GRB 261024D
GCN Circular 46111
Subject
GRB 261024D: SVOM/GRM observation
Date
2026-10-30T13:30:23Z (2 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
SVOM/GRM team: Xing-Hao Luo, Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Oliver Godet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 261024D (SVOM trigger reference: sb26102402) at 2026-10-24T21:33:06.000 (T0), which is also detected by AstroSat CZTI (A. Goyal et.al., GCN#46040), NuSTAR (G. Waratkar et.al., GCN#46051), Glowbug gamma-ray telescope (C. C. Cheung et.al., GCN#46053), GECAM-B (Xing-Hao Luo et.al., GCN#46061) and Insight-HXMT (Xing-Hao Luo et.al., GCN#46065).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90-value of 11.0 +2.5/-1.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/svgrb261024D.png
In addition, the position of this burst, as determined by GECAM-B (RA = 208.64 deg, Dec = 25.1 deg, with a statistical uncertainty of 5.46 degrees, Xing-Hao Luo et.al., GCN #46061), is located at about 155 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. However, ECLAIRs detected this burst by reflection onto the Earth atmosphere since the Earth fraction was 1 at the time of the burst.
With this localization, the time-averaged spectrum from T0-1.5 to T0+11 s is best fitted by a power law function with an exponential high energy cutoff. The power law index is -1.32 +0.17/-0.16 and the cutoff energy, parameterized as Epeak, is 131 +11/-10 keV. The event fluence (10-1000 keV) in this time interval is (2.22 +0.13/−0.12)E-05 erg/cm^2.
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 46094
Subject
IPN triangulation of GRB 261024D
Date
2026-10-29T15:17:19Z (3 days ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
A. Ridnaia, D. Frederiks, A. Lysenko, V. Panteleeva, D. Svinkin,
and T. Cline on behalf of the Konus-Wind team,
E. Burns on behalf of the IPN,
A. Arya (IITB), G. Waratkar (Caltech/IITB), V. Bhalerao (IITB)
on behalf of AstroSat/CZTI team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
The long-duration GRB 261024D
(AstroSat-CZTI detection: Goyal et al., GCN 46040;
NuSTAR-ACS detection: Waratkar & Grefenstette, GCN 46051;
Glowbug detection: Cheung et al., GCN 46053;
GECAM-B detection: Luo et al., GCN 46061;
Insight-HXMT/HE detection: Luo et al., GCN 46065)
was detected by AstroSat (CZTI), NuSTAR (ACS), SVOM (GRM),
Glowbug, GECAM-B, Insight (HXMT), Konus-Wind and
Mars-Odyssey (HEND) at about 77582 s UT (21:33:02).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
212.913 (14h 11m 39s) +31.361 (+31d 21' 39")
Corners:
211.453 (14h 05m 49s) +23.721 (+23d 43' 15")
214.144 (14h 16m 35s) +38.561 (+38d 33' 38")
214.045 (14h 16m 11s) +38.529 (+38d 31' 45")
211.361 (14h 05m 27s) +23.673 (+23d 40' 23")
---------------------------------------------
The error box area is 1.1 sq. deg, and its maximum
dimension is 15 deg (the minimum one is 4 arcmin).
The Sun distance was 36 deg.
This localization may be improved.
A triangulation map and HEALPix FITS file are posted at
https://www.ioffe.ru/LEA/GRBs/GRB261024_T77582/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 46065
Subject
GRB 261024D: Insight-HXMT/HE detection
Date
2026-10-28T04:41:34Z (5 days ago)
Edited On
2026-10-28T18:16:31Z (4 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
At 2026-10-24T21:33:06.850 (T0), Insight-HXMT/HE detected the GRB 261024D, which is also detected by AstroSat CZTI (A. Goyal et.al., GCN#46040), NuSTAR (G. Waratkar et.al, GCN#46051), Glowbug gamma-ray telescope (C. C. Cheung et.al., GCN#46053), and GECAM-B (Xing-Hao Luo et.al., GCN#46061).
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 9.0 +1.5/-0.5 s. The 1s peak rate, measured from T0+0.25 s, is 2957 cnts/sec. Insight-HXMT/HE detected a total of 11613 counts from this burst.
The HXMT/HE light curve can be found here:
https://www.bursthub.cn/gcn/2026/hxmtgrb261024D.png
All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/
GCN Circular 46061
Subject
GRB 261024D: GECAM-B observation
Date
2026-10-27T14:59:59Z (5 days ago)
Edited On
2026-10-28T18:15:59Z (4 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of 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 261024D, at 2026-10-24T21:33:05.250 UTC (denoted as T0), which is also detected by AstroSat CZTI (A. Goyal.et., GCN#46040), NuSTAR (G. Waratkar et.al., GCN#46051) and Glowbug gamma-ray telescope (C. C. Cheung.et.al., GCN#46053).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 9.5 +1.0/-0.5 s.
The on-ground calculated location, using the GECAM-B trigger data, is RA = 208.64, Dec = 25.1, with a statistical uncertainty of 5.46 degrees.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//gcn/2026/gecambgrb261024D.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 46053
Subject
GRB 261024D: Glowbug gamma-ray detection
Date
2026-10-27T01:24:21Z (6 days ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 261024D, which was also detected by AstroSat (GCN 46040), NuSTAR (GCN 46051), SVOM (sb26102402), and Konus-Wind (Trig_Time 21:33:02.529).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-10-24 21:33:03.736 with a duration of 9.2 s and a total significance of about 43.1 sigma. The light curve comprises a triple-peaked structure.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 46051
Subject
GRB 261024D: NuSTAR detection of prompt emission
Date
2026-10-26T21:58:49Z (6 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 261024D 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 2026-10-24T21:33:05.000 UTC shows a detection of GRB 261024D, also detected by SVOM-GRM (GCN Notices), KONUS-Wind (GCN Notices), and AstroSat-CZTI (GCN 46040).
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 do not see any evidence in the signal above 100 keV in the CZT detectors.
The SVOM-GRM localization at RA = 209.99, Dec = -47.33 implies an offset from the NuSTAR boresight of 100-deg and an offset from the geocenter of 102-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261024D
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 46040
Subject
GRB 261024D: AstroSat CZTI detection of a long burst
Date
2026-10-26T10:14:30Z (6 days ago)
From
ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Via
Web form
A. Goyal (IITB), A. Arya (IITB), S. Puri (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), V. Bhalerao (IITB), A. Vibhute (IUCAA), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a GRB 261024D which was also detected by SVOM/GRM (via notices), and KONUS-Wind (via IPN notices).
The source was detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-10-24 21:33:06.85 UTC. The measured peak count rate associated with the burst is 105 (+28, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 458 (+195, -196) counts. The local mean background count rate was 211 (+2, -2) counts/s. We measure a T90 of 11 (+7, -5) s from the cumulative CZT light curve. We caution that there is a 0.3 s dead time in the CZTI data just in the burst, hence the actual T90 may be slightly longer.
The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a peak at 2026-10-24 21:33:06.86 UTC. The measured peak count rate associated with the burst is 405 (+49, -51) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1698 (+303, -328) counts. The local mean background count rate was 520 (+3 -4) counts/s. We measure a T90 of 13 (+10, -5) s from the cumulative Veto light curve.
CZTI data products like interactive and downloadable light curves for this GRB can be found at:
https://astrosat.iucaa.in/cift/cift_products/530573567.36/S530573567.36_details.html
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb