GCN Circular 45072

W.J XIE (NAOC), C. PLASSE (HKU), Y.H CHENG (YNU), X.TIAN (GXU) report on behalf of the SVOM mission team:

At 2026-07-04T03:41:05 UTC (T0), SVOM/ECLAIRs triggered and located an a possible GRB (SVOM burst-id sb26070403).The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was only detected by the Image Trigger (IMT), which produced a sequence of 3 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.66 in the [5-20] keV energy band over a time window of 40.96 seconds starting at 2026-07-04T03:40:24.
The localization of the best alert is R.A., Dec. 318.5239, -25.6141 degrees (J2000) with a 90% confidence level (C.L.) radius of 10.25 arcmin (including systematic error of 2 arcmin added in quadrature).

There is a high proper motion star LP 873-16 in the ECLAIRs error box.

SVOM slewed to the burst.

SVOM/MXT began observing the field at 2026-07-04T03:43:24 UTC, 139 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 318.7072, -25.5102 degrees:
R.A. (J2000) = 21h14m49.74s
Dec. (J2000) = -25d30m36.89s
with a 90% C.L. radius of 33.97 arcseconds.

This location is 11.72 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.

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 : yhcheng@mail.ynu.edu.cn 
Please contact the BA by email if you require additional information.