GCN Circular 39657
Subject
IceCube-250309A: Upper limits from Fermi-GBM Observations
Event
Date
2025-03-10T23:19:19Z (a year ago)
From
Lorenzo Scotton at UAH <lscottongcn@outlook.com>
Via
Web form
L. Scotton (UAH) reports on behalf of the Fermi-GBM Team:
For the IceCube high-energy neutrino candidate event IceCube-250309A
(GCN 39631), at the event time Fermi-GBM was observing the reported
neutrino location at:
RA: 211.07 (+0.31 -0.30 deg 90% PSF containment) J2000
Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000
Fermi-GBM detected GRB 250309B (GCNs 39635, 39642) around
146s after the time of the neutrino candidate. However,
the ZTF and GROWTH collaborations reported the detection
of a potential optical counterpart ZTF25aaitvjt | AT2025dws
(R. Stein et al, GCN 39639), suggesting that GRB 250309B
and IceCube-250309A are unrelated. The IPN triangulation
(Kozyrev A. S. et al, GCN 39652) also suggests that
GRB 250309B and IceCube-250309A are unrelated.
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-250309A.
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: 1.0 1.8 3.7
1.024 s: 0.35 0.56 1.3
8.192 s: 0.11 0.11 0.24
These results are preliminary.