期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 435, 期 1, 页码 698-706出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1329
关键词
stars: AGB and post-AGB; binaries: general; stars: carbon; stars: evolution stars: Population II; stars: variables: RR Lyrae
资金
- Alexander von Humboldt Foundation
- Research School of Astronomy and Astrophysics (RSAA)
- Australian Research Council [FS110200016]
- US National Science Foundation
- [PHY 08-22648]
- Australian Research Council [FS110200016] Funding Source: Australian Research Council
Certain carbon-enhanced metal-poor stars likely obtained their composition via pollution from some of the earliest generations of asymptotic giant branch stars and as such provide important clues to early Universe nucleosynthesis. Recently, Kinman et al. discovered that the highly carbon-and barium-enriched metal-poor star SDSS J1707+58 is in fact an RR Lyrae pulsator. This gives us an object in a definite evolutionary state where the effects of dilution of material during the main sequence are minimized owing to the object having passed through first dredge-up. We perform detailed stellar modelling of putative progenitor systems in which we accreted material from asymptotic giant branch stars in the mass range 1-2 M-circle dot. We investigate how the surface abundances are affected by the inclusion of mechanisms like thermohaline mixing and gravitational settling. While we are able to find a reasonable fit to the carbon and sodium abundances of SDSS J1707+58, suggesting accretion of around 0.1 M-circle dot from a 2 M-circle dot companion, the strontium and barium abundances remain problematic and this object may have experienced something other than a standard s-process. We have more success in fitting the abundances of the mildly carbon-enriched, metal-poor RR Lyrae pulsator TY Gru (CS 22881-071), which we suggest received 0.1 M-circle dot of material from a companion of around 1 M-circle dot
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