[vsnet-grb-info 10670] GRB 110625A: Fermi LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12097
SUBJECT: GRB 110625A: Fermi LAT detection
DATE:    11/06/26 19:52:11 GMT
FROM:    Thomas P.H. Tam at Nat.Tsing Hua U.  <grbtom at gmail.com>

P.H.T. Tam and A.K.H. Kong (NTHU) report:

We report on the detection of >100 MeV gamma-ray emission from the direction
of GRB 110625A (Swift trigger
456073; Page et al., GCN #12088) using the Fermi Large Area Telescope
(LAT).

The GRB position was outside the LAT field of view (i.e., >75 deg with
respect to the LAT boresight) at the burst
onset (T0; 2011-06-25 UT 21:08:28; GCN #12088). However, prominent emission
up to several GeV was detected
from the GRB direction around T0+200s to T0+500s, during which the light
curve seems to resemble a double-peak
structure. Using the data obtained from the above period, we localized the
LAT emission at RA, DEC (J2000 deg) =
286.6, 6.9, with a statistical error of ~0.3 deg (68% CL), which is
compatible with the refined Swift/XRT position (Page
et al., GCN #12092). A preliminary spectral fit gives a photon spectral
index of around -3 at energies above 100
MeV.