Carbon Stars in the Hamburg/ESO Survey: Abundances

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dc.creatorCohen, Judith G.
dc.creatorMcWilliam, Andrew
dc.creatorShectman, Stephen
dc.creatorThompson, Ian
dc.creatorChristlieb, Norbert
dc.creatorMelendez, Jorge
dc.creatorRamirez, Solange
dc.creatorSwensson, Amber
dc.creatorZickgraf, Franz-Josef
dc.date2006-03-21
dc.date.accessioned2026-07-07T11:25:24Z
dc.date.available2026-07-07T11:25:24Z
dc.descriptionWe have carried out a detailed abundance analysis for a sample of 16 carbon stars found among candidate extremely metal-poor (EMP) stars from the Hamburg/ESO Survey. We find that the Fe-metallicities for the cooler C-stars (Teff ~ 5100K) have been underestimated by a factor of ~10 by the standard HES survey tools. The results presented here provided crucial supporting data used by Cohen et al (2006) to derive the frequency of C-stars among EMP stars. C-enhancement in these EMP C-stars appears to be independent of Fe-metallicity and approximately constant at ~1/5 the solar C/H. The mostly low C12/C13 ratios (~4) and the high N abundances in many of these stars suggest that material which has been through proton burning via the CN cycle comprises most of the stellar envelope. C-enhancement is associated with strong enrichment of heavy nuclei beyond the Fe-peak for 12 of the 16 stars. The remaining C-stars from the HES, which tend to be the most Fe-metal poor, show no evidence for enhancement of the heavy elements. Very high enhancements of lead are detected in some of the C-stars with highly enhanced Ba. (We show that) the s-process is responsible for the enhancement of the heavy elements for the majority of the C-stars in our sample. We suggest that both the s-process rich and Ba-normal C-stars result from phenomena associated with mass transfer in binary systems. This leads directly to the progression from C-stars to CH stars and then to Ba stars as the Fe-metallicity increases. (abridged and slightly edited to shorten)
dc.descriptionAJ, in press, submitted 13 Dec, 2005, accepted 21 March 2006
dc.identifierhttps://arxiv.org/abs/astro-ph/0603582
dc.identifierhttp://arxiv.org/abs/astro-ph/0603582
dc.identifierAstron.J.132:137-160,2006
dc.identifierdoi:10.1086/504597
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/195495
dc.subjectAstrophysics
dc.titleCarbon Stars in the Hamburg/ESO Survey: Abundances
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