Determination of chemical abundances in yellow symbiotic stars from the southern hemsiphere / "Determinação de abundâncias químicas em simbióticas amarelas austrais"

AUTOR(ES)

Silvia Ribeiro Calbo

DATA DE PUBLICAÇÃO

2004

RESUMO

The present work is a contribution to the study of chemical composition of southern symbiotic stars, scarcely studied in literature. We present a complete set of yellow southern symbiotic stars extracted from Belczynski. Some of the objects analyzed had no spectroscopic data in literature. The data were obtained using 1.6m telescope in LNA, Brazil and the IUE satelite database. The reddening was calculated from Hydrogen recombination lines. From the ratio fluxes of the lines of [OIII] and [NII] and a hypothetical electronic temperature of 12 000K (Nussbaumer) we estimated the eletronic density of the nebulae present in the symbiotic system. With this data plus the fluxes of lines observed we obtained the chemical abundances in symbiotic nebulae; C,N,O in U.V. and He, Ar, S, O and N in visible. The abundances of the yellow symbiotic stars were compared to planetary disc nebulae extracted from Pottasch, cefeids form Luck &Lambert, G, K and M giant abundances from Lambert &Ries, G and K dwarfs from Reddy et. al., M giants from Smith &Lambert, Ba star abundances from Smith, mild Ba stars type G8 and K3 from Berdygina, early R from Dominy, C stars form Lambert et. al. and M and S (MS)stars from Smith &Lambert. We can distinguish two types of yellow symbiotic groups. One group presents CN cycle products and is situated near the low metalicity and solar metalicity curve. The other group is found near the C/O=1 curve that is made of rich carbon objects (Schmid &Nussbaumer).The yellow symbiotic stars enriched in carbon are not univically asociated with Ba or early R stars. These two groups represent respectively the yellow s and d symbiotics. The yellow symbiotic stars analyzed in this work confirm the model in which they would be AGB stars iluminated by some hot source radiation.

ASSUNTO(S)

estrela simbiótica spectroscopy abundância química austral southern hemisphere chemical abundance symbiotic stars espectroscopia

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