A new massive double-lined spectroscopic binary system: The Wolf-Rayet star WR 68a

TL;DR

This paper reports the discovery and detailed orbital analysis of a new massive double-lined spectroscopic binary system, WR 68a, consisting of a Wolf-Rayet star and an O-type star, with implications for understanding massive star evolution.

Contribution

The study presents the first spectroscopic orbital solution for WR 68a, identifying its components and their properties, and analyzing spectral and photometric variations.

Findings

WR 68a is a double-lined spectroscopic binary with a 5.2207-day period.

The system contains a WN6 Wolf-Rayet star and an O5.5-6 star.

The WN star is less massive, with minimum mass 15 +/- 5 Msun, compared to 30 +/- 4 Msun for the O star.

Abstract

Double-lined spectroscopic binary systems, containing a Wolf-Rayet and a massive O-type star, are key objects for the study of massive star evolution because these kinds of systems allow the determination of fundamental astrophysical parameters of their components. We have performed spectroscopic observations of the star WR 68a as part of a dedicated monitoring program of WR stars to discover new binary systems. We identified spectral lines of the two components of the system and disentangled the spectra. We measured the radial velocities in the separated spectra and determined the orbital solution. We discovered that WR 68a is a double- lined spectroscopic binary with an orbital period of 5.2207 days, very small or null eccentricity, and inclination ranging between 75 and 85 deg. We classified the binary components as WN6 and O5.5-6. The WN star is less massive than the O-type star with minimum masses of 15 +/- 5 Msun and 30 +/- 4 Msun , respectively. The equivalent width of the He II {\lambda}4686 emission line shows variations with the orbital phase, presenting a minimum when the WN star is in front of the system. The light curve constructed from available photometric data presents minima in both conjunctions of the system