A Circumbinary Disk Model for the Rapid Orbital Shrinkage in Black Hole Low-Mass X-ray Binaries

TL;DR

This paper proposes a circumbinary disk model to explain rapid orbital shrinkage in black hole low-mass X-ray binaries, showing that disk-binary interactions can account for observed orbital changes without high mass transfer rates.

Contribution

It introduces a new model involving circumbinary disks formed from outburst mass loss to explain fast orbital decay in BHLMXBs, supported by detailed evolution calculations.

Findings

Circumbinary disks can cause rapid orbital shrinkage in BHLMXBs.

The model explains observations without requiring high mass transfer rates.

Disk formation scenarios from single or successive outbursts are viable.

Abstract

Several black hole low-mass X-ray binaries (BHLMXBs) show very fast orbital shrinkage, which is difficult to understand in the standard picture of the LMXB evolution. Based on the possible detection of a circumbinary (CB) disk in A0620-00 and XTE J1118+480, we investigate the influence of the interaction between a CB disk and the inner binary and calculate the evolution of the binary using the Modules for Experiments in Stellar Astrophysics. We consider two cases for the CB disk formation in which it is fed by mass loss during single outburst or successive outbursts in the LMXB. We show that when taking reasonable values of the initial mass and the dissipating time of the disk, it is possible to explain the fast orbital shrinkage in the BHLMXBs without invoking high mass transfer rate.