than previous visual observations
show that the companion's distance from Mira is substantially larger
than expected.
---------------------------------------------------------
Title: An Advanced Fiber Optic Echelle Spectrograph for
Asteroseismology
Authors: Noyes, R. W.; Brown, T. M.; Horner, S.; Korzennik, S.;
Nisenson, P.
1993ASPC...42..485N Altcode: 1993gong.conf..485N
No abstract at ADS
---------------------------------------------------------
Title: The AFOE - a new instrument for asteroseismology
Authors: Noyes, R. W.; Brown, T. M.; Horner, S.; Korzennik, S.;
Nisenson, P.
1993ASPC...40..752N Altcode: 1993IAUCo.137..752N; 1993ist..proc..752N
No abstract at ADS
---------------------------------------------------------
Title: Progress with the Infrared-Optical Telescope Array
Authors: Benson, J. A.; Carelton, N. P.; Lacasse, Mg.; Nisenson, P.;
Papaliolios, C.; Pearlman, M. R.; Reasenberg, R. D.; Traub, W. A.;
Dyck, H. M.; Gibson, D. M.; Predmore, R.; Schloerb, F. P.
1992AAS...181.7405B Altcode: 1992BAAS...24.1239B
No abstract at ADS
---------------------------------------------------------
Title: The Infrared Optical Telescope Array: Project Update
Authors: Lacasse, M. G.; Carleton, N. P.; Nisenson, P.; Pearlman, M.;
Reasenberg, R.; Traub, W. A.; Horowitz, P.; Papaliolios, C.; Gibson,
D.; Predmore, R.; Schloerb, F. P.; Strom, S.; Dyck, M.; Ridgeway, S.
1992AAS...180.0912L Altcode: 1992BAAS...24..742L
Smithsonian Astrophysical Observatory, Harvard University, University
of Massachusets-Amherst, University of Wyoming and MIT Lincoln
Laboratory are collaborating to construct and operate an Infrared
Optical Telescope Array (IOTA) at the Smithsonian's Fred L. Whipple
Observatory on Mt. Hopkins south of Tucson, AZ. The array will consist
of 3 light collector assemblies each with apertures of 0.45 meter
diameter on baselines of 5 to 38 meters. The array will operate in the
optical (0.45microns to 0.75microns) and in the infrared (1.25microns
to 2.2microns) as a Michelson interferometer. We present some of the
design considerations which have led us to the current configuration
of this instrument. We examine the current status of the fabrication
and testing of various<SUB>systems.</SUB> We discuss some of the
scientific targets which this instrument will uniquely be suited to
investigate. Early investigations will focus on diameters of single
stars and on orbital parameters for binary star systems. Of particular
interest is the investigation of the diameter as a function of time
and wavelength for radially pulsating stars such as Cepheids. In later
investigations, we will investigate objects with more complex geometries
such as multiple-star systems and disks around stars. We hope eventually
to investigate the structure in the cores of the brightest active
galactic nuclei. The construction phase of the project is nearing
completion. The central building and the array-station foundations
are under construction on Mt. Hopkins. The light collector assemblies
are complete and being tested in Cambridge.Two elements of the array
should see first light later this year.
---------------------------------------------------------
Title: Speckle View of Supernova 1987A and Longperiod Variables
Authors: Karovska, M.; Nisenson, P.
1992ESOC...39..141K Altcode: 1992hrii.conf..141K
No abstract at ADS
---------------------------------------------------------
Title: Single Speckle Frame Imaging Using Ayers-Dainty Blind Iterative
Deconvolution
Authors: Nisenson, P.
1992ESOC...39..299N Altcode: 1992hrii.conf..299N
No abstract at ADS
---------------------------------------------------------
Title: Iterative deconvolution of x ray and optical SNR images
Authors: Nisenson, Peter; Standley, Clive; Hughes, John
1992sao..reptR....N Altcode:
Blind Iterative Deconvolution (BID) is a technique which was
originally developed to correct the degrading effects of atmospheric
turbulence on astronomical images from single short exposure, high
signal-to-noise-ratio frames. At the Center for Astro physics, we
have implemented a version of BID following the general approach of
Ayers and Dainty (1988), but extending the technique to use Wiener
filtering, and developed it for application to high energy images from
Einstein and ROSAT. In the optical, the point spread function (PSF)
that degrades the images is due to a combination of telescope and
atmospheric aberrations. At high energies, the degrading function is
the instrument response function, which is known to be time and energy
level unstable. In both cases, the PSF is poorly known, so BID can be
used to extract the PSF from the image and then deconvolve the blurred
image to produce a sharpened image. Other aspects of this technique
are discussed.
---------------------------------------------------------
Title: The effects of limb variation on the diameter measurements
of SN 1987A.
Authors: Karovska, M.; Nisenson, P.
1992A&A...253..210K Altcode:
We explore the effects of model brightness distributions on the
estimated diameter from measurements of the supernova SN 1987A
envelope. The measurements were made using speckle interferometry
techniques 265 days after the explosion. The results of this study
show strong dependence of the diameter estimates for different model
profiles. We conclude that the choice of the intensity distribution
profile has an essential role in accurate determination of the supernova
envelope diameter.
---------------------------------------------------------
Title: HST image processing: an overview of algorithms for image
restoration
Authors: Gonsalves, Robert A.; Nisenson, Peter
1991SPIE.1567..294G Altcode:
After the Hubble Space Telescope was stabilized so that it could image
a star, scientists were dismayed to find that the telescope produced
severely degraded images. A flaw in the manufacture of the primary
mirror causes an aberration that appears to be circularly symmetric. In
this paper we review some of the algorithms and procedures that have
been used to perform image restoration of the Hubble data.
---------------------------------------------------------
Title: Speckle Observations of Mira's Companion
Authors: Karovska, M.; Nisenson, P.; Beletic, J.
1991BAAS...23.1380K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Asymmetries in the Atmosphere of Mira
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Boyle, R. P.
1991ApJ...374L..51K Altcode:
A two-dimensional high angular resolution study of Omicron Ceti (Mira),
carried out at four epochs from November 1983 to November 1988 using
speckle interferometry techniques, detected asymmetries in the extended
atmosphere of this pulsating star. The reconstructed speckle images
show that the strength and the shape of this asymmetry changes as
a function of wavelength and time. The position angles of the major
axes of the asymmetries at different epochs are determined and the
axes were measured accurately as a function of wavelength. The origin
of the observed asymmetries has not yet been identified. Plausible
causes include instabilities in the pulsating atmosphere, nonspherical
pulsation, or the interaction with the nearby companion.
---------------------------------------------------------
Title: HST image processing - An overview of algorithms for image
restoration
Authors: Gonsalves, Robert A.; Nisenson, Peter
1991adip.proc..294G Altcode:
An account is given of the algorithms that have been devised and the
procedures that have been performed to achieve image restoration on the
HST. The techniques employed are the inverse and Wiener filters, and
the methods encompass those of constrained-iterative, Richardson-Lucy,
blind deconvolution, and maximum entropy type. The blind deconvolution
method is noted to be especially powerful.
