Overview of the ECLAIRs Trigger for SVOM gamma-ray burst detection

TL;DR

The paper describes the ECLAIRs trigger system onboard the SVOM satellite, which autonomously detects and localizes gamma-ray bursts, enabling rapid alerts and follow-up observations.

Contribution

It provides an overview of the onboard trigger algorithms, including the Count-Rate Trigger and Image Trigger, and discusses their role in GRB detection and localization.

Findings

Detected several notable GRBs, including high-redshift bursts.

Enabled numerous redshift measurements for observed GRBs.

Demonstrated effective autonomous detection and alerting capabilities.

Abstract

The French-Chinese SVOM satellite mission (Space-based multi-band astronomical Variable Objects Monitor) was launched in mid-2024, with science objectives focused on the detection and study of astrophysical transient events, primarily Gamma-Ray Bursts (GRBs). The onboard trigger of the hard X-ray wide-field coded-mask instrument ECLAIRs autonomously detects and localizes GRBs on SVOM and requests automatic spacecraft slews toward these sources, enabling follow-up observations by the onboard narrow field-of-view instruments MXT and VT. The trigger also transmits real-time alerts via the SVOM VHF network to the ground, allowing rapid follow-up campaigns by the broader community, including multiple space- and ground-based facilities. We present an overview of the ECLAIRs trigger, with emphasis on the two trigger algorithms running simultaneously onboard: the Count-Rate Trigger (CRT) and the Image Trigger (IMT), both of which issue alerts for GRBs localized on the sky. The trigger has already detected several notable events, including both classical GRBs and peculiar X-ray-rich GRBs, enabling numerous redshift measurements, including high-redshift bursts.