Astron. Astrophys. Suppl. Ser.
Volume 143, Number 3, May I 2000
|Page(s)||535 - 539|
|Published online||15 May 2000|
Feasibility study of an absolute energy calibration of imaging atmospheric Cherenkov telescopes by starlight*
Institut für Experimentelle und Angewandte Physik, Leibnizstr. 19, 24118 Kiel, Germany
Send offprint request to: O. Karschnick, e-mail: Oliver.Karschnick@desy.de
Accepted: 20 January 2000
A new method is presented for an absolute energy calibration of imaging atmospheric Cherenkov telescopes as a whole instrument at all relevant wavelengths. For this study the Cherenkov telescope #1 of the HEGRA experiment was used. The calibration was carried out by detecting the light of different selected stars during one night. From the data a simple linear correlation was derived between the anode current of the Cherenkov camera photomultiplier tubes and the incident photon flux. This result is important for the imaging air Cherenkov technique in several aspects: The method enables to determine the response function of Cherenkov telescopes in the energetic range of Cherenkov light quickly and reliably. Therefore it can be used as an atmospheric calorimeter by measuring the absolute integrated flux of Cherenkov photons. Moreover, the signal of a point run can be predicted and a simulation of the apparatus response can be carried out more reliably.
Key words: telescopes / methods: observational / stars: general / cosmic rays
The High Energy Gamma Ray Astronomy experiment is operated on La Palma (Canary Island) by the HEGRA collaboration formed by the University of Hamburg, Max-Planck Institut für Kernphysik, Heidelberg, University of Kiel, University of Madrid, Max-Planck Institut für Physik, Munich, University of Wuppertal and the Yerevan Physics Institute.
© European Southern Observatory (ESO), 2000