2011/03/10 by Satoshi Honda, Wako Aoki, Nobuo Arimoto +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Asymptotic giant branch #Binary number #Binary star #Dwarf galaxy #Dwarf spheroidal galaxy #Galaxy #Giant star #Red giant #Red-giant branch #Stars #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · doi:10.1093/pasj/63.sp2.s523
18 pages, PASJ in press
arxiv created 2011/03/10 · openalex publication_date 2011/03/25 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Abstract We determined the chemical abundances of the extremely metal-poor (EMP) star S 15–19 ([Fe/H] =-3.0) in the Sextans dwarf galaxy. While heavy neutron-capture elements (e.g., Ba) are generally deficient in EMP stars in dwarf galaxies, this object was shown to have an exceptional over-abundance of Ba ([Ba/Fe] ∼+0.5) by a previous study, which is similar to those of r-process-enhanced stars found in the field halo. Our new high-resolution spectroscopy for this object for the blue region, however, reveals that no clear excess of r-process elements, like Eu, appears in this object. Moreover, a significant excess of carbon ([C/Fe] =+1.0) and a deficiency of Sr ([Sr/Fe] =-1.4) are found for this object. Taking the variation of the radial velocities measured at the two different epochs into consideration, the origin of the excesses of heavy neutron-capture elements in S 15–19 is not the r-process, but is the s-process in an asymptotic giant branch (AGB) star that was the binary companion (primary) of this object. Carbon- and s-process-enhanced material should have been transferred to the surface of S 15–19 across the binary system. These results are compared with carbon-enhanced metal-poor stars in the field halo.