IceCube-201115A

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

On 20/11/15 at 02:07:26.21 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 1.523 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/134699_70289682.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 20/11/15
Time:  02:07:26.21 UT
RA: 195.12 (+ 1.27 - 1.49  deg  90% PSF containment) J2000
Dec: 1.38 (+ 1.30 - 1.11 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-LAT 4FGL or 3FHL sources inside the 90% localization region. The closest source is 4FGL J1250.6+0217 located at RA 192.65 deg and Dec 2.29 deg (J2000), at a distance of 2.63 degrees from the best-fit location.

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 following is an abbreviated form of Astronomers Telegram #14177. Here
we fix the link to the original IceCube GCN for the source (we originally
missed the N, which prevents auto linking in ATels).

IceCube-201115A is a recently detected (gold-track) astrophysical neutrino
(GCN #28889
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 ), localized at 90% PSF containment to (J2000):
RA: 195.12 (+ 1.27 / - 1.49) deg
Dec: 1.38 (+ 1.30 / - 1.11) deg.
Here, we present potential counterparts with precursor (2019 April 21)
radio emission at 2-4 GHz from the catalog of the Very Large Array Sky
Survey Epoch 1 Quick Look Components catalog (Gordon et al. 2020, RNAAS, 4,
175). We highlight the brightest component in particular, VLASS1QLCIR
J125908.35+013606.4 (with a peak radio flux density of 172.3 +/- 0.2 mJy,
and an association to SDSS J125908.28+013605.3). This source may be
associated with a BL Lac type object.

The VLASS detection consists of multiple components. Visual inspection
shows a bright source and a ~2.5x fainter source about 6" to the south
east. We interpret these as either two radio lobes (or less likely two jet
knots) as SDSS J125908.28+013605.2 (aka SDSS J125908.28+013605.3) lies
directly between the sources. This optical source has a photo-z of
0.62+/-0.05. While the Initial Gaia Source List (Smart and Nicastro 2013)
indicates a 5.2 sigma non-zero proper motion, this catalog states it should
be used for care for individual sources. We discount the likelihood that
this is a Galactic source, given the two radio detections.

We adopt the Sloan position of the source, specifying positional errors
that contain the VLASS radio emission, after accounting for potential 0.5"
accuracy issues with VLASS Epoch 1 data in their current processing stage:
RA: 194.78452 +/- 0.00028 deg
Dec: 1.601466 +/- 0.000018 deg.
The VLASS QL position (RA = 194.784795+/- 0.000003, Dec = 1.601785 +/-
0.000002) is 1.5" offset from the SDSS position due to the asymmetry in the
radio emission. The radio "source" that typically describes the two VLASS
components is PKS 1256+018 (PKS J1259+0136), which is a known radio
variable source (Ofek et al. 2011, ApJ, 737, 45). The radio spectral index
(-0.59; Vollmer 2010, A&A, 511, 53) is consistent with optically thin
synchrotron emission (flux density S_�� proportional to ��^-0.6, where �� is
the frequency).

Burbidge & Hewitt (1992, Variability of Blazars, 4) list "1E 1256+018" as a
BL Lac and is likely to be the same source as PKS 1256+018. However, the
nearest Second Einstein catalog source is 4.7' away, and has a positional
error of 0.7'.

Given this potential radio source associated with a BL Lac and an
astrophysical neutrino, we strongly suggest multi-wavelength observations
of SDSS J125908.28+013605.3.

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

At the time of the neutrino candidate IceCube-201115A
(GCN 28889
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 ), Fermi was passing through the South Atlantic
Anomaly from 10.4 minutes prior until 17.6 minutes after the trigger
time; therefore the GBM detectors were disabled.

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 
IC201115A neutrino event (GCN 28889
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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 2020-10-15 at 02:07:26.21 
UT (T0) with J2000 position RA = 195.12 (+1.27, -1.49) deg, Decl. = 1.38 
(+1.30, -1.11) deg (90% PSF containment). No cataloged >100 MeV 
gamma-ray source is located within the 90% IC201115A localization region.

