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T: Fachverband Teilchenphysik
T 87: Gamma-Astronomie II
T 87.8: Talk
Thursday, March 28, 2019, 17:50–18:05, S14
FACT - Investigations of Long Term Performance — •Fabian Theißen, Marvin Beck, Marc Klinger, and Thomas Bretz for the FACT Collaboration collaboration — RWTH Aachen, Germany
The First G-APD Cherenkov Telescope (FACT) has continuously been monitoring a small sample of known TeV gamma-ray sources over the last seven years reaching up to 93% data taking efficiency.
Measurements of imaging air Cherenkov telescopes are dominated by charged cosmic rays. They hit the Earth with a remarkably stable rate. Therefore, they are a precise measurement of performance variations and changes of the atmosphere and can be used to quantify these variations.
The telescope has observed the Crab Nebula for more than 2000 hours. As the Crab Nebula is known as a standard candle in TeV astronomy, correlation studies of the cosmic ray rate with the photon flux of Crab allow for an efficiency correction. A long term understanding of the changes in the performance of the telescope is required for further analyses like periodicity studies. It also allows for a phenomenological correction of data taken under bad weather conditions.