GCN Circular 34822

The Fermi GBM team reports the detection of a likely Long GRB.

At 08:05:03.30 UT on 17 October 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB231017A (trigger 719222708 / 231017337).

The on-ground calculated location, using the GBM trigger data, is RA = 88.8, DEC = 57.2 (J2000 degrees, equivalent to 5h 55m, 57d 09'), with a statistical uncertainty of 5.7 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 58 degrees.

The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_skymap_all_bn231017337.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/bn231017337/quicklook/glg_healpix_all_bn231017337.fit

The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_lc_medres34_bn231017337.gif