IceCube-260704A
GCN Circular 45099
Subject
IceCube-260704A: No candidates from the Zwicky Transient Facility
Date
2026-07-07T10:32:00Z (3 days ago)
From
Robert David Stein at JSI <rdstein@umd.edu>
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-260704A (Zegarelli et. al, GCN 45075) 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 2026-07-04 07:25 UTC, approximately 0.1 hours after event time. We covered 98.4% (0.8 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 the following high-significance 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 |
+--------------------------------------------------------------------------------+
| ZTF19ablafcb | ------- | 320.5248614 | +34.5149697 | g | 21.09 | 0.20 |
+--------------------------------------------------------------------------------+
ZTF19ablafcb was first detected by ZTF on 2019-07-31. It is located at a galactic latitude of -10.94 degrees. Based on its WISE colours (W1-W2=0.6), historical optical variability in ZTF data, and nuclear location, it is likely that the source is an AGN. The source is clearly visible in archival PS1 imaging, and the source does not appear to be significantly flaring relative to this baseline. We therefore find no temporal evidence to suggest that the AGN is associated to the high-energy neutrino.
We do not select the AGN WISEA J212302.62+340634.2, which was observed by Adami et al. (GCN 45085). This is expected, given that the source was reported to not be flaring. Our ZTF ToO program only targets AGN which are undergoing flares coincident with the detection of neutrinos.
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 45092
Subject
IceCube-260704A: Upper limits from a search for additional neutrino events in IceCube
Date
2026-07-06T20:24:10Z (3 days ago)
From
Sam Hori at IceCube/U Wisc-Madison <sahori@wisc.edu>
Via
email
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-260704A (https://gcn.nasa.gov/circulars/45075) in a time range of 1000 seconds centered on the alert event time (2026-07-04 07:08:38.191 UTC to 2026-07-04 07:25:18.191 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-260704A. 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-260704A 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 6e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2026-07-03 07:16:58.191 UTC to 2026-07-05 07:16:58.191 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 1.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260704A 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 45085
Subject
IceCube260704A: OHP/T193 optical observations
Date
2026-07-06T10:52:28Z (4 days ago)
From
Christophe Adami at LAM <christophe.adami@lam.fr>
Via
Web form
C. Adami (LAM/Pytheas/AMU), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), F. Schussler (CEA Paris-Saclay) report on behalf of a larger collaboration:
We observed the WISEA J212302.62+340634.2 source (no available public spectroscopy in NED), at ~4.9arcmin from the mean coordinates of the IceCube
event IceCube260704A (Zegarelli et al., GCN 45075), using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL
spectro-imager.
We obtained 6 min of exposure in the r-band starting at 2026-07-05T02:04 UT (18.8h after the Zegarelli et al. trigger).
In the preliminar stacked images, we do not detect significant magnitude change as compared to the PanStarrs r-band magnitude of r=18.05.
We also observed in spectroscopic mode:
- We obtained a total of 60 min of exposures (2 x 30min) with the MISTRAL spectroscopic blue setting from 4000 to 7800 AA, starting at 2026-07-05 00:18 UT (17h after the trigger). With a preliminar data reduction, we very clearly detect Halpha (apparently with
a single peak) at a redshift of 0.1402. We also detect very clearly an intense double-peaked [NII]@6584A emission line. No other emission
line are visible. We detect however Magnesium@5175A, CaFe@5269A and NaD@5892A in absorption.
The log(Halpha/[NII]) is close to -0.1, likely placing this galaxy in the AGN/LINER region in a BPT diagram.
The two peaks of the [NII] emission line are separated by ~300km/s.
- We then obtained a second serie of 3 x 30min starting at 2026-07-05 23:13 UT (~40h after the trigger). With a preliminar data reduction, we still clearly detect Halpha with
a single peak at the same redshift and with a similar intensity. The [NII]@6584A emission line may show a mild evolution: the flux is stronger and the two peaks are much less separated and proeminent.
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean Pierre Troncin.
GCN Circular 45075
Subject
IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2026-07-04T09:34:08Z (6 days ago)
From
A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu>
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 26-07-04 at 07:16:58.19 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 0.8177 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/142791_45913213.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 26-07-04
Time: 07:16:58.19 UT
RA: 320.67 (+0.57/-0.55 deg 90% PSF containment) J2000
Dec: 34.14 (+0.45/-0.47 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.
No known gamma-ray sources listed in the Fermi LAT 16-year Source List (FL16Y) are located within the 90% uncertainty region of this event.
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