AST 95-29230 PI: Omer Blaes Optical/Ultraviolet Emission from active Galactic Nuclei The origin of the optical/UV spectrum in Active Galactic Nuclei is not currently understood. X-ray observations suggest that the standard thin accretion disk paradigm be altered in such a way that a substantial fraction of the gravitational energy be transferred and released outside the optically thick portion of the disk, but it is not clear that such a model can explain all the optical/UV observations. The PI will investigate the consequences of two-phase models (disk and overlying hot corona) for the optical and ultraviolet observations, concentrating in particular on the spectrum and polarization that a non-LTE, self-consistent, atmosphere code would produce. The model, which assumes that the disk and corona are locally coupled at each radius, will explore the parameter space defined by the fraction of accretion power dissipated in the corona and the coronal optical depth. The UV/optical response to X-ray variability will also be studied.
