ARE SYMBIOTIC STARS THE PRECURSORS OF TYPE-IA SUPERNOVAE

Arguments have been presented recently which favor a membership in the bulge/thick-disk population for symbiotic stars together with a shorter distance scale than previously accepted. Observational evidence from eclipsing symbiotic novae suggests that the large-amplitude thermonuclear outbursts of the white dwarf components are not accompanied by mass loss. On these premises we reanalyze the question of the frequency of symbiotics in the Galaxy, notice that their discovery probability so far has been grossly overestimated, and derive under conservative assumptions a total number for them of approximately 3 x 10(5), some 100 times more than currently reported. It follows that to account for the observed frequency of SN la's in the Galaxy it is sufficient that only approximately 4% of these symbiotics conclude their evolution with the accreting white dwarf reaching the Chandrasekhar limit and exploding as a supernova. The observational evidence that the late-type giants in symbiotic stars are losing mass at a rate much higher than single red giants of the same spectral type suggests that mass transfer in symbiotics is a self-regulating mechanism, which may delay or even prevent the formation of a common envelope after the primary has evolved to the white dwarf stage. Altogether, these characteristics of symbiotics make them the most attractive known candidate progenitor for SN Ia events.