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

COLLADO, A.; GAMEN, R.; BARBÁ, R. H.; MORRELL, N.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2015 vol. 581

0004-6361

Double-lined spectroscopic binary systems, containing a Wolf-Rayet and amassive O-type star, are key objects for the study of massive starevolution because these kinds of systems allow the determination offundamental astrophysical parameters of their components. We haveperformed spectroscopic observations of the star WR 68a as part of adedicated monitoring program of WR stars to discover new binary systems.We identified spectral lines of the two components of the system anddisentangled the spectra. We measured the radial velocities in theseparated spectra and determined the orbital solution. We discoveredthat WR 68a is a double-lined spectroscopic binary with an orbitalperiod of 5.2207 days, very small or null eccentricity, and inclinationranging between 75 and 85 deg. We classified the binary components asWN6 and O5.5-6. The WN star is less massive than the O-type star withminimum masses of 15 ± 5 M⊙ and 30 ± 4M⊙, respectively. The equivalent width of the He iiλ4686 emission line shows variations with the orbital phase,presenting a minimum when the WN star is in front of the system. Thelight curve constructed from available photometric data presents minimain both conjunctions of the system.