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DOE OSTI · 3001608

Low-metallicity Nova Explosions: A Site for Weak rp -process Nucleosynthesis

Psaltis, Athanasios [Duke University, Durham, NC (United States)] (ORCID:0000000321970797)·José, Jordi [Universitat Politècnica de Catalunya, Barcelona (Spain); Institut d’Estudis Espacials de Catalunya, Castelldefels (Spain)] (ORCID:0000000299372685)·Longland, Richard [Duke University, Durham, NC (United States); North Carolina State University, Raleigh, NC (United States)] (ORCID:000000017731580X)·Iliadis, Christian [Duke University, Durham, NC (United States); University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000323810412)
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Abstract

Classical novae are common cataclysmic events involving a binary system of a white dwarf and a main-sequence or red giant companion star. In metal-poor environments, these explosions produce ejecta differently from their solar counterparts due to the accretion of subsolar-metallicity material onto the white dwarf. In particular, it has been suggested that the nucleosynthesis flow in such low-metallicity nova explosions extends up to the Cu–Zn region, much beyond the expected endpoint, around Ca, predicted for solar-metallicity classical novae. This behavior resembles a weak rp-process, and such nuclear activity has never been observed in accreting white dwarf binaries with typical accretion flows. In this work, we study the characteristics of the weak rp-process for four nova models with metallicities Z = 2 × 10 −9 , 10 −7 , 2 × 10 −6 , and 2 × 10 −5 , and explore the impact of the nuclear physics uncertainties via a Monte Carlo sensitivity study. We identify nuclear reactions whose uncertainties affect the production of intermediate-mass nuclei under these conditions. These reactions and relevant nuclear quantities are targets for measurements at stable or radioactive beam facilities to reduce their rate uncertainties.

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Classical novaeExplosive nucleosynthesisNuclear astrophysicsNuclear reaction cross sectionsclassical novaeexplosive nucleosynthesisnuclear astrophysicsnuclear reaction cross sections

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BibTeXRIS

Psaltis, Athanasios [Duke University, Durham, NC (United States)] (ORCID:0000000321970797), José, Jordi [Universitat Politècnica de Catalunya, Barcelona (Spain); Institut d’Estudis Espacials de Catalunya, Castelldefels (Spain)] (ORCID:0000000299372685), Longland, Richard [Duke University, Durham, NC (United States); North Carolina State University, Raleigh, NC (United States)] (ORCID:000000017731580X), Iliadis, Christian [Duke University, Durham, NC (United States); University of North Carolina at Chapel Hill, NC (United States)] (ORCID:0000000323810412). 2025-07-01. Low-metallicity Nova Explosions: A Site for Weak rp -process Nucleosynthesis. https://doi.org/10.3847/1538-4357%2Faddfd5

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DOE OSTI2025

Impact of Thermonuclear Reaction Rate Uncertainties on the Identification of Presolar Grains from Classical Novae

Approximately 30%–40% of classical novae generate dust between 20 and 100 days following the eruption. However, there has yet to be a definitive identification of presolar stardust grains originating from classical novae. While multiple studies have suggested a nova origin for specific grains, aligning simultaneously all measured isotopic ratios of a specific grain with those predicted from simulations remains challenging. Using Monte Carlo simulations, this work investigates how uncertainties in thermonuclear reaction rates influence the isotopic ratios predicted in simulations of classical novae, specifically impacting the identification of presolar grains. In particular, we address two questions: (i) What is the impact of uncertainties in reaction rates on the range of isotopic ratios predicted by classical nova simulations? (ii) Which reaction rate uncertainties most significantly influence the predicted abundance ratios in presolar grains? Our results show that current reaction rate uncertainties affect the isotopic ratios of 12 C/ 13 C, 14 N/ 15 N, 16 O/ 17 O, 16 O/ 18 O, 24 Mg/ 25 Mg, 24 Mg/ 26 Mg, 26 Al/ 27 Al, and 28 Si/ 29 Si by less than 20% in either carbon–oxygen or oxygen–neon (ONe) novae, especially when considering the mixing of matter throughout the entire envelope. However, the isotopic ratios of 28 Si/ 30 Si, 32 S/ 33 S, and 32 S/ 34 S in ONe novae are exceptions: their variability greatly exceeds a factor of 2 due to the uncertainties in the reaction rates of 30 P(p,γ) 31 S, 33 S(p,γ) 34 Cl, and 34 S(p,γ) 35 Cl, respectively. These results highlight the significant influence of specific reaction rates on the predicted abundance ratios and underscore the necessity for accurate nuclear measurements to reduce these uncertainties.

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