Details

Autor(en) / Beteiligte

• Niemela, V. S.
• Gamen, R. C.
• Barbá, R. H.
• Fernández Lajús, E.
• Benaglia, P.
• Solivella, G. R.
• Reig, P.
• Coe, M. J.

Titel

The very massive X-ray bright binary system Wack 2134 (= WR 21a)

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2008-09, Vol.389 (3), p.1447-1452

Ort / Verlag

Oxford, UK: Blackwell Publishing Ltd

Erscheinungsjahr

2008

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• From the radial velocities of the N ivλ4058 and He iiλ4686 emission lines, and the N vλ4604-20 absorption lines, determined in digital spectra, we report the discovery that the X-ray bright emission line star Wack 2134 (= WR 21a) is a spectroscopic binary system with an orbital period of 31.673 ± 0.002 d. With this period, the N iv and He ii emission and N v absorption lines, which originate in the atmosphere of the primary component, define a rather eccentric binary orbit (e= 0.64 ± 0.03). The radial velocity variations of the N v absorptions have a lower amplitude than those of the He ii emission. Such a behaviour of the emission line radial velocities could be due to distortions produced by a superimposed absorption component from the companion. High-resolution echelle spectra observed during the quadrature phases of the binary show H and He ii absorptions of both components with a radial velocity difference of about 541 km s−1. From this difference, we infer quite high values of the minimum masses, of about 87 and 53 M⊙ for the primary and secondary components, respectively, if the radial velocity variations of the He ii emission represent the true orbit of the primary. No He i absorption lines are observed in our spectra. Thus, the secondary component in the Wack 2134 binary system appears to be an early O-type star. From the presence of H, He ii and N v absorptions, and N iv and C iv emissions, in the spectrum of the primary component, it most clearly resembles those of Of/WNLha-type stars.