IceCube-231125A

L. Pfeiffer (Univ. of Wuerzburg), S. Buson (Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the IC231125A high-energy neutrino event (GCN 35194
Loading...
 
 ) 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 2023-11-25 at 22:34:56.64 UT (T0) with J2000 position RA = 177.53 (+3.99, -4.03) deg, Decl. = +53.62 (+1.57, -1.64) deg (90% PSF containment). There are two gamma-ray (>100 MeV; 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546
Loading...
 
 ) sources located within the 90% IC231125A localization region. These are:

4FGL J1215.0+5351, associated with the BL LAC GB6 J1215+5349;
4FGL J1208.9+5441, associated with the FSRQ TXS 1206+549

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 IC231125A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC231125A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.77e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2023-11-26 UTC), and < 8.10e-9 (<8.91e-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 person is L. Pfeiffer (leonard.pfeiffer at stud-mail.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-231125A (https://gcn.nasa.gov/circulars/35194
Loading...
 
 ) in a time range of 1000 seconds centered on the alert event time (2023-11-25 22:26:36.640 UTC to 2023-11-25 22:43:16.640 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-231125A. 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-231125A ranges from 1.5e-01 to 1.7e-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 5e+04 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2023-11-24 22:34:56.640 UTC to 2023-11-26 22:34:56.640 UTC). In this case, we report a p-value of 0.81, 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-231125A ranges from 1.8e-01 to 2.1e-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)

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

The error on the right ascension of the high-energy track-like event IceCube-231125A reported in GCN circular 35192
Loading...
 
  was incorrectly reported. All other information was correct. The corrected refined directional information is:

Date: 2023-11-25
Time:  22:34:56.64 UT
RA: 177.53 (+3.99, -4.03 deg  90% PSF containment) J2000
Dec: +53.62 (+1.57, -1.64 deg 90% PSF containment) J2000

We apologize for the error. 

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

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

On 2023-11-25 at 22:34:56.64 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 0.1472 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/138599_39138591.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2023-11-25
Time:  22:34:56.64 UT
RA: 177.53 (+2.20, -2.27 deg  90% PSF containment) J2000
Dec: +53.62 (+1.57, -1.64 deg 90% PSF containment) J2000

An error in the automatic processing pipeline that performs the offline reconstruction resulted in a delay in the circulation of the updated position. Therefore, an alternative reconstruction algorithm has been applied to this event. 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 source in either catalog is 4FGL J1202.9+5141 at RA: 180.74 deg, Dec: +51.69 deg (2.74 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