A&A Supplement series, Vol. 122, April I 1997, 31-42
Received February 27; accepted June 23, 1996
L. Zacs
, F.A. Musaev
, I.F. Bikmaev
, and O.
Alksnis
Send offprint request: L. Zacs
Radioastrophysical Observatory, Latvian Academy of
Sciences, Akademijas laukums 1, Riga LV-1527, Latvia
internet: zacs@acad.latnet.lv
Shemakha Astrophysical Observatory, Azerbaydzhan Academy of Sciences, 373243 Shemakha, Azerbaydzhan
Special Astrophysical Observatory, Russian Academy of Sciences, 357147 Niznhny Arkhyz, Karachai-Cherkess Republic, Russia
Department of Astronomy, Kazan State University, Lenin str. 18, 420008 Kazan, Russia
University of Latvia, Raina blvd. 19, Riga LV-1586, Latvia
Detailed abundance analyses have been carried out for
17 single-lined binaries (giants and dwarfs) with orbital elements and mass
functions similar to those of barium stars, using high-dispersion CCD spectra
and model atmospheres. All these binary systems contain an unseen low-mass component, presumably, a white
dwarf. A mild enhancement (
) of the averaged s-process elements abundances
has been found only for two stars. The heavy-element overabundances in these stars are much less marked
than those of the classical barium stars having similar orbital periods. We have concluded that the existence
of a white dwarf (WD) companion in binary systems with barium star like characteristics is not sufficient
to produce a strong barium star. However, five of the analyzed giants show a significant
enhancement (
) of barium. The analysis indicates that a main sequence companion
has not a significant influence (due to tidal mixing, as has been sometimes suggested) on the
internal structure (chemical composition) of the primary star. Since barium enhanced giants occupy a place
on the (eccentricity-orbital period) plane similar to BaII stars we have concluded that a mild barium
enhancement in these stars is due to mass transfer from the companion during its
late phases of evolution. Thus it seems likely that all giants (primaries) in
barium star like binary systems with WD component have chemical peculiarities
(very slight in some cases) depending, apparently, on the efficiency of mass
transfer in a specific binary system. The significant enhancement of heavy
elements in the atmospheres of two radial velocity non-variable barium stars
shows then that these barium stars have either very long orbital periods or high
inclined orbital planes.
keywords: binaries: spectroscopic -- stars: chemically peculiar -- stars: abundances -- stars: fundamental parameters -- stars: evolution