TITLE:   GCN CIRCULAR
NUMBER:  40571
SUBJECT: GRB 250529B: Fermi GBM Final Real-time Localization
DATE:    25/05/29 11:08:59 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 10:58:24 UT on 29 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250529B (trigger 770209109.316756 / 250529457).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 149.1, Dec = 71.6 (J2000 degrees, equivalent to J2000 09h 56m, 71d 35'), with a statistical uncertainty of 2.9 degrees.

The angle from the Fermi LAT boresight is 121.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250529457/quicklook/glg_skymap_all_bn250529457.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/bn250529457/quicklook/glg_healpix_all_bn250529457.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250529457/quicklook/glg_lc_medres34_bn250529457.gif