TITLE: GCN CIRCULAR NUMBER: 39051 SUBJECT: GRB 250128A: Fermi GBM Final Real-time Localization DATE: 25/01/28 10:44:09 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 10:33:42 UT on 28 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250128A (trigger 759753227.594888 / 250128440).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 284.0, Dec = 62.3 (J2000 degrees, equivalent to J2000 18h 56m, 62d 17'), with a statistical uncertainty of 5.4 degrees.

The angle from the Fermi LAT boresight is 109.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128440/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/bn250128440/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128440/q...

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