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GCN Circular 30649

Subject
IceCube-210811A: Upper limits from Fermi-GBM Observations
Date
2021-08-16T21:06:34Z (3 years ago)
From
Cori Fletcher at USRA <cfletcher@usra.edu>
C. Fletcher (USRA) reports on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-210811A
(GCN 30627), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 270.79 (+1.07, -1.08 deg  90% PSF containment) J2000
Dec: 25.28 (+0.79, -0.84 deg 90% PSF containment) J2000

There was no Fermi-GBM onboard trigger around the event time of the
neutrino candidate. An automated, blind search for short gamma-ray bursts
below the onboard triggering threshold in Fermi-GBM also identified no
counterpart candidates.

The GBM targeted search, the most sensitive, coherent search for GRB-like
signals, was run from +/-30 s around the neutrino candidate time.
From this search, no significant signal was found related
to IceCube-210811A.

We set upper limits on impulsive gamma-ray emission. Using the
representative soft, normal, and hard GRB-like templates described in
arXiv:1612.02395, we set the following 3 sigma flux upper limits over
10-1000 keV (in units of 10^-7 erg/s/cm^2):

Timescale   Soft     Normal   Hard
-------------------------------------------
0.128 s:     8.7      11.      19.
1.024 s:     2.1      2.7      4.3
8.192 s:     1.1      1.4      1.5

These results are preliminary.
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