A Candidate Open Cluster Pulsar: Timing Analysis of PSR J1922+3745 in NGC 6791

PSR J1922+3745 was recently identified as a radio pulsar toward the old open cluster NGC 6791, raising the prospect of the first pulsar associated with an open cluster. We report Five-hundred-meter Aperture Spherical radio Telescope follow-up observations that yield a phase-coherent timing solution, a precise position, a measurement of the spin-down rate and the pulsar’s polarization properties. PSR J1922+3745 is consistent with an isolated slow pulsar with P = 1.9 s and P ̇ ∼ 3.9 × 1 0 − 15 s s −1 , giving a characteristic age of 7.8 Myr, which is comparable to the small population of long-period pulsars found in globular clusters. Motivated by the potential cluster association we conduct deeper searches of the NGC 6791 field but detect no additional pulsars. We also assess whether H I absorption spectroscopy can provide a useful distance constraint and find that such measurements are unlikely to be constraining with currently available sensitivity. Consequently, existing evidence does not yet establish membership in NGC 6791. Further deep searches for additional pulsars with similar dispersion measures in the cluster field will likely be the most direct path to confirming a physical association.