منابع مشابه
CNO in Low- and Zero-Metallicity AGB Stars
The oldest stars hide information about the chemical evolution of the early universe. In this contect new models of the AGB stellar evolution phase at very low and zero metallicity are presented. Due to the deficiency or absence of CNO catalytic material hydrogen burning operates at significantly higher temperatures than in stars of higher metallicity. As a result convective mixing plays a very...
متن کاملZero-Metallicity Stars and the Effects of the First Stars on Reionization.
We present stellar structure and atmosphere models of metal-free stars and examine them from a cosmological point of view. Metal-free stars exhibit high effective temperatures and small sizes relative to metal-enriched stars of equal mass. These unique physical characteristics enhance the ionizing photon production by metal-free stars, particularly in the He ii (hnu>/=4 ryd) continuum. The star...
متن کاملNew beryllium observations in low-metallicity stars
We present observations of the Be II 313.0 nm resonance doublet in 14 halo and old disk stars with metallicities ranging from [Fe/H]=-0.4 to≈-3.0 obtained with the CASPEC spectrograph of the ESO 3.6m telescope at a FWHM≈ 8.6 kms−1 resolution. Abundances are derived bymeans of the synthetic spectra technique employing Kurucz (1993) atmospheric models, with enhanced α-elements and no overshooting...
متن کاملs-Process Nucleosynthesis in Low-Metallicity Stars
Nobuyuki IWAMOTO1,∗, Toshitaka KAJINO, Grant J. MATHEWS, Masayuki Y. FUJIMOTO and Wako AOKI National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan The Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Center for Astrophysics, Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA Department of Physics, Hokkaido Univ...
متن کاملMass loss and very low-metallicity stars
Mass loss plays a dominant role in the evolution of massive stars at solar metallicity. After discussing different mass loss mechanisms and their metallicity dependence, we present the possibility of strong mass loss at very low metallicity. Our models at Z = 10−8 show that stars more massive than about 60 M⊙ may lose a significant fraction of their initial mass in the red supergiant phase. Thi...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2003
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361:20021756