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

Abstract

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 Eγ ⩾ 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.