Observations of southern hemisphere gamma ray emitting blazars

Abstract

This thesis details observations of three Southern hemisphere blazars PKS 2155-304 PKS 2005-489 and PKS 0548-322 using the University of Durham Mark 6 Telescope between 1996 and 1999. The nature of blazars and the physical processes responsible for very high energy emission are also discussed. A signal above 700 GeV was observed from PKS 2155-304 between 1996 and 1997 but not in 1998 and 1999. One plausible explanation for this is a reduction in sensitivity of the Mark 6.Evidence for variability of high energy emission from PKS 2155-304 was search for but no firm conclusion was reached. Upper limits to emission from PKS 2005-489 and PKS 0548-322 were determined. Gamma ray observations for all three objects were tested for correlation with near simultaneous 2-10 keV X-ray emission (taken using the ASM onboard RXTE). No strong evidence for correlation was found. It is worth noting however that gamma ray emission from PKS 2155-304 was detected when the X-ray emission was greatest. No constraints could be made on models of gamma ray production from blazars. No models were excluded. Future observations with the new generation of gamma ray telescopes such as H.E.S.S. and CANGAROO will allow more detailed investigation of these objects and many others and their variability while multiwavelength observations will determine the nature of the acceleration processes at work.