Massive stars: evolution with mass-loss. II. Mass-loss in early phases, and evolutionary status of the transition Wolf Rayet stars.
Abstract
Summary. Evolutionary sequences of stars with initial mass 20, 60, 100 M0 and Pop I chemical composition (X = 0.700, Z = 0.020) are computed from the main sequence to early stages of central He-burning. The mass-loss rate used in the computations follows the prescription of Barlow and Cohen (1976) derived from infrared observations of a selected sample of 0 stars and BA supergiants. The results are described in terms of evolutionary sequences, and effects of mass-loss on the internal structure of the models. A systematic comparison among all the available sources of theoretical models with mass-loss is performed to derive several fundamental calibration relationships. The comparison with the observations allows us to confine the mass-loss rates for 0 stars of the main sequence band within quite a narrow range, and provide constraints to the rates predicted by theories of mass-loss by radiation pressure. The problem of the evolutionary status of the transition WR stars is discussed to some extent, reaching the conclusion that quite presumably they are in the core Heburning phase. Although other alternatives cannot be excluded at the present time, the interpretation of the transition WR's as still burning hydrogen in the core seems rather unlikely. Key words: massive star evolution - mass-loss - WR stars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1979
- Bibcode:
- 1979A&A....74...62C
- Keywords:
-
- O Stars;
- Stellar Evolution;
- Stellar Mass Ejection;
- Supermassive Stars;
- Wolf-Rayet Stars;
- A Stars;
- B Stars;
- Chemical Composition;
- Helium;
- Hertzsprung-Russell Diagram;
- Hydrogen;
- Stellar Luminosity;
- Stellar Models;
- Stellar Structure;
- Astrophysics;
- Mass Loss:Massive Stars;
- Mass Loss:O Stars;
- Mass Loss:Stellar Models;
- Massive Stars:Evolution