Gamma-ray upper limits on magnetars with 6 years of Fermi-LAT observations

TL;DR

This study used 6 years of Fermi-LAT data to search for gamma-ray emission from 20 magnetars, setting the most stringent upper limits to date and finding no significant gamma-ray signals.

Contribution

It provides the first comprehensive gamma-ray upper limits on magnetars with extensive Fermi-LAT data, including searches for pulsations and analysis of associated supernova remnants.

Findings

No significant gamma-ray emission detected from any magnetars.

Established the most stringent upper limits on 0.1--10 GeV emission.

No gamma-ray pulsations found in magnetars with known ephemerides.

Abstract

We report on the search for gamma-ray emission from 20 magnetars using 6 years of Fermi, Large Area Telescope (LAT) observations. No significant evidence for gamma-ray emission from any of the currently-known magnetars is found. We derived the most stringent upper limits to date on the 0.1--10 GeV emission of Galactic magnetars, which are estimated between $\sim10^{-12}-10^{-11}$ erg s$^{-1}$ cm$^{-2}$. Gamma-ray pulsations were searched for the four magnetars having reliable ephemerides over the observing period, but none were detected. On the other hand, we also studied the gamma-ray morphology and spectra of seven Supernova Remnants associated or adjacent to the magnetars.