IceCube-210717A

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

On 21/07/17 at 15:45:19.48 UT IceCube detected a high-energy starting event [1]. The IceCube online selection did not identify this event as a Gold or Bronze starting track. However, based on advanced reconstructions performed offline, we identify this event as a potential astrophysical neutrino of interest to the community, given its topology and light deposition. Because the event was not identified as either Gold or Bronze, we do not currently report a false alert rate or signalness. The IceCube detector was in a normal operating state at the time of detection.

Advanced reconstruction algorithms have been applied offline, with the direction estimated to be:

Date: 21/07/17
Time: 15:45:19.48 UT
RA: 46.49 (+ 2.40 - 2.57 deg 90% PSF containment) J2000
Dec: -1.34 (+ 2.63 - 3.41 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 is one Fermi-LAT 4FGL source inside the 90% localization region, 4FGL J0304.5-0054, located at RA 46.14 deg and Dec -0.91 deg (J2000), at a distance of 0.55 degrees from the best-fit location. The source is also listed in the Fermi 3FHL hard-spectrum source catalog.

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] The IceCube Collaboration, Phys. Rev. Lett. 113, 101101 (2014)

V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
<https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration>

Using combination of INTEGRAL all-sky detectors (following [1]):
SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt
gamma-ray counterpart of IceCube-210717A (GCN 30468
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 ).

At the time of the event (2021-07-17 15:45:19 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 124 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (4.1% of optimal) response of ISGRI, strongly suppressed
(29% of optimal) response of IBIS/Veto, and somewhat suppressed (58%
of optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

We have performed a search for any impulsive events in INTEGRAL SPI-
ACS (as described in [2]), IBIS, and IBIS/Veto data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 3.1e-07 erg/cm^2 (within the
50% probability containment region of the source localization) for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and
Ep=300 keV), the derived peak flux upper limit is ~2.7e-07 (7.1e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

We report for completeness and in order of FAP, all excesses
identified in the search region. We find: 4 likely background
excesses:

T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP
-32 | 0.15 | 4.1 | 1.12 +/- 0.291 +/- 0.491 | 0.596
-162 | 2.1 | 3.4 | 2.39 +/- 0.767 +/- 1.05 | 0.68
152 | 2 | 3.3 | 2.36 +/- 0.786 +/- 1.04 | 0.832
-149 | 0.35 | 4.4 | 0.768 +/- 0.189 +/- 0.338 | 0.966

Note that FAP estimates (especially at timescales above 2s) may be
possibly further affected by enhanced non-stationary local background
noise. This list excludes any excesses for which FAP is close to
unity.



All results quoted are preliminary.

This circular is an official product of the INTEGRAL Multi-Messenger
team.

[1] Savchenko et al. 2017, A&A 603, A46
[2] Savchenko et al. 2012, A&A 541A, 122S

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and R. de 
Menezes (Univ. of Sao Paulo, Univ. of Wuerzburg) on behalf of the 
Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy 
IC210717A neutrino event (GCN 30468
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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 2021-07-17 at 15:45:19.48 
UT (T0) with J2000 position RA = 46.49 (+ 2.40, - 2.57) deg, Decl. = 
-1.34 (+ 2.63, - 3.41) deg (90% PSF containment). Three cataloged 
gamma-ray (>100 MeV) sources are located within the 90% IC210717A 
localization region (4FGL-DR2, The Fermi-LAT collaboration 2020, ApJS, 
247, 33). Based on a preliminary analysis of the LAT data over the 
timescale of 1-day and 1-month prior to T0, none of these objects is 
significantly detected (> 5 sigma).

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 IC210717A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC210717A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 1.2e-10 ph cm^-2 s^-1 for 
~12-years (2008-08-04 to 2021-07-17 UTC), and < 1.4e-8 (< 1.0e-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 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.