GCN Circular 36854

Stéphane Schanne (CEA), Olivier Godet (IRAP) on behalf of the ECLAIRs collaboration 

and SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), JeanLuc Attéia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

GRB240713A : The First probable GRB Located On-Board SVOM by ECLAIRs.

On July 13 2024, 02:02:40 (UTC, TimeTb) the ECLAIRs telescope on board SVOM triggered and located an apparent gamma-ray burst during the commissioning phase.

The on-board trigger produced real-time alerts, but their prompt sending to ground is not yet enabled, such that they were received after delay. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled.

The burst is seen in the Count-Rate Trigger (CRT) and the Image Trigger (IMT). The best detection is given by IMT with a signal to noise of 9.7 in the 8-120 keV energy band on a time window of 40.96 s starting at TimeTb. The location is RA, Dec = 352.59, 1.88 (J2000). This is about 28.5 degrees off the ECLAIRs optical axis in the partially coded field of view. The SVOM attitude control system is still undergoing calibration, but we estimate that the location accuracy is within 10 arcmin (radius).

We caution that due to solar activity the particle environment is currently perturbed on low Earth orbit. However, the quality of the images produced let us be confident on the reality of this transient event.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developped jointly by APC, CEA, CNES and IRAP.

The SVOM points of contact for this burst are Stéphane Schanne (s.schanne@cea.fr) and Olivier Godet (ogodet@irap.omp.eu).