IceCube-250309A

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 (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 AstrophysicsObservatory)


MASTER-OAFA robotic telescope  (Global MASTER-Net: Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) 
located in Argentina (OAFA observatory of San Juan National University)
started IceCube-250309A (IC GCN#39631
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 ) alert error-box (trigger No 1288692,14h 03m 12.24s , -10d 26m 24.0s, R=0.51)
9 sec after notice time (109 sec after trigger time) at 2025-03-09 07:37:54 UT, with upper limit up to  21.3 mag. (Lipunov et al.GCN#39630)

MASTER cover map:
https://master.sai.msu.ru/site/master2/observ.php?id=2805613

We analyzed MASTER archive images since 2013 of possible sources, that can be related with this event.
There is blazar J140105.33-091631.6 inside 3 sigma 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=210.27220833333+-9.2754444444444&-c.rs=5
We detected its decay and  brightening up to usual state after 10 hours of IC event trigger time.

MASTER archive light curve from 2013 year is available at
   http://observ.pereplet.ru/IC/MASTER_IC250309A.jpg

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

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-250309A (https://gcn.nasa.gov/circulars/39631
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 ) in a time range of 1000 seconds centered on the alert event time (2025-03-09 07:27:44.750 UTC to 2025-03-09 07:44:24.750 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-250309A. 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-250309A ranges from 1.7e+00 to 1.8e+00 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 1e+03 GeV and 9e+05 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2025-03-08 07:36:04.750 UTC to 2025-03-10 07:36:04.750 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-250309A ranges from 1.7e+00 to 1.8e+00 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)

L. Scotton (UAH) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event IceCube-250309A
(GCN 39631
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 ), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 211.07 (+0.31 -0.30 deg  90% PSF containment) J2000
Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000

Fermi-GBM detected GRB 250309B (GCNs 39635
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 , 39642
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 ) around 
146s after the time of the neutrino candidate. However, 
the ZTF and GROWTH collaborations reported the detection 
of a potential optical counterpart ZTF25aaitvjt | AT2025dws
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(R. Stein et al, GCN 39639
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 ), suggesting that GRB 250309B 
and IceCube-250309A are unrelated. The IPN triangulation 
(Kozyrev A. S. et al, GCN 39652
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 ) also suggests that 
GRB 250309B and IceCube-250309A are unrelated.    

An automated, blind search for short gamma-ray bursts below 
the onboard triggering threshold in Fermi-GBM also identified 
no counterpart candidates. The GBM targeted search, the most 
sensitive, coherent search for GRB-like signals, was run 
from +/-30 s around the neutrino candidate time. From this search, 
no significant signal was found related to IceCube-250309A.

Using the representative soft, normal, and hard GRB-like templates 
described in arXiv:2308.13666
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 , we set the following 3 sigma flux 
upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2):

Timescale   Soft     Normal   Hard
-------------------------------------------
0.128 s:    1.0      1.8      3.7
1.024 s:    0.35     0.56     1.3
8.192 s:    0.11     0.11     0.24

These results are preliminary.

Robert Stein (JSI), Jannis Necker, Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum), Tomas Ahumada (Caltech), Jesper Sollerman (Stockholm) 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-250309A (Zegarelli et. al, GCN 39631
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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 deep observations in the g- and r-band beginning at 2025-03-09 10:16 UTC while the same field was also observed by the routine ZTF survey at 08:18 UTC, approximately 0.7 hours after event time. We covered 92.9% (0.3 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 candidate within the 90.0% localization of the skymap.

±–––––––––––––––––––––––––––––––––––––––-+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr |
±–––––––––––––––––––––––––––––––––––––––-+
| ZTF25aaiurnn | –––- | 211.3537073 | -10.4938701 | g | 20.82 | 0.18 |
±–––––––––––––––––––––––––––––––––––––––-+

ZTF25aaiurnn was first detected on 2025-03-02 in the r-band, roughly one week before the neutrino arrival. It has a match in the MILLIQUAS catalog at a distance of 0.18 arcsec as a 95% probable QSO. The match in the AllWISE source catalog (WISEA J140524.90-102938.0, 0.22 arcsec) shows a red color of W1-W2=1), consistent with an AGN. Although there is only one detection per band, there is no clear evidence for coincident flaring activity.

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

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 Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, 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; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.

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 ).

S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), N. Di Lalla (Stanford Univ.), M. Arimoto (Kanazawa University), R. Gupta (NASA GSFC) and A. Holzmann Airasca (UniTrento and INFN Bari)  on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy IC250309A neutrino event (GCN 39631
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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 2025-03-09 07:36:04.75 UTC (T0) with J2000 position RA = 211.07 (+0.31, -0.30) deg, Decl. = -10.73 (+0.26, -0.30) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250309A 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 IC250309A 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 <2.4e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <6.8e-09 (<9.3 e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0.

The IceCube event IC250309A occurred near the GRB 250309B (GCN 39635
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 ), with a detection time 145.91 seconds after the Fermi-GBM trigger and a positional separation of 0.50 deg. An analysis of the LAT data conducted over a ±1000-second window centered on T0, shows no significant excess emission, neither associated with IC250309A nor GRB 250309B. The  >100 MeV flux upper limit (95% confidence) at IC250309A best-fit position for this time interval is  < 5.3 e-6 ph cm^-2 s^-1.  

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 S. Buson (sara.buson at 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.

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

On 2025-03-09 at 07:36:04.75 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 0.1759 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/140626_1288692.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2025-03-09
Time:  07:36:04.75 UT
RA: 211.07 (+0.31 -0.30 deg  90% PSF containment) J2000
Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000

The inferred neutrino energy of this alert is ~4 PeV, making it the fourth-highest energy known detection by IceCube over the past decade.

The alert coincides with the Fermi GRB250309B (Fermi-GBM trigger 763198715 at 07:38:30.66 on 09 March 2025; https://gcn.gsfc.nasa.gov/other/763198715.fermi) with a time delay of 145.91 seconds relative to the GRB trigger time. The angular distance to the most updated reconstruction released by the GBM team, which has a 1σ statistical error of 1.60 deg, is 0.77 degrees. An alternative algorithm results in a shifted direction (https://gcn.nasa.gov/circulars/39629
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 ) with an angular distance from the best fit neutrino direction of 3.18 degrees and has a 1σ statistical error of 1.3 degree and a systematic error of 1 degree.

We strongly encourage follow-up observations of the neutrino region of interest and the uncertainty region of GRB250309B.

No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the 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