TITLE: GCN CIRCULAR NUMBER: 39789 SUBJECT: GRB 250320A: Fermi GBM Final Real-time Localization DATE: 25/03/20 06:16:17 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 06:05:44 UT on 20 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250320A (trigger 764143549.57948 / 250320254).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 263.0, Dec = 47.3 (J2000 degrees, equivalent to J2000 17h 32m, 47d 17'), with a statistical uncertainty of 1.2 degrees.

The angle from the Fermi LAT boresight is 105.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250320254/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/bn250320254/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250320254/q...

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