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D. Proga (GSFC/NASA, NRC), T.R. Kallman (GSFC/NASA)
The X-ray heating of the photosphere of an accretion disk is an obvious mechanism to produce relatively strong, broad and single peaked UV emission lines in low mass X-ray binaries (LMXBs). However detailed photoionization calculations show that this mechanism fails to produce sufficient emission measure at suitable ionization and optical depth. We present the results of hydrodynamical calculations of the disk photosphere irradiated by strong X-rays. We attempt to determine whether LMXBs can harbor significant UV-driven disk winds despite the effects of X-ray ionization. Such winds would be a likely candidate for the site of emission of UV lines and may better explain the observations than the X-ray heated disk photosphere.
This work was performed while DP held a National Research Council Research Associateship at NASA/GSFC.