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15 February 2025
 
  » arxiv » astro-ph/0107172

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The 12C(alpha,gamma)16O Reaction Rate and the Evolution of Stars in the Mass Range 0.8 < M/M(sun) < 25
Gianluca Imbriani ; Marco Limongi ; Lucio Gialanella ; Filippo Terrasi ; Oscar Straniero ; Alessandro Chieffi (Istituto di Astrofisica Spaziale ;
Date 10 Jul 2001
Subject astro-ph
AffiliationDipartimento di Scienze Fisiche, Universitá Federico II di Napoli, and INFN), Marco Limongi (Osservatorio Astronomico di Roma), Lucio Gialanella (Dipartimento di Scienze Fisiche, Universitá Federico II di Napoli, and INFN), Filippo Terras
AbstractWe discuss the influence of the 12C(alpha,gamma)16O$ reaction rate on the central He burning of stars in the mass range 0.8-25 Msun, as well as its effects on the explosive yields of a 25 Msun star of solar chemical composition. We find that the central He burning is only marginally affected by a change in this cross section within the currently accepted uncertainty range. The only (important) quantity which varies significantly is the amount of C left by the He burning. Since the C(alpha,gamma)16O is efficient in a convective core, we have also analyzed the influence of the convective mixing in determining the final C abundance left by the central He burning. Our main finding is that the adopted mixing scheme does not influence the final C abundance provided the outer border of the convective core remains essentially fixed (in mass) when the central He abundance drops below about 0.1 dex by mass fraction; vice versa, even a slight shift (in mass) of the border of the convective core during the last part of the central He burning could appreciably alter the final C abundance. Hence, we stress that it is wiser to discuss the advanced evolutionary phases as a function of the C abundance left by the He burning rather than as a function of the efficiency of the 12C(alpha,gamma)16O reaction rate. Only a better knowledge of this cross section and/or the physics of the convective motions could help in removing the degeneracy between these two components. We also prolonged the evolution of the two 25 M_sun stellar models up to the core collapse and computed the final explosive yields.
Source arXiv, astro-ph/0107172
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