GCN Circular 30871

Subject

IceCube-210922A: Upper limits from Fermi-GBM Observations

Event

Date

2021-09-23T15:47:11Z (5 years ago)

From

Christian Malacaria at NASA-MSFC/USRA <cmalacaria@usra.edu>

C. Malacaria (USRA) reports on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-210811A
(GCN 30862Loading...
 
 ), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 60.73 (+0.96, -0.66 deg  90% PSF containment) J2000
Dec: -4.18 (+0.42, -0.55 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-210922A.

We set upper limits on impulsive gamma-ray emission. Using the
representative soft, normal, and hard GRB-like templates described in
arXiv:1612.02395Loading...
 
 , we set 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:       6.4      11.        14.
1.024 s:       2.1      3.4        4.6
8.192 s:       0.6      0.9        1.4

These results are preliminary.