Numerical Modeling of Multi-wavelength Spectra of M87 Core Emission

TL;DR

This study models M87's core emission across multiple wavelengths using GRMHD and Monte Carlo simulations, showing that accretion rate variations can explain observed X-ray variability without external jet influences.

Contribution

It introduces a comprehensive modeling approach combining GRMHD and Monte Carlo methods to fit M87's spectral data and assesses the role of accretion rate changes in X-ray variability.

Findings

Accretion disk model up to 28 GM/c^2 fits M87's core emissions.

High black hole spin (a/M > 0.8) drives polar outflows.

Variations in accretion rate (~20%) explain X-ray flux and spectral changes.

Abstract

Spectral fits to M87 core data from radio to hard x-ray are generated via a specially selected software suite, comprised of the HARM GRMHD accretion disk model and a 2D Monte Carlo radiation transport code. By determining appropriate parameter changes necessary to fit x-ray quiescent and flaring behavior of M87's core, we assess the reasonableness of various flaring mechanisms. This shows that an accretion disk model of M87's core out to 28 GM/c^2 can describe the inner emissions. High spin rates show GRMHD-driven polar outflow generation, without citing an external jet model. Our results favor accretion rate changes as the dominant mechanism of x-ray flux and index changes, with variations in density of approximately 20% necessary to scale between the average x-ray spectrum and flaring or quiescent spectra. The best fit parameters are black hole spin a/M > 0.8 and maximum accretion flow density n <= 3x10^7 cm^-3, equivalent to horizon accretion rates between m_dot = M_dot/M_dot_Edd ~ 2x10^-6 and 1x10^-5 (with M_dot_Edd defined assuming a radiative efficiency eta = 0.1). These results demonstrate that the immediate surroundings of M87's core are appropriate to explain observed x-ray variability.