TITLE: GCN CIRCULAR NUMBER: 40792 SUBJECT: GRB 250620B: Fermi GBM Final Real-time Localization DATE: 25/06/20 13:33:28 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 13:22:56 UT on 20 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620B (trigger 772118581.936592 / 250620558).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 67.1, Dec = -30.2 (J2000 degrees, equivalent to J2000 04h 28m, -30d 11'), with a statistical uncertainty of 6.0 degrees.

The angle from the Fermi LAT boresight is 90.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620558/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/bn250620558/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620558/q...

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