Absolute Determination of the 22Na(p,g) Reaction Rate in Novae

Abstract

Gamma-ray telescopes in orbit around the Earth are searching for evidence of the elusive radionuclide 22Na produced in novae. Previously published uncertainties in the dominant destructive reaction, 22Na(p,g)23Mg, indicated new measurements in the proton energy range of 150 to 300 keV were needed to constrain predictions. We have measured the resonance strengths, energies, and branches directly and absolutely by using protons from the University of Washington accelerator with a specially designed beamline, which included beam rastering and cold vacuum protection of the 22Na implanted targets. The targets, fabricated at TRIUMF-ISAC, displayed minimal degradation over a ~ 20 C bombardment as a result of protective layers. We avoided the need to know the stopping power, and hence the target composition, by extracting resonance strengths from excitation functions integrated over proton energy. Our measurements revealed that resonance strengths for E_p = 213, 288, 454, and 610 keV are stronger by factors of 2.4 to 3.2 than previously reported. Upper limits have been placed on proposed resonances at 198-, 209-, and 232-keV. We have re-evaluated the 22Na(p,g) reaction rate, and our measurements indicate the resonance at 213 keV makes the most significant contribution to 22Na destruction in novae. Hydrodynamic simulations including our rate indicate that the expected abundance of 22Na ejecta from a classical nova is reduced by factors between 1.5 and 2, depending on the mass of the white-dwarf star hosting the nova explosion.

arXiv comment20 pages, 18 figures; shortened paper, accepted in Phys. Rev. C

References in corpus (12)

• Radioactive 26Al and massive stars in the Galaxy
• Nucleosynthesis in Classical Novae: ONe vs. CO White Dwarfs
• Charged-Particle Thermonuclear Reaction Rates: II. Tables and Graphs of Reaction Rates and Probability Density Functions
• The Effects of Thermonuclear Reaction Rate Variations on Nova Nucleosynthesis: A Sensitivity Study
• Presolar Grains from Novae
• The Imprint of Nova Nucleosynthesis in Presolar Grains
• Nuclear uncertainties in the NeNa-MgAl cycles and production of 22Na and 26Al during nova outbursts
• Precise measurement of the ^7Be(p,gamma)^8B S-factor
• The 21Na(p,gamma)22Mg Reaction and Oxygen-Neon Novae
• Hydrodynamic Models of Type I X-Ray Bursts: Metallicity Effects
• Reevaluation of the ${}^{22}$Na(p,$\gamma$) reaction rate: Implications for the detection of ${}^{22}$Na gamma rays from novae
• Direct measurements of 22Na(p,g)23Mg resonances and consequences for 22Na production in classical novae

Cited by in corpus (10)

• Presupernova evolution and explosive nucleosynthesis of rotating massive stars in the metallicity range -3 <=[Fe/H]<= 0
• A new study of the ${}^{22}$Ne(p,$\gamma$)${}^{23}$Na reaction deep underground: Feasibility, setup, and first observation of the 186 keV resonance
• Structure of 23Al from one-proton breakup reaction and astrophysical implications
• Low-energy ${}^{23}$Al $\beta$-delayed proton decay and ${}^{22}$Na destruction in novae
• The structure of a recent nova shell as observed by ALMA
• Branches of 33S(p,γ)34Cl at Oxygen-Neon Nova Temperatures
• Measurement of Lifetimes in 23Mg
• The $2_1^{+}\to 3_1^{+}$ gamma width in ${}^{22}$Na and second class currents
• Production of 26Al in stellar hydrogen-burning environments: spectroscopic properties of states in 27Si
• The 2025 Evaluation of Experimental Thermonuclear Reaction Rates (ETR25)