PSR J1922+37: a 1.9-second pulsar discovered in the direction of the old open cluster NGC 6791

TL;DR

This paper reports the discovery of a 1.9-second pulsar in the open cluster NGC 6791 using FAST, marking the first potential pulsar found in an open cluster, with implications for future pulsar searches.

Contribution

First discovery of a pulsar in an open cluster, demonstrating the potential of FAST for such searches and opening new avenues in pulsar astronomy.

Findings

Discovered a 1.9-second pulsar in NGC 6791

Estimated the pulsar's distance consistent with cluster membership

Outlined future observations to confirm cluster association

Abstract

More than 300 pulsars have been discovered in Galactic globular clusters; however, none have been found in open clusters. Here we present results from 20-hour pulsar searching observations in seven open clusters with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our first discovery is a 1.9-second pulsar (J1922+37) found in the direction of the old open cluster NGC 6791. The measured dispersion measure (DM) implies a distance of 4.79 kpc and 8.92 kpc based on the NE2001 and YMW16 electron density models, respectively. Given the large uncertainty of DM distance estimates, it is likely that PSR J1922+37 is indeed a member of NGC 6791, for which the distance is $4.19\pm0.02$ kpc based on Gaia Data Release 3. If confirmed, PSR J1922+37 will be the first pulsar found in Galactic open clusters. We outline future observations that can confirm this pulsar-open cluster association and discuss the general prospects of finding pulsars in open clusters.