Publication Date:
2020-02-03
Description:
We investigate the significance of isomers on a kilonova associated with neutron star mergers (NSMs) for the first time. We calculate the evolution of abundances and energy generation rates ($dot{epsilon }_{
m nuc}$) of ejecta from NSMs, taking into account β− decay through isomers. We find that for ejecta with electron fraction (Ye) of 0.2–0.3, $dot{epsilon }_{
m nuc}$ is appreciably changed from those without isomers, due to the large change in timing of β− decay through the isomeric states (ISs) of ${}^{123,125,127}
m Sn$ and ${}^{128}
m Sb$. In particular, the effects of the isomers on $dot{epsilon }_{
m nuc}$ are prominent for ejecta of Ye ∼ 0.25, which could emit a fraction of an early, blue component of a kilonova observed in GW170817. When the excitation from a ground state to its IS is important, the isomers of ${}^{129}
m Sb$ and ${}^{129, 131}
m Te$ also cause additional and appreciable change in $dot{epsilon }_{
m nuc}$. Furthermore, we demonstrate that larger amounts of lanthanide-free ejecta result in a better fit of an observed light curve of the kilonova in GW170817 if the isomers are taken into account.
Print ISSN:
1745-3925
Electronic ISSN:
1745-3933
Topics:
Physics
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