S. Sahayanathan

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

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Multi-wavelength study of Mrk 421 TeV flare observed with TACTIC telescope in February 2010

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

VHE observation of Mrk 421 with TACTIC during 2012; multiwavelength study

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TeV gamma-ray Observations of the Blazar Markarian 421 from January to April 2004 with TACTIC Imaging Element

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

VHE Observations of H1426+428 using TACTIC imaging telescope : 2004

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Very High Energy Gamma-ray and Near Infrared observations of 1ES2344+514 with TACTIC and MIRO Telescopes

1 TeV energy and the time-averaged differential

VHE observations of H 1426+428 using TACTIC imaging telescope 2004 observations.

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TeV energy spectrum of the Crab nebula as measured by the TCTIC gamma-ray 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