Optical variabilities in Be/X-ray binary system:GRO J2058+42

TL;DR

This study analyzes long-term optical and spectroscopic data of the Be/X-ray binary GRO J2058+42, revealing non-radial pulsations and persistent disk features in the Be star, with the system currently in X-ray quiescence.

Contribution

It provides the first detailed optical variability and spectral analysis of GRO J2058+42, identifying non-radial pulsations and disk presence in the Be star.

Findings

Detected non-radial pulsation frequency at 2.404 1/day.

Observed persistent double-peaked H alpha emission lines.

System is currently in X-ray quiescent state.

Abstract

We present an analysis of long-term optical monitoring observations and optical spectroscopic observations of the counterpart to CXOU J205847.5+414637 (high mass X-ray binary system). We search for a variability in the light curve of Be star. We used differential magnitudes in the time series analysis. The variability search in the optical light curve was made by using different algorithms. The reduction and analysis of spectra were done by using MIDAS and its suitable packages. We have performed a frequency search which gave us the value 2.404 1/day. This value is attributed to the non-radial pulsation of Be star. H alpha emission line profiles always show double-peaked emissions with a mean equivalent width of 2.31 \pm 0.19 \AA ~and a peak separation of 516 \pm 45 km/s. This suggests that Be star disk is still present. CXOU J205847.5+414637 is in X-ray quiescent state.