Microquasar: Disk Models

Abstract

Basic disk models are reviewed with special attention on the dynamics of near- or super-critical accretion regimes. High accretion-rate flows are observed in many different systems and interaction between radiation and gas is key physics in this regime. GRS 1915+105 seems to probe the presence of transitions between the standard-disk and slim-disk branches. At even higher accretion rates (> LE/c2), significant photon trapping effects appear, leading to spectral softening, because hard photons are more effectively trapped by the flow.