GCN Circular 44369
Subject
GRB 260421C: Fermi GBM Final Real-time Localization
Event
Date
2026-04-21T08:35:58Z (16 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 LONG GRB
At 08:25:19 UT on 21 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260421C (trigger 798452724.59066 / 260421351).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 295.0, Dec = 64.2 (J2000 degrees, equivalent to J2000 19h 40m, 64d 12'), with a statistical uncertainty of 3.1 degrees.
The angle from the Fermi LAT boresight is 59.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421351/quicklook/glg_skymap_all_bn260421351.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/bn260421351/quicklook/glg_healpix_all_bn260421351.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421351/quicklook/glg_lc_medres34_bn260421351.gif