GRB 260923A
GCN Circular 45749
Subject
GRB 260923A: Glowbug gamma-ray detection
Date
2026-09-25T18:07:16Z (9 hours 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 260923A, which was also detected by Fermi/GBM (GCN 45710) and Insight-HXMT/HE (GCN 45738).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-09-23 23:41:32.368 with a duration of 88.3 s and a total significance of about 93.3 sigma. The light curve comprises a complex multi-peaked structure. Note that data from throughout the burst interval suffered from deadtime in various detectors.
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 45738
Subject
GRB 260923A: Insight-HXMT/HE detection
Date
2026-09-25T04:25:59Z (a day ago)
From
yzh807926@163.com
Via
Web form
Zheng-Hang Yu, Wen-Jun Tan and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
At 2026-09-23T23:41:36 (T0), Insight-HXMT/HE detected GRB 260923A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #45710)
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 13.8 +8.0/-4.2 s. The 1 s peak rate, measured from T0+30 s, is 667.90 cnts/sec. Insight-HXMT/HE detected a total of 4029 counts from this burst.
The Insight-HXMT/HE light curve can be found here:
https://www.bursthub.cn/gcn/2026/9/hxmtgrb260923A.png
All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Normal 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://www.hxmt.org
GCN Circular 45711
Subject
Fermi GRB 260923A: Global MASTER-Net observations report
Date
2026-09-24T00:16:29Z (2 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA)
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 (Lomonosov MSU)
D.Buckley (SAAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
A.Sosnovskij (Lomonosov MSU)
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
R.Rebolo (The Instituto de Astrofisica de Canarias)
O.Gress, N.Budnev(ISU)
MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260923A ( Fermi GBM team, GCN 45710) errorbox 37 sec after notice time and 59 sec after trigger time at 2026-09-23 23:42:36 UT, with upper limit up to 18.6 mag. Observations started at twilight. The observations began at zenith distance = 43 deg. The sun altitude is -15.6 deg.
The galactic latitude b = -57 deg., longitude l = 332 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3510396
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
65 | 2026-09-23 23:42:36 | MASTER-OAFA | (22h 46m 25.67s , -53d 14m 22.7s) | C | 10 | 16.3 |
85 | 2026-09-23 23:42:36 | MASTER-OAFA | (22h 46m 25.66s , -53d 14m 22.6s) | C | 50 | 17.6 | Coadd
86 | 2026-09-23 23:42:52 | MASTER-OAFA | (22h 46m 25.64s , -53d 14m 21.4s) | C | 20 | 17.1 |
112 | 2026-09-23 23:43:17 | MASTER-OAFA | (22h 46m 25.63s , -53d 14m 20.2s) | C | 20 | 17.8 |
153 | 2026-09-23 23:43:54 | MASTER-OAFA | (22h 53m 16.70s , -53d 46m 50.8s) | C | 30 | 18.1 |
188 | 2026-09-23 23:43:54 | MASTER-OAFA | (22h 53m 16.70s , -53d 46m 50.8s) | C | 100 | 18.3 | Coadd
189 | 2026-09-23 23:44:30 | MASTER-OAFA | (22h 53m 16.68s , -53d 46m 49.0s) | C | 30 | 18.0 |
230 | 2026-09-23 23:45:06 | MASTER-OAFA | (22h 53m 16.69s , -53d 46m 47.0s) | C | 40 | 17.6 |
281 | 2026-09-23 23:45:52 | MASTER-OAFA | (22h 53m 16.67s , -53d 46m 45.4s) | C | 50 | 17.2 |
351 | 2026-09-23 23:45:52 | MASTER-OAFA | (22h 53m 16.67s , -53d 46m 45.4s) | C | 190 | 18.3 | Coadd
342 | 2026-09-23 23:46:48 | MASTER-OAFA | (22h 53m 16.66s , -53d 46m 42.5s) | C | 60 | 17.5 |
418 | 2026-09-23 23:47:54 | MASTER-OAFA | (22h 53m 16.71s , -53d 46m 39.5s) | C | 80 | 18.1 |
509 | 2026-09-23 23:49:20 | MASTER-OAFA | (22h 53m 16.69s , -53d 46m 35.9s) | C | 90 | 18.4 |
1308 | 2026-09-24 00:02:54 | MASTER-OAFA | (23h 04m 22.40s , -54d 00m 27.3s) | C | 60 | 17.9 |
1368 | 2026-09-24 00:02:54 | MASTER-OAFA | (23h 04m 22.39s , -54d 00m 27.3s) | C | 180 | 18.6 | Coadd
1383 | 2026-09-24 00:04:09 | MASTER-OAFA | (23h 04m 16.72s , -54d 01m 03.5s) | C | 60 | 17.8 |
1459 | 2026-09-24 00:05:25 | MASTER-OAFA | (23h 17m 55.73s , -54d 00m 36.9s) | C | 60 | 17.8 |
1534 | 2026-09-24 00:06:40 | MASTER-OAFA | (23h 18m 01.94s , -54d 01m 34.3s) | C | 60 | 17.6 |
1610 | 2026-09-24 00:07:56 | MASTER-OAFA | (23h 04m 18.40s , -54d 01m 52.7s) | C | 60 | 17.7 |
1688 | 2026-09-24 00:09:14 | MASTER-OAFA | (23h 18m 00.49s , -54d 02m 25.2s) | C | 60 | 18.1 |
1766 | 2026-09-24 00:10:31 | MASTER-OAFA | (23h 04m 20.74s , -54d 00m 05.6s) | C | 60 | 17.9 |
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 45710
Subject
GRB 260923A: Fermi GBM Final Real-time Localization
Date
2026-09-23T23:52:10Z (2 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 23:41:36 UT on 23 Sep 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260923A (trigger 811899701.42774 / 260923987).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 345.9, Dec = -54.1 (J2000 degrees, equivalent to J2000 23h 03m, -54d 06'), with a statistical uncertainty of 2.1 degrees.
The angle from the Fermi LAT boresight is 30.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260923987/quicklook/glg_skymap_all_bn260923987.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/bn260923987/quicklook/glg_healpix_all_bn260923987.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260923987/quicklook/glg_lc_medres34_bn260923987.gif