Wolf-Rayet stars as a diagnostic of internal mixing processes in massive mass losing stars

Abstract

• • The convective core size in very massive H-burning stars may well be approximated by the Schwarzschild criterion.

• • In sufficiently massive stars the extension of the intermediate convection zone exceeds 10–20 M _⊙.

• • The convective core size in massive He-burning stars can hardly be restricted by observations. However, the absence of very massive WC stars is consistent with the case of no overshooting at all.

Theoretical evolutionary sequences taking into account the above points lead to the following scheme, which is basically consistent with recent papers of Schild and Maeder (1984), Langer (1987), and Doom (1987): most massive stars → WNL → SN very massive stars → WNL → WCE → SN massive stars → WNE → WCL → SN less massive stars → WNE → SN.