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GCN Circular 20127

Subject
Fermi GBM Observations of IceCube-161103
Date
2016-11-04T20:44:06Z (8 years ago)
From
Eric Burns at U of Alabama <eb0016@uah.edu>
E. Burns (UAH), A. Goldstein (USRA), P. Jenke (UAH),
M. S. Briggs (UAH), and L. Blackburn (CfA) report on behalf
of the Fermi GBM team:

We have searched the Fermi Gamma-ray Burst Monitor data for a
gamma-ray counterpart to the IceCube neutrino 161103
(Taboada 2016, GCN 20119).

The location of the neutrino was observed by GBM with good
geometry. The closest on-board trigger was more than 10 hours
before the neutrino time and was terrestrial in origin.

Measurements using the Earth Occultation technique (Wilson-Hodge
et al. 2012, ApJS, 201, 33) around this position place a three sigma one
day flux upper limit of about 190 mCrab between 12 and 100 keV between
October 31st and November 3rd.

A seeded search for impulsive emission with duration between 0.128 s and
8.192 s around the time and sky location of the detected neutrino yielded
no significant candidates above the GBM background. The search method was
developed to look for electromagnetic counterparts in the GBM data of
sub-threshold gravitational wave signals found in the LIGO data
(Blackburn et al. 2015, ApJS, 217, 8), with improvements to be described
in a forthcoming article. Here the search was run from 30 s before to 30 s
after the reported neutrino detection time and seeded with its location.

A blind search for untriggered impulsive emission in the GBM data
centered on the neutrino detection looking for events between 0.1 s and
32 s durations yielded no candidates consistent with the position of the
neutrino. This search technique was developed for the detection of
untriggered short GRBs in the GBM data (Briggs et al., in prep.).

There are some longer term, low energy fluctuations that localize away
from the neutrino direction. With no impulsive emission found we set
model-dependent 1 second peak flux 3 sigma upper limits on prompt
emission. Using a cutoff power law model with index -0.42 and Epeak of
566 keV, representative of a typical short GRB observed by GBM, the limit
in the 10-1000 keV range is 9.1x10^-5 erg/cm^2. For a Band function with
Epeak, alpha, beta = 300, -1.0, -2.5, similar to long GRBs, gives an upper
limit of 4.6x10^-5 erg/cm^2 in 10-1000 keV. These limits are higher than
usual as a result of highly variable backgrounds around event time.
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