THEs-PROCESS IN ASYMPTOTIC GIANT BRANCH STARS OF LOW METALLICITY AND THE COMPOSITION OF CARBON-ENHANCED METAL-POOR STARS

Abstract

We present models for the slow neutron-capture process (s process) in asymptotic giant branch (AGB) stars of metallicity [Fe/H]=−2.3 and masses 0.9 M ⊙ to 6 M ⊙ . We encountered different regimes of neutron-capture nucleosynthesis increasing in importance as the stellar mass decreases: the 22 Ne(α,n) 25 Mg reaction activated during the thermal pulses, the 13 C(α,n) 16 O reaction activated in

THE DIVERSE ORIGINS OF NEUTRON-CAPTURE ELEMENTS IN THE METAL-POOR STAR HD 94028: POSSIBLE DETECTION OF PRODUCTS OF i-PROCESS NUCLEOSYNTHESIS*

“…Several example fits are shown. To create the fits shown in Figure 5, we mix the final ejected AGB yields with an r-process "foundation" of material (e.g., Bisterzo et al 2012;Lugaro et al 2012). Nearly all metal-poor stars contain some r-process material (e.g., Roederer 2013), and we assume that HD94028 also inherited r-process material from its natal cloud.…”

“…Most of these species are impossible to detect in the spectral range accessible to ground-based telescopes, and Ge, Cd, Lu, Pt, and Au had not been detected previously in any CEMP-s star.HD196944 and HD201626 are each in wide binary systems with orbital periods of 1325 and 407day (Lucatello et al 2005;Placco et al 2015). Placco et al compared these abundances with model predictions, revealing that each star could be reasonably fit by the predicted s-process yields from models of low-mass (≈0.9 M e ) stars on the asymptotic giant branch (AGB; Lugaro et al 2012;Placco et al 2013).The elements detected in the NUV had only a minor impact on the model selection, but the abundances of these elements all lie reasonably close (within ≈2σ) to the model predictions. One exception, Cd in HD196944, was about 1 dex lower than that predicted by the model.…”

Accelerator mass spectrometry measurements of theC13(n,γ)C14andWallner1, Bichler2, Buczak3 et al. 2016Phys. Rev. C281170View full textAdd to dashboardCite

“…Therefore, AMS offers a highly sensitive and complementary tool for cross-section measurements of nuclear reactions leading to radioactive nuclides, independent of their half-lives or decay patterns. The list of reaction products of interest for astrophysics includes radioisotopes over the entire mass range, e.g., 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 55 244 Pu. The present AMS measurements have been performed at the Vienna Environmental Research Accelerator (VERA) which represents a state-of-the-art AMS facility based on a 3-MV tandem [42,43].…”

“…Detailed information about the stellar evolutionary sequences can be found in [53] and [54]. The numerical method used in this study was described by Lugaro et al [55].…”

SAGA: Stellar Abundances for Galatic Archeology

“…This tool is helpful not only for looking up the available data but also for comparing models and observations, which can be applied to various astrophysical problems. For example, abundances patterns of EMP stars can be compared with nucleosynthesis models of supernovae [3], AGB yields [4,5,6,11,12], planetary nebulae [15], yields from rotating massive stars [14], and so on. Comparisons with Galactic chemical evolution models [7] and binary population models [8,9,10] are also possible.…”