The 12C +12C reaction and the impact on nucleosynthesis in massive stars

Pignatari, M.; Hirschi, R.; Wiescher, M.; Gallino, R.; Bennett, M.; Beard, M.; Fryer, C.; Herwig, F.; Rockefeller, G.; X. Timmes, F.

Abstract

Despite much effort in the past decades, the C-burning reaction rate is uncertain by several orders of magnitude, and the relative strength between the different channels 12 C( 12 C, α) 20 Ne, 12 C( 12 C, p) 23 Na, and 12 C( 12 C, n) 23 Mg is poorly determined. Additionally, in C-burning conditions a high 12 C+ 12 C rate may lead to lower central C-burning temperatures and to 13 C(α, n) 16 O emerging as a more dominant neutron source than 22 Ne(α, n) 25 Mg, increasing significantly the s-process production. This is due to the chain 12 C(p, γ) 13 N followed by 13 N(β +) 13 C, where the photodisintegration reverse channel 13 N(γ, p) 12 C is strongly decreasing with increasing temperature. Presented here is the impact of the 12 C+ 12 C reaction uncertainties on the s-process and on explosive p-process nucleosynthesis in massive stars, including also fast rotating massive stars at low metallicity. Using various 12 C+ 12 C rates, in particular an upper and lower rate limit of ∼50,000 higher and ∼20 lower than the standard rate at 5 × 10 8 K, five 25 M ⊙ stellar models are calculated. The enhanced s-process signature due to 13 C(α, n) 16 O activation is considered, taking into account the impact of the uncertainty of all three C-burning reaction branches. Consequently, we show that the p-process abundances have an average production factor increased up to about a factor of eight compared with the standard case, efficiently producing the elusive Mo and Ru proton-rich isotopes. We also show that an s-process being driven by 13 C(α, n) 16 O is a secondary process, even though the abundance of 13 C does not depend on the initial metal content. Finally, implications for the Sr-peak elements inventory in the solar system and at low metallicity are discussed. © 2013. The American Astronomical Society. All rights reserved.

Citation

Pignatari, M., Hirschi, R., Wiescher, M., Gallino, R., Bennett, M., Beard, M., Fryer, C., Herwig, F., Rockefeller, G., & X. Timmes, F. (2013). The 12C +12C reaction and the impact on nucleosynthesis in massive stars. The Astrophysical journal, 762(1), Article 31. https://doi.org/10.1088/0004-637X/762/1/31

• Journal Article Type: Article
• Acceptance Date: Oct 25, 2012
• Online Publication Date: Dec 13, 2012
• Publication Date: Jan 1, 2013
• Deposit Date: Oct 25, 2018
• Publicly Available Date: Nov 7, 2018
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 762
• Issue: 1
• Article Number: 31
• DOI: https://doi.org/10.1088/0004-637X/762/1/31
• Keywords: Stars: abundances; Stars: evolution; Stars: interiors
• Public URL: https://hull-repository.worktribe.com/output/561935
• Publisher URL: http://iopscience.iop.org/article/10.1088/0004-637X/762/1/31/
• Contract Date: Oct 25, 2018