TITLE:   GCN CIRCULAR
NUMBER:  28735
SUBJECT: IceCube-201021A: Upper limits from Fermi-GBM Observations
DATE:    20/10/21 22:07:13 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH) reports on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-201021A
(GCN 28715), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 260.82 (+1.73 -1.68 deg 90% PSF containment) J2000
Dec: 14.55 (+1.35 -0.74 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-201021A.

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:    5.2      8.1      16.0
1.024 s:    2.5      3.5      5.9
8.192 s:    0.6      0.8      1.7

These results are preliminary.