Ultra-Long Gamma-Ray Bursts detection with SVOM/ECLAIRs

TL;DR

This paper evaluates the potential of the SVOM/ECLAIRs instrument to detect ultra-long gamma-ray bursts, using simulations based on existing data and synthetic populations, indicating it can detect at least as many ulGRBs as current instruments.

Contribution

The study presents the first detailed simulation-based assessment of ECLAIRs' capabilities to detect ulGRBs, including synthetic population modeling and detection rate estimates.

Findings

ECLAIRs can detect at least as many ulGRBs as Swift/BAT.

Simulations show ECLAIRs' effectiveness in observing high-redshift ulGRBs.

Estimated ulGRB detection rate by ECLAIRs is promising.

Abstract

Ultra-long Gamma-Ray Bursts (ulGRBs) are Gamma-Ray Bursts (GRBs) with an unusually long emission in X and gamma rays, reaching durations of thousands of seconds. They could form a specific class of high-energy transient events, whose origin is still under discussion. The current sample of known ulGRBs consists of a few tens of events which have been detected so far by the Burst Alert Telescope (BAT) aboard the Neil Gehrels Swift Observatory and some other instruments. The SVOM mission which is scheduled to begin operations after 2021 could help to detect and observe more ulGRBs thanks to its soft gamma-ray telescope ECLAIRs. After an introduction on ulGRBs and the SVOM mission, we present the results of our simulations on the capabilities of ECLAIRs to detect ulGRBs. First we use the sample of ulGRBs detected by Swift/BAT and simulate these events through a model of the instrument and the prototype trigger software that will be implemented onboard ECLAIRs. Then we present a study of the ECLAIRs capabilities to detect a synthetic population of ulGRBs built by transporting the ulGRBs detected by Swift/BAT to higher redshifts. Finally we give an estimate of the ulGRB rate expected to be detected by ECLAIRs and show that ECLAIRs can detect at least as much ulGRBs as BAT.