GCN Circular 26385

G. Vianello (Stanford Univ.), M. Axelsson (KTH & Stockholm Univ.), N. Omodei (Stanford Univ.), M. Arimoto (Kanazawa Univ.), D. Kocevski (NASA/MSFC), J. McEnery (NASA/GSFC), J. Racusin (NASA/GSFC), P. Veres (UAH), F. Longo (University & INFN, Trieste), E. Bissaldi (Politecnico and INFN Bari) and S. Cutini (INFN Perugia) report on behalf of the Fermi-LAT team:

A blind search of Fermi-LAT data from December 7, 2019, discovered a potential GRB at time T0 = 2019-12-07 16:19:01 UT. The transient is detected slightly above the 5 sigma threshold during an interval from T0 to T0 + 50s.

The best LAT on-ground location is found to be

RA, Dec =  237.1, -55.5 (degrees, J2000)

with an error radius of 0.52 deg (90% containment, statistical error only).

The position is in the Galactic plane, and was 52 deg from the LAT boresight at the time of the trigger time, and 65 degrees from the spacecraft zenith.

A power-law fit gives a spectral index of -2.0 +/- 0.3, and the highest-energy photon is a 1.3 GeV event, which is observed at T0 + 49s.

Further analysis is ongoing.

The Fermi-LAT point of contact for this burst is Sara Cutini (sara.cutini@pg.infn.it<mailto:sara.cutini@pg.infn.it>).



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.