Performance of the stereoscopic system of the HEGRA imaging air Cerenkov telescopes: Monte Carlo simulations and observations

Based on the Monte Carlo simulations we have studied the performance of the HEGRA system of imaging air Cerenkov telescopes (IACTs) in its present con figuration of 4 IACTs as well as in its future final configuration of 5 IAC Ts. Here we present the results on the basic characteristics of the IACT sy stem which are used in the standard data analysis procedure, i.e., the coll ection areas, the detection rates, the angular resolution, the energy resol ution, and the gamma/hadron-separation efficiency. By comparing several key Monte Carlo predictions with experimental results it is possible to check the accuracy of the simulations. The Monte Carlo results concerning hadron- nuclear showers are tested with the recorded cosmic ray events and the resu lts concerning photon-induced showers are tested with a large data sample o f gamma-rays observed from BL Lac object Mkn 501 during its high flaring ac tivity in 1997. Summarizing the simulations and current observations we giv e the basic recommendations of using the instrument and the major values of its sensitivity. (C) 1999 Elsevier Science B.V.