IceCube-201120A

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

On 20/11/20 at 09:44:40.56 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 0.295 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/134715_65785778.amon), more 
sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 20/11/20
Time: 09:44:40.56  UT
RA: 307.53 (+ 5.34 - 5.59 deg 90% PSF containment) J2000
Dec: 40.77 (+ 4.97 - 2.80 deg 90% PSF containment) J2000 

Due to the topology of this event, with a short distance traversed through the detector, the updated angular uncertainty is significantly larger than average error contours.  

We encourage follow-up by ground and space-based instruments to help identify a possible 
astrophysical source for the candidate neutrino.

There are several Fermi-LAT 4FGL sources inside the 90% localization region. The closest source is 4FGL J2028.6+4110e (Cygnus Cocoon) located at RA 307.17 deg and Dec 41.17 deg (J2000), at a distance of 0.484 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

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM team:

For the IceCube high-energy neutrino candidate event IceCube-201120A
(GCN 28927
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 ), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 307.53 (+5.34 -5.59 deg 90% PSF containment) J2000
Dec: 40.77 (+4.97 -2.80 deg 90% PSF containment) J2000

A Fermi-GBM onboard GRB trigger (627557935 / 201120402) occurred
around 6 minutes prior to the event time of the neutrino candidate.
However, we estimate that the spatial localization of this trigger
only has a 20% chance of association with the neutrino event. It is
likely unrelated. 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-201120A.

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

Timescale   Soft     Normal   Hard
-------------------------------------------
0.128 s:    10.      16.      29.
1.024 s:    2.1      3.7      7.3
8.192 s:    0.7      0.9      2.0

These results are preliminary.

D. B. Fox (PSU), A. Keivani (Columbia U.), J.P. Osborne (U. Leicester), F. Krauss (PSU), T. Gregoire (PSU), P.A. Evans (U. Leicester), J.A. Kennea (PSU) and H. A. Ayala Solares (PSU),  D.F. Cowen (PSU) and J. DeLaunay (PSU) report:

Swift observed the location of 4FGL J2028.6+4110e, the Fermi-LAT source closest to the location of IceCube 201120A (IceCube Collaboration; GCN Circ. 28927
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 ) for 3.5 ks between 17:10UT and 20:05UT on 2020 November 20. No sources are found in the XRT field of view. 

The background level varies significantly across the field of view, due to the presence of stray light arising from the out-of-field bright source 2SXPS J203225.7+405727 (=1RXH J203225.7+405727) which is approximately 45��� away from the XRT boresight. This stray light was modelled automatically when searching for sources, using the new online source detection tool within https://www.swift.ac.uk/user_objects.

Taking this variation into account the 3-sigma upper limit in the XRT field of view varies between 3.7 x 10^-3 ct/sec and 4.5x10^-3 ct/sec. Assuming a power-law spectral photon index of 1.7, and Galactic absorption (1.46 x 10^22 cm^-2; Willingale et al, 2013), this corresponds to an observed 0.3-10 keV flux of 2.7 x 10^-13 erg cm^-2 s^-1 to 3.3 x 10^-13 erg cm^-2 s^-1

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-201120A (GCN 28927
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 ).

At the time of the event (2020-11-20 09:44:40 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 129 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (3.8% of optimal) response of ISGRI, strongly suppressed
(32% of optimal) response of IBIS/Veto, and somewhat suppressed (51%
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]), 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 3.5e-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 ~3.2e-07 (8.7e-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: 2 possibly associated
excesses:

T-T0  | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP
-3.01 | 0.55  | 4.2 | 0.703 +/- 0.176 +/- 0.319 | 0.0147
-13.5 | 4     | 3.6 | 2.28 +/- 0.65 +/- 1.03    | 0.0197
     
10 likely background excesses:

T-T0  | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP
7.19  | 0.55  | 3.4 | 0.582 +/- 0.176 +/- 0.264 | 0.105
164   | 0.05  | 9.5 | 5.38 +/- 0.618 +/- 2.44   | 0.443
-229  | 8     | 3.1 | 1.16 +/- 0.459 +/- 0.527  | 0.581
43.7  | 0.05  | 5.3 | 2.9 +/- 0.601 +/- 1.31    | 0.584
-35.4 | 0.35  | 3.6 | 0.748 +/- 0.221 +/- 0.34  | 0.601
50.4  | 0.45  | 3.6 | 0.666 +/- 0.195 +/- 0.302 | 0.706
271   | 0.95  | 4.2 | 0.525 +/- 0.134 +/- 0.238 | 0.758
6.29  | 0.15  | 3.1 | 0.959 +/- 0.339 +/- 0.436 | 0.837
-46.7 | 0.5   | 3.4 | 0.584 +/- 0.185 +/- 0.265 | 0.892
63.2  | 0.65  | 3.4 | 0.514 +/- 0.162 +/- 0.234 | 0.946

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) 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 
IC201120A neutrino event (GCN 28927
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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 2020-11-20 at 09:44:40.56 
UT (T0) with J2000 position RA = 307.53 (+5.34 , -5.59) deg, Decl. = 
40.77 (+4.97, -2.80) deg (90% PSF containment). The 90% neutrino 
localization consists in approximately a 85 sqdeg region centered on the 
Galactic plane. Fourteen cataloged gamma-ray (>100 MeV) sources are 
located within the 90% IC201120A localization region (4FGL, The 
Fermi-LAT collaboration 2020, ApJS, 247, 33).

