Nucleosynthesis in outflows of compact objects and detection prospects of associated kilonovae

Kavli Affiliate: Shunsaku Horiuchi

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| Summary:

We perform a comparative analysis of nucleosynthesis yields from binary
neutron star (BNS) mergers, black hole-neutron star (BHNS) mergers, and
core-collapse supernovae (CCSNe) with the goal of determining which are the
most dominant sources of r-process enrichment observed in stars. We find that
BNS and BHNS binaries may eject similar mass distributions of robust r-process
nuclei post merger (up to 3rd peak and actinides, $Asim200-240$), after
accounting for the volumetric event rates. Magnetorotational (MR) CCSNe likely
undergo a weak r-process (up to $Asim140$) and contribute to the production of
light element primary process (LEPP) nuclei, whereas typical thermal,
neutrino-driven CCSNe only synthesize up to 1st r-process peak nuclei
($Asim80-90$). We also find that the upper limit to the rate of MR CCSNe is
$lesssim1%$ the rate of typical thermal CCSNe; if the rate was higher, then
weak r-process nuclei would be overproduced. Although the largest uncertainty
is from the volumetric event rate, the prospects are encouraging for confirming
these rates in the next few years with upcoming surveys. Using a simple model
to estimate the resulting kilonova light curve from mergers and our set of
fiducial merger parameters, we predict that $sim7$ BNS and $sim2$ BHNS events
will be detectable per year by the Vera C. Rubin Observatory (LSST), with prior
gravitational wave (GW) triggers.

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