Publication Date:
2014-04-29
Description:
We present a new grid of stellar models and nucleosynthetic yields for super-AGB stars with metallicities Z = 0.001 and 0.0001, applicable for use within galactic chemical evolution models. Contrary to more metal-rich stars where hot bottom burning is the main driver of the surface composition, in these lower metallicity models the effect of third dredge-up and corrosive second dredge-up also have a strong impact on the yields. These metal-poor and very metal-poor super-AGB stars create large amounts of 4 He, 13 C, 14 N and 27 Al as well as the heavy magnesium isotopes 25 Mg and 26 Mg. There is a transition in yield trends at metallicity Z 0.001, below which we find positive yields of 12 C, 16 O, 15 N and 28 Si, which is not the case for higher metallicities. We explore the large uncertainties derived from wind prescriptions in super-AGB stars, finding 2 orders of magnitude difference in yields of 22 Ne, 23 Na, 24, 25, 26 Mg, 27 Al and our s-process proxy isotope g . We find inclusion of variable composition low-temperature molecular opacities is only critical for super-AGB stars of metallicities below Z 0.001. We analyse our results, and those in the literature, to address the question: Are super-AGB stars the polluters responsible for extreme population in the globular cluster NGC 2808? Our results, as well as those from previous studies, seem unable to satisfactorily match the extreme population in this globular cluster.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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