Microsecond Time Resolution Optical Photometry using a H.E.S.S. Cherenkov Telescope

TL;DR

This paper presents a novel optical photometer with microsecond resolution installed on a H.E.S.S. Cherenkov telescope, enabling high-time-resolution observations of astrophysical phenomena like pulsars and flares.

Contribution

The authors developed and tested a high-time-resolution optical photometer integrated with a Cherenkov telescope, demonstrating its capability to detect rapid astrophysical events.

Findings

Successful observation of Crab pulsar confirming instrument performance

Detection of microsecond to millisecond optical flares from galactic targets

Validation of the photometer's sensitivity and data analysis methods

Abstract

We have constructed an optical photometer with microsecond time resolution, which is currently being operated on one of the H.E.S.S. telescopes. H.E.S.S. is an array of four Cherenkov telescopes, each with a 107 m^2 mirror, located in the Khomas highland in Namibia. In its normal mode of operation H.E.S.S. observes Cherenkov light from air showers generated by very high energy gamma-rays in the upper atmosphere. Our detector consists of seven photomultipliers, one in the center to record the lightcurve from the target and six concentric photomultipliers as a veto system to reject disturbing signals e.g. from meteorites or lightning at the horizon. The data acquisition system has been designed to continuously record the signals with zero deadtime. The Crab pulsar has been observed to verify the performance of the instrument and the GPS timing system. Compact galactic targets were observed to search for flares on timescales of a few microseconds to ~ 100 milliseconds. The design and sensitivity of the instrument as well as the data analysis method are presented.