Circumstellar discs in X/gamma-ray binaries: first results from the Echelle spectrograph

TL;DR

This paper presents initial spectral observations of Be/X-ray and gamma-ray binaries using a new spectrograph, revealing disc parameters and intriguing similarities in emission lines, advancing understanding of circumstellar environments in these systems.

Contribution

First spectral data of these binaries with a new spectrograph, providing disc size estimates and identifying notable emission line features and similarities.

Findings

Disc sizes estimated from emission lines.

Deep disc penetration by the compact object in MWC 148.

Similarity between gamma-ray binary MWC 148 and gamma Cas in emission lines.

Abstract

Here we report our first spectral observations of Be/X-ray and gamma-ray binaries obtained with the new Echelle spectrograph of the National Astronomical Observatory Rozhen. For four objects (LSI+61303, gamma Cas, MWC 148, 4U 2206+54), we report the parameters and estimate the sizes of their circumstellar discs using different emission lines (H-alpha, H-beta, H-gamma, HeI and FeII). For MWC 148, we find that the compact object goes deeply through the disc. The flank inflections of H-alpha can be connected with inner ring formed at the periastron passage or radiation transfer effects. We point out an intriguing similarity between the optical emission lines of the $\gamma$-ray binary MWC 148 and the well known Be star $\gamma$ Cas.