[vsnet-grb-info 25486] GRB 200415A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27586
SUBJECT: GRB 200415A: Fermi-LAT detection 
DATE:    20/04/15 19:29:32 GMT
FROM:    Nicola Omodei at Stanford U.  <nicola.omodei at slac.stanford.edu>

N. Omodei (Stanford University), M. Axelsson (KTH & Stockholm Univ.), F. Piron (CNRS/IN2P3/LUPM), F. Longo (University and INFN, Trieste), D. Kocevski (NASA/MSFC), E. Bissaldi (Politecnico & INFN Bari) and A. Berretta (University & INFN Perugia) 
report on behalf of the Fermi-LAT Collaboration:

On April 15, 2020, Fermi-LAT detected high-energy emission from GRB 200415A, which was also detected by Fermi-GBM (trigger 608633290/200415367).

The GRB is marginally detected at high energy (>100 MeV) by Fermi-LAT at a location of: 
RA, Dec = 11.0, -25.1 (degrees, J2000) with an error radius of 0.5 deg (90% containment, statistical error only).

This was 49 deg from the LAT boresight at the time of the GBM trigger,  T0 = 08:48:05.56 UT, and 8.1 deg from the GBM final ground position (The Fermi GBM team, GCN27579). The location is also consistent within errors with the location from the IPN (Svinkin et al., GCN27585).

The photon flux above 100 MeV in the time interval 0-500 seconds after the GBM trigger is 3.4e-06 +/- 2.1e-06 ph/cm^2/s. The estimated photon index above 100 MeV is -1.7 +/ - 0.3. The highest-energy photon is a 1.7 GeV event, which is observed 284 seconds after the GBM trigger. 

The Fermi-LAT point of contact for this burst is:
Alessandra Berretta (alessandra.berretta at 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.