TITLE:   GCN CIRCULAR
NUMBER:  40501
SUBJECT: GRB 250520B: Fermi GBM Final Real-time Localization
DATE:    25/05/20 10:46:39 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 10:36:02 UT on 20 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250520B (trigger 769430167.408886 / 250520442).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 100.6, Dec = 68.7 (J2000 degrees, equivalent to J2000 06h 42m, 68d 42'), with a statistical uncertainty of 4.3 degrees.

The angle from the Fermi LAT boresight is 21.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250520442/quicklook/glg_skymap_all_bn250520442.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250520442/quicklook/glg_healpix_all_bn250520442.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250520442/quicklook/glg_lc_medres34_bn250520442.gif