TITLE: GCN CIRCULAR NUMBER: 39692 SUBJECT: GRB 250312B: Fermi GBM Final Localization DATE: 25/03/12 21:55:01 GMT FROM: Lorenzo Scotton at UAH lscottongcn@outlook.com

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

"At 20:36:56.64 UT on 12 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250312B (trigger 763504621/250312859).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 180.86, Dec = -50.96 (J2000 degrees, equivalent to J2000 12h 3m, -50d 57'), with a statistical uncertainty of 4.87 degrees.

The angle from the Fermi LAT boresight is 105 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250312859/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/bn250312859/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250312859/q..."

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