2008A&A...485..245G


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.15CEST11:23:22

2008A&A...485..245G - Astronomy and Astrophysics, volume 485, 245-256 (2008/7-1)

The qWR star HD 45166. II. Fundamental stellar parameters and evidence of a latitude-dependent wind.

GROH J.H., OLIVEIRA A.S. and STEINER J.E.

Abstract (from CDS):

The enigmatic object HD 45166 is a qWR star in a binary system with an orbital period of 1.596 day, and presents a rich emission-line spectrum in addition to absorption lines from the companion star (B7 V). As the system inclination is very small (i=0.77°±0.09°), HD 45166 is an ideal laboratory for wind-structure studies. The goal of the present paper is to determine the fundamental stellar and wind parameters of the qWR star.A radiative transfer model for the wind and photosphere of the qWR star was calculated using the non-LTE code CMFGEN. The wind asymmetry was also analyzed using a recently-developed version of CMFGEN to compute the emerging spectrum in two-dimensional geometry. The temporal-variance spectrum (TVS) was calculated to study the line-profile variations.Abundances and stellar and wind parameters of the qWR star were obtained. The qWR star has an effective temperature of Teff=50000±2000K, a luminosity of log(L/L)=3.75±0.08, and a corresponding photospheric radius of Rphot=1.00R. The star is helium-rich (N(H)/N(He)=2.0), while the CNO abundances are anomalous when compared either to solar values, to planetary nebulae, or to WR stars. The mass-loss rate is {dot}(M)=2.2x10–7M/yr, and the wind terminal velocity is v=425km/s. The comparison between the observed line profiles and models computed under different latitude-dependent wind densities strongly suggests the presence of an oblate wind density enhancement, with a density contrast of at least 8:1 from equator to pole. If a high velocity polar wind is present (∼1200km/s), the minimum density contrast is reduced to 4:1.The wind parameters determined are unusual when compared to O-type stars or to typical WR stars. While for WR stars v/vesc>1.5, in the case of HD 45166 it is much smaller (v/vesc=0.32). In addition, the efficiency of momentum transfer is η=0.74, which is at least 4 times smaller than in a typical WR. We find evidence for the presence of a wind compression zone, since the equatorial wind density is significantly higher than the polar wind. The TVS supports the presence of such a latitude-dependent wind and a variable absorption/scattering gas near the equator.

Abstract Copyright:

Journal keyword(s): stars: winds, outflows - stars: mass-loss - stars: fundamental parameters - binaries: spectroscopic - stars: individual: HD 45166 - stars: Wolf-Rayet

Simbad objects: 3

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Number of rows : 3

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 HD 45166 WR* 06 26 19.1550467867 +07 58 28.071465236 9.05 9.81 9.88     WRpec+B8V 70 1
2 V* V456 Car Ro* 07 42 23.7789286664 -56 08 45.658961827   7.17 7.25     B7V(p) 21 0
3 V* AG Car WR* 10 56 11.5779283438 -60 27 12.809532379 7.00 7.57 6.96 7.73   WN11h 590 0

    Equat.    Gal    SGal    Ecl

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2020.07.15-11:23:22

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