CfA Colloquium Schedule Fall 2007
 6 December 2007

6 December 2007

Speaker: Frederick Baganoff (MIT)

Title: How Luminous Was the Galactic Supermassive Black Hole in the Past?

Abstract:Repeated deep Chandra monitoring of Sgr A* over the past few years has revealed rapidly variable Fe fluorescence features within 6' (14 pc in projection) of the supermassive black hole, suggesting that its X-ray luminosity may have been greater than 10^38 erg/s for at least 2-3 years about 60 years ago, before the first X- ray satellites were launched. These results will be discussed in the context of X-ray observations of Fe fluorescence in Sgr B2 and Sgr C, and arguments will be presented against the alternative hypotheses of irradiation by local X-ray binaries or excitation by low-energy cosmic ray electrons. In addition, some results from the latest multiwavelength monitoring campaigns on Sgr A* will be presented, including the first clear detection of a sub-mm counterpart with the SMA to a flare seen in the X-ray and IR bands by Chandra and Keck.

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