Californium-254 and kilonova light curves

TL;DR

This paper identifies the isotope Californium-254 as a key contributor to the brightness of kilonova light curves from neutron star mergers, especially in the 15-250 day range, due to its long half-life and fission properties.

Contribution

It highlights the significant impact of Californium-254 on kilonova light curves and outlines conditions under which it influences electromagnetic transients.

Findings

Californium-254 significantly affects kilonova brightness between 15-250 days.

Fission of Californium-254 contributes to thermalization efficiency in light curves.

Future IR observations could confirm actinide nucleosynthesis in mergers.

Abstract

Neutron star mergers offer unique conditions for the creation of the heavy elements and additionally provide a testbed for our understanding of this synthesis known as the $r$-process. We have performed dynamical nucleosynthesis calculations and identified a single isotope, $^{254}$Cf, which has a particularly high impact on the brightness of electromagnetic transients associated with mergers on the order of 15 to 250 days. This is due to the anomalously long half-life of this isotope and the efficiency of fission thermalization compared to other nuclear channels. We estimate the fission fragment yield of this nucleus and outline the astrophysical conditions under which $^{254}$Cf has the greatest impact to the light curve. Future observations in the middle-IR which are bright during this regime could indicate the production of actinide nucleosynthesis.