Detection prospects for short time-scale transient events at VHE with current and next generation Cherenkov observatories

TL;DR

This paper evaluates the potential for detecting short time-scale transient events like GRBs at very-high energies using current and future Cherenkov telescopes, highlighting the importance of VHE observations for understanding GRB physics.

Contribution

It introduces a method to estimate VHE detection prospects for transient events with Cherenkov telescopes, using GRB 090102 as a test case and comparing current and upcoming observatories.

Findings

Detection prospects improve with CTA's enhanced sensitivity.

VHE observations can help discriminate between emission models.

Method provides realistic detection estimates under various conditions.

Abstract

In the current view of Gamma-Ray Burst (GRB) phenomena, an emission component extending up to the very-high energy (VHE, E > 30 GeV) domain is though to be a relatively common feature at least in the brightest events. This leads to an unexpected richness of possible theoretical models able to describe such phenomenology. Hints of emission at tens of GeV are indeed known since the EGRET observations during the '90s and confirmed in the Fermi-LAT data. However, our comprehension of these phenomena is still far to be satisfactory. In this respect, the VHE characterization of GRBs may constitute a breakthrough for understanding their physics and, possibly, for providing decisive clues for the discrimination among different proposed emission mechanisms, which are barely distinguishable at lower energies. The current generation of Cherenkov observatories, such as the MAGIC telescopes, have opened the possibility to extend the measurement of GRB emission, and in general to any short time-scale transient phenomena, fromfew tens of GeV up to the TeV energy range, with a higher sensitivity with respect to gamma-ray space-based instruments. In the near future, a crucial role for the VHE observations of GRBs will be played by the Cherenkov Telescope Array (CTA), thanks to its about one order of magnitude better sensitivity and lower energy threshold with respect to current instruments. In this contribution, we present a method aimed at providing VHE detection prospects for observations of GRB-like transient events with Cherenkov telescopes. In particular, we consider the observation of the transient event GRB 090102 as a test case for the method and show the achieved detection prospects under different observational conditions for the MAGIC telescopes and CTA.