Dr. Craig Wheeler will use this award to explore thermal instabilities in accretion disks in a variety of contexts in order to gain a deeper understanding of transient phenomena in binary stars and related systems. An attempt will be made to incorporate models of non-local angular momentum transport to supplant current models for viscosity. The sensitivity of unstable disks to key parameters, such as transfer rate, inner and outer disk radii, central mass, and viscosity, will be explored. Models of the magnetically truncated disk of the intermediate polar binary system GK Per will be refined to make quantitative predictions of the X- ray, ultraviolet, and optical behavior of the next outburst expected about mid 1992. Models incorporating time dependent coronae and the attendant effects of disk irradiation from the inner disk, the compact object, and the corona will be used to explore the behavior of soft X-ray transients like Agl X-1 and Cen X-4 which contain neutron stars and a number of transient black hole candidates.
