IceCube-220822A
GCN Circular 32475
Subject
IceCube-220822A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2022-08-22T23:07:55Z (3 years ago)
From
Dr. Massimiliano Lincetto at Ruhr-Universitaet Bochum <lincetto@astro.rub.de>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2022-08-22 20:26:30.03 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 2.005 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/136973_28816141.amon) more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:
Date: 2022-08-22
Time: 20:26:30.03 UT
RA: 273.08 (+2.47, -2.50 deg 90% PSF containment) J2000
Dec: +21.54 (+0.94, -1.18 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.
Two gamma-ray sources listed in the 4FGL Fermi-LAT catalog are located
in the 90% containment region. The sources are 4FGL J1809.3+2042 and
4FGL J1819.1+2133 (3FHL J1819.2+2135), respectively located at 1.08 and
1.58 deg from the best fit 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
GCN Circular 32478
Subject
Fermi-LAT gamma-ray observations of IceCube-220822A and detection of a new gamma-ray source, Fermi J1810.1+2154
Date
2022-08-23T21:44:17Z (3 years ago)
From
Simone Garrappa at DESY <simone.garrappa@desy.de>
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
IC220822A neutrino event (GCN 32475) 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 2022-08-22 at 20:26:30.03��
UT (T0) with J2000 position RA = +273.08 (+2.47, -2.50) deg, Decl. =
21.54 (+0.94, -1.18) deg (90% PSF containment). Two cataloged gamma-ray
(>100 MeV) sources are located within the 90% IC220822A localization
region (4FGL-DR3; arXiv:2201.11184; The Fermi-LAT collaboration 2020,
ApJS, 247, 33). These are 4FGL J1809.3+2042 associated with the BL Lac
RX J1809.3+2041 and 4FGL J1819.1+2133, associated with the BL Lac MG2
J181902+2132 at 1.1 deg and 1.6 deg distance from the best-fit neutrino
localization, respectively. Based on a preliminary analysis of the LAT
data over the timescales of 1-day and 1-month prior to T0, these objects
are not significantly detected (> 5 sigma).
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 IC220822A
best-fit position. Assuming a power-law spectrum (photon index = 2.0
fixed) for a point source at the IC220822A best-fit position, the >100
MeV flux upper limit (95% confidence) is < 2e-10 ph cm^-2 s^-1 for
~14-years (2008-08-04 to 2022-08-22 UTC), and < 4.1e-9 (<8.8e-8) ph
cm^-2 s^-1 for a 1-month (1-day) integration time before T0.
Within the 90% confidence localization of the neutrino, 0.6 deg offset
from the best-fit IC220822A position, an excess of gamma rays, Fermi
J1810.1+2154, was detected in an analysis of the ~14-years integrated
LAT data (100 MeV - 1 TeV) prior to T0. This putative new source is
detected at a statistical significance ~4.5 sigma (calculated following
the prescription adopted in the The Fourth Fermi-LAT catalog, The
Fermi-LAT collaboration 2020, ApJS, 247, 33). Assuming a power-law
spectrum, the excess has best-fit localization of RA = 272.54 deg, Decl.
= 21.91 deg (95% containment radius = 0.14 deg) with best-fit spectral
parameters, flux = (6.6 +/- 4.7)e-10 ph cm^-2 s^-1, index = 1.9 +/-0.2.
In a preliminary analysis of the LAT data over one month prior to T0,
Fermi J1810.1+2154 is not significantly detected in the LAT data. All
values include the statistical uncertainty only.
Since Fermi normally operates in an all-sky scanning mode, regular
monitoring of this region 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.
GCN Circular 32480
Subject
IceCube-220822A: One Candidate Counterpart from the Zwicky Transient Facility
Date
2022-08-24T18:20:59Z (3 years ago)
From
Jannis Necker at DESY <jannis.necker@desy.de>
Jannis Necker (DESY), Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Simeon Reusch (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:
As part of the ZTF neutrino follow up program (Stein et al. 2022), we observed the localization region of the neutrino event IceCube-220822A (Lincetto et. al, GCN 32475) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2022-08-23 03:53 UTC, approximately 7.4 hours after event time. We covered 84.1% (8.2 sq deg) of the reported localization region. This estimate accounts for chip gaps. 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, Stein et al. 2021) 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 are left with the following high-significance transient candidate by our pipeline, lying within the 90.0% localization of the skymap:
+---------------------------------------------------------------------------------+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr |
+---------------------------------------------------------------------------------+
| ZTF22aarmiqk | AT2022saw | 272.3184212 | +22.1633981 | r | 21.71 | 0.20 |
+---------------------------------------------------------------------------------+
ZTF22aarmiqk/AT2022saw is a possible supernova 50 days post peak. Spectroscopic follow-up is encouraged to determine the type.
ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France.
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. 2021).
GCN Circular 32481
Subject
IceCube-220822A: Upper limits from a search for additional neutrino events in IceCube
Date
2022-08-25T13:03:29Z (3 years ago)
From
Abhishek Desai at ICECUBE/U of Wisconsin <desai25@wisc.edu>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-220822A (https://gcn.gsfc.nasa.gov/gcn3/32475.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-08-22 20:18:10.030 UTC to 2022-08-22 20:34:50.030 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-220822A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-220822A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 9e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2022-08-21 20:26:30.030 UTC to 2022-08-23 20:26:30.030 UTC). In this case, we report a p-value of 0.07, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-220822A is 1.7e-01 GeV cm^-2 in a 2 day time window.
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>.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 32498
Subject
IceCube-220822A: Classification of AT2022saw as a Type Ia supernova
Date
2022-08-28T19:58:48Z (3 years ago)
From
Robert Stein at Caltech <rdstein@caltech.edu>
Robert Stein, Zach Vanderbosch, Ilaria Caiazzo (Caltech), Jannis Necker, Simeon Reusch (DESY), Sven Weimann (Ruhr University Bochum), Mansi Kasliwal, Viraj Karambelkar (Caltech), Anna Franckowiak (DESY/Ruhr University Bochum) and Jesper Sollerman (Stockholm) report:
We observed neutrino IC220822A (Lincetto et. al, GCN 32475) with the Zwicky Transient Facility (Necker et al., GCN 32480) as part of our ZTF neutrino follow-up program (Stein et al. 2022). As part of these observations, we reported the transient ZTF22aarmiqk/AT2022saw as a possible optical counterpart.
We undertook spectroscopic observations of AT2022saw with the Low Resolution Imaging Spectrometer (LRIS, Oke et al. 95) at the Keck I Observatory. Using SNID (Blondin et al. 2007), we classify AT2022saw as a type Ia supernova at redshift z=0.14 (see https://www.wis-tns.org/object/2022saw for the full spectrum), approximately 50 days post peak. Given that type Ia supernovae are not predicted to emit high-energy neutrinos, we therefore exclude AT2022saw as a candidate counterpart to IC220822A.
The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
GCN Circular 32504
Subject
IceCube-220822A: No significant detection in HAWC
Date
2022-08-31T19:52:17Z (3 years ago)
From
Hugo Ayala at Pennsylvania State University <hgayala@psu.edu>
Hugo Ayala (PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):
On 2022-08-22 20:26:30.03 UTC, the IceCube collaboration reported a
track-like very-high-energy event that has a high probability of
being an astrophysical neutrino, IceCube-220822A. Location is at
RA: 273.08 (+2.47, -2.50 deg 90% PSF containment) J2000
Dec: +21.54 (+0.94, -1.18 deg 90% PSF containment) J2000
(GCN circular 32475).
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 7.62e-4 (0.04 post-trials),
is at RA 274.13 deg, Dec +20.38 deg (��0.27 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 = 1.33e-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 2022/08/21 05:42:32 UTC and ended
2022/08/23 05:55:16 UTC.
The most significant location, with p-value 3.7e-2 (0.87 post-trials),
is at RA 272.33 deg, Dec +22.51 deg (��0.24 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:
E^2 dN/dE = 5.88e-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.