grmonty: a Monte Carlo Code for Relativistic Radiative Transport

TL;DR

This paper introduces 'grmonty', a Monte Carlo code for simulating radiative transfer in relativistic plasmas, specifically modeling spectra from hot accretion flows around black holes in full general relativity.

Contribution

The paper presents a new Monte Carlo radiative transfer code capable of modeling spectra in relativistic spacetimes, including synchrotron and Compton processes, with demonstrated convergence and application to black hole accretion.

Findings

Code accurately models spectra of relativistic plasmas.

Demonstrates expected Monte Carlo convergence rate.

Applied to Sgr A* with realistic accretion data.

Abstract

We describe a Monte Carlo radiative transport code intended for calculating spectra of hot, optically thin plasmas in full general relativity. The version we describe here is designed to model hot accretion flows in the Kerr metric and therefore incorporates synchrotron emission and absorption, and Compton scattering. The code can be readily generalized, however, to account for other radiative processes and an arbitrary spacetime. We describe a suite of test problems, and demonstrate the expected $N^{-1/2}$ convergence rate, where $N$ is the number of Monte Carlo samples. Finally we illustrate the capabilities of the code with a model calculation, a spectrum of the slowly accreting black hole Sgr A* based on data provided by a numerical general relativistic MHD model of the accreting plasma.