GCN Circular 44358
Subject
GRB 260421A: Fermi GBM Final Real-time Localization
Event
Date
2026-04-21T02:23:18Z (11 hours 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 02:12:44 UT on 21 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260421A (trigger 798430369.324586 / 260421092).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 198.8, Dec = 62.9 (J2000 degrees, equivalent to J2000 13h 15m, 62d 53'), with a statistical uncertainty of 8.2 degrees.
The angle from the Fermi LAT boresight is 60.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421092/quicklook/glg_skymap_all_bn260421092.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/bn260421092/quicklook/glg_healpix_all_bn260421092.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421092/quicklook/glg_lc_medres34_bn260421092.gif