Energy Sensitive Search for Pulsed Photons from Crab Pulsar using the TACTIC Imaging Element

Abstract

The Imaging Element (IE) of the 4-element TACTIC array of atmospheric Cherenkov telescopes is in operation at Mt. Abu Rajasthan, in Western India. We have successfully detected a steady signal from the Crab Nebula at a sensitivity level of ~ 6.3 in 40 hours at E 1 TeV, during the period Jan.- March 2001. This database has been used to carry out a search for the presence of pulsed photons at two higher threshold energies (E 2 TeV and E 3 TeV) by applying energy - sensitive size cuts. We do not find any evidence for the presence of an energy- dependent pulsed photon signal from the Crab pulsar direction. However, we place the upper limits of 1.08 x 10-12 and 8.88 x 10-13 photons cm-2 sec-1 for the 2TeV and 3TeV light curves respectively. Results presented here, are however preliminary and we are collecting more data on the source so as to be able to arrive at a more definitive conclusion about the TeV -ray pulsed emission from the Crab pulsar.