IceCube-201007A

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

On 20/10/07 at 22:01:49.28 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 0.262 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/134577_31638233.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 20/10/07
Time:  22:01:49.28 UT
RA: 265.17 (+/- 0.52 deg  90% PSF containment) J2000
Dec: 5.34 ((+0.32, -0.23) 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 J1736.6+0628 at RA: 264.17 deg, Dec: 6.47 deg J2000 (1.51 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

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-201007A (GCN 28575
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 ).

At the time of the event (2020-10-07 22:01:49 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 30 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(19% of optimal) response of ISGRI, strongly suppressed (31% of
optimal) response of IBIS/Veto, and near-optimal (69% of optimal)
response of SPI-ACS.

The background within +/-300 seconds around the event was 
stable (excess variance 1.3). 

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 2.5e-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 ~2.2e-07 (7.6e-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: 1 possibly associated
excess:

T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP
-163 | 12.5 | 4 | 1.13 +/- 0.257 +/- 0.413 | 0.0422

2 likely background excesses:

T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP
-19.7 | 0.85 | 3.3 | 3.26 +/- 0.991 +/- 1.19 | 0.25
-59 | 0.9 | 3.2 | 2.96 +/- 0.962 +/- 1.08 | 0.913

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

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

Swift observed the field of IceCube 201007A (GCN Circ. 28575
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 ) between 00:18:13
2020 October 8 and 02:19:15 on 2020 October 8, collecting a total of 3.8 ks of
cleaned photon counting (PC) mode data. The observations used a 4-point tiling
pattern with a radius of ~0.3 degrees.

We found 3 X-ray sources, as detailed below. All of these are either known X-ray
sources, consistent with catalogued fluxes, or are unknown but with count rate
consistent with the previous non-detections. We therefore do not claim any of
them as the likely counterpart to IceCube 201007A.

The 3-sigma upper limit in the field was in the range 4-9 x 10^-3 ct/sec.

The detected sources were:
     
Source no:   1
RA (J2000):  265.15814 [degrees] = 17h 40m 37.95s
Dec (J2000): +5.30616 [degrees] = +05d 18' 22.2"
Error:       +5.5 [arcsec, 90% conf. radius]
Count rate (0.3-10 keV): 9.1 (+3.1, -2.5) x 10-3 ct s-1
Flux (0.3-10 keV):       3.9 (+1.3, -1.1) x 10-13 erg cm-2 s-1


Source no:   2
RA (J2000):  265.16388 [degrees] = 17h 40m 39.33s
Dec (J2000): +5.46461 [degrees] = +05d 27' 52.6"
Error:       +5.0 [arcsec, 90% conf. radius]
Count rate (0.3-10 keV): 3.8 (+2.1, -1.6) x 10-3 ct s-1
Flux (0.3-10 keV):       1.6 (+0.9, -0.7) x 10-13 erg cm-2 s-1

     
Source no:   3
RA (J2000):  265.06867 [degrees] = 17h 40m 16.48s
Dec (J2000): +5.64807 [degrees] = +05d 38' 53.1"
Error:       +5.8 [arcsec, 90% conf. radius]
Count rate (0.3-10 keV): 1.2 (+0.5, -0.4) x 10-2 ct s-1
Flux (0.3-10 keV):       5.3 (+2.1, -1.7) x 10-13 erg cm-2 s-1

S. Buson (Univ. of Wuerzburg) and S. Garrappa (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:

We report an analysis of observations of the vicinity of the high-energy IC201007A neutrino event (GCN 28575
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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 2020-10-07 at 22:01:49.28 UT (T0) with J2000 position RA = 265.17 (+/- 0.52) deg, Decl. = 5.34 (+0.32, -0.23) deg 90% PSF containment. No cataloged >100 MeV gamma-ray sources (The Fourth Fermi-LAT catalog; The Fermi-LAT collaboration 2020, ApJS, 247, 33) are located within the 90% IC201007A localization error. 

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 IC201007A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC201007A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 4.4e-10 ph cm^-2 s^-1 for ~12-years (2008-08-04 / 2020-10-07 UTC), < 2.1e-8 (< 1.6e-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.

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

For the IceCube high-energy neutrino candidate event IceCube-201007A
(GCN 28575
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 ), at the event time Fermi-GBM was observing the reported
neutrino location at:

RA: 265.17 (+/- 0.52 deg  90% PSF containment) J2000
Dec: 5.34 ((+0.32, -0.23) 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-201007A.

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:    5.7      8.4      14.
1.024 s:    1.7      3.3      4.7
8.192 s:    0.6      1.1      1.8

These results are preliminary.

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-201007A (https://gcn.gsfc.nasa.gov/gcn3/28575.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2020-10-06 22:01:49.28 UTC to 2020-10-08 22:01:49.28 UTC) during which IceCube was collecting good quality data. Excluding the
event that prompted the alert, zero additional track-like events are found in spatial coincidence
with the 90% containment region of IceCube-201007A. We accordingly derive a time-integrated muon-neutrino flux upper limit at the alert position of E^2 dN/ dE = 3.2 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 3 PeV.

A subsequent search was performed to include the month of data prior to the alert event (2020-09-07 22:01:49.28 UTC to 2020-10-08 22:01:49.28 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
3.9 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>.

Alberto Carrami��ana (INAOE) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 2020/10/07 22:01:49 UTC, the IceCube collaboration reported a 
track-like very-high-energy event  that has a high probability of 
being an astrophysical neutrino, IceCube-201007A. Location is at
RA: 265.17 (+/-0.52 deg  90% PSF containment) J2000
Dec: 5.34 (+0.32/-0.23 deg 90% PSF containment) J2000  
(GCN circular 28575
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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 1.29e-02 (3.70e-02 post-trials), 
is at RA 264.86 deg, Dec +5.23 deg (��0.15 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 = 2.57e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1

- Search for a transient source. 
The IceCube event was in our field of view at the time reported.

Data acquisition started on 2020/10/07 20:06:38 UTC and ended
2020/10/08 01:58:29 UTC.
The most significant location, with p-value 3.97e-01 (7.71e-01 post-trials),
is at RA 265.25 deg, Dec +5.34 deg (��0.27 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of 
maximum significance of:

E^2 dN/dE = 6.47e-12 (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.

Simeon Reusch (DESY), Sven Weimann (Ruhr University Bochum), Robert Stein (DESY) and Anna Franckowiak (DESY/Ruhr University Bochum) report,

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We serendipitously observed the localization region of the neutrino event IC-201007A (Santander et al. GCN 28575
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 ) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019), followed by dedicated Target-of-Opportunity observations. We observed in the g- and r-band beginning at 2020-10-08 02:52:02 UTC, approximately 4.8 hours after event time.  We covered 0.5 sq deg at least twice, corresponding to 87.5% of the reported localization region. This estimate accounts for chip gaps. Each serendipitous exposure was 30s with a typical depth of 20.5 mag, while ToO exposures were 300s with a typical depth of 21.0.

The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019; Stein et al. 2020) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We looked for high-significance transient candidates with our pipeline, lying within the 90.0% localization of the skymap.

No counterpart candidates were detected.

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.
ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341.
GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).
Alert database searches are done by AMPEL (Nordin et al. 2019).
Alert filtering is performed with the AMPEL Follow-up Pipeline (Stein et al. 2020).