The TACTIC atmospheric Cherenkov Imaging telescope

Abstract

The TACTIC $\gamma$-ray telescope, equipped with a light collector of area $\sim$9.5m${}^2$ 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 2-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$\times$11 pixels ($\sim$ 3.4${}^{\circ }$$\times 3.4^{\circ }$), the telescope records a cosmic ray event rate of $\sim$2.5 Hz at a typical zenith angle of 15${}^{\circ }$. 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 $\sim$1.2 TeV energy, at a sensitivity level of $\sim 5.0\sigma$ in $\sim$25 h, 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 $\gamma$-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 $\gamma$-ray emission activity from other active galactic nuclei on a long term basis.

27 pages, 13 figures, accepted for publication in NIM A

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Cited by in corpus (19)

• Artificial Neural Network-based error compensation procedure for low-cost encoders
• Ground-based gamma-ray astronomy: history and development of techniques
• ANN-based energy reconstruction procedure for TACTIC gamma-ray telescope and its comparison with other conventional methods
• Multiwavelength study of VHE emission from Markarian 501 using TACTIC observations during April-May, 2012
• Very High Energy gamma-ray observations of Mrk 501 using TACTIC imaging gamma-ray telescope during 2005-06
• A time dependent approach to model X-ray and $\gamma$--ray light curves of Mrk 421 observed during the flare in February 2010
• TeV Gamma-ray Observations of Markarian 421 using TACTIC during 2009-10
• Multi-wavelength study of Mrk 421 TeV flare observed with \emph{TACTIC} telescope in February 2010
• Study of short term enhanced TeV $\gamma$- ray emission from Mrk 421 observed with TACTIC on December 28, 2014
• Validation of a new background discrimination method for the TACTIC TeV $\gamma$-ray telescope with Markarian 421 data
• Search for TeV $\gamma$--ray emission from blazar 1ES1218+304 with TACTIC telescope during March-April 2013
• Feasibility of utilizing Cherenkov Telescope Array gamma-ray telescopes as free-space optical communication ground stations
• Simulation studies for optimizing the trigger generation criteria for the TACTIC telescope
• Artificial Neural Network based gamma-hadron segregation methodology for TACTIC telescope
• Search for TeV $\gamma$ -rays from H1426+428 during 2004-07 with the TACTIC telescope
• Search for diffuse cosmic gamma-ray flux using Fractal and Wavelet analysis from Galactic region using single imaging Cerenkov telescopes
• Cosmic-ray composition with TACTIC telescope using Fractal and Wavelet Analysis
• A Site Evaluation Campaign for a Ground Based Atmospheric Cherenkov Telescope in Romania
• Contributions to free-space optical communications: feasibility of utilizing Cherenkov telescopes as receivers and beam-wander correction in quantum communications