The anti-glitching gamma-ray pulsar PSR J1522-5735

TL;DR

This study analyzes over 15 years of Fermi-LAT data on the gamma-ray pulsar PSR J1522-5735, identifying eight glitch events including anti-glitches, and suggests an internal mechanism may cause spin-down glitches.

Contribution

The paper presents the first detailed detection and analysis of multiple glitch and anti-glitch events in PSR J1522-5735 using long-term gamma-ray data, revealing new insights into pulsar glitch phenomena.

Findings

Identified eight glitch events, including anti-glitches.

Glitch events were radiatively quiet with no flux or profile changes.

Internal mechanisms may drive spin-down glitch phenomena.

Abstract

Context. A small number of pulsar glitches have been identified as anti-glitches or spin-down glitches, where the overall contribution to the pulsar's rotation frequency is negative. A notable example of a spin-down glitch was observed in PSR 1522-5735, a radio-quiet gamma-ray pulsar discovered by blind searches in the 3-year data from the Fermi Large Area Telescope (LAT). Aims. This work aims to search for PSR 1522-5735's glitches using Fermi-LAT data from over 15 years of observations. Methods. The weighted H-test statistic was applied to identify glitches and evaluate the related changes in pulsar's spin parameters. The timing solution based on these results was further refined by maximization of the unbinned likelihood. The Bayesian information criterion was used to set an appropriate number of parameters in the timing solution to avoid overfitting. Results. The analysis revealed eight glitch events: regular spin-up glitch, spin-up glitch over-recovered to a spin-down and six anti-glitches. These events were radiatively quiet, exhibiting no significant variations in the shape of the pulse profile or energy flux. Conclusions. The results may suggest that an internal mechanism is responsible for spin-down glitch phenomena.