---------------------------------------------------------
Title: A Wiener Filter Version of Blind Iterative Deconvolution
Authors: Nisenson, P.; Standley, C.; Gay, D.
1991rhis.conf..103N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements of the Diameter of the Supernova SN 1987A
Authors: Karovska, M.; Nisenson, P.; Standley, C.; Heathcote, S. R.
1991ApJ...367L..15K Altcode:
We present speckle interferometric measurements of the angular diameter
of SN 1987A in the Large Magellanic Cloud obtained at 664 days after
the outburst. Diameters were estimated with milliarcsecond precision
at 657 nm and 550 nm by fitting model visibility functions to the data
corresponding to different intensity distributions for the supernova
disk. Measurements made assuming a uniform intensity distribution were
compared to the uniform disk measurements obtained from 30 days after
the explosion. Diameter measurements obtained near the center of the
Hα line are consistent with homologous expansion of the supernova
shell with a mean velocity of 2850 km s^-1^. The linear least-squares
fit to the measurements obtained at other wavelengths from 260 days
after the explosion yielded a somewhat lower mean expansion velocity.
---------------------------------------------------------
Title: High resolution optical imaging through the atmosphere
Authors: Noyes, R. W.; Nisenson, P.; Stachnik, R. V.; Papaliolios, C.
1989sao..rept.....N Altcode:
This program has concentrated on three major areas: the application
of high angular resolution image reconstruction techniques to the
reconstruction of solar surface features; speckle imaging of a wide
range of astronomical sources; and the implementation of adaptive
optics for faint object imaging. Substantial modifications were made
to a technique for reconstruction of high resolution images from single
short exposure solar frames, blind iterative deconvolution (IDC). These
improvements were tested using numerical simulation data. Analysis of
speckle data of the supernova SN1987A has detected a new bright source,
0.9 arcseconds south of the SN, as well as substantial structure in
the region surrounding the SN. New results were obtained on several
Young Stellar Objects and supergiants. In the area of adaptive
optics, an AOA wavefront sensor has been set up and tested using an
image intensifier which increases its sensitivity by three orders of
magnitude. Faint object image active tilt correction was also tested
with some important enhancements, including new highly linear and
sensitive CCD quad cells developed by Cal Tech and Tektronix, and
an off-the-shelf high speed 2-D tilting mirror with greatly improved
specifications. The effects of only partially correcting atmospheric
turbulence have been theoretically analyzed and numerically simulated.
---------------------------------------------------------
Title: Astronomical Image Processing with Iterative Deconvolution
Authors: Nisenson, P.; Standley, C.; Hughes, J.
1989BAAS...21.1072N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurement of Limb-Darkening/Brightening and Asymmetry of
Mira's Extended Atmosphere
Authors: Karovska, M.; Nisenson, P.; Standley, C.; Heathcote, S.
1989BAAS...21.1117K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Second Generation PAPA Detector
Authors: Standley, C.; Nisenson, P.
1989BAAS...21.1072S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Standley, C.; Heathcote, S.
1989IAUC.4837....1K Altcode: 1989IAUC.4837....0K
M. Karovska, P. Nisenson and C. Standley, Center for Astrophysics;
and S. Heathcote, Cerro Tololo Interamerican Observatory, report:
"New measurements of the diameter of SN 1987A were made from speckle
data obtained at the CTIO 4-m telescope in 1988 Dec. (IAUC 4749)
using a 35-nm bandpass centered at 551 nm. The diameters obtained at
657/7 nm and 551/35 nm are 0".042 +/- 0".002 and 0".046 +/- 0".002,
respectively. The mean velocity of expansion calculated from these
measurements is in agreement with previously reported measurements
(2850 km/s: IAUC 4604). Reconstructed images from the 551/35 nm data
reveal complex arclike structures within 2" of the supernova. The
images clearly show the presence of a number of bright knots in the
structures. These arcs are very similar to those described by Crotts
et al. (IAUC 4791) in CCD images obtained in 1989 Mar. These images
are suggestive of separated concentric rings around SN 1987A and may
be due to a light echo or fluorescence from material located behind
the supernova in two discrete shells. These shells could be a result
of episodic mass loss during the red-supergiant stage of evolution
of the progenitor star. If this interpretation is correct, one would
expect to observe a contraction of the rings by the current epoch."
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Burrows, C.; Karovska, M.; Nisenson, P.; Standley, C.;
Bailyn, C.; Heathcote, S.
1989IAUC.4781....1B Altcode: 1989IAUC.4781....0B
C. Burrows, Space Telescope Science Institute; and Astrophysics
Division, ESA Space Science Department, reports: "CCD coronagraphic
images taken with the 2.2-m telescope at the European Southern
Observatory on 1988 Sept. 8 contain 16 pointlike sources down to a
limit of 20 mag in a 20" x 30" region centered on the supernova. All
these sources appear consistent photometrically and astrometrically with
sources present on the pre-explosion digitized plate No. 4858 referred
to by Walborn et al. (1987, Ap.J. 321, L41). After subtraction of
these sources, all the remaining structure in the field is consistent
with fainter background stars present in both residual images. This
shows that there is no apparent light echo with an annular morphology
and a thickness of 1" to 3" in the angular range 5" to 10" from the
supernova to a limit of R = 22 mag per square arcsec, and it appears
inconsistent with a sheet or spherical shell of dust as being the cause
of the inner echo reported by Bond et al. (IAUC 4733)." M. Karovska,
P. Nisenson, C. Standley and C. Bailyn, Center for Astrophysics; and
S. Heathcote, Cerro Tololo Interamerican Observatory, communicate:
"The position of maximum brightness of SN 1987A determined from speckle
(1988 Dec., IAUC 4749) and CCD (1989 Mar., IAUC 4753) images obtained at
the CTIO 4-m telescope shows evidence for a displacement of 0".15 +/-
0".07 from the astrometric position of star 1 as measured by Testor
(1987, A.Ap. 190, L1) and Heap et al. (1987, A.Ap. 185, L10) in the
pre-explosion images of the Sk -69 202 complex. The possibility of
extended structure around the supernova may result in an additional
systematic error in the position of the supernova itself not included
in the above error estimates. Analysis of pre-supernova plates suggested
that star 1 may be composed of two stars (Testor; Heap et al.) separated
in the north-south direction and allows a possibility that one of
the components survived the explosion. Assuming the supernova itself
continued to decay at the same rate as it did during the period from
day 500 to approximately day 600, the change in slope after day 600
can be explained by the presence of the other star. In this case
the visible lightcurve is well fit by including a star with V = 13.4,
probably a supergiant of a spectral type between late A and early G. The
pre-explosion magnitude of the B supergiant that became SN 1987A would
then have been V = 12.8. Extrapolation of this fit predicts that the
lightcurve will flatten out by mid-July."
---------------------------------------------------------
Title: Measurements of the Diameter of the Large Magellanic Cloud
Supernova SN 1987A
Authors: Karovska, M.; Koechlin, L.; Nisenson, P.; Papaliolios, C.;
Standley, C.
