Role of magnetically dominated disc-outflow symbiosis on bright hard-state black hole sources: ultra-luminous X-ray sources to quasars

TL;DR

This paper proposes a magnetically dominated disc-outflow model around black holes that explains high luminosity in bright hard-state sources, including ULXs and quasars, without requiring super-Eddington accretion or intermediate-mass black holes.

Contribution

It introduces a new magnetically dominated disc-outflow symbiosis model that accounts for high luminosity in black hole systems across a wide mass range, emphasizing magnetic fields and energy advection effects.

Findings

Magnetically dominated flow achieves high luminosity at sub-Eddington rates.

Model explains ULXs with hard spectra without invoking IMBHs.

Supermassive black hole quasars' luminosity also explained by the model.

Abstract

We present optically thin solutions for magnetized, advective disc-outflow symbiosis around black holes (BHs). The main objective is to explain the bright, hard state observations of accreting systems with stellar-mass to supermassive BHs. We include the effects of magnetic fields and radiation counterpart in entropy gradient based on the first law of thermodynamics to represent energy advection. The cooling process includes bremsstrahlung, synchrotron radiation, and inverse Comptonization process. One of our main ventures is to explain some long-standing issues of ultra-luminous X-ray sources (ULXs). The existing physical scenarios to explain their unusual high luminosity are either the existence of the missing class of intermediate-mass BH (IMBH), or super-Eddington accretion around a stellar-mass BH. However, most ULXs with steep power-law spectrum can be well explained through super-Eddington accretion, while the existence of IMBH is indeed disputed extensively. Nevertheless, the interpretation of ULXs with a hard power-law dominated state remains mysterious. Here we show that our magnetically dominated disc-outflow symbiosis around rapidly spinning stellar-mass BHs can achieve such large luminosity even for sub-Eddington accretion rate. The magnetic field at the outer zone of the advective flow is more than the corresponding Eddington limit. Such field becomes dynamically dominant near the BH through continuous accretion process due to flux freezing, but maintaining its Eddington limit. This unique field configurations enhance the synchrotron, and synchrotron self-Comptonization process to achieve very large luminosity. Through the same mechanism, our solutions for supermassive BHs can explain the unusual large luminosity of ultra-luminous quasars.