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 IC201115A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC201115A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 5.6e-10 ph cm^-2 s^-1 for 
~12-years (2008-08-04 to 2020-11-15 UTC), and < 8.9e-9 (< 5.9e-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 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.

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-201115A (GCN 28889
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  <https://gcn.gsfc.nasa.gov/gcn3/28889.gcn3
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 >). The reconstructed origin was -7 degrees below the horizon for ANTARES.

No up-going muon neutrino candidate events were recorded within 90% error box of the IceCube event during a +/- 1h time-window centered on the IceCube event time, and over which the potential source remained visible all time. This leads to a preliminary 90% confidence level upper limit on the muon-neutrino fluence from a point source of 17.1 GeV.cm^-2 over the energy range 3.2 TeV - 3.5 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and 68.3 GeV.cm^-2 (640 GeV - 325 TeV) for an E^-2.5 spectrum. A search over an extended time window of +/- 1 day has also yielded no detection (49% visibility).
ANTARES <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.

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-201115A (GCN 28889
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 ).

At the time of the event (2020-11-15 02:07:26 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 99 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(6% of optimal) response of ISGRI, strongly suppressed (32% of
optimal) response of IBIS/Veto, and somewhat suppressed (64% of
optimal) response of SPI-ACS.

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

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 2.9e-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 ~2.5e-07 (7.3e-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: 7 likely background
excesses:

T-T0     | scale   | S/N | flux ( x 1e-06 erg/cm2/s)     | FAP    
-18.2    | 1.7     | 3.6 |     2.72 +/- 0.791  +/- 1.09   | 0.0584 
-1.35    | 0.25    | 3.2 |    0.624 +/- 0.207  +/- 0.25   | 0.0822 
8.22     | 0.2     | 4   |    0.873 +/- 0.233  +/- 0.351  | 0.129 
-239     | 1.85    | 3.7 |     2.79 +/- 0.759  +/- 1.12   | 0.601 
4.1      | 0.05    | 3.4 |     1.48 +/- 0.47   +/- 0.596  | 0.625 
5.92     | 0.1     | 3.3 |     1.03 +/- 0.33   +/- 0.413  | 0.634 
-113     | 0.9     | 3.5 |    0.372 +/- 0.109  +/- 0.149  | 0.915 

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

--

Hugo Ayala (Penn State) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 202011/15 02:07:26 UTC, the IceCube collaboration reported a
track-like very-high-energy event that has a high probability of
being an astrophysical neutrino, IceCube-201115A. Location is at
RA: 195.12 (+1.27/-1.49 deg  90% PSF containment) J2000
Dec: 1.38 (+1.30/-1.11 deg 90% PSF containment) J2000
(GCN circular 28889
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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 June 2019. We searched
inside the reported IceCube error region.
The most significant location, with p-value 1.25e-2 (3.48e-1 post-trials),
is at RA 194.920 deg, Dec +2.28 deg (��0.35 deg 68% containment) J2000.
We set a time-integrated 95% CL  upper limit on gamma rays at the
maximum position of:

E^2 dN/dE = 2.52e-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 2020/11/13 18:35:15 UTC and ended
2020/11/15 18:52:30 UTC.
The most significant location, with p-value 8.42e-3  (2.49e-1 post-trials),
is at RA 194.5 deg, Dec +0.26 deg (��0.32 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:

E^2 dN/dE = 1.33e-11 (E/TeV)^-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.

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-201115A (https://gcn.gsfc.nasa.gov/gcn3/28889.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2020-11-14 02:07:26.21 UTC to 2020-11-16 02:07:26.21 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-201115A. We find that these data are consistent with atmospheric background expectations, with a p-value of 0.07. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/dE = 3.7 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 5 PeV.

A subsequent search was performed to include the month of data prior to the alert event (2020-10-16 02:07:26.21 UTC to 2020-11-16 02:07:26.21 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
3.7 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>.