TITLE: GCN CIRCULAR NUMBER: 40094 SUBJECT: GRB 250406A: Fermi GBM Final Real-time Localization DATE: 25/04/06 14:48:42 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 14:38:11 UT on 6 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250406A (trigger 765643096.56557 / 250406610).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 6.2, Dec = -63.2 (J2000 degrees, equivalent to J2000 00h 24m, -63d 12'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 29.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/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/bn250406610/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/q...

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