GRB 260303A
GCN Circular 43926
Subject
GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
Date
2026-03-05T16:36:08Z (6 days ago)
Edited On
2026-03-05T20:19:40Z (5 days ago)
From
Debalina Kar at ARIES <kardebalina2000@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
GCN Circular 43925
Subject
GRB 260303A: 1.3m DFOT optical upper limit
Date
2026-03-05T16:34:28Z (6 days ago)
From
Debalina Kar at ARIES <kardebalina2000@gmail.com>
Via
Web form
Debalina Kar, Pankaj Pawar, Anshika Gupta, Dhruv Jain and Kuntal Misra (ARIES) report:
We observed the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303, Wang et al., GCN 43901) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India.
The observations began on 2026-03-03 at 14:54:29.000 UT, approximately 8.88 hours after the trigger. We obtained multiple exposures of 300 s each in the R filter . A total of 10 frames were aligned and stacked to improve the signal-to-noise ratio.
In the stacked frame we do not detect any optical counterpart within the error box of SVOM/ECLAIRs (Brunet et al., GCN 43922, Wang et al., GCN 43901) as well as outside the ECLAIRs error circle as reported by Xin et al. (GCN 43916) and (Schneider et al., GCN 43902). This is consistent with the non-detection in the J band reported by Mo et al. (GCN 43915).
We derive the following 3-sigma upper limit from the stacked image:
Date (UT) Start Time T_start–T0 (hr) Filter Exposure Magnitude
----------------------------------------------------------------------------------
2026-03-03 14:54:29 ~8.88 R 300 s × 10 > 20.29
The reported magnitude is not corrected for Galactic extinction. Photometric calibration was performed using standard stars from the USNO-B1.0 catalogue.
GCN Circular 43922
Subject
GRB 260303A: SVOM/ECLAIRs refined analysis
Date
2026-03-05T09:11:45Z (6 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, L. Bouchet (IRAP), Z. Wang, D. Kong(GXU) report on behalf of the SVOM/ECLAIRs team.
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260303A (SVOM burst-id sb26030303 – GCN 43901, trigger time T0 = 2026-03-03T06:01:47 UTC).
The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration is estimated to be around 14.5s (from T0-19.5s to T0-5s) in the 4-120 keV energy band through imaging.
The refined burst localization is RA, Dec = 93.1458, 41.1727 degrees:
RA (J2000) = 06h12m34.99s
Dec (J2000) = 41d10m21.72s
with a 90% C.L. radius of 9.6 arcmin (including systematic error of 6 arcmin added in quadrature).
The time-averaged spectrum from T0-19.5 s to T0-5 s in the energy range 5-120 keV is best fitted by a powerlaw model with a photon index of 1.67 +0.14/-0.13. With this model, the 4-120 keV fluence is (1.19 +0.11/-0.20) e-6 erg/cm² and the 4-120 keV photon flux is 2.73 +0.16/-0.31 ph/cm²/s.
All the quoted errors are at the 68% confidence level.
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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.
The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr)
GCN Circular 43916
Subject
GRB 260303A: SVOM/VT optical observations
Date
2026-03-04T01:20:25Z (7 days ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
Via
Web form
L. P. Xin, Y. N. Ma, H. L. Li, C. Wu, Z. H. Yao, Y. L. Qiu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), Ziqi Wang and Defeng Kong(GXU) report on behalf of the SVOM/VT team.
SVOM/VT performed observation with auto slew to the field of GRB 260303A triggered by SVOM/ECLAIRs (sb26030303,Wang et al., GCN 43901). The observation started at 2026-03-03T06:12:27 UTC, i.e. about 9.5 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The optical afterglow reported (Schneider et al., GCN 43902) was clearly detected in both channels.
The magnitudes we derived are:
mid time (min) | exposure time (s)| band| mag (AB)
-------------|-------------------|------ |--------------
10.4 | 50 | VT_B | 19.29+/-0.05
10.4 | 50 | VT_R | 17.62+/-0.02
47.5 | 50 | VT_B | 20.48+/-0.11
47.5 | 50 | VT_R | 19.51+/-0.07
More detailed analysis is still on going.
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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 43915
Subject
GRB 260303A: J-band observations with WINTER
Date
2026-03-04T00:22:14Z (7 days ago)
From
Geoffrey Mo at Caltech / Carnegie Observatories <gmo@mit.edu>
Via
Web form
Geoffrey Mo (Caltech/Carnegie), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Viraj Karambelkar (Columbia), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 260303A (Wang et al., GCN 43901) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).
Observations began at 2026-03-03T06:53:36 UTC in the J band (~52 min after the GRB trigger), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
We do not detect a source at the optical counterpart location (Schneider et al., GCN 43902). We obtain the following 5-sigma upper limit: J = 19.2 mag (AB).
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 43902
Subject
GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
Date
2026-03-03T07:31:10Z (8 days ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
Benjamin Schneider (LAM), Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Jean-Luc Atteia (IRAP), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Ziqi Wang (GXU) and Defeng Kong (GXU) report:
We imaged the field of the SVOM GRB 260303A (Wang et al., GCN Circ. 43901) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-03 06:02:58 to 06:24:06 UTC (from 81 seconds after the trigger or 30 seconds after the notice until to 24 minutes after the trigger) and obtained 700 seconds of simultaneous exposure in the r and z filters.
The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detect an uncatalogued source just outside the ECLAIRs error circle (Wang et al., GCN Circ. 43901) at:
RA(J2000) = 06:12:45.06 = 93.1877 degrees
Dec(J2000) = +41:09:04.4 = 41.1512 degrees
with an uncertainty of 0.5 arcsec.
The preliminary magnitudes derived for that source are:
r = 18.69 +/- 0.01
z = 18.19 +/- 0.02
The source is observed to rise and then fall in both r and z.
Further observations are ongoing.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular 43901
Subject
GRB 260303A: SVOM detection of a burst
Date
2026-03-03T07:17:32Z (8 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
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.