TeV astronomy of millisecond pulsars

Abstract

This thesis is concerned with the detection of pulsed TeV γ-rays from millisecond pulsars. These stars appear to include some very efficient producers of high energy particles, but the mechanisms by which they produce TeV γ-rays are still a matter of debate. After an introductory section, there is a brief description of the principles used in the atmospheric Cerenkov technique. The design and operation of the University of Durham atmospheric Cerenkov telescopes are reviewed. The main analysis techniques used to search for periodic signals are then described. The effects on periodic signals of binary motion of a source are discussed. These are a particularly important consideration for observations of millisecond pulsars, where high timing accuracy is required. One of the problems of detecting TeV sources is the cosmic ray background. A means of rejecting background events in TeV γ -ray telescopes is considered in chapter 5. The technique is developed for the Durham Mark III telescope. Substantial rejection of the cosmic ray background is achieved, with minimal loss of source events. The evolutionary scenarios which lead to the formation of millisecond pulsars are outlined. Two models for 7-ray emission are discussed briefly and applied to six known millisecond pulsars. Empirical results on these and two other pulsars are also presented. In particular, a detection of PSR 1855+09 is reported, and an upper limit to the flux from PSR 1957+20 is derived. All the empirical fluxes are compatible with the emission models, but the 'polar gap' model may be favoured. The final chapter summarises the results obtained and suggests some directions for future work on the 7-ray emission from millisecond pulsars.