Low-metallicity nova explosions: a site for weak rp-process nucleosynthesis

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.

The TUNL authors acknowledge support from U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-SC0017799 and contract Nos. DE-FG02-97ER41033 (TUNL), DE-FG02-97ER41041 (UNC), and DE-FG02-97ER41042 (NCSU). J.J. acknowledges support from the Spanish MINECO grant PID2023-148661NB-I00, the E.U. FEDER funds, and the AGAUR/Generalitat de Catalunya grant SGR-386/2021. The authors would like to thank S. Shore and N. Evans for fruitful discussions.

Peer Reviewed

Postprint (published version)