RECENT OBSERVATIONS OF VHE GAMMA-RAYS FROM CYGNUS-X-3

Our observations of Cygnus X-3 in 1981-88 have suggested that sporadic 12.6 ms pulsed very high energy gamma rays are produced at or near the maximum (phase 0.6) in the 4.8 h x-ray cycle. Cygnus X-3 was observed with the Durham University Mark IV Northern Hemisphere gamma-ray telescope in 1989, shortly after two radio outbursts were detected from the object. An analysis of these data suggests that 12.6 ms pulsar emission may be observed at a phase in the 4.8 h cycle some 1000 s before our prediction from previous measurements. This is in agreement with measurements made at Woomera by the University of Adelaide. More recent observations using the Mark III Southern Hemisphere telescope at large zenith angles have not provided any further evidence for pulsar activity.