Do all barium stars have a white dwarf companion ?
Abstract
International Ultraviolet Explorer short-wavelength, low-dispersion spectra were analyzed for four barium, two mild barium, and one R-type carbon star in order to test the hypothesis that the barium and related giants are produced by mass transfer from a companion now present as a white dwarf. An earlier tentative identification of a white dwarf companion to the mild barium star Zeta Cyg is confirmed. For the other stars, no ultraviolet excess attributable to a white dwarf is seen. Limits are set on the bolometric magnitude and age of a possible white dwarf companion. Since the barium stars do not have obvious progenitors among main-sequence and subgiant stars, mass transfer must be presumed to occur when the mass-gaining star is already on the giant branch. This restriction, and the white dwarf's minimum age, which is greater than 8 x 10 to the 8th yr, determined for several stars, effectively eliminates the hypothesis that mass transfer from an asymptotic giant branch star creates a barium star. Speculations are presented on alternative methods of producing a barium star in a binary system.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1983
- DOI:
- 10.1086/161109
- Bibcode:
- 1983ApJ...270..180D
- Keywords:
-
- Barium;
- Binary Stars;
- Companion Stars;
- Giant Stars;
- Peculiar Stars;
- Stellar Evolution;
- White Dwarf Stars;
- Abundance;
- Asymptotic Giant Branch Stars;
- Carbon Stars;
- Hertzsprung-Russell Diagram;
- Nuclear Fusion;
- Planetary Nebulae;
- Stellar Magnitude;
- Stellar Mass Accretion;
- Stellar Spectra;
- Ultraviolet Spectra;
- Astrophysics