IceCube-260805A
GCN Circular 45337
Subject
IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
Date
2026-08-09T23:42:20Z (21 days ago)
From
syan079@icecube.wisc.edu
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-260805A (https://gcn.nasa.gov/circulars/45294)in a time range of 1000 seconds centered on the alert event time (2026-08-05 13:53:19.709 UTC to 2026-08-05 14:09:59.709 UTC) during which IceCube was collecting good quality data. Excluding the event
that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-260805A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260805A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination
with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 7e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2026-08-04 14:01:39.709 UTC to 2026-08-06 14:01:39.709 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.7e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260805A in a 2 day
time window.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 45310
Subject
IceCube-260805A: One candidate from the Zwicky Transient Facility
Date
2026-08-07T16:29:17Z (24 days ago)
From
akshay.eranhalodi@desy.de
Via
Web form
Akshay Eranhalodi (DESY), Robert Stein (JSI), Cristobal Zilleruelo Cañas (DESY), Jannis Necker (Leiden University), and Anna Franckowiak (Ruhr University Bochum) report,
On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:
As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260805A (IceCube Collaboration, GCN 45294) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-08-06 10:23 UTC, approximately 20.4 hours after event time. We covered 65.4% (1.0 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag.
The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with one transient candidate by our pipeline, lying within the 90.0% localization of the skymap.
+--------------------------------------------------------------------------------+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr |
+--------------------------------------------------------------------------------+
| ZTF26aaskzvj | AT 2026jrc | +60.57411872 | +25.81342036 | g | 20.937 | 0.182 |
+--------------------------------------------------------------------------------+
ZTF26aaskzvj/AT 2026jrc was first detected on 2026-04-15, and is a SN-like transient associated with a nearby galaxy in NED at z=0.0192 (~85 Mpc). The transient is only marginally detected with forced photometry at the neutrino arrival time. The source appears to have peaked 100 days ago at M<-18 in r-band, and is now much fainter at M=-15.4 as of last week.
We encourage spectroscopic follow-up to determine its nature and asses potential high-energy neutrino emission scenarios.
ZTF and GROWTH are worldwide collaborations comprising Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany.
GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).
Alert database searches are done by AMPEL (Nordin et al. 2019).
Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ).
GCN Circular 45294
Subject
IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2026-08-06T00:02:49Z (25 days ago)
From
mvelazquez@icecube.wisc.edu
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 26-08-05 at 14:01:39.70 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. Documentation regarding the alert streams and their astrophysical purity can be found here: https://gcn.nasa.gov/missions/icecube.
This alert has an estimated false alarm rate of 1.449 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.
After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/142956_64385264.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 26-08-05
Time: 14:01:39.70 UT
RA: 60.47 (+0.91/-0.8 deg 90% PSF containment) J2000
Dec: 26.07 (+0.54/-0.56 deg 90% PSF containment) J2000
As announced in GCN Circular 43419 (https://gcn.nasa.gov/circulars/43419), IceCube alert notices for high-energy track alerts are now also streamed via Kafka.
IceCube Gold/Bronze track alerts are available on the Kafka topic 'gcn.notices.icecube.gold_bronze_track_alerts'.
The probability distribution of the true neutrino direction, allowing the extraction of precise 90% containment regions around the best-fit direction, is now available for revised reconstruction of high-energy track alerts.
The corresponding sky map is distributed as a FITS file and follows the explicit naming convention IceCube-YYMMDDX, where YYMMDD indicates the date of the event and X is a letter distinguishing multiple alerts on the same day. The download link is provided through the GCN schema distributed via Kafka.
Detailed documentation describing the alert distribution, schemas, and probability maps is available at: https://gcn.nasa.gov/missions/icecube.
One gamma-ray source from the Fermi FL16Y catalog is located within the 90% uncertainty region of this event: FL16Y J0402.5+2615, at RA = 60.647° and Dec = 26.267° (J2000), with an angular separation of 0.254° from the best-fit event position.
We report here sources within the 90% confidence contour available in the multi-order probability map, rather than those selected using the simplified rectangular error-box reported in this Circular.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica.
The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu