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.

published in New Astronomy, 2, pp. 245-250 (1997)

Abstract: Hipparcos parallax measurements give a distance to the Wolf-Rayet WC8+O spectroscopic binary γ2 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 γ2 Vel an interstellar extinction of Aν = 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 γ2 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, γ2 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 γ2 Vel for its mass, mass loss rate, luminosities at various wavelengths, and, briefly, its association with the Gum Nebula, are discussed.

DOI: 10.1016/S1384-1076(97)00018-3
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