Results of 15 yr Pulsar Timing of PSR J0007+7303 with Fermi-LAT

Abstract The study of pulsar glitches provides a unique window into the internal structure and dynamic processes of neutron stars. PSR J0007+7303, a very bright gamma-ray pulsar, is the first pulsar discovered by the Fermi–Large Area Telescope (LAT) telescope. In this paper, we present the 15 yr of timing results of this pulsar using the Fermi-LAT data. We identified nine glitches, five of which are newly discovered. Among these new glitches, two are small glitches, occurring between the three previously reported ones, while the other three are large glitches. The glitches exhibit fractional frequency changes ranging from 21.5 × 10 −9 to 1239 × 10 −9 , with intervals of approximately 1–2 yr between events. Uniquely, this pulsar shows no exponential recovery behavior following any glitch, setting it apart from most glitching pulsars. Furthermore, no significant changes were observed in the gamma-ray pulse profile, flux, or phase-averaged spectra before and after glitches, indicating the stability of the pulsar’s emission properties despite internal changes. A parametric analysis of the glitches yielded a fractional moment of inertia of the crustal superfluid involved in glitches as 1.06%, which matches extremely well with previous statistical work if the nondissipative entrainment effect is not considered and strongly supports the internal origin of these glitches. These results highlight the distinct glitch behavior of PSR J0007+7303 and offer valuable insights into the crust–superfluid interaction in neutron stars. The physical origin of no exponential recovery is also discussed.