GRB 260704A
GCN Circular 45102
Subject
GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
Date
2026-07-07T13:16:54Z (2 days ago)
From
F. Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work@gmail.com>
Via
Web form
GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
Noémie Globus (UNAM), Francesco Magnani (CPPM), Camila Angulo (UNAM), Jean-Grégoire Ducoin (CPPM), Nathaniel R. Butler (ASU), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), W.J Xie (NAOC), Y. H. Cheng (YNU), C. Plasse (HKU), report:
We imaged the field of the SVOM GRB 260704A (W.J Xie et al., GCN Circ. 45072) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-07-05 07:25:02 to 11:20:12 UTC (from 27.7 to 31.7 hours after the trigger) and obtained 104 minutes of simultaneous exposure in the r and z filters.
The data were reduced, coadded, and analyzed with the 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 tentatively detected a faint, uncatalogued source consistent with both the SVOM/MXT error circle (W.J. Xie et al., GCN Circ. 45072) and the EP/FXT error circle (Y.-H. I. Yin et al., GCN Circ. 45078) at:
RA (J2000) = 21:14:51.52 = 318.71468 deg,
Dec (J2000) = -25:30:29.4 = -25.50816 deg,
with an estimated astrometric uncertainty of 0.5 arcsec.
The preliminary unsubtracted magnitude derived for that source was:
r = 23.54 ± 0.22
z = 22.70 ± 0.27
We reobserved from 2026-07-06 07:18:26 to 09:47:39 UTC (from 51.62 to 54.11 hours after the trigger) and obtained 111 minutes of simultaneous exposure in the r and z filters.
Compared to our previous observations, the source has faded. The preliminary unsubtracted magnitude is:
r = 24.08 ± 0.23 mag,
z = 23.19 ± 0.28 mag.
The detection of the source in two independent optical bands, together with its fading between the two observing epochs, makes it a possible candidate for the optical counterpart of the GRB.
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 45083
Subject
GRB 260704A: NOT optical upper limits
Date
2026-07-06T06:20:45Z (4 days ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), F. Mustafaj (NOT) report on behalf of a larger collaboration:
We observed the field of GRB 260704A reported by SVOM/ECLAIRs (Xie et al., GCN 45072), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 9x120 s exposures in the SDSS i band at mid time 2026 Jul 5.116 UT (23.1 hr after the trigger). Our observations targeted the location of the X-ray source detected by SVOM/MXT (Xie et al., GCN 45072) and EP/FXT (Yin et al., GCN 45078).
Within the EP/FXT error circle, we note the presence of a bright star (i = 15.46). Its magnitude in our image is consistent with the archival value. Its TESS light curve does not show historical variability either. This makes the star not likely related to the X-ray source.
Furthermore, in the stack of our images, no new optical source is detected within the EP/FXT error region, down to the 3-sigma limiting AB magnitudes of i > 22.5 (calibrated against nearby stars from the Pan-STARRS catalog and not corrected for Galactic extinction).
GCN Circular 45078
Subject
GRB 260704A: EP-FXT follow-up observation
Date
2026-07-04T14:56:07Z (5 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y.-H. I. Yin, C.-K. Kan (HKU), Y. H. Cheng (YNU), S.Y. Fu (HUST). Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed an automatically follow-up observation of GRB 260704A detected by SVOM/ECLAIRs (Xie et al., GCN 45072). The follow-up observation started at 2026-07-04T04:49:23 (UTC), about 1 hr after the SVOM trigger, with a total exposure time of around 2.6 ks.
On-ground analysis of the FXT data found an uncatalogued source within the ECLAIRs and MXT error circles at R.A., Dec. = 318.7151, -25.5074 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The derived average unabsorbed flux is 1.49 (-0.22/+0.26) x 10^(-12) erg/s/cm^2 (0.5-10 keV; 1-sigma uncertainty).
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular 45072
Subject
GRB 260704A: SVOM detection of a possible GRB
Date
2026-07-04T04:49:49Z (6 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
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.