Gamma-ray source observations with the HAGAR telescope system at Hanle in the Himalayas

Abstract

We have observed Crab nebula using the recently commissioned wavefront sampling high alti- tude (4270 m) array, HAGAR, at Hanle in the Ladakh region of the Himalayas. Regular source observations have begun with the complete setup of 7 telescopes since Sept. 2008. HAGAR is the first array of atmo- spheric Cherenkov telescopes established at a so high altitude and was designed to reach a relatively low threshold with quite a low mirror area (31 m 2). Estimation of the sensitivity of the experiment is undergoing using several hours of data from the direction of Crab nebula, the standard candle source of TeV gamma-ray astronomy. Data were acquired using the On-source/Off-source mode and by comparing these sky regions the strength of the gamma-ray signal could be estimated. Gamma-ray events arrive close to telescope axis direction while the cosmic-ray background events arrive from the whole field of view. We discuss our anal- ysis procedures for the estimate of arrival direction, estimate of gamma-ray flux from Crab nebula and the sensitivity of the HAGAR system etc in this paper. Also preliminary results on blazars 1es2344+514 and Mkn421 will be presented.