Special Astroparticle Seminar

Long-term monitoring of blazars with dedicated Cherenkov telescopes? the DWARF network and the FACT telescope

Michael Backes

Technical University Dortmund

With the latest generation of imaging atmospheric Cherenkov telescopes (IACTs), i.e. H.E.S.S., MAGIC, and VERITAS, the research field of very high energy (VHE) gamma-ray astronomy has made a huge progress. A vast increase in the instruments' sensitivity and, at the same time, a significant lowering the energy threshold compared to their predecessors made it possible to enhance the number of detected extragalactic sources from seven to about fifty. Obviously, these telescopes are overbooked with discovery observations at their sensitivity limit and hardly any time can be spent on monitoring the long-term behavior of the strongest sources. Orthogonally to this approach, we started to set up a global network of several small IACTs for long-term monitoring of the TeV-brightest blazars, the Dedicated Worldwide AGN Research Facility (DWARF). The first telescope which has been built to be part of the DWARF network is a completely refurbished former HEGRA telescope located on the Canary island of La Palma, the First G-APD Cherenkov Telescope (FACT). Moreover, FACT is the very first IACT that is equipped with a camera completely based on semi-conductors (G-APDs) as photo sensors, making it a pathfinder experiment for future Cherenkov telescopes like CTA.

In this talk, I will review the physical motivation of blazar monitoring, give an overview of the status and perspectives of DWARF and outline the technical aspects and first results of FACT.