High Energy Emission Mechanism in Mode Changing Pulsars

The radio and γ-ray beams are generally interpreted as inner and outer gap emission, respectively, with the two gaps being connected by magnetic field lines. Therefore, we expect that some MCPs may undergo mode variations both in the radio and γ-ray bands. In this thesis, we studied the two young γ-ray MCPs, PSR J0742-2822 and PSR J1105-6107. They were extensively observed both in the radio and γ-ray bands in the past decades. We first analyzed the radio observations made with the 64-m radio telescope at Parkes Observatory (PKS) in the radio band and found that the radio emission of the two pulsars undergoes variations both on the short term and on the long term. Then we analyzed the observations made with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) in the γ-ray band, and found that the γ-ray emission can also change with the radio emission. In perticular, a transient inter pulse (IP) appears in the γ-ray profile when one of the components of the radio profile shows enhancement. This suggests that the radio and γ-ray emission regions may be connected to the same magnetic field lines, and that studying their variable emission could provide a good constraint on the emission height in the γ-ray band. Finally, we investigated the relationship between glitches and radio state changes. We found that all the 6recent glitches (G3-G8) of the pulsar PSR J0742-2822 occurred during 4 highly periodic (high-Q) states and that 2 recent glitches (G4, G5) of the pulsar PSR J1105-6107 occurred during an emission state in which the second component (C2) of the pulse is occasionally weaker than the first one (C1). These states usually appeared∼100 d, so we called them pre-glitch emission variations. We speculated that these pre-glitch emissions are caused by crust variations of neutron stars. The appearance of the special state of the neutron star crust not only changed the gap-sparking mode in the inner gap of pulsars but also reduced the threshold at which the glitch occurs.