Mrk 421 in a high TeV emission state during 2010: TACTIC observations
Ramesh Chand Rannot, P. Chandra, K. K. Yadav, A. K. Tickoo, K. Chanchalani, M. Kothari, K. K. Singh, N. K. Agarwal, A. Goyal, H. C. Goyal, S. Kotwal, N. Kumar, P. Marandi, K. Venugopal, C. K. Bhat, N. Bhatt, S. Bhattacharya, N. Chouhan, V. K. Dhar, S. R. Kaul, S. K. Koul, M. K. Koul, R. Koul, A. K. Mitra, S. Sahayanathan and M. Sharma
ApSD, Bhabha Atomic Researh Centre, Trombay, Mumbai, 400 085
E-mail: rcrannot@barc.gov.in

Abstract. We have observed the extragalactic TeV gamma-ray source Mrk421 (z = 0.030) in the Very High Energy (VHE) domain of gamma-rays with the TACTIC telescope. The observations were made in the tracking mode of TACTIC operation from 22nd November 2009 to 15th May 2010 and a total of 265.5 hours of the data were recorded from this source direction. Preliminary analysis of the data indicates detection of a significant TeV gamma-ray signal with a statistical significance of 9.3σ. Further, these preliminary results also indicate a variability in signal strength on a day to day basis particularly during March 2010 observations. In order to study the source at lower energies, we also compare the TACTIC TeV light curves with those of the RXTE ASM (2-12 keV), FERMI (1 GeV-300 GeV) and SWIFT(15-50 keV) obtained for the same period. Details of these preliminary results will be presented in the meeting.