TITLE: GCN CIRCULAR NUMBER: 39046 SUBJECT: GRB 250127B: Fermi GBM Final Real-time Localization DATE: 25/01/27 15:25:16 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 15:14:38 UT on 27 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250127B (trigger 759683683.583014 / 250127635).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 126.4, Dec = -14.0 (J2000 degrees, equivalent to J2000 08h 25m, -14d 00'), with a statistical uncertainty of 4.8 degrees.

The angle from the Fermi LAT boresight is 96.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250127635/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/bn250127635/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250127635/q...

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