Loading…

Long-term optical variability of the Be/X-ray binary GRO J2058+42

We investigate the long-term optical variability of the Be/X-ray binary GRO J2058+42 and the possible connection with periods of enhanced X-ray activity. We performed an optical spectroscopic and photometric analysis on data collected during about 18 years. We also present the first optical polarime...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2023-01
Main Authors: Reig, P, Tzouvanou, A, Blinov, D, Pantoulas, V
Format: Article
Language:English
Subjects:
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We investigate the long-term optical variability of the Be/X-ray binary GRO J2058+42 and the possible connection with periods of enhanced X-ray activity. We performed an optical spectroscopic and photometric analysis on data collected during about 18 years. We also present the first optical polarimetric observations of this source. The long-term optical light curves in the \(BVRI\) bands and the evolution of the H\(\alpha\) equivalent width display a sinusoidal pattern with maxima and minima that repeat every \(\sim\)9.5 years. The amplitude of this variability increases as the wavelength increases. The H\(\alpha\) equivalent width varied from about \(-0.3\) to \(-15\) \AA. We found a significant decrease in the polarization degree during the low optical state. The optical maxima occur near periods of enhanced X-ray activity and are followed by a drop in the optical emission. Unlike many other Be/X-ray binaries, GRO 2058+42 does not display \(V/R\) variability. The long-term optical variability agrees with the standard model of a Be/X-ray binary, where the circumstellar disk of the Be star grows and dissipates on timescales of 9--10 years. We find that the dissipation of the disk started after a major X-ray outburst. However, the stability of the H\(\alpha\) line shape as a double-peak profile and the lack of asymmetries suggest the absence of a warped disk and argue against the presence of a highly distorted disk during major X-ray outbursts.
ISSN:2331-8422
DOI:10.48550/arxiv.2301.09415