2 Velorum: orbital solution and fundamental parameter determination with SUSI

Abstract

The first complete orbital solution for the double-lined spectroscopic binary system γ 2 Velorum, obtained from measurements with the Sydney University Stellar Interferometer (SUSI), is presented. This system contains the closest example of a Wolf-Rayet star and the promise of full characterization of the basic properties of this exotic high-mass system has subjected it to intense study as an archetype for its class. In combination with the latest radial-velocity results, our orbital solution produces a distance of 336 +8 −7 pc, significantly more distant than the Hipparcos estimation. The ability to fully specify the orbital parameters has enabled us to significantly reduce uncertainties and our result is consistent with the Very Large Telescope Interferometer (VLTI) observational point, but not with their derived distance. Our new distance, which is an order of magnitude more precise than prior work, demands critical reassessment of all distance-dependent fundamental parameters of this important system. In particular, membership of the Vela OB2 association has been re-established, and the age and distance are also in good accord with the population of young stars reported by Pozzo et al. We determine the O-star primary component parameters to be M V (O) = −5.63 ± 0.10 mag, R(O) = 17 ± 2 R and M(O) = 28.5 ± 1.1 M . These values are consistent with calibrations found in the literature if a luminosity class of II-III is adopted. The parameters of the Wolf-Rayet (WR) component are M v (WR) = −4.33 ± 0.17 mag and M(WR) = 9.0 ± 0.6 M .

VEGA: Visible spEctroGraph and polArimeter for the CHARA array: principle and performance

“…Baselines ranging from 100 m to 300 m are mandatory to provide a detectable effect that could be measured accurately for the closest WR stars. SUSI ) and the VLTI (Glindemann et al 2004) have already carried out pioneering works in this field (North et al 2007;Millour et al 2007). …”

Modeling of the Vela complex including the Vela supernova remnant, the binary systemγ2 Velorum, and the Gum nebula

“…The current mass estimate of the WR star is M WR = 9.0 ± 0.6 M (North et al 2007). The mass of the O star is A154, page 4 of 8 M O = (28.5 ± 1.1) M (North et al 2007).…”

“…The mass of the O star is A154, page 4 of 8 M O = (28.5 ± 1.1) M (North et al 2007). The γ 2 Velorum system is an important source from the viewpoint of nuclear gamma-ray astronomy.…”

“…Millour et al (2007) give an interferometric estimate of the distance 368 +38 −13 pc. North et al (2007) estimate the distance to γ 2 Velorum to be 336 +8 −7 pc based on the orbital solution for the γ 2 Velorum binary obtained from the interferometric data. Finally, a revision of the analysis of HIPPARCOS data gives a distance of 334 +40 −32 pc van Leeuwen (2007).…”

Binaries and Multiple Systems Observed with the CHARA, NPOI, SUSI and VLTI Interferometric Eyes

“…This system was observed by Millour et al (2007) with the VLTI/AMBER and by North et al (2007) with the SUSI interferometer. Millour et al (2007) using a relatively restrained data set have set tight constraints on the geometrical parameters of the γ 2 Velorum orbit.…”