511 keV line constraints on feebly interacting particles from supernovae

TL;DR

This paper uses observations of the 511 keV gamma-ray line to set new constraints on feebly interacting particles like sterile neutrinos and dark photons produced in supernovae, improving previous bounds significantly.

Contribution

It introduces a novel method of constraining feebly interacting particles by analyzing the 511 keV line flux from the Galactic center, surpassing previous energy-loss bounds from supernovae.

Findings

New bounds on sterile neutrino mixing parameters

Enhanced constraints on dark photon properties

Improved limits compared to SN 1987A energy-loss arguments

Abstract

Feebly interacting particles with masses with O(10-100) MeV can be copiously produced by core-collapse supernovae (SNe). In this paper we consider the case of MeV-ish sterile neutrinos and dark photons mixed with ordinary neutrinos and photons, respectively. Furthermore, both sterile neutrinos and dark photons may decay into positrons on their route to Earth. Such positrons would annihilate with electrons in the Galactic medium and contribute to the photon flux in the 511 keV line. Using the SPI (SPectrometer on INTEGRAL) observation of this line improves the bounds on the mixing parameters for these particles by several orders of magnitude below what is already excluded by the SN 1987A energy-loss argument.