We use the Novikov-Thorne thin disk model to fit the thermal continuum X-ray spectra of black hole X-ray binaries, and thereby extract the dimensionless spin parameter a∗=a/M of the black hole as a parameter of the fit. We summarize the results obtained to date for six systems and
describe work in progress on additional systems. We also describe recent methodological advances, our current efforts to make our analysis software fully available to others, and our theoretical efforts to validate the Novikov-Thorne model.
