GRB 260808A
GCN Circular 45369
Subject
GRB 260808A: SVOM/GRM observation
Date
2026-08-13T03:20:24Z (14 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
SVOM/GRM team: Xing-Hao Luo, Chen-Wei Wang, Yue Wang, Jin-Ye Luo, Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Marius Brunet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM observed GRB 260808A at 2026-08-08T02:51:45.500 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45313), NuSTAR (G. Waratkar et.al., GCN#45327) , CGBM (M.L. Cherry et.al., GCN#45347) and GECAM-B (Xing-Hao Luo et.al., GCN#45356). Unfortunately, ECLAIRs was not collecting data at the time of the burst.
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 21 +/-2 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//gcn/2026/svgrb260808A.png
In addition, the position of this burst, as determined by Fermi/GBM (RA=341.8 , DEC=14.1, with a statistical uncertainty of 2.2 degrees, Fermi GBM team, GCN #45313), is located at about 21 degrees from the SVOM optical axis, which is inside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-5.5 to T0+20.5 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.16 +0.11/-0.10 and the cutoff energy, parameterized as Epeak, is 194 +45/-30 keV. The event fluence (10-1000keV) in this time interval is (7.74 +0.68/-0.61)E-06 erg/cm^2.
The 'Amati' relation diagram of GRB 260808A is shown at:
https://www.bursthub.cn//gcn/2026/svgrb260808A_amati.png
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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Xing-Hao Luo (luoxh@ihep.ac.cn)
GCN Circular 45356
Subject
GRB 260808A: GECAM-B observation
Date
2026-08-11T10:49:01Z (15 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Chen-Wei Wang, Ren-Yang Zhao, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered on-ground by GRB 260808A, at 2026-08-08T02:51:45.500 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45313), NuSTAR (G. Waratkar et.al., GCN#45327) and CGBM (M.L. Cherry et.al., GCN#45347).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 14 +/-2 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//gcn/2026/gecambgrb260808A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular 45347
Subject
GRB 260808A: CALET Gamma-Ray Burst Monitor detection
Date
2026-08-10T13:51:56Z (16 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
N. Cannady (GSFC), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260808A
at 02:51:52.41 UTC on 8 August 2026 (trigger #1470192693;
https://cgbm.calet.jp/cgbm_trigger/flight/1470192693/index.html).
No real-time CGBM GCN notice was distributed about this trigger because
the real-time communication from the ISS was off (loss of signal).
This event was also reported by Fermi GBM (Fermi GBM Team, GCN #45313;
Preis and Greiner, GCN #45315) and NuSTAR (Waratkar et al., GCN #45327).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure starting
at T-10.6 s and ending at T+4.4 s.
The T90 and T50 durations measured with the SGM data are 13.4 +/- 0.9 s
and 7.1 +/- 0.6 s in the 40-1000 keV band, respectively.
The ground-processed light curve is available at:
https://cgbm.calet.jp/cgbm_trigger/ground/1470192693/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 45327
Subject
GRB 260808A: NuSTAR detection of prompt emission
Date
2026-08-09T07:43:36Z (17 days ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:
The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260808A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm, triggered at 2026-08-08T02:51:42.310 UTC, shows a detection of GRB 260808A, also detected by Fermi-GBM (GCN 45313).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single episode with two peaks lasting for about 20-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors.
The Fermi-GBM localization (GCN 45313) at RA = 341.8, Dec = 14.1 implies an offset from the NuSTAR boresight of 76-deg (i.e. from the side) and an offset from the geocenter of 135-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260808A
Information on NuSTAR SINGS can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/
NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.
GCN Circular 45315
Subject
GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
Date
2026-08-08T06:09:23Z (19 days ago)
From
Jochen Greiner at MPE <jcgrog@mpe.mpg.de>
Via
email
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
807850307 at 02:51:42 on 08 Aug. 2026 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position is:
RA(2000.0) = 344.1 deg
Decl.(2000.0) = 11.9 deg
The 1 sigma statistical error radius is 2.9 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB260808119/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB260808119/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB260808119/json
GCN Circular 45314
Subject
Fermi GRB 260808A: Global MASTER-Net observations report
Date
2026-08-08T04:46:20Z (19 days 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260808A ( Fermi GBM team, GCN 45313) errorbox 99 sec after notice time and 136 sec after trigger time at 2026-08-08 02:53:58 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 68 deg. The sun altitude is -61.1 deg.
The galactic latitude b = -39 deg., longitude l = 84 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3463356
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
152 | 2026-08-08 02:53:58 | MASTER-OAFA | (22h 48m 26.72s , +15d 27m 39.0s) | C | 30 | 17.9 |
188 | 2026-08-08 02:54:35 | MASTER-OAFA | (22h 48m 26.71s , +15d 27m 41.6s) | C | 30 | 18.1 |
229 | 2026-08-08 02:55:11 | MASTER-OAFA | (22h 48m 26.79s , +15d 27m 43.8s) | C | 40 | 18.1 |
281 | 2026-08-08 02:55:58 | MASTER-OAFA | (22h 48m 26.78s , +15d 27m 46.4s) | C | 50 | 18.4 |
342 | 2026-08-08 02:56:53 | MASTER-OAFA | (22h 48m 26.83s , +15d 27m 49.2s) | C | 60 | 18.5 |
641 | 2026-08-08 03:01:23 | MASTER-OAFA | (22h 46m 41.95s , +14d 00m 48.5s) | C | 120 | 19.1 |
777 | 2026-08-08 03:03:29 | MASTER-OAFA | (22h 46m 41.99s , +14d 00m 54.5s) | C | 140 | 19.2 |
938 | 2026-08-08 03:05:55 | MASTER-OAFA | (22h 46m 41.94s , +14d 01m 00.1s) | C | 170 | 19.3 |
1060 | 2026-08-08 03:08:52 | MASTER-OAFA | (22h 46m 41.89s , +14d 01m 04.3s) | C | 60 | 18.8 |
1126 | 2026-08-08 03:09:58 | MASTER-OAFA | (22h 46m 41.85s , +14d 01m 06.4s) | C | 60 | 18.9 |
1191 | 2026-08-08 03:11:03 | MASTER-OAFA | (22h 46m 41.82s , +14d 01m 09.3s) | C | 60 | 18.9 |
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 45313
Subject
GRB 260808A: Fermi GBM Final Real-time Localization
Date
2026-08-08T03:02:15Z (19 days 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 02:51:42 UT on 8 Aug 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260808A (trigger 807850307.310674 / 260808119).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 341.8, Dec = 14.1 (J2000 degrees, equivalent to J2000 22h 47m, 14d 05'), with a statistical uncertainty of 2.2 degrees.
The angle from the Fermi LAT boresight is 72.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260808119/quicklook/glg_skymap_all_bn260808119.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/bn260808119/quicklook/glg_healpix_all_bn260808119.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260808119/quicklook/glg_lc_medres34_bn260808119.gif