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Bibliographical reference
Astroparticle Physics, Volume 94, p. 29-41.
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9
2017
Journal
Citations
62
Refereed citations
50
Description
MAGIC, a system of two imaging atmospheric Cherenkov telescopes,
achieves its best performance under dark conditions, i.e. in absence of
moonlight or twilight. Since operating the telescopes only during dark
time would severely limit the duty cycle, observations are also
performed when the Moon is present in the sky. Here we develop a
dedicated Moon-adapted analysis to characterize the performance of MAGIC
under moonlight. We evaluate energy threshold, angular resolution and
sensitivity of MAGIC under different background light levels, based on
Crab Nebula observations and tuned Monte Carlo simulations. This study
includes observations taken under non-standard hardware configurations,
such as reducing the camera photomultiplier tubes gain by a factor
∼1.7 (reduced HV settings) with respect to standard
settings (nominal HV) or using UV-pass filters to strongly reduce the
amount of moonlight reaching the cameras of the telescopes. The Crab
Nebula spectrum is correctly reconstructed in all the studied
illumination levels, that reach up to 30 times brighter than under dark
conditions. The main effect of moonlight is an increase in the analysis
energy threshold and in the systematic uncertainties on the flux
normalization. The sensitivity degradation is constrained to be below
10%, within 15-30% and between 60 and 80% for nominal HV, reduced HV and
UV-pass filter observations, respectively. No worsening of the angular
resolution was found. Thanks to observations during moonlight, the
maximal duty cycle of MAGIC can be increased from ∼18%, under dark
nights only, to up to ∼40% in total with only moderate performance
degradation.
Related projects
Particle Astrophysics
The MAGIC Collaboration is integrated by 20 research institutes and university departments from Armenia, Bulgaria, Finland, Germany, Italy, Poland, Spain, Switzerland and USA. The collaboration comprises two 17m diameter telescopes, located at the Roque de los Muchachos Observatory, designed to measure the Cherenkov radiation associated with
Ramón
García López