2008A&A...482..945G


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.29CET06:12:28

2008A&A...482..945G - Astronomy and Astrophysics, volume 482, 945-960 (2008/5-2)

Mass loss from late-type WN stars and its Z-dependence. Very massive stars approaching the Eddington limit.

GRAEFENER G. and HAMANN W.-R.

Abstract (from CDS):

The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to the formation of long-duration Gamma Ray Bursts (GRBs) and the yields from early stellar generations. However, the mechanism of formation of WR-type stellar winds is still under debate. We present the first fully self-consistent atmosphere/wind models for late-type WN stars. We investigate the mechanisms leading to their strong mass loss, and examine the dependence on stellar parameters, in particular on the metallicity Z. We perform a systematic parameter study of the mass loss from WNL stars, utilizing a new generation of hydrodynamic non-LTE model atmospheres. The models include a self-consistent treatment of the wind hydrodynamics, and take Fe-group line-blanketing and clumping into account. They thus allow a realistic modelling of the expanding atmospheres of WR stars. The results are verified by comparison with observed WNL spectra. We identify WNL stars as very massive stars close to the Eddington limit, potentially still in the phase of central H-burning. Due to their high L/M ratios, these stars develop optically thick, radiatively driven winds. These winds show qualitatively different properties than the thin winds of OB stars. The resultant mass loss depends strongly on Z, but also on the Eddington factor Γe, and the stellar temperature T*. We combine our results in a parametrized mass loss recipe for WNL stars. According to our present model computations, stars close to the Eddington limit tend to form strong WR-type winds, even at very low Z. Our models thus predict an efficient mass loss mechanism for low metallicity stars. For extremely metal-poor stars, we find that the self-enrichment with primary nitrogen can drive WR-type mass loss. These first WN stars might play an important role in the enrichment of the early ISM with freshly produced nitrogen.

Abstract Copyright:

Journal keyword(s): stars: Wolf-Rayet - stars: early-type - stars: atmospheres - stars: mass-loss - stars: winds, outflows - stars: individual: WR22

Simbad objects: 10

goto Full paper

goto View the reference in ADS

Number of rows : 10

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 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14559 1
2 RMC 136a Cl* 05 38 43.3 -69 06 08           ~ 142 2
3 Ass Car OB 1 As* 10 38 -59.0           ~ 140 0
4 HD 92740 WR* 10 41 17.5154230335 -59 40 36.897706569 5.68 6.50 6.42 7.38   WN7h+O9III-V 376 0
5 HD 93162 WR* 10 44 10.3888220947 -59 43 11.105959983 7.90 8.55 8.80 8.66   O2.5If*/WN6+OB 330 1
6 * eta Car Em* 10 45 03.5455050 -59 41 03.951060 6.37 7.034 6.21 4.90 4.41 OBepec 2174 0
7 Cl Trumpler 16 OpC 10 45 10 -59 43.0   5.35 5.0     ~ 421 0
8 HD 96548 WR* 11 06 17.2033098417 -65 30 35.237611013 7.10 7.80 7.70 8.49   WN8h 384 0
9 NAME Arches Cluster Cl* 17 45 50.5 -28 49 28           ~ 621 0
10 HD 165763 WR* 18 08 28.4691215895 -21 15 11.182287576 7.16 7.54 7.82 8.55   WC6 263 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2008A&A...482..945G and select 'bookmark this link' or equivalent in the popup menu


2020.02.29-06:12:28

© Université de Strasbourg/CNRS

    • Contact