A New¹⁷F(p, γ)¹⁸Ne Reaction Rate and Its Implications for Nova Nucleosynthesis

Abstract

Proton capture by 17 F plays an important role in the synthesis of nuclei in nova explosions. A revised rate for this reaction, based on a measurement of the 1 H( 17 F,p) 17 F excitation function using a radioactive 17 F beam at ORNL's Holifield Radioactive Ion Beam Facility, is used to calculate the nucleosynthesis in nova outbursts on the surfaces of 1.25 M ⊙ and 1.35 M ⊙ ONeMg white dwarfs and a 1.00 M ⊙ CO white dwarf. We find that the new 17 F (p,γ) 18 Ne reaction rate changes the abundances of some nuclides (e.g., 17 O) synthesized in the hottest zones of an explosion on a 1.35 M ⊙ white dwarf by more than a factor of 10 4 compared to calculations using some previous estimates for this reaction rate, and by more than a factor of 3 when the entire exploding envelope is considered. In a 1.25 M ⊙ white dwarf nova explosion, this new rate changes the abundances of some nuclides synthesized in the hottest zones by more than a factor of 600, and by more than a factor of 2 when the entire exploding envelope is considered. Calculations for the 1.00 M ⊙ white dwarf nova show that this new rate changes the abundance of 18 Ne by 21%, but has negligible effect on all other nuclides. Comparison of model predictions with observations is also discussed.

Recent astrophysical studies with exotic beams at ORNL

“…The rate is about two to five times smaller than that of Coc et al [7] in the nova temperature range. We have used this updated 18 F(p, α) 15 O reaction rate in a nova nucleosynthesis calculation based on a post-processing approach with temperature and density histories of 28 zones of ejected material determined from hydrodynamics calculations of an explosion on the surface of a 1.25 solar mass white dwarf star [22]. The tools for this calculation are online in the Computational Infrastructure for Nuclear Astrophysics [23].…”

“…8. In this initial test measurement, 22 8 B recoils were observed resulting in a rough cross-section measurement of 1.12 µb with 24% uncertainty at E c.m. = 1.5 MeV.…”

Algebraic stabilization of explicit numerical integration for extremely stiff reaction networks

“…4(b) we estimate that a standard explicit method would require ∼ 10 21 s of pro- . The calculation used the QSS method and a network containing 134 isotopes coupled by 1531 reactions, with rates taken from the REACLIB library [19] and initial abundances enriched in heavy elements [24]. cessor time to compute the pp-chains to hydrogen depletion, which is a thousand times longer than the age of the Universe.…”

Nuclear data for astrophysics: resources, challenges, strategies, and software solutions

“…The level of sophistication of such studies has significantly increased in the last decade. Some examples: X-ray burst simulations (with coupled hydrodynamics and nuclear networks) with different 15 O(α,γ) 19 Ne reaction rates [12] and examining overall reaction flows [13]; core collapse supernova simulations with different 132 Sn(n,γ) 133 Sn rates [14]; Type II supernova simulations with different weak reaction rates [15]; and multi-zone post-processing nova simulations with different 17 F(p,γ) 18 Ne [16] and 18 F(p,α) 15 O [17] reaction rates. For the future, it is imperative to vigorously pursue sensitivity studies with even mo re sophisticated models and, especially, more complete nuclear data sets.…”

“…and other theoretical calculations, it is imperative to design software systems that enable anyone to run and visualize these calculations. The Computational Infrastructure for Nuclear Astrophysics features explosive element burning ("reaction network" [18]) calculations using a post-processing approach [16] wherein the temperature and density evolution in time are pre-determined from separate, lengthy simulations where hydrodynamics and nuclear effects are fully coupled [19]. The suite facilitates sensitivity studies by enabling quick comparisons of the results of explosive nucleosynthesis simulations that utilize different, custom input nuclear data sets created by the User (fig.…”