IceCube-230405A

On 2023-04-05 at 13:20:20.04 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 2.84 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/137806_8756840.amon), more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:

Date: 2023-04-05
Time: 13:20:20.04 UT
RA: 120.85 (+2.86 / -4.98 deg 90% PSF containment) J2000
Dec: +9.75 (+1.87 / -2.17 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.

Six gamma-ray sources listed in the 4FGL-DR3 Fermi-LAT catalog are
located within the 90% containment radius of the event. The nearest
source is 4FGL J0802.0+1006 located at RA 120.51 deg, Dec 10.11 deg
J2000, 0.49 deg away from the best-fit 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 (Ruhr-Universitaet Bochum), J. Sinapius (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 IC230405A�� 
high-energy neutrino event (GCN 33567
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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 2023-04-05 at 13:20:20.04 
UT (T0) with J2000 position RA = 120.85 (+2.86, -4.98) deg, Decl. = 
+9.75 (+1.87, -2.17) deg (90% PSF containment).�� Seven cataloged 
gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) 
sources are located within the 90% IC230405A�� localization region. Based 
on a preliminary analysis of the LAT data over a month and day timescale 
prior T0, these objects are not significantly detected at gamma rays.

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 IC230405A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC230405A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 1.8e-10 ph cm^-2 s^-1 for 
~14-years (2008-08-04 to 2023-04-05 UTC), and < 9.4e-9 (<1.7e-7) 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 region will continue. For these observations the 
Fermi-LAT contact persons are S. Garrappa (simone.garrappa at 
ruhr-uni-bochum.de), J. Sinapius (jonas.sinapius 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-230405A (https://gcn.gsfc.nasa.gov/gcn/gcn3/33567.gcn3
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  ) in a time range of 1000 seconds centered on the alert event time (2023-04-05 13:12:00.040 UTC to 2023-04-05 13:28:40.040 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-230405A. 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-230405A 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 (2023-04-04 13:20:20.040 UTC to 2023-04-06 13:20:20.040 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-230405A is 1.5e-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)

D. R. Xiong, J. M. Bai, Y. F. Fan, K. Ye, C. J. Wang, Y. X. Xin, B. L. Lun, J. R. Mao, X. H. Zhao, L. Xu, X. G. Yu, K. X. Lu, X. Ding, D. Q. Wang (Yunnan Observatories), A. J. Castro-Tirado, E. Fernandez-Garcia, Y. D. Hu (IAA-CSIC) and C. J. Perez del Pulgar (UMA) on behalf of the BOOTES team report:

On 2023-04-05 at 13:20:20.04 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin (GCN 33567
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 ). We observed the nearest gamma-ray source 4FGL J0802.0+1006 and the best-fit position of IceCube-230405A with BOOTES-4/MET robotic telescope.The magnitudes were calculated using bright stars in the same frame and the SDSS-DR16 as reference. We did not detect any optical source within the best-fit position, and also the optical counterparts of 4FGL J0802.0+1006. The upper limits of magnitudes (without being corrected for Galactic extinction) are given as follows. 

Sources | Tmid-T0 (day) | UT (start) | Upper Limit (error) | Exposure Time | Filter 

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Best-fit position| 1.18 | 23-04-06 17:43:37.49 | 18.96 (0.06) | 300s | SDSS-i  

J0802.0+1006 | 1.2 | 23-04-06 18:08:52.38 | 18.69 (0.04) | 300s | SDSS-i

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The Burst Optical Observer and Transient Exploring System (BOOTES, bootes.iaa.es) is a completed world-wide network of robotic telescopes led at IAA-CSIC (Spain) which aims at following-up transients and other astrophysical sources in the sky for which the first station was installed in 1998 (Castro-Tirado et al. 1999). The fourth station of the BOOTES Network, BOOTES-4/MET, is located at the Lijiang Observatory of the Yunnan Observatories of China (Xiong et al. 2020). See also Hu et al. (2021). We acknowledge the support of BOOTES-4 technical staffs.