IceCube-220303A

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

On 2022-03-03 at 18:00:07.62 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 0.54 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/136385_7450363.amon), more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:

Date: 2022-03-03
Time:  18:00:07.62
RA: +267.80 (+1.50/-1.17 deg  90% PSF containment) J2000
Dec: +11.42 (+0.89/-1.14 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.

There are no Fermi 4FGL or 3FHL catalog sources in the 90% uncertainty
region. The nearest gamma-ray sources in either catalog are 4FGL
J1745.5+1017 at RA: 266.40 deg, Dec: 10.30 deg and 4FGL J1751.5+0938
(OT 081) at RA: 267.88 deg, Dec: 9.65 (in J2000 coordinates, both 1.78
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

K.Zhirkov  behalf MASTER team

MASTER-Net automatically inspected IceCube-220303A error 
box (Ttrigger=2022-03-03 18:00:07.62UT, Tnotice=2022-03-03 20:49:24UT).
MASTER auto-detection system discovered Tev blazar 4C 09.57 
(http://simbad.u-strasbg.fr/simbad/sim-id?Ident=0FGL%20J1751.5%2B0935%20 ) 
inside   3-sigma error-box in high stage state in 10 hours after the 
trigger time.

The analysis will be continued.
Additional observations are planned.

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and J. 
Sinapius (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC220303A neutrino event (GCN 31670
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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 2022-03-03 18:00:07.62 UTC 
(T0) with J2000 position RA = 267.80 (+1.50, -1.17) deg, Decl. = 11.42 
(+0.89, -1.14) deg 90% PSF containment. No cataloged gamma-ray sources 
are found within the 90% IC220303A localization error (4FGL-DR3; 
arXiv:2201.11184
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 ; The Fermi-LAT collaboration 2020, ApJS, 247, 33).

We searched for the existence of intermediate (months to years) 
timescale emission from a new gamma-ray transient source. Preliminary 
analysis indicates no significant (>5sigma) new excess emission (> 100 
MeV) within the IC220303A 90% confidence localization. Assuming a 
power-law spectrum (photon index = 2.0 fixed) for a point source at the 
IC220303A best-fit position, the >100 MeV flux upper limit (95% 
confidence) is < 5.6-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 
2022-03-03 UTC), <4.6-9 (< 6.6-8) 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 source will continue. For this source the Fermi-LAT 
contact persons are S. Garrappa (simone.garrappa at desy.de) and 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:

IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-220303A (https://gcn.gsfc.nasa.gov/gcn3/31670.gcn3
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 ) in a time range of 1000 seconds centered on the alert event time (2022-03-03 17:51:47.620 UTC to 2022-03-03 18:08:27.620 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-220303A. 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-220303A is 1.3e-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 1e+05 GeV.

A subsequent search was performed including 2 days of data centered on the alert event time (2022-03-02 18:00:07.620 UTC to 2022-03-04 18:00:07.620 UTC). In this case, we report a p-value of 0.12, 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-220303A ranges from 1.5e-01 to 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<mailto:roc@icecube.wisc.edu>.

[1] IceCube Collaboration, R. Abbasi  et al., ApJ 910 4 (2021)

Felicia McBride, Derek B. Fox, Doug Cowen, Hugo Ayala Solares, Timoth��e 
Gregoire, Jamie Kennea (PSU), Alexis Coleiro (APC), and Phil Evans 
(Leicester) report for AMON (https://amon.psu.edu/):

The Neil Gehrels Swift Observatory X-ray Telescope (XRT) observed the 
uncertainty region of the IceCube neutrino event IceCube-220303A (GCN 
Circ. 31679
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 ) on 2022-03-04, between 00:22 and 02:25 UTC.
A 10-point tiling observation centered on the neutrino position was 
taken for a total of 4 ksec.
Of the 90% confidence 4.3 sq. degrees uncertainty region, the XRT 
observations cover roughly 50% of the central area, but the 50% 
uncertainty region almost completely.

 ��One X-ray candidate counterpart was detected at the coordinates of 
R.A.: 267.715732, Dec.: 10.9488175 (J2000.0), which may be consistent 
with the source WISEA J175051.31+105645.3 at a redshift of 0.066. The 
0.5-10 keV flux of the source is ~5e-13 erg/s/cm^2, but cannot be 
constrained well due to the short observation. We have requested 
follow-up observations with NuSTAR.

Multiwavelength follow-up observations are encouraged.

Hugo Ayala (Penn State) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 2022/03/03 18:00:07 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-220303A. Location is at
RA: 267.80 (+1.50/-1.17 deg  90% PSF containment) J2000
Dec: 11.42 (+0.89/-1.14 deg 90% PSF containment) J2000
(GCN circular 31670
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 ).

We performed two types of analyses for the follow-up. The first is for
a steady source in archival data and the second is a search for a
transient source. We assume a power-law spectrum with an index of -2.3
for both analyses.

Search for a steady source in archival data:
The archival data spans from November 2014 to June 2019. We searched
inside the reported IceCube error region.
The most significant location, with p-value 1.02e-2 (2.46e-1 post-trials),
is at RA 268.29 deg, Dec +11.34 deg (��0.18 deg 68% containment) J2000.
We set a time-integrated 95% CL  upper limit on gamma rays at the
maximum position of:

E^2 dN/dE = 6.9e-14 (E/TeV)^-0.3 TeV.cm^-2.s^-1

Search for a transient source.

Since the event was not in our field of view at the time reported,
we report the combined result for the transits before and after the
IceCube event.

Data acquisition started on 2022/03/02 16:29:02 UTC and ended
2022/03/04 16:39:48 UTC.
The most significant location, with p-value 2.05e-3 (5.51e-2 post-trials),
is at RA 269.12 deg, Dec 10.24 deg (��0.25 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:

E^2 dN/dE = 1.0729e-11 (E/TeV)^-0.3 TeV.cm^-2.s^-1

HAWC is a very-high-energy gamma-ray observatory operating in Central
Mexico at latitude 19 deg. north. Operating day and night with over
95% duty cycle, HAWC has an instantaneous field of view of 2 sr and
surveys 2/3 of the sky every day. It is sensitive to gamma rays from
300 GeV to 100 TeV.