1989ApJ...340..435K Altcode:
We present direct measurements of the angular diameter of SN 1987A in
the Large Magellanic Cloud (LMC) made from high-angular resolution
observations at the CTIO 4 m telescope in five observing runs from
1987 April to 1988 April. Diameters were determined to milliarcsecond
precision from integrated power spectra, using speckle interferometric
data. The accuracy of the technique was evaluated by laboratory
experiments and measurements of the diameters of several stars of known
angular size. The SN 1987A diameters measured near the center of the
Hα line show clear evolution during this period. The rate at which
the supernova size changed at this wavelength corresponds to 2850 km
s^-1^ mean velocity of expansion. Diameter measurements obtained in
several spectral lines and in the continuum indicate stratification
of the expanding envelope of the supernova. Our continuum data yield
diameters substantially larger than those calculated from photometric
measurements and a blackbody fit to the observed spectra.
---------------------------------------------------------
Title: Asymmetry of the envelope of supernova 1987A
Authors: Papaliolios, C.; Karovska, M.; Koechlin, L.; Nisenson, P.;
Standley, C.; Heathcote, S.
1989Natur.338..565P Altcode: 1989Nat...338..565P
The supernova SN1987A in the Large Magellanic Cloud has been observed
by high-angular-resolution speckle interferometry since 25 March (30
days after the explosion) with the 4-m telescope at the Cerro Tololo
Interamerican Observatory. These observations have provided a number
of results that may be central to a detailed understanding of this
unique event. Data obtained on 25 March and 2 April 1987 revealed
a second bright 'companion' source separated from the supernova by
60 milliarcseconds and less than three magnitudes fainter than the
supernova<SUP>1</SUP>. Measurements of the average diameter of the
supernova envelope have been made from data recorded from March 1987
to April 1988<SUP>2</SUP>. Here we present a more detailed analysis of
these data, which shows that the expanding envelope is asymmetric. This
asymmetry has been observable since June 1987. The ratio between the
minor and major axes of the envelope profile is about 2-3, and the
position angle of the major axis is 20° +/- 5°, consistent with
results reported from polarization measurements. The major axis is
aligned with the position angle of the companion to the supernova.
---------------------------------------------------------
Title: High Angular Resolution Speckle Observations of SN1987A. Days
640 to 700
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.;
Heathcote, S.
1989BAAS...21..787K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.;
Heathcote, S.
1989IAUC.4749....2K Altcode: 1989IAUC.4749....1K; 1989IAUC.4749....0K
M. Karovska, P. Nisenson, C. Papaliolios, and C. Standley, Center for
Astrophysics; and S. Heathcote, Cerro Tololo Interamerican Observatory,
write: "Observations performed on 1988 Dec. 20 with the CTIO 4-m
telescope, the PAPA detector, and speckle image reconstruction
techniques show a source located 0".85 +/- 0".05 from SN 1987A at
position angle 200 +/- 5 deg. The magnitude difference of this source
from the SN is approximately 2.6 in a 35-nm bandpass centered at 551
nm. The separation and p.a. of this source is consistent with the
position of the compact blob reported by Allen et al. (IAUC 4747). It
is also consistent with a position predicted for uniform motion of the
bright source which was detected using speckle techniques on 1987 Apr. 1
(IAUC 4382) and by Matcher et al. on 1987 Apr. 15 (IAUC 4413). We also
detect star 2 (IAUC 4319) separated by 3" from the SN with a magnitude
difference of about 3 (at 551 nm) and p.a. of 315 +/- 5 degrees. We do
not see star 3 (IAUC 4322) in these observations, so it would have to be
at least 4 mag fainter than the SN. We also do not detect any feature
to the north of the SN, as suggested by Allen. These features should
now be observable using direct imaging under good seeing conditions."
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.;
Heathcote, S.
1989IAUC.4752....2K Altcode: 1989IAUC.4752....1K; 1989IAUC.4752....0K
M. Karovska, P. Nisenson, C. Papaliolios, and C. Standley, Center for
Astrophysics; and S. Heathcote, Cerro Tololo Interamerican Observatory,
communicate: "Reduction of speckle data recorded on 1988 Nov. 28 and
1989 Jan. 20 confirms the existence of the bright source near SN 1987A
reported on IAUC 4749 from observations on 1988 Dec. 20. The data were
recorded with the CTIO 4-m telescope, the PAPA detector, and a 35-nm
bandpass centered at 551 nm. The source was located at p.a. 200 +/-
5 deg for all observations. Preliminary estimates of the magnitude
differences (from the SN) and angular separations were: 3.3 +/- 0.2
mag and 0".85 +/- 0".05 (Nov. 28); and 2.1 +/- 0.2 mag and 0".95 +/-
0".05 (Jan. 20). The Dec. result showed that the source was 2.6 +/-
0.2 mag different from the SN and separated by 0".85 +/- 0".05. Data
recorded at other wavelengths are currently being reduced."
---------------------------------------------------------
Title: The Iota Project
Authors: Carleton, N.; Horowitz, P.; Lacasse, M.; Nisenson, P.;
Papaliolios, C.; Reasenberg, R.; Traub, W.; Predmore, R.; Schloerb,
P.; Strom, S.; Gibson, D.; Benson, J.; Dyck, M.
1989BAAS...21..709C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Evidence for asymmetries in SN1987A
Authors: Karovska, M.; Koechlin, L.; Nisenson, P.; Papaliolios, C.;
Standley, C.
1989HiA.....8..193K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle Imaging with the PAPA Detector and the Knox-Thompson
Algorithm
Authors: Nisenson, P.
1989ASIC..274..157N Altcode: 1989dli..conf..157N
No abstract at ADS
---------------------------------------------------------
Title: High Angular Resolution Speckle Observations of SN1987A:
Days 40 to 580
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.
1988BAAS...20..961K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Two-Dimensional 5μm Speckle Interferometry of IRC + 10216
Authors: Nisenson, P.; Stachnik, R.; Gezari, D.
1988BAAS...20.1014N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High Spatial Resolution Observations of Young Stellar Objects
Authors: Salas, L.; Strom, S.; Edwards, S.; Stauffer, J.; Nisenson,
P.; Karovska, M.
1988BAAS...20R1091S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Measurement of Stellar Angular Diameters Smaller than
the Telescope's Diffraction Limit
Authors: Standley, C.; Karovska, M.; Nisenson, P.; Papaliolios, C.
1988BAAS...20R1005S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Koechlin, L.; Nisenson, P.; Papaliolios, C.;
Standley, C.
