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Titolo:
Evolution and nucleosynthesis of zero-metal intermediate-mass stars
Autore:
Chieffi, A; Dominguez, I; Limongi, M; Straniero, O;
Indirizzi:
CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy CNR Rome Italy I-00133CNR, Ist Astrofis Spaziale, I-00133 Rome, Italy Univ Granada, Dept Fis Teor & Cosmos, Granada 18071, Spain Univ Granada Granada Spain 18071 Fis Teor & Cosmos, Granada 18071, Spain Osservatorio Astron Roma, I-00040 Rome, Italy Osservatorio Astron Roma Rome Italy I-00040 on Roma, I-00040 Rome, Italy Osserv Astron Collurania Teramo, I-64100 Teramo, Italy Osserv Astron Collurania Teramo Teramo Italy I-64100 64100 Teramo, Italy
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 2, volume: 554, anno: 2001,
parte:, 1
pagine: 1159 - 1174
SICI:
0004-637X(20010629)554:2<1159:EANOZI>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
ASYMPTOTIC GIANT BRANCH; SYNTHETIC AGB EVOLUTION; POPULATION-III STARS; DREDGE-UP PHENOMENON; LYMAN-ALPHA FOREST; M-CIRCLE-DOT; POOR STARS; NITROGEN ABUNDANCES; STELLAR EVOLUTION; DEFICIENT STARS;
Keywords:
nuclear reactions, nucleosynthesis, abundances; stars : abundances; stars : evolution; stars : Population II;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
93
Recensione:
Indirizzi per estratti:
Indirizzo: Chieffi, A CNR, Ist Astrofis Spaziale, Via Fosso Cavaliere, I-00133 Rome, Italy CNR Via Fosso Cavaliere Rome Italy I-00133 I-00133 Rome, Italy
Citazione:
A. Chieffi et al., "Evolution and nucleosynthesis of zero-metal intermediate-mass stars", ASTROPHYS J, 554(2), 2001, pp. 1159-1174

Abstract

New stellar models with masses ranging between 4 and 8 M-circle dot, Z = 0, and Y = 0.23 are presented. The models have been evolved from the pre-main sequence up to the asymptotic giant branch (AGB). At variance with previous claims, we find that these updated stellar models do experience thermal pulses in the AGB phase. In particular, we show the following :1. In models with a mass larger than 6 M-circle dot, the second dredge-up is able to raise the CNO abundance in the envelope enough to allow a normalAGB evolution, in the sense that the thermal pulses and the third dredge-up take place.2. In models of lower mass, the efficiency of the CNO cycle in the H-burning shell is controlled by the carbon produced locally via the 3 alpha reactions. Nevertheless, the He-burning shell becomes thermally unstable after the early AGB. The expansion of the overlying layers induced by these weak He-shell flashes is not sufficient by itself to allow a deep penetration of the convective envelope. However, soon after the development of the maximumluminosity of the He flash is attained, a convective shell systematically forms at the base of the H-rich envelope. The innermost part of this convective shell probably overlaps the underlying C-rich region left by the intershell convection during the thermal pulse so that fresh carbon is dredged up in a hot H-rich environment and an H flash occurs. This flash favors the expansion of the outermost layers already started by the weak thermal pulse, and a deeper penetration of the convective envelope takes place. Then thecarbon abundance in the envelope rises to a level high enough that the further evolution of these models closely resembles that of more metal-rich AGB stars. These stars provide an important source of primary carbon and nitrogen, soa major revision of the chemical evolution in the early Galaxy is required. We suggest that the chemical imprint of these Population III stars could be found in the old and metal-poor components of the Milky Way.

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Documento generato il 04/12/20 alle ore 13:06:13