TITLE:   GCN CIRCULAR
NUMBER:  41473
SUBJECT: GRB 250821B: Fermi GBM Final Localization of a Bright Burst
DATE:    25/08/21 19:00:29 GMT
FROM:    Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>

The Fermi GBM team reports the detection of a likely LONG GRB

"At 16:07:47.46 UT on 21 August 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250821B (trigger 777485272/250821672).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 39.95, Dec = -77.13 (J2000 degrees, equivalent to J2000 2h 39m, -77d 7'),
with a statistical uncertainty of 1.00 degrees.

The angle from the Fermi LAT boresight is 67 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250821672/quicklook/glg_skymap_all_bn250821672.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250821672/quicklook/glg_healpix_all_bn250821672.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250821672/quicklook/glg_lc_medres34_bn250821672.gif"