Magnetic inversion as a mechanism for the spectral transition of black hole binaries

TL;DR

This paper proposes a magnetic inversion mechanism explaining spectral state transitions in black hole X-ray binaries, linking magnetic field dynamics with accretion disk states and jet formation.

Contribution

It introduces a novel magnetic inversion model that accounts for the spectral state transitions and jet activity in black hole binaries.

Findings

Magnetically arrested disks explain low/hard states and jet formation.

Magnetic field inversion causes state transitions between spectral states.

The model links magnetic dynamics with observed X-ray spectral changes.

Abstract

A mechanism for the transition between low/hard, high/soft, and steep power law (SPL) spectral states in black hole X-ray binaries is proposed. The low/hard state is explained by the development of a magnetically arrested accretion disk attributable to the accumulation of a vertical magnetic field in a central bundle. This disk forms powerful jets and consists of thin spiral accretion streams of a dense optically thick plasma surrounded by hot, magnetized, optically thin corona, which emits most of the energy in hard X-rays. State transition occurs because of the quasi-periodic or random inversion of poloidal magnetic fields in the accretion flow supplied by the secondary star. The inward advection of the inverted field results in a temporal disappearance of the central bundle caused by the annihilation of the opposed fields and restoration of the optically thick disk in the innermost region. This disk represents the high/soft state. The SPL state develops at the period of intensive field annihilation and precedes the high/soft state. The continuous supply of the inverted field leads to a new low/hard state because of the formation of another magnetically arrested disk.