Volume 581, September 2015
|Number of page(s)||6|
|Section||Stellar structure and evolution|
|Published online||01 September 2015|
A new massive double-lined spectroscopic binary system: The Wolf-Rayet star WR 68a⋆
1 Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), CONICET, Avda. España 1512 Sur, J5402DSP, San Juan, Argentina
2 Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de San Juan, San Juan, Argentina
3 Instituto de Astrofísica de La Plata, CONICET, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, B1900FWA, La Plata, Argentina
4 Departamento de Física y Astronomía, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, Chile
5 Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile
Received: 26 August 2014
Accepted: 30 July 2015
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 M⊙ and 30 ± 4 M⊙, respectively. The equivalent width of the He ii λ4686 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.
Key words: binaries: spectroscopic / stars: Wolf-Rayet / stars: individual: WR 68a / stars: fundamental parameters
Table 2 is available in electronic form at http://www.aanda.org
© ESO, 2015
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