GRB 260604A
GCN Circular 44845
Subject
GRB 260604A: Glowbug gamma-ray detection
Date
2026-06-05T22:03:48Z (13 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 260604A, which was also detected by Fermi/GBM (GCN 44812).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-04 02:24:24.648 with a duration of 4.1 s and a total significance of about 9.8 sigma. The light curve comprises a single peak. Note that data from ~T0-5s 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 44812
Subject
GRB 260604A: Fermi GBM Final Real-time Localization
Date
2026-06-04T02:36:52Z (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 02:24:27 UT on 4 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260604A (trigger 802232672.54125 / 260604100).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 60.4, Dec = -12.8 (J2000 degrees, equivalent to J2000 04h 01m, -12d 48'), with a statistical uncertainty of 9.3 degrees.
The angle from the Fermi LAT boresight is 94.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604100/quicklook/glg_skymap_all_bn260604100.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/bn260604100/quicklook/glg_healpix_all_bn260604100.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260604100/quicklook/glg_lc_medres34_bn260604100.gif