IceCube-191001A

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

On 19/10/01 at 20:09:18.17 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 0.86 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/133119_22683750.amon <https://gcn.gsfc.nasa.gov/notices_amon_g_b/133119_22683750.amon>), more 
sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 19/10/01
Time: 20:09:18.17 UT
RA: 314.08 (+6.56 -2.26 deg 90% PSF containment) J2000
Dec: 12.94 (+1.50 -1.47 deg 90% PSF containment) J2000

Given that the track is partially obscured by a natural dust layer in the ice, the 90% uncertainty region reported by the reconstruction algorithms is larger than average error contours. 

There are two Fermi 4FGL catalogue sources within the 90% contour. The nearest is 4FGL J2052.7+1218, located 1.1 degrees away at the edge of the 50% localization region. One additional source, 4FGL J2115.2+1218, is also located within the 90% contour at a distance of 4.8 degrees from the best fit.

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

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), Diego Gotz (CEA, Saclay)
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-191001A (GCN 25913
Loading...
 
 ).

At the time of the event (2019-10-01 20:09:18 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 111 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (3% of optimal) response of ISGRI, strongly suppressed (33%
of optimal) response of IBIS/Veto, and somewhat suppressed (54% of
optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

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 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 ~2.4e-07 (7.5e-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:

scale | T | S/N | flux ( x 1e-06 erg/cm2/s) | FAP  
1.25 | 8.35 | 3.4 | 3.03 +/- 0.825 +/- 0.828 | 0.0615 
3.75 | 240 | 4.7 | 2.37 +/- 0.476 +/- 0.647 | 0.115 
2.5 | 152 | 4 | 2.37 +/- 0.583 +/- 0.646 | 0.194 
2.7 | 108 | 3.2 | 1.8 +/- 0.56 +/- 0.492 | 0.522 
0.8 | 71.1 | 3.6 | 0.386 +/- 0.103 +/- 0.105 | 0.524 
2.4 | -168 | 3.3 | 2.09 +/- 0.594 +/- 0.569 | 0.7  
0.15 | 13.5 | 3.3 | 0.815 +/- 0.24 +/- 0.222 | 0.997 

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

A. Goldstein (USRA) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event 191001A (GCN 25913
Loading...
 
 ),
the reported position:

RA: 314.08 (+6.56 -2.26 deg 90% PSF containment)
Dec: 12.94 (+1.50 -1.47 deg 90% PSF containment)

was occulted by the Earth for Fermi-GBM from approximately 27 minutes prior
until 2 minutes after event time. Therefore, the GBM observations are not
constraining for prompt gamma-ray emission.

Robert Stein (DESY), Anna Franckowiak (DESY), Jannis Necker (DESY), Suvi Gezari (UMd), Sjoert van Velzen (UMd/NYU) report,
On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We observed the localization region of the neutrino event IceCube-191001A (Stein et. al, GCN 25913
Loading...
 
 ) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started obtaining target-of-opportunity observations in the g-band and r-band beginning at 2019-10-02T03:32:47.200, approximately 7.4 hours after event time. Excluding chip gaps, we covered the entire reported localisation region of the neutrino. Each exposure was 300s with a typical depth of 21.0 mag.

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) 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 to remove bogus subtractions (Mahabal et al. 2019). We are left with 10 high-significance transient candidates by our pipeline, and highlight four that are particularly interesting. 

+-------------------------------------------------------------------------------+
| ZTF Name     | IAU Name  | RA (deg)   | DEC (deg)   | Filter | Mag   | MagErr |
+-------------------------------------------------------------------------------+
| ZTF19aapreis | AT2019dsg
Loading...
 
  | 314.2623825| +14.2045431 | g      | 19.79 | 0.05   | 
| ZTF19abzkexb | AT2019qhl
Loading...
 
  | 320.5502682| +11.5600861 | g      | 19.13 | 0.03   | 
| ZTF19acbpqfn | AT2019rsj
Loading...
 
  | 316.0854222| +12.9171434 | g      | 21.00 | 0.14   | 
| ZTF19acbxbjq | AT2019rsk
Loading...
 
  | 318.6378536| +14.1469459 | g      | 20.32 | 0.08   | 
+-------------------------------------------------------------------------------+

ZTF19aapreis is a Tidal Disruption Event approximately 150 days post peak, previously reported in ATEL #12752 and ATEL #12777. We note that this source is also one of a handful of radio-detected TDEs, as reported in ATEL #12798, making it a particularly interesting candidate for high-energy neutrino emission. 

Additional Swift TOO observations as well as VLA observations have been submitted for ZTF19aapreis. We strongly encourage further multi-wavelength observations of this source.

