The impact of the revised 17O(p, α)14N reaction rate on 17O stellar abundances and yields
1 INAF, Osservatorio Astronomico di Teramo, 64100 Teramo, Italy
2 INFN, Laboratori Nazionali del Gran Sasso (LNGS), 67100 Assergi, Italy
3 Gran Sasso Science Institute, INFN, Viale F. Crispi 7, 67100 L’ Aquila, Italy
4 Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr 400, 01328 Dresden, Germany
5 SUPA, School of Physics and Astronomy, University of Edinburgh, EH9 3 FD Edinburgh, UK
6 Università di Napoli “Federico II” and INFN, Sezione di Napoli, 80126 Napoli, Italy
7 INFN, Sezione di Padova, via Marzolo 8, 35131 Padova, Italy
8 Department of Physics and Astronomy, University of Padova, via Marzolo 8, 35131 Padova, Italy
9 Università degli Studi di Genova and INFN, Sezione di Genova, via Dodecaneso 33, 16146 Genova, Italy
10 Institute for Nuclear Research (MTA ATOMKI), PO Box 51, 4001 Debrecen, Hungary
11 Università degli Studi di Torino and INFN, Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy
12 Università degli Studi di Milano and INFN, Sezione di Milano, via G. Celoria 16, 20133 Milano, Italy
13 INFN, Sezione di Roma La Sapienza, Piazzale A. Moro 2, 00185 Roma, Italy
14 Università degli Studi di Bari and INFN, Sezione di Bari, 70125 Bari, Italy
15 South Dakota School of Mines, 501 E. Saint Joseph St., SD 57701, USA
16 INFN, Sezione di Perugia, 06123 Perugia, Italy
Received: 31 August 2016
Accepted: 20 October 2016
Context. Material processed by the CNO cycle in stellar interiors is enriched in 17O. When mixing processes from the stellar surface reach these layers, as occurs when stars become red giants and undergo the first dredge up, the abundance of 17O increases. Such an occurrence explains the drop of the 16O/17O observed in RGB stars with mass larger than ~ 1.5M⊙. As a consequence, the interstellar medium is continuously polluted by the wind of evolved stars enriched in 17O.
Aims. Recently, the Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration released an improved rate of the 17O(p, α)14N reaction. In this paper we discuss the impact that the revised rate has on the 16O/17O ratio at the stellar surface and on 17O stellar yields.
Methods. We computed stellar models of initial mass between 1 and 20 M⊙ and compared the results obtained by adopting the revised rate of the 17O(p, α)14N to those obtained using previous rates.
Results. The post-first dredge up 16O/17O ratios are about 20% larger than previously obtained. Negligible variations are found in the case of the second and the third dredge up. In spite of the larger 17O(p, α)14N rate, we confirm previous claims that an extra-mixing process on the red giant branch, commonly invoked to explain the low carbon isotopic ratio observed in bright low-mass giant stars, marginally affects the 16O/17O ratio. Possible effects on AGB extra-mixing episodes are also discussed. As a whole, a substantial reduction of 17O stellar yields is found. In particular, the net yield of stars with mass ranging between 2 and 20 M⊙ is 15 to 40% smaller than previously estimated.
Conclusions. The revision of the 17O(p, α)14N rate has a major impact on the interpretation of the 16O/17O observed in evolved giants, in stardust grains and on the 17O stellar yields.
Key words: nuclear reactions, nucleosynthesis, abundances / stars: abundances / stars: evolution
© ESO, 2017