JAPC - Measuring Black Hole Spin: Progress, Problems and Promise

Speaker: Dr. Jeffrey E. McClintock, Harvard/Smithsonian Center for Astrophysics

Topic: "Measuring Black Hole Spin: Progress, Problems and Promise "

Time: 2:00 PM, Friday, March 28th, 2008

Place: P-148 (refreshments will be served at 1:45 PM in P145A)

Abstract: Our group has estimated the spins of four stellar-mass black holes, which are located in X-ray binary systems. We now have preliminary results for another three and expect to publish the results of a dozen or more in total during the next few years. In principle, the method we use is simple, and it is completely analogous to the method one uses to determine the radius of an ordinary star given its distance, temperature and magnitude. We fit the thermal X-ray spectrum of the black hole to a fully relativistic model of an accretion disk and thereby determine the radius of the inner edge of the disk. We identify this inner disk radius with the innermost stable circular orbit (ISCO), whose radius depends only on the mass and spin of the black hole. Two main areas of uncertainty will be discussed: (1) the validity of the relativistic model used to analyze the observations, which is being addressed in ongoing theoretical work; and (2) our assumption that the black hole spin is approximately aligned with the angular momentum vector of the binary, which can be addressed by a future X-ray polarimetry mission.

You can view JAPC upcoming talks or the archive.