An analysis method for data taken by Imaging Air Cherenkov Telescopes at very high energies under the presence of clouds
arXiv:2009.13204 · doi:10.1016/j.astropartphys.2020.102450
Abstract
The effective observation time of Imaging Air Cherenkov Telescopes (IACTs) plays an important role in the detection of gamma-ray sources, especially when the expected flux is low. This time is strongly limited by the atmospheric conditions. Significant extinction of Cherenkov light caused by the presence of clouds reduces the photon detection rate and also complicates or even makes impossible proper data analysis. However, for clouds with relatively high atmospheric transmission, high energy showers can still produce enough Cherenkov photons to allow their detection by IACTs. In this paper, we study the degradation of the detection capability of an array of small-sized telescopes for different cloud transmissions. We show the expected changes of the energy bias, energy and angular resolution and the effective collection area caused by absorption layers located at 2.5 and 4.5 km above the observation level. We demonstrate simple correction methods for reconstructed energy and effective collection area. As a result, the source flux that is observed during the presence of clouds is determined with a systematic error of < 20%. Finally, we show that the proposed correction method can be used for clouds at altitudes higher than 5 km a.s.l.. As a result, the analysis of data taken under certain cloudy conditions will not require additional time-consuming Monte Carlo simulations.
10 pages, 9 figures
References in corpus (10)
- Observations of the Crab Nebula with H.E.S.S
- The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
- Implementation of the Random Forest Method for the Imaging Atmospheric Cherenkov Telescope MAGIC
- On the re-summation of enhanced Pomeron diagrams
- Unfolding of differential energy spectra in the MAGIC experiment
- Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layout
- An innovative silicon photomultiplier digitizing camera for gamma-ray astronomy
- A method to correct IACT data for atmospheric absorption due to the Saharan Air Layer
- Nature of the low-energy, γ-like background for the Cherenkov Telescope Array
- Influence of clouds on the parameters of images measured by IACT at very high energies