The Hipparcos distance determination of the Wolf-Rayet system γ2 Velorum (WC8+O) and its ramifications

• Published in: New astronomy Vol. 2; no. 3; pp. 245 - 250
• Main Authors: van der Hucht, K.A., Schrijver, H., Stenholm, B., Lundström, I., Moffat, A.F.J., Marchenko, S.V., Seggewiss, W., Setia Gunawan, D.Y.A., Sutantyo, W., van den Heuvel, E.P.J., De Cuyper, J.-P., Gómez, A.E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.1997
• Subjects: Binaries spectroscopic; Stars distances; Stars fundamental parameters; Stars individual γ2 Vel; Stars mass loss; Stars Wolf-Rayet; Stars distances; Stars mass loss; 97.10.Nf; 97.10.Vm; 97.30.Eh; Stars individual γ 2 Vel; Stars Wolf-Rayet; Stars fundamental parameters; 95.10.Jk; 97.80.Fk; Binaries spectroscopic
• ISSN: 1384-1076; 1384-1092
• DOI: 10.1016/S1384-1076(97)00018-3

Hipparcos parallax measurements give a distance to the Wolf-Rayet WC8+O spectroscopic binary γ 2 Vel of d = 258 −31 +41 pc and a distance to the O4I(n)f star ξ Pup of d = 429 −77 +120pc. Adopting for γ 2 Vel an interstellar extinction of A ν = 0.06 mag, this implies an absolute magnitude M ν = − 5.4 mag for the WC8+O binary system. Given that the binary components have a magnitude difference Δm = 1.4 mag, we derive M ν (WC8) = −3.7 and M v (O) = −5.0 mag. The latter indicates an O8.5III rather than an O9I companion, as was adopted during the last 25 years. Apparently γ 2 Vel is not a member of, but a foreground object before the open cluster Cr 173 and the association Vel OB2. Given a re-assessment of the distance of the Gum Nebula, γ 2 Vel is still one of its ionizing sources, while ξ Pup appears to be located at the back of the Gum Nebula. Consequences of the Hipparcos distance determination of γ 2 Vel for its mass, mass loss rate, luminosities at various wavelengths, and, briefly, its association with the Gum Nebula, are discussed.