Title: Accretion topics in astrophysics
Description: Accretion theory is essential for understanding a multitude of varied astronomical observations such as X-ray binaries, active galactic nuclei and gamma-ray bursts. In this document three works on accretion will be presented.The first one is on the structure of an inviscid accretion disc with small angular momentum around a rotating black hole. This regime of accretion may occur in X-ray binaries and GRBs. The second work is on neutrino antineutrino annihilation in the vicinity of a hyper-accreting black hole. This work is relevant for the study of GRBs, in particular it singles out when neutrinos may be responsible for powering GRBs. The third work studies the tidal stripping of a white dwarf spiraling into a massive black hole. The stripped matter accretes onto the black hole producing a transient emission, presumably periodic, observable with X-ray and optical telescopes. At the same time the white dwarf emits gravitational waves as it spirals into the black hole.