Affiliation:
1. National Institute of Technology, Kumamoto College, Kumamoto 861-1102, Japan
2. Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
Abstract
ABSTRACT
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 ($\dot{\epsilon }_{\rm nuc}$) 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, $\dot{\epsilon }_{\rm nuc}$ is appreciably changed from those without isomers, due to the large change in timing of β− decay through the isomeric states (ISs) of ${}^{123,125,127} \rm Sn$ and ${}^{128} \rm Sb$. In particular, the effects of the isomers on $\dot{\epsilon }_{\rm nuc}$ 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 ${}^{129} \rm Sb$ and ${}^{129, 131} \rm Te$ also cause additional and appreciable change in $\dot{\epsilon }_{\rm nuc}$. 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.
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
14 articles.
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