Fermi Gamma-ray Space Telescope

Multi-Wavelength View on TeV Blazars

D. Dorner
FACT Collaboration

Abstract:

The First G-APD Cherenkov Telescope (FACT) is monitoring bright blazars. While Fermi is scanning the whole sky at MeV to GeV energies, FACT is observing a small sample of blazars at energies around 1 TeV in pointed observations from the ground. Using silicon based photosensors (SiPM aka G-APDs), the camera provides consistent data with an excellent and stable performance. Since October 2011, FACT has collected a large data sample, which includes more than 1300 hours on Mrk 501. Showing no aging when exposed to strong light, SiPMs enable FACT to observe during strong moonlight enlarging not only the duty cycle of the instrument but also providing an unbiased data sample. A quick look analysis provides publicly available preliminary results within the same night. This enables us to send flare alerts to other instruments in almost real time and provides the possibility for multi-wavelength observations of interesting flare activity. The presentation will summarize the status and observations of the last four years. Results from multi-wavelength studies including the monitoring data from Fermi will be presented. A Future outlook to a global monitoring network at TeV energies will be given.