1988IAUC.4604....1K Altcode: 1988IAUC.4604....0K
M. Karovska, L. Koechlin, P. Nisenson, C. Papaliolios and C. Standley,
Center for Astrophysics, report: "New measurements have been made of SN
1987A, showing a substantial asymmetry in the expanding shell. Speckle
interferometric processing was applied to data that were recorded
using the CTIO 4-m telescope and our PAPA camera speckle system during
Feb. 29-Mar. 2 and Apr. 9-12. Data were recorded in 10-nm passbands at
several wavelengths. We report on results obtained at two wavelengths,
533 nm and 656 nm (H alpha). Previous diameter measurements were
reported on IAUC 4521 and 4457. For those data, azimuthal averages of
the power spectra were performed, and Airy disks were fitted. These
new data are of better quality than the earlier data, mostly due to
better seeing. The higher signal-to-noise and increased size of the
shell have allowed greater accuracy in the measurements. A substantial
asymmetry is observed in displays of the power spectra and in the image
reconstructions. The images are elongated along an axis tilted about
20 degrees from north. The image is 20 to 30 percent longer along this
axis and is somewhat brighter in the southwest direction. Similar
asymmetries have been detected in previous observations, but the
poorer signal-to-noise in those data and the smaller scale of the
SN at the time precluded accurate measurements of the effect. A
summary of the results follows. The azimuthally averaged diameter
in Feb.-Mar. was 0".019 at 533 nm and 0".020 at 656 nm. In Apr. the
diameter was 0".026 at 533 and 0".027 at 656 nm. The 1-sigma error
bars in these measurements are about 0".001. The Feb.-Mar. data give
a 0".017 minor axis and 0".025 major axis (+/- 0".002). In April the
minor axis was 0".025 and the major axis 0".030 (+/- 0".002). Data
recorded on comparison stars gave symmetric power spectra and images
and were unresolved (< 0".001 angular diameter). New measurements
of Alpha Cen A give a diameter of 0".010 +/- 0".001, and the images
show no asymmetry. Photometric estimates for Alpha Cen give a diameter
of 0".009."
---------------------------------------------------------
Title: The Precision Calcium Photometer - a New Instrument for
Asteroseismology
Authors: Nisenson, P.; Dupree, A. K.; Noyes, R. W.
1988IAUS..123..521N Altcode:
The Precision Calcium Photometer has been built with characteristics
optimized for amplitude astroseismology. A description of the instrument
and of laboratory and on-telescope test runs are discussed here.
---------------------------------------------------------
Title: Detection of a Very Bright Source Close to the LMC Supernova
SN 1987A: Erratum
Authors: Nisenson, P.; Papaliolios, C.; Karovska, M.; Noyes, R.
1988ApJ...324L..35N Altcode:
In the Letter "Detection of a Very Bright Source Close to the LMC
Supernova SN 1987A" by P. Nisenson, C. Papaliolios, M. Karovska,
and R. Noyes (1987 Ap. J. [Letters], 320, L15), two of the figure
labels for Figure 1 were inadvertently transposed in the production
process. A corrected version of the figure appears as Plate L4. The
Journal regrets the error.
---------------------------------------------------------
Title: High angular resolution observations of SN 1987A.
Authors: Nisenson, P.; Karovska, M.; Koechlin, L.; Papaliolios, C.;
Standley, C.
1988ESOC...29..491N Altcode: 1988hrii.conf..491N
Using the 4-meter telescope at the Cerro Tololo Interamerican
Observatory, and the technique of speckle interferometry, the authors
have discovered an unexpected second bright source close to SN 1987A
and they have measured the diameter of the expanding shell.
---------------------------------------------------------
Title: Speckle Imaging with the PAPA Detector and the Knox-Thompson
Algorithm
Authors: Nisenson, P.
1988dli..conf..157N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: SN 1987A and companion.
Authors: Papaliolios, Costas; Karovska, Margarita; Nisenson, Peter;
Standley, Clive
1988slmc.proc..225P Altcode:
The diameter of the shell surrounding SN 1987A was measured using the
technique of Davis and Tango (1986). Also, the position of the supernova
relative to Sanduleak -69 deg 202 was determined and the area around
SN 1987A was examined to search for reflected light. It is found that
SN 1987A has a faint companion. The data concerning the magnitude and
position of the companion on March 25 and April 4, 1987 are given. In
addition, the measured diameter of SN 1987A is presented for several
wavelengths between 450 and 775 nm observed on April 2 and June 1, 1987.
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Koechlin, L.; Nisenson, P.; Papaliolios, C.;
Standley, C.; Beresford, A. C.
1987IAUC.4521....1K Altcode: 1987IAUC.4521....0K
M. Karovska, L. Koechlin, P. Nisenson, C. Papaliolios and C. Standley,
Center for Astrophysics, report: "New measurements have been made
of the angular diameter of SN 1987A using speckle interferometric
techniques. The data were recorded on Nov. 17-18 using the 4-m
telescope at Cerro Tololo Interamerican Observatory and our PAPA
camera speckle system. Data were recorded in 10-nm passbands at 533,
640, 656.5, 658.5 and 700 nm. Data were also recorded at 850 nm with
a 250-nm passband. Count rates were adjusted using neutral-density
filters to a level of 50 000 to 70 000 detected photons per second. The
supernova had a visual magnitude of about 5.5 at that time. The result
of least-squares fitting of Airy disks to the integrated power spectra
gives the following diameters: 533 nm, 0".021; 640 nm, 0".020; 656.5
nm, 0".023; 700 nm, 0".024; 850 nm, 0".023. All results have an error
of 0".002. Our measurements made on a G8 star, BS 1008, whose diameter
has been estimated from the blackbody calculation to be 0".019, give a
diameter of 0".019 +/- 0".002. We have also applied the same technique
to comparison stars recorded with the supernova data, and all results
show these stars to be unresolved, as expected. The result at 656.5 nm,
when combined with earlier data sets, appears to fit a linear expansion
velocity of 4000 km/s at 50 kpc, which may well be a direct measure
of the photospheric expansion. The measured diameter is substantially
larger than the value that would be obtained using a blackbody fit to
the spectrum, but such a calculation is only applicable to stars without
extended atmospheres." Visual magnitude estimates by A. C. Beresford,
Adelaide, South Australia: Dec. 24.46 UT, 6.2; 25.48, 6.3; 27.50, 6.4;
28.49, 6.4.
---------------------------------------------------------
Title: Partial atmospheric correction with adaptive optics.
Authors: Nisenson, Peter; Barakat, Richard
1987JOSAA...4.2249N Altcode: 1987OSAJ....4.2249N
The authors have performed some one-dimensional numerical simulations to
test atmospheric wave-front correction when the active element is not
matched to the correlation scale in the pupil. The results demonstrate
that substantial seeing improvement can be obtained with an adaptive
optical system having a limited number of active elements.
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.;
Beresford, A. C.
