TeV gamma-ray observations of Markarian 421 using TACTIC during 2009-10

We have observed the blazar Markarian 421 with the TACTIC γ-ray telescope at Mt. Abu, India, from 22 November 2009 to 16 May 2010 for 265 h. Detailed analysis of the data so recorded revealed the presence of a TeV γ-ray signal with a statistical significance of 12.12σ at E_γ ⩾ 1 TeV. We have estimated the time-averaged differential energy spectrum of the source in the energy range 1.0-16.44 TeV. The spectrum fits well with the power-law function of the form (dF/dE = f₀E^-Γ) with f₀ = (1.39 ± 0.239) × 10^-11 cm^-2 s^-1 TeV^-1 and Γ = 2.31 ± 0.14.