GRB 261024A
GCN Circular 46057
Subject
GRB 261024A: SVOM/GRM observation
Date
2026-10-27T07:22:26Z (a day ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
SVOM/GRM team: Xing-Hao Luo, Yue Wang, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Hui-Yang
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 261024A (SVOM trigger reference: sb26102401) at 2026-10-24T16:23:03.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #46019).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of muplti-pulses with a T90 of 7.0 +1.0/-0.5 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/svgrb261024A.png
In addition, the position of this burst, as determined by BALROG localization of Fermi/GBM (RA = 311.8, Dec = 59.9, the 1 sigma statistical error radius is 1.2 deg, T.Preis et.al., GCN #46020), is located at about 75 degrees from the SVOM optical axis. ECLAIRs was in extended-SAA and in XOFF mode, so no photon was collected.
With this localization, the time-averaged spectrum from T0-3 to T0+9.5 s is best fitted by a power law function with an exponential high energy cutoff. The power law index is -1.07 +/-0.07 and the cutoff energy, parameterized as Epeak, is 138 +10/-9 keV. The event fluence (10-1000 keV) in this time interval is (1.05 +/−0.04)E-05 erg/cm^2.
The localization of GRB 261024A in the ‘Amati’ relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/svgrb261024A_amati.png
The localization of GRB 261024A in the ‘Yonetoku’ relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/svgrb261024A_yonetoku.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/GRM point of contact for this burst is: Xing-Hao Luo (IHEP) (luoxh@ihep.ac.cn)
GCN Circular 46031
Subject
GRB 261024A: NuSTAR detection of prompt emission
Date
2026-10-26T06:39:29Z (3 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 261024A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm triggered at 2026-10-24T16:23:00.790 UTC shows a detection of GRB 261024A, also detected by Fermi-GBM (GCN 46019).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single-peaked burst lasting for about 10-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We also see a faint detection in the signal above 100 keV in the CZT detectors.
The Fermi-GBM localization (GCN 46019) at RA = 317.0, Dec = 63.1 implies an offset from the NuSTAR boresight of 62-deg and an offset from the geocenter of 76-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261024A
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 46020
Subject
GRB 261024A: BALROG localization (Fermi Trigger 814551785 / GRB 261024683)
Date
2026-10-24T16:50:33Z (4 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
814551785 at 16:23:00 on 24 Oct. 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) = 311.8 deg
Decl.(2000.0) = 59.9 deg
The 1 sigma statistical error radius is 1.2 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB261024683/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB261024683/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB261024683/json
GCN Circular 46019
Subject
GRB 261024A: Fermi GBM Final Real-time Localization
Date
2026-10-24T16:33:31Z (4 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 16:23:00 UT on 24 Oct 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261024A (trigger 814551785.78892 / 261024683).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 317.0, Dec = 63.1 (J2000 degrees, equivalent to J2000 21h 07m, 63d 06'), with a statistical uncertainty of 1.6 degrees.
The angle from the Fermi LAT boresight is 49.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261024683/quicklook/glg_skymap_all_bn261024683.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/bn261024683/quicklook/glg_healpix_all_bn261024683.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261024683/quicklook/glg_lc_medres34_bn261024683.gif