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| Titre : |
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The Two States of Sgr A* in the Near-infrared: Bright Episodic Flares on Top of Low-level Continuous Variability |
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| Auteur(s) : |
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K. Dodds-Eden, S. Gillessen, T. K. Fritz, F. Eisenhauer, S. Trippe, R. Genzel, T. Ott, H. Bartko, O. Pfuhl, G. Bower, A. Goldwurm1, 2, D. Porquet3, G. Trap1, 2, F. Yusef-Zadeh |
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| Laboratoire : |
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| équipe(s) de recherche : |
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APC - AHE |
| Résumé : |
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In this paper, we examine properties of the variable source Sgr A* in the near-infrared (NIR) using a very extensive Ks-band data set from NACO/VLT observations taken in 2004-2009. We investigate the variability of Sgr A* with two different photometric methods and analyze its flux distribution. We find that Sgr A* is continuously emitting and continuously variable in the near-infrared, with some variability occurring on timescales as long as weeks. The flux distribution can be described by a lognormal distribution at low intrinsic fluxes (lsim5 mJy, dereddened with AKs = 2.5). The lognormal distribution has a median flux of ≈1.1 mJy, but above 5 mJy the flux distribution is significantly flatter (high flux events are more common) than expected for the extrapolation of the lognormal distribution to high fluxes. We make a general identification of the low-level emission above 5 mJy as flaring emission and of the low-level emission as the quiescent state. We also report here the brightest Ks-band flare ever observed (from 2008 August 5) which reached an intrinsic Ks-band flux of 27.5 mJy (mKs = 13.5). This flare was a factor 27 increase over the median flux of Sgr A*, close to double the brightness of the star S2, and 40% brighter than the next brightest flare ever observed from Sgr A*. |
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Langue du texte
intégral : |
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Anglais |
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Date de production,
écriture : |
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30/11/2010 |
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| Journal : |
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| Astrophysical Journal (Astrophys. J.) |
| Publisher |
American Astronomical Society |
| ISSN |
0004-637X |
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| Audience : |
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internationale |
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| Type de publication : |
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Articles dans des revues avec comité de lecture |
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| Date de publication : |
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02/2011 |
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| Volume : |
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728 |
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| Page, identifiant, ... : |
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37 |
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| Mots Clés : |
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accretion – accretion disks – black hole physics – Galaxy: center – infrared: general |
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| Commentaire : |
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14 pages, 6 figures, accepted for publication in ApJ |
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