2021MNRAS.503.4908L

PSR J1420-6048 is a young γ-ray pulsar with recurrent glitches. Utilizing long-term monitoring data obtained from the Fermi Gamma-ray Space Telescope, we found that PSR J1420-6048 has shown γ-ray flux variation and we also detected four glitches between 2008 and 2019. Two of the glitches are previously unknown, and their γ-ray spectrum also shows variability between each glitch. Because the results might be contaminated by background sources, we discuss whether the observed changes in flux and spectra were caused by artificial misallocations of photons from a nearby pulsar wind nebula (HESS J1420-607) and a pulsar (PSR J1418-6058), or by a change of the emission geometry from the target pulsar itself. We examine the correlation of the flux changes and the alternating pulse structure to investigate whether the emission geometry in the outer magnetosphere was changing. By assuming that the observational features did not totally result from the background environment, we compare our results with similar phenomena observed in other γ-ray pulsars. We propose that a strong crust crack can cause timing anomaly of a neutron star, which can affect the particle accelerations or pair creation regions, resulting in the changes of emission behaviours.