IceCube-191215A

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

On 19/12/15 at 11:09:57.63 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 0.34 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/133433_29047901.amon <https://gcn.gsfc.nasa.gov/notices_amon_g_b/133433_29047901.amon>), more 
sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 19/12/15 
Time: 11:09:57.63 UT
RA: 285.87 (+2.88 -3.19 deg 90% PSF containment) J2000
Dec: 58.92 (+1.85 -2.25 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 or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J1858.7+5708 at RA: 284.70 deg, Dec: 57.15 deg (1.88 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 <mailto:roc@icecube.wisc.edu>

Diego Gotz (AIM/DAp CEA Saclay, France), Alexander Lutovinov (IKI Russia)
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 INTEGRAL/SPI-ACS realtime data (following [1]) we have performed
a search for a prompt gamma-ray counterpart of IceCube-191215A.

At the time of the event (2019-12-15 11:09:57 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 28 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(17% of optimal) response of ISGRI, strongly suppressed (25% of
optimal) response of IBIS/Veto, and somewhat suppressed (46% of
optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.2).

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

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 3.7e-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 ~3.4e-07 (1e-07)
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: 7 likely background
excesses:

T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP  
-98.7 | 1.1 | 4 | 0.564 +/- 0.154 +/- 0.299 | 0.281 
15.3 | 0.45 | 3.2 | 0.65 +/- 0.241 +/- 0.344 | 0.526 
98.7 | 1.15 | 3.5 | 0.442 +/- 0.15 +/- 0.234 | 0.635 
22.1 | 0.05 | 4 | 2.55 +/- 0.738 +/- 1.35 | 0.826 
-38.6 | 0.4 | 3.4 | 0.761 +/- 0.256 +/- 0.403 | 0.827 
7.26 | 0.05 | 3.4 | 2.17 +/- 0.735 +/- 1.15 | 0.951 
-119 | 0.4 | 4 | 0.873 +/- 0.256 +/- 0.463 | 0.969 

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

C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event 191215A (GCN 26435
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 ),
the reported position:

RA: 285.87 (+2.88 -3.19 deg 90% PSF containment) J2000
Dec: 58.92 (+1.85 -2.25 deg 90% PSF containment) J2000

was occulted by the Earth for Fermi-GBM from approximately 27.1 minutes prior
until 1.6 minutes after event time. Therefore, the GBM observations are not
constraining for prompt gamma-ray emission.

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

IceCube has performed a search for additional track-like muon neutrino events arriving
from the direction of IceCube-191215A (https://gcn.gsfc.nasa.gov/gcn3/26435.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2019-12-14 11:09:57.63 UTC to 2019-12-16 11:09:57.63 UTC) during which IceCube was collecting good quality data. Excluding the
event that prompted the alert, three additional track-like events are found in spatial coincidence
with the 90% containment region of IceCube-191215A. We find that these data are consistent with atmospheric background expectations, with a p-value of 0.015. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/ dE = 1.08 x 10^-4 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are approximately between 1 TeV and 200 TeV.

A subsequent search was performed to include the month of data prior to the alert event (2019-11-15 11:09:57.63 UTC to 2019-12-16 11:09:57.63 UTC). In this case, we report a p-value of 1.0, consistent with no significant excess of track-like events, and a corresponding time-integrated muon-neutrino flux upper limit assuming an E^-2 spectrum (E^2 dN/dE) of
 1.36 x 10^-4 TeV cm^-2 at the 90% CL.

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>.

S. Garrappa (DESY-Zeuthen), 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 
IC191215A neutrino event (GCN 26435
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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 2019-12-15 11:09:57.63 UTC 
(T0) with J2000 position RA =285.87 (+2.88 -3.19) deg, Decl. = 58.92 
(+1.85 -2.25) deg 90% PSF containment. One cataloged >100 MeV gamma-ray 
source is located within the 90% IC191215A localization error, at a 
distance of roughly 1.88 deg. This is the object 4FGL J1858.7+5708�(The 
Fermi-LAT Collaboration 2019, arXiv:1902.10045
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 ) associated with the 
blazar candidate object of uncertain type 87GB 185759.9+570427. Based on 
a preliminary analysis of the LAT data over the timescales of 1-day and 
1-month prior to T0, this object is not significantly detected at 
gamma-rays.

We searched for the existence of intermediate (months to years) 
timescale emission from a new gamma-ray transient source. Preliminary 
analysis indicates no significant (>5sigma) new excess emission (> 100 
MeV) within the IC191215A 90% confidence localization. Assuming a 
power-law spectrum (photon index = 2.0 fixed) for a point source at the 
IceCube best-fit position, the >100 MeV flux upper limit (95% 
confidence) is < 2.2e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-12-15 UTC), < 4.2e-8 (< 1e-8) ph cm^-2 s^-1 for a 1-day (1-month) 
integration time before T0.

Since Fermi normally operates in an all-sky scanning mode, regular 
monitoring of the region will continue. For this event the Fermi-LAT 
contact person are S. Garrappa (simone.garrappa atdesy.de 
<http://desy.de/>) and S. Buson (sara.buson atgmail.com 
<http://gmail.com/>). 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.