Characterisation of Hβ spectra from EXO 051910+3737.7 X-rays binaries

We investigate the spectral characteristics of the Be/X-ray binary system, EXO 051910+3737.7, in which Be/X-ray systems are the largest sub-class of high-mass X-ray binaries. Spectroscopic observations are taken by the Thai National Telescope (TNT) with a Medium-RESolution spectrograph (MRES) instrument for seven nights spanning from 2020 to 2021. Our primary focus is directed towards the analysis of two Balmer lines, namely Hα and Hβ, given that Be stars typically exhibit emission features in at least one of these hydrogen Balmer lines during certain phases. Our observations reveal split Balmer emission lines throughout the entire duration of our monitoring. Double Gaussian profiles were employed for line fitting to characterize these lines. The presence of double peaks in the Balmer lines indicates the presence of asymmetries within the circumstellar disc. We then analyze V/R variations and the changes in Hβ spectra. Our analysis of V/R variation which Violet (V) and Red (R) peak intensity components, revealed rapid fluctuations occurring within a single day, although determining the precise periodicity was constrained by instrumental limitations and the duration of observability. Furthermore, employing observed the wavelength differences (Δλ) in conjunction with typical Be star parameters allowed us to estimate the radius (rβ) of the Hβ emitting envelope. The average value was calculated to be 2.585r∗, with a standard deviation of 0.050r∗. HIGHLIGHTS EXO 051010+3737.7 spectral line profiles were observed using the TNO/MRES instrument, revealing absorption lines for He I, and double-peak emission lines for Hand H. Rapid V/R variations were detected within a single day. The radius of the Hemitting envelope use the observed  and typical Be star parameters. GRAPHICAL ABSTRACT