In a preliminary analysis of the LAT data over the timescales of 1-day 
prior to T0, one of these objects is significantly detected (> 5 sigma). 
This is 4FGL J2021.5+4026, associated with the pulsar PSR J2021+4026. 
The estimated daily flux is consistent with the one reported in the 4FGL 
catalog.

Based on a preliminary analysis of the LAT data over the timescales of 
1-month prior to T0, five of these objects are significantly detected (> 
5 sigma). These are 4FGL J2028.6+4110e (associated with the Star Forming 
Region Cygnus-X), 4FGL J2038.4+4212 (associated with the Cygnus Cocoon 
region) and the pulsars 4FGL J2021.5+4026, 4FGL J2030.9+4416 and 4FGL 
J2032.2+4127. The flux values of these objects are consistent with the 
average flux reported in the 4FGL catalog.

We searched for intermediate (day to month) timescale emission from a 
new gamma-ray transient source. Preliminary analysis indicates no 
significant (> 5 sigma) new excess emission (> 100 MeV) at the IC201120A 
best-fit position. Assuming a power-law spectrum (photon index = 2.0 
fixed) for a point source at the IC201120A best-fit position, the >100 
MeV flux upper limit (95% confidence) is < 4.6e-8 (< 3.4e-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.

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-201120A (https://gcn.gsfc.nasa.gov/gcn3/28927.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2020-11-19 09:44:40.56 UTC to 2020-11-21 09:44:40.56 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-201120A. We find that these data are consistent with 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 = 5.8 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 500 TeV.

A subsequent search was performed to include the month of data prior to the alert event (2020-10-21 09:44:40.56 UTC to 2020-11-21 09:44:40.56 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
6.7 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>.

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

On 2020/11/20 09:44:40 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-201120A. Location is at
RA: 307.53 (+ 5.34 - 5.59 deg 90% PSF containment) J2000
Dec: 40.77 (+ 4.97 - 2.80 deg 90% PSF containment) J2000
(GCN circular 28927
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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.

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. This region corresponds to the
Cygnus Cocoon region.
The best position of the IceCube event is close to the HAWC catalog source
3HWC J2031+415 RA 307.93, Dec: 41.51 (��0.06 deg 68% containment) J2000
Significance: 23.56
Flux: 30.7e-15 +1.3e-15 -1.4e-15 [Tev cm2 s]^-1 at 7 TeV
Index: -2.36 �� 0.04

Other 3HWC sources in the region:
3HWC J2020+403 RA 305.16 Dec 40.37 (��0.09 deg 68% containment) J2000
Significance: 9.69
Flux: 11.4e-15 ��1.2e-15  [Tev cm2 s]^-1 at 7 TeV
Index: -3.11 �� 0.07

3HWC J2022+431 RA 305.522 Dec: 43.158 (��0.10 deg 68% containment) J2000
Significance: 28.95
Flux: 6.0e-15 ��1.1e-15  [Tev cm2 s]^-1 at 7 TeV
Index: -2.34 �� 0.12

3HWC J2043+443 RA 310.89 Dec: 44.30 (��0.24 deg 68% containment) J2000
Significance: 5.35
 Flux: 9.7e-15 +2.1e-15 -2.2e-15 [Tev cm2 s]^-1 at 7 TeV
Index: -2.33 +0.14 -0.15

Search for a transient source. We assume a power-law spectrum with an index
of -2.3
with pivot energy of 1 TeV.

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 2020/11/20 01:52:08 UTC and ended
2020/11/22 02:06:34 UTC.

We found 4 hotspots in the region of the IceCube uncertainty.
3 of them are consistent with 3HWC sources. One is not.

|  RA  | Dec | Unc. |p-value|Flux [TeV^-1 cm^-2 s^-1]|Nearby source|
|------|-----|-----|------|------------------------------|---------|
|305.2|40.0|0.4| 0.20 |7.9e-12 (+8.0e-12 -5.2e-12)|3HWC J2020+403|
|309.0|40.4|0.2| 0.25 |7.2e-12 (+8.3e-12 -5.1e-12)|None|
|305.1|43.0|0.3| 0.84 |4.5e-12 (+7.1e-12 -3.6e-12)|3HWC J2020+431|
|307.6|41.4|0.7| 0.91 |7.7e-12 (+9.1e-12 -5.8e-12)|3HWC J2031+415|

Position and uncertainty (68%) are in degrees.
P-values are post-trials. None of the hotspots is a significant detection,
nor we see any significant flux enhancements.

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.