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2. Impact of Nuclear Reaction Uncertainties on AGB Nucleosynthesis Models

Author

Claudia Travaglio, Sara Bisterzo, Kaeppeler Franz, Roberto Gallino, and Michael Wiescher

Subjects
Nuclear physics, Nuclear reaction, Physics, Astrophysics - Solar and Stellar Astrophysics, Nucleosynthesis, FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

Asymptotic giant branch (AGB) stars with low initial mass (1 - 3 Msun) are responsible for the production of neutron-capture elements through the main s-process (main slow neutron capture process). The major neutron source is 13C(alpha, n)16O, which burns radiatively during the interpulse periods at about 8 keV and produces a rather low neutron density (10^7 n/cm^3). The second neutron source 22Ne(alpha, n)25Mg, partially activated during the convective thermal pulses when the energy reaches about 23 keV, gives rise to a small neutron exposure but a peaked neutron density (Nn(peak) > 10^11 n/cm^3). At metallicities close to solar, it does not substantially change the final s-process abundances, but mainly affects the isotopic ratios near s-path branchings sensitive to the neutron density. We examine the effect of the present uncertainties of the two neutron sources operating in AGB stars, as well as the competition with the 22Ne(alpha, gamma)26Mg reaction. The analysis is carried out on AGB the main-s process component (reproduced by an average between M(AGB; ini) = 1.5 and 3 Msun at half solar metallicity, see Arlandini et al. 1999), using a set of updated nucleosynthesis models. Major effects are seen close to the branching points. In particular, 13C(alpha, n)16O mainly affects 86Kr and 87Rb owing to the branching at 85Kr, while small variations are shown for heavy isotopes by decreasing or increasing our adopted rate by a factor of 2 - 3. By changing our 22Ne(alpha, n)25Mg rate within a factor of 2, a plausible reproduction of solar s-only isotopes is still obtained. We provide a general overview of the major consequences of these variations on the s-path. A complete description of each branching will be presented in Bisterzo et al., in preparation., Proceedings of Science 108, XII International Symposium on Nuclei in the Cosmos 2012 (Cairns, Australia); 6 pages, 2 figures

Published
2013

3. Neutron cross sections at n_TOF

Author

M. Oshima, J. Andrzejewski, J. Pancin, A. Pavlik, S. Lukic, G. Cortes, B. Haas, Y. Kadi, I. Duran, Iris Dillmann, Costas G. Papadopoulos, H. Frais-Koelbl, V. Konovalov, M. Dahlfors, L. Perrot, C. Eleftheriadis, P. Vaz, K. Fujii, C. Carrapiço, Aaron Couture, F. Voss, J. Salgado, A. Poch, F. Becvar, I. Savvidis, P. Cennini, Thomas Rauscher, Roberto Capote, P.A. Assimakopoulos, W. Dridi, A. Goverdovski, Rene Reifarth, Isabel Lopes, F. Calviño, H. Leeb, Nicola Colonna, M. Embid-Segura, L. Ferrant, E. Griesmayer, G. Aerts, A. Plukis, F. Alvarez-Velarde, Vasilis Vlachoudis, H. Alvarez-Pol, L. Sarchiapone, D. Karadimos, F. Gramegna, Wiescher Michael, L. Fitzpatrick, Manuel Lozano, D. Karamanis, E. González-Romero, G. Vannini, K. Wisshak, Sara Bisterzo, R. Vlastou, Gerald Badurek, N. Patronis, J. M. Quesada, S. Andriamonje, L. Tassan-Got, E. Berthoumieux, A. Herrera-Martinez, R. Dolfini, E. Jericha, D. Villamarin, E. Chiaveri, M. Rosetti, M. C. Vincente, Arnaud Ferrari, R. Ferreira Marques, P. F. Mastinu, H. Wendler, S. David, M. Mosconi, Alberto Mengoni, C. Stephan, F. Gunsing, G. Tagliente, D. Cano-Ott, S. Isaev, S. O'Brien, V. Ketlerov, M. Krtička, P. E. Koehler, V. Chepel, G. Rudolf, F. Käppeler, Roberto Gallino, César Domingo Pardo, R. Terlizzi, C. Paradela, F. Neves, P. M. Milazzo, L. Audouin, P. Pavlopoulos, L. Tavora, J. Marganiec, P. Rullhusen, P. Baumann, C. Pretel, Masayuki Igashira, E. Kossionides, A. Lindote, Michael Heil, Carlos Guerrero, U. Abbondanno, Heinz Oberhummer, A. J. M. Plompen, S. Walter, Ralf Plag, James L. Cox, W.I. Furman, C. A. Papachristodoulou, Andrea Venturi, Corrie S. Moreau, M. Kerveno, C. Rubbia, Isabel S. Gonçalves, S. Marrone, C. Lamboudis, J. L. Tain, and Robert C. Haight

Subjects
Nuclear physics, Astrophysics and Astronomy, Materials science, Neutron
Published
2010

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