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The evolutionary status of WNL stars

Published online by Cambridge University Press:  07 August 2017

Paul A. Crowther ,
Linda J. Smith  and
D. John Hillier
Paul A. Crowther
Affiliation:
1 Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT U.K.
Linda J. Smith
Affiliation:
1 Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT U.K.
D. John Hillier
Affiliation:
2Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, U.S.A.

Abstract

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We discuss the evolutionary and mass loss implications of recent non-LTE analyses of late WN (WNL) stars in the Galaxy, LMC and M33 using the Wolf-Rayet standard model and address the observed dichotomy of WNL stars discussed by Moffat (1989). Individual subtypes belong to two distinct groups. We find that the single WNL+abs and WN7 stars evolve directly from very massive O stars (60–100 M⊙) with the former intimately related to extreme Of stars and found exclusively in the youngest clusters in our Galaxy. Conversely, the observational properties and chemistries of WN8-10 stars suggest that they are descended from lower initial mass progenitors (∼25–60 M⊙). These stars are either dormant LBVs (= WN9–10) or at a phase immediately after this stage (= WN8) although a previous RSG phase cannot be excluded. Included in this subgroup are the LMC and M33 Ofpe/WN9 stars, re-classified as WN9–10 since they appear to be genuine WN stars.

Keywords

stars: Wolf-Rayetatmospheresabundanceswindsmass-loss
Type
Session II - Model atmospheres for single Wolf-Rayet stars
Information
Symposium - International Astronomical Union , Volume 163: Wolf-Rayet Stars: Binaries, Colliding Winds, Evolution , 1995 , pp. 147 - 151
Copyright
Copyright © Kluwer 1995 

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