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Titolo:
THE BINARY-SYSTEM ALPHA-VIR (SPICA) - FUN DAMENTAL PARAMETERS OF THE COMPONENTS AND DIFFERENCES IN THEIR HELIUM ABUNDANCE
Autore:
LYUBIMKOV LS; RACHKOVSKAYA TM; ROSTOPCHIN SI; TARASOV AE;
Indirizzi:
CRIMEAN ASTROPHYS OBSERV NAUCHNYI 334413 UKRAINE
Titolo Testata:
ASTRONOMICESKIJ ZURNAL
fascicolo: 2, volume: 72, anno: 1995,
pagine: 212 - 221
SICI:
0004-6299(1995)72:2<212:TBA
Fonte:
ISI
Lingua:
RUS
Soggetto:
EARLY-TYPE STARS; MODEL ATMOSPHERES; STELLAR MODELS; B-STARS; NITROGEN;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
33
Recensione:
Indirizzi per estratti:
Citazione:
L.S. Lyubimkov et al., "THE BINARY-SYSTEM ALPHA-VIR (SPICA) - FUN DAMENTAL PARAMETERS OF THE COMPONENTS AND DIFFERENCES IN THEIR HELIUM ABUNDANCE", ASTRONOM ZH, 72(2), 1995, pp. 212-221

Abstract

Spectra with high resolution and large signal-to-noise ratio were used to measure the equivalent widths and radial velocities of the components in the binary system alpha Vir (Spica). Based on previously developed techniques, their fundamental parameters were studied, The following effective temperatures and surface gravities were adopted: T-eff =24700 +/- 500 K and logg = 3.7 +/- 0.1 for the primary component (star A); T-eff = 20 800 +/- 1500 K and logg = 4.2 +/- 0.2 for the secondary component (star B). On the basis of non-LTE analysis of seven HeI lines, the following average helium abundances were derived: He/H = 0.22 +/- 0.04 for component A, and He/H = 0.10 +/- 0.02 for component B. A comparison with evolutionary tracks showed the more massive primary component (M(A) approximate to 11M.) to be near completion of the main-sequence (MS) phase, while the less massive secondary component (M(B)approximate to 7M.) is still at the beginning of this phase. Thus, the difference in helium abundance between components A and B is consistent with the earlier made suggestion of mixing at the MS stage; it is explained by the fact that the atmosphere of star A during its MS lifetime managed to be enriched by the CNO-cycled products. The discrepancy between the mass M(A) = 12.6 +/- 0.6M. derived from evolutionary M(A) = 10.9 +/- 0.9M. previously obtained from interferometric and spectroscopic observations confirms the existence of a problem of ''evolutionary'' mass for O and early B stars. Its solution is likely to reduce to the effect of mixing at the MS stage being taken into account.

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Documento generato il 22/01/19 alle ore 22:57:10