Numerical Simulations of Optically Thick Accretion onto a Black Hole - II. Rotating Flow

TL;DR

This paper presents advancements in a relativistic radiation magnetohydrodynamics code, enabling simulations of complex black hole accretion flows with broader optical depth ranges and improved stability, advancing understanding of super-Eddington accretion phenomena.

Contribution

Development of a new primitive inversion scheme and hybrid solver in Cosmos++ that broadens simulation capabilities for radiation-pressure-dominated black hole accretion disks.

Findings

Successfully tested the new methods against various problems.

Demonstrated ability to simulate super-Eddington, quasi-spherical accretion.

Hints of complex radiation-gas interactions in initial simulations.

Abstract

In this paper we report on recent upgrades to our general relativistic radiation magnetohydrodynamics code, Cosmos++, including the development of a new primitive inversion scheme and a hybrid implicit-explicit solver with a more general closure relation for the radiation equations. The new hybrid solver helps stabilize the treatment of the radiation source terms, while the new closure allows for a much broader range of optical depths to be considered. These changes allow us to expand by orders of magnitude the range of temperatures, opacities, and mass accretion rates, and move a step closer toward our goal of performing global simulations of radiation-pressure-dominated black hole accretion disks. In this work we test and validate the new method against an array of problems. We also demonstrate its ability to handle super-Eddington, quasi-spherical accretion. Even with just a single proof-of-principle simulation, we already see tantalizing hints of the interesting phenomenology associated with the coupling of radiation and gas in super-Eddington accretion flows.