VERITAS Observations of Mkn 501 in 2009

Understand

VERITAS is the high-sensitivity instrument of latest generation.

• It is often used for the short AGN monitoring exposures evenly distributed over entire observational season of a source of interest.
• Each of these exposures is long enough to detect the source at the flux level of about 1 Crab.
• During the 2009 observing season a number of exposures of Mkn 501 with VERITAS revealed variable TeV gamma-ray emission at the flux level eventually exceeding 2 Crab.