GRB 260522A
GCN Circular 44697
Subject
GRB 260522A: Fermi GBM Observation
Date
2026-05-23T00:32:40Z (7 days ago)
From
Angus Jameson <abj0023@uah.edu>
Via
Web form
A. Jameson (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 02:15:08.78 UT on 22 May 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260522A (trigger 801108913/260522094),
which was also detected by Fermi-LAT ( et al. 2026, GCN 44689).
The Fermi GBM on-ground location is consistent with the Fermi-LAT position.
The angle from the Fermi LAT boresight is 10 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 1.8 s (50-300 keV). The time-averaged spectrum
from T0-0.7 to T0+0.4 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.48 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 1010 +/- 70 keV.
The event fluence (10-1000 keV) in this time interval is
(8.1 +/- 0.7)E-07 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.51 s in the 10-1000 keV band is 3 +/- 1 ph/s/cm^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 44693
Subject
GRB 260522A: GOTO optical upper limit
Date
2026-05-22T11:34:14Z (8 days ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
D. O'Neill, G. Ramsay, A. Kumar, R. Starling, B. P. Gompertz, S. Belkin, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the Fermi/GBM and LAT detected GRB 260522A (Fermi GBM team, GCN 44687; Bissaldi, E., GCN 44689).
Observations covering the GBM localisation area began at 2026-05-22 03:16:58 UT (+1.03h post trigger) and continued through to 2026-05-22 04:54:51 UT (+2.66h post trigger). Observations covering the LAT position were taken at 2026-05-22 04:14:26 UT (+1.99h post trigger). Images consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks (Lyman et al. 2026).
We found no new transients that could be credibly associated with 260522A within the LAT localisation down to a 5-sigma depth of L<19.8 AB mag.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 44691
Subject
Fermi GRB 260522A: Global MASTER-Net observations report
Date
2026-05-22T09:15:54Z (8 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),
C.Francile, 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 260522A ( Fermi GBM team, GCN 44687) errorbox 20242 sec after notice time and 20291 sec after trigger time at 2026-05-22 07:53:20 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 81 deg. The sun altitude is -37.9 deg.
The galactic latitude b = -40 deg., longitude l = 86 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3330735
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
20321 | 2026-05-22 07:53:20 | MASTER-OAGH | (22h 29m 21.04s , +17d 30m 10.0s) | C | 60 | 17.6 |
20736 | 2026-05-22 08:00:14 | MASTER-OAGH | (22h 31m 10.56s , +15d 35m 11.4s) | C | 60 | 17.8 |
20961 | 2026-05-22 08:04:00 | MASTER-OAGH | (22h 44m 59.44s , +19d 24m 13.9s) | C | 60 | 17.6 |
21293 | 2026-05-22 08:09:31 | MASTER-OAGH | (22h 37m 34.70s , +18d 07m 52.6s) | C | 60 | 18.5 |
21293 | 2026-05-22 08:09:31 | MASTER-OAGH | (22h 45m 20.15s , +17d 30m 06.7s) | C | 60 | 17.7 |
21552 | 2026-05-22 08:13:50 | MASTER-OAGH | (22h 47m 01.86s , +15d 35m 01.0s) | C | 60 | 17.6 |
21552 | 2026-05-22 08:13:50 | MASTER-OAGH | (22h 39m 21.07s , +16d 12m 47.8s) | C | 60 | 18.5 |
21807 | 2026-05-22 08:18:05 | MASTER-OAGH | (22h 31m 54.37s , +12d 23m 27.9s) | C | 60 | 18.2 |
21807 | 2026-05-22 08:18:05 | MASTER-OAGH | (22h 39m 27.63s , +11d 45m 47.0s) | C | 60 | 17.9 |
21879 | 2026-05-22 08:19:17 | MASTER-OAGH | (22h 27m 00.97s , +14d 18m 45.6s) | C | 60 | 18.8 |
21879 | 2026-05-22 08:19:17 | MASTER-OAGH | (22h 34m 37.36s , +13d 41m 11.6s) | C | 60 | 18.3 |
21965 | 2026-05-22 08:20:43 | MASTER-OAGH | (22h 42m 42.24s , +14d 19m 33.9s) | C | 60 | 18.5 |
21965 | 2026-05-22 08:20:43 | MASTER-OAGH | (22h 50m 18.96s , +13d 41m 45.4s) | C | 60 | 17.5 |
22042 | 2026-05-22 08:22:00 | MASTER-OAGH | (22h 53m 22.36s , +20d 01m 39.3s) | C | 60 | 18.4 |
22042 | 2026-05-22 08:22:00 | MASTER-OAGH | (23h 01m 12.71s , +19d 23m 51.7s) | C | 60 | 17.6 |
22189 | 2026-05-22 08:24:27 | MASTER-OAGH | (22h 53m 34.68s , +18d 06m 41.9s) | C | 60 | 18.5 |
22189 | 2026-05-22 08:24:27 | MASTER-OAGH | (23h 01m 19.97s , +17d 28m 52.6s) | C | 60 | 17.6 |
22410 | 2026-05-22 08:28:08 | MASTER-OAGH | (22h 38m 08.15s , +10d 29m 27.1s) | C | 60 | 18.7 |
