GCN Circular 44360
Subject
GRB 260421B: Fermi GBM Final Real-time Localization
Event
Date
2026-04-21T04:22:36Z (9 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 04:13:21 UT on 21 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260421B (trigger 798437606.166588 / 260421176).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 188.8, Dec = -17.8 (J2000 degrees, equivalent to J2000 12h 35m, -17d 48'), with a statistical uncertainty of 2.4 degrees.
The angle from the Fermi LAT boresight is 58.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421176/quicklook/glg_skymap_all_bn260421176.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/bn260421176/quicklook/glg_healpix_all_bn260421176.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421176/quicklook/glg_lc_medres34_bn260421176.gif