TITLE: GCN CIRCULAR NUMBER: 39657 SUBJECT: IceCube-250309A: Upper limits from Fermi-GBM Observations DATE: 25/03/10 23:19:19 GMT FROM: Lorenzo Scotton at UAH lscottongcn@outlook.com
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.
View this GCN Circular online at https://gcn.nasa.gov/circulars/39657. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...