In addition, three unclassified transients were found within the localisation region. ZTF19abzkexb, already reported to the TNS as AT2019qhl
Loading...
 
 , was first detected 14 days ago and is clearly offset from its host. It shows a rising light curve resembling a young supernova. ZTF19acbpqfn also shows a lightcurve consistent with a supernova that is a few days post peak. It is offset from its host. ZTF19acbxbjq, first detected four days ago, shows a rising light curve. It has a position consistent with the center of the host galaxy.

We encourage spectroscopic and photometric observations to discern the nature of the three unclassified objects listed above.

Additional target-of-opportunity observations of the localisation region of IceCube 191001A will continue, in addition to serendipitous observations as part of the regular survey operations.

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; IIT-B, 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 and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

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 
IC191001A neutrino event (GCN�25913) �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 2019-10-01��20:09:18.17�UTC 
(T0) with J2000 position RA =�314.08 (+6.56, -2.26) deg, Decl. =�12.94 
(+1.50, -1.47) deg 90% PSF containment. Two cataloged gamma-ray sources 
(The Fermi-LAT collaboration, 2019, arXiv:1902.10045
Loading...
 
 )�are found within 
the 90% localization error of IC191001A. These are�the millisecond 
pulsar 4FGL�J2052.7+1218 (a.k.a.�PSR J2052+1218)�and the blazar 
candidate of uncertain type 4FGL J2115.2+1218 (a.k.a. NVSS 
J211522+121802), at a distance of 1.1 deg and�4.7 deg�from the best 
fit,�respectively.

We searched for the existence of intermediate (days to years) timescale 
emission from a new gamma-ray transient source.�Preliminary analysis 
indicates no significant (>5sigma) new excess emission (> 100 MeV) 
within the�IC191001A�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 < 
3.7e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2019-10-02 UTC), < 
2e-8 (< 2.9e-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 persons 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.

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

On 2019/10/01 at 20:09:18.17 UTC, the IceCube collaboration detected a
track-like
event with a high probability of being of astrophysical origin named
IceCube-1901001A.
The revised position is  RA= 314.08 deg and Dec= 12.94 deg, J2000 (GCN
circular 25913
Loading...
 
 ).
We have performed a search in our archival data for a steady source as
well as a transient source. We assume a power-law spectrum with a spectral
index of -2.3.
We use this spectrum for both analyses.

* Search for a steady source: Archival data from November 2014 to May
2018 is used.
We searched inside the uncertainty region reported by IceCube in the
circular (8.82 deg x 2.97 deg).
The highest significance found is 4.03 sigmas, at RA= 313.46 deg, Dec=
14.48 deg (J2000).
Note that there are at least 133 trials in this search, so the post-trials
significance is consistent with a non-detection.
We set a 95% CL time-integrated upper limit on the gamma-ray flux of E^2
dN/dE = 2.3e-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 on the GCN we report the combined result for the
transit before and
after the time of the IceCube event. We obtain the following results:
Data acquisition started on 2019/09/30 05:46:52 UTC and ended 2019/10/02
06:03:29 UTC.
The most significant location, with a pre-trials value of 2.55 sigma,  is
at RA= 313.84 deg, Dec= 12.71 deg (J2000).
We set a time-integrated 95% CL upper limit on the gamma-ray flux at the
position
of maximum signficance of: E^2 dN/dE = 3.51e-13 (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.

A. Biland (ETH Zurich) reports on behalf of the FACT Collaboration:

On Tue 01 Oct 19 20:09:48 UTC, the IceCube collaboration reported the
detection of a high-energy neutrino (run number 133119, event number
22683750).

FACT observed the position of the neutrino for a total of 5.13
hours on Oct 1st and Oct 2nd. The automatic quick-look analysis does
not show any signal from the observed position. Preliminary results can
be found at
https://fact-project.org/monitoring/index.php?y=2019&m=10&d=02&source=3748&timebin=12&plot=week
https://fact-project.org/monitoring/index.php?y=2019&m=10&d=02&source=3748&timebin=3&plot=night
https://fact-project.org/monitoring/index.php?y=2019&m=10&d=01&source=3748&timebin=3&plot=night

 From the results of the quick-look analysis, an upper limit of 24% of
the flux of the Crab Nebula at TeV energies was determined with a
confidence level of 99%.

Contact person: Daniela Dorner (dorner@astro.uni-wuerzburg.de)

The First G-APD Cherenkov Telescope (FACT) is an imaging air Cherenkov
telescope monitoring blazars at TeV energies. It is located in the
Observatorio del Roque de los Muchachos on the Canary Island La Palma.

[GCN OPS_NOTE(05oct19): "Title:" was removed from the SUBJECT:-line.]