IceCube-220907A
GCN Circular 32573
Subject
IceCube-220907A: Classification of AT2022oyn as a Type Ia supernova
Date
2022-09-22T13:49:51Z (3 years ago)
From
Robert Stein at Caltech <rdstein@caltech.edu>
Robert Stein (Caltech), Jannis Necker, Simeon Reusch (DESY), Viraj Karambelkar (Caltech), Sven Weiman (Ruhr University Bochum), Mansi Kasliwal (Caltech) and Anna Franckowiak (DESY/Ruhr University Bochum) report:
We observed neutrino IC220907A (Lincetto et al., GCN 32523) with the Zwicky Transient Facility (Stein et al., GCN 32536) as part of our ZTF neutrino follow-up program (Stein et al. 2022). As part of these observations, we reported the transient ZTF22aatwsqt/AT2022oyn as a possible optical counterpart.
We undertook spectroscopic observations of AT2022oyn with the Low Resolution Imaging Spectrometer (LRIS, Oke et al. 95) at the Keck I Observatory, as part of a program to classify possible electromagnetic counterparts to neutrinos (C271, PI: Stein). Using SNID (Blondin et al. 2007), we classify AT2022oyn as a type Ia supernova at redshift z=0.135 (see https://www.wis-tns.org/object/2022oyn for the full spectrum), approximately 45 days post peak. Given that type Ia supernovae are not predicted to emit high-energy neutrinos, we therefore exclude AT2022oyn as a candidate counterpart to IC220907A.
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 32560
Subject
IceCube-220907A: No significant detection in HAWC
Date
2022-09-16T07:41:24Z (3 years ago)
From
Woo-Hyeon Heo at U of Seoul <gjdngus9809@gmail.com>
Woo-Hyeon Heo, Hugo Ayala (UOS, PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):
On 2022-09-07 6:46:47. UTC, the IceCube collaboration reported a
track-like very-high-energy event that has a high probability of
being an astrophysical neutrino, IceCube-220907A. Location is at
RA: 224.81 (+2.07/-1.95 deg 90% PSF containment) J2000
Dec: +44.70 (+0.94/-1.06 deg 90% PSF containment) J2000
(GCN circular 32523).
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 3.26e-03 (1.25e-01 post-trials),
is at RA 223.26 deg, Dec +45.09 deg (+/-0.18 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 = 4.62e-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 2022/09/06 01:18:41 UTC and ended
2022/09/08 01:20:57 UTC.
The most significant location, with p-value 2.87e-02 (6.97e-01 post-trials),
is at RA 225.61 deg, Dec +44.70 deg (+/-0.23 deg 68% containment) J2000.
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:
E^2 dN/dE = 9.32e-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.
GCN Circular 32538
Subject
IceCube-220907A: Upper limits from a search for additional neutrino events in IceCube
Date
2022-09-08T21:15:26Z (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-220907A (https://gcn.gsfc.nasa.gov/gcn3/32523.gcn3) in a time range of 1000 seconds centered on the alert event time (2022-09-07 06:38:27.516 UTC to 2022-09-07 06:55:07.516 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-220907A. 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-220907A is 1.5e-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 5e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2022-09-06 06:46:47.516 UTC to 2022-09-08 06:46:47.516 UTC). In this case, we report a p-value of 1.00, 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-220907A is 1.8e-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 32536
Subject
IceCube-220907A: One Candidate Counterpart from the Zwicky Transient Facility
Date
2022-09-08T20:30:33Z (3 years ago)
From
Robert Stein at Caltech <rdstein@caltech.edu>
Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Simeon Reusch, Jannis Necker (DESY), Anna Franckowiak (DESY/Ruhr University Bochum) and Michael Coughlin (UMN) 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-220907A (Lincetto et al., GCN 32523) 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 2022-09-08 03:58 UTC, approximately 21.2 hours after event time. We covered 75% (5.4 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 |
+--------------------------------------------------------------------------------+
| ZTF22aatwsqt | AT2022oyn | 224.4694373 | +44.8892302 | r | 20.83 | 0.19 |
+--------------------------------------------------------------------------------+
ZTF22aatwsqt/AT2022oyn is a potential supernova 40 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 32528
Subject
Fermi-LAT Gamma-ray Observations of IceCube-220907A
Date
2022-09-07T21:42:57Z (3 years ago)
From
Sara Buson at GSFC/Fermi <sara.buson@gmail.com>
J. Sinapius (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg), S. Garrappa (DESY-Zeuthen) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the IceCube-220907A high-energy neutrino event (GCN 32523) 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 2022-09-07 at 06:46:47.52 UT (T0) with J2000 position RA = 224.81 (+2.07, -1.95) deg, Decl. = +44.70 (+0.94 , -1.06) deg (90% PSF containment). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC220907A localization region at a distance of roughly 1.38 deg (4FGL-DR3; The Fermi-LAT collaboration 2022, ApJS, 260, 53). This is the unassociated gamma-ray source 4FGL J1504.6+4343. Based on a preliminary analysis of the LAT data over the timescales of 1-day and 1-month prior to T0, this object is 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 IC220907A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC220907A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.5e-10 ph cm^-2 s^-1 for ~14-years (2008-08-04 to 2022-09-07 UTC), and < 1.1e-8 (< 4.7e-8) 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 J. Sinapius (jonas.sinapius at desy.de), 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 32523
Subject
IceCube-220907A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2022-09-07T12:26:59Z (3 years ago)
From
Dr. Massimiliano Lincetto at Ruhr-Universitaet Bochum <lincetto@astro.rub.de>
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2022-09-07 at 06:46:47.52 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 0.46 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/137019_70165712.amon),
more��sophisticated reconstruction algorithms have been applied offline,
with the direction refined to:
Date: 2022-09-07
Time: 06:46:47.52 UT
RA: 224.81 (+2.07 / -1.95 deg 90% PSF containment) J2000
Dec: +44.70 (+0.94 / -1.06 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
J1504.6+4343 at RA: 226.16, Dec: 43.72 deg (1.38 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