GRB 231222A

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

At 07:09:54 UT on 22 Dec 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231222A (trigger 724921799.613468 / 231222299).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 161.4, Dec = -36.0 (J2000 degrees, equivalent to J2000 10h 45m, -36d 00'), with a statistical uncertainty of 1.2 degrees.

The angle from the Fermi LAT boresight is 91.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231222299/quicklook/glg_skymap_all_bn231222299.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/bn231222299/quicklook/glg_healpix_all_bn231222299.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231222299/quicklook/glg_lc_medres34_bn231222299.gif

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 231222A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00118

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.