GCN Circular 43901

Ziqi Wang, Defeng Kong(GXU), Donghua Zhao(NAOC), Hatsune Goto(Kanazawa Univ.) report on behalf of the SVOM mission team:

At 2026-03-03T06:01:47 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260303A (SVOM burst-id sb26030303).

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 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.95 in the [5-20] keV energy band over a time window of 20.48 seconds starting at 2026-03-03T06:01:27.

The localization of the best alert is R.A., Dec. 92.9479, 41.1688 degrees:
R.A. (J2000) = 6h11m47.49s
Dec. (J2000) = 41d10m07.61s
 with a 90% confidence level (C.L.) radius of 9.89 arcmin (including systematic error of 2 arcmin added in quadrature).

We note that the best position (2 overlapped positions) was distant from other 3 detected positions, maybe due to Crab in FoV.
The best detection in other 3 triggers are:
R.A., Dec.  93.220, 41.184 degrees  with  90% confidence level (C.L.) radius of 10.52'.

SVOM slewed to the burst.

The SVOM/MXT team is waiting for the full dataset to detect and localise the possible SVOM/MXT counterpart.

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: Ziqi Wang: ziqi.wang@st.gxu.edu.cn.
Please contact the BA by email if you require additional information.