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Apr 12 – 17, 2021
Africa/Johannesburg timezone

Unbiased Monitoring of Active Galactic Nuclei in Gamma Rays

Apr 13, 2021, 3:00 PM
Contributed AGN Exploring the Cosmos: AGN-1


Daniela Dorner


To understand extremely variable sources like Active Galactic Nuclei,
unbiased monitoring is of great importance. Often multi-wavelength
observations are triggered by flaring activities of the sources which
biases the overall data sample towards higher fluxes. Studying flux
correlations between different wavelengths or flux distributions, an
unbiased data sample is crucial. In the GeV energy range, Fermi-LAT is
continuously monitoring the MeV-GeV-sky with a large field of view. At
TeV energies, different monitoring programs are available. While for
large imaging air Cherenkov telescopes the time dedicated to monitoring
is limited, FACT and HAWC dedicate their observation time to unbiased

Observing a small sample of bright blazars at TeV energies as much as
possible, FACT has collected an unprecedented data sample of more than
14700 hours of physics data. For each of the bright, monitored sources,
a total of 1900 hours to 3200 hours of physics data are available. Per
night, the sources are observed between 40 minutes and 7 hours
depending on their visibility. This provides the possibility to probe
time scales from minutes to years. Comparing light curves, variability
characteristics and flux distributions from Fermi-LAT and FACT allows
for constraining the mechanisms responsible for the gamma-ray emission at GeV
and TeV energies.

The presentation will summarize results from an unbiased data sample
from more than eight years of monitoring.

Primary author

Presentation materials