[vsnet-grb-info 2412] GRB 051103 Milagro GeV/TeV Observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4249
SUBJECT: GRB 051103 Milagro GeV/TeV Observations
DATE:    05/11/11 06:45:36 GMT
FROM:    Pablo Saz Parkinson at UCSC/Milagro  <pablo at scipp.ucsc.edu>

Pablo Saz Parkinson (UC Santa Cruz) on behalf of the Milagro Collaboration
reports:

We have searched Milagro data for emission at GeV/TeV energies from the
IPN short hard burst GRB 051103 (GCN Circ 4197, S. Golenetskii et al.),
during the 0.17 s burst duration observed by the Konus-Wind experiment. No
evidence for prompt GeV/TeV emission was found. This burst occurred at a
relatively large zenith angle of 50 degrees, where the sensitivity of
Milagro is degraded. A preliminary analysis, assuming a differential
photon spectral index of -2.4, gives an upper limit on the fluence at 99%
confidence of:

Fluence < 4.2 * 10^(-6) erg cm^(-2) (0.25 - 25 TeV)

If the burst originated from a source in the nearby galaxy M81, at
a distance of less than 4 Mpc (GCN Circ 4197, S. Golenetskii et al.)
the attenuation due to the extra-galactic background light (EBL) would
be negligible. This upper limit is preliminary and will be refined with
further analysis.