EAS Publications Series
Volume 71-72, 2015The Physics of Evolved Stars: A Conference Dedicated to the Memory of Olivier Chesneau
|Page(s)||339 - 342|
|Published online||01 December 2015|
E. Lagadec, F. Millour and T. Lanz (eds)
EAS Publications Series, 71–72 (2015) 339-342
Radioactive Clocks and Thermometer in S-type Stars
1 I.A.A., Université libre de Bruxelles (ULB), CP 226, 1050 Bruxelles, Belgium
2 LUPM, Université Montpellier, CNRS, 34095 Montpellier, France
Direct probes of the temporal evolution of stars are rare. We derive the time spent by S-type stars since the onset of the first thermal pulse, from the 99Tc – 99Ru and 93Zr – 93Nb chronometers. Zirconium and niobium abundances constrain as well the nucleosynthesis temperature, supporting 13C(α,n)16O as the s-process neutron source. Niobium abundances are used, for the first time, to efficiently separate stars with active nucleosynthesis from binary stars with fossil overabundances resulting from a previous mass transfer. The abundances of Tc, Nb, and Zr thus give access to the nucleosynthesis chronology and temperature, and provide a diagnostic of possible external pollution from a companion star.
© EAS, EDP Sciences, 2015
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