Radius, rotational period and inclination of the Be stars in the Be/gamma-ray binaries MWC 148 and MWC 656

TL;DR

This study estimates the rotational periods, radii, and inclinations of Be stars in two gamma-ray binaries using TESS photometry and spectra, revealing their rotational characteristics and alignment with orbital planes.

Contribution

It provides the first detailed measurements of rotational parameters and inclinations for the Be stars in MWC 148 and MWC 656, using combined photometric and spectroscopic data.

Findings

MWC 148 has a rotational period of 1.10 days and an inclination of 40 degrees.

MWC 656 has a rotational period of 1.12 days and an inclination of 52 degrees.

The rotation of the MWC 656 donor is coplanar with its orbital plane.

Abstract

Using TESS photometry and Rozhen spectra of the Be/gamma-ray binaries MWC 148 and MWC 656, we estimate the projected rotational velocity ($ {v} \sin i$), the rotational period (P$_{\rm rot}$), radius (R$_{\rm 1}$), and inclination ($i$) of the mass donor. For MWC 148 we derive P$_{\rm rot} = 1.10 \pm 0.03$~d, R$_{\rm 1}= 9.2 \pm 0.5$~R$_\odot$, $i = 40^\circ \pm 2^\circ$, and $ {v} \sin i =272 \pm 5$~km~s$^{-1}$. For MWC 656 we obtain P$_{\rm rot} = 1.12 \pm 0.03$~d, R$_{\rm 1}= 8.8 \pm 0.5$~R$_\odot$, $i = 52^\circ \pm 3^\circ$, and $ {v} \sin i =313 \pm 3$~km~s$^{-1}$. For MWC 656 we also find that the rotation of the mass donor is coplanar with the orbital plane.