Impact of experimental mass of $^{70}$Kr on the $^{68}$Se waiting-point in $rp$-process

TL;DR

This study uses a new mass measurement of $^{70}$Kr to refine models of the $rp$-process, showing increased flow past the $^{68}$Se waiting point and impacting X-ray burst light curves and nucleosynthesis.

Contribution

First experimental mass measurement of $^{70}$Kr significantly refines the $rp$-process modeling near the $^{68}$Se waiting point.

Findings

Enhanced $p$-capture flow by up to four times.

Reduced effective half-life of $^{68}$Se.

Altered light curve tail and final abundances in X-ray burst models.

Abstract

The recent mass measurement of $^{70}$Kr using the $B\rho$-defined isochronous mass spectrometry yields a mass excess of $-41320(140)$ keV, indicating a 220-keV increase in binding energy compared to the AME2020 prediction. We utilize this experimental mass -- the last piece of information needed -- to model the potential waiting point $^{68}$Se in $rp$-process and quantitatively constrain the sequential $p$-capture reaction flow bypassing this waiting point. Our investigation shows that the more tightly bound nature of $^{70}$Kr enhances this reaction flow up to a factor of four. This enhancement reduces the effective half-life of $^{68}$Se. {A} one-zone X-ray burst model calculations reveal that the higher flow of $^{70}$Kr has distinct effects on the tail structure of light curve and the final SnSbTe abundances in the ashes due to a stronger $rp$-process heating.