TITLE: GCN CIRCULAR NUMBER: 40515 SUBJECT: GRB 250521C: Fermi GBM Final Localization DATE: 25/05/21 18:36:09 GMT FROM: Lorenzo Scotton at UAH lscottongcn@outlook.com

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

"At 13:31:01.20 UT on 21 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250521C (trigger 769527066/250521563).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 105.00, Dec = 65.63 (J2000 degrees, equivalent to J2000 7h 0m, +65d 37'), with a statistical uncertainty of 16.05 degrees.

The angle from the Fermi LAT boresight is 91 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/q...

The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250521563/q..."

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