1987IAUC.4450....1K Altcode: 1987IAUC.4450....0K
M. Karovska, P. Nisenson, C. Papaliolios and C. Standley, Center
for Astrophysics, report: "The angular diameter of SN 1987A has been
determined at three wavelengths from high angular resolution speckle
data obtained on Apr. 2 and at four wavelengths from data recorded
on June 1. These dates were 38 and 98 days, respectively, after
the explosion. Observations were made with the CTIO 4-m telescope
and our speckle camera using the PAPA 2-dimensional photon-counting
detector. Data were recorded in 10-nm passbands centered at 450, 533 and
656 nm (H alpha) on both nights and at 775 nm on June 1. Approximately
30 000 speckle frames were used in each speckle integration for the
SN data sets and the corresponding comparison star data. The power
spectra were first azimuthally averaged, and then the SN power spectra
were deconvolved with the comparison-star power spectra. We performed
a least-squares fit of the Fourier transform of a uniform disk to the
deconvolved SN power spectra. On Apr. 2, at a wavelength of 450 nm,
the angular diameter was 0".010 +/- 0".003, which translates into
a linear diameter of 500 AU (at a distance of 50 kpc) and gives an
expansion velocity of 11 400 km/s; at 533 nm, angular diameter 0".011
+/- 0".004, linear diameter 550 AU, velocity 12 500 km/s; at 656 nm,
angular diameter 0".001 +/- 0".004. On June 1 the corresponding figures
were at 450 nm, 0".019 +/- 0".003, 950 AU, 8400 km/s; at 533 nm,
0".018 +/- 0".004, 900 AU, 8000 km/s; at 656 nm, 0".009 +/- 0".004,
450 AU, 4000 km/s; and at 775 nm, 0".022 +/- 0".005, 1100 AU, 9700
km/s." Visual magnitudes by A. C. Beresford, Adelaide, S. Australia:
Sept. 15.41, 5.1; 16.47, 5.2; 17.47, 5.2; 18.41, 5.3; 19.50, 5.2.
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Catchpole, R.; Glass, I.; Karovska, M.; Nisenson, P.;
Papaliolios, C.; Standley, C.; Flower, T. F.; Seargent, D. A. J.;
McNaught, R. H.
1987IAUC.4457....1C Altcode: 1987IAUC.4457....0C
R. Catchpole, South African Astronomical Observatory, telexes:
"Since it is possible that emission features, in particular the CO
fundamental band at 4.8 microns, may contribute a significant fraction
of the infrared excess in the M band reported by Allen, Whitelock and
Catchpole on IAUC 4453, spectroscopic observations in this band are
very important. An emission feature that may be due to the CO first
overtone at 2.3 microns is seen in a circular- variable-filter spectrum
taken by I. Glass on July 9." M. Karovska, P. Nisenson, C. Papaliolios
and C. Standley, Center for Astrophysics, report: "The measurements
of the diameter of SN 1987A on IAUC 4450 were erroneously scaled by
a factor proportional to the observation wavelength. Correctly scaled
values follow. Apr. 2: 450 nm, 0".012 +/- 0".004, 600 AU, 13 500 km/s;
533 nm, 0".011 +/- 0".004, 550 AU, 12 500 km/s; 656 nm, 0".001 +/-
0".004, -, -. June 1: 450 nm, 0".023 +/- 0".004, 1150 AU, 10 200 km/s;
533 nm, 0".018 +/- 0".004, 900 AU, 8000 km/s; 656 nm, 0".008 +/- 0".004,
400 AU, 3600 km/s; 775 nm, 0".015 +/- 0".004, 750 AU, 6700 km/s. As
a calibration of the accuracy of our measurements of the diameter
of SN 1987A, we measured the diameter of Alpha Cen using speckle
data recorded at the CTIO 4-meter telescope with the PAPA speckle
system. Data were recorded at 533 nm with a 10-nm bandpass. Fitting the
Fourier transform of a uniform disk to the integrated power spectrum
gives an angular diameter of 0".009 +/- 0".002. This is very close
to the diameter of 0".0086 calculated by Blackwell and Shallis (1977,
M.N. 180, 177)." Corrigendum. On IAUC 4452, in the second paragraph,
the name of the observer should read T. F. Flower. Visual magnitudes:
Sept. 23.56 UT, 5.6 (D. A. J. Seargent, The Entrance, N.S.W.); 24.77,
5.4 (R. H. McNaught, Coonabarabran, N.S.W.); 25.54, 5.4 (McNaught);
28.49, 5.5 (Seargent).
---------------------------------------------------------
Title: Detection of a Very Bright Source Close to the LMC Supernova
SN 1987A
Authors: Nisenson, P.; Papaliolios, C.; Karovska, M.; Noyes, R.
1987ApJ...320L..15N Altcode:
High angular resolution observations of the supernova in the Large
Magellanic Cloud, SN 1987A, have revealed a bright source separated
from the SN by approximately 60 mas with a magnitude difference of 2.7
at 656 nm (H-alpha). Speckle imaging techniques were applied to data
recorded with the CfA two-dimensional photon counting detector on the
CTIO 4 m telescope on March 25 and April 2 to allow measurements in
H-alpha on both nights and at 533 nm and 450 nm on the second night. The
nature of this object is as yet unknown, though it is almost certainly
a phenomenon related to the SN.
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Papaliolios, C.; Standley, C.
1987IAUC.4440....2K Altcode: 1987IAUC.4440....1K; 1987IAUC.4440....0K
M. Karovska, P. Nisensen, C. Papaliolios and C. Standley, Center for
Astrophysics, report: "Follow-up observations were carried out during
May 30-June 2 with the purpose of detecting the second bright source
(IAUC 4382) using our speckle system and the CTIO 4-m telescope. Data
were recorded in 10-nm bandpasses at H alpha and seven other optical
wavelengths in the range 400-775 nm. Conditions were fairly good (2"-3"
seeing) on two of the four nights. Careful analysis of these data
has not provided a certain detection of the second source above the
background noise. For a certain detection the magnitude difference at
the time of these observations would have to be less than about 4. SN
1987A had brightened from mv about 4.1 at the time of our original
observation (Mar. 23) to mv about 3.1 for these observations, so if
the second source remained at its originally detected brightness the
magnitude difference between it and the supernova would have been about
3.7. Data from additional observations carried out in early July using
the same telescope and equipment are still being reduced. The positions
of the second source relative to the supernova were remeasured in the
reconstructions from data taken on Mar. 23 and Apr. 2. To the limits
of accuracy of the process (0".015) there was no detectable change
in the separation. Better accuracy in centroid determination might
have been possible if the supernova were at a greater zenith angle,
where atmospheric dispersion would have less of an effect."
---------------------------------------------------------
Title: Detection of a Very Bright Close Companion Source to SN1987A
Authors: Nisenson, P.; Karovska, M.; Noyes, R.; Papaliolios, C.
1987BAAS...19..950N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supernova 1987A in the Large Magellanic Cloud
Authors: Karovska, M.; Nisenson, P.; Noyes, R.; Papaliolios, C.;
McNaught, R.; Seargent, D. A. J.
