[vsnet-grb-info 27283] GRB 210202A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29386
SUBJECT: GRB 210202A: Fermi-LAT detection
DATE:    21/02/03 05:58:46 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007 at uah.edu>

R. Hamburg (UAH), M. Axelsson (KTH & Stockholm Univ.), M. Arimoto (Kanazawa
Univ.), and R. Pillera (Politecnico and INFN Bari) report on behalf of the
Fermi-LAT team:

On February 2, 2021, Fermi-LAT detected high-energy emission from GRB
210202A, which was also detected by Fermi-GBM (trigger 633989436 /
210202841, GCN 29380).

The best LAT on-ground location is found to be

RA, Dec = 230.0, -38.0 (J2000)

with an error radius of 0.7 deg (90 % containment, statistical error only).

This was 45 deg from the LAT boresight at the time of the GBM trigger:

T0 = 20:10:31.3 UT.

The data from the Fermi-LAT show a significant increase in the event rate
after the GBM trigger that is spatially and temporally correlated with the
GBM emission (3 degrees from the GBM location) with high significance.

The photon flux above 100 MeV in the time interval 0-100s after the GBM
trigger is (2.3 +/- 0.9)e-05 ph/cm2/s, while the flux above 1 GeV is (2.7
+/- 1.6)e-06 ph/cm2/s.

The estimated photon index above 100 MeV is -1.9 +/- 0.3.

The highest-energy photon is a 1.4 GeV event which is observed 19 seconds
after the GBM trigger.

A Swift ToO has been requested for this burst.

The Fermi-LAT point of contact for this burst is Rachel Hamburg (
rkh0007 at uah.edu).

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.