Shafee, RebeccaMcClintock, Jeffrey E.Narayan, RameshDavis, Shane W.Li, Li-XinRemillard, Ronald A.McClintock, JeffreyDavis, ShaneRemillard, Ronald2019-09-222005Shafee, Rebecca, Jeffrey E. McClintock, Ramesh Narayan, Shane W. Davis, Li-Xin Li, and Ronald A. Remillard. 2005. “Estimating the Spin of Stellar-Mass Black Holes by Spectral Fitting of the X-Ray Continuum.” The Astrophysical Journal 636 (2): L113–16. https://doi.org/10.1086/498938.0004-637X1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384965We 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*similar to 0.75 and a*similar to 0.65-0.75, respectively, from ASCA and RXTE data. For 4U 1543-47, we estimate a*similar to 0.75-0.85 from RXTE data. Thus, neither black hole has a spin approaching the theoretical maximum a* = 1.en-USJournal Article2019-09-2210.1086/498938