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Titolo:
The C-12(alpha,gamma)O-16 reaction rate and the evolution of stars in the mass range 0.8 <= M/M-circle dot <= 25
Autore:
Imbriani, G; Limongi, M; Gialanella, L; Terrasi, F; Straniero, O; Chieffi, A;
Indirizzi:
Univ Naples Federico II, Dipartimento Sci Fis, Naples, Italy Univ Naples Federico II Naples Italy ipartimento Sci Fis, Naples, Italy Ist Nazl Fis Nucl, I-80125 Naples, Italy Ist Nazl Fis Nucl Naples Italy I-80125 l Fis Nucl, I-80125 Naples, Italy Osservatorio Astron Napoli, I-80131 Naples, Italy Osservatorio Astron Napoli Naples Italy I-80131 i, I-80131 Naples, Italy Osserv Astron Roma, I-00040 Monte Porzio Catone, Italy Osserv Astron RomaMonte Porzio Catone Italy I-00040 orzio Catone, Italy Univ Naples 2, Dipartimento Sci Ambientali, Naples, Italy Univ Naples 2 Naples Italy , Dipartimento Sci Ambientali, Naples, Italy Osservatorio Astron Collurania, I-64100 Teramo, Italy Osservatorio Astron Collurania Teramo Italy I-64100 -64100 Teramo, Italy CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy CNR Rome Italy I-00133CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 2, volume: 558, anno: 2001,
parte:, 1
pagine: 903 - 915
SICI:
0004-637X(20010910)558:2<903:TCRRAT>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
THERMONUCLEAR REACTION-RATES; HORIZONTAL-BRANCH STARS; GLOBULAR-CLUSTER STARS; CROSS-SECTION; WHITE-DWARFS; STELLAR ENERGIES; MODELS; HELIUM; NUCLEOSYNTHESIS; ISOCHRONES;
Keywords:
nuclear reactions, nucleosynthesis, abundances; stars : evolution; stars : interiors; supernovae : general;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Imbriani, G Univ Naples Federico II, Dipartimento Sci Fis, Naples, Italy Univ Naples Federico II Naples Italy Sci Fis, Naples, Italy
Citazione:
G. Imbriani et al., "The C-12(alpha,gamma)O-16 reaction rate and the evolution of stars in the mass range 0.8 <= M/M-circle dot <= 25", ASTROPHYS J, 558(2), 2001, pp. 903-915

Abstract

We discuss the influence of the C-12(alpha, gamma)O-16 reaction rate on the central He burning of stars in the mass range 0.8-25 M., as well as its effects on the explosive yields of a 25 M. 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 that varies significantly is the amount of C left by the He burning. Since the C-12(alpha, gamma)O-16 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. Ourmain 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 similar or equal to0.1 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 centralHe burning could appreciably alter the final C abundance. Hence, we stressthat it is wiser to discuss the advanced evolutionary phases as a functionof the C abundance left by the He burning rather than as a function of theefficiency of the C-12(alpha, gamma)O-16 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. stellar models up to the core collapse and computed the Dnal explosive yields. Our main results are that the intermediate-light elements, Ne, Na, Mg, and Al (which are produced in the Cconvective shell), scale directly with the C abundance left by the He burning because they depend directly on the amount of available fuel (i.e., C and/or Ne). All the elements whose final yields are produced by any of the four explosive burnings (complete explosive Si burning, incomplete explosiveSi burning, explosive O burning, and explosive Ne burning) scale inverselywith the C abundance left by the He burning because the mass-radius relation in the deep interior of a star steepens as the C abundance reduces. We confirm previous findings according to which a low C abundance (similar or equal to0.2 dex by mass fraction) is required to obtain yields with a scaledsolar distribution.

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Documento generato il 04/12/20 alle ore 13:09:44