TITLE: GCN CIRCULAR NUMBER: 39389 SUBJECT: GRB 250220A: Fermi GBM Final Real-time Localization DATE: 25/02/20 22:19:28 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 22:09:01 UT on 20 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250220A (trigger 761782146.820828 / 250220923).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 194.6, Dec = -60.9 (J2000 degrees, equivalent to J2000 12h 58m, -60d 53'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 171.0 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220923/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/bn250220923/q...

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220923/q...

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