Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 61: Gamma Astronomy I

T 61.4: Talk

Wednesday, March 18, 2026, 17:00–17:15, KS 00.005

Effects of the geomagnetic field on IACT event reconstruction — •Matheus Genaro Dantas Xavier, Tim Unbehaun, Rodrigo Guedes Lang, and Stefan Funk — Erlangen Centre for Astroparticle Physics (ECAP), Friedrich-Alexander-Universität Erlangen-Nürnberg

The observation of astrophysical gamma rays by Imaging Atmospheric Cherenkov Telescopes (IACTs) is based on the detection and imaging of Cherenkov light produced along the development of extensive particle air showers. The recorded images are then analyzed to reconstruct fundamental information of the primary gamma ray, such as its energy and direction. Due to Earth’s magnetic field, charged particles in the shower are deflected during their trajectory, broadening the lateral development of the shower and the distribution of Cherenkov light on the ground. Consequently, distortions in the camera image can lead to systematic effects in the reconstruction procedure. These effects are especially visible for low energy events (∼100 GeV) and are believed to be significant when only one telescope is triggered (monoscopic reconstruction). In this work, we investigate the impact of the geomagnetic field on the largest H.E.S.S. telescope (CT5), based on simulations of gamma-ray-induced air showers. Due to its large light collection area and improved camera design, CT5 is crucial for lowering the energy threshold of observed sources. Therefore, to comprehend the geomagnetic field effects is especially important to quantify and possibly correct systematic errors present on the monoscopic analysis.

Keywords: Gamma rays; Geomagnetic field; Cherenkov light; Event reconstruction; Imaging Atmospheric Cherenkov Telescopes