Gamma-rays from kilonovae and the cosmic gamma-ray background

TL;DR

This paper calculates the gamma-ray contribution of kilonovae to the cosmic background, finding it is not dominant but could help explain observational data within current uncertainties.

Contribution

It provides the first detailed estimate of kilonovae's gamma-ray contribution to the MeV background using recent spectral data.

Findings

Kilonovae contribute a minor fraction to the MeV gamma-ray background.

Their contribution could help fit observational data within existing uncertainties.

Kilonova gamma-ray spectra are characterized and compared with other sources.

Abstract

The recent detection of the gravitational wave event GW170817, produced by the coalescence of two neutron stars, and of its optical-infrared counterpart, powered by the radioactive decay of r-process elements, has opened a new window to gamma-ray astronomy: the direct detection of photons coming from such decays. Here we calculate the contribution of kilonovae to the diffuse gamma-ray background in the MeV range, using recent results on the spectra of the gamma-rays emitted in individual events, and we compare it with that from other sources. We find that the contribution from kilonovae is not dominant in such energy range, but within current uncertainties, its addition to other sources might help to fit the observational data.