PopII 1/2 stars: very high N14 and low O16 yields

Hirschi, Raphael

Abstract

Nine 20 Mo models were computed with metallicities ranging from solar, through $Z=10^{-5}$ ([Fe/H]=~-3.1) down to $Z=10^{-8}$ ([Fe/H]=~-6.1) and with initial rotational velocities between 0 and 600 km/s to study the impact of initial metallicity and rotational velocity. The very large amounts of N14 observed (~0.03 Mo) are only produced at $Z=10^{-8}$ (PopII 1/2). The strong dependence of the N14 yields on rotation and other parameters like the initial mass and metallicity may explain the large scatter in the observations of N14 abundance. The metallicity trends are best reproduced by the models with Omega_ini/Omega_c=~0.75, which is slightly above the mean observed value for OB solar metallicity stars. Indeed, in the model with Vini=600 km/s at $Z=10^{-8}$, the O16 yield is reduced due to strong mixing. This allows in particular to reproduce the upturn for C/O and a slightly decreasing [C/Fe], which are observed below [Fe/H]=~-3.

Citation

Hirschi, R. PopII 1/2 stars: very high N14 and low O16 yields. Presented at From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution

• Presentation Conference Type: Conference Paper (published)
• Conference Name: From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution
• Online Publication Date: Dec 23, 2005
• Publication Date: Dec 23, 2005
• Deposit Date: Jul 7, 2023
• Journal: Proceedings of the International Astronomical Union
• Print ISSN: 1743-9213
• Electronic ISSN: 1743-9221
• Publisher: Cambridge University Press
• Peer Reviewed: Peer Reviewed
• Volume: 1
• Issue: S228
• DOI: https://doi.org/10.1017/S1743921305005922
• Keywords: Astrophysics
• Public URL: https://keele-repository.worktribe.com/output/506793