GCN Circular 44622

M. Brunet, L. Bouchet (IRAP), A. Saccardi (CEA/Irfu), D. Gotz (CEA/Irfu) report on behalf of the SVOM mission team:

At 2026-05-15T19:08:19 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260515A (SVOM burst-id sb26051504).

The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 17 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 24.06 in the [5-20] keV energy band over a time window of 10.20 seconds starting at 2026-05-15T19:08:19.

The localization of the best alert is R.A., Dec. 227.6800, 24.5706 degrees:
R.A. (J2000) = 15h10m43.20s
Dec. (J2000) = 24d34m14.13s
with a 90% confidence level (C.L.) radius of 3.77 arcmin (including systematic error of 2 arcmin added in quadrature).

The SVOM/ECLAIRs light curve showed a single peak structure with a T90 duration of 16.6 +/-1.5 s in the 5-120 keV.

This burst was also detected by SVOM/GRM with a significance of 10.2 .

SVOM slewed to the burst.

MXT and VT began observing the field after the slew. The analysis of the data will be published in a future circular.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.

The Burst Advocate (BA) on shift for this alert is Andrea Saccardi (CEA): andrea.saccardi@cea.fr
Please contact the BA by email if you require additional information.