GRB 260726A
GCN Circular 45259
Subject
GRB 260726A: SVOM/ECLAIRs refined analysis
Date
2026-07-30T23:53:05Z (2 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet (IRAP), W. Xie (NAOC), R. Li (YNAO), Z. Wang (BNU) 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 260726A (SVOM burst-id sb26072614 – GCN 45219 & GCN 45229, trigger time T0 = 2026-07-26T23:45:23UTC), which was also detected by Fermi/GBM (GCN 45218 & GC 45246).
The burst that triggered ECLAIRs onboard shows a single peak lightcurve. The burst duration is T90 = 63 +9/-10 s in the 4-120 keV energy band.
The time-averaged spectrum from T0-23.3 s to T0+35.9 s in the 5-120 keV energy range is best fitted by a powerlaw with an exponential cutoff model with alpha = -1.30 +0.23/-0.18 and a peak energy = 58 +57/-18 keV. With this model, the 4-120 keV fluence is (1.1 +/-0.1)e-6 erg/cm^2 and the 4-120 keV photon flux is 0.61+/-0.03 ph/cm^2/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 45249
Subject
GRB 260726A: EP-FXT follow-up observations
Date
2026-07-29T03:29:48Z (2 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Ruizhi Li (YNAO), Ziming Wang (BNU), Yifang Liang (PMO), Wenjin Xie (NAOC), Clara Plasse (HKU) report on behalf of the SVOM mission team:
EP-FXT performed a follow-up observation of GRB 260726A detected by SVOM/ECLAIRs (Liang et al., GCN 45219), which also triggered Fermi/GBM (Scotton et al., GCN 45218, GCN 45246). The follow-up observation started at 2026-07-27T23:04:39 (UTC), about 23.32 hours after the SVOM-ECLAIRs trigger, with a total exposure time of around 5 ks.
No X-ray counterpart was detected at the VT position (Li et al., GCN 45230). The estimated flux upper limit is 1.16 x 10^(-13) erg cm^-2 s^-1 in the 0.5–10 keV energy band (90% C.L.).
Optical follow-up observations of the burst were carried out by MASTER (Lipunov et al., GCN 45221), SVOM/VT (Li et al., GCN 45230), WINTER (Mohan et al., GCN 45232) and Liverpool Telescope (Bochenek et al., GCN 45241).
The Burst Advocate (BA) on shift for this alert is Rui-Zhi Li: liruizhi@ynao.ac.cn
Please contact the BA by email if you require additional information.
GCN Circular 45246
Subject
GRB 260726A: Fermi GBM Observation
Date
2026-07-28T22:06:21Z (2 months ago)
From
Lorenzo Scotton at UAH <lscottongcn@outlook.com>
Via
Web form
L. Scotton (UAH), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 23:44:49.07 UT on 26 July 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260726A (trigger 806802294/260726989), which was also detected by SVOM (Liang et al. 2026, GCN 45219; Brunet et al. 2026, GCN 45229).
An optical counterpart is identified by Liverpool Telescope (Bochenek et al. 2026, GCN 45241).
The Fermi GBM real-time localization (GCN 45218) is consistent with the SVOM/ECLAIRs position.
The angle from the Fermi LAT boresight is 21 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.6 to T0+23.8 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.27 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 121 +/- 6 keV.
The event fluence (10-1000 keV) in this time interval is (1.32 +/- 0.10)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.2 s in the 10-1000 keV band is 1.4 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 45241
Subject
GRB 260726A: Liverpool Telescope optical observations
Date
2026-07-28T11:04:58Z (2 months ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
A. Bochenek, D. A. Perley (LJMU), report:
We observed the field of GRB 260726A (Fermi GBM team, GCN 45218; Liang et al., GCN 45219; Brunet et al., GCN 45229) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 8x120s exposures in SDSS r and i filters, starting at 2026-07-28 01:48:36 UT, approximately 26.06 hours after Fermi trigger.
We detect a source in the i-band stacked image at the candidate counterpart position reported by Brunet et al. (GCN 45229) and Li et al. (GCN 45230), and a non-detection in the stacked r-band image, with photometry given below:
MJD (mid) T_mid-T_0 Filter Mag. (AB)
61249.08219 26.23 h r > 22.03
61249.09609 26.56 h i 22.58 ± 0.16
The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
GCN Circular 45232
Subject
GRB 260726A: J-band upper limit with WINTER
Date
2026-07-27T19:19:29Z (2 months ago)
From
tanishk.mohan@iitb.ac.in
Via
Web form
Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 260726A (Fermi GBM, GCN 45218; Liang et al., GCN 45219) 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 2026-07-27T04:50:12.365 UTC in the J band (5.09 hr after the Fermi trigger), consisting of 15*120 sec 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 any new source at the position of SVOM/VT optical candidate (Li et al., GCN 45230) in our stacked image. We obtain the following 5-sigma upper limit: J = 18.92 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 45230
Subject
GRB 260726A: SVOM/VT optical candidate
Date
2026-07-27T17:26:25Z (2 months ago)
Edited On
2026-07-28T02:36:27Z (2 months ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu), Ruizhi Li (YNAO) and Ziming Wang (BNU) report on behalf of the SVOM/VT team.
SVOM/VT performed observations with automatic slew for GRB 260726A detected by SVOM/ECLAIRs (Liang et al., GCN 45219; Brunet et al., GCN 45229) and SVOM/GRM (Liang et al., GCN 45219). This burst was also detected by Fermi/GBM (Fermi GBM team, GCN 45218). The observation started at 2026-07-27T01:28:04 UTC, i.e., 1.72 hr post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
An uncatalogued optical candidate was detected in VT_R within the errorbox of SVOM/MXT (Brunet et al., GCN 45229), compared with the PanSTARRS catalogue. The position is at R.A., Dec. = 356.883196, 52.870077 degrees, equivalent to:
R.A. (J2000) = 23:47:31.93
Dec. (J2000) = +52:52:12.69
with an uncertainty of 0.5 arcsec.
