TITLE: GCN CIRCULAR NUMBER: 40314 SUBJECT: GRB 250502B: Fermi GBM Final Real-time Localization DATE: 25/05/02 10:24:22 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM do_not_reply@GIOC.nsstc.nasa.gov

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

At 10:13:53 UT on 2 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250502B (trigger 767873638.16821 / 250502426).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.3, Dec = 14.5 (J2000 degrees, equivalent to J2000 20h 49m, 14d 30'), with a statistical uncertainty of 2.3 degrees.

The angle from the Fermi LAT boresight is 56.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250502426/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/bn250502426/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250502426/q...

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