TITLE: GCN CIRCULAR NUMBER: 40596 SUBJECT: GRB 250601A: Fermi GBM Final Real-time Localization DATE: 25/06/01 17:40:08 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 17:29:35 UT on 1 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250601A (trigger 770491780.538054 / 250601729).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 86.5, Dec = -55.7 (J2000 degrees, equivalent to J2000 05h 46m, -55d 42'), with a statistical uncertainty of 4.5 degrees.

The angle from the Fermi LAT boresight is 23.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250601729/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/bn250601729/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250601729/q...

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