R. Bazer-Bachi

A NEW ANALYSIS METHOD FOR VERY HIGH DEFINITION IMAGING ATMOSPHERIC CHERENKOV TELESCOPES AS APPLIED TO THE CAT TELESCOPE

Abstract A new method of shower-image analysis is presented which appears very powerful as applied to those Cherenkov Imaging Telescopes with very high definition imaging capability. It provides hadron rejection on the basis of a single cut on the image shape, and simultaneously determines the energy of the electromagnetic shower and the position of the shower axis with respect to the detector. The source location is also reconstructed for each individual γ-ray shower, even with one single telescope, so for a point source the hadron rejection can be further improved. As an example, this new method is applied to data from the CAT (Cherenkov Array at Themis) imaging telescope, which has been operational since Autumn, 1996.

First detection of gamma rays from the crab nebula with the CELESTE “solar farm” Cherenkov detector

Abstract We have converted the THEMIS solar array (French Pyrenees) into an atmospheric Cherenkov telescope, called CELESTE, sensitive to astrophysical gamma rays above 30 GeV (7×10 24 Hz). In early 1998 the Crab nebula was detected at 80 GeV with a preliminary 18 heliostat setup. The full 40 heliostat array has since been commissioned. The STACEE experiment using the same technique in New Mexico is also analysing their first data. Thus, the window between the EGRET instrument and the Cherenkov imagers has been opened. We describe the CELESTE detector and the data analysis, and discuss the prospects for studying AGN (specifically, blazars) and galactic sources in this energy range.

Approaching the Spectral Knee in High Energy Cosmic Rays with CREAM

The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment flew for the third time in Antarctica between 19 December 2007 and 16 January 2008. This ∼29-day flight resulted in an accumulation of almost 100 days of exposure for the CREAM payload. The instrument included double layers of finely segmented Silicon detectors and an imaging Cherenkov Camera for charge measurements. A finely segmented tungsten-scintillator fiber ionization calorimeter was used for energy measurements. Energy spectra of cosmic ray particles for 1 ≤ Z ≤26 were measured at the top of atmosphere with excellent charge and energy resolution. CREAM extends direct measurements of cosmic-ray composition to energies where ground-based air shower measurements are possible, thereby providing calibration for those indirect measurements. The instrument performance during the flight and results from the on-going data analysis are presented. The project status, including preparations for the next flight and results from the beam test ca...

Observation of supernova remnants with the CAT Cherenkov imaging telescope

Supernova remnants (SNR) can be broadly classified into two types: plerionic or plasma-filled SNR, like the Crab Nebula, and shell-type SNR, like Cassiopeia A (Cas A). VHE observations of the Crab Nebula and Cas A made with the CAT atmospheric Cherenkov imaging telescope are used to constrain models for production of gamma rays in SNR. For both plerionic and shell-type SNR, these observations serve primarily to impose a limit on the magnetic field in the region where the particles are accelerated.