Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

Rapid accretion of matter into either stellar mass or supermassive black holes produces some the most luminous objects in the Universe, such as quasars, ultra-luminous X-ray sources (ULXs), and tidal disruption events. Understanding such flows is important not only for interpreting the spectra and variability of these sources, but also to predict the rate of growth of black holes in the early universe, and to quantify energy and momentum feedback into the medium surrounding the black hole (a process likely to be important in controlling galaxy formation in the case of AGN). New results from a study of the magnetohydrodynamics (MHD) of luminous accretion flows, in which radiation pressure dominates, will be presented. We have developed new numerical methods for solving the equations of radiation MHD based on a formal solution of the time-dependent radiation transfer equation to study this regime. Our numerical simulations reveal new effects that require extension of standard thin-disk models. We discuss these results, and their implications for the astrophysics of accreting black holes.