Chandra Observations of the Nearest Black Holes

Mike Garcia

Black holes, as described by general relativity, are widely accepted as true members of the stellar family. They are believed to power some of the most energetic phenomenon in the universe, ie, quasars, active galaxies, and gamma-ray bursts. Despite this, evidence of one of their most basic properties: that they are 'black', has been difficult to obtain. Chandra observations of Galactic black hole binaries has produced some of the first good evidence that objects we believe are black holes are indeed 'black'. The superb resolution and sensitivity of Chandra allows us to extend our studies of 'Galactic' black hole binaries to our nearest neighbor galaxy, M31. Synoptic observations have allowed X-ray detection of many such binaries, and HST followup has allowed discovery of the first optical counterpart. The supermassive black hole in the center of M31 is surprisingly faint in the X-ray band.