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Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes.

Hahn, J. and de los Reyes, R. and Bernlöhr, K. and Krüger, P. and Lo, Y.T.E. and Chadwick, P.M. and Daniel, M.K. and Deil, C. and Gast, H. and Kosack, K. and Marandon, V. (2014) 'Impact of aerosols and adverse atmospheric conditions on the data quality for spectral analysis of the H.E.S.S. telescopes.', Astroparticle physics., 54 . pp. 25-32.


The Earth’s atmosphere is an integral part of the detector in ground-based imaging atmospheric Cherenkov telescope (IACT) experiments and has to be taken into account in the calibration. Atmospheric and hardware-related deviations from simulated conditions can result in the mis-reconstruction of primary particle energies and therefore of source spectra. During the eight years of observations with the High Energy Stereoscopic System (H.E.S.S.) in Namibia, the overall yield in Cherenkov photons has varied strongly with time due to gradual hardware aging, together with adjustments of the hardware components, and natural, as well as anthropogenic, variations of the atmospheric transparency. Here we present robust data selection criteria that minimize these effects over the full data set of the H.E.S.S. experiment and introduce the Cherenkov transparency coefficient as a new atmospheric monitoring quantity. The influence of atmospheric transparency, as quantified by this coefficient, on energy reconstruction and spectral parameters is examined and its correlation with the aerosol optical depth (AOD) of independent MISR satellite measurements and local measurements of atmospheric clarity is investigated.

Item Type:Article
Keywords:Cherenkov telescopes, Gamma-ray astronomy, Aerosols, Atmosphere, MISR, Radiometer.
Full text:(NA) Not Applicable
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Publisher statement:NOTICE: this is the author’s version of a work that was accepted for publication in Astroparticle Physics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Astroparticle Physics, 54, February 2014, 10.1016/j.astropartphys.2013.10.003.
Date accepted:25 October 2013
Date deposited:No date available
Date of first online publication:February 2014
Date first made open access:No date available

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