IceCube-241224A

K. Labzina,  K.Zhirkov, V.Lipunov, E.Gorbovskoy, A.Kuznetsov, G.Antipov, D.Vlasenko,
A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, V.Topolev, Ya.Kechin, V.Senik, Yu.Tselik (Lomonosov MSU),
O.Gress, N.Budnev, O.Ershova (ISU),
C.Francile,  F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
D.Buckley (SAAO),
A.Sosnovskij (Crao RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)

MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)
started IceCube-241224A (IC GCN #38664
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 , trigger No 303893, trigger time 07:10:04UT, 12h 20m 13.44s , +02d 46m 01.2s, R=0.74) errorbox
16 sec after notice time (178 sec after trigger time) at 2024-12-24 07:13:02 UT, with upper limit up to  19.6 mag (Lipunov et al.GCN#38663, MASTER cover map:
https://master.sai.msu.ru/site/master2/event.php?id=2720792 )

We observed it in MASTER-SAAO, MASTER-OAFA and analyzed MASTER archive images since 2016 of the sources, that can be related with this event.
There is  quasar PKS 1217+02  inside 3-sigma IC error-box
https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=_RAJ%2C_DEJ&-sort=_r&-to=&-out.max=20&-meta.ucd=2&-meta.foot=1&-c=185.0495+2.0617222222222&-c.rs=5)

We detected its brightening up to 15.7m near alert time.
MASTER archive light curve from 2016 year is available at
http://observ.pereplet.ru/IC/MASTER_IC241224A.jpg

We report the observation of an Zhirkov effect, discovered earlier
(The Astrophysic Jornal Letters, 896, L19, 2020 https://ui.adsabs.harvard.edu/abs/2020ApJ...896L..19L/abstract ).

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 IC241224A neutrino event (GCN 38664
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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 2024-12-24 07:10:04.35 UTC (T0) with J2000 position RA = 184.97 (+0.59, -0.52) deg, Decl. = 2.76 (+0.67, -0.67) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC241224A localization error (The Fourth Fermi-LAT catalog Data Release 4, 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 IC241224A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC241224A best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.45e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <9.80e-09(<5.72e-08) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.

In the analysis of the ~16-years integrated LAT data (100 MeV - 1 TeV), a 4.9 sigma excess of gamma rays, Fermi J1220.3+0200, was detected 0.73 deg offset from the best-fit IC241224A position, outside the 90% confidence localization of the direction of the neutrino. Assuming a power-law spectrum, the best-fit localization is (J2000) RA: 185.09 deg, Dec: 2.04 deg (9.40 arcmin 99% containment, 4.6 arcmin 68% containment). The gamma-ray best-fit spectral parameters are flux = (1.25 +/- 0.65)e-9 ph cm^-2 s^-1 and index = 2.08+/-0.19 (statistical uncertainty only). In a preliminary analysis of the LAT data over 1-day and 1-month prior T0, Fermi J1220.3+0200 is not significantly detected. The statistical significance is calculated following the prescription adopted in the Fourth Fermi-LAT catalog (The Fermi-LAT collaboration 2022, ApJS, 260, 53). 

The LAT catalogued object 2FGL J1219.7+0201 (The Fermi-LAT collaboration 2011, ApJ, 743, 171) is positionally consistent with Fermi J1220.3+0200 (2.7 arcmin separation). A possible counterpart is the blazar 5BZQJ1220+0203 (PKS 1217+02) at RA= 185.0495 deg, Dec= 2.0617 deg (Massaro et al. 2015 Ap&SS, 357, 1). The blazar is within the 68% positional uncertainty of Fermi J1220.3+0200, located 3 arcmin away from the gamma-ray best-fit position.

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.

Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY), Robert Stein (JSI), 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-241224A (Zegarelli et. al, GCN 38664
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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 2024-12-24 10:31 UTC, approximately 3.4 hours after event time. We covered 75.3% (1.1 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 candidate 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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| ZTF18aaxzhgj |  -------  | 185.0307759 | +02.4088207 | g      | 18.31 | 0.06   | 
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ZTF18aaxzhgj was first detected on 2018-06-05. The optical detection is located 0.17 arcsec from the nucleus of known AGN 2MASX J12200736+0224320. This AGN has a spectroscopic redshift of z=0.159 from SDSS, and a QSO broadline classification.

The source has been slowly brightening over the past five years, reaching a difference imaging magnitude of g ~ 18. In reference science images from PS1 (Chambers et al. 2016), the source was detected at a slightly fainter level of g = 19, demonstrating that the source has brightened in recent years.

However, there are no indications of significant flaring on timescales of either weeks or months that coincide with the detection of IC241224A. We therefore find no strong evidence from our data to suggest that this AGN is associated with the neutrino. 

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Oskar Klein Center at Stockholm University, the University of Maryland, University of California, Berkeley , the University of Wisconsin at Milwaukee, University of Warwick, Ruhr University Bochum, Cornell University, Northwestern University and Drexel University. Operations are conducted by COO, IPAC, and UW. 

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 ).

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-241224A (https://gcn.nasa.gov/circulars/38664
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 ) in a time range of 1000 seconds centered on the alert event time (2024-12-24 07:01:44.350 UTC to 2024-12-24 07:18:24.350 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-241224A. 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-241224A 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 2e+05 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2024-12-23 07:10:04.350 UTC to 2024-12-25 07:10:04.350 UTC). In this case, we report a p-value of 0.22, 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-241224A 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)

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

On 2024-12-24 07:10:04.35 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. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 3.816 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/140284_303893.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2024-12-24
Time: 07:10:04.35 UT
RA: 184.97 (+0.59, -0.52 deg 90% PSF containment) J2000
Dec: 2.76 (+0.67, -0.67 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.

No Fermi 4FGL or 3FHL catalog source are in the 90% uncertainty region.
The nearest gamma-ray source in either catalog is 4FGL J1225.0+0330 at RA: 186.25 deg, Dec: 3.51 deg 1.46 deg away from the best-fit event 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