Abstract
Magnetars are a category of neutron stars with unusually high magnetic fields on their surface. Frequent starquakes on magnetars lead to their recurrent X-ray outbursts. The positions of magnetars are commonly coincident with supernova remnants (SNRs). While SNRs have been confirmed to be a kind of luminous gamma-ray sources, none of our known magnetars have been seen at energies above several hundred kiloelectronvolts (keV). Therefore, although Fermi Large Area Telescope (LAT) detected two bright gigaelectronvolt (GeV)-clumps respectively in the regions of magnetars SGR 1806-20 and 1E 1841-045, we need to constrain the gamma-ray contribution from their associated and/or adjacent SNRs before claiming discoveries of gamma-ray excess originated from magnetars. It is also important to search for correlation between the X-ray outburst history of a magnetar and the gamma-ray flux in its region. For the SGR 1806-20 region, we speculate the existence of a PWN powered by the magnetic-field decay of the magnetar and it may dominate the emission above several GeV. In the 1E 1841-045 region, the magnetar is seemingly a necessary and sufficient source for the gamma-ray emission below 10 GeV.