[vsnet-grb-info 23708] IceCube-190922A: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25807
SUBJECT: IceCube-190922A: Upper limits from Fermi-GBM Observations
DATE:    19/09/23 05:27:26 GMT
FROM:    Eric Burns at GSFC  <erickayserburns at gmail.com>

E. Burns (NASA/GSFC) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event 190922A (GCN 25802),
at the event time Fermi-GBM was observing about half the reported neutrino
probability map of:

RA: 167.43 (+ 3.40 - 2.63  deg  90% PSF containment) J2000
Dec: -22.39 (+ 2.88 - 2.89 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-190922A. Over the 1 minute search interval the
Earth-occulted region for Fermi shifted by about 4 degrees, resulting in
time-varying exposure to the neutrino localization.

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

Timescale  soft     norm     hard
--------------------------------------
0.128 s:   3.8      6.3      13.
1.024 s:   1.0      1.8      3.7
8.192 s:   0.3      3.9      1.0