ACCRETION DISK EVOLUTION WITH WIND INFALL .1. GENERAL-SOLUTION AND APPLICATION TO SAGITTARIUS A-ASTERISK

The evolution of an accretion disk can be influenced significantly by the deposition of mass and angular momentum by an infalling Bondi-Hoyl e wind. Such a mass influx impacts the long-term behavior of the disk by providing additional sources of viscosity and heating. In this pape r, we derive and solve the disk equations when these effects are taken into account. We present a survey of models with various wind configu rations and demonstrate that the disk spectrum may then differ substan tially from that of a standard alpha-disk. In particular, it is likely that a wind-fed disk has a significant infrared bump due to the depos ition of energy in its outer region. We apply some of the results of o ur calculations to the Galactic center black hole candidate Sagittariu s A and show that if a fossil disk is present in this source, it must have a very low viscosity parameter (alpha less than or similar to 10 (-4)) and the Bondi-Hoyle wind must be accreting with a very high spec ific angular momentum to prevent it from circularizing in the inner di sk region where its impact would be most noticeable.