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J. Woillez,
R. Akeson,
M. Colavita,
J. Eisner,
A. Ghez,
J. Graham,
L. Hillenbrand,
R. Millan-Gabet,
J. Monnier,
J. -U. Pott, [......],
M. Hrynevych,
O. Martin,
D. Medeiros,
D. Morrison,
T. Panteleeva,
B Smith,
K. Summers,
K. Tsubota,
C. Tyau,
E. Wetherell
[show abstract]
[hide abstract]
ABSTRACT: ASTRA (ASTrometric and phase-Referencing Astronomy) is an upgrade to the existing Keck Interferometer which aims at providing new self-phase referencing (high spectral resolution observation of YSOs), dual-field phase referencing (sensitive AGN observations), and astrometric (known exoplanetary systems characterization and galactic center general relativity in strong field regime) capabilities. With the first high spectral resolution mode now offered to the community, this contribution focuses on the progress of the dual field and astrometric modes.
Danchi, William C.; Delplancke, Françoise; Rajagopal, Jayadev K.: Optical and Infrared Interferometry II, SPIE, 773412-773412-10 (2010). 08/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We present simulations of Keck Interferometer ASTRA and VLTI GRAVITY
observations of mock star fields in orbit within ~50 milliarcseconds of Sgr A*.
Dual-field phase referencing techniques, as implemented on ASTRA and planned
for GRAVITY, will provide the sensitivity to observe Sgr A* with infrared
interferometers. Our results show an improvement in the confusion noise limit
over current astrometric surveys, opening a window to study stellar sources in
the region. Since the Keck Interferometer has only a single baseline, the
improvement in the confusion limit depends on source position angles. The
GRAVITY instrument will yield a more compact and symmetric PSF, providing an
improvement in confusion noise which will not depend as strongly on position
angle. Our Keck results show the ability to characterize the star field as
containing zero, few, or many bright stellar sources. We are also able to
detect and track a source down to mK~18 through the least confused regions of
our field of view at a precision of ~200 microarcseconds along the baseline
direction. This level of precision improves with source brightness. Our GRAVITY
results show the potential to detect and track multiple sources in the field.
GRAVITY will perform ~10 microarcsecond astrometry on a mK=16.3 source and ~200
microarcsecond astrometry on a mK=18.8 source in six hours of monitoring a
crowded field. Monitoring the orbits of several stars will provide the ability
to distinguish between multiple post-Newtonian orbital effects, including those
due to an extended mass distribution around Sgr A* and to low-order General
Relativistic effects. Early characterizations of the field by ASTRA including
the possibility of a precise source detection, could provide valuable
information for future GRAVITY implementation and observation.
06/2012;
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J. A. Eisner,
R. Akeson,
M. Colavita,
A. Ghez,
J. Graham,
L. Hillenbrand,
R. Millan-Gabet,
J. D. Monnier,
J. -U. Pott,
S. Ragland, P. Wizinowich,
J. Woillez
[show abstract]
[hide abstract]
ABSTRACT: The ASTrometric and phase-Referenced Astronomy (ASTRA) project will provide phase referencing and astrometric observations at the Keck Interferometer, leading to enhanced sensitivity and the ability to monitor orbits at an accuracy level of 30-100 microarcseconds. Here we discuss recent scientific results from ASTRA, and describe new scientific programs that will begin in 2010-2011. We begin with results from the "self phase referencing" (SPR) mode of ASTRA, which uses continuum light to correct atmospheric phase variations and produce a phase-stabilized channel for spectroscopy. We have observed a number of protoplanetary disks using SPR and a grism providing a spectral dispersion of ~2000. In our data we spatially resolve emission from dust as well as gas. Hydrogen line emission is spectrally resolved, allowing differential phase measurements across the emission line that constrain the relative centroids of different velocity components at the 10 microarcsecond level. In the upcoming year, we will begin dual-field phase referencing (DFPR) measurements of the Galactic Center and a number of exoplanet systems. These observations will, in part, serve as precursors to astrometric monitoring of stellar orbits in the Galactic Center and stellar wobbles of exoplanet host stars. We describe the design of several scientific investigations capitalizing on the upcoming phase-referencing and astrometric capabilities of ASTRA. Comment: Published in the proceedings of the SPIE 2010 conference on "Optical and Infrared Interferometry II"
08/2010;
