Search for gamma-ray emission from magnetars with the Fermi large area telescope

Abstract

We report on the search for 0.1-10GeV emission from magnetars in 17months of Fermi LargeAreaTelescope (LAT) observations. No significant evidence for gamma-ray emission from any of the currently known magnetars is found. The most stringent upper limits to date on their persistent emission in the Fermi energy range are estimated between ∼10-12 and 10-10 erg s-1 cm-2, depending on the source.We also searched for gamma-ray pulsations and possible outbursts, also with no significant detection. The upper limits derived support the presence of a cutoff at an energy below a few MeV in the persistent emission of magnetars. They also show the likely need for a revision of current models of outer-gap emission from stronglymagnetized pulsars, which, in some realizations, predict detectableGeV emission frommagnetars at flux levels exceeding the upper limits identified here using the Fermi-LAT observations. © 2010. The American Astronomical Society. All rights reserved.