IceCube-210730A

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

On 2021-07-30 at 22:12:40.629 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 2.542 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/135553_7213992.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2021-07-30
Time:  22:12:40.629 UT
RA: 105.73 (+2.00, -1.85 deg  90% PSF containment) J2000
Dec: 14.79 (+0.91, -0.86 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.

One gamma-ray source listed in the 4FGL Fermi-LAT catalog is located within the 90% uncertainty region of the best-fit candidate neutrino position. The source is 4FGL J0659.7+1416, 0.92 deg away 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

S. Garrappa (DESY-Zeuthen), S. Buson (Univ. of Wuerzburg) and R. de Menezes (Univ. of Sao Paulo, Univ. of Wuerzburg) on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC210730A neutrino event (GCN 30559
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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 2021-07-30 at 22:12:40.629 UT (T0) with J2000 position RA = 105.73 (+2.00, -1.85) deg, Decl. = 14.79 (+0.91, -0.86) deg (90% PSF containment). One cataloged gamma-ray (>100 MeV) source is located within the 90% IC210730A localization region (4FGL-DR2, The Fermi-LAT collaboration 2020, ApJS, 247, 33). This is 4FGL J0659.7+1416, associated with the pulsar PSR J0659+1414 (Jankowski et al. 2019 MNRAS, 484, 3691). Based on a preliminary analysis of the LAT data over the timescale 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 IC210730A best-fit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC210730A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 5.1e-10 ph cm^-2 s^-1 for ~13-years (2008-08-04 to 2021-07-30 UTC), and < 2.7e-8 (< 1.6e-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 source will continue. For these observations the Fermi-LAT contact persons are S. Garrappa (simone.garrappa 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.

V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
<https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration>

Using combination of INTEGRAL all-sky detectors (following [1]):
SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt
gamma-ray counterpart of unknown (GCN 30559
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 ).

At the time of the event (2021-07-30 22:12:40 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 97 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(6.6% of optimal) response of ISGRI, strongly suppressed (31% of
optimal) response of IBIS/Veto, and strongly suppressed (25% of
optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.2).

We have performed a search for any impulsive events in INTEGRAL SPI-
ACS (as described in [2]), IBIS, and IBIS/Veto data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 6.6e-07 erg/cm^2 (within the
50% probability containment region of the source localization) for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and
Ep=300 keV), the derived peak flux upper limit is ~7e-07 (1.8e-07)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

We report for completeness and in order of FAP, all excesses
identified in the search region. We find: 1 possibly associated
excess:

T-T0 | scale | S/N | flux ( x 1e-05 erg/cm2/s) | FAP
-0.0911 | 0.35 | 3.1 | 1.16 +/- 0.418 +/- 0.564 | 0.0203

5 likely background excesses:

T-T0 | scale | S/N | flux ( x 1e-05 erg/cm2/s) | FAP
25.3 | 5.55 | 3.3 | 0.318 +/- 0.104 +/- 0.155 | 0.0524
-72.6 | 4.5 | 3.9 | 0.433 +/- 0.116 +/- 0.211 | 0.0603
116 | 0.05 | 8.8 | 0.91 +/- 0.116 +/- 0.442 | 0.387
-145 | 1.6 | 3.5 | 0.637 +/- 0.195 +/- 0.31 | 0.593
205 | 1.7 | 3.5 | 0.635 +/- 0.189 +/- 0.309 | 0.779

Note that FAP estimates (especially at timescales above 2s) may be
possibly further affected by enhanced non-stationary local background
noise. This list excludes any excesses for which FAP is close to
unity.



All results quoted are preliminary.

This circular is an official product of the INTEGRAL Multi-Messenger
team.

[1] Savchenko et al. 2017, A&A 603, A46
[2] Savchenko et al. 2012, A&A 541A, 122S

C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:

For the IceCube high-energy neutrino candidate event 210730A (GCN 30559
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 ),
the reported position:

RA: 105.73 (+2.00, -1.85 deg  90% PSF containment) J2000
Dec: 14.79 (+0.91, -0.86 deg 90% PSF containment) J2000

was occulted by the Earth for Fermi-GBM from approximately from 4.9 minutes
prior until 26.7 minutes after event time. Therefore, the GBM observations
are not constraining for prompt gamma-ray emission.