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S. Ragland,
R. Akeson,
M. Colavita,
R. Millan-Gabet,
J. Woillez, P. Wizinowich,
E. Appleby,
B. Berkey,
A. Cooper,
C. Felizardo, [......],
M. Hrynevych,
D. Medeiros,
D. Morrison,
T. Panteleeva,
J.-U. Pott,
B. Smith,
K. Summers,
K. Tsubota,
C. Tyau,
E. Wetherell
[show abstract]
[hide abstract]
ABSTRACT: The Keck Interferometer (KI) combines the two 10m diameter Keck telescopes providing milliarcsecond angular resolution. KI has unique observing capabilities such as sensitive K-band V2, L-band V2 and N-band nulling operations. The instrument status of the Keck Interferometer since the last SPIE meeting in 2008 is summarized. We discuss the performance of new visibility observing capabilities including L-band and self-phase referencing modes. A simultaneous dual-beam-combiner mode in the K and L-band has been demonstrated, nearly doubling operational efficiency for bright targets. Operational improvements including simplified reliable operations with reduced personnel resources are highlighted. We conclude with a brief review of the current and future developmental activities of KI. Details of ASTRA developments, nulling performance and science results are presented elsewhere at this conference.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
07/2010;
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J. Woillez,
R. Akeson,
M. Colavita,
J. Eisner,
A. Ghez,
J. Graham,
L. Hillenbrand,
R. Millan-Gabet,
J. Monnier,
J-U. Pott, [......],
M. Hrynevych,
O. Martin,
D. Medeiros,
D. Morrison,
T. Panteleeva,
B. Smith,
K. Summers,
K. Tsubota,
C. Tyau,
E. Wetherell
[show abstract]
[hide abstract]
ABSTRACT: ASTRA (ASTrometric and phase-Referencing Astronomy) is an upgrade to the existing Keck Interferometer which aims at providing new self-phase referencing (high spectral resolution observation of YSOs), dual-field phase referencing (sensitive AGN observations), and astrometric (known exoplanetary systems characterization and galactic center general relativity in strong field regime) capabilities. With the first high spectral resolution mode now offered to the community, this contribution focuses on the progress of the dual field and astrometric modes.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
07/2010;
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[show abstract]
[hide abstract]
ABSTRACT: We present near-infrared observations of T Tauri and Herbig Ae/Be stars with a spatial resolution of a few milli-arcseconds and a spectral resolution of ~2000. Our observations spatially resolve gas and dust in the inner regions of protoplanetary disks, and spectrally resolve broad-linewidth emission from the Brackett gamma transition of hydrogen gas. We use the technique of spectro-astrometry to determine centroids of different velocity components of this gaseous emission at a precision orders of magnitude better than the angular resolution. In all sources, we find the gaseous emission to be more compact than or distributed on similar spatial scales to the dust emission. We attempt to fit the data with models including both dust and Brackett gamma-emitting gas, and we consider both disk and infall/outflow morphologies for the gaseous matter. In most cases where we can distinguish between these two models, the data show a preference for infall/outflow models. In all cases, our data appear consistent with the presence of some gas at stellocentric radii of ~0.01 AU. Our findings support the hypothesis that Brackett gamma emission generally traces magnetospherically driven accretion and/or outflows in young star/disk systems. Comment: 48 pages, including 17 figures. Accepted for publication by ApJ
06/2010;
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Sam Ragland,
R. Akeson,
T. Armandroff,
M. Colavita,
W. Cotton,
W. Danchi,
L. Hillenbrand,
R. Millan-Gabet,
S. T. Ridgway,
W. Traub, P. Wizinowich
Bulletin of the American Astronomical Society; 01/2010
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J. Patience,
R. J. White,
A. M. Ghez,
C. McCabe,
I. S. McLean,
J. E. Larkin,
L. Prato,
Sungsoo S. Kim,
J. P. Lloyd,
M. C. Liu,
J. R. Graham,
B. A. Macintosh,
D. T. Gavel,
C. E. Max,
B. J. Bauman,
S. S. Olivier, P. Wizinowich,
and D. S. Acton
[show abstract]
[hide abstract]
