We report on our Galactic plane searches for magnetars in the archival Chandra X-ray Observatory (CXO) data. We summarize the properties of known magnetars and use them to establish a procedure for magnetar searches. The procedure includes four steps: source finding, spectral characterization, optical counterpart checks, and period searches. We searched 1,282 archival CXO observations, found 32,838 X-ray sources, and selected 25 intriguing candidates using the developed procedure. Although we do not firmly identify a magnetar among them, we significantly reduced the number of targets in future magnetar searches to be done with better X-ray telescopes.

Anomalous X-ray pulsars (AXPs) are thought to be magnetars which are young isolated neutron stars with extremely strongmagnetic fields of >1014 Gauss. Their tremendous magnetic fields inferred from the spin parameters provide a huge energyreservoir to power the observed X-ray emission. High-energy emission above 0.3 MeV has never been detected despiteintensive search. Here, we present the possible Fermi Large Area Telescope (LAT) detection of γ-ray pulsations above 200MeV from the AXP, 1E 2259+586, which puts the current theoretical models of γ-ray emission mechanisms of magnetars intochallenge. We speculate that the high-energy γ-rays originate from the outer magnetosphere of the magnetar.