GAMMA-RAY UPPER LIMITS ON MAGNETARS WITH SIX YEARS OF FERMI-LAT OBSERVATIONS

Abstract

ABSTRACT We report on the search for gamma-ray emission from 20 magnetars using six years of Fermi Large Area Telescope 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 ∼10−12 and 10−11 erg s−1 cm−2. We searched gamma-ray pulsations for the four magnetars having reliable ephemerides over the observing period, but detected none. We also report updated morphologies and spectral properties of seven spatially extended gamma-ray sources, which are most likely attributed to supernova remnants associated with or adjacent to the magnetars.