The throughput calibration of the VERITAS telescopes
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Published:2022-02
Issue:
Volume:658
Page:A83
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ISSN:0004-6361
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Container-title:Astronomy & Astrophysics
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language:
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Short-container-title:A&A
Author:
Adams C. B.ORCID, Benbow W., Brill A., Buckley J. H., Christiansen J. L., Falcone A.ORCID, Feng Q., Finley J. P., Foote G. M.ORCID, Fortson L., Furniss A., Giuri C., Hanna D.ORCID, Hassan T., Hervet O.ORCID, Holder J., Hona B., Humensky T. B., Jin W., Kaaret P.ORCID, Kleiner T. K., Kumar S., Lang M. J.ORCID, Lundy M., Maier G.ORCID, Moriarty P.ORCID, Mukherjee R.ORCID, Nievas Rosillo M.ORCID, O’Brien S., Park N.ORCID, Patel S.ORCID, Pfrang K.ORCID, Pohl M.ORCID, Prado R. R., Pueschel E., Quinn J.ORCID, Ragan K.ORCID, Reynolds P. T., Ribeiro D.ORCID, Roache E., Ryan J. L., Santander M.ORCID, Weinstein A., Williams D. A.ORCID, Williamson T. J.
Abstract
Context. The response of imaging atmospheric Cherenkov telescopes to incident γ-ray-initiated showers in the atmosphere changes as the telescopes age due to exposure to light and weather. These aging processes affect the reconstructed energies of the events and γ-ray fluxes.
Aims. This work discusses the implementation of signal calibration methods for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) to account for changes in the optical throughput and detector performance over time.
Methods. The total throughput of a Cherenkov telescope is the product of camera-dependent factors, such as the photomultiplier tube gains and their quantum efficiencies, and the mirror reflectivity and Winston cone response to incoming radiation. This document summarizes different methods to determine how the camera gains and mirror reflectivity have evolved over time and how we can calibrate this changing throughput in reconstruction pipelines for imaging atmospheric Cherenkov telescopes. The implementation is validated against seven years of observations with the VERITAS telescopes of the Crab Nebula, which is a reference object in very-high-energy astronomy.
Results. Regular optical throughput monitoring and the corresponding signal calibrations are found to be critical for the reconstruction of extensive air shower images. The proposed implementation is applied as a correction to the signals of the photomultiplier tubes in the telescope simulation to produce fine-tuned instrument response functions. This method is shown to be effective for calibrating the acquired γ-ray data and for recovering the correct energy of the events and photon fluxes. At the same time, it keeps the computational effort of generating Monte Carlo simulations for instrument response functions affordably low.
Funder
U.S. Department of Energy Office of Science U.S. National Science Foundation U.S. Smithsonian Institution Germany's Helmholtz Association Open Science Grid
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
5 articles.
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1. VERITAS highlights of observations and results;SciPost Physics Proceedings;2023-09-29 2. The Cherenkov Telescope Array;Handbook of X-ray and Gamma-ray Astrophysics;2023-09-05 3. Analysis Methods for Gamma-Ray Astronomy;Handbook of X-ray and Gamma-ray Astrophysics;2023-09-05 4. A VERITAS/Breakthrough Listen Search for Optical Technosignatures;The Astronomical Journal;2023-08-01 5. Gamma-ray observations of MAXI J1820+070 during the 2018 outburst;Monthly Notices of the Royal Astronomical Society;2022-09-23
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