Thermonuclear ²⁸P(p, γ)²⁹S reaction rate and astrophysical implication in ONe nova explosion

¹ Key Laboratory of High Precision Nuclear Spectroscopy, Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd, Lanzhou 730000, PR China
e-mail: sqhou@impcas.ac.cn
² School of Nuclear Science and Technology, University of Chinese Academy of Sciences, 19A Yuquan Rd, Shijingshan District, Beijing 100049, PR China
³ Departament de Física, Universitat Politècnica de Catalunya, 08019 Barcelona, Spain
⁴ Institut d’Estudis Espacials de Catalunya, Universitat Politècnica de Catalunya, 08034 Barcelona, Spain
⁵ NuGrid Collaboration, http://www.nugridstars.org
⁶ Konkoly Observatory, HUN-REN, H-1121 Budapest, Konkoly Thege M. út 15–17, Hungary
⁷ CSFK, MTA Centre of Excellence, Budapest, Konkoly Thege Miklós út 15–17, 1121, Hungary
⁸ E. A. Milne Centre for Astrophysics, University of Hull, Cottingham Rd, Kingston upon Hull HU6 7RX, UK
⁹ Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements, 640 S Shaw Lane, East Lansing, MI 48824, USA
¹⁰ Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
¹¹ Triangle Universities Nuclear Laboratory, Durham, NC 27708, USA
¹² Department of Physics and Astronomy, Texas A&M University-Commerce, Commerce, TX 75429, USA

Received: 8 February 2024
Accepted: 11 April 2024

Abstract

Context. An accurate ²⁸P(p, γ)²⁹S reaction rate is crucial to defining the nucleosynthesis products of explosive hydrogen burning in ONe novae. Using the recently released nuclear mass of ²⁹S, together with a shell model and a direct capture calculation, we reanalyzed the ²⁸P(p, γ)²⁹S thermonuclear reaction rate and its astrophysical implication.

Aims. We focus on improving the astrophysical rate for ²⁸P(p, γ)²⁹S based on the newest nuclear mass data. Our goal is to explore the impact of the new rate and associated uncertainties on the nova nucleosynthesis.

Methods. We evaluated this reaction rate via the sum of the isolated resonance contribution instead of the previously used Hauser-Feshbach statistical model. The corresponding rate uncertainty at different energies was derived using a Monte Carlo method. Nova nucleosynthesis is computed with the 1D hydrodynamic code SHIVA.

Results. The contribution from the capture on the first excited state at 105.64 keV in ²⁸P is taken into account for the first time. We find that the capture rate on the first excited state in²⁸ P is up to more than 12 times larger than the ground-state capture rate in the temperature region of 2.5 × 10⁷ K to 4 × 10⁸ K, resulting in the total ²⁸P(p, γ)²⁹S reaction rate being enhanced by a factor of up to 1.4 at ~1 × 10⁹ K. In addition, the rate uncertainty has been quantified for the first time. It is found that the new rate is smaller than the previous statistical model rates, but it still agrees with them within uncertainties for nova temperatures. The statistical model appears to be roughly valid for the rate estimation of this reaction in the nova nucleosynthesis scenario. Using the 1D hydrodynamic code SHIVA, we performed the nucleosynthesis calculations in a nova explosion to investigate the impact of the new rates of ²⁸P(p, γ)²⁹S. Our calculations show that the nova abundance pattern is only marginally affected if we use our new rates with respect to the same simulations but statistical model rates. Finally, the isotopes whose abundance is most influenced by the present ²⁸P(p, γ)²⁹S uncertainty are ²⁸Si, ^33,34S, ^35,37Cl, and ³⁶Ar, with relative abundance changes at the level of only 3% to 4%.