IceCube-191119A

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

On Nov 19, 2019 at 01:01:29.38 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 threshold astrophysical neutrino purity  for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.54 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/133331_47828126.amon), more  sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 19/11/19 (yy/mm/dd)
Time:  01:01:29.38 UT
RA: 230.10 (+4.76/-6.48 deg  90% PSF containment) J2000
Dec: 3.17 (+3.36/-2.09 deg 90% PSF containment) J2000

The geometry of this event was near the edge of the instrumented volume of IceCube and yielded a somewhat larger 90% uncertainty region when compared to typical realtime alert events. We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

Several gamma-ray sources listed in the 4FGL Fermi-LAT catalog are located within 90% containment region about the best-fit candidate neutrino position. The closest source is
4FGL J1518.8+0203, located 1.2 deg away from the best-fit position. A total of 11 sources listed in the 4FGL catalog are contained in a 5 deg radius from the best-fit position, which approximately corresponds to the 90% containment radius of the event.

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

Maeve Doyle (UCD, Ireland), James Rodi  (IAPS-Roma, Italy)
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
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-191119A (GCN 26258
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 ).

At the time of the event (2019-11-19 01:01:29 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 88 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(7.9% of optimal) response of ISGRI, strongly suppressed (27% of
optimal) response of IBIS/Veto, and strongly suppressed (34% of
optim al) response of SPI-ACS.

The background within +/-300 seconds around the event was rather
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 4.9e-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 ~5.1e-07 (1.6e-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:

scale | T | S/N | flux ( x 1e-06 erg/cm2/s) | FAP  
0.25 | 0.978 | 3.1 | 1.07 +/- 0.389 +/- 0.5 | 0.0794 
1.4 | 16.3 | 3.4 | 0.498 +/- 0.164 +/- 0.233 | 0.104 
0.9 | 20 | 3.3 | 0.616 +/- 0.204 +/- 0.289 | 0.23  
1 | 115 | 3.6 | 0.63 +/- 0.194 +/- 0.295 | 0.699 
1.1 | 290 | 4.1 | 0.697 +/- 0.185 +/- 0.327 | 0.738 
0.45 | 77.4 | 3.6 | 0.955 +/- 0.29 +/- 0.447 | 0.997 
0.35 | -38.3 | 3.4 | 0.988 +/- 0.328 +/- 0.463 | 1  

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 191119A (GCN 26258
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 ),
at the event time Fermi-GBM was observing the reported neutrino location at:

RA: 230.10 (+4.76/-6.48 deg  90% PSF containment) J2000
Dec: 3.17 (+3.36/-2.09 deg 90% PSF containment) J2000

There was no Fermi-GBM onboard trigger around the event time of the
neutrino candidate. An automated, blind search for short gamma-ray bursts
below the onboard triggering threshold in Fermi-GBM also identified no
counterpart candidates. The GBM targeted search, the most sensitive,
coherent search for GRB-like signals, was run from +/-30 s around the
neutrino candidate time. From this search, no significant signal was found
related to IceCube-191119A.

We set upper limits on impulsive gamma-ray emission. Using the
representative soft, normal, and hard GRB-like templates
(arXiv:1612.02395
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 ), we report the following 3 sigma flux upper limits over
10-1000 keV (in units of 10^-7 erg/s/cm^2):

Timescale  soft     norm     hard
--------------------------------------
0.128 s:   5.0      8.4      22.0
1.024 s:   1.3      2.2      5.4
8.192 s:   0.6      1.1      2.9

S. Garrappa (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 high-energy 
IC191119A neutrino event (GCN 26258
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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 2019-11-19 01:01:29.38 UT 
(T0) with J2000 position RA = 230.10 (+4.76, -6.48) deg, Decl. = 3.17 
(+3.36, -2.09) deg 90% PSF containment. Several cataloged >100 MeV 
gamma-ray sources are located within the 90% IC191119A localization 
error. Based on a preliminary analysis of the LAT data, none of those is 
significantly detected at gamma-rays over a 1-day and 1-month timescale 
prior T0.

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 IC191119A 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 < 6e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-11-19 UTC), < 1e-8 (< 1e-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 this source the Fermi-LAT 
contact person 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.

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-191119A (https://gcn.gsfc.nasa.gov/gcn3/26258.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2019-11-18 01:01:29.380 UTC to 2019-11-20 01:01:29.380 UTC) during which IceCube was collecting good quality data. Excluding the
event that prompted the alert, one additional track-like event is found in spatial coincidence
with the 90% containment region of IceCube-191119A. We find that these data are well described by atmospheric background expectations, with a p-value of 1.0. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/ dE = 4.0 x 10^-5 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 8 PeV.

A subsequent search was performed to include the previous month of data (2019-10-19 01:01:29.380 UTC to 2019-11-20 01:01:29.380 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
 9.5 x 10^-5 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>.

Alexis Coleiro (APC/Universite de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. 

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported single track-like event IceCube-191119A (GCN 26258
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  <https://gcn.gsfc.nasa.gov/gcn3/26258.gcn3
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  <https://gcn.gsfc.nasa.gov/gcn3/26258.gcn3
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 >>). The reconstructed origin was 37.0 degrees below the horizon for ANTARES.

No up-going muon neutrino candidate events were recorded within 3 degrees of the IceCube event coordinates during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible all time. A search over an extended time window of +/- 1 day has also yielded no detection (48% visibility).

This leads to a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 16 GeV.cm^-2 over the energy range 3.4 TeV - 3.6 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 28 GeV.cm^-2 (656 GeV - 338 TeV) for an E^-2.5 spectrum.

ANTARES <http://antares.in2p3.fr/ <http://antares.in2p3.fr/>> is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky.

Hugo Ayala (PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):
On 2019/11/19 01:01:29 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-191119A. Location is at
RA: 230.10 (+4.76/-6.48 deg  90% PSF containment) J2000
Dec: 3.17 (+3.36/-2.09 deg 90% PSF containment) J2000
(GCN circular 26258
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 ).

We performed two types of analyses for the follow-up. The first is for
a steady source in archival data and the second is a search for a
transient source. We assume a power-law spectrum with an index of -2.3
for both analyses.

Search for a steady source in archival data:
The archival data spans from November 2014 to May 2018. We searched
inside the reported IceCube error region from the circular.
The highest significance, 4.03 sigma (2.38 post-trials),
is at RA 226.10 deg, Dec 1.42 deg J2000.
We set a time-integrated 95% CL  upper limit on gamma rays at the
maximum position of:

E^2 dN/dE = 3.97e-13 (E/TeV)^-0.3 TeV cm^-2 s^-1

Search for a transient source.
Since the event was not in our field of view at the time reported,
we report the combined result for the transits before and after the
IceCube event.
Data acquisition started on 2019/11/17 20:48:09 UTC and ended
2019/11/19 20:53:47 UTC.
The most significant location, with 2.75 sigma (-1.75 post-trials),
is at RA 229.41 deg, Dec 2.05 deg (J2000).
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:

E^2 dN/dE = 2.00e-11 (E/1TeV)^-0.3 TeV cm^-2 s^-1

HAWC is a very-high-energy gamma-ray observatory operating in Central
Mexico at latitude 19 deg. north. Operating day and night with over
95% duty cycle, HAWC has an instantaneous field of view of 2 sr and
surveys 2/3 of the sky every day. It is sensitive to gamma rays from
300 GeV to 100 TeV.