TITLE: GCN CIRCULAR NUMBER: 26598 SUBJECT: GRB 191227A: Marginal detection by Fermi-LAT DATE: 19/12/27 17:15:42 GMT FROM: Francesco Longo at U of Trieste,INFN Trieste F. Fana Dirirsa (Univ. of Johannesburg), F. Longo (University & INFN, Trieste), M. Axelsson (KTH & Stockholm Univ.), D. Kocevski (NASA/MSFC) and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: On December 27, 2019, Fermi-LAT marginally detected high-energy emission from GRB 191227A, which was also detected by Fermi-GBM (GCN 26593) and Swift/BAT (Melandri et al, GCN 26595). The best LAT on-ground location is found to be RA, Dec 318.0, -16.9 (degrees, J2000) with an error radius of 0.33 deg (90% containment, statistical error only). This was 96 deg from the LAT boresight at the time of the GBM trigger and entered in the LAT field of view around 1 ks later. The localisation is consistent with the Swift/BAT position. The detection significance lies just below the 5-sigma threshold, but more than 3 photons with >90% probability to be associated with the GRB are found in the time interval up to 10ks after the GBM trigger. The photon flux above 100 MeV in this time interval is (9 +/- 4) e-7 ph/cm2/s. The estimated photon index above 100 MeV is -2.0 +/- 0.3. Further analysis is ongoing. The Fermi-LAT point of contact for this burst is Feraol Fana Dirirsa (fdirirsa@uj.ac.za) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.