Optimal strategies for observation of active galactic nuclei variability with Imaging Atmospheric Cherenkov Telescopes

Abstract

Variable emission is one of the defining characteristic of active galactic nuclei (AGN). While providing precious information on the nature and physics of the sources, variability is often challenging to observe with time- and field-of-view-limited astronomical observatories such as Imaging Atmospheric Cherenkov Telescopes (IACTs). In this work, we address two questions relevant for the observation of sources characterized by AGN-like variability: what is the most time-efficient way to detect such sources, and what is the observational bias that can be introduced by the choice of the observing strategy when conducting blind surveys of the sky. Different observing strategies are evaluated using simulated light curves and realistic instrument response functions of the Cherenkov Telescope Array (CTA), a future gamma-ray observatory. We show that strategies that makes use of very small observing windows, spread over large periods of time, allows for a faster detection of the source, and are less influenced by the variability properties of the sources, as compared to strategies that concentrate the observing time in a small number of large observing windows. Although derived using CTA as an example, our conclusions are conceptually valid for any IACTs facility, and in general, to all observatories with small field of view and limited duty cycle.

arXiv comment14 pages, 11 figures

References in corpus (16)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• A Unified Approach to the Classical Statistical Analysis of Small Signals
• On characterising the variability properties of X-ray light curves from active galaxies
• Design Concepts for the Cherenkov Telescope Array
• Observations of the Crab Nebula with H.E.S.S
• An Exceptional VHE Gamma-Ray Flare of PKS 2155-304
• The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Variable VHE gamma-ray emission from Markarian 501
• Non-linear X-ray variability in X-ray binaries and active galaxies
• Gamma-ray Light Curves and Variability of Bright Fermi-Detected Blazars
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• VHE gamma-ray emission of PKS 2155-304: spectral and temporal variability
• The minijets-in-a-jet statistical model and the RMS-flux correlation
• Active Galactic Nuclei under the scrutiny of CTA
• Long-term lightcurves from combined unified very high energy $\gamma$-ray data
• The aperiodic broad-band X-ray variability of Cygnus X-3