Massive Star Evolution in the Dwarf Galaxy I Zwicky 18
Abstract
From the study of luminous supernovae and long duration gamma ray bursts, as from observations of chemical anomalies in stars of galactic globular clusters, evidence has been accumulated that the evolution of massive stars proceeds very differently at low metallicity. Nearby irregular dwarf galaxies provide excellent laboratories for star formation, massive star evolution and chemical enrichment processes. One of the key objects is I Zwicky 18, which has a high SF rate and contains WR stars. We present a large grid of evolutionary tracks of massive, rotating single stars with an initial composition corresponding to that of I Zwicky 18 ( 1/50 Zo, or rather 1/10 Z_{SMC}).
The grid contains 300 evolutionary sequences of single stars in the mass range of 20-300 Mo, with initial rotational velocity between 0-600 km/s. We find a significant fraction of them following a Chemically Homogeneous Evolutionary path, evolving blueward in the HR diagram and becoming WR stars. We also derive Hydrogen and Helium ionizing fluxes emitted from our stars. Furthermore, our models have been compared with observations of I Zwicky 18, and we estimate the fractions of pair-instability supernovae and gamma ray bursts from our models.- Publication:
-
Massive Stars: From alpha to Omega
- Pub Date:
- June 2013
- Bibcode:
- 2013msao.confE.103S