IceCube-230603A

S. Garrappa (Ruhr-Universitaet Bochum), 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 IC230603A   high-energy neutrino event (GCN 33911
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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 2023-06-03 at 05:00:47.13 UT (T0) with J2000 position RA =68.20 (+2.62, -3.06) deg, Decl. = +24.21 (+2.08, -2.59) deg (90% PSF containment).  Two cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230603A localization region. These are 4FGL J0439.2+2151, associated with the blazar candidate of uncertain type IERS B0435+217, and the unassociated source 4FGL J0441.8+2600c. 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 IC230603A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230603A 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 2023-06-03 UTC), and < 9.7e-9 (< 9.5e-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 region will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa atruhr-uni-bochum.de <http://ruhr-uni-bochum.de/>), J. Sinapius (jonas.sinapius atdesy.de <http://desy.de/>) and S. Buson (sara.buson atuni-wuerzburg.de <http://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-230603A (https://gcn.nasa.gov/circulars/33911
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 ) in a time range of 1000 seconds centered on the alert event time (2023-06-03 04:52:27.130 UTC to 2023-06-03 05:09:07.130 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-230603A. 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-230603A 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 2e+02 GeV and 8e+04 GeV.


A subsequent search was performed including 2 days of data centered on the alert event time (2023-06-02 05:00:47.130 UTC to 2023-06-04 05:00:47.130 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-230603A is 1.7e-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)

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

On 2023-06-03 at 05:00:47.13 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 Bronze alerts is 30%.

This alert has an estimated false alarm rate of 1.24 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/138005_24780443.amon), more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:

Date: 2023-06-03
Time:  05:00:47.13 UT
RA: 68.20 (+2.62 / -3.06 deg  90% PSF containment) J2000
Dec: +24.21 (+2.08 / -2.59 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 gamma-ray sources listed in the 4FGL-DR3 Fermi-LAT catalog are
located within the 90% uncertainty region. The nearest source is 4FGL
J0439.2+2151, located 2.79 deg away from the best-fit alert 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