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<i>CHANDRA</i>/HETGS OBSERVATIONS OF THE BRIGHTEST FLARE SEEN FROM Sgr A*

M. A. NowakMassachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139, USA; [email protected], [email protected], [email protected], [email protected]J. NeilsenMassachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139, USA; [email protected], [email protected], [email protected], [email protected]S. B. MarkoffAstronomical Institute, “Anton Pannekoek,” University of Amsterdam, Amsterdam, The Netherlands; [email protected]F. K. BaganoffMassachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139, USA; [email protected], [email protected], [email protected], [email protected]D. PorquetObservatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, France; [email protected], [email protected]N. GrossoObservatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, France; [email protected], [email protected]Y. LevinLeiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The NetherlandsJ. HouckMassachusetts Institute of Technology, Kavli Institute for Astrophysics, Cambridge, MA 02139, USA; [email protected], [email protected], [email protected], [email protected]A. EckartPhysikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany; [email protected]H. FalckeASTRON, Postbus 2, 7990 AA Dwingeloo, The NetherlandsL. JiPurple Mountain Observatory, CAS, 210008 Nanjing, People's Republic of China; [email protected]J. M. MillerDepartment of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA; [email protected]Q. D. WangDepartment of Astronomy, University of Massachusetts, Amherst, MA 01002, USA; [email protected]

2012en

ABI

Аннотация

Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A*, utilizing the High Energy Transmission Grating Spectrometer (HETGS) instrument on the Chandra X-Ray Observatory. These observations will allow us to measure the quiescent X-ray spectra of Sgr A* for the first time at both high spatial and spectral resolution. The X-ray emission of Sgr A*, however, is known to flare roughly daily by factors of a few to ten times over quiescent emission levels, with rarer flares extending to factors of greater than 100 times quiescence. Here we report an observation performed on 2012 February 9 wherein we detected what are the highest peak flux and fluence flare ever observed from Sgr A*. The flare, which lasted for 5.6 ks and had a decidedly asymmetric profile with a faster decline than rise, achieved a mean absorbed 2-8 keV flux of (8.5 +/- 0.9) x 10(-12) erg cm(-2) s(-1). The peak flux was 2.5 times higher, and the total 2-10 keV emission of the event was approximately 10(39) erg. Only one other flare of comparable magnitude, but shorter duration, has been observed in Sgr A* by XMM-Newton in 2002 October. We perform spectral fits of this Chandra-observed flare and compare our results to the two brightest flares ever observed with XMM-Newton. We find good agreement among the fitted spectral slopes (Gamma similar to 2) and X-ray absorbing columns (N-H similar to 15 x 10(22) cm(-2)) for all three of these events, resolving prior differences (which are most likely due to the combined effects of pileup and spectral modeling) among Chandra and XMM-Newton observations of Sgr A* flares. We also discuss fits to the quiescent spectra of Sgr A*.

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DOI: 10.1088/0004-637x/759/2/95

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