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BD-21 3873: another yellow-symbiotic barium star.
An abundance analysis of the yellow symbiotic system BD-21 3873 revealsit to be a metal-poor K-giant ([Fe/H]=-1.3) which is enriched in theheavy s-process elements. In that respect, this star appears to be atwin of AG Dra, another yellow symbiotic system analyzed in a previouspaper (Smith et al., 1996A&A...315..179S). The heavy-elementabundance distributions of AG Dra and BD-21 3873 are almost identical,and are best reproduced by a s-process with a neutron exposure parameterof 1.2-1.3mb^-1^ and a neutron density logN_n_=8.3 (as derived from theRb/Zr ratio). These two systems thus link the symbiotic stars to thebinary barium and CH stars which are also s-process enriched. Thesebinary systems, which exhibit overabundances of the heavy elements, owetheir abundance peculiarities to mass transfer from thermally-pulsingasymptotic giant branch stars, which have since evolved to becomewhite-dwarf companions of the cool stars we now view as thechemically-peculiar primaries. The spectroscopic orbits of BD-21 3873(derived from CORAVEL measurements) and AG Dra are similar to those ofbarium and CH stars. With an orbital period of 281.6d, BD-21 3873 is oneof the closest systems in these families, and its light curve indeedsuggests that variations due to reflection and ellipticity effects arepresent. The amplitude of the ellipsoidal variations indicates that thegiant must be close to filling its Roche lobe. However, no acceptablesolution simultaneously satisfies the constraints from the light curve,the orbital elements and the evolutionary tracks in the framework of thestandard Roche lobe geometry. We suggest that this discrepancy may beresolved by taking into account the deformation of the Roche lobe causedby the force driving the large mass loss of the giant.
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | נחש מים |
| התרוממות ימנית: | 14h12m07.51s |
| סירוב: | -23°42'04.0" |
| גודל גלוי: | 8.351 |
| מרחק: | 301.205 פארסק |
| תנועה נכונה: | 0.3 |
| תנועה נכונה: | 16 |
| B-T magnitude: | 9.558 |
| V-T magnitude: | 8.451 |
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