s-Process Nucleosynthesis in Carbon Stars

By C. Abia, I. Domínguez, Roberto Gallino, M. Busso, S. Masera, O. Straniero, P. Laverny, B. Plez, Jordi Isern. 2002

142 citations recorded by the source corpus.

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 13C(α, n)16O reaction is the main source of neutrons for the s-process; a moderate spread, however, must exist in the abundance of 13C 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/6ee46c024141c7ad9d5efc733f197decc3da7113

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In Astronomy and Astrophysics

1. A. Karakas
2. M. Lugaro
3. J. Lattanzio
4. Roberto Gallino
5. Falk Herwig
6. S. Bisterzo
7. S. Cristallo
8. C. Sneden

Citations in the corpus

• s‐Process in low‐metallicity stars – I. Theoretical predictions (2010, background): “Spectroscopic observations of disc metallicity stars were done in the past for MS, S, C(N) stars, in order to search for intrinsic AGBs by detecting Tc lines (Smith & Lambert 1988, 1990; Brown et al. 1990; Busso et al. 2001; Abia et al. 2002).”
• STELLAR YIELDS FROM METAL-RICH ASYMPTOTIC GIANT BRANCH MODELS (2016, background): “…by the branching points at 203Hg and 204Tl (for which we have not yet implemented the predicted temperature dependence of the decay rates). solar metallicity (see e.g., Busso et al. 2001; Abia et al. 2002), a large number of neutrons are needed to be released in the intershell via (α,n) reactions.”
• The s process: Nuclear physics, stellar models, and observations (2010, background): “Abia et al. (2002) have determined chemical abundances of N type AGB stars.”
• Neutron-Capture Elements in the Early Galaxy (2008, methodology): “In essence, the choice of the 13C concentration in the pocket is left as a free parameter, in the range of the upper and lower limits specified above, to be calibrated by observational constraints (Busso et al. 2001, Abia et al. 2002, Gallino et al. 2005, Bisterzo et al. 2006a,b).”
• NUGRID STELLAR DATA SET. I. STELLAR YIELDS FROM H TO BI FOR STARS WITH METALLICITIES Z = 0.02 and Z = 0.01 (2013, background): “…grains (e.g., Lugaro et al. 2003a) and the spectroscopic observations of stars at different metallicities (Lambert et al. 1995; Busso et al. 2001; Abia et al. 2002; Masseron et al. 2010; Bisterzo et al. 2011; Lugaro et al. 2012; Maiorca et al. 2012) and planetary nebulae (Karakas et al. 2007;…”
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks (2004, background): “The companion star could have been an AGB star, in which these elements are believed to be synthesized (see, e.g., Abia et al. 2002), that now is invisible since it has evolved into a white dwarf.”
• s-Process Nucleosynthesis in Asymptotic Giant Branch Stars: A Test for Stellar Evolution (2002, background): “…ls ’’ is the average of light s-process elements (Y and Zr) and ‘‘ hs ’’ is the average of heavy s-process elements (Ba, La, Nd, and Sm), is a good indicator of the distribution of s-elements and varies in the range 0.6 to 0 for AGB stars of solar metallicity (Busso et al. 2001; Abia et al. 2002).”
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, background): “…Galactic disc MS, S, C(N) and Ba stars show a spread in the distribution of the sprocess elements for a given metallicity (Busso et al. 1995, 2001; Abia et al. 2001, 2002; Gallino et al. 2005; Husti et al. 2009 and references therein), which increases in the halo of CEMP-s stars (Sneden et al.…”
• Short-Lived Nuclei in the Early Solar System: A Low Mass Stellar Source? (2003, unknown): “The mass loss was parametrised through the Reimers (1975) formula: choices of this free parameter are discussed elsewhere (Gallino et al. 1998; Busso et al. 2001; Abia et al. 2002).”
• EVOLUTION, NUCLEOSYNTHESIS, AND YIELDS OF LOW-MASS ASYMPTOTIC GIANT BRANCH STARS AT DIFFERENT METALLICITIES (2009, methodology): “…telescopes, from very metal-poor C-rich stars (see Bisterzo et al. 2010 and references therein) to the Galactic and extragalactic C (N-type) stars (Abia et al. 2001, 2002, 2008, 2010; de Laverny et al. 2006; Zamora et al. 2009), Ba-stars (Allen & Barbuy 2006; Smiljanic et al. 2007; Liu et al.…”
• Astrophysics with Presolar Stardust (2004, background): “That this occurs is well documented by observations (Abia et al. 2002, Busso et al. 2001, Smith & Lambert 1990).”
• GALACTIC CHEMICAL EVOLUTION AND SOLAR s-PROCESS ABUNDANCES: DEPENDENCE ON THE 13C-POCKET STRUCTURE (2014, background): “…(planetary nebulae, post-AGB, MS, S, C(N), Ba, CH, and CEMP s stars; see, e.g., Smith & Lambert 1990; Péquignot & Baluteau 1994; Aoki et al. 2002; Abia et al. 2002; Allen & Barbuy 2006; Jonsell et al. 2006; Sharpee et al. 2007; Sterling & Dinerstein 2008; Reyniers et al. 2007; Zamora et al.…”
• The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, background): “…surface abundances predictions for AGB models (a highly incomplete list includes the following examples: Kahane et al. 2000; Chieffi et al. 2001; Abia et al. 2002; Lebzelter et al. 2008; Weiss & Ferguson 2009; Campbell et al. 2010; Bisterzo et al. 2010; Kamath et al. 2012; D’Orazi et al. 2013)…”
• Reaction Rate Uncertainties and the Production of 19F in Asymptotic Giant Branch Stars (2004, methodology): “Using data for carbon stars from Utsumi (1985), it appeared that these two quantities were correlated in AGB stars; however, using more recent and precise data from Abia et al. (2002), this correlation does not seem to appear anymore.”