2023MNRAS.518.5414R -
Mon. Not. R. Astron. Soc., 518, 5414-5443 (2023/February-1)
High-resolution spectroscopic analysis of four new chemically peculiar stars.
RORIZ M.P., PEREIRA C.B., JUNQUEIRA S., LUGARO M., DRAKE N.A. and SNEDEN C.
Abstract (from CDS):
We present detailed chemical compositions of four stars on the first-ascent red giant branch that are classified as chemically peculiar, but lack comprehensive analyses at high spectral resolution. For BD+03°2688, HE 0457-1805, HE 1255-2324, and HE 2207-1746, we derived metallicities [Fe/H] = -1.21, -0.19, -0.31, and -0.55, respectively, indicating a range in Galactic population membership. In addition to atmospheric parameters, we extracted elemental abundances for 28 elements, including the evolutionary-sensitive CNO group and 12C/13C ratios. Novel results are also presented for the heavy elements tungsten and thallium. All four stars have very large enhancements of neutron-capture elements, with high [La/Eu] ratios indicating enrichments from the slow neutron capture (s-process). To interpret these abundances, all indicative of [s/Fe] >1.0, we compared our results with data from literature, as well as with predictions from the Monash and FRUITY s-process nucleosynthesis models. BD+03°2688, HE 1255-2324, and HE 2207-1746 show C/O >1, while HE 0457-1805 has C/O <1. Since HE 0457-1805 and HE 1255-2324 are binary stars, their peculiarities are attributable to mass transfer. We identified HE 0457-1805 as a new barium giant star, and HE 1255-2324 as a new CH star, in fact a higher metallicity analogue CEMP-r/s star; the single object reported in literature so far with similar characteristics is the barium star HD 100503 ([Fe/H] = -0.72). A systematic monitoring is needed to confirm the binary nature of BD+03°2688 and HE 2207-1746, which are probably CH stars.
Abstract Copyright:
© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Journal keyword(s):
nuclear reactions, nucleosynthesis, abundances - stars: abundances - stars: AGB and post-AGB - stars: chemically peculiar - stars: evolution - stars: fundamental parameters
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Simbad objects:
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