1987IAUC.4382....2K Altcode: 1987IAUC.4382....1K; 1987IAUC.4382....0K
M. Karovska, P. Nisenson, R. Noyes, and C. Papaliolios, Center for
Astrophysics, write: "High-angular-resolution speckle observations of
SN 1987A on Mar. 25 and Apr. 2 using the Cerro Tololo Interamerican
Observatory 4-m telescope (with the CfA PAPA photon- counting detector)
show a bright feature with a separation of 0".057 +/- 0".014 at
p.a. 194 deg +/- 5 deg relative to the SN. This feature appears to
be 2.7 +/- 0.2 mag fainter than the SN in a 10-nm bandpass centered
on 656.3 nm (H-alpha). A corresponding feature was detected in a
10-nm bandpass centered at 533 nm, though it appears to be somewhat
fainter than in H-alpha. Preliminary analysis of data recorded in
a 10- nm bandpass centered at 450 nm shows no evidence of an object
within a 4-mag difference from the SN. Data from nearby comparison
stars, recorded close in time using the same filters, produced clean,
point-like images with no structure above the noise at the separation
and position angle of the observed feature." Corrigendum. On IAUC
4370, lines 7-15, for mm read microns Visual magnitude estimates:
Apr. 28.51 UT, 3.0 (R. McNaught, Siding Spring Observatory); 29.38,
3.0 (D. A. J. Seargent, The Entrance, N.S.W.); 30.43, 2.9 (McNaught).
---------------------------------------------------------
Title: High Angular Resolution Speckle Imaging of α Ori
Authors: Karovska, M.; Nisenson, P.; Noyes, R.
1987BAAS...19..755K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle Imaging at CfA
Authors: Nisenson, P.; Karovaka, M.; Noyes, R.; Papaliolios, C.;
Stachnik, R.; Strom, S.; Edwards, S.
1987BAAS...19Q.748N Altcode: 1987BAAS...19..748N
No abstract at ADS
---------------------------------------------------------
Title: Magnitude Limit of the Group Delay Fringe Tracking Method
for Long Baseline Interferometry
Authors: Nisenson, P.; Traub, W.
1987iia..conf..129N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle Imaging at CFA
Authors: Nisenson, P.; Karovska, M.
1987iia..conf..229N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The CERGA Small Interferometer
Authors: Koechlin, L.; di Benedetto, G. P.; Thom, C.; Nisenson, P.
1987iia..conf..109K Altcode:
Contents: 1. Stellar diameters at λ = 0.6 μm (1985 - 86). 2. Stellar
diameters at λ = 2.2 μm and 1.6 μm. 3. γ Cassiopeiae envelope in
the Hα emission line. 4. Observations of α Cyg with the PAPA detector
at λ = 0.6 μm.
---------------------------------------------------------
Title: Resolution of the halo binary MU CAS at optical wavelengths.
Authors: Karovska, M.; Nisenson, P.; Stachnik, R. V.
1986AJ.....92..898K Altcode:
The faint secondary of the Population II binary system μ Cas has been
detected at 850 nm, using a two-dimensional photon-counting camera and
speckle-imaging techniques. The reconstructed image of the μ Cas binary
system permitted a determination of the position angle (63°±2°) and
separation (1arcsec.118±0arcsec.023) of μ Cas B, and its magnitude
difference from the primary (Δm ≈ 5 at 850 nm). Using these results
together with existing astrometric measurements the authors estimated
the masses of the components. Since errors in the mass estimates are
still dominated by errors in the astrometric data, no definitive
estimate of the helium abundance could be derived. However, using
mean values for the masses and Z = 0.005, the authors estimated Y =
0.21 for μ Cas A, which is consistent with their estimate of the
helium abundance for μ Cas B (0.20 ≤ Y ≤ 0.25).
---------------------------------------------------------
Title: On the Alpha Orionis Triple System
Authors: Karovska, M.; Nisenson, P.; Noyes, R.
1986ApJ...308..260K Altcode:
Detection of two close optical companions to the red supergiant α
Ori was accomplished in 1983 November on the Steward Observatory
2.25 m telescope. A new two-dimensional photon counting camera
was used for data recording, and speckle imaging was used for
image reconstruction. The closer of the two sources is located at
0arcsec.06±0arcsec.01 from α Ori (P.A. = 273°), the more distant at
0arcsec.51±0arcsec.01 (P.A. = 278°). An analysis of these results
and of earlier polarization data favors an interpretation in which
the two optical sources are stellar companions to α Ori.
---------------------------------------------------------
Title: High Angular Resolution Speckle Observations of Mira
Authors: Karovska, M.; Nisenson, P.; Stachnik, R. V.
1986BAAS...18..914K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High Angular Resolution Solar Imaging by Post-processing
Authors: Nisenson, P.; Stachnik, R. V.
1986BAAS...18..924N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High resolution astrophysical observations using speckle
imaging
Authors: Noyes, R. W.; Nisenson, P.; Papaliolios, C.; Stachnik, R. V.
1986sao..reptQ....N Altcode:
This report describes progress under a contract to develop a complete
astronomical speckle image reconstruction facility and to apply that
facility to the solution of astronomical problems. During the course
of the contract we have developed the procedures, algorithms, theory
and hardware required to perform that function and have made and
interpreted astronomical observations of substantial significance. A
principal result of the program was development of a photon-counting
camera of innovative design, the PAPA detector. Development of this
device was, in our view, essential to making the speckle process into
a useful astronomical tool, since the principal impediment to that
circumstance in the past was the necessity for application of photon
noise compensation procedures which were difficult if not impossible
to calibrate. The photon camera made this procedure unnecessary and
permitted precision image recovery. The result of this effort and the
associated algorithm development was an active program of astronomical
observation which included investigations into young stellar objects,
supergiant structure and measurements of the helium abundance of the
early universe. We have also continued research on recovery of high
angular resolution images of the solar surface working with scientists
at the Sacramento Peak Observatory in this area.
---------------------------------------------------------
Title: Development of a CCD based solar speckle imaging system
Authors: Nisenson, Peter; Stachnik, Robert V.; Noyes, Robert W.
1986sao..reptR....N Altcode:
A program to develop software and hardware for the purpose of obtaining
high angular resolution images of the solar surface is described. The
program included the procurement of a Charge Coupled Devices imaging
system; an extensive laboratory and remote site testing of the
camera system; the development of a software package for speckle
image reconstruction which was eventually installed and tested at
the Sacramento Peak Observatory; and experiments of the CCD system
(coupled to an image intensifier) for low light level, narrow spectral
band solar imaging.
---------------------------------------------------------
Title: Companions to α Orionis
Authors: Karovska, M.; Nisenson, P.; Noyes, R. W.; Stachnik, R.
1986LNP...254..445K Altcode: 1986csss....4..445K
Detection of two close optical companions to the red supergiant a
Ori was accomplished using the PAPA detector for data recording,
and speckle imaging for image reconstruction. Our analysis favors an
interpretation in which the two optical sources are stellar companions
to a Ori.The observed time dependent variations of the polarization of
a Ori can be interpreted as being due to a systemic asymmetry created
by one of the companions.
---------------------------------------------------------
Title: A new optical source associated with T Tauri.
Authors: Nisenson, P.; Stachnik, R. V.; Karovska, M.; Noyes, R.
1985ApJ...297L..17N Altcode:
A faint optical source close to T Tauri has been detected using speckle
imaging techniques in a photon-counting mode of operation. This second
optical source is located at position angle 358°±5° with a separation
of 0arcsec.27±0arcsec.04 from the optical astrometric position of T
Tauri. The visual magnitude difference with respect to the primary,
measured at 521 nm, is m<SUB>v</SUB> = 4.33±0.09. Since the new source
is located north of T Tauri, it is distinct from the radio/infrared
object recently reported to be located 0arcsec.61 south of T Tauri. If
the new source is a stellar object, it appears to have a mass of
between 0.2 and 0.35 M_sun; and has a surface temperature of 3000±200K.
