The very high state accretion disk structure from the galactic black hole transient XTE J1550-564

We use the 1998 outburst of the bright Galactic black hole binary system XTEJ1550-564 to constrain the accretion disk structure in the strongly Comptonised, very high state spectral state. We show that the disk emission is not easily compatible with the constant area L ~ T^4 behaviour seen during the disk dominated high/soft state. Even after correcting for the effects of the scattering geometry, the disk temperature is always much lower than expected for its derived luminosity in the very high state. The simplest interpretation is that this indicates that the optically thick disk is truncated in the strong very high state, so trivially giving the observed continuity of properties between the low/hard/intermediate and very high states of Galactic black holes