S-Process--Enriched Cool Stars with and without Technetium: Clues to Asymptotic Giant Branch and Binary Star Evolution
Abstract
High-resolution spectra at λ4260 have been obtained for 40 stars of type MS or S to search for the presence of Tc I. In addition, previously published Tc surveys provide an additional 18 stars for a total sample of 58 MS or S stars. Most of these stars have also been observed in Zr I, Y II, La II, and Nd II lines. These stars show general s-process abundance enhancements. Of the total sample, 38% of these s-process-enriched stars do not show Tc. The authors suggest that the MS and S stars are composed of two major groups: (1) Tc-containing stars which are currently thermally pulsing AGB stars undergoing third dredge-up and (2) Tc-poor stars which represent the coolest members of the barium star class, where s-process enrichment is probably the result of binary mass transfer in the past.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1988
- DOI:
- 10.1086/166738
- Bibcode:
- 1988ApJ...333..219S
- Keywords:
-
- Asymptotic Giant Branch Stars;
- Binary Stars;
- Cool Stars;
- Stellar Composition;
- Stellar Evolution;
- Technetium;
- Barium;
- M Stars;
- S Stars;
- Stellar Atmospheres;
- Stellar Spectra;
- Astrophysics;
- STARS: ABUNDANCES;
- STARS: BA II;
- STARS: BINARIES;
- STARS: LATE-TYPE;
- STARS: S-TYPE