TITLE:   GCN CIRCULAR
NUMBER:  34851
SUBJECT: IceCube-231004A: Upper limits from Fermi-GBM Observations
DATE:    23/10/20 15:50:36 GMT
FROM:    Joshua Wood at NASA/MSFC <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC), Eric Burns (LSU), Michelle Hui (NASA/MSFC) report on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-231004A
(GCN 34797), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 143.79 (+1.10, -1.01 deg  90% PSF containment) J2000
Dec: -25.04 (+1.03, -1.21 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-231004A.

We set upper limits on impulsive gamma-ray emission to aid
theoretical modeling of the potential optical counterpart
AT2023uqf/ZTF23abidzvf (GCN 34837). Using the representative
soft, normal, and hard GRB-like templates described in
arXiv:2308.13666, 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:    2.9      4.2      7.3
1.024 s:    0.9      1.4      2.3
8.192 s:    0.3      0.4      0.6

Assuming the reported redshift z = 0.1503 (GCN 34837), we estimate
the following intrinsic luminosity upper limits over 
the 1 keV-10 MeV energy range (in units of 10^49 erg/s):

Timescale  Soft     Normal   Hard
------------------------------------
0.128s:    2.8      3.7      10.6
1.024s:    0.8      1.2      3.3
8.192s:    0.3      0.3      0.9

These results are preliminary.