2025ApJ...988..218H

In this paper, we present the first direct measurement of the proper motion of the neutron star (NS) in the supernova remnant (SNR) G18.9-1.1 using a 15 yr Chandra baseline. After correcting the observations' astrometric solutions using reference Gaia stars' positions, we measure a total proper motion of 24.7 ± 6.8 mas yr^–1 at an angle of 336° ± 16° east of north. Using the distance estimates from the literature of 2.1 and 3.8 kpc, this proper motion corresponds to Galactic rotation-corrected transverse velocities of 264d_2.1 ± 79 km s^–1 and 474d_3.8 ± 129 km s^–1, respectively. Our power ratio method analysis of SNR ejecta slightly favors the higher velocity, as multipole moments calculated from the back-evolved center using the farther distance are more consistent with values from other CCSNRs. The NS's motion is directly opposite the motion of bulk ejecta in G18.9-1.1, providing yet more evidence that NS kicks are generated via a conservation of momentum-like process between the NS and the ejecta, as has been observed in other SNRs.