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Consistency of the Infrared Variability of SGR A* over 22 yr

Chen, Zhuo and Gallego-Cano, E. and Do, T. and Witzel, G. and Ghez, A. M. and Schödel, R. and Sitarski, B. N. and Becklin, E. E. and Lu, J. and Morris, M. R. and Dehghanfar, A. and Gautam, A. K. and Hees, A. and Hosek, M. W., Jr. and Jia, S. and Mangian, A. C. and Matthews, K. (2019) Consistency of the Infrared Variability of SGR A* over 22 yr. Astrophysical Journal Letters, 882 (2). Art. No. L28. ISSN 2041-8213. https://resolver.caltech.edu/CaltechAUTHORS:20191003-113816483

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Abstract

We report new infrared (IR) measurements of the supermassive black hole at the Galactic Center, Sgr A*, over a decade that was previously inaccessible at these wavelengths. This enables a variability study that addresses variability timescales that are 10 times longer than earlier published studies. Sgr A* was initially detected in the near-infrared (NIR) with adaptive optics observations in 2002. While earlier data exists in form of speckle imaging (1995–2005), Sgr A* was not detected in the initial analysis. Here, we improved our speckle holography analysis techniques. This has improved the sensitivity of the resulting speckle images by up to a factor of three. Sgr A* is now detectable in the majority of epochs covering 7 yr. The brightness of Sgr A* in the speckle data has an average observed K magnitude of 16.0, which corresponds to a dereddened flux density of 3.4 mJy. Furthermore, the flat power spectral density of Sgr A* between ~80 days and 7 yr shows its uncorrelation in time beyond the proposed single power-law break of ~245 minutes. We report that the brightness and its variability is consistent over 22 yr. This analysis is based on simulations using the Witzel et al. model to characterize IR variability from 2006 to 2016. Finally, we note that the 2001 periapse of the extended, dusty object G1 had no apparent effect on the NIR emission from accretion flow onto Sgr A*. The result is consistent with G1 being a self-gravitating object rather than a disrupting gas cloud.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/2041-8213/ab3c68DOIArticle
ORCID:
AuthorORCID
Chen, Zhuo0000-0002-3038-3896
Gallego-Cano, E.0000-0002-7452-1496
Do, T.0000-0001-9554-6062
Witzel, G.0000-0003-2618-797X
Ghez, A. M.0000-0003-3230-5055
Lu, J.0000-0001-9611-0009
Morris, M. R.0000-0002-6753-2066
Dehghanfar, A.0000-0003-0518-944X
Gautam, A. K.0000-0002-2836-117X
Hees, A.0000-0002-2186-644X
Hosek, M. W., Jr.0000-0003-2874-1196
Jia, S.0000-0001-5341-0765
Mangian, A. C.0000-0003-2385-6904
Additional Information:© 2019. The American Astronomical Society. Received 2019 June 22; revised 2019 July 30; accepted 2019 August 17; published 2019 September 11. The primary support for this work was provided by NSF, through grant AST-1412615, and UCLA, through faculty salaries. Additional support was received from the Heising-Simons Foundation, the Levine-Leichtman Family Foundation, the Preston Family Graduate Fellowship (held by B.N.S and A.G.), UCLA Galactic Center Star Society, UCLA Cross–disciplinary Scholars in Science and Technology (CSST) Fellowship, NSF Research Experiences for Undergraduates (REU) grant No. PHY-1460055, and the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement No. [614922] (R.S.). This research was based on data products from the Galactic Center Orbit Initiative (GCOI), which is hosted at UCLA and which is a key science program of the Galactic Center Collaboration (GCC). These data products were derived from data originally obtained from W. M. Keck Observatory. 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.
Funders:
Funding AgencyGrant Number
NSFAST-1412615
UCLAUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Levine-Leichtman Family FoundationUNSPECIFIED
Preston Family Graduate FellowshipUNSPECIFIED
UCLA Galactic Center Star SocietyUNSPECIFIED
NSFPHY-1460055
European Research Council (ERC)614922
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:accretion, accretion disks; black hole physics; Galaxy: center; techniques: high angular resolution
Issue or Number:2
Record Number:CaltechAUTHORS:20191003-113816483
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20191003-113816483
Official Citation:Zhuo Chen et al 2019 ApJL 882 L28
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99054
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:03 Oct 2019 22:47
Last Modified:04 Nov 2019 18:50

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