Studying the gamma-ray properties of glitching pulsars

Abstract

Pulsars are highly magnetized rotating neutron stars and radiate beams of emission that are observed as pulses when they sweep across the Earth. Most times the stable rotation can be well described by a simple model spaning many years with an accuracy of a few microseconds or better. Glitch, as a main type of timing irregularity observed for radio pulsars, is usually characterized by a sudden increase in rotation speed followed by a secular relaxation. Although glitch events are frequently observed, their origin is still unclear. In this thesis, I investigate the influence of glitch on high-energy emission from gamma-ray pulsars. Through a comparison of flux, spectrum and pulse shape before and after glitch, I try to understand the possible scenario for glitch. The gamma-ray flux change induced by glitch was seldom reported before except for PSR J2021+4026. Thus I first briefly review the results for this pulsar and its implication for the cause of glitch. Then several pulsars with strong gamma-ray emission and known ephemeris are selected from Fermi catalog to be analyzed with the Fermi Science Tools. I find only PSR J1420-6048 shows evidence of flux variation during glitch. However this flux change is suspected to be induced by a nearby pulsar PSR J1418-6058 which is only $0.24^{\circ}$ away. To minimize the contamination we apply a gating technique based on the light curve of PSR J1418-6058, and find there are still flux variations after gating. Then we continue to compare the spectrum and pulse profile, and find the spectrum shows a significant change during glitch while light curve is almost the same. At last we try to extend the timing model for PSR J1418-6058, and find another glitch from the gamma-ray emission.