Abstract
Pulsars are usually known as steady sources in gamma-ray sky. However, the discovery of the first variable gamma-ray pulsar PSR J2021+4026 challenges our understanding to pulsar astronomy. We here present the results of a detailed analysis of ∼ 7 years of Fermi-LAT data of the variable gamma-ray pulsar candidate, PSR J0248+6021, a rotation-powered pulsar located in a dense gas cloud region with two glitches after the Fermi satellite being launched. We found spectral variation before and after the first glitch and a marginal change in its rotational light curve (pulse profile). To inspect the origin of the spectral change, phase-resolved spectral analysis have been performed while the results show the origin might be due to a weak detection of off- pulse emission during the period before the first glitch (P1). We conclude that no significant variation of pulsar properties of PSR J0248+6021 has been observed to be associated with glitches. For the unpulsed emission, in previous works, a potential pulsar wind nebula (PWN) has been proposed on the basis of extended feature in op- tical wavelengths, and hence we performed spatial analysis with Fermi-LAT data and revisited the X-ray observation from Chandra. PSR J0248+6021 is an underluminous X-ray pulsar with a soft powerlaw spectrum obtained in gamma-ray regime seemingly weaken the possibility PWN. Spectral changes and flux variability associated with pulsar irregularities have been found in radio and X-ray energy bands, while to date, only PSR J2021+4026 is claimed as a variable gamma-ray pulsar showing different modes before and after a significant flux jump. The intrinsic origin of the flux jump occurred in PSR J2021+4026 is still unclear, searching for more pulsar behaving in this way would help us understand the gamma-ray pulsar emission mechanism.