Spectral transitions in Cygnus X-1 and other black hole X-ray binaries

We show that the model proposed by Esin, McClintock, & Narayan for the low state, intermediate stale, and high state of the black hole soft X-ray tran sient, Nova Muscae 1991, is consistent with the spectral evolution of the b lack hole X-ray binary, Cyg X-1, during the hard-to-soft slate transition o bserved in 1996. We also apply the model to the outbursts of two other blac k hole X-ray transients, GRO J0422 + 32 and GRO J1719 - 24.