TITLE:   GCN CIRCULAR
NUMBER:  15196
SUBJECT: GRB 120916A: Fermi-LAT detection of a burst
DATE:    13/09/08 18:45:43 GMT
FROM:    Giacomo Vianello at SLAC  <giacomov@slac.stanford.edu>

G. Vianello (Stanford), D. Kocevski(NASA/Goddard), J. Racusin
(NASA/Goddard), and V. Connaughton (UAH) report on behalf of the
Fermi-LAT team:

On Sept. 8th, 2013, Fermi LAT detected high energy emission from GRB
130907A, which triggered Swift at T0 = 21:41:13 UT (GCN 15183).

Fermi was passing through the South Atlantic Anomaly around T0,
therefore data taking was disabled and neither Fermi/GBM nor Fermi/LAT
could trigger on the burst. Fermi exited the SAA and resumed data
taking at ~T0+1300 s.

The burst was ~150 deg from the LAT boresight when Fermi resumed data
taking, and entered the LAT FOV at ~T0+3400 s. A likelihood analysis
in the time interval T0+3400 s - T0+20 ks (with a ~8000 s exposure)
resulted in a detection of the source with a significance of ~6 sigma
at the NOT position (GCN Circ. 15187).

In particular, a 55 GeV photon compatible with the position of the
burst was observed at ~T0+18 ks.

The Fermi LAT point of contact for this burst is Daniel Kocevski
(daniel.kocevski@nasa.gov).

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.