Slim Disks with Transition Regions and Applications to Microquasars and Narrow Line Seyfert 1 Galaxies

Abstract

Slim disks have been received much attention because of the increasing evidence for the super-critical accreting objects. In this paper, we make an attempt to construct a unified model, in which the viscosity and the dimensionless accretion rate can span rather wide ranges. We replace blackbody radiation under diffusion approximation with a bridged formula, which accounts for both blackbody radiation and thermal bremsstrahlung in optically-thick and -thin cases, respectively. Thus this allows us to investigate the structures of and the emergent spectra from slim disks in a wider parameter space, covering transition regions from optically thick to optically thin. We show that there is a maximum transition radius, roughly $R_{\rm tr, max}/R_g\sim 50$ when $\dot{M}/\dot{M}_{\rm C}\sim 15$. The emergent spectra from the unified model of the accretion disk have been calculated. A simple model of hot corona above the slim disk is taken into account for the hard X-ray spectrum in this paper based on Wang & Netzer (2003). We have applied the present model to the microquasar GRS 1915+105, narrow line Seyfert 1 galaxies RE J1034+396 and Akn 564. Our model can explain well the broadband X-ray spectra of narrow line Seyfert 1 galaxies, microquasars and possible ultra-luminous compact X-ray sources. The present model can be widely applied to the candidates of super-critical accreting objects.