s process in low-mass asymptotic giant branch stars

By O. Straniero, Roberto Gallino, S. Cristallo. 2005

218 citations recorded by the source corpus.

Abstract The main component of the s process is produced by low mass stars ( 1.5 ⩽ M / M ⊙ ⩽ 3 ) , when they climb for the second time the red giant branch and experience a series of He shell flashes called thermal pulses. During the relatively long period (10 5 yr) that elapses between two subsequent thermal pulses, a slow neutron flux is provided by the 13 C ( α , n ) 16 O reaction taking place within a thin 13 C pocket located in the He-rich and C-rich mantel of these stars. A second, marginal, neutron burst occurs during the thermal pulse and it is powered by the 22 Ne ( α , n ) 25 Mg reaction. We review the present status of the nucleosynthesis models of low mass AGB stars. The advance in the knowledge of the complex coupling between convective mixing and nuclear process, which allows the surface enrichment of C- and s-process elements, is presented, together with the hypotheses concerning the physical mechanism driving the formation of the 13 C pocket. In order to illustrate the capabilities and the limits of the theory, an updated computation of a 2 M ⊙ stellar structure with solar chemical composition is reported. This model has been obtained by including a full nuclear network (from H up to Bi, at the termination point of the s-process path) into the stellar evolution code. The predicted modification of the surface composition occurring during the AGB evolution is shown. The new challenge of AGB modeling, namely, the study of C-rich and s-rich very metal-poor stars, is discussed.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/af6bd104e5d181dc3fd677865d78e7e6f1032028

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In Astronomy and Astrophysics

1. A. Karakas
2. M. Lugaro
3. Roberto Gallino
4. S. Cristallo
5. S. Bisterzo
6. A. Chieffi
7. M. Limongi
8. C. Abia

In Nuclear and High Energy Physics

1. A. Karakas
2. M. Lugaro
3. A. Chieffi
4. M. Limongi
5. S. Bisterzo
6. Roberto Gallino
7. C. Abia
8. S. Cristallo

Citations in the corpus

• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, background): “For a complete discussion on AGB nucleosynthesis the reader may refer to Busso et al. (1999); Straniero et al. (2006); Sneden et al. (2008); Käppeler et al. (2010).”
• The s process: Nuclear physics, stellar models, and observations (2010, methodology): “For a general discussion see Busso, Gallino, and Wasserburg (1999); Herwig (2004); Iben and Renzini (1983); Sneden, Cowan, and Gallino (2008); Straniero, Gallino, and Cristallo (2006).”
• Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements (2018, methodology): “Contrary to FRUITY models, in which a time-dependent mixing scheme is adopted (see, e.g., Straniero et al. 2006), in MST models instantaneous mixing is assumed within the convective zone and no extra-mixing beyond the convective boundaries is applied.”
• CHEMICAL ABUNDANCES FOR 855 GIANTS IN THE GLOBULAR CLUSTER OMEGA CENTAURI (NGC 5139) (2010, background): “…the s–process is widely believed to be active in thermally pulsing low and intermediate mass AGB stars, but theoretical models indicate that most of the s–process element production is probably constrained to stars in the range ∼1.3–3 M (e.g., Busso et al. 1999; Herwig 2005; Straniero et al. 2006).”
• STELLAR YIELDS FROM METAL-RICH ASYMPTOTIC GIANT BRANCH MODELS (2016, methodology): “Cristallo et al. (2015) adopt a Reimer’s mass-loss rate with η = 0.4 for the pre-AGB phase and then use the formulae from Straniero et al. (2006) for the AGB.”
• EVOLUTION, NUCLEOSYNTHESIS, AND YIELDS OF LOW-MASS ASYMPTOTIC GIANT BRANCH STARS AT DIFFERENT METALLICITIES (2009, methodology): “At fixed pulsational period, the resulting theoretical mass loss laws reproduce the minimum and the maximum mass-loss rates observed in Galactic AGB stars (see Figure 3 of Straniero et al. 2006).”
• s‐Process in low‐metallicity stars – I. Theoretical predictions (2010, background): “In particular, observational constraints for the calibration of the mass-loss rate at very low metallicities are lacking (see Straniero et al. 2006).”