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News on the s process from young open clusters
- Publication Year :
- 2011
-
Abstract
- Recent spectroscopic measurements in open clusters younger than the Sun, with [Fe/H]>=0, showed that the abundances of neutron-rich elements have continued to increase in the Galaxy after the formation of the Sun, roughly maintaining a solar-like distribution. Such a trend requires neutron fluences larger than those so far assumed, as these last would have too few neutrons per iron seed. We suggest that the observed enhancements can be produced by nucleosynthesis in AGB stars of low mass (M < 1.5M\odot), if they release neutrons from the ^{13}C(��,n)^{16}O reaction in reservoirs larger by a factor of 4 than assumed in more massive AGBs (M > 1.5M\odot). Adopting such a stronger neutron source as a contributor to the abundances at the time of formation of the Sun, we show that this affects also the solar s-process distribution, so that its main component is well reproduced, without the need of assuming ad-hoc primary sources for the synthesis of s elements up to A \sim 130, contrary to suggestions from other works. The changes in the expected abundances that we find are primarily due to the following reasons. i) Enhancing the neutron source increases the efficiency of the s process, so that the ensuing stellar yields now mimic the solar distribution at a metallicity higher than before ([Fe/H]>=-0.1). ii) The age-metallicity relation is rather flat for several Gyr in that metallicity regime, so that those conditions remain stable and the enhanced nuclear yields, which are necessary to maintain a solar-like abundance pattern, can dominate the composition of the interstellar medium from which subsequent stars are formed.<br />Accepted for publication in The Astrophysical Journal
- Subjects :
- Metallicity
FOS: Physical sciences
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
Stellar evolution
Nucleosynthesis
Galactic evolution
Nuclear Astrophysics
Astrophysics::Solar and Stellar Astrophysics
Neutron
Solar and Stellar Astrophysics (astro-ph.SR)
Astrophysics::Galaxy Astrophysics
Physics
Astronomy and Astrophysics
Astrophysics - Astrophysics of Galaxies
Galaxy
Interstellar medium
Stars
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Astrophysics::Earth and Planetary Astrophysics
s-process
Open cluster
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....68f1f797fe76c261ed4db693df015089