[vsnet-grb-info 11410] GBM trigger 347620337 (GRB 120107A?) : High-energy photon emission in Fermi/LAT data

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12822
SUBJECT: GBM trigger 347620337 (GRB 120107A?) : High-energy photon emission in Fermi/LAT data
DATE:    12/01/09 22:43:53 GMT
FROM:    Weikang Zheng at U.of Michigan  <zwk at umich.edu>

Weikang Zheng and Carl Akerlof, report on behalf of the ROTSE
collaboration:

High-energy photon emission in Fermi/LAT data was found to be correlated
with GBM trigger 347620337 (probably GRB 120107A). Our LAT data
processing pipeline which uses the matched filter technique (Akerlof et
al, 2010, ApJ, 725, L15; 2011 ApJ, 726, 22; Zheng et al. 2012, ApJ
745,72), detected the high-energy photon emission from 09:12:15 UT on
Jan. 7, 2012 (MET = 347620337) as a follow-up of a routine search in GBM
trigger catalogs. The GBM trigger location (Ra = 223.1, Dec = -77.96)
was about 56 degree from the LAT boresight, and the zenith angle was
about 106 degrees. ~7 photons above 100 MeV were detected within 50 s
after the burst, with the highest energy of ~1.78 GeV at 1.18s after the
burst (note that class 1 photons are not included in the pipeline
analysis since it is not automatically available from LAT data server at
the moment). The new GRB location estimated by the matched filter
technique is Ra = 246.40, Dec = -69.93 with uncertainty ~0.5 degree,
this is ~10 degrees away from the GBM trigger location.

A likelihood analysis gives a TS value of 58.9 (duration of 50 s), and
the GRB location Ra = 246.31, Dec = -69.93, which is also consistent
with the location derived from the matched filter technique.

All the pipeline results can be found in the following link, including
the skymap and light curve figures:
http://www.rotse.net/LAT/GBMTriggers/347620337/347620337_res.html