Simulating black hole binaries

Abstract

Black hole binaries (BHBs) undergo state transitions during which their spectral and timing properties change dramatically. The nature of these state transitions is a long-standing open question. One leading idea is that they are associated with modulations in the mass accretion rate $\dot{M}$ which affect the amount of radiative cooling in the accretion flow. The goal of this project is to address the nature of state transitions in BHBs, by performing global 3D GRMHD simulations of accretion flows around stellar mass black holes (BH), incorporating the radiative cooling self-consistently in the dynamics through the bremsstrahlung, synchrotron and inverse Compton processes. We will use a state-of-the-art GPU-accelerated code and quantify how the inner radius of the thin disk and the properties of the hot corona (e.g. size and temperature) are related to the fundamental system properties such as $\dot{M}$ and BH spin. Along the way, we will compare our results with BHB observations. (AU)