The new Wolf-Rayet binary system WR62a

TL;DR

This paper confirms WR62a as a binary system with a WN5 primary and an O-type secondary, revealing their orbital period, mass estimates, and spectral variations through spectroscopic and photometric analysis.

Contribution

First detailed spectroscopic and photometric study identifying WR62a as a double-lined binary with specific orbital and stellar parameters.

Findings

WR62a is a double-lined spectroscopic binary.

Orbital period is 9.1447 days.

Masses range between 21-23 Mo for WN star and 39-42 Mo for O star.

Abstract

Context. A significant number of the Wolf-Rayet stars seem to be binary or multiple systems, but the nature of many of them is still unknown. Dedicated monitoring of WR stars favours the discovery of new systems. Aims. We explore the possibility that WR62a is a binary system. Methods. We analysed the spectra of WR62a, obtained between 2002 and 2010, to look for radial-velocity and spectral variations that would suggest there is a binary component. We searched for periodicities in the measured radial velocities and determined orbital solutions. A period search was also performed on the "All-Sky Automated Survey" photometry. Results. We find that WR62a is a double-lined spectroscopic binary with a WN5 primary star and an O 5.5-6 type secondary component in orbit with a period of 9.1447 d. The minimum masses range between 21 and 23 Mo for the WN star and between 39 and 42 Mo for the O-type star, thus indicating that the WN star is less massive than the O-type component. We detect a phase shift in the radial-velocity curve of the He II 4686 emission line relative to the other emission line curves. The equivalent width of this emission line shows a minimum value when the WN star passes in front of the system. The analysis of the ASAS photometry confirms the spectroscopic periodicity, presenting a minimum at the same phase.