Lizhong Zhang (CCA, Flatiron Institute)
Title: Modeling Black Hole Accretion with Radiation GRMHD: A Parameter Survey and Connection to Observations
Abstract: Radiation and magnetic fields play crucial rolesin shaping black hole accretion across a wide range of regimes. To model thesesystems, we solve the GRMHD equations coupled with angle-dependent radiationtransfer, which enables us to capture the complex dynamics of accretion inextreme environments — from super-Eddington to sub-Eddington regimes. In thesuper-Eddington regime, radiative support causes the accretion disk tothermally expand, forming a narrow conical funnel through which radiation escapes,leading to low radiation efficiency. In the sub- and near-Eddington regimes,the magnetic field topology strongly influences the resulting disk structure,allowing the system to reach a steady state as either a thin disk with magneticcoronae or a magnetically elevated disk. These simulations broadly alignwith observational findings — such as the soft states of X-ray binaries,ultraluminous X-ray sources, and “little red dots” — and offer predictivediagnostics for future observations, which I will discuss in detail during thetalk.
