IceCube-241127A

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

On 2024-11-27 at 14:11:14.42 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 1.28 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/140125_41215060.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2024-11-27
Time:  14:11:14.42 UT
RA: 164.09 (+0.46, -0.52 deg 90% PSF containment) J2000
Dec: 5.38 (+0.58, -0.55 deg 90% PSF containment) J2000

No Fermi 4FGL or 3FHL catalog sources are in the 90% uncertainty region. However, given the promising characteristics of the candidate neutrino event, we encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source associated with it. 

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

L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), C. Bartolini (INFN Bari), S. Garrappa (Weizmann Institute of Science) and J. Sinapius (DESY) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy IC241127A neutrino event (GCN 38349
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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 2024-11-27 14:11:14.42 UTC (T0) with J2000 position RA = 164.09 (+0.46, -0.52) deg, Decl. = 5.38 (+0.58, -0.55) deg 90% PSF containment.
No cataloged gamma-ray sources are found within the 90% IC241127A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546
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 ).

We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC241127A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <3.09e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <1.67e-08(<9.31e-08) 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 source will continue. For this source, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at stud-mail.uni-wuerzburg.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.

P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report on behalf of the Swift-XRT team,

Swift-XRT observed the field of IceCube-241127A (IceCube Collaboration, GCN 38349
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 ) between 18:51 and 22:12 UT on 2024 November 27 (16.8 to 29.4 ks after the trigger), gathering 4.7 ks over 10 pointings centred on the neutrino position.

One X-ray source is detected at a RA, Dec = 164.0502° 5.2615, which is equivalent to:

RA (J2000)  =  10h 56m 12.04s
Dec (J2000) = +05d 15’ 41.3S"

with an uncertainty of 8.4 arcseconds (radius, 90 confidence). This is consistent with the a known X-ray source from the Swift [LSXPS](https://www.swift.ac.uk/LSXPS/) catalogue: [LSXPS J105612.0+051546](https://www.swift.ac.uk/LSXPS/LSXPS%20J105612.0%2B051546); and the optical galaxy SDSS J105612.22+051544.6. The count-rate in the historical Swift data is 0.023 (+0.007, -0.006) ct/sec; in the new observations the count-rate is 0.015 (+0.006, -0.005); i.e. the source shows no signs of outburst.

Three other objects were found, all of which are rated “poor” by the detection algorithm which corresponds to a ~1 sigma detection, their details are below (all positions in J2000, errors are arcseconds, 90% confidence).

SWIFT J105542.0+051112 (source 2):

RA:  10h 55m 42.04s (= 163.9252)
Dec: +05d 11’ 12.1" (= +5.1867)
Error: 7.0
This source is 2.1 arcseconds from the radio source NVSS J105542+051112.


SWIFT J105615.1+051437 (source 3):

RA:   10h 56m 15.13s (= 164.0630)
Dec: +05d 14’ 37.7" (= +5.2438)
Error: 8.2


SWIFT J105711.6+054504 (source 4):

RA (J2000):  10h 57m 11.64s (= 164.2985)
Dec (J2000): +05d 45’ 04.8" (= +5.7513)
Error: 7.6
This source is 10.6 arseconds from the high proper-motion star PM J10571+0544A, and 13arcseconds
from the Rosat source: 1RXS J105710.9+054458.
The Rosat brightness is equivalent to 0.048 +/- 0.011 ct/sec in XRT (assuming a power-law spectrum, photon index 1.7, nH = 3e20 cm^-2); the XRT count-rate is 0.013 (+0.008, -0.006); this this possible source also shows no evidence for an outburst.

The full XRT analysis can be viewed online at https://www.swift.ac.uk/neutrino/NEUTRINO_FIELD00042/.

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-241127A (https://gcn.nasa.gov/circulars/38349
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 ) in a time range of 1000 seconds centered on the alert event time (2024-11-27 14:02:54.420 UTC to 2024-11-27 14:19:34.420 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-241127A. 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-241127A is 1.4e-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 3e+02 GeV and 1e+05 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2024-11-26 14:11:14.420 UTC to 2024-11-28 14:11:14.420 UTC). In this case, we report a p-value of 1.00, 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-241127A is 1.6e-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 (JSI), Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY), Anna Franckowiak (Ruhr University Bochum) and Jesper Sollerman (Stockholm University) 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-241127A (Zegarelli et. al, GCN 38349
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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). As a result of delays due to bad weather, we started observations in the g- and r-band beginning at 2024-11-29 10:38 UTC, approximately 44.4 hours after event time. We covered 95.5% (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 find one candidates lying within the 90.0% localization of the skymap.

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| ZTF Name     | IAU Name   | RA (deg)    | DEC (deg)   | Filter | Mag   | MagErr |
+---------------------------------------------------------------------------------+
| ZTF19aasljeo | AT2022aelp
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  | 163.5871140 | +05.9265829 | g      | 19.23 | 0.14   | 
+---------------------------------------------------------------------------------+

ZTF19aasljeo is a nuclear source that was first detected on 2019-04-27, and has a long history of variability in ZTF. The source has a crossmatched detection as WISEA J105420.91+055535.5 at a distance of 0.25", and based on the WISE colours of the galaxy (W1-W2 = 1.07), ZTF19aasljeo is very likely an AGN. 

Over the past two months the source has been detected in difference imaging with a magnitude of g ~ 19.3. In historical detections over the past two years, the source was detected at a fainter level of g ~ 20. In reference science images from PS1 (Chambers et al. 2016), the source was detected at a much fainter level of g = 21.3, demonstrating that the source has brightened substantially in recent years.

However, there are no indications of significant flaring on timescales of either weeks or months that coincide with the detection of IC241127A. We therefore find no strong evidence from our data to suggest that this AGN is associated with the neutrino. 

Observations of this field will continue as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023).

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 ).