TITLE: GCN CIRCULAR NUMBER: 39597 SUBJECT: GRB 250305A: Fermi GBM Final Real-time Localization DATE: 25/03/05 15:39:31 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 15:28:57 UT on 5 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250305A (trigger 762881342.919284 / 250305645).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 223.7, Dec = -3.0 (J2000 degrees, equivalent to J2000 14h 54m, -3d 00'), with a statistical uncertainty of 5.0 degrees.

The angle from the Fermi LAT boresight is 60.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/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/bn250305645/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/q...

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