22410 | 2026-05-22 08:28:08 | MASTER-OAGH | (22h 45m 38.44s , +09d 51m 42.6s) | C | 60 | 18.1 |
22633 | 2026-05-22 08:31:52 | MASTER-OAGH | (22h 47m 29.08s , +12d 24m 15.1s) | C | 60 | 18.6 |
22634 | 2026-05-22 08:31:52 | MASTER-OAGH | (22h 55m 02.26s , +11d 46m 29.2s) | C | 60 | 17.6 |
22713 | 2026-05-22 08:33:12 | MASTER-OAGH | (22h 55m 14.36s , +16d 11m 27.2s) | C | 60 | 18.3 |
22713 | 2026-05-22 08:33:12 | MASTER-OAGH | (23h 02m 54.91s , +15d 33m 41.2s) | C | 60 | 17.8 |
22938 | 2026-05-22 08:36:56 | MASTER-OAGH | (23h 09m 34.33s , +20d 00m 02.3s) | C | 60 | 18.6 |
23357 | 2026-05-22 08:43:56 | MASTER-OAGH | (22h 58m 25.81s , +14d 18m 37.0s) | C | 60 | 18.5 |
23357 | 2026-05-22 08:43:56 | MASTER-OAGH | (23h 06m 02.72s , +13d 40m 58.6s) | C | 60 | 17.9 |
23430 | 2026-05-22 08:45:08 | MASTER-OAGH | (23h 01m 03.75s , +09d 52m 16.5s) | C | 60 | 17.9 |
23430 | 2026-05-22 08:45:08 | MASTER-OAGH | (22h 53m 33.23s , +10d 29m 56.5s) | C | 60 | 18.4 |
23607 | 2026-05-22 08:48:05 | MASTER-OAGH | (23h 03m 00.46s , +12d 23m 19.5s) | C | 60 | 18.2 |
23607 | 2026-05-22 08:48:05 | MASTER-OAGH | (23h 10m 33.91s , +11d 45m 40.8s) | C | 60 | 17.8 |
23679 | 2026-05-22 08:49:17 | MASTER-OAGH | (23h 11m 07.56s , +16d 12m 42.7s) | C | 60 | 18.2 |
23679 | 2026-05-22 08:49:17 | MASTER-OAGH | (23h 18m 48.36s , +15d 35m 03.0s) | C | 60 | 17.5 |
23760 | 2026-05-22 08:50:39 | MASTER-OAGH | (22h 45m 45.40s , +08d 34m 28.4s) | C | 60 | 18.5 |
23760 | 2026-05-22 08:50:39 | MASTER-OAGH | (22h 53m 13.26s , +07d 57m 00.4s) | C | 60 | 18.5 |
24000 | 2026-05-22 08:54:38 | MASTER-OAGH | (23h 14m 05.04s , +14d 17m 27.5s) | C | 60 | 18.1 |
24073 | 2026-05-22 08:55:51 | MASTER-OAGH | (23h 09m 34.28s , +18d 06m 37.0s) | C | 60 | 18.6 |
24073 | 2026-05-22 08:55:51 | MASTER-OAGH | (23h 17m 19.72s , +17d 29m 07.5s) | C | 60 | 18.1 |
24253 | 2026-05-22 08:58:51 | MASTER-OAGH | (23h 09m 06.45s , +10d 28m 56.4s) | C | 60 | 18.7 |
24253 | 2026-05-22 08:58:51 | MASTER-OAGH | (23h 16m 37.32s , +09d 51m 15.3s) | C | 60 | 18.4 |
24325 | 2026-05-22 09:00:04 | MASTER-OAGH | (23h 01m 10.70s , +08d 36m 20.3s) | C | 60 | 18.6 |
24325 | 2026-05-22 09:00:04 | MASTER-OAGH | (23h 08m 39.11s , +07d 58m 43.5s) | C | 60 | 18.2 |
24618 | 2026-05-22 09:04:56 | MASTER-OAGH | (23h 18m 37.97s , +12d 23m 55.7s) | C | 60 | 18.5 |
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 44689
Subject
GRB 260522A: Fermi-LAT detection
Date
2026-05-22T08:24:21Z (8 days ago)
Edited On
2026-05-22T14:43:16Z (8 days ago)
From
Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it>
Via
Web form
E. Bissaldi (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari) and T. Khalil (Johannesburg Univ) report on behalf of the Fermi-LAT team:
At 02:15:08 UT on May 22nd, 2026, Fermi-LAT detected high-energy emission from GRB 260522A, which was also detected by Fermi-GBM (trigger 801108913 / 260522094, GCN #44687).
The best LAT on-ground location is found to be
RA, Dec = 346.67, 9.66 (J2000)
with an error radius of 0.55 deg (90 % containment, statistical error only).
This was 15 deg from the LAT boresight at the time of the trigger.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance.
The photon flux above 100 MeV in the time interval 0 - 50 s after the GBM trigger is (2.89 ± 0.97)E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.14 ± 0.38. The highest-energy photon is a 820 MeV event, which is observed 1.3 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi
(elisabetta.bissaldi@ba.infn.it ).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 44687
Subject
GRB 260522A: Fermi GBM Final Real-time Localization
Date
2026-05-22T02:25:32Z (8 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 02:15:08 UT on 22 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260522A (trigger 801108913.782424 / 260522094).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 343.6, Dec = 14.1 (J2000 degrees, equivalent to J2000 22h 54m, 14d 05'), with a statistical uncertainty of 5.1 degrees.
The angle from the Fermi LAT boresight is 10.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260522094/quicklook/glg_skymap_all_bn260522094.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/bn260522094/quicklook/glg_healpix_all_bn260522094.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260522094/quicklook/glg_lc_medres34_bn260522094.gif