[vsnet-grb-info 12945] GRB 130310A: Fermi-LAT detection and localization

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14282
SUBJECT: GRB 130310A: Fermi-LAT detection and localization
DATE:    13/03/11 07:36:13 GMT
FROM:    Sylvain Guiriec at UAH  <sylvain.guiriec at lpta.in2p3.fr>

S. Guiriec (NASA/GSFC/NPP), G. Vianello (Stanford)
and M. Ohno (Hiroshima U.)
report on behalf of the Fermi-LAT team:

The Fermi Large Area Telescope (LAT) detected emission from
GRB 130310A (GBM trigger 130310840/384638984) at approximately
20:09:44 UT on March 10th, 2013, about 3s after Fermi-GBM trigger time.

The burst location was outside the LAT nominal field of view, at an angle
of ~79 degrees from the LAT boresight, and ~50 degrees from the Zenith.

Using the non-standard LAT Low Energy (LLE) data selection, featuring
a large effective area and a larger field of view below 100 MeV but a much
larger PSF with respect to the standard classes, we clearly detect
the prompt emission of the GRB (significance > 10 sigma above the
background). With this selection and in this energy range the GRB shows
a single FRED-like pulse, peaking ~3 s after the GBM trigger in good
coincidence with the peak of the GBM emission.

The high peak flux of the burst triggered an Autonomous Repointing
Request (ARR) starting about 50s after the trigger time, which placed
the GRB within the LAT nominal field of view for standard data
classes (~65 deg) approximately 200 s after the trigger.
Using the P7SOURCE_V6 class we detect ~18 photons between 100 MeV
and 3 GeV in the time interval 200 s - 800 s from the trigger, clearly clustered
in a point source ~4.8 deg away from the best GBM position and with
a significance larger than 5 sigma. Our best localization is:

R.A., Dec = 142.34, -17.23 (J2000)
90 % containment radius (statistical only) = 0.45 deg.

A GBM circular on GRB 130310A is forthcoming.

The Fermi LAT point of contact for this burst is Sylvain Guiriec
(sylvain.guiriec at nasa.gov)