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Titolo:
Modeling lithium-rich carbon stars in the Large Magellanic Cloud: An independent distance indicator?
Autore:
Ventura, P; DAntona, F; Mazzitelli, I;
Indirizzi:
Osservatorio Astron Roma, I-00040 Monte Porzio Catone, Italy Osservatorio Astron Roma Monte Porzio Catone Italy I-00040 Catone, 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: 524, anno: 1999,
parte:, 2
pagine: L111 - L114
SICI:
0004-637X(19991020)524:2<L111:MLCSIT>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
INTERMEDIATE-MASS STARS; GIANT BRANCH STARS; RED GIANTS; STELLAR EVOLUTION; S-PROCESS; CONVECTION; OVERSHOOT; AGB;
Keywords:
stars : AGB and post-AGB; stars : carbon; stars : evolution;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
20
Recensione:
Indirizzi per estratti:
Indirizzo: Ventura, P Osservatorio Astron Roma, Via Frascati 33, I-00040 Monte PorzioCatone, Italy Osservatorio Astron Roma Via Frascati 33 Monte Porzio Catone Italy I-00040
Citazione:
P. Ventura et al., "Modeling lithium-rich carbon stars in the Large Magellanic Cloud: An independent distance indicator?", ASTROPHYS J, 524(2), 1999, pp. L111-L114

Abstract

We present the first quantitative computations explaining the presence in the Large Magellanic Cloud of some asymptotic giant branch stars that are both lithium-rich stars and carbon stars (surface C/O > 1). A self-consistent description of time-dependent mixing, overshooting, and nuclear burning was required. The products of nucleosynthesis at the stellar surface turn out to be very sensitive to the temperature at the base of the outer convective envelope (T-bce) during the quiescent phase of hydrogen burning. Lithiumproduction is obtained for T-bce greater than or equal to 4 x 10(7) K (hotbottom burning), but T-bce greater than or equal to 6.5 x 107 K is necessary in order to cycle into nitrogen the carbon that was previously convectedto the stellar surface by the third dredge-up. Therefore, Li-rich C stars can occur for T-bce's in this small range of temperatures. We then identifya possible (narrow) range of masses and luminosities for this peculiar evolutionary stage. Comparison of these models with the luminosities of the few Li-rich C stars in the LMC provides an independent distance indicator (within similar to 0.25 mag) for the LMC. The present data and models are consistent with (m - M)(o) similar to 18.7, but a better determination would bepossible by refining the observations and the theoretical models.

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Documento generato il 29/11/20 alle ore 15:32:54