TITLE:   GCN CIRCULAR
NUMBER:  35407
SUBJECT: GRB 231220A: Fermi GBM Final Real-time Localization
DATE:    23/12/20 16:20:38 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 16:10:17 UT on 20 Dec 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231220A (trigger 724781422.403544 / 231220674).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 73.4, Dec = 82.3 (J2000 degrees, equivalent to J2000 04h 53m, 82d 17'), with a statistical uncertainty of 5.0 degrees.

The angle from the Fermi LAT boresight is 136.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231220674/quicklook/glg_skymap_all_bn231220674.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231220674/quicklook/glg_healpix_all_bn231220674.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231220674/quicklook/glg_lc_medres34_bn231220674.gif