Calendar

Astrophysics, Relativity, and Cosmology Seminar - Lizhong Zhang (Flatiron Institute) "Modeling Black Hole Accretion with Radiation GRMHD: A Parameter Survey and Connection to Observations"

Speaker: Lizhong Zhang, Flatiron Institute
Date: 4/30/2025
Time: 12 p.m.
Location: Rhondale Tso Seminar Room, Loomis 236
Event Contact: Deanna Frye
ddebord@illinois.edu
Sponsor: Department of Physics
Event Type: Seminar/Symposium
 

Radiation and magnetic fields play crucial roles in shaping black hole accretion across a wide range of regimes. To model these systems, we solve the GRMHD equations coupled with angle-dependent radiation transfer, which enables us to capture the complex dynamics of accretion in extreme environments � from super-Eddington to sub-Eddington regimes. In the super-Eddington regime, radiative support causes the accretion disk to thermally 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 magnetic coronae or a magnetically elevated disk.  These simulations broadly align with observational findings � such as the soft states of X-ray binaries, ultraluminous X-ray sources, and �little red dots� � and offer predictive diagnostics for future observations, which I will discuss in detail during the talk.