ABSTRACT: A combination of high-resolution and wide-field imaging reveals two binary stars and one triple star system among the sample of the first 11 stars with planets detected by radial velocity variations. High-resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to the diffraction limit of the Keck 10 m or the Lick 3 m, and direct images or AO images are sensitive to a wider field, extending to 10'' or 38'', depending on the camera. One of the binary system—HD 114762—was not previously known to be a spatially resolved multiple system; additional data taken with the combination of Keck adaptive optics and NIRSPEC are used to characterize the new companion. The second binary system—τ Boo—was a known multiple with two conflicting orbital solutions; the current data will help constrain the discrepant estimates of periastron time and separation. Another target—16 Cyg B—was a known common proper motion binary, but the current data resolve a new third component, close to the wide companion 16 Cyg A. Both the HD 114762 and 16 Cyg B systems harbor planets in eccentric orbits, while the τ Boo binary contains an extremely close planet in a tidally circularized orbit. Although the sample is currently small, the proportion of binary systems is comparable to that measured in the field over a similar separation range. Incorporating the null result from another companion search project lowers the overall fraction of planets in binary systems, but the detections in our survey reveal that planets can form in binaries separated by less than 50 AU.
The Astrophysical Journal 12/2008; 581(1):654. · 6.02 Impact Factor
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M. Colavita,
R. Akeson, P. Wizinowich,
M. Shao,
S. Acton,
J. Beletic,
J. Bell,
J. Berlin,
A. Boden,
A. Booth, [......],
P. Swanson,
R. Thompson,
K. Tsubota,
A. Tumminello,
G. van Belle,
G. Vasisht,
J. Vause,
J. Walker,
K. Wallace,
and U. Wehmeier
[show abstract]
[hide abstract]
ABSTRACT: We present the first science results from the Keck Interferometer, a direct-detection infrared interferometer utilizing the two 10 m Keck telescopes. The instrument and system components are briefly described. We then present observations of the T Tauri object DG Tau, which is resolved by the interferometer. The resolved component has a radius of 0.12-0.24 AU, depending on the assumed stellar and extended component fluxes and the model geometry used. Possible origins and implications of the resolved emission are discussed.
The Astrophysical Journal 12/2008; 592(2):L83. · 6.02 Impact Factor
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B. Mennesson,
C. Koresko,
M. J. Creech-Eakman,
E. Serabyn,
M. M. Colavita,
R. Akeson,
E. Appleby,
J. Bell,
A. Booth,
S. Crawford, [......],
T. Saloga,
M. Shao,
R. Smythe,
K. Summers,
M. Swain,
K. Tsubota,
C. Tyau,
G. Vasisht, P. Wizinowich,
and J. Woillez
[show abstract]
[hide abstract]
ABSTRACT: We report interferometric observations of the semiregular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long-baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner. The light was dispersed by a low-resolution spectrometer, allowing simultaneous measurement of the source visibility and intensity spectra from 8 to 12 μm. The interferometric observations allow a nonambiguous determination of the dust shell spatial scale and relative flux contribution. Using a simple spherically symmetric model, in which a geometrically thin shell surrounds the stellar photosphere, we find that ~30% to ~70% of the overall mid-infrared flux—depending on the wavelength—originates from 7-8 stellar radii. The derived shell opacity profile shows a broad peak around 11 μm (τ 0.06), characteristic of Mg-rich silicate dust particles.
The Astrophysical Journal 12/2008; 634(2):L169. · 6.02 Impact Factor
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R. K. Barry,
W. C. Danchi,
W. A. Traub,
J. L. Sokoloski,
J. P. Wisniewski,
E. Serabyn,
M. J. Kuchner,
R. Akeson,
E. Appleby,
J. Bell, [......],
M. Shao,
R. Smythe,
K. Summers,
M. Swain,
K. Tsubota,
C. Tyau,
E. Wetherell, P. Wizinowich,
J. Woillez,
and G. Vasisht
[show abstract]
[hide abstract]
ABSTRACT: We report observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nuller (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N band from 8 to 12.5 μm in a nulling mode. The nulling technique is the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture telescopes. In this mode the stellar light itself is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. By fitting the unique KIN data, we have obtained an angular size of the mid-infrared continuum emitting material of 6.2, 4.0, or 5.4 mas for a disk profile, Gaussian profile (FWHM), and shell profile, respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at ~17 AU from the WD, that are not found in the inner regime. Our evidence suggests that these features have been excited by the nova flash in the outer spatial regime before the blast wave reached these regions. These identifications support a model in which the dust appears to be present between outbursts and is not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star.
