TITLE: GCN CIRCULAR NUMBER: 38766 SUBJECT: GRB 250101B: Fermi GBM Final Real-time Localization DATE: 25/01/01 23:24:52 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 23:14:12 UT on 1 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250101B (trigger 757466057.652354 / 250101968).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 70.9, Dec = -3.2 (J2000 degrees, equivalent to J2000 04h 43m, -3d 12'), with a statistical uncertainty of 3.3 degrees.

The angle from the Fermi LAT boresight is 49.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250101968/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/bn250101968/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250101968/q...

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