IceCube-230707A

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

On 23-07-07 at 16:58:50.03 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 0.4443 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/138125_11333473.amon), more
sophisticated reconstruction algorithms have been applied offline, with
the direction refined to:

Date: 23-07-07
Time: 16:58:50.03 UT
RA: 269.03 (+0.88 / -0.76 deg  90% PSF containment) J2000
Dec: -1.94 (+0.53 / -0.54 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-DR3 or 3FHL catalog sources in the 90%
uncertainty region. The nearest gamma-ray source in either catalog is
4FGL J1759.0-0107 at RA: 269.77 deg, Dec: -1.12 deg (1.10 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

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-230707A (https://gcn.nasa.gov/circulars/34163
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 ) in a time range of 1000 seconds centered on the alert event time (2023-07-07 16:50:30.030 UTC to 2023-07-07 17:07:10.030 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-230707A. 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-230707A 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 3e+02 GeV and 2e+05 GeV. 

A subsequent search was performed including 2 days of data centered on the alert event time (2023-07-06 16:58:50.030 UTC to 2023-07-08 16:58:50.030 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-230707A is 1.6e-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)

S. Garrappa (Weizmann Institute of Science), S. Buson (Univ. Wuerzburg), J. Sinapius (DESY) and C. Bartolini (INFN Bari) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the IC230707A  high-energy neutrino event (GCN 34163
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 ) 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 2023-07-07 at 16:58:50.03 UT (T0) with J2000 position RA = 269.03 (+0.88, -0.76) deg, Decl. = -1.94 (+0.53, -0.54) deg (90% PSF containment).  No cataloged gamma-ray (>100 MeV; The Fermi-LAT collaboration 2022, ApJS, 260, 53) sources are located within the 90% IC230707A  localization region.
We searched for intermediate (days to years) timescale emission from a new gamma-ray source. Preliminary analysis indicates no significant (> 5 sigma) new excess emission (> 100 MeV) at the IC230707A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC230707A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 6.8e-10 ph cm^-2 s^-1 for ~15-years (2008-08-04 to 2023-07-07 UTC), and < 5.2e-8 (< 3.2e-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 region will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa at weizmann.ac.il), J. Sinapius (jonas.sinapius at desy.de <http://desy.de/>) and S. Buson (sara.buson at uni-wuerzburg.de <http://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.

Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Simeon Reusch (DESY), Jannis Necker (DESY), Anna Franckowiak (DESY/Ruhr University Bochum) and Vishwajeet Swain (IITB) 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-230707A (Lincetto et. al, GCN 34163
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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 observations in the g- and r-band beginning at 2023-07-08 04:57 UTC, approximately 12.0 hours after event time. We covered 87.6% (1.4 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). 

No candidate counterparts were detected. 

Additional observations are planned as part of our standard neutrino follow-up procedure, and any candidates will be reported.

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 nuztf package (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf).

P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report,

Swift-XRT carried out 13 observations of the region of IceCube-230707A (Lincetto et al., GCN Circ 34163
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 ), from 59 ks to 78 ks after the neutrino trigger; the typical exposure time was 300 s per field.

We detected three uncatalogued X-ray objects, however all of these are classified as “poor” by the source detection algorithm (Evans et al., 2020) and are thus likely spurious. The typical 3-sigma upper limit is 0.05 ct/sec (0.3-10 keV) corresponding to ~2.1 x 10^-12 erg/cm^2/s.

The full results of the automated XRT analysis can be viewed online at: https://www.swift.ac.uk/neutrino/NEUTRINO_FIELD00040/


(Reference: Evans et al., 2020, ApJS, 247, 54)

W.Iwakiri (Chiba Univ.), M.Serino (AGU),  K. Gendreau, Z. Arzoumanian (NASA/GSFC):

We report the non-detection of MAXI/GSC of the neutrino event IceCube-230707A (Lincetto et al., GCN Circ 34163
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 ) and the upper limits of the X-ray flux of Swift J1753.5-0127 located in the error region of the neutrino event by NICER.
At 16:25:43 UT on 2023-07-07 (about 33 min before the event trigger)) and 17:58:40 UT on 2023-07-07 (about 60 min after the event trigger),  MAXI/GSC scanned the error region of the event. No significant excess emission was detected from the region. A typical 1-sigma averaged upper limit in one scan observation is 20 mCrab at 2-20 keV. 

We have also observed Swift J1753.5-0127, located in the 90% uncertainty region of IceCube-230707A, by NICER. Swift J1753.5-0127 is a candidate of a black hole in X-ray binary system, discovered in an outburst in 2005(ATel #546). The outburst lasted in 2017 (ATel #10562), and after that no significant activity has been reported. To search for any reactivity of Swift J1753.5-0127 associated with the high-energy neutrino signal, NICER observed the source from July 9th 19:34 UT to July 10th 02:01 UT with 3.9 ksec exposure. There was no significant X-ray signal. The estimated 3-sigma flux upper limit of Swift J1753.5-0127 in the 0.6-10 keV band is about 1.8 x 10^-12 erg/sec/cm^2 using an absorbed power-law model with photon index 1.7 and a column density nH of 2 x 10^21 cm^-2 (Plotkin et al., 2017). Assuming the distance of 8 kpc, the X-ray luminosity corresponds to 1.5 x 10^34 erg/s. The result indicates that Swift J1753.5-0127 is in quiescence.

NICER is a 0.2–12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA.

(Reference: Plotkin et al., 2017, ApJ, 848, 92)

Y. Urata, K.Y. Huang on behalf of a larger collaboration

We observed the field of IceCube-230707A (GCN Circ. 34163
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 ) using
SCUBA-2 attached to JCMT. The observations at 450 and 850 um were
conducted on 2023/07/08, 2023/07/14, 2023/07/24, 2023/07/25, and
2023/07/28. In the individual epochs, SCUBA-2 imaged the field
centered at RA 269.03, Dec -1.94 with 1.3 deg diameter. The rms of the
stacked map in 850um is 6 mJy. There was no source brighter than the
5-sigma limit.