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The explosive yields produced by the first generation of core collapse supernovae and the chemical composition of extremely metal poor stars

May, 2002
30 pages
Published in:
  • Astrophys.J. 577 (2002) 281-294
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Abstract: (arXiv)
We present a detailed comparison between an extended set of elemental abundances observed in some of the most metal poor stars presently known and the ejecta produced by a generation of primordial core collapse supernovae. We used five stars which form our initial database and define a template ultra metal poor star which is then compared to the theoretical predictions. Our main findings are as follows: a) the fit to [Si/Mg] and [Ca/Mg] of these very metal poor stars seems to favor the presence of a rather large C abundance at the end of the central He burning: in a classical scenario in which the border of the convective core is strictly determined by the Schwarzschild criterion, such a large C abundance would imply a rather low C12(alpha,gamma)O16 reaction rate: b) a low C abundance left by the central He burning would imply a low [Al/Mg] (<-1.2 dex) independently on the initial mass of the exploding star while a rather large C abundance would produce such a low [Al/Mg] only for the most massive stellar model: c) at variance with current beliefs that it is difficult to interpret the observed overabundance of [Co/Fe], we find that a mildly large C abundance in the He exhausted core (well within the present range of uncertainty) easily and naturally allows a very good fit to [Co/Fe]: d) our yields allow a reasonable fit to 8 out of the 11 available elemental abundances: e) within the present grid of models it is not possible to find a good match of the remaining three elements, Ti, Cr and Ni (even for an arbitrary choice of the mass cut): f) the adoption of other yields available in the literature does not improve the fit: g) since no mass in our grid provides a satisfactory fit to these three elements, even an arbitrary choice of the initial mass function would not improve their fit.
Note:
  • 30 pages, 8 figures, 8 tables. Accepted for publication on ApJ