First direct measurement constraining the $^{34}$Ar($\alpha$,p)$^{37}$K reaction cross section for mixed hydrogen and helium burning in accreting neutron stars

Author:

J. Browne, K. A. Chipps, K. Schmidt, H. Schatz, S. Ahn, S. D. Pain, F. Montes, W. J. Ong, U. Greife, J. Allen, D. W. Bardayan, J. C. Blackmon, D. Blankstein, S. Cha, K. Y. Chae, M. Febbraro, M. R. Hall, K. L. Jones, A. Kontos, Z. Meisel, P. D. O'Malley, K. T. Schmitt, K. Smith, M. S. Smith, P. Thompson, R. Toomey, M. Vostinar, D. Walter

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex)

journal:

Phys. Rev. Lett. 130 (2023) 212701

date:

2023-05-29 16:00:00

Abstract

The rate of the final step in the astrophysical $\alpha$p-process, the $^{34}$Ar($\alpha$,\textit{p})$^{37}$K reaction, suffers from large uncertainties due to lack of experimental data, despite having a considerable impact on the observable light curves of x-ray bursts and the composition of the ashes of hydrogen and helium burning on accreting neutron stars. We present the first direct measurement constraining the $^{34}$Ar($\alpha$,p)$^{37}$K reaction cross section, using the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target. The combined cross section for the $^{34}$Ar,Cl($\alpha$,p)$^{37}$K,Ar reaction is found to agree well with Hauser-Feshbach predictions. The $^{34}$Ar($\alpha$,2p)$^{36}$Ar cross section, which can be exclusively attributed to the $^{34}$Ar beam component, also agrees to within the typical uncertainties quoted for statistical models. This indicates the applicability of the statistical model for predicting astrophysical ($\alpha$,p) reaction rates in this part of the $\alpha$p process, in contrast to earlier findings from indirect reaction studies indicating orders-of-magnitude discrepancies. This removes a significant uncertainty in models of hydrogen and helium burning on accreting neutron stars.

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