M. K. Koul

The TACTIC atmospheric Cherenkov imaging telescope

The TACTIC (TeV Atomospheric Cherenkov Telescope with Imaging Camera) γγ-ray telescope, equipped with a light collector of area ∼9.5m2 and a medium resolution imaging camera of 349 pixels, has been in operation at Mt. Abu, India, since 2001. This paper describes the main features of its various subsystems and its overall performance with regard to (a) tracking accuracy of its two-axes drive system, (b) spot size of the light collector, (c) back-end signal processing electronics and topological trigger generation scheme, (d) data acquisition and control system and (e) relative and absolute gain calibration methodology. Using a trigger field-of-view of 11×1111×11 pixels (∼3.4∘×3.4∘)(∼3.4∘×3.4∘), the telescope records a cosmic ray event rate of ∼2.5Hz at a typical zenith angle of 15∘15∘. Monte Carlo simulation results are also presented in the paper for comparing the expected performance of the telescope with actual observational results. The consistent detection of a steady signal from the Crab Nebula above ∼1.2TeV energy, at a sensitivity level of ∼5.0σ∼5.0σ in ∼25h, alongwith excellent matching of its energy spectrum with that obtained by other groups, reassures that the performance of the TACTIC telescope is quite stable and reliable. Furthermore, encouraged by the detection of strong γγ-ray signals from Mrk 501 (during 1997 and 2006 observations) and Mrk 421 (during 2001 and 2005–2006 observations), we believe that there is considerable scope for the TACTIC telescope to monitor similar TeV γγ-ray emission activity from other active galactic nuclei on a long-term basis.

Observations of TeV γ-rays from Mrk 421 during December 2005 to April 2006 with the TACTIC telescope

The TACTIC

TeV observations of Mrk 421 with the TACTIC γ-ray telescope during 2006-8

\gamma

Very high energy γ-ray observations of Mrk 501 using the TACTIC imaging γ-ray telescope during 2005 06

-ray telescope has observed Mrk 421 on 66 clear nights from Dec. 07, 2005 to Apr. 30, 2006, totalling

Very high energy γ-ray and near infrared observations of 1ES2344+514 during 2004–05

\sim

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

202 hours of on-source observations. Here, we report the detection of flaring activity from the source at

Search for TeV γ-rays from H1426+428 during 2004–2007 with the TACTIC telescope

\geq

Simulation studies for optimizing the trigger generation criteria for the TACTIC telescope

1 TeV energy and the time-averaged differential

Artificial Neural Network based γ-hadron segregation methodology for TACTIC telescope

\gamma

Artificial Neural Network based segregation methodology for TACTIC telescope

-ray spectrum in the energy range 1-11 TeV for the data taken between Dec. 27, 2005 to Feb. 07, 2006 when the source was in a relatively higher state as compared to the rest of the observation period. Analysis of this data spell, comprising about