TITLE: GCN CIRCULAR NUMBER: 40801 SUBJECT: GRB 250621A: Fermi GBM Final Real-time Localization DATE: 25/06/21 01:25:28 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 01:14:55 UT on 21 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250621A (trigger 772161300.203902 / 250621052).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 129.7, Dec = -25.1 (J2000 degrees, equivalent to J2000 08h 38m, -25d 06'), with a statistical uncertainty of 1.9 degrees.

The angle from the Fermi LAT boresight is 50.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/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/bn250621052/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/q...

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