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Titolo:
NEW BERYLLIUM OBSERVATIONS IN LOW-METALLICITY STARS
Autore:
MOLARO P; BONIFACIO P; CASTELLI F; PASQUINI L;
Indirizzi:
OSSERV ASTRON TRIESTE,VIA GB TIEPOLO 11 I-34131 TRIESTE ITALY CNR,GNA I-34131 TRIESTE ITALY EUROPEAN SO OBSERV SANTIAGO 19 CHILE
Titolo Testata:
Astronomy and astrophysics
fascicolo: 2, volume: 319, anno: 1997,
pagine: 593 - 606
SICI:
0004-6361(1997)319:2<593:NBOILS>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
METAL-POOR STARS; INHOMOGENEOUS PRIMORDIAL NUCLEOSYNTHESIS; COSMIC-RAY NUCLEOSYNTHESIS; LITHIUM ISOTOPE RATIO; COOL DWARF STARS; SOLAR-TYPE STARS; F-TYPE STARS; HALO STARS; EARLY GALAXY; GALACTIC EVOLUTION;
Keywords:
STARS, ABUNDANCES; STARS, POPULATION II; GALAXY, EVOLUTION; COSMOLOGY, OBSERVATIONS; COSMIC RAYS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
85
Recensione:
Indirizzi per estratti:
Citazione:
P. Molaro et al., "NEW BERYLLIUM OBSERVATIONS IN LOW-METALLICITY STARS", Astronomy and astrophysics, 319(2), 1997, pp. 593-606

Abstract

We present observations of the Be II 313.0 nm resonance doubler in 14halo and old disk stars with metallicities ranging from [Fe/H]=-0.4 to approximate to-3.0 obtained with the CASPEC spectrograph of the ESO 3.6m telescope at a FWHM approximate to 8.6 kms(-1) resolution. Abundances are derived by means of the synthetic spectra technique employingKurucz (1993) atmospheric models, with enhanced alpha-elements and noovershooting. The derived abundances together with those available inliterature show that for -2.7 < [Fe/H] < -0.8 Be correlates linearly with iron [Be]proportional to 1.07(+/-0.08)[Fe/H], giving strength to previous results. However, a steeper correlation is still possible at metallicities lower than [Fe/H]<-1.4 with [Be]proportional to 1.6(+/-0.44)[Fe/H]. When iron is replaced with oxygen, Be is found tracking closely oxygen up to solar values, without signs of breaking in correspondence of the onset of the Galactic disk. No evidence of intrinsic dispersion is found, ought to the large errors involved in the Be abundance determinations, but for three stars (HD 106516, HD 3795, HD 211998)a significant upper limit in the Be abundance can be placed at approximate to 1 dex below the mean trend of the Be-Fe relation. For such stars non conventional mixing is required to explain Be depletion. Be observations can be used to discriminate strongly Li-depleted stars. These are the stars which show less Li than that expected by high energy cosmic rays production as deduced from Be observations. The available Be observations imply that some of the stars which contribute to the scatter in the Li-Fe diagram are Li-depleted stars. This result strongly supports the use of the upper envelope of the Li-Fe diagram to tracethe Li galactic evolution, and argues for a low value for the primordial Li against models which predict substantial Li depletion in halo and old disk stars.

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Documento generato il 19/09/20 alle ore 14:09:31