The Astrophysical Journal 12/2008; 677(2):1253. · 6.02 Impact Factor
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P. Wizinowich,
R. Dekany,
D. Gavel,
C. Max,
S. Adkins,
B. Bauman,
J. Bell,
A. Bouchez,
M. Britton,
J. Chin, [......],
E. Johansson,
R. Kupke,
D. Le Mignant,
C. Lockwood,
D. Medeiros,
E. McGrath,
A. Moore,
C. Neyman,
M. Reinig,
V. Velur
[show abstract]
[hide abstract]
ABSTRACT: W. M. Keck Observatory (WMKO) is currently engaged in the design of a powerful new Adaptive Optics (AO) science capability providing precision correction in the near-IR, good correction in the visible, and faint object multiplexed integral field spectroscopy. Improved sensitivity will result from significantly higher Strehl ratios over narrow fields (< 30" diameter) and from lower backgrounds. Quantitative astronomy will benefit from improved PSF stability and knowledge. Strehl ratios of 15 to 25% are expected at wavelengths as short as 750 nm. A multi-object AO approach will be taken for the correction of multiple science targets over modest fields of regard (< 2' diameter) and to achieve high sky coverage using AO compensated near-IR tip/tilt sensing. In this paper we present the conceptual design for this system including discussion of the requirements, system architecture, key design features, performance predictions and implementation plans.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
07/2008;
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[show abstract]
[hide abstract]
ABSTRACT: The Keck Interferometer (KI) combines the two 10m Keck telescopes with a
baseline separation of 85m, and is one of the two large aperture optical
long baseline interferometric (OLBI) facilities in the world. The KI is
funded by the National Aeronautics and Space Administration (NASA). The
10m telescope diameters provide a unique sensitivity advantage and has
lead to several 'first OLBI' science in the IR such as visibility
measurements of an AGN. The visibility (V2) and Nuller modes, are in
operation and offered to the Keck community. Now a new major development
effort is underway to broaden the astrophysical applications of this
unique instrument: the ASTRA upgrade.
ASTRA stands for the ASTrometric and phase-Referenced Astronomy upgrade
of the KI project. ASTRA has been funded by the NSF-Major Research
Instrumentation program and will be implemented in three steps over the
next 3 years. Besides the NSF engagement a number of science institutes
contribute to the ASTRA collaboration to advance and profit from
large-aperture OLBI.
This contribution will present the three modes of ASTRA each of which
will overcome current sensitivity limitations by continuous correction
for phase distortions induced by the turbulent atmosphere: (i)
self-referenced spectroscopy stabilizes fringes on-axis and enable
higher spectral resolution up to a few thousands (ii) dual-field
visibility measurements stand for integration beyond the atmospheric
coherence time to reach K=15mag on science targets while locking the
fringe tracker on an offset guide star (iii) the narrow-angle astrometry
mode eventually will measure distances between a pair of stars within
the iso-planatic patch to an accuracy of less than 100 uas.
02/2008; 211.
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D. Le Mignant,
R. Sahai,
A. Bouchez,
R Campbell,
M. Van Dam,
J. Chin,
E. Johansson,
S. Hartman,
R. Lafon,
J. Lyke,
P. Stomski,
D. Summers, P. Wizinowich
[show abstract]
[hide abstract]
ABSTRACT: The Egg Nebula has been regarded as the archetype of bipolar proto-planetary nebulae, yet we lack a coherent model that can explain the morphology and kinematics of the nebular and dusty components observed at high-spatial and spectral resolution. Here, we report on two sets of observations obtained with the Keck Adaptive Optics Laser Guide Star: H to M-band NIRC2 imaging, and narrow bandpath K-band OSIRIS 3-D imaging-spectroscopy (through the H2 2.121micron emission line). While the central star or engine remains un-detected at all bands, we clearly resolve the dusty components in the central region and confirm that peak A is not a companion star. The spatially-resolved spectral analysis provide kinematic information of the H_2 emission regions in the eastern and central parts of the nebula and show projected velocities for the H_2 emission higher than 100 km/s. We discuss these observations against a possible formation scenario for the nebular components.
