Another intriguing multi-messenger coincidence:
A (very) high-energy neutrino candidate event was detected by the IceCube neutrino telescope at 2025-03-09 07:36:04. The preliminary data reconstruction gives an enormous energy of 4132 TeV (>4 peta electronvolt = 4x10^15 eV!). It has a 50% probability of being of astrophysical origin (signalness) and instead of a noise event induced for example by cosmic rays in the Earths atmosphere. This combination (very high energy but only relatively low signalness) makes this event a clear outlier in the usual distribution of these parameters. The preliminary, online reconstruction of the direction of the neutrino points to a region of about 1deg diameter in the Virgo constellation.
About two minutes later, on 2025-03-09 07:38:30, the gamma-ray burst monitor (GBM) onboard the Fermi satellite recorded a bright, long gamma-ray burst (GRB), named GRB 250309B. The reconstructed origins of both events are perfectly compatible with each other. This could thus point to a common origin.
More refined analyses of both events should become available soon. In parallel follow-up observations at other wavelengths will also help to confirm (and hopefully study) this phenomenon in more detail.
2 Likes
An improved reconstruction performed by IceCube on the neutrino data resulted in a reduced localisation uncertainty of around 0.3deg radius. The energy and other parameters of the event are confirmed. The neutrino event is now called IceCube-250309A.
We have added the event display of IceCube-250309A to Astro-COLIBRI. Source: IceCube@X
While the X-ray afterglow of the GRB has not been found (yet?), there is a candidate for the optical afterglow: AT 2025dws, detected by the Zwicky Transient Facility (ZTF). Rapid observations will help see if this event fades as expected for a GRB afterglow…
The optical transient AT 2025dws detected by ZTF, seems indeed to be the afterglow of GRB 250309B. It is rapidly fading (e.g. LCO GCN #39643) as expected.
Spectroscopic observations with OSIRIS+ at the GTC even allowed to determine its redshift to z=1.898 (GCN #39647).
The position of the optical afterglow is pretty far away from the neutrino event IceCube-250309A (distance 2.2deg) and thus far outside the localisation uncertainty of the neutrino (~0.3deg at 90% containment). Everything thus points to the neutrino and GRB being two unrelated events. They just happened around the same time and roughly in the same region of the sky by chance.
Further confirmation of the statements above comes from the Interplanetary Network (IPN). Using data from 4 satellites ( Fermi, Konus-Wind, Mars-Odyssey, and GECAM-B), allowed to triangulate the position of GRB 250309B to a small strip that includes the optical event AT 2025dws but that is incompatible with the localization of the neutrino IceCube-250309A. Details: GCN #39652
1 Like
