IceCube-190922B

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

On 19/09/22 at 23:03:55.56 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 1.33 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/133092_52499868.amon), more  
sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 19/09/22
Time:  23:03:55.56 UT
RA: 5.76 (+ 1.19 - 1.37 deg  90% PSF containment) J2000
Dec: -1.57(+ 0.93 - 0.82 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 
J0022.0+0006 at RA: 5.52 deg, Dec: 0.11 deg (1.70 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

E. Burns (NASA/GSFC) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event 190922B (GCN 25806
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 ),
at the event time Fermi-GBM was observing the reported neutrino location at:

RA: 5.76 (+ 1.19 - 1.37 deg  90% PSF containment) J2000
Dec: -1.57(+ 0.93 - 0.82 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-190922B.

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:   2.9      5.2      11.
1.024 s:   0.8      1.5      2.7
8.192 s:   0.3      0.6      1.1

Antonio Martin-Carrillo (UCD), Francesca Onori, 
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
S. Mereghetti (INAF IASF-Milano, Italy)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

The INTEGRAL spacecraft has a highly elliptical orbit and the
instruments are not acquiring science data during perigee passage,
every 2.6 days to prevent radiation-induced damages. Unfortunately, at
the time of the IceCube event 190922B (2019-09-22 23:03:55, GCN 25806
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 ) 
the spacecraft was preparing to start the observations after the perigee passage
between the orbits number 2140 and 2141 and no scientific instrument
data are available between 2019-09-22T16:12:23 and
2019-09-23T01:40:00.

Robert Stein (DESY), Anna Franckowiak (DESY), Marek Kowalski (DESY), and Mansi Kasliwal (Caltech) 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-190922B (Blaufuss et. al, GCN 25806
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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). We started obtaining target-of-opportunity observations in the g-band and r-band beginning at 2019-09-23
07:03:11.900 UTC, approximately 8.0 hours after event time. Excluding  chip gaps, we covered the entire reported 90.0% probability region. 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 rejected stellar sources (Tachibana and Miller 2018) and moving objects, applied machine learning algorithms (Mahabal et al. 2019) and rejected candidates with a history of variability. We were left with one candidate identified by our pipeline in spatial coincidence with the neutrino localisation. 

+------------------------------------------------------------------------------+
| ZTF Name     | IAU Name  | RA (deg)   | DEC (deg)  | Filter | Mag   | MagErr |
+------------------------------------------------------------------------------+
| ZTF19abxtupj | AT2019pqh
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  | 6.617881   | -1.131493  | r      | 21.07 | 0.15   |
+------------------------------------------------------------------------------+

ZTF19abxtupj, previously reported to the TNS as AT2019pqh
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 , was first detected by ZTF on 2019-09-04. It appears to have peaked on 2019-09-07 and subsequently declined. Given the host spectroscopic redshift of z=0.1334 as reported to the TNS, the absolute magnitude at peak was approximately -18.7 mag in r-band, consistent with expectations for a supernova. The arrival of a neutrino roughly 16 days after peak is also consistent with a supernova CSM-interaction model for neutrino production.

We strongly encourage spectroscopic observations to discern the nature of ZTF19abxtupj/AT2019pqh
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 , and to rule out a classification as a type-Ia supernova.

Additional target-of-opportunity observations of the localisation region of IceCube 190922B 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; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.

On 2019-09-22 at  23:03:55.56 UTC, the IceCube collaboration detected a
track-like event with a moderate probability of being of astrophysical
origin, IceCube-190922B, at RA= 5.76  deg and Dec= -1.57 deg, J2000 (GCN
circular 25806
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 ). In HAWC's sky, the neutrino was outside of our field of
view.
We have performed a search in our archival data for a steady source as
well as a transient source.

* Search for a steady source in archival data from November 2014 to May
2018. Assuming a  power law with a spectral index of -2.3 we searched in a
2.74 x 1.86 degree rectangle around IceCube's reported location.

The highest significance, 0.63 sigma, was at RA= 6.37 deg, Dec= -1.49 deg
(J2000). Note that there are at least 5.5 trials in this search, so
post-trials significance is consistent with a non-detection. We set a
time-integrated upper limit 95% CL on the gamma-ray flux of E^2 dN/dE =
1.8e-13 (E/TeV)^-0.3 TeV cm^-2 s^-1.

*Search for a transient source: Since the events was not in our field of
view at the time reported on the GCN we did a search for the day before and
after as well. Looking in the same region of interest and spectrum we
obtain the following results:

Data acquisition on 2019-09-22 09:32:39 and ends 2019-09-23 09:28:43 (UTC),
1.16 sigma pre-trials (0.68 post trials), was at RA= 5.72 deg, Dec= -1.41
deg
(J2000). We set a time-integrated upper limit 95% CL on the gamma-ray flux
of: E^2 dN/dE = 1.5e-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-190922B (https://gcn.gsfc.nasa.gov/gcn3/25802.gcn3
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 ) in a time
range of 2 days centered on the alert event time (2019-09-21 23:03:55.56 UTC to 2019-09-23 23:03:55.56 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-190922B. We find that these data are well described by atmospheric background expectations, with a p-value of 1.0. Accordingly, these data would represent a time-integrated muon-neutrino flux upper limit at the alert position assuming an E^-2 spectrum (E^2 dN/dE) at the 90% CL of 3.3 x 10^-5 TeV cm^-2 for this observation period. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum are approximately between 1 TeV and 10 PeV.

A subsequent search was performed to include the previous month of data (2019-08-22 23:03:55.56 UTC to 2019-09-23 23:03:55.56 UTC). In this case, we report a p-value of 0.062,
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
 6.4 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>.

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

We report an analysis of observations of the vicinity of the high-energy 
IC190922B neutrino event (GCN�25806) �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 �2019-09-22 at�23:03:55.56 
UT (T0) with J2000 position RA =��5.76 (+1.19, -1.37) deg, Decl. =�-1.57 
(+0.93, -0.82) deg 90% PSF containment. No cataloged (>100 MeV) 
gamma-ray sources are found within the 90% IC190922B�localization error.

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�IC190922B 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 < 1e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 
2019-09-23 UTC), < 1e-7 (< 1e-8) ph cm^-2 s^-1 for a 1-day (1-month) 
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 Simone Garrappa (simone.garrappa atdesy.de 
<http://desy.de/>) and Sara 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.