10/2007;
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E. Serabyn,
A. Booth,
M. M. Colavita,
S. Crawford,
J. Garcia,
J. Gathright,
M. Hrynevych,
C. Koresko,
R. Ligon,
B. Mennesson,
T. Panteleeva,
S. Ragland,
K. Summers,
W. Traub,
K. Tsubota,
E. Wetherell, P. Wizinowich,
J. Woillez
[show abstract]
[hide abstract]
ABSTRACT: The Keck Interferometer Nuller (KIN) is now largely in place at the Keck Observatory, and functionalities and performance are increasing with time. The main goal of the KIN is to examine nearby stars for the presence of exozodiacal emission, but other sources of circumstellar emission, such as disks around young stars, and hot exoplanets are also potential targets. To observe with the KIN in nulling mode, knowledge of the intrinsic source spectrum is essential, because of the wide variety of wavelengths involved in the various control loops - the AO system operates at visible wavelengths, the pointing loops use the J-band, the high-speed fringe tracker operates in the K-band, and the nulling observations take place in the N-band. Thus, brightness constraints apply at all of these wavelengths. In addition, source structure plays a role at both K-band and N-band, through the visibility. In this talk, the operation of the KIN is first briefly described, and then the sensitivity and performance of the KIN is summarized, with the aim of presenting an overview of the parameter space accessible to the nuller. Finally, some of the initial observations obtained with the KIN are described.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
06/2006;
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B. Mennesson ,
R. Akeson ,
E. Appleby ,
J. Bell ,
A. Booth ,
M.M. Colavita ,
S. Crawford ,
M.J. Creech-Eakman ,
W. Dahl ,
J. Fanson , [......],
E. Serabyn ,
M. Shao ,
R. Smythe ,
K. Summers ,
M. Swain ,
K. Tsubota ,
C. Tyau ,
G. Vasisht , P. Wizinowich ,
J. Woillez
[show abstract]
[hide abstract]
ABSTRACT: The Keck Interferometer Nuller (KIN) is one of the major scientific and technical precursors to the Terrestrial Planet Finder Interferometer (TPF-I) mission. KIN's primary objective is to measure the level of exo-zodiacal mid-infrared emission around nearby main sequence stars, which requires deep broad-band nulling of astronomical sources of a few Janskys at 10 microns. A number of new capabilitites are needed in order to reach that goal with the Keck telescopes: mid-infrared coherent recombination, interferometric operation in “split pupil” mode, N-band optical path stabilization using K-band fringe tracking and internal metrology, and eventually, active atmospheric dispersion correction. We report here on the progress made implementing these new functionalities, and discuss the initial levels of extinction achieved on the sky.
Proceedings of the International Astronomical Union 09/2005; 1:227 - 232.
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A. M. Ghez,
S. D. Hornstein,
J Lu,
A. Bouchez,
D. Le Mignant,
M. A. van Dam, P. Wizinowich,
K. Matthews,
M Morris,
E. E. Becklin,
R. D. Campbell,
J. C. Y. Chin,
S. K. Hartman,
E. M. Johansson,
R. E. Lafon,
P. J. Stomski,
D. M. Summers
[show abstract]
[hide abstract]
ABSTRACT: (Abridged) We present the first Laser Guide Star Adaptive Optics (LGS-AO) observations of the Galactic center. LGS-AO has dramatically improved the quality, robustness, and versatility with which high angular resolution infrared images of the Galactic center can be obtained with the W. M. Keck II 10-meter telescope. Specifically, Strehl ratios of 0.7 and 0.3 at L'[3.8 micron] and K'[2.1 micron], respectively, are achieved in these LGS-AO images. During our observations, the infrared counterpart to the central supermassive black hole, Sgr A*-IR, showed significant infrared intensity variations, with observed L' magnitudes ranging from 12.6 to 14.5 mag. The faintest end of our L' detections, 1.3 mJy (dereddened), is the lowest level of emission yet observed for this source by a factor of 3. No significant variation in the location of SgrA*-IR is detected as a function of either wavelength or intensity. Near a peak in its intensity, we obtained the first measurement of SgrA*-IR's K'-L' color (3.0 +- 0.2 mag, observed), which corresponds to an intrinsic spectral index of -0.5 +- 0.3. This is significantly bluer than other recent infrared measurements. Because our measurement was taken at a time when Sgr A* was ~6 times brighter in the infrared than the other measurements, we posit that the spectral index of the emission arising from the vicinity of our Galaxy's central black hole may depend on the strength of the flare, with stronger flares giving rise to a higher fraction of high energy electrons in the emitting region.
