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Titolo:
THE FIELD HORIZONTAL-BRANCH B-TYPE STAR FEIGE-86
Autore:
BONIFACIO P; CASTELLI F; HACK M;
Indirizzi:
OSSERV ASTRON TRIESTE,VIA GB TIEPOLO 11 I-34131 TRIESTE ITALY SCH ADV INT STUDIES I-34014 TRIESTE ITALY CNR,GRP NAZL ASTRON,UNITA RIC TRIESTE TRIESTE ITALY UNIV TRIESTE,DIPARTIMENTO ASTRON TRIESTE ITALY
Titolo Testata:
Astronomy & Astrophysics. Supplement series
fascicolo: 3, volume: 110, anno: 1995,
pagine: 441 - 468
SICI:
0365-0138(1995)110:3<441:TFHBSF>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
CHEMICALLY PECULIAR STARS; LIGHT-ION SPECTRA; OSCILLATOR-STRENGTHS; HG-II; LIFETIME MEASUREMENTS; EFFECTIVE TEMPERATURE; STELLAR ATMOSPHERES; IUE SPECTRA; BEAM-FOIL; SDB STARS;
Keywords:
STARS, ABUNDANCES; STARS, CHEMICALLY PECULIAR; STARS, HORIZONTAL BRANCH; STARS, INDIVIDUAL, FEIGE 86; IOTA HER; 3 CEN A;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
123
Recensione:
Indirizzi per estratti:
Citazione:
P. Bonifacio et al., "THE FIELD HORIZONTAL-BRANCH B-TYPE STAR FEIGE-86", Astronomy & Astrophysics. Supplement series, 110(3), 1995, pp. 441-468

Abstract

IUE and visible high resolution spectra of the halo B-type star Feige86 are analyzed with the aim to get further insight into the atmospheric parameters and surface chemical composition of this Pop II star. The analysis is mostly based on the comparison of photometric, spectrophotometric, and spectroscopic observations with color indices, fluxes,and spectra computed by using Kurucz (1993a,b) codes, Kurucz, (1993a)LTE ATLAS9 model atmospheres, and Kurucz (1993b) line lists. The atmospheric parameters T-eff = 16430+/-250 K and log g = 4.20+/-0.02 are determined from the Stromgren photometry, visual energy distribution, and Palmer profiles. A colour excess E(B - V) between 0.02 and 0.08 magis deduced on the basis of both photometric and spectrophotometric data. Although the star's kinematics implies that it is a Pop II object (hence on the HE, given its spectral type) we find that its chemical composition is peculiar and unlike that of Pop II stars: We find that light elements (up to S) are underabundant, with the exception of P; iron-peak elements are solar or slightly overabundant; heavy elements, with the exception of Ge, are overabundant. In particular, we identify lines of Pt II, Au III, and Hg II consistent with overabundances from 3.5 to 4.0 dex. Several Mo III lines are also identified. He I Lines are carefully analyzed and the detection of the He-3 line at 667.8 nm is discussed. Some ultraviolet Lines arising from a lower level with energy close to 0 eV are affected by an additional slightly red-shifted absorption, probably of interstellar or circumstellar origin. We compare the spectra of Feige 86 with those of the normal Pop I B-type star iota Her and with those of the peculiar Pop I B-type star 3 Cen A, to which Feige 86 has always been associated. We show that the similaritywith 3 Cen A is marginal, because, although nearly all the same elements are affected by abundance anomalies, these occur in a different degree in the two stars, except for He, P, and Cu. No Mo, Pt, and Au lines have been identified in 3 Cen A. To what extent the different abundances of the two stars can be explained in terms of the different evolutionary history or of different atmospheric phenomena, such as diffusion, is still an open question.

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Documento generato il 19/09/20 alle ore 15:24:39