GRB 260807A
GCN Circular 45445
Subject
GRB 260807A: EP-FXT follow-up observations
Date
2026-08-26T11:11:27Z (4 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Ruizhi Li (YNAO), Chao Wu, Huali Li, Wenjin Xie, Donghua Zhao (NAOC), Hui Yang, Laurent Bouchet (IRAP) report:
We performed two EP/FXT observations of the possible faint GRB 260807A detected by SVOM/ECLAIRs (Xie et al., GCN 45308). The first EP/FXT observation started at 2026-08-07 12:51:33 UTC, approximately 1.85 hours post-trigger, with an exposure time of 5.8 ks. The second EP/FXT observation started at 2026-08-13 07:44:00 UTC, approximately 5.86 days post-trigger, with an exposure time of 4.3 ks.
We analyzed the data from the two EP/FXT observations. None of the X-ray sources within the SVOM/ECLAIRs error circle (Xie et al., GCN 45308) showed significant fading between the two EP/FXT observations, with 90% confidence upper limits on the flux of 2.85 x 10^-14 erg cm^-2 s^-1 and 3.67 x 10^-14 erg cm^-2 s^-1, respectively.
We conclude that no credible X-ray source within the SVOM/ECLAIRs error circle can be identified as the X-ray afterglow of the burst.
GCN Circular 45355
Subject
GRB 260807A: SVOM/ECLAIRs refined analysis
Date
2026-08-11T10:07:50Z (19 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
H. Yang, L. Bouchet (IRAP), R.-Z. Li (YNAO), W.-J. Xie, C. Wu (NAOC)
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 the possible faint burst GRB 260807A (SVOM burst-id sb26080703, GCN 45308, trigger time T0 = 2025-08-07T11:00:20 UTC).
The burst that triggered ECLAIRs shows a multiple peak light curve, and is detected from T0-20 s to T0 in the 8-120 keV energy band.
The time-averaged spectrum from T0-20 s to T0 in the 8-120 keV is well fitted by a power-law model with a photon index of 0.7+/-0.3 and a corresponding 4-120 keV fluence of (1.4+/-0.3)e-6 erg/cm^2.
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: Hui Yang (IRAP) (hui.yang@cnrs.fr).
GCN Circular 45309
Subject
GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
Date
2026-08-07T16:17:10Z (23 days ago)
From
Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com>
Via
email
Antonio de Ugarte Postigo (LAM), Enrique Moreno Méndez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Chao Wu (NAOC) and Rui-Zhi Li (YNAO) report:
We imaged the field of the SVOM GRB 260807A (Xie et al., GCN Circ. 45308) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-07 11:43:34 to 11:47:16 UTC (from 0.7266 to 0.8050 hours after the trigger) and obtained 4x60 seconds of exposure in the z band before the end of the night.
The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with the ASU pipeline of COLIBRÍ and with STDWeb (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1r catalog, is in the AB system, and is not corrected for Galactic extinction.
In the stacked image, we do not detect any convincing new source within the ECLAIRs error circle (Xie et al., GCN Circ. 45308) down to the following 5-sigma limit:
z > 20.0
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
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 45308
Subject
GRB 260807A: SVOM possible detection of a faint burst
Date
2026-08-07T11:45:48Z (23 days ago)
Edited On
2026-08-07T14:16:10Z (23 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Wenjin Xie, Donghua Zhao(NAOC), Hui Yang, Laurent Bouchet (IRAP), Ruizhi Li (YNAO), Chao Wu (NAOC) report on behalf of the SVOM mission team:
At 2026-08-07T11:00:20 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260807A (SVOM burst-id sb26080703).
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 Count-Rate Trigger (CRT), which produced a sequence of 1 alert. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7 in the [8-120] keV energy band over a time window of 20.40 seconds starting at 2026-08-07T10:59:59.
The localization of the best alert is R.A., Dec. 16.1480, 44.7752 degrees:
R.A. (J2000) = 1h04m35.51s
Dec. (J2000) = 44d46m30.57s
with a 90% confidence level (C.L.) radius of 11.18 arcmin (including systematic error of 2 arcmin added in quadrature).
Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being.
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 Chao WU: cwu@bao.ac.cn
Please contact the BA by email if you require additional information.