A&A 448, L37-L41 (2006)
On the origin of the high helium sequence in
CentauriA. Maeder and G. Meynet
Geneva Observatory, 1290 Sauverny, Switzerland
(Received 19 December 2005 / Accepted 21 January 2006 )
The blue Main Sequence (bMS) of Cen implies a ratio of helium to metal enrichment
, which is a major enigma.
We show that rotating models of low metallicity stars, which account for the anomalous
abundance ratios of extremely metal poor stars, are also useful for understanding the very high
ratio in Cen. Models of massive stars
with moderate initial rotation velocities
produce stellar winds with large He- and N-excesses, but
without the large C- (and O-) excesses made by very fast rotation, in agreement with the observed chemical abundance ratios in Cen.
It is still uncertain whether the abundance peculiarities of
Cen result from the fact
that the high velocity contributions of supernovae escaped the globular cluster, usually considered as a tidally stripped core of a dwarf galaxy. Another possibility is a general dominance of wind ejecta at very low Z
, due to the formation of black holes. Some abundance and isotopic ratios like
may allow us to further discriminate between these scenarios and between the AGB and massive star contributions.
© ESO 2006
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