• DOI:10.1051/0004-6361/201526617
• Corpus ID: 119275004

Low-metallicity massive single stars with rotation. Evolutionary models applicable to I Zwicky 18

@article{Szecsi2015LowmetallicityMS,
  title={Low-metallicity massive single stars with rotation. Evolutionary models applicable to I Zwicky 18},
  author={Dorottya Sz'ecsi and Norbert Langer and S.-C. Yoon and D. Sanyal and Selma E. de Mink and C. J. Evans and Tyl Dermine},
  journal={arXiv: Solar and Stellar Astrophysics},
  year={2015}
}

• D. Sz'ecsi, N. Langer, +4 authors T. Dermine
• Published 30 June 2015
• Physics
• arXiv: Solar and Stellar Astrophysics

Massive rotating single stars with an initial metal composition appropriate for the dwarf galaxy I Zw 18 ([Fe/H]=$-$1.7) are modelled during hydrogen burning for initial masses of 9-300 M$_{\odot}$ and rotational velocities of 0-900 km s$^{-1}$. Internal mixing processes in these models were calibrated based on an observed sample of OB-type stars in the Magellanic Clouds. Even moderately fast rotators, which may be abundant at this metallicity, are found to undergo efficient mixing induced by rotation resulting in quasi chemically-homogeneous evolution. These homogeneously-evolving models reach effective temperatures of up to 90 kK during core hydrogen burning. This, together with their moderate mass-loss rates, make them Transparent Wind Ultraviolet INtense stars (TWUIN star), and their expected numbers might explain the observed HeII ionizing photon flux in I Zw 18 and other low-metallicity HeII galaxies. Our slowly rotating stars above $\sim$80 M$_{\odot}$ evolve into late B- to M-type supergiants during core hydrogen burning, with visual magnitudes up to 19$^{\mathrm{m}}$ at the distance of I Zw 18. Both types of stars, TWUIN stars and luminous late-type supergiants, are only predicted at low metallicity. Massive star evolution at low metallicity is shown to differ qualitatively from that in metal-rich environments. Our grid can be used to interpret observations of local star-forming dwarf galaxies and high-redshift galaxies, as well as the metal-poor components of our Milky Way and its globular clusters.