A pulsar escaping from an open cluster: origin of neutron stars in the Milky Way Disk

Open clusters (OCs) are the primary contributors to the native stellar population of the Milky Way disk. Neutron stars (NSs) -- remnants of massive stars -- in the disk should also originate from OCs, along with the resulting pulsars. However, no NS associated with any OC has been validated, presumably due to high-velocity kicks, exceeding the OC's escape velocity, imparted by supernova explosions. We have achieved arcsec-level localization (~1/1000 of the OC's tidal radius) to place the newly found pulsar PSR J1921+3745 in the tidal tail as well as near the tidal radius edge of NGC 6791, one of the oldest and most massive Galactic OCs. Our N-body simulation shows that, for an OC like NGC 6791, a substantial fraction of NSs with low-velocity kicks, peaking around 3 km/s in our calculation, remain in the cluster's tidal tails. The radio PSR J1921+3745 in the cluster tidal tail thus represents a snapshot of an escaping NS from an OC to the Galactic disk field. Further identification and characterization of pulsars associated with OCs are crucial to probe the origin of Galactic disk neutron stars and their co-evolution with the clusters.