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

Understand

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.