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Detection of Galactic Center Source G2 at 3.8 μm during Periapse Passage

Witzel, G. and Ghez, A. M. and Morris, M. R. and Sitarski, B. N. and Boehle, A. and Naoz, S. and Campbell, R. and Becklin, E. E. and Canalizo, G. and Chappell, S. and Do, T. and Lu, J. R. and Matthews, K. and Meyer, L. and Stockton, A. and Wizinowich, P. and Yelda, S. (2014) Detection of Galactic Center Source G2 at 3.8 μm during Periapse Passage. Astrophysical Journal Letters, 796 (1). Art. No. L8. ISSN 2041-8205. doi:10.1088/2041-8205/796/1/L8.

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We report new observations of the Galactic Center source G2 from the W. M. Keck Observatory. G2 is a dusty red object associated with gas that shows tidal interactions as it nears its closest approach with the Galaxy's central black hole. Our observations, conducted as G2 passed through periapse, were designed to test the proposal that G2 is a 3 Earth mass gas cloud. Such a cloud should be tidally disrupted during periapse passage. The data were obtained using the Keck II laser guide star adaptive optics system (LGSAO) and the facility near-infrared camera (NIRC2) through the K' [2.1 μm] and L' [3.8 μm] broadband filters. Several results emerge from these observations: (1) G2 has survived its closest approach to the black hole as a compact, unresolved source at L', (2) G2's L' brightness measurements are consistent with those over the last decade, (3) G2's motion continues to be consistent with a Keplerian model. These results rule out G2 as a pure gas cloud and imply that G2 has a central star. This star has a luminosity of ~30 L_☉ and is surrounded by a large (~2.6 AU) optically thick dust shell. The differences between the L' and Br-γ observations can be understood with a model in which L' and Br-γ emission arises primarily from internal and external heating, respectively. We suggest that G2 is a binary star merger product and will ultimately appear similar to the B-stars that are tightly clustered around the black hole (the so-called S-star cluster).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Witzel, G.0000-0003-2618-797X
Ghez, A. M.0000-0003-3230-5055
Morris, M. R.0000-0002-6753-2066
Boehle, A.0000-0003-0439-7634
Naoz, S.0000-0002-9802-9279
Campbell, R.0000-0002-3289-5203
Canalizo, G.0000-0003-4693-6157
Do, T.0000-0001-9554-6062
Lu, J. R.0000-0001-9611-0009
Wizinowich, P.0000-0002-1646-442X
Yelda, S.0000-0001-5036-4329
Additional Information:© 2014 American Astronomical Society. Received 2014 October 7; accepted 2014 October 14; published 2014 November 3. We wish to dedicate this paper to Gerry Neugebauer (1932–2014). We thank the anonymous referee and the generous financial support from the NSF (AST-0909218 and AST-1412615), the Galactic Center Board of Advisors, the Lauren Leichtman & Arthur Levine Chair in Astrophysics, the Preston Family Graduate Student Fellowship, and the Janet Marott Student Travel Awards. The W. M. Keck Observatory is operated as a scientific partnership among Caltech, the University of California, and NASA. The Observatory was made possible by through a gift from the W. M. Keck Foundation.
Funding AgencyGrant Number
Galactic Center Board of AdvisorsUNSPECIFIED
Lauren Leichtman and Arthur Levine Chair in AstrophysicsUNSPECIFIED
Preston Family Graduate Student FellowshipUNSPECIFIED
Janet Marott Student Travel AwardsUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:black hole physics; Galaxy: center; Galaxy: nucleus; infrared: stars; techniques: high angular resolution; techniques: photometric
Issue or Number:1
Record Number:CaltechAUTHORS:20141215-090620639
Persistent URL:
Official Citation:Detection of Galactic Center Source G2 at 3.8 μm during Periapse Passage G. Witzel et al. 2014 ApJ 796 L8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52800
Deposited By: Ruth Sustaita
Deposited On:15 Dec 2014 17:31
Last Modified:10 Nov 2021 19:43

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