The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models

By S. Bisterzo, Roberto Gallino, O. Straniero, S. Cristallo, F. Kaeppeler. 2011

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High-resolution spectroscopic observations of a hundred metal-poor Carbon and s-rich stars (CEMP-s) collected from the literature are compared with the theoretical nucleosynthesis models of asymptotic giant branch (AGB) presented in Paper I (M = 1.3, 1.4, 1.5, 2 Msun, -3.6 < [Fe/H] < -1.5). The s-process enhancement detected in these objects is associated to binary systems: the more massive companion evolved faster through the thermally pulsing AGB phase (TP-AGB), synthesising in the inner He-intershell the s-elements, which are partly dredged-up to the surface during the third dredge-up (TDU) episode. The secondary observed low mass companion became CEMP-s by mass transfer of C and s-rich material from the primary AGB. We analyse the light elements as C, N, O, Na and Mg, as well as the two s-process indicators, [hs/ls] (where ls = is the the light-s peak at N = 50 and hs = the heavy-s peak at N = 82), and [Pb/hs]. We distinguish between CEMP-s with high s-process enhancement, [hs/Fe] > 1.5 (CEMP-sII), and mild s-process enhanced stars, [hs/Fe] < 1.5 (CEMP-sI). To interpret the observations, .... . Detailed analyses for individual stars will be provided in Paper III.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2af26a6f686b42272a089e9e179df56f164e213e

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Citations in the corpus

THE s-PROCESS IN ASYMPTOTIC GIANT BRANCH STARS OF LOW METALLICITY AND THE COMPOSITION OF CARBON-ENHANCED METAL-POOR STARS (2011, background): “6 of Jonsell et al. 2006; Bisterzo et al. 2011b, respectively), the CEMP-s/r stars are separated from the CEMP-s in that they show [ls/hs] lower by at least 0.5 dex.”
NUGRID STELLAR DATA SET. I. STELLAR YIELDS FROM H TO BI FOR STARS WITH METALLICITIES Z = 0.02 and Z = 0.01 (2013, background): “…113In, 120Te, 124,126Xe, 130,132Ba, 136,138Ce, 138La, 144Sm, 152Gd, 156,158Dy, 162,164Er, 168Yb, 174Hf, 180Ta, 180W, 184Os, 190Pt, and 196Hg. – 27 – controversial predictions Arlandini et al. 1999; Goriely & Mowlavi 2000; Bisterzo et al. 2011) and in massive stars (e.g., Rauscher et al. 2002).”
HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS FROM SDSS/SEGUE. I. ATMOSPHERIC PARAMETERS AND CHEMICAL COMPOSITIONS (2012, background): “Note that recent studies of CEMP-s stars split this class even more granularly (e.g., Bisterzo et al. 2011).”
CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES (2014, unknown): “Radial-velocity monitoring (e.g., Lucatello et al. 2005) confirms the binarity of the majority of these CEMP stars, and extensive studies have been conducted to compare the observed abundance patterns with theoretical models (e.g., Bisterzo et al. 2011; Placco et al. 2013; Hollek et al. 2014).”
GALACTIC CHEMICAL EVOLUTION AND SOLAR s-PROCESS ABUNDANCES: DEPENDENCE ON THE 13C-POCKET STRUCTURE (2014, methodology): “As a minimum 13C pocket, we assume case ST × 0.1 at disk metallicities and case ST × 0.03 in the halo (see discussion by Bisterzo et al. 2010, 2011).”
The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars (2014, background): “…in metallicity and mass (e.g., Hollowell & Iben 1988; Gallino et al. 1998; Goriely & Mowlavi 2000; Busso et al. 2001; Lugaro et al. 2003; Karakas et al. 2007, 2009; Cristallo et al. 2009, 2011; Karakas & Lugaro 2010; Bisterzo et al. 2010, 2011, 2012; Lugaro et al. 2012; Pignatari et al. 2013).”
STELLAR YIELDS FROM METAL-RICH ASYMPTOTIC GIANT BRANCH MODELS (2016, background): “…2012), AGB stars and chemically peculiar stars that show the chemical signature of mass transfer from low-mass AGB stars (e.g., Ba and CH stars, carbon enhanced metal-poor stars; Busso et al. 2001; Bisterzo et al. 2011; Lugaro et al. 2012) as well as pre-solar grains (Lugaro et al. 2003, 2014b).”
CARBON-ENHANCED METAL-POOR STARS IN SDSS/SEGUE. I. CARBON ABUNDANCE ESTIMATION AND FREQUENCY OF CEMP STARS (2013, background): “…– log10(N(C)/N(Fe))⊙ branch (AGB) star to its (presently observed) binary companion (e.g., Herwig 2005; Sneden et al. 2008; Masseron et al. 2010; Bisterzo et al. 2011, 2012); (2) massive, rapidly rotating, zero-metallicity stars, which produce large amounts of carbon, nitrogen, and oxygen…”