The dependence of the lateral distribution of Cherenkov light in simulated extensive air showers to the energy and the mass of the primary cosmic rays has been studied. It has been shown that a previous claim about mass independent proportionality of shower energy to the total Cherenkov photon number is not valid in energies below EEAS ~ 1014 eV. We have found that the core distance of the so c...

The Cherenkov Telescope Array (CTA) is an initiative to build the next generation, ground-based gamma-ray observatories. We present a prototype workspace developed at INAF that aims at providing innovative solutions for the CTA community. The workspace leverages open source technologies providing web access to a set of tools widely used by the CTA community. Two different user interaction model...

The H.E.S.S. Imaging Atmospheric Cherenkov Telescope Array is currently the most sensitive instrument for Very High Energy (VHE) γ-ray observations in the energy range of about 0.1-10 TeV. During more than two years of operation with the complete 4-telescope array, many galactic and extragalactic VHE γ-ray sources have been discovered. With its superior sensitivity and its large field-of-view c...

We report our observations on 4 AGNs viz, Mkn421, Mkn501, 1ES1426+428 and ON231 belonging to a sub-class called blazars. The observations were carried out using the Pachmarhi Array of Cherenkov Telescopes and span about 6 years period from 2000 to 2005. We discuss our methods of analysis adopted to extract the gamma ray signal from cosmic ray background. We present our results on the emission o...

The energy spectrum of cosmic rays in the range E ∼ 1015 eV to 6 × 1019 eV has been studied using the air Cherenkov light detectors of the Yakutsk array. The total flux of photons produced by relativistic electrons (including positrons as well, hereafter) of extensive air showers in the atmosphere is used as the energy estimator of the primary particle initiating a shower. The resultant differe...

The current generation of Cherenkov telescopes is mainly limited in their gamma-ray energy and flux reconstruction by uncertainties in the determination of atmospheric parameters. The Cherenkov Telescope Array (CTA) aims to provide high-precision data extending the duty cycle as much as possible. To reach this goal, it is necessary to continuously and precisely monitor the atmosphere by means o...

Abstract The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of four 12 m Atmospheric Cherenkov Telescopes (IACTs), located at the Fred Lawrence Whipple Observatory in Arizona, USA, that has been full operation since 2007. VERITAS conducts research a variety areas including galactic science such as supernova remnants, pulsar wind nebulae, binary systems; extra-gala...

The lateral distribution of particles in extensive air showers from cosmic rays with energy above $10^{17}$ eV registered at the Yakutsk complex array was analyzed. Experimentally measured particle densities were compared to predictions obtained within frameworks three ultra-high hadron interaction models. ray mass composition estimated by readings surface-based and underground detectors is con...

VERITAS is a system of four imaging Cherenkov telescopes located at the Fred Lawrence Whipple Observatory in southern Arizona. We present here results of detailed Monte Carlo simulations of the array response to extensive air showers. Cherenkov image and shower parameter distributions are calculated and show good agreement with distributions obtained from observations of background cosmic rays ...