09/2005;
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J. D. Monnier,
R. Millan-Gabet,
R. Billmeier,
R. Akeson,
D. Wallace,
J. -P. Berger,
N. Calvet,
P. D'Alessio,
W. Danchi,
L. Hartmann, [......],
R. Thompson,
G. Vasisht, P. Wizinowich,
C. Beichman,
J. Beletic,
M. Creech-Eakman,
C. Koresko,
A. Sargent,
M. Shao,
G. van Belle
[show abstract]
[hide abstract]
ABSTRACT: We report the results of a sensitive K-band survey of Herbig Ae/Be disk sizes using the 85-m baseline Keck Interferometer. Targets were chosen to span the maximum range of stellar properties to probe the disk size dependence on luminosity and effective temperature. For most targets, the measured near-infrared sizes (ranging from 0.2 to 4 AU) support a simple disk model possessing a central optically-thin (dust-free) cavity, ringed by hot dust emitting at the expected sublimation temperatures (T_sub~1000-1500K). Furthermore, we find a tight correlation of disk size with source luminosity R propto L^(1/2) for Ae and late Be systems (valid over more than 2 decades in luminosity), confirming earlier suggestions based on lower-quality data. Interestingly, the inferred dust-free inner cavities of the highest luminosity sources (Herbig B0-B3 stars) are under-sized compared to predictions of the optically-thin cavity model, likely due to optically-thick gas within the inner AU. Comment: Accepted by Astrophysical Journal; 24 pages, 4 figures, 4 tables
The Astrophysical Journal 02/2005; · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present the first Laser Guide Star Adaptive Optics (LGS-AO)
observations of the Galactic Center. LGS-AO has dramatically improved
the quality and robustness with which high angular resolution images of
the Galactic Center can be obtained with the W. M. Keck II 10-meter
telescope. Specifically, the Strehl ratios are at least a factor of two
higher (0.76 at 3.8 microns) and significantly more stable against
atmospheric fluctuations compared the performance of the Keck Natural
Guide Star AO system on the Galactic Center. Furthermore, these
observations are the first that can cover a large area surrounding the
central black hole at diffraction-limited resolution for an 8-10 meter
class telescope. These K'(2.2 microns) and L'(3.8 microns) images reveal
newly identified extended emission in the vicinity of the central black
hole. The extent of this emission is roughly 900 AU, peaks 700 AU from
the central black hole, and is the reddest emission in the central 1" x
1". In addition, emission coincident with the central black hole is
observed to fade by a factor of two within 8 minutes. Over the larger
field of view (80" x 80"), narrow band images present a more complete
picture of the young star population. These observations represent an
exciting next step in our understanding of the central black hole and
its surrounding as well as our technical ability to obtain high angular
resolution data.
11/2004; 36:1384.
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[show abstract]
[hide abstract]
ABSTRACT: We present the first science results from the Keck Interferometer, a direct-detection infrared interferometer utilizing the two 10-meter Keck telescopes. The instrument and system components are briefly described. We then present observations of the T Tauri object DG Tau, which is resolved by the interferometer. The resolved component has a radius of 0.12 to 0.24 AU, depending on the assumed stellar and extended component fluxes and the model geometry used. Possible origins and implications of the resolved emission are discussed. Comment: 10 pages, 2 figures, to appear in ApJ Letters
07/2003;
