Disk Emission from Magneto-hydrodynamic Simulations of Spinning Black Holes

TL;DR

This paper presents 3D relativistic MHD simulations of thin accretion disks around spinning black holes, demonstrating improved spectral modeling and the potential to resolve spin-inclination degeneracies through spectropolarization.

Contribution

It introduces a universal emissivity profile for disk spectra and shows how spectropolarization can break degeneracies in black hole spin measurements.

Findings

Simulated spectra fit better with a universal emissivity profile.

Spectropolarization can resolve spin-inclination degeneracy.

Disks modeled with different spins produce distinct polarization signatures.

Abstract

We present the results of a new series of global 3D relativistic magneto-hydrodynamic (MHD) simulations of thin accretion disks around spinning black holes. The disks have aspect ratios of $H/R\sim 0.05$ and spin parameters $a/M=0, 0.5, 0.9$, and $0.99$. Using the ray-tracing code Pandurata, we generate broad-band thermal spectra and polarization signatures from the MHD simulations. We find that the simulated spectra can be well fit with a simple, universal emissivity profile that better reproduces the behavior of the emission from the inner disk, compared to traditional analyses carried out using a Novikov-Thorne thin disk model. Lastly, we show how spectropolarization observations can be used to convincingly break the spin-inclination degeneracy well-known to the continuum fitting method of measuring black hole spin.