IceCube-231103A

The IceCube Collaboration (http://icecube.wisc.edu/) reports:

On 23-11-03 at 09:17:35.29 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.1472 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/138515_8773328.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 23-11-03
Time: 09:17:35.29 UT
RA: 105.67 (+3.15 / -2.94 deg 90% PSF containment) J2000
Dec: +47.85 (+ 1.95 / -1.78 deg 90% PSF containment) J2000

We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

Several Fermi 4FGL-DR4 sources are located in the 90% uncertainty region of the event. The closest source is  4FGL J0708.9+4839  at RA = 107.25 deg, Dec = +48.66  located 1.32 deg away from the best fit position.

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

C. Bartolini (INFN Bari), S. Buson (Uni Wuerzburg), S. Garrappa (Weizmann Institute of Science), and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the IC231103A  high-energy neutrino event (GCN 34933
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 ) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2023-11-03 at 09:17:35.29 UT (T0) with J2000 position RA =  105.67 (+3.15, -2.94) deg, Decl. = +47.85 (+1.95, -1.78) deg (90% PSF containment).  According to the fourth Fermi LAT source catalog (4FGL-DR4), there are several 4FGL-DR4 cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources in the 90% IC231103A uncertainty localization region. Based on a preliminary analysis of the LAT data over a month and day timescale prior T0, these objects are not significantly detected at gamma rays.

We searched for intermediate (days to years) timescale emission from a new gamma-ray source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC231103A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC231103A best-fit position, the >100 MeV flux upper limit (95% confidence) is <4.3e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2023-11-03 UTC), and < 1.3e-8 (<7.2 e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.

Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at weizmann.ac.il), C. Bartolini (chiara.bartolini at ba.infn.it), S. Buson (sara.buson at uni-wuerzburg.de) and J. Sinapius (jonas.sinapius at desy.de).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

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-231103A (https://gcn.nasa.gov/circulars/34933
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 ) in a time range of 1000 seconds centered on the alert event time (2023-11-03 09:09:15.290 UTC to 2023-11-03 09:25:55.290 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-231103A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-231103A is 1.5e-01 GeV cm^-2 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 5e+04 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2023-11-02 09:17:35.290 UTC to 2023-11-04 09:17:35.290 UTC). In this case, we report a p-value of 0.07, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-231103A is 1.8e-01 GeV cm^-2 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)

Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Anna Franckowiak (DESY/Ruhr University Bochum), Jannis Necker (DESY),  Simeon Reusch (DESY), Jesper Sollerman (OKC), Theophile du Laz (Caltech) 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-231103A (Blaufuss et. al, GCN 34933
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 ) 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 2023-11-03 09:24 UTC, approximately 0.1 hours after event time. We covered 84.1% (12.9 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). After removing low-level AGN variability, we are left with one following high-significance transient candidate by our pipeline, lying within the 90.0% localization of the skymap: 

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| ZTF Name     | IAU Name  | RA (deg)    | DEC (deg)   | Filter | Mag   | MagErr |
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| ZTF23abnoapt | AT2023wue
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  | 102.9192032 | +48.0780348 | g      | 17.98 | 0.05   | 
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ZTF23abnoapt was first detected on 2023-10-27, with a fast rise, slow decay and blue colour resembling a CV. We obtained a follow-up spectrum with the SEDm (Blagorodnova et al. 2018), which confirmed a blue continuum as expected for a CV, and a SNID best-fit to a galactic source. We therefore consider it likely that ZTF23abnoapt is unrelated to the neutrino.  

We note that one additional variable source in the localisation, ZTF19aaenfez, appears to be undergoing an extended optical flare. The source is WISE-detected (WISEA J065203.55+473924.6), and is a probable AGN based on WISE colours (W1-W2=0.95). The source is approximately 50% brighter in flux than the median across the 5-year baseline of ZTF. The flare has been ongoing for over one year in ZTF data. 

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France.

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 ).