2002/07/11 by C. Abia, I. Dominguez, I. Domı́nguez +7 · 3 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Asymptotic giant branch #Carbon star #Metallicity #Nucleosynthesis #Physics #Stars #Stellar nucleosynthesis #Stellar, planetary, and galactic studies #astro-ph #s-process
paper · pdf · doi:10.1086/342924
published as Astrophys.J. 579 (2002) 817-831 · 31 pages, 10 figures, 6 tables. Accepted in ApJ
arxiv created 2002/07/11 · openalex publication_date 2002/11/04 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present the first detailed and homogeneous analysis of the s -element content in Galactic carbon stars of N type. Abundances of Sr, Y, Zr (low-mass s -elements, or ls), Ba, La, Nd, Sm, and Ce (high-mass s -elements, or hs) are derived using the spectral synthesis technique from high-resolution spectra. The N stars analyzed are of nearly solar metallicity and show moderate s -element enhancements, similar to those found in S stars, but smaller than those found in the only previous similar study (Utsumi 1985), and also smaller than those found in supergiant post-asymptotic giant branch (post-AGB) stars. This is in agreement with the present understanding of the envelope s -element enrichment in giant stars, which is increasing along the spectral sequence M → MS → S → SC → C during the AGB phase. We compare the observational data with recent s -process nucleosynthesis models for different metallicities and stellar masses. Good agreement is obtained between low-mass AGB star models ( M ≲ 3 M ☉ ) and s -element observations. In low-mass AGB stars, the 13 C(α, n ) 16 O reaction is the main source of neutrons for the s -process; a moderate spread, however, must exist in the abundance of 13 C that is burnt in different stars. By combining information deriving from the detection of Tc, the infrared colors, and the theoretical relations between stellar mass, metallicity, and the final C/O ratio, we conclude that most (or maybe all) of the N stars studied in this work are intrinsic, thermally pulsing AGB stars; their abundances are the consequence of the operation of third dredge-up and are not to be ascribed to mass transfer in binary systems.