2006/08/04 by Aruna Goswami, A. Goswami, W. Aoki +11 · 3 citations
Physics and Astronomy · #Astronomical spectroscopy #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Asymptotic giant branch #Carbon star #K-type main-sequence star #Observatory #Spectral line #Stars #Stellar classification #Stellar, planetary, and galactic studies #T Tauri star #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2006.10877.x
published as Mon.Not.Roy.Astron.Soc.372:343-356,2006 · 19 pages, 11 figures, MNRAS format, accepted for publication in MNRAS
arxiv created 2006/08/04 · openalex publication_date 2006/09/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present results of an analysis of high-resolution spectra (R∼ 50 000), obtained with the Subaru Telescope High Dispersion Spectrograph, of two carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/European Southern Observatory prism survey, HE 1305+0007 and HE 1152−0355, and of the classical CH star HD 5223. All these stars have relatively low effective temperatures (4000–4750 K) and high carbon abundances, which result in the presence of very strong molecular carbon bands in their spectra. The stellar atmospheric parameters for these stars indicate that they all have surface gravities consistent with a present location on the red giant branch, and metallicities of [Fe/H]=−2.0 (HE 1305+0007, HD 5223) and [Fe/H]=−1.3 (HE 1152−0355). In addition to their large enhancements of carbon ([C/Fe]=+1.8, +1.6 and +0.6, respectively), all three stars exhibit strong enhancements of the s-process elements relative to iron. HE 1305+0007 exhibits a large enhancement of the third-peak s-process element, lead, with [Pb/Fe]=+2.37, as well as a high abundance of the r-process element europium, [Eu/Fe]=+1.97. The second-peak s-process elements, Ba, La, Ce, Nd and Sm, are found to be more enhanced than the first-peak s-process elements Zr, Sr and Y. Thus, HE 1305+0007 joins the growing class of the so-called ‘Lead stars’, and also the class of objects that exhibit the presence of both r- and s-process elements, the CEMP-r/s stars. The large enhancements of neutron-capture (n-capture) elements exhibited by HE 1152−0355 and HD 5223 are more consistent with the abundance patterns generally noticed in CH stars, essentially arising from pure s-process nucleosynthesis. The elemental abundance distributions observed in these stars are discussed in light of existing theories of CH star formation, as well as the suggested formation scenarios of the CEMP-r/s group.