IceCube-220405A

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

On 2022-04-05 at 04:57:26.12 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 3.28 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/136504_1833389.amon), more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:

Date: 2022-04-05
Time:  04:57:26.12 UT
RA: +134.47 (+1.71/-1.72 deg  90% PSF containment) J2000
Dec: -1.27 (+1.45/-1.02 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-DR3 or 3FHL catalog sources in the 90%
uncertainty region. The nearest gamma-ray source in either catalog is
4FGL J0859.8+0053 at RA: 134.95 deg, Dec: 0.90 deg J2000 (2.22 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

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

We report an analysis of observations of the vicinity of the high-energy 
IC220405A neutrino event (GCN 31833
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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 2022-04-05 at 04:57:26.12�� 
UT (T0) with J2000 position RA = +134.47 (+1.71, -1.72) deg, Decl. = 
-1.27 (+1.45, -1.02) deg (90% PSF containment). No cataloged gamma-ray 
(>100 MeV) sources are located within the 90% IC220405A localization 
region (4FGL-DR3; arXiv:2201.11184
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 ; The Fermi-LAT collaboration 2020, 
ApJS, 247, 33).

We searched for intermediate (days to years) timescale emission from a 
new gamma-ray transient source. Preliminary analysis indicates no 
significant (> 5 sigma) new excess emission (> 100 MeV) at the IC220405A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC220405A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 1.1e-10 ph cm^-2 s^-1 for 
~13-years (2008-08-04 to 2022-04-05 UTC), and < 3.2e-9 (< 8.0e-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 these observations 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:

On 2022-04-05 at 22:20:03.41 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 2.02 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/136506_15341152.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2022-04-05
Time:  22:20:03.41 UT
RA: 320.62 (+1.37, -1.13 deg  90% PSF containment) J2000
Dec: 29.06 (+0.94, -0.68 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 sources in the  4FGL-DR2 Fermi-LAT catalog in the 90% uncertainty region.  The nearest source is 4FGL J2115.4+2932 (318.87 deg, 29.55 deg J2000, 1.82 deg away from the best-fit neutrino 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

Simeon Reusch, Jannis Necker (DESY), Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum) and Anna Franckowiak (DESY/Ruhr University Bochum),

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. 2022), observed the localization region of the neutrino event IceCube-220405A (Lincetto et. al, GCN 31833
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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 2022-04-05 05:31 UTC, approximately 0.6 hours after event time. We covered 98.3% (7.5 sq deg) of the reported localization region. This estimate accounts for chip gaps. Two of the exposures lasted 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).

No candidate counterparts were detected.

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 AMPEL Follow-up Pipeline (Stein et al. 2021).