January 1, 2008Open Access
Estimating the Spins of Stellar-Mass Black Holes by Fitting Their Continuum Spectra
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Abstract
We have used the Novikov‐Thorne thin disk model to fit the continuum X‐ray spectra of three transient black hole X‐ray binaries in the thermal state. From the fits we estimate the dimensionless spin parameters of the black holes to be: 4U 1543–47, a∗≡a/M = 0.7–0.85; GRO J1655–40, a∗ = 0.65–0.8; GRS 1915+105, a∗ = 0.98–1. We plan to expand the sample of spin estimates to about a dozen over the next several years. Some unresolved theoretical issues are briefly discussed.