IceCube-240721A
GCN Circular 36918
Subject
IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
Date
2024-07-21T20:11:48Z (10 months ago)
From
A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu>
Via
Web form
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
On 2024-07-21 at 16:17:25.8 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 1.376 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/139674_30853199.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:
Date: 2024-07-21
Time: 16:17:25.8 UT
RA: 354.99 (+1.08, -1.14 deg 90% PSF containment) J2000
Dec: 22.67 (+1.38, -1.14 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-DR4 or 3FHL catalog sources in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J2338.9+2124 at RA: 354.74 deg, Dec: 21.40 deg J2000 (1.29 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
GCN Circular 36921
Subject
Fermi-LAT gamma-ray observations of IceCube-240721A
Date
2024-07-22T13:01:53Z (10 months ago)
From
Leo Pfeiffer at University of Würzburg <pfeiffer.leo@gmail.com>
Via
Web form
L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), C. Bartolini (INFN Bari), S. Garrappa (Weizmann Institute of Science) and J. Sinapius (DESY) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC-240721A neutrino event (GCN 36918) 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 2024-07-21 16:17:25.8 UTC (T0) with J2000 position RA = 354.99 (+1.08, -1.14) deg, Decl. = 22.67 (+1.38, -1.14) deg 90% PSF containment.
No cataloged gamma-ray sources are found within the 90% IC-240721A localization error (Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546).
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 IC-240721A 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 <2.01e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / 2024-07-22 UTC), <1.06e-08(<8.26e-08) 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 person is L. Pfeiffer (leonard.pfeiffer at stud-mail.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 36927
Subject
IceCube-240721A: Upper limits from a search for additional neutrino events in IceCube
Date
2024-07-23T19:09:00Z (10 months ago)
From
Jessie Thwaites at IceCube/U Wisc-Madison <thwaites@wisc.edu>
Via
Web form
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-240721A (https://gcn.nasa.gov/circulars/36918) in a time range of 1000 seconds centered on the alert event time (2024-07-21 16:09:05.76 UTC to 2024-07-21 16:25:45.76 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-240721A. 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-240721A 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 8e+04 GeV.
A subsequent search was performed including 2 days of data centered on the alert event time (2024-07-20 16:17:25.76 UTC to 2024-07-22 16:17:25.76 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-240721A 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.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular 36929
Subject
IceCube-240721A: Two candidates from the Zwicky Transient Facility
Date
2024-07-24T07:02:46Z (10 months ago)
From
Jannis Necker at DESY <jannis.necker@desy.de>
Via
Web form
Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY), Robert Stein (Caltech), Simeon Reusch (DESY), 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. 2023), we observed the localization region of the neutrino event IceCube-240721A (Zegarelli et. al, GCN 36918) 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 2024-07-22 07:09 UTC, approximately 14.9 hours after event time. We covered 100.0% (5.1 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 candidates by our pipeline, all lying within the 90.0% localization of the skymap.
+--------------------------------------------------------------------------------+
| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr |
+--------------------------------------------------------------------------------+
| ZTF23aaslxmh | AT2023qqp | 354.7409079 | +23.6986176 | g | 20.34 | 0.16 |
| ZTF24aaugpvz | AT2024pge | 355.2587572 | +23.8561717 | g | 20.11 | 0.13 |
+--------------------------------------------------------------------------------+
AT2023qqp was first detected on 2023-06-21. It appears to be nuclear and is slowly rising ever since its first detection. We detect a 0.5 mag flare around the time of neutrino arrival with a similar flare happening roughly 80 days before. This could indicate AGN activity, although the WISE color of the host W1-W2=-0.07 is not AGN-like (Stern et al. 2012).
AT2024pge was first detected on 2024-07-10, about ten days before the neutrino arrival. The rise time of the lightcurve and the offset of ~ 1" to the host suggest a supernova origin.
We will resume our regular follow-up observation schedule to obtain more observations of these objects.
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 nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ).
GCN Circular 37195
Subject
IceCube-240721A: AT2023qqp and AT2024pge likely unrelated
Date
2024-08-16T20:49:15Z (9 months ago)
From
Jannis Necker at DESY <jannis.necker@desy.de>
Via
Web form
Jannis Necker (DESY), Robert Stein (Caltech), Jesper Sollerman (OKC), Tomas Ahumada (Caltech), Christoffer Fremling (Caltech), Anna Franckowiak (RUB) and Mansi Kasliwal (Caltech) report:
AT2023qqp/ZTF23aaslxmh and AT2024pge/ZTF24aaugpvz were first reported by ZTF (Weimann et al., GCN 36929) as potential counterparts to the high-energy neutrino IceCube-240808A (Zegarelli et. al, GCN 36918), as part of the broader ZTF neutrino follow-up program (Stein et al. 2023).
We obtained spectroscopic observations of AT2024pge/ZTF24aaugpvz at the P200 Hale Telescope with the Double Spectrograph (PI:Fremling) and at Gemini North with GMOS (PI: Stein). Observations took place on 07/24/24 and 07/31/24, respectively. The spectrum shows broad balmer lines at a redshift of z=0.096 which suggests a supernova Type II with a peak g-band magnitude of M=-18.5. This interpretation aligns with the offset from the host center. However, there are no indications for narrow emission lines shich would indicate CSM interaction, so we consider the transient unrelated to the neutrino.
AT2023qqp/ZTF23aaslxmh was observed at Gemini North with GMOS (PI: Stein) on 07/31/24. The spectrum indicates a redshift of z=0.64 which puts the peak g-band magnitude at M=-23.4. There are no supernova-like features and based on the past activity over more than 400 days, AT2023qqp is likely due to AGN activity. The short term flare of around one day with a magnitude increase of 0.5 occuring at neutrino arrival was likely happening by chance.
We conclude that both transient are likely unrelated to IceCube-240721A.
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.
Based on observations obtained at the international Gemini Observatory, a program of NSF NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the U.S. National Science Foundation on behalf of the Gemini Observatory partnership: the U.S. National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).
This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance.