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T: Fachverband Teilchenphysik

T 87: Gamma-Astronomie II

T 87.5: Vortrag

Donnerstag, 28. März 2019, 17:05–17:20, S14

FACT - Measuring the Evolution of the Optical Point Spread Function using Muon-Rings — •Laurits Tani — ETH Zürich, Switzerland

In ground-based gamma-ray astronomy, muon events have a distinct feature of casting ring-like images on the sensor plane, thus forming a well known signal class for Cherenkov telescopes. These ring-like images can then be used to deduce the optical point spread function (PSF) which is a highly important measure of the optical quality of the system. In this talk the observed width of a muon ring is used as a measure to infer the PSF. However to have a good estimate for this width, the reconstruction of the ring center and ring radius itself needs to be accurate, so different methods of ring feature extraction were studied. To check the accuracy of the ring reconstruction and correlation between the width of the ring and PSF, a simulation is done. Measuring the evolution of the PSF over time allows to adjust the instrument response function postliminary. Furthermore, no dedicated observations are needed and no human activity is required on site. The best found reconstruction method is applied on FACT data and the plots for accuracy of the ring feature extraction and for PSF vs. time will be presented.