Near IR Astrometry of Magnetars

Abstract

We report on the progress of our five-year program for astrometric monitoring of magnetars using high-resolution NIR observations using the laser guide star adaptive optics (LGS-AO) supported NIRC2 camera on the 10-meter Keck telescope. We have measured the proper motion of two of the youngest magnetars, SGR 1806–20 and SGR 1900+14, which have counterparts with K ~21 mag, and have placed a preliminary upper limit on the motion of the young AXP 1E 1841–045. The precision of the proper motion measurement is at the milliarcsecond per year level. Our proper motion measurements now provide evidence to link SGR 1806–20 and SGR 1900+14 with neighboring young star clusters. At the distances of these magnetars, their proper motion corresponds to transverse space velocities of 350 ± 100 km s^(−1) and 130 ± 30 km s^(−1) respectively. The upper limit on the proper motion of AXP 1E 1841–045 is 160 km s^(−1). With the sample of proper motions available, we conclude that the kinematics of the magnetar family are not distinct from that of pulsars.

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