High-resolution spectroscopic analysis of four new chemically peculiar stars

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Abstract
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 fruitys-process nucleosynthesis models. BD+03○2688, HE 1255-2324, and HE 2207-1746 show C/O >1, while HE 0457-1805 has C/O 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.
Funding Information
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico
  • NKFI (KH_18 130405)
  • National Science Foundation (AST 1616040)

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