Observations at Very High Energies with the First G-APD Cherenkov Telescope

by Dr Daniela Dorner (Uni Wuerzburg)

Tuesday 29 Oct 2013, 17:00 → 18:00 Europe/Berlin

Auditorium (MPI fuer Physik)

Since two years, the First G-APD Cherenkov Telescope (FACT) is operational at the Observatorio del Roque de los Muchachos at the Canary Island of La Palma. Using the Imaging Atmospheric Cherenkov Technique, it is observing in the gamma-ray regime at TeV energies. The two major goals of the project are monitoring of active galactic nuclei at TeV energies and the proof of principle for silicon based photo sensors (Geigermode Avalanche Photodiodes: G-APDs) in Cherenkov astronomy. Results demonstrating the performance and stability of G-APDs will be presented explaining how these devices facilitate observations in Cherenkov astronomy. Especially the robustness towards strong ambient light makes them ideal for long-term monitoring, as observations during strong moon light are possible enlarging the duty cycle of the instrument. Active galactic nuclei are known to be extremely variable objects at all energies. However, the origin of these flux variations cannot be explained well by current theoretical models. Long-term monitoring and simultaneous observations in all energy ranges are the key to better understand the processes causing the variability and to investigate the correlation between different energy ranges. Few active galactic nuclei have been monitored in the last two years with FACT. Several outbursts could be detected from Markarian 421 and Markarian 501. First results from these two years observations will be presented.