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Estimating the Spin of Stellar-Mass Black Holes by Spectral Fitting of the X-Ray Continuum

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Published 2005 December 30 © 2006. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation Rebecca Shafee et al 2006 ApJ 636 L113 DOI 10.1086/498938

1538-4357/636/2/L113

Abstract

We fit X-ray spectral data in the thermal-dominant, or high-soft, state of two dynamically confirmed black holes, GRO J1655-40 and 4U 1543-47, and estimate the dimensionless spin parameters a*a/M of the two holes. For GRO J1655-40, using a spectral hardening factor computed for a non-LTE relativistic accretion disk, we estimate a* ~ 0.75 and a* ~ 0.65-0.75, respectively, from ASCA and RXTE data. For 4U 1543-47, we estimate a* ~ 0.75-0.85 from RXTE data. Thus, neither black hole has a spin approaching the theoretical maximum a* = 1.

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10.1086/498938