---------------------------------------------------------
Title: Speckle Image Reconstruction of a Northern Optical Companion
to T Tau
Authors: Nisenson, P.; Karovska, M.; Stachnik, R.; Noyes, R.
1985BAAS...17..556N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On a Possible Close Companion to αOri
Authors: Karovska, M.; Noyes, R. W.; Roddier, F.; Nisenson, P.;
Stachnik, R. V.
1985BAAS...17..598K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: T Tauri
Authors: Karovska, M.; Nisenson, P.; Noyes, R.; Papaliolios, C.;
Stachnik, R.
1985IAUC.4039....2K Altcode: 1985IAUC.4039....0K
M. Karovska, P. Nisenson, R. Noyes, C. Papaliolios and R. Stachnik,
Center for Astrophysics, write: "Speckle image reconstructions
of T Tau show a second, unresolved source located ~ 0"35 from T
Tau at p.a. ~ 5 deg. The source was first detected at the Steward
Observatory's 2.3-m telescope in 1983 Nov., and it was detected again
using the 2.5-m telescope at Mt. Wilson Observatory in 1984 Nov.,
thus confirming its reality. Both sets of data were obtained through
broad-band filters centered near 660 nm (and including H=alpha), using
a two-dimensional photon-counting PAPA detector. The source appears
to be ~ 4 mag fainter than T Tau itself in this wavelength band. We
note that this appears to be a third component of the T Tau system;
it is not the object reported by infrared and radio observers as
being south of T Tau. Further optical or infrared observations of T
Tau during the remainder of this observing season would be most useful."
---------------------------------------------------------
Title: Speckle imaging with the PAPA detector
Authors: Papaliolios, Costas; Nisenson, Peter; Ebstein, Steven
1985ApOpt..24..287P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Is Mt. Wilson the Best Interferometric Site in the World?
Authors: Nisenson, P.; Noyes, R.; Shao, M.
1984BAAS...16..908N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: PM. 03 A 50-Meter Michelson Stellar Interferometer on a
Space Platform
Authors: Faucherre, M.; Lacasse, M. G.; Nisenson, P.; Reasenberg,
R. D.; Shao, M.; Stachnik, R. V.; Traub, W. A.
1984BAAS...16..793F Altcode:
The authors discuss a 50-meter Michelson stellar interferometer that
could be mounted on a space platform. For this device, the estimated
magnitude limit would be near +15 mag and, in the ultraviolet (2000
Angstroms), upper limits on angular diameters may be determined down to
about 0.2 milliarcsecond. The authors regard the development of such
a relatively simple, low-cost device as an important demonstration
of the technical and scientific potential of long baseline optical
interferometers in space.
---------------------------------------------------------
Title: Speckle with PAPA
Authors: Nisenson, P.; Papaliolios, C.; Stachnik, R.; Ebstein, S.
1984BAAS...16..496N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Finite Exposure Time, Astronomical Speckle Transfer Function
Authors: Barakat, Richard; Nisenson, Peter
1983AcOpt..30.1405B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle image reconstruction of solar features
Authors: Stachnik, R. V.; Nisenson, P.; Noyes, R. W.
1983ApJ...271L..37S Altcode:
Speckle image reconstruction procedures have been applied to 5 x 6
arcsec patches of the solar surface. Data were recorded with a CID
(charge-injection device) sensor. This detector has the wide dynamic
range and linearity required to record accurately the extremely
low contrast speckle that occurs for extended objects such as the
sun. Reconstructed images of spot penumbrae and of pores show evidence
for detail at scales as fine as 0.11 arcsec, despite prevailing seeing
conditions of 1 - 2 arcsec. The finest structures appear to be embedded
in penumbral filaments. Coarser sub-arcsecond detail appears in some,
but not all, of the pores studied. The presence of such fine, presumably
magnetically controlled detail suggests that much can be learned from
high-resolution solar surface imaging from space.
---------------------------------------------------------
Title: Solar Speckle Imaging with a CCD Camera
Authors: Nisenson, P.; Stachnik, R.; Noyes, R.; Ebstein, S.
1983BAAS...15..718N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle imaging for planetary research
Authors: Nisenson, P.; Apt, J.; Goody, R.; Papaliolios, C.
1983Icar...53..465N Altcode:
The use of speckle imaging techniques for planetary research is
discussed. Data are gathered with a video camera system. Image
reconstruction uses a division algorithm for Fourier amplitudes
and the Knox-Thompson algorithm for Fouroer phases. Bias correction
techniques for arbitrary "photon shapes" have been developed. Results
have been obtained with a laboratory optical simulator and on Io,
Titan, Pallas, Jupiter, and Uranus using the 2.24-m telescope on Mauna
Kea. All evidence indicates that spatial resolutions less than the seing
limit by a factor of about 4 can be obtained. This applies to objects
brighter than Uranus. For fainter objectsbias correction is inadequate
and images cannot be recovered. Resolutions obtained are well above the
diffraction limit. The reasons for this performance are understood in
terms of inadequacies in the video camera. A photon-counting camera
has been developed which should eliminate these problems. If so,
it should be possible to obtain diffraction-limited resolution on
objects as faint as Charon.
---------------------------------------------------------
Title: Effects of photon noise on speckle image reconstruction with
the Knox-Thompson algorithm.
Authors: Nisenson, P.; Papaliolios, C.
1983OptCo..47...91N Altcode:
An analysis of the effects of photon noise on astronomical speckle image
reconstruction using the Knox-Thompson algorithm is presented. It is
shown that the quantities resulting from the speckle average are biased,
but that the biases are easily estimated and compensated. Calculations
are also made of the convergence rate for the speckle average as a
function of the source brightness. An illustration of the effects of
photon noise on the image recovery process is included.
---------------------------------------------------------
Title: The effectiveness of astronomical speckle transfer function
reweighting algorithms.
Authors: Barakat, R.; Nisenson, P.
1983OptCo..45..311B Altcode:
Two methods for reweighting the astronomical speckle transfer
function are compared using a combination of analysis and numerical
computation. One method, long exposure subtraction, is shown to perform
well only for very short wavefront correlation lengths (shorter than
the correlation length expected from a real atmosphere). The other
method, reference star division, is demonstrated to be effective and
accurate, even when the wavefront statistics for the reference star
data are substantially changed from the object data statistics. An
experimental result using real telescope data is included which
substantiates the analysis.
---------------------------------------------------------
Title: Speckle Image Reconstruction of Solar Features
Authors: Stachnik, R. V.; Nisenson, P.; Noyes, R. W.
1982BAAS...14R.624S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radius and limb darkening of Titan from speckle imaging.
Authors: Nisenson, P.; Apt, J.; Goody, R.; Horowitz, P.
