Magnetically arrested advective accretion flows and jets/outflows around stellar mass black holes: Explaining hard state ULXs with GRMHD simulations

TL;DR

This study uses GRMHD simulations to show how strong magnetic fields in accretion disks around stellar black holes can produce ultra-luminous X-ray sources in the hard state without super-Eddington accretion, explaining observed high luminosities.

Contribution

The paper demonstrates, through detailed simulations, that magnetic fields can account for ULX luminosities in the hard state without requiring intermediate-mass black holes or super-Eddington accretion.

Findings

Simulations reproduce ULX luminosities of 10^{39} - 10^{40} erg/s.

Strong magnetic fields enable super-Eddington luminosities without super-Eddington accretion.

The magnetic energy contributes significantly to the observed high luminosity.

Abstract

An optically thin advective accretion disk is crucial for explaining the hard state of black hole sources. Using general relativistic magnetohydrodynamic (GRMHD) simulations, we investigate how a large-scale, strong magnetic field influences accretion and outflows/jets, depending on the field geometry, magnetic field strength, and the spin parameter of the black hole. We simulate a sub-Eddington, advective disk-outflow system in the presence of a strong magnetic field, which likely remains in the hard state. The model simulations based on HARMPI successfully explain ultra-luminous X-ray sources (ULXs) in the hard state, typically observed with luminosities ranging from $10^{39}$ - $10^{40}$ ergs s$^{-1}$. Our simulations generally describe the bright, hard state of stellar-mass black hole sources without requiring a super-Eddington accretion rate. This work explores the characteristics of ULXs without invoking intermediate-mass black holes. The observed high luminosity is attributed to the energy stored in the strong magnetic fields, which can generate super-Eddington luminosity. The combined energy of the matter and magnetic field leads to such significant luminosity.