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[39.02] On the Role of Irradiation and Evaporation in Accretion Disks

J. K. Cannizzo (GSFC/LHEA/Univ. Space Res. Assoc.)

Evaporation is an inevitable consequence of viscous dissipation in the coronae of accretion disks, as first shown by Shaviv & Wehrse. Recently deKool & Wickramasinghe presented a simple formalism for investigating the optically thin structure of accretion disks using a photoionization balance code. We report on an investigation using G. Ferland's program CLOUDY to determine an extensive grid of mass loss rates from disks covering a range of physical parameters (in radius, mass accretion rate, and irradiation), and utilize this information in our time dependent accretion disk code to calculate outburst light curves for systems undergoing limit cycle oscillations. We find that for dwarf nova parameters, evaporation does not strongly affect the outburst light curves, but does influence the recurrence time scales. For black hole X-ray nova parameters, the functional form of the light curve is substantially different from that found by previous workers who took into account the effect of the blocking of the cooling front by irradiation during the decay of an outburst, but not the irradiation-induced mass loss from the accretion disk.

JKC was supported through the long-term scientist program under the Universities Space Research Association (USRA contract NAS5-32484) in the Laboratory for High Energy Astrophysics at Goddard Space Flight Center.