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The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole

Witzel, G. and Sitarski, B. N. and Ghez, A. M. and Morris, M. R. and Hees, A. and Do, T. and Lu, J. R. and Naoz, S. and Boehle, A. and Martinez, G. and Chappell, S. and Schödel, R. and Meyer, L. and Yelda, S. and Becklin, E. E. and Matthews, K. (2017) The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole. Astrophysical Journal, 847 (1). Art. No. 80. ISSN 1538-4357.

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We present new adaptive optics (AO) imaging and spectroscopic measurements of Galactic center source G1 from W. M. Keck Observatory. Our goal is to understand its nature and relationship to G2, which is the first example of a spatially resolved object interacting with a supermassive black hole (SMBH). Both objects have been monitored with AO for the past decade (2003–2014) and are comparatively close to the black hole (ɑ_(min) ~ 200–300 au) on very eccentric orbits (ℯ_(G1) ~ 0.99; ℯ_(G2) ~ 0.96). While G2 has been tracked before and during periapsis passage (T_0 ~ 2014.2), G1 has been followed since soon after emerging from periapsis (T_0 ~ 2001.3). Our observations of G1 double the previously reported observational time baseline, which improves its orbital parameter determinations. G1's orbital trajectory appears to be in the same plane as that of G2 but with a significantly different argument of periapsis (Δω = 21° ± 4°). This suggests that G1 is an independent object and not part of a gas stream containing G2, as has been proposed. Furthermore, we show for the first time that (1) G1 is extended in the epochs closest to periapsis along the direction of orbital motion, and (2) it becomes significantly smaller over time (450 au in 2004 to less than 170 au in 2009). Based on these observations, G1 appears to be the second example of an object tidally interacting with an SMBH. G1's existence 14 yr after periapsis, along with its compactness in epochs further from the time of periapsis, suggest that this source is stellar in nature.

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
Hees, A.0000-0002-2186-644X
Do, T.0000-0001-9554-6062
Lu, J. R.0000-0001-9611-0009
Naoz, S.0000-0002-9802-9279
Boehle, A.0000-0003-0439-7634
Martinez, G.0000-0002-7476-2521
Yelda, S.0000-0001-5036-4329
Additional Information:© 2017 American Astronomical Society. Received 2015 November 25. Accepted 2017 July 17. Published 2017 September 22. Support for this work was provided by NSF grants AST-0909218 and AST-1412615, the Levine-Leichtman Family Foundation, the Preston Family Graduate Fellowship (held by B.N.S. and A.B.), and the UCLA Graduate Division Dissertation Year Fellowship (held by B.N.S). The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The authors wish to recognize that the summit of Maunakea has always held a very significant cultural role for the indigenous Hawaiian community. We are most fortunate to have the opportunity to observe from this mountain. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. B.N.S. also thanks James Larkin for his engaging discussions about the nature of G1 and G2, Alexander Stephan for his comments, and Ann-Marie Madigan for her thoughts on G1. We thank Arezu Dehghanfar for help with preparing the manuscript. We thank the anonymous referee for providing fruitful comments.
Funding AgencyGrant Number
Levine-Leichtman Family FoundationUNSPECIFIED
Preston Family Graduate FellowshipUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20170922-103538437
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Official Citation:G. Witzel et al 2017 ApJ 847 80
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81743
Deposited By: Ruth Sustaita
Deposited On:22 Sep 2017 18:04
Last Modified:01 Nov 2019 20:18

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