Detecting Astrophysical Gamma-rays with Panoramic Optical SETI

Astrophysical gamma-rays entering the atmosphere produce a cascade of relativistic charged particles that can be detected at the surface with scintillators or imaging atmospheric Cherenkov telescopes (IACT). Studying the highest energy gamma-ray sources is made difficult by the observed inverse power law flux. Above 100 teraelectronvolts (TeV), roughly 5 gamma-rays from the strongest sources are detected per square kilometer per day. IACTs offer better angular resolution than particle detectors, but meeting the effective area requirement above 100 TeV is challenging and expensive. The Panoramic Search for Extraterrestrial Intelligence (PANOSETI) is an experiment designed to observe optical transients with nanosecond time resolution over a wide field of view. These characteristics make PANOSETI telescopes sensitive to the atmospheric air showers produced by gamma-rays. Furthermore, these 0.5 meter aperture telescopes are more affordable and easier to deploy than traditional IACTs. Here we demonstrate that PANOSETI effectively detects high energy gamma-ray emission, and show results of Monte Carlo simulations for a planned array of these telescopes.