The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | Brightness
1.95 hr VT_R 17*100 s 21.4 +/-0.2 mag
The source showed a fading slope of about -0.2 in VT_R during the observations above.
It was not detected in VT_B, even all the available data were stacked with the total exposure time of 85*100s. The 3 sigma upper limit was estimated to be 24.0 mag in VT_B at the mid time of 4.37 hr.
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 45229
Subject
GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
Date
2026-07-27T17:05:01Z (2 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet (IRAP), P. Maggi (ObAS), D. Götz, D. Turpin (CEA), Ruizhi Li (YNAO), Ziming Wang (BNU), on behalf of the SVOM/ ECLAIRs & MXT team report:
Using the full X band dataset a corrected ECLAIRs position could be derived for GRB 260726A/sb27062614 (Liang et al., GCN 45219).
The improved ECLAIRs position is RA=356.770, Dec=52.851 with a 90% c.l. of 3.7 arcmin.
The burst appeared very close to the Earth limb and only part of the burst signal was considered by the onboard processing, explaining the localization error.
SVOM MXT observed the ECLAIRs error region starting at T0 = 2026-07-26T23:47:09 (106s after trigger time ECLAIRs T0).
Using the full X band dataset, a faint fading source is recovered in the first orbit. Removing the first 150s affected by straylight, the best position is RA=356.903, Dec=52.870 corresponding to:
RA (J2000) = 23h47m36.59s.
Dec (J2000) = +52d52m11.7s
with a statistical 90% C.L. radius of 75.4”.
This detection remains tentative due to the presence of straylight possibly remaining in the MXT data.
This position is 4.95 arcmin from the ECLAIRs position.
This position corrects and supersedes the one reported by (Liang et al., GCN 45219).
The Space 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. ECLAIRs was developed jointly by CNES, IRAP, APC and CEA.
The Burst Advocate (BA) on shift for this burst is Rui-Zhi Li: liruizhi@ynao.ac.cn .
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN Circular 45221
Subject
Fermi GRB 260726A: Global MASTER-Net observations report
Date
2026-07-27T01:46:31Z (2 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260726A ( Fermi GBM team, GCN 45218) errorbox 3746 sec after notice time and 3782 sec after trigger time at 2026-07-27 00:47:51 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 78 deg. The sun altitude is -59.0 deg.
The galactic latitude b = -10 deg., longitude l = 127 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3444915
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
3812 | 2026-07-27 00:47:51 | MASTER-SAAO | (00h 33m 08.03s , +40d 42m 54.8s) | C | 60 | 17.4 |
4815 | 2026-07-27 01:04:33 | MASTER-SAAO | (00h 53m 12.92s , +40d 41m 37.6s) | C | 60 | 17.4 |
4915 | 2026-07-27 01:06:13 | MASTER-SAAO | (01h 11m 16.44s , +38d 48m 24.2s) | C | 60 | 17.1 |
5018 | 2026-07-27 01:07:57 | MASTER-SAAO | (00h 34m 12.82s , +42d 36m 13.8s) | C | 60 | 17.4 |
5327 | 2026-07-27 01:13:06 | MASTER-SAAO | (00h 14m 01.29s , +44d 30m 13.1s) | C | 60 | 17.3 |
5926 | 2026-07-27 01:23:05 | MASTER-SAAO | (01h 13m 23.75s , +40d 41m 40.4s) | C | 60 | 17.1 |
6024 | 2026-07-27 01:24:42 | MASTER-SAAO | (01h 30m 51.35s , +38d 49m 10.7s) | C | 60 | 16.9 |
6121 | 2026-07-27 01:26:19 | MASTER-SAAO | (00h 54m 59.03s , +42d 36m 51.3s) | C | 60 | 17.5 |
6426 | 2026-07-27 01:31:24 | MASTER-SAAO | (00h 35m 31.56s , +44d 32m 11.3s) | C | 60 | 17.3 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html
GCN Circular 45219
Subject
GRB 260726A: SVOM detection of a burst
Date
2026-07-27T00:23:38Z (2 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Yifang Liang(PMO), Wenjin Xie (NAOC), Ruizhi Li (YNAO), Ziming Wang (BNU), Clara Plasse (HKU) report on behalf of the SVOM mission team:
At 2026-07-26T23:45:23 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260726A (SVOM burst-id sb26072614), which was also detected by Fermi/GBM (Fermi GBM team, GCN 45218).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 13 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 14.47 in the [8-50] keV energy band over a time window of 40.96 seconds starting at 2026-07-26T23:45:03.
The localization of the best alert is R.A., Dec. 356.3179, 53.1360 degrees (J2000) with a 90% confidence level (C.L.) radius of 5.68 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst was also detected by SVOM/GRM.
SVOM slewed to the burst. MXT and 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 Rui-Zhi Li: liruizhi@ynao.ac.cn
Please contact the BA by email if you require additional information.
GCN Circular 45218
Subject
GRB 260726A: Fermi GBM Final Real-time Localization
Date
2026-07-26T23:55:25Z (2 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 23:44:49 UT on 26 Jul 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260726A (trigger 806802294.070584 / 260726989).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 19.0, Dec = 52.4 (J2000 degrees, equivalent to J2000 01h 15m, 52d 23'), with a statistical uncertainty of 11.9 degrees.
The angle from the Fermi LAT boresight is 13.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260726989/quicklook/glg_skymap_all_bn260726989.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260726989/quicklook/glg_healpix_all_bn260726989.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260726989/quicklook/glg_lc_medres34_bn260726989.gif