TITLE:   GCN CIRCULAR
NUMBER:  42385
SUBJECT: GRB 251023A: Fermi GBM Final Localization Correction
DATE:    25/10/23 07:33:17 GMT
FROM:    A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>

The Fermi GBM team reports the detection of a likely LONG GRB

"At 05:57:43.66 UT on 23 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251023A (trigger 782891868/251023248).
This trigger was initially classified as distant particles by the flight software,
but is in fact a GRB.

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 39.87, Dec = -6.53 (J2000 degrees, equivalent to J2000 02h 39m, -06d 31'),
with a statistical uncertainty of 3.12 degrees.

The angle from the Fermi LAT boresight is 89 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251023248/quicklook/glg_skymap_all_bn251023248.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/bn251023248/quicklook/glg_healpix_all_bn251023248.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251023248/quicklook/glg_lc_medres34_bn251023248.gif"