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Title:
The orbital motion of gamma^2 Velorum
Authors:
Schmutz, W.; Schweickhardt, J.; Stahl, O.; Wolf, B.; Dumm, T.; Gang, Th.; Jankovics, I.; Kaufer, A.; Lehmann, H.; Mandel, H.; Peitz, J.; Rivinius, Th.
Affiliation:
AA(Institut fur Astronomie, ETH-Zentrum, CH-8092 Zurich, Switzerland), AB(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AC(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AD(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AE(Institut fur Astronomie, ETH-Zentrum, CH-8092 Zurich, Switzerland), AF(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany; STScI, 3700 San Martin Drive, Baltimore MD 21218, USA), AG(Gothard Astrophysical Observatory, H-9707 Szombathely, Hungary), AH(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AI(Thuringer Landessternwarte Tautenburg, Karl-Schwarzschild-Observatorium, D-07778 Tautenburg, Germany), AJ(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AK(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany), AL(Landessternwarte Heidelberg Konigstuhl, D-69117 Heidelberg, Germany)
Publication:
Astronomy and Astrophysics, v.328, p.219-228 (1997) (A&A Homepage)
Publication Date:
12/1997
Origin:
A&A
A&A Keywords:
BINARIES: SPECTROSCOPIC, STARS: EARLY-TYPE, STARS: FUNDAMENTAL PARAMETERS, STARS: INDIVIDUAL: GAMMA (2) VEL
Bibliographic Code:
1997A&A...328..219S

Abstract

We analyze the orbital motion of gamma (2) Velorum based on high resolution optical spectra obtained in 1995 and 1996. By combining our data with values from the literature we find a period P=78.53+/- 0.01 d. We determine radial velocity semi-amplitudes K_WR= 122+/- 2 \ifmmode kms^{-1} \else kms(-1) \fi and K_O= 38.4+/- 2 \ifmmode kms^{-1} \else kms(-1) \fi for the Wolf-Rayet star and the O star, respectively. The given errors are the standard deviations of the results from individual lines. The inclination of the system is i=65(deg) . This result is obtained by combining M_Osin(3) i from the orbital analysis with the mass M_O= 29 \ifmmode M_{\odot} \else Msun\fi , obtained from its luminosity and stellar evolution tracks. The mass of the Wolf-Rayet component is M_WR=9 \ifmmode M_{\odot} \else Msun\fi . Our O star velocity curve disagrees by 15 sigma from a previously published result. We have identified the reason for the disagreement in the failure to correct for the WR emission that affects the measurements of the absorption line centers. The correction could have introduced systematic errors that may be larger than the given precision of the amplitudes. However, we can set an upper limit of K_O<50 \ifmmode kms^{-1} \else kms(-1) \fi from uncorrected measurements. This yields an upper limit for the Wolf-Rayet mass of M_WR<12 \ifmmode M_{\odot} \else Msun\fi . We find systematic phase-shifts between the velocity curves of some emission lines. We also observe that some (but not all) emission lines deviate significantly in the 1995 data set from the line's orbital solution defined by the 1996 observations. These phenomena may indicate that the radial velocities of the emission lines could be subject to systematic distortions and that the errors of the orbital motion are larger than the internal precision given here.

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