High-energy neutrino IceCube-260315A detected, followed by X-ray and optical counterparts.

AI Summary

IceCube detected a high-energy neutrino event, leading to the identification of an X-ray source and an optical transient, suggesting a potential astrophysical origin involving a QSO at redshift z=1.389.

Notices (1)

IceCube — NEUTRINO · Sun, 15 Mar 2026 02:19:06 GMT

GCN Circulars (8)

GCN-44048 — IceCube-260315A · Wed, 18 Mar 2026 18:09:53 GMT
The Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations reported no detection of optical counterparts to the neutrino event IceCube-260315A using the Palomar 48-inch telescope and ZTF camera. They covered 93.7% of the reported localization region and applied machine learning algorithms to reject false positives. The previously reported candidate counterpart AT 2026fpm was also not detected due to its location outside the 90% containment area and its likelihood of being a known variable.

GCN-44042 — IceCube-260315A · Wed, 18 Mar 2026 04:57:04 GMT
The Einstein Probe's Follow-up X-ray Telescope (FXT) detected an X-ray source consistent with the optical transient AT2026fpm at RA: 176.1586 deg, DEC: -2.6035 deg, and a flux of 1.1×10^(-13) erg/s/cm^2 in the 0.5-10 keV band. The X-ray position aligns with the QSO at redshift z=1.389.

GCN-44036 — IceCube-260315A · Tue, 17 Mar 2026 12:07:57 GMT
A team of researchers led by L. Pfeiffer from the University of Würzburg reported the results of an analysis of Fermi-LAT gamma-ray observations of the IceCube-260315A neutrino event. No significant gamma-ray emission was detected within the error region of the neutrino event, setting upper limits on the flux for timescales from years to days. The team will continue monitoring the source with Fermi-LAT.

GCN-44033 — IceCube-260315A · Mon, 16 Mar 2026 17:57:13 GMT
The IceCube Neutrino Observatory reported conducting a search for additional neutrino events from the direction of IceCube-260315A, following an initial alert. No additional events were detected within the 90% containment region in either a 1000 second or 2 day time window. The sensitivity to neutrino point sources with an E^-2.5 spectrum was measured at 0.15 GeV cm^-2 in 1000 seconds and 0.16 GeV cm^-2 in 2 days.

GCN-44026 — IceCube-260315A · Mon, 16 Mar 2026 13:05:38 GMT
A team of international researchers led by Francis Fortin (IRAP) observed the optical counterpart of IceCube 260315A using the DDRAGO imager on the COLIBRÍ telescope. They detected a candidate optical counterpart, AT 2026fpm, with preliminary magnitudes of g = 19.94, r = 19.69, and z = 19.66. The team also noted that the source was previously identified as a variable and found in PS1 at a much fainter level.

GCN-44023 — AT2026fp · Sun, 15 Mar 2026 18:39:46 GMT
The MASTER-OAFA robotic telescope in Argentina discovered a new optical transient, J114437.99-023613.5/AT2026fpm, located near the errorbox of an IceCube neutrino alert. The transient has a magnitude of 19.2 in the 'CLEAR' filter and was not detected in a reference image from February 2026. Spectral observations are required for further analysis.

GCN-44017 — IceCube-260315A · Sun, 15 Mar 2026 11:21:27 GMT
The IceCube Neutrino Observatory at the South Pole detected a high-energy neutrino candidate event on March 26, 2015. The event, IceCube-260315A, was initially identified with a moderate probability of astrophysical origin and a false alarm rate of 3.3512 events per year. Subsequent analysis refined the direction to RA: 175.69, Dec: -1.9, with a 30% astrophysical neutrino purity. No known gamma-ray sources were found within the 90% uncertainty region. IceCube Gold/Bronze track alerts are now available via Kafka for further analysis.

GCN-44011 — IceCube Alert 260315A · Sun, 15 Mar 2026 02:40:16 GMT
An astronomical alert was issued for IceCube Alert 260315A based on data from the MASTER-OAFA robotic telescope in Argentina. The observations began 105 seconds after the alert was issued and 224 seconds after the trigger time. The upper limit for the detection was set at 20.4 mag. The observation and reduction are continuing.