[vsnet-grb-info 25555] IceCube-200425A: Upper limits from Fermi-GBM Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27655
SUBJECT: IceCube-200425A: Upper limits from Fermi-GBM Observations
DATE:    20/04/27 16:31:54 GMT
FROM:    Cori Fletcher at USRA  <cfletcher at usra.edu>

C. Fletcher (USRA) reports on behalf of the Fermi-GBM team:
For the IceCube high-energy neutrino candidate event IceCube-200425A
(GCN 27651), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 100.10 (+4.67/-3.14 deg  90% PSF containment) J2000
Dec: 53.57 (+2.45/-1.60 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 identified
a low reliability event 8.93 minutes before IceCube-200425A
(https://gcn.gsfc.nasa.gov/notices_gbm_sub/609549478.fermi). However
due to the temporal offset and low reliability, we do not consider these
two events associated.

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-200425A.

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:    7.3      14.      37.
1.024 s:    2.6      3.9      10.
8.192 s:    0.8      1.8      3.5

These results are preliminary.