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An Adaptive Optics Survey of Stellar Variability at the Galactic Center

Gautam, Abhimat Krishna and Do, Tuan and Ghez, Andrea M. and Morris, Mark R. and Martinez, Gregory D. and Hosek, Matthew W., Jr. and Lu, Jessica R. and Sakai, Shoko and Witzel, Gunther and Jia, Siyao and Becklin, Eric E. and Matthews, Keith (2019) An Adaptive Optics Survey of Stellar Variability at the Galactic Center. Astrophysical Journal, 871 (1). Art. No. 103. ISSN 1538-4357. doi:10.3847/1538-4357/aaf103.

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We present an ≈11.5 yr adaptive optics (AO) study of stellar variability and search for eclipsing binaries in the central ~0.4 pc (~10'') of the Milky Way nuclear star cluster. We measure the photometry of 563 stars using the Keck II NIRC2 imager (K'-band, λ_0 = 2.124 μm). We achieve a photometric uncertainty floor of Δm_K' ~ 0.03 (≈3%), comparable to the highest precision achieved in other AO studies. Approximately half of our sample (50% ± 2%) shows variability: 52% ± 5% of known early-type young stars and 43% ± 4% of known late-type giants are variable. These variability fractions are higher than those of other young, massive star populations or late-type giants in globular clusters, and can be largely explained by two factors. First, our experiment time baseline is sensitive to long-term intrinsic stellar variability. Second, the proper motion of stars behind spatial inhomogeneities in the foreground extinction screen can lead to variability. We recover the two known Galactic center eclipsing binary systems: IRS 16SW and S4-258 (E60). We constrain the Galactic center eclipsing binary fraction of known early-type stars to be at least 2.4% ± 1.7%. We find no evidence of an eclipsing binary among the young S-stars nor among the young stellar disk members. These results are consistent with the local OB eclipsing binary fraction. We identify a new periodic variable, S2-36, with a 39.43 days period. Further observations are necessary to determine the nature of this source.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Gautam, Abhimat Krishna0000-0002-2836-117X
Do, Tuan0000-0001-9554-6062
Ghez, Andrea M.0000-0003-3230-5055
Morris, Mark R.0000-0002-6753-2066
Martinez, Gregory D.0000-0002-7476-2521
Hosek, Matthew W., Jr.0000-0003-2874-1196
Lu, Jessica R.0000-0001-9611-0009
Sakai, Shoko0000-0001-5972-663X
Witzel, Gunther0000-0003-2618-797X
Jia, Siyao0000-0001-5341-0765
Additional Information:© 2019 The American Astronomical Society. Received 2018 September 18; revised 2018 November 6; accepted 2018 November 12; published 2019 January 24. We thank the anonymous referee for helpful comments. We thank the staff of the Keck Observatory for their help in obtaining the observations presented herein. Support for this work at UCLA was provided by the Kaplan Family Student Support Fund and the W. M. Keck Foundation. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck:II (NIRC2). - Software: NumPy (van der Walt et al. 2011), Astropy (Astropy Collaboration et al. 2013), emcee (Foreman-Mackey et al. 2013), SciPy (Jones et al. 2001), Matplotlib (Hunter 2007).
Funding AgencyGrant Number
Kaplan Family Student Support FundUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: eclipsing – Galaxy: center – stars: variables: general – techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20190214-072935747
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Official Citation:Abhimat Krishna Gautam et al 2019 ApJ 871 103
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92912
Deposited By: Tony Diaz
Deposited On:14 Feb 2019 17:31
Last Modified:16 Nov 2021 16:54

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