1. Constraints for stellar electron-capture rates on $^{86}$Kr via the $^{86}$Kr($t$,$^{3}$He$+\gamma$)$^{86}$Br reaction and the implications for core-collapse supernovae
- Author
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Titus, R., Ney, E. M., Zegers, R. G. T., Bazin, D., Belarge, J., Bender, P. C., Brown, B. A., Campbell, C. M., Elman, B., Engel, J., Gade, A., Gao, B., Kwan, E., Lipschutz, S., Longfellow, B., Lunderberg, E., Mijatovic, T., Noji, S., Pereira, J., Schmitt, J., Sullivan, C., Weisshaar, D., Zamora, J. C., Titus, R., Ney, E. M., Zegers, R. G. T., Bazin, D., Belarge, J., Bender, P. C., Brown, B. A., Campbell, C. M., Elman, B., Engel, J., Gade, A., Gao, B., Kwan, E., Lipschutz, S., Longfellow, B., Lunderberg, E., Mijatovic, T., Noji, S., Pereira, J., Schmitt, J., Sullivan, C., Weisshaar, D., and Zamora, J. C.
- Abstract
In the late stages of stellar core-collapse, prior to core bounce, electron captures on medium-heavy nuclei drive deleptonization and simulations require the use of accurate reaction rates. Nuclei with neutron number near $N=50$, just above atomic number $Z=28$, play an important role, but rates used in astrophysical simulations rely primarily on a relatively simple single-state approximation. In order to improve the accuracy of astrophysical simulations, experimental data are needed to test the electron-capture rates and to guide the development of better theoretical models. This work presents the results of the $^{86}$Kr($t$,$^{3}$He+$\gamma$) experiment at the NSCL, from which an upper limit for the Gamow-Teller strength up to an excitation energy in $^{86}$Br of 5 MeV is extracted. The derived upper limit for the electron-capture rate on $^{86}$Kr indicates that the rate estimated through the single-state approximation is too high and that rates based on Gamow-Teller strengths estimated in shell-model and QRPA calculations are more accurate. The QRPA calculations tested in this manner were used for estimating the electron capture rates for 78 isotopes near $N=50$ and above $Z=28$. The impact of using these new electron-capture rates in simulations of supernovae instead of the rates based on the single-state approximation is investigated, indicating a significant reduction in the deleptonization that affects multi-messenger signals, such as the emission of neutrinos and gravitational waves., Comment: 15 pages, 10 figures
- Published
- 2019
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