An analysis method for data taken by Imaging Air Cherenkov Telescopes at very high energies under the presence of clouds

0538474 - FZÚ 2021 RIV NL eng J - Článek v odborném periodiku
Sobczynska, D. … celkem 4 autorů
An analysis method for data taken by Imaging Air Cherenkov Telescopes at very high energies under the presence of clouds.
Astroparticle Physics. Roč. 120, July (2020), s. 1-10, č. článku 102450. ISSN 0927-6505. E-ISSN 1873-2852
Výzkumná infrastruktura: CTA-CZ II - 90105
Klíčová slova: gamma-rays * general - methods * observational - instrumentation
Obor OECD: Particles and field physics
Impakt faktor: 2.724, rok: 2020
Způsob publikování: Open access
https://doi.org/10.1016/j.astropartphys.2020.102450

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 less than or similar to 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.
Trvalý link: http://hdl.handle.net/11104/0316724