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Core-Halo Structure of a Chemically Homogeneous Massive Star and Bending of the Zero-Age Main Sequence

1999; Oxford University Press; Volume: 51; Issue: 4 Linguagem: Inglês

10.1093/pasj/51.4.417

ISSN

2053-051X

Autores

Mie Ishii, Munetaka Ueno, Mariko Kato,

Tópico(s)

Astrophysics and Star Formation Studies

Resumo

We have recalculated interior structure of very massive stars of uniform chemical composition with the OPAL opacity. Very massive stars are found to develop a core-halo structure with a extended radiative-envelope. With the core-halo structure, a more massive star has a more extended envelope, then the track of upper zero-age main-sequence (ZAMS) curves redward in the H-R diagram at > 100 M_sol (Z=0.02), >70 M_sol (Z=0.05), and > 15 M_sol for helium ZAMS (X=0., Z=0.02). Therefore, effective temperature of a very massive ZAMS star is rather low: e.g., for the 200 M_sol star, log T_eff=4.75 (Z=0.004), 4.60 (Z=0.02), 4.46 (Z=0.05), and 4.32 (Z=0.10). Effective temperatures of very luminous stars (> 120 M_sol) found in the LMC, the SMC, and the Galaxy are discussed in relation with this metal dependence of curving upper main-sequence.

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