CfA Colloquium Schedule Fall 2006
 12 October 2006

12 October 2006

Speaker: Jeff McClintock (CfA)

Title: The Spin of the Near-Extreme Kerr Black Hole GRS 1915+105

Abstract: Starting with Cygnus X-1, we now have a good sample of 21 stellar-mass black holes, that is, compact binary X-ray sources that are more massive than 3 suns. The next obvious step is to measure spin, since mass and spin (and charge) completely define a black hole, just as these quantities define an electron or a quark. Using the straightforward methodology of fitting the X-ray continuum spectrum of the black-hole's accretion disk, our team has estimated the spins of three black holes. Most exciting is our result for the microquasar GRS1915+105, which has a spin that is between 98% and 100% of the theoretical maximum value. We hope to estimate the spins of a dozen additional black holes during the next several years. Black hole spin is important for theories of black-hole formation, for models of relativistic jets and gamma-ray bursts, and for gravitational-wave astronomy.

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