Depending on its initial mass, a star may end as a white dwarf or explode as a
supernova. The dividing boundary is however ill-defined, and depends on the
treatment of convection and mass loss. Asymptotic Giant Branch (AGB) stars do
not ignite carbon and end up as carbon-oxygen white dwarfs. But if mass loss is
weak the core may grow to reach the Chandrasekhar mass limit and explode as a
thermonuclear supernova. Slightly more massive stars ignite carbon and, like
AGB stars, they also undergo thermal pulses. These super-AGB stars may leave an
oxygen-neon white dwarf, but their fate is unclear. They will either produce an
oxygen-neon white dwarf or explode in an electron capture supernova and produce
a neutron star. Red supergiants of initial mass as low as 8 solar masses have
now been identified directly as the progenitors of type IIP supernovae. With
the Initial Mass Function favouring the low mass end of the supernova
progenitors, massive AGB stars contributing to nitrogen enrichment on
timescales as short as tens of million years, and both supernovae and AGB stars
competing for the title of most prolific dust factory in the early Universe, it
is crucial to gain a better understanding of the boundary between massive AGB
stars and the progenitors of core-collapse supernovae.
Organised by
Jacco van Loon
(Keele University)
and
John Eldridge
(Cambridge University)
on behalf of the UK Working
Group on Evolved Stars
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