Bibcode
Di Criscienzo, M.; Ventura, P.; D'Antona, F.; Dell'Agli, F.; Tailo, M.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 479, Issue 4, p.5325-5334
Fecha de publicación:
10
2018
Número de citas
7
Número de citas referidas
4
Descripción
Almost several decades after the discovery of the first multiple
populations in galactic globular clusters (GC), the debate on their
formation is still extremely current and NGC 2808 remains one of the
best benchmark to test any scenario for their origin and the evolution.
In this work, we focus on the chemical composition of stars belonging to
the extreme He-rich population populated by stars with the most extreme
abundance of Mg, Al, Na, O, and Si. We checked whether the most recent
measures are consistent with the asymptotic giant branch (AGB) yields of
stars of 6.5-8 M_{⊙}. These stars evolve on time scales of the order
of 40-60 Myr and eject matter strongly enriched in helium, owing to a
deep penetration of the surface convective zone down to regions touched
by CNO nucleosynthesis occurring after the core He-burning phase. Since
the big unknown of the AGB phase of massive stars is the mass-loss, we
propose a new approch that takes into account the effects of the
radiation pressure on dust particles. We show that this more realistic
description is able to reproduce the observed abundances of Mg, Al, Na,
and Si in these extreme stars. The large spread in the oxygen abundances
is explained by invoking deep mixing during the red giant branch phase.
It will be possible to check this work hypothesis as soon as the oxygen
measurements of the main-sequence stars of NGC 2808 will be available.
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