[vsnet-grb-info 9687] GRB100826A: Fermi-LAT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11155
SUBJECT: GRB100826A: Fermi-LAT Observations
DATE:    10/08/30 20:52:22 GMT
FROM:    Julie McEnery at NASA/GSFC  <julie.e.mcenery at nasa.gov>

Julie McEnery (NASA/GSFC) and Nicola Omodei (Stanford) report
on behalf of the Fermi-LAT collaboration.

The Fermi Large Area Telescope (LAT) detected emission from
GRB 100826A also detected by GBM (trigger 304556304) at
22:58:22.89 on August 26, 2010.

The GBM location was at a very large angle of (~70 degrees) to
the LAT  boresight, and no significant excess is seen using
standard analysis procedures.

Using a non-standard data selection, over 350 counts above
background were detected within a 50 s interval coinciding with
the first GBM broad peak. The LAT light curve has a very similar
structure to this GBM peak, with the maximum count rate occurring
at ~22 s post-trigger. A preliminary study of the instrument
performance  at such a large inclination suggests that these events
are likely to be low energy gamma-rays, with energies less than 200
MeV. This data selection has insufficient spatial resolution to provide
a reliable LAT localization.

Further analysis is ongoing.

The Fermi LAT point of contact for this burst is Julie McEnery
(julie.mcenery at nasa.gov).