Drastic Spectroscopic Variability of the Be/X-ray Binary A0535+262/V725 Tau during and after the 2009 Giant Outburst

TL;DR

This study presents detailed spectroscopic observations of the Be/X-ray binary A0535+262/V725 Tau during and after its 2009 giant outburst, revealing significant variability and complex disk structures.

Contribution

It provides new high-resolution spectroscopic data showing drastic variability and warped disk components during the outburst, advancing understanding of Be/X-ray binary dynamics.

Findings

Drastic variability in emission line profiles during outburst

Evidence of a warped circumstellar disk structure

Detection of a gas stream from the Be disk to the neutron star

Abstract

We report on high-dispersion optical spectroscopic observations of the Be/X-ray binary A0535+262/V725 Tau during the giant outburst in November/December 2009 and after it. The observed emission line profiles, reflecting the structure of the geometrically thin circumstellar envelope of the Be star (Be disk), show drastic variabilities and indicate the existence of a warped component. The enhanced blue shoulder seen after periastron passage implies the gas stream from a dense part of the Be disk to the neutron star.