The H.E.S.S. II GRB Program

TL;DR

The paper discusses the upgraded H.E.S.S. II array's capabilities and strategies for observing gamma-ray bursts at energies above 10 GeV, focusing on rapid response and data analysis methods.

Contribution

It introduces the second phase of H.E.S.S. with a new large telescope, expanding energy coverage and detailing the observation and data analysis schemes for GRB detection.

Findings

Enhanced energy range up to 100 GeV for GRB observations

Improved rapid repointing system performance

Effective data analysis scheme for transient gamma-ray events

Abstract

Gamma-ray bursts (GRBs) are some of the most energetic and exotic events in the Universe, however their behaviour at the highest energies (>10 GeV) is largely unknown. Although the Fermi-LAT space telescope has detected several GRBs in this energy range, it is limited by the relatively small collection area of the instrument. The H.E.S.S. experiment has now entered its second phase by adding a fifth telescope of 600 m$^{2}$ mirror area to the centre of the array. This new telescope increases the energy range of the array, allowing it to probe the sub-100 GeV range while maintaining the large collection area of ground based gamma-ray observatories, essential to probing short-term variability at these energies. We will present a description of the GRB observation scheme used by the H.E.S.S. experiment, summarising the behaviour and performance of the rapid GRB repointing system, the conditions under which potential GRB repointings are made and the data analysis scheme used for these observations.