GCN Circular 44504

GRB 260509A: SVOM detection of a burst

D. Götz (CEA/Irfu), A. Saccardi (CEA/Irfu), H. Goto (RIKEN), F. Lacreu (IAP), D. Adrien (CEA/Irfu), report on behalf of the SVOM mission team:

At 2026-05-09T21:51:09 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260509A (SVOM burst-id sb26050905).

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 18 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 18.00 in the [5-20] keV energy band over a time window of 20.40 seconds starting at 2026-05-09T21:51:03.

The localization of the best alert is R.A., Dec. 176.8870, 0.2095 degrees:
R.A. (J2000) = 11h47m32.9s
Dec. (J2000) = 0d12m34.2s
 with a 90% confidence level (C.L.) radius of 4.72 arcmin (including systematic error of 2 arcmin added in quadrature).

We note the presence of a high proper motion star G 10-49 at a distance of 4.48 arcmin from the ECLAIRs position.

The SVOM/ECLAIRs light curve showed a single peak structure with a T90 duration of about 14.7 +/-0.6 s.

This burst was also detected by SVOM/GRM with a significance of 6.40.
The SVOM/GRM light curve showed a double peak structure with a T90 duration of about 18 (-6/+10) s.

SVOM slewed to the burst.

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

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 Dylan Adrien: dylan.adrien@cea.fr.
Please contact the BA by email if you require additional information.