1981AJ.....86.1690N Altcode:
The radius R of Titan is determined from ground-based, visible light
observations using a two-dimensional speckle imaging technique. The
value of R is found to depend on the limb-darkening exponent alpha,
which is used in modeling the observed disk, and it is determined
that the probable range extends from R values of 2680 + or - 100 km
for alpha of 0.6 to 2900 + or - 100 km for alpha of 1.3. This range
is in agreement with Voyager 1 and Pioneer Saturn observations. It
is suggested that spatial resolution may be doubled by using a grid
of 256 x 256 pixels at the time the image is digitized, and that
further improvements are possible with speckle-reduction techniques
under development.
---------------------------------------------------------
Title: Influence of the wave-front correlation function
and deterministic wave-front aberrations on the speckle
image-reconstruction problem in the high-light-level regime
Authors: Barakat, R.; Nisenson, P.
1981JOSA...71.1390B Altcode: 1981OSAJ...71.1390B
No abstract at ADS
---------------------------------------------------------
Title: High Resolution Image Reconstruction of Binary Stars and
Other Objects
Authors: Nisenson, P.; Stachnik, R. S.
1981BAAS...13..514N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Speckle Imaging
Authors: Stachnik, R.; Nisenson, P.; Papaliolios, C.
1981siwn.conf..502S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Data recording and processing for speckle image reconstruction.
Authors: Nisenson, P.; Stachnik, R.; Papaliolios, C.; Horowitz, P.
1980SPIE..243...88N Altcode:
Image reconstruction from astronomical speckle data using the
Knox-Thompson algorithm has now been extensively demonstrated as
feasible through analysis and computer simulations. Experimental
verification of the technique and its implementation for astronomy
places stringent constraints on the recording system and requires
complex processing algorithms to handle the many experimental
details. In this paper we describe a video recording system specifically
designed for the requirements of speckle imaging. This system has been
built and tested, yielding high quality image reconstructions from
a laboratory-atmospheric simulator for a wide range of input light
levels and test objects.
---------------------------------------------------------
Title: High Resolution Imaging at Large Telescopes
Authors: Nisenson, P.; Stachnik, R.; Papaliolios, C.; Hewitt, A.
1980oits.conf..401N Altcode: 1980STIN...8029217N
Image recovery at a resolution limited only by diffraction is
now possible at large telescopes. The theory of speckle image
reconstruction is explained and the current status of a video
recording and digitization system for the reconstruction procedure is
described. Potential applications of the process when used with very
large telescopes are discussed. The constraints on telescope design
imposed by these techniques are listed.
---------------------------------------------------------
Title: Image Reconstruction of Binary Stars and Solar Features
Authors: Stachnik, R.; Nisenson, P.; Papaliolios, C.
1979BAAS...11..686S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle Image Reconstruction at Low Light Levels
Authors: Nisenson, P.; Stachnik, R.; Papaliolios, C.
1979BAAS...11..668N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Restoration of turbulence degraded images - A review
Authors: Nisenson, P.; Stachnik, R. V.
1979hars.proc...34N Altcode: 1979IAUCo..50...34N
The paper surveys techniques for recovering high resolution information
from atmospheric turbulence degraded images. Several approaches to image
restoration are covered, noting that the effectiveness of each technique
is strongly dependent on the brightness and the angular extent of the
object being observed. These approaches include: speckle holography and
betelgence imaging, nonredundant aperture imaging, phase retrieval,
and speckle imaging. In addition, the applications and the expected
performance range of the various techniques are discussed.
---------------------------------------------------------
Title: Speckle Image Reconstruction of Astronomical Objects
Authors: Nisenson, P.; Stachnik, R. V.
1978BAAS...10..661N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Speckle Image Reconstruction of Outer Planet Satellites.
Authors: Nisenson, P.; Stachnik, R. V.
1978BAAS...10..459N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Measurements of atmospheric isoplanatism using speckle
interferometry.
Authors: Nisenson, P.; Stachnik, R. V.
1978JOSA...68..169N Altcode: 1978OSAJ...68..169N
Measurements of isoplanatism for speckle interferometry and speckle
imaging applications have been made at a 1.57 meter aperture telescope
in Hawaii. The measurements were obtained from optically produced
spatial power spectra of short-exposure images showing pairs of stars
with different angular separations. The result of this process is a
sequence of plots of correlation versus spatial frequency in the image
for 0.25, 0.5, 1.9, and 4.7 arcsec separation binary stars. Substantial
correlation is found to be at least 0.6 of the diffraction limit cutoff
for the 4.7 arcsec pair.
---------------------------------------------------------
Title: Speckle image reconstruction of solar features
Authors: Stachnik, R. V.; Nisenson, P.; Ehn, D. C.; Hudgin, R. H.;
Schirf, V. E.
1977Natur.266..149S Altcode:
SPECKLE imaging is a process which permits recovery of diffraction
limited resolution from atmospherically degraded astronomical images. We
describe here the application of this new process to the reconstruction
of solar surface features with resolution approaching the telescope
limit, despite severe atmospheric blurring in the original data.
---------------------------------------------------------
Title: Measurements of atmospheric isoplanatism using speckle
interferometry.
Authors: Nisenson, P.; Stachnik, R. V.
1977JOSA...67.1391N Altcode: 1977OSAJ...67.1391N
No abstract at ADS
---------------------------------------------------------
Title: Measurements of the isoplanatic angle using speckle
interferometry.
Authors: Nisenson, P.; Stachnik, R. V.
1976JOSA...66.1077N Altcode: 1976OSAJ...66.1077N
No abstract at ADS
---------------------------------------------------------
Title: Astronomical speckle imaging.
Authors: Nisenson, P.; Ehn, D. C.; Stachnik, R. V.
1976SPIE...75...83N Altcode: 1976imat.conf...83N
Speckle imaging is a technique for recovering diffraction limited images
from sequences of atmosphere-degraded, short exposure photographs
obtained at a large telescope. The technique is derived from speckle
interferometry and shares many of the characteristics of that process,
including dependence of the output signal-to-noise on number of frames
processed and relative insensitivity to fixed telescope aberrations and
noise in the image record. Speckle interferometry has been demonstrated
to yield telescope-diffraction-limited information, but only in the
form of spatial power spectra. Speckle imaging averages a different
quantity, the statistical autocorrelation of the image Fourier
transform, which contains all the information in the averaged power
spectra plus the transform phase information required to recover an
image. Two-dimensional digital simulations of the process for extended
continuous-tone objects are presented, and include the case where
severe static telescope aberrations are present.
---------------------------------------------------------
Title: Astronomical speckle imaging.
Authors: Ehn, D. C.; Nisenson, P.
1975JOSA...65.1196E Altcode: 1975OSAJ...65.1196E
No abstract at ADS
---------------------------------------------------------
Title: The PROM Optical Speckle Interferometer.
Authors: Nisenson, P.; Stachnik, R. V.
1974BAAS....6..459N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Mirror blank testing by real-time holographic interferometry.
Authors: van Deelen, W.; Nisenson, P.
1969ApOpt...8..951V Altcode:
No abstract at ADS
