Accretion Disk-Outflow/Jet and Hard State ULXs

TL;DR

This paper uses GRMHD simulations to demonstrate that highly magnetized accretion flows around stellar black holes can produce ULX-like luminosities, supporting the idea that ULXs in hard states are super-Eddington accretion systems with strong magnetic fields.

Contribution

It provides the first GRMHD simulation evidence that highly magnetized accretion flows can generate ULX luminosities, confirming previous steady-state calculations and elucidating emission mechanisms.

Findings

Magnetic fields of around 10^7 G are sufficient for ULX luminosities.

Simulated power profiles reveal emission features from Blandford-Znajek and Blandford-Payne mechanisms.

Highly magnetized advective accretion flows can explain ULXs in hard states.

Abstract

Ultraluminous X-ray sources (ULXs) have been objects of great interest for the past few decades due to their unusually high luminosities and spectral properties. A few of these sources exhibit super-Eddington luminosities assuming them to be centering around stellar mass objects, even in their hard state. It has been shown via numerical steady state calculations that ULXs in hard state can be interpreted as highly magnetised advective accretion sources around stellar mass black holes. We use general relativistic magnetohydrodynamic (GRMHD) framework to simulate highly magnetised advective accretion flows around a black hole and show that such systems can indeed produce high luminosities like ULXs. We also verify that the magnetic fields required for such high emissions is around $10^7$ G, in accordance with previous numerical steady state calculations. We further present power profiles for zero angular momentum observer (ZAMO) frame. These profiles show interesting features which can be interpreted as effects of emission due to the Blandford-Znajek and Blandford-Payne mechanisms.