Core-halo structure of a chemically homogeneous massive star and bending of the zero-age main sequence

Mie Ishii, Munetaka Ueno, Mariko Kato

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

We have recalculated the 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 an extended radiative-envelope. With the core-halo structure, because a more massive star has a more extended envelope, the track of the upper zero-age main-sequence (ZAMS) curves redward in the H-R diagram at > 100 M(fisheye) (Z = 0.02), > 70 M(fisheye) (Z = 0.05), and > 15 M(fisheye) for helium ZAMS (X = 0, Z = 0.02). Therefore, the effective temperatures of very massive ZAMS stars are rather low: e.g., for a 200 M(fisheye) star, log Teff = 4.75 (Z = 0.004), 4.60 (Z = 0.02), 4.46 (Z = 0.05), and 4.32 (Z = 0.10). The effective temperatures of very luminous stars (> 120 M(fisheye)) found in the LMC, the SMC, and the Galaxy are discussed in relation to this metal dependence of a curving upper main-sequence.

Original languageEnglish
Pages (from-to)417-424
Number of pages8
JournalPublications of the Astronomical Society of Japan
Volume51
Issue number4
Publication statusPublished - 1999

Fingerprint

massive stars
halos
envelopes
stars
main sequence stars
opacity
helium
chemical composition
temperature
diagram
diagrams
galaxies
metal
curves
metals

Keywords

  • Stars: abundances
  • Stars: individual (the Pistol star)
  • Stars: interiors
  • Stars: massive
  • Stars: supergiants

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Core-halo structure of a chemically homogeneous massive star and bending of the zero-age main sequence. / Ishii, Mie; Ueno, Munetaka; Kato, Mariko.

In: Publications of the Astronomical Society of Japan, Vol. 51, No. 4, 1999, p. 417-424.

Research output: Contribution to journalArticle

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AU - Ishii, Mie

AU - Ueno, Munetaka

AU - Kato, Mariko

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N2 - We have recalculated the 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 an extended radiative-envelope. With the core-halo structure, because a more massive star has a more extended envelope, the track of the upper zero-age main-sequence (ZAMS) curves redward in the H-R diagram at > 100 M(fisheye) (Z = 0.02), > 70 M(fisheye) (Z = 0.05), and > 15 M(fisheye) for helium ZAMS (X = 0, Z = 0.02). Therefore, the effective temperatures of very massive ZAMS stars are rather low: e.g., for a 200 M(fisheye) star, log Teff = 4.75 (Z = 0.004), 4.60 (Z = 0.02), 4.46 (Z = 0.05), and 4.32 (Z = 0.10). The effective temperatures of very luminous stars (> 120 M(fisheye)) found in the LMC, the SMC, and the Galaxy are discussed in relation to this metal dependence of a curving upper main-sequence.

AB - We have recalculated the 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 an extended radiative-envelope. With the core-halo structure, because a more massive star has a more extended envelope, the track of the upper zero-age main-sequence (ZAMS) curves redward in the H-R diagram at > 100 M(fisheye) (Z = 0.02), > 70 M(fisheye) (Z = 0.05), and > 15 M(fisheye) for helium ZAMS (X = 0, Z = 0.02). Therefore, the effective temperatures of very massive ZAMS stars are rather low: e.g., for a 200 M(fisheye) star, log Teff = 4.75 (Z = 0.004), 4.60 (Z = 0.02), 4.46 (Z = 0.05), and 4.32 (Z = 0.10). The effective temperatures of very luminous stars (> 120 M(fisheye)) found in the LMC, the SMC, and the Galaxy are discussed in relation to this metal dependence of a curving upper main-sequence.

KW - Stars: abundances

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KW - Stars: supergiants

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