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Testing for periodicities in near-IR light curves of Sgr A

Do, T. and Ghez, A. M. and Morris, M. R. and Yelda, S. and Lu, J. R. and Hornstein, S. D. and Matthews, K. (2008) Testing for periodicities in near-IR light curves of Sgr A. Journal of Physics: Conference Series, 131 . Art. No. 012003. ISSN 1742-6596.

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We present the results of near-infrared (2 μm) monitoring of Sgr A*-IR with 1 minute time sampling using laser guide star adaptive optics (LGS AO) system at the Keck II telescope. Sgr A*-IR was observed continuously for up to three hours on each of seven nights, between 2006 May and 2007 August. Sgr A*-IR is detected at all times and is continuously variable. These observations allow us to investigate Nyquist sampled periods ranging from about 2 minutes to an hour. Of particular interest are periods of ~20 min, which corresponds to a quasi-periodic (QPO) signal claimed based upon previous near-infrared observations and interpreted as the orbit of a ’hot spot’ at or near the last stable orbit of a spinning black hole. We investigate these claims by comparing periodograms of the light curves with models for red noise and find no significant deviations that would indicate QPO activity at any time scale probed in the study. We find that the variability of Sgr A* is consistent with a model based on correlated noise with a power spectrum having a frequency dependence of ~ f^(2.5), consistent with that observed in AGNs. Furthermore, the periodograms show power down to the minimum sampling time of 2 min, well below the period of the last stable orbit of a maximally spinning black hole, indicating that the Sgr A*-IR light curves observed in this study is unlikely to be from the Keplerian motion of a single ’hot spot’ of orbiting plasma.

Item Type:Article
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URLURL TypeDescription
Do, T.0000-0001-9554-6062
Ghez, A. M.0000-0003-3230-5055
Morris, M. R.0000-0002-6753-2066
Yelda, S.0000-0001-5036-4329
Lu, J. R.0000-0001-9611-0009
Additional Information:© 2008 IOP Publishing Ltd. Accepted papers received: 30 September 2008. Published online: 24 October 2008. The infrared 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 that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
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W. M. Keck FoundationUNSPECIFIED
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ID Code:13582
Deposited By: Ruth Sustaita
Deposited On:06 Jul 2009 22:31
Last Modified:01 Nov 2019 22:26

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