GRB 260506B
GCN Circular 44975
Subject
GRB 260506B: cubesat Avion detection
Date
2026-06-18T09:57:49Z (8 days ago)
From
Andrey Bogomolov at Moscow State University <aabboogg@srd.sinp.msu.ru>
Via
email
From Andrey Bogomolov at Moscow State University <aabboogg@srd.sinp.msu.ru>
A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev
on behalf of the MSU “Sozvezdie-270” team, report:
At 2026-05-06 ~13:07:28 UT the long-duration GRB 260506B (Fermi GBM detection: GCN #44484, AstroSat CZTI detection: GCN #44503, Glowbug detection: GCN #44559) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1].
Total amount of photons detected by Avion is 428 (energy band >30 keV), it corresponds to a fluence of ~3.8*10^(-6) erg/cm^2 in the range 30-500 keV.
LC in the energy range of 30-500 keV has a multiple peak structure including a faint peak of ~1 s duration at ~13:07:29 with a maximum flux of ~60 phot/(cm^2*s) and a main peak of ~5 s duration at ~13:07:40 with a maximum flux of ~80 phot/(cm^2*s) at ~13:07:42 UT.
А total duration (T90) of the burst is ~15 s.
The light curve obtained by Avion is available here:
https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260506B_LC_Avion.png
Parameters of GRB 260506B as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en
Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s.
[1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21
[2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282
GCN Circular 44559
Subject
GRB 260506B: Glowbug gamma-ray detection
Date
2026-05-11T17:12:04Z (a month 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 260506B, which was also detected by Fermi/GBM (GCN 44484, 44485) and AstroSat/CZTI (GCN 44503).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-06 13:07:30.824 with a duration of 20.5 s and a total significance of about 34 sigma. The lightcurve comprises a faint initial peak at ~T0+1s, a complex structure from ~T0+7s to +15s, and a peak at ~T0+21s — the peaks correspond to the brightest features seen in the GBM lightcurve. Note that data from ~T0-1s to +1s 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. 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 44503
Subject
GRB 260506B: AstroSat CZTI detection
Date
2026-05-08T19:22:25Z (2 months ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
S. Salunke (IUCAA), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), 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 CIFT2 framework showed the detection of GRB 260506B which is also detected by the Fermi/GBM (Fermi GBM team, GCN Circ. 44484).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-05-06 13:07:41.9 UTC. The measured peak count rate associated with the burst is 129 (+37, -17) counts/s above the background in the combined data of all four quadrants, with a total of 899 (+239, -328) counts. The local mean background count rate was 289 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 22 (+12, -15) s. We caution that there is a 0.3 s dead time in the CZTI data in the burst, hence the actual T90 may be slightly longer.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-05-06 13:07:42.0 UTC. The measured peak count rate associated with the burst is 440 (+67, -69) counts/s above the background in the combined data of all quadrants, with a total of 3325 (+520, -551) counts. The local mean background count rate was 1313 (+4, -4) counts/s. We measure a T90 of 36 (+3, -7) s from the cumulative Veto light curve.
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 data products like interactive and downloadable light curves for this GRB can be found at:
https://astrosat.iucaa.in/cift/cift_products/515768858.51/S515768858.51_details.html
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 44485
Subject
GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
Date
2026-05-06T14:01:40Z (2 months 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
799765648 at 13:07:23 on 06 May 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) = 280.7 deg
Decl.(2000.0) = -6.1 deg
The 1 sigma statistical error radius is 1.5 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB260506547/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB260506547/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB260506547/json
GCN Circular 44484
Subject
GRB 260506B: Fermi GBM Final Real-time Localization
Date
2026-05-06T13:18:06Z (2 months 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 13:07:23 UT on 6 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260506B (trigger 799765648.964258 / 260506547).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 280.5, Dec = -0.5 (J2000 degrees, equivalent to J2000 18h 41m, 0d 30'), with a statistical uncertainty of 1.8 degrees.
The angle from the Fermi LAT boresight is 44.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260506547/quicklook/glg_skymap_all_bn260506547.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/bn260506547/quicklook/glg_healpix_all_bn260506547.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260506547/quicklook/glg_lc_medres34_bn260506547.gif