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Paper: The He flash in Ultra Metal-Poor Low-Mass Stars
Volume: 293, 3D Stellar Evolution
Page: 314
Authors: Schlattl, H.; Salaris, M.; Cassisi, S.; Weiss, A.
Abstract: The currently favoured explanation for observed strongly C- and N-enriched ultra metal-poor stars ([Fe/H] < 3) is presented. At the tip of the RGB of extremely metal deficient stars, the He-flash driven convective zone is able to penetrate H-rich layers. The ingested H is immediately fusing with C to form N, releasing large amounts of energy. In the subsequent evolution the convective envelope merges with material enriched with C and N, but almost unaltered in the O abundance. While this scenario is potentially able to explain the occurrence of C- and N-enriched ultra metal-poor stars, it fails to reproduce the absolute values of [C/Fe] and [N/Fe]. Recent investigations show that the efficiency of mixing in the convective regions is one of the main uncertainty in these models, and that it plays a crucial role in determining the amount of C and N enrichment.
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