Magnetar counterparts, kinematics, and birth sites with HST and JWST

Aims. Magnetars are highly magnetised, isolated neutron stars with uncertain formation channels. They comprise a potentially significant fraction of the young neutron star population in the Milky Way and are implicated in the explosion mechanisms of some of the most powerful explosions in nature. We aim to identify magnetars in the near-infrared with Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) imaging in order to measure their proper motions and search for their birth sites. Methods. Candidate infrared counterparts were selected based on variability, colours, and proper motions, which are outliers with respect to other sources in the field. Precise proper motions were obtained by tying HST/WCF3 and JWST/NIRcam images to the Gaia absolute astrometric reference frame. Results. We identify new infrared counterpart candidates for PSRJ1622−4950, 1RXSJ 170849.0-400910, and CXOUJ164710.2-455216, representing a substantial increase in the population. Results. The past trajectory of the 1RXSJ 170849.0-400910-associated source coincides with the supernova remnant G346.6-0.2. The transverse velocity distribution of magnetars is found to be marginally inconsistent with that of young pulsars, due primarily to a dearth of high velocity magnetars. A candidate birth site is identified inside the cone of possible past trajectories in nearly every case. We show, based on the inferred kinematic ages, that magnetar characteristic ages may frequently be lower than the true age but caution that this result depends on the reliability of the birth site associations. Conclusions. We conclude that magnetars are broadly similar to the wider Galactic neutron star population in terms of their kinematics and birth sites, consistent with magnetar formation being a common outcome of massive star core collapse. However, we find tentative evidence for a dearth of high-velocity magnetars. If real, this may arise from physical differences in the progenitor population giving rise to magnetars or from differences in their post-formation velocity evolution.