Very high energy gamma rays from the crab pulsar
The Ooty data on VHE (> 600 GeV) γ-rays from the Crab pulsar have been used to look at possible emission on three different timescales,viz. years, minutes and hours. When averaged over three years of observation, there is no significant time-averaged emission. But interesting aspects are revealed when the data are subdivided into miniruns of one-minute duration. Minutes with moderate γ-ray activity were isolated with a κ2 analysis. The summed phasogram of such minutes shows two strong peaks coinciding with the radio main pulse and the interpulse respectively. The probability that these are due to chance is small. The phasogram has a bimodal distribution which indicates some emission from the middle region between the two phases. In general, there is no significant emission on the timescale of a few hours. However, the main pulse, as well as the bimodal distribution, were seen also in the total data of two nights of simultaneous observation at two sites during 1984–1985.
Volume 40 | Issue 3
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