Improved limits on sterile neutrino dark matter from full-sky observations by the Fermi-GBM

TL;DR

This study uses Fermi-GBM data to search for sterile neutrino decay lines in the 10-25 keV range, setting new constraints on sterile neutrino properties and surpassing previous limits.

Contribution

First application of Fermi-GBM for sterile neutrino decay line search in 10-25 keV range, providing improved limits on sterile neutrino mixing angles.

Findings

No significant decay lines detected.

Set new upper limits on sterile neutrino mixing angles.

Demonstrated GBM's capability for dark matter searches.

Abstract

For the first time, we use the Gamma-ray Burst Monitor (GBM) on-board the Fermi satellite to search for sterile neutrino decay lines in the energy range 10-25 keV corresponding to sterile neutrino mass range 20-50 keV. This energy range has been out of reach of traditional X-ray satellites such as Chandra, Suzaku, XMM-Newton, and gamma-ray satellites such as INTEGRAL. Furthermore, the extremely wide field of view of the GBM opens a large fraction of the Milky Way dark matter halo to be probed. We start with 1601 days worth of GBM data, implement stringent data cuts, and perform two simple line search analyses on the reduced data: in the first, the line flux is limited without background modeling, and in the second, the background is modeled as a power-law. We find no significant excess lines in both our searches. We set new limits on sterile neutrino mixing angles, improving on previous limits by approximately an order of magnitude. Better understanding of detector and astrophysical backgrounds, as well as detector response, can further improve the limit.