SEARCH FOR VERY HIGH ENERGY GAMMA-RAYS FROMACTIVE GALACTIC NUCLEI

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Observation of AGNs : I have observed four AGNs in the energy range above several hundred GeV using CANGAROO-II 10 m telescope. For PKS2155-304, observation has been done for about 36 hours for on-source scan and about 35 hours for off-source scan including participation in the mulriwave length campaign. I have seen no evidence for persistent gamma-ray emission from PKS2155-304. Flux upper limits(2δ)is obtained to be 1.2×10^<-11>cm^<-2> sec^<-1> for above 400GeV.PKS2005-489 was observed for 33 hours for on-source scan and 31 hours for off-source scan. RXTE observation were carried out for 15 days during my observation periods in 2000. I have seen no evidence for persistent gamma-ray emission from PKS2005-489. Flux upper limit(2δ) obtained for above 450 GeV is 6.4×10^<-12> cm^<-2> sec^<-1>. During my observation periods, both targets remained in a low level state. We observed Mrk421 for ten nights during its active state in early 2001 using the very large zenith angle technique. The result shows the detection of gamma-rays from Mrk421 in the energy range above 10 TeV. Considering the absorption by extragalactic infrared photons, this implies that the energy spectrum in a high level state is very hard.Development of trigger module : In order to lower the energy threshold, I studied the trigger condition by the Monte Carlo simulation, and I found clustering trigger is very effective. Then I develop the intelligent trigger module using complimentary programmable logic device to realize the clustering trigger.