GRB 260601A
GCN Circular 44817
Subject
GRB 260601A: CALET Gamma-Ray Burst Monitor detection
Date
2026-06-04T08:23:39Z (17 minutes ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita,
Y. Kawakubo (AGU), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) detected the short
GRB 260601A at 11:00:12.042 UTC on 1 June 2026 (trigger #1464346716;
https://cgbm.calet.jp/cgbm_trigger/flight/1464346716/index.html).
A CGBM Notice was distributed in near real time.
This event was also reported by Fermi GBM (The Fermi GBM team, GCN #44755;
Holzmann Airasca et al., GCN #44760), Glowbug (Cheung et al., GCN #44763),
GECAM-B (Wang et al., GCN #44778), SVOM/GRM (Wang et al., GCN #44793), and
KONUS-Wind (IPN_RAW Notice at 2026-06-01 11:00:09.16 UTC).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure, starting at T+0.40 s,
peaking at T+0.50 s, and ending at T+0.59 s.
The T90 and T50 durations measured with the SGM data are 0.18 +/- 0.01 s
and 0.05 +/- 0.03 s in the 40-1000 keV band, respectively.
The ground-processed light curve is available at:
https://cgbm.calet.jp/cgbm_trigger/ground/1464346716/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 44793
Subject
GRB 260601A: SVOM/GRM observation of a short burst
Date
2026-06-03T07:52:54Z (a day ago)
From
Yue Wang <m18509381757@163.com>
Via
Web form
SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Frédéric Daigne (IAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered on-ground by GRB 260601A at 2026-06-01T11:00:12.500 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44755) and GECAM-B (Yue Wang et. al., GCN #44778).
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 0.20 +0.47/-0.09 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260601A.png
In addition, the position of this burst, as determined by Fermi/GBM (RA = 15.1, Dec = 44.4, Error = 2.0, GCN #44755), is located at about 116 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-0.06 to T0+0.16 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.04 +0.15/-0.17 and the cutoff energy, parameterized as Epeak, is 899 +210/-150 keV. The event fluence (10-1000 keV) in this time interval is (3.28 +0.138/−0.13)E-06 erg/cm^2.
The localization of GRB 260601A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260601A_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/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang@ihep.ac.cn)
GCN Circular 44778
Subject
GRB 260601A: GECAM-B observation of a short burst
Date
2026-06-03T00:54:14Z (a day ago)
From
Yue Wang <m18509381757@163.com>
Via
Web form
Yue Wang, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 260601A at 2026-06-01T11:00:12.500 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44755).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of muplti-pulses with a duration (T90) of 0.78 +0.21/-0.57 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260601A.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 44763
Subject
GRB 260601A: Glowbug gamma-ray detection of a short burst
Date
2026-06-02T01:04:27Z (2 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 260601A, which was also detected by Fermi/GBM (GCN 44755, 44760) and CALET (Trigger ID Num 1464346716).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-01 11:00:11.408 with a duration of 0.26 s and a total significance of about 77 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. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[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 44760
Subject
GRB 260601A: Fermi GBM Observation
Date
2026-06-01T18:13:56Z (3 days ago)
From
A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>
Via
Web form
A. Holzmann Airasca (UniTrento and INFN Bari) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 11:00:12.44 UT on 01 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260601A (trigger 802004417/260601458).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 15.06, Dec = 44.38 (J2000 degrees, equivalent to
J2000 1h 0m, +44d 22'), with a statistical uncertainty of 2.03 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).
The angle from the Fermi LAT boresight is 30 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 0.8 s (50-300 keV). The time-averaged spectrum
from T0-0.07 to T0+0.34 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.63 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 960 +/- 30 keV.
The event fluence (10-1000 keV) in this time interval is
(2.08 +/- 0.06)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.064 s in the 10-1000 keV band is 40 +/- 1 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 750 +/- 20 keV, alpha = -0.57 +/- 0.05 and beta = -2.0 +/- 0.2.
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 44756
Subject
Fermi GRB 260601A: Global MASTER-Net observations report
Date
2026-06-01T11:45:38Z (3 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-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) started inspect of the Fermi GRB 260601A ( Fermi GBM team, GCN 44755) errorbox 301 sec after notice time and 327 sec after trigger time at 2026-06-01 11:05:39 UT, with upper limit up to 19.5 mag. Observations started at twilight. The observations began at zenith distance = 53 deg. The sun altitude is -13.8 deg.
