Modeling the line variations from the wind-wind shock emissions of WR 30a

TL;DR

This paper models the spectral line variations in WR 30a caused by wind-wind interactions to determine orbital parameters and stellar masses in a binary Wolf-Rayet system.

Contribution

It introduces a model that accounts for wind-wind interaction effects on spectral lines, enabling better orbital and mass estimations for WR 30a.

Findings

Successfully fit spectral line excesses across orbital phases

Derived orbital eccentricity and inclination from spectral data

Constrained stellar masses using spectral modeling

Abstract

The study of Wolf-Rayet stars plays an important role in evolutionary theories of massive stars. Among these objects, ~ 20% are known to be in binary systems and can therefore be used for the mass determination of these stars. Most of these systems are not spatially resolved and spectral lines can be used to constrain the orbital parameters. However, part of the emission may originate in the interaction zone between the stellar winds, modifying the line profiles and thus challenging us to use different models to interpret them. In this work, we analyzed the HeII4686\AA + CIV4658\AA blended lines of WR30a (WO4+O5) assuming that part of the emission originate in the wind-wind interaction zone. In fact, this line presents a quiescent base profile, attributed to the WO wind, and a superposed excess, which varies with the orbital phase along the 4.6 day period. Under these assumptions, we were able to fit the excess spectral line profile and central velocity for all phases, except for the longest wavelengths, where a spectral line with constant velocity seems to be present. The fit parameters provide the eccentricity and inclination of the binary orbit, from which it is possible to constrain the stellar masses.