Thirty-five Years of Timing of M53A with Arecibo and FAST

PSR B1310+18A is a 33 ms binary pulsar in a 256 day, low eccentricity orbit with a low-mass companion located in NGC 5024 (M53). In this Letter, we present the first phase-coherent timing solution for this pulsar (designated as M53A) derived from a 35 yr timing baseline; this combines the archival Arecibo Observatory data with the recent observations from the Five-hundred-meter Aperture Spherical radio Telescope. We find that the spin period derivative of the pulsar is between 6.1 and 7.5 × 10−19 s s−1, which implies a characteristic age between 0.70 and 0.85 Gyr. The timing solution also includes a precise position and proper motion for the pulsar, enabling the identification of the companion of M53A in Hubble Space Telescope data as a helium white dwarf (He WD) with a mass of MWD = 0.39-+0.070.05 M and a cooling age of 0.14-+0.030.04 Gyr, confirming that the system formed recently in the history of the globular cluster. The system resembles, in its spin and orbital characteristics, similarly wide pulsar–He WD systems in the Galactic disk. We conclude by discussing the origin of slow pulsars in globular clusters, showing that none of the slow pulsars in low-density globular clusters are as young as the systems observed in the densest known globular clusters.