[vsnet-grb-info 26369] IceCube-200921A: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28469
SUBJECT: IceCube-200921A: Upper limits from Fermi-GBM Observations
DATE:    20/09/22 02:48:51 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007 at uah.edu>

R. Hamburg (UAH) reports on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-200921A
(GCN 28468), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 195.29 (+2.35  -1.73 deg 90% PSF containment) J2000
Dec: 26.24 (+1.51  -1.77 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-200921A.

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^-6 erg/s/cm^2):

Timescale   Soft     Normal   Hard
--------------------------------------
0.128 s:    17.      34.      73.
1.024 s:    6.4      13.      21.
8.192 s:    2.2      2.5      1.4

These results are preliminary.