Observations with the High Altitute GAmma-Ray (HAGAR) telescope array in the Indian Himalayas
Richard J. Britto (on behalf of HAGAR collaboration)
(Tata Institute of Fundamental Research)
For several decades, it was thought that astrophysical sources emit high energy photons within the energy range of the gamma-ray region of the electromagnetic spectrum. These photons originate from interactions of high energy particles from sources involving violent phenomena in the Universe (supernovae, pulsars, Active Galactic Nuclei, etc.) with gas and radiation fields. Since the first reliable detections of cosmic gamma rays in the 1970's, improvements in instrumentation have led gamma-ray astronomy to an established branch of modern Astrophysics, with a constant increase in the number of detected sources. But the 30-300 GeV energy range remained sparsely explored until the launch of the Fermi space telescope in June 2008. The gamma-ray telescope array HAGAR is the first array of atmospheric Cherenkov telescopes established at a so high altitude (4270 m a.m.s.l.), and was designed to reach a relatively low energy threshold with quite a low mirror area (31 m). It is located at Hanle in India, in the Ladakh region of the Himalayas. Regular source observations have begun with the complete setup of 7 telescopes on Sept. 2008. We report and discuss our estimation of the systematics through dark region studies, and present preliminary results from gamma-ray sources, etc., in this paper.
Radio follow-up of High Energy sources with the NRT. Results and on-going programs.
Martin, Theureau, Colom, Gérard et al.
(Observatoire de Paris)