The galactic latitude b = -18 deg., longitude l = 125 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3352995
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
357 | 2026-06-01 11:05:39 | MASTER-OAGH | (00h 50m 13.85s , +45d 57m 12.7s) | C | 60 | 19.4 |
430 | 2026-06-01 11:06:52 | MASTER-OAGH | (00h 38m 00.15s , +44d 39m 27.6s) | C | 60 | 19.1 |
430 | 2026-06-01 11:06:52 | MASTER-OAGH | (00h 48m 30.18s , +44d 02m 36.0s) | C | 60 | 19.5 |
576 | 2026-06-01 11:09:18 | MASTER-OAGH | (00h 52m 04.36s , +47d 50m 39.9s) | C | 60 | 19.0 |
678 | 2026-06-01 11:10:30 | MASTER-OAGH | (00h 59m 12.69s , +44d 07m 39.1s) | P- | 120 | 16.9 |
678 | 2026-06-01 11:10:30 | MASTER-OAGH | (01h 01m 18.88s , +43d 31m 06.4s) | P| | 120 | 17.8 |
798 | 2026-06-01 11:10:30 | MASTER-OAGH | (01h 01m 18.88s , +43d 31m 06.6s) | P| | 360 | 18.0 | Coadd
807 | 2026-06-01 11:12:39 | MASTER-OAGH | (00h 59m 19.74s , +44d 08m 01.8s) | P- | 120 | 16.9 |
807 | 2026-06-01 11:12:39 | MASTER-OAGH | (01h 01m 25.92s , +43d 31m 26.7s) | P| | 120 | 17.8 |
936 | 2026-06-01 11:14:48 | MASTER-OAGH | (00h 59m 15.81s , +44d 09m 26.1s) | P- | 120 | 16.9 |
936 | 2026-06-01 11:14:48 | MASTER-OAGH | (01h 01m 22.64s , +43d 32m 53.3s) | P| | 120 | 17.5 |
1065 | 2026-06-01 11:16:57 | MASTER-OAGH | (00h 59m 15.96s , +44d 07m 29.9s) | P- | 120 | 16.6 |
1065 | 2026-06-01 11:16:57 | MASTER-OAGH | (01h 01m 22.92s , +43d 30m 56.4s) | P| | 120 | 17.4 |
1173 | 2026-06-01 11:19:15 | MASTER-OAGH | (00h 59m 32.67s , +44d 39m 48.6s) | C | 60 | 18.5 |
1173 | 2026-06-01 11:19:15 | MASTER-OAGH | (01h 09m 59.11s , +44d 02m 59.4s) | C | 60 | 18.3 |
1246 | 2026-06-01 11:20:28 | MASTER-OAGH | (00h 57m 41.97s , +42d 45m 11.1s) | C | 60 | 18.2 |
1246 | 2026-06-01 11:20:28 | MASTER-OAGH | (01h 07m 49.03s , +42d 08m 22.9s) | C | 60 | 18.1 |
1319 | 2026-06-01 11:21:41 | MASTER-OAGH | (01h 01m 31.23s , +46d 34m 48.3s) | C | 60 | 18.1 |
1319 | 2026-06-01 11:21:41 | MASTER-OAGH | (01h 12m 18.99s , +45d 57m 59.6s) | C | 60 | 18.0 |
1393 | 2026-06-01 11:22:55 | MASTER-OAGH | (00h 55m 58.79s , +40d 51m 00.4s) | C | 60 | 17.8 |
1466 | 2026-06-01 11:24:08 | MASTER-OAGH | (00h 47m 06.39s , +42d 09m 10.0s) | C | 60 | 18.1 |
1541 | 2026-06-01 11:25:23 | MASTER-OAGH | (01h 18m 18.85s , +42d 46m 18.7s) | C | 60 | 17.2 |
1686 | 2026-06-01 11:27:48 | MASTER-OAGH | (01h 20m 55.25s , +44d 40m 22.4s) | C | 60 | 17.2 |
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 44755
Subject
GRB 260601A: Fermi GBM Final Real-time Localization
Date
2026-06-01T11:10:43Z (3 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 SHORT GRB
At 11:00:12 UT on 1 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260601A (trigger 802004417.438878 / 260601458).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 15.1, Dec = 44.4 (J2000 degrees, equivalent to J2000 01h 00m, 44d 23'), with a statistical uncertainty of 2.0 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/bn260601458/quicklook/glg_skymap_all_bn260601458.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/bn260601458/quicklook/glg_healpix_all_bn260601458.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260601458/quicklook/glg_lc_medres34_bn260601458.gif