IceCube-191204A

Diego Gotz (AIM CEA Saclay, France),  Enrico Bozzo, 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 INTEGRAL/SPI-ACS realtime data (following [1]) we have performed
a search for a prompt gamma-ray counterpart of IceCube-191204A.

At the time of the event (2019-12-04 22:46:11 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 79 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(4.7% of optimal) response of ISGRI, strongly suppressed (8.2% of
optimal) response of IBIS/Veto, and somewhat suppressed (65%! of
op timal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

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

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 2.6e-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 ~2.1e-07 (7e-08)
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 reg! ion. We find: 7 likely background
excesses:

scale | T | S/N | flux ( x 1e-06 erg/cm2/s) | FAP  
0.9 | -31.8 | 3.9 | 3.64 +/- 0.889 +/- 0.953 | 0.129 
2.4 | -41.2 | 3.2 | 1.82 +/- 0.542 +/- 0.476 | 0.236 
0.35 | -21.2 | 3.8 | 0.567 +/- 0.143 +/- 0.148 | 0.251 
0.05 | 71.1 | 7 | 2.85 +/- 0.393 +/- 0.747 | 0.44  
1.5 | -51.6 | 3.1 | 2.3 +/- 0.687 +/- 0.603 | 0.562 
0.75 | 139 | 3.7 | 3.85 +/- 0.974 +/- 1.01 | 0.853 
0.6 | 217 | 4.2 | 0.472 +/- 0.109 +/- 0.123 | 0.918 

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

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

On 19/12/04 at 22:46:11.32 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 3.21 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/133394_27261780.amon <https://gcn.gsfc.nasa.gov/notices_amon_g_b/133394_27261780.amon>), more 
sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 19/12/04 
Time: 22:46:11.32 UT
RA: 79.72 (+3.20 -1.74 deg 90% PSF containment) J2000
Dec: 2.80 (+1.12 -1.23 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 J0521.6+0103 at RA: 80.41 deg, Dec: 1.05 deg (1.88 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

C. M. Hui (MSFC) and P. Veres (UAH) report on behalf of the Fermi-GBM team:



For the IceCube high-energy neutrino candidate event 191204A (GCN 26341
Loading...
 
 ), at the event time Fermi-GBM was observing the reported neutrino location at:



RA: 79.72 (+3.20 -1.74 deg 90% PSF containment) J2000

Dec: 2.80 (+1.12 -1.23 deg 90% PSF containment) J2000



There was no Fermi-GBM onboard trigger around the event time of the neutrino candidate. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around the neutrino candidate time. From this search, no significant signal was found related to IceCube-191204A.



We set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395
Loading...
 
 , we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2):



Timescale  Soft     Normal   Hard

-------------------------------------------

0.128 s:     15      20      37

1.024 s:      3.4     4.4    12

8.192 s:      1.3     2.3     3.6

S. Buson (Univ. of Wuerzburg) and S. Garrappa (DESY-Zeuthen)  on behalf of the Fermi-LAT collaboration:
We report an analysis of observations of the vicinity of the high-energy IC191204A neutrino event (GCN 26341
Loading...
 
 ) 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 2019-12-04 at 22:46:11.32 UT (T0) with J2000 position RA = 79.72 (+3.20, -1.74) deg, Decl. = 2.80(+1.12, -1.23) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC191204A localization error.
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 IC191204A 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 < 2.6e-10 ph cm^-2 s^-1 for ~11-years (2008-08-04 / 2019-12-04 UT), < 8e-9 (< 5e-9) 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 are S. Buson (sara.buson at uni-wuerzburg.de) and S. Garrappa (simone.garrappa at desy.de <http://desy.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.

Hugo Ayala (PSU) reports on behalf of the HAWC
collaboration (http://www.hawc-observatory.org/collaboration):

On 2019/12/04 22:46:11.32 UTC, the IceCube collaboration reported a
track-like very-high-energy event  that has a high probability of
being an astrophysical neutrino, IceCube-191204A. Location is at
RA: 79.72 (+3.20/-1.74  90% PSF containment) J2000
Dec: 2.80(+1.12/-1.23 deg 90% PSF containment) J2000
https://gcn.gsfc.nasa.gov/gcn3/26341.gcn3
Loading...
 
 
(GCN circular 26341
Loading...
 
 ).

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 May 2018. We searched
inside the reported IceCube error region from the circular.
The highest significance, 2.93 sigma (1.28 post-trials),
is at RA 82.57 deg, Dec 2.99 deg J2000.
We set a time-integrated 95% CL  upper limit on gamma rays at the
maximum position of:

E^2 dN/dE < 3.414e-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 Data Start: 2019/12/03 09:40:53 UTC and ended
2019/12/04 09:53:59 UTC.
The most significant location, with 3.27 sigma (1.86 post-trials),
is at RA 80.99 deg, Dec 3.49 deg (J2000).
We set a time-integrated 95% CL upper limit at the position of
maximum significance of:

E^2 dN/dE < 1.235e-11 (E/1TeV)^-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.

Y. G. Zheng, C. Cai, Q. Luo, S. Xiao, Q. B. Yi, 
Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong,
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

Insight-HXMT was taking data normally around the trigger time
(T0=2019-12-04 22:46:11.32 UTC) of this high-energy neutrino event 
(GCN #26341
Loading...
 
 ), which was monitored without any occultation by 
the Earth. 

Within T0 +/- 100 s, no significant excess events (SNR > 3 sigma) 
are found in a search of the Insight-HXMT/HE raw light curves.

Assuming the counterpart GRB with three typical GRB Band spectral 
models, two typical duration timescales(1 s, 10 s) coming from the position
of this neutrino event, the 5-sigma upper-limits fluence 
(0.2 - 5 MeV, incident energy) are reported below:

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1s:  9.1e-07 erg cm^-2   
10s: 1.5e-06 erg cm^-2 

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1s:  1.1e-06 erg cm^-2   
10s: 1.8e-06 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1s:  1.0e-06 erg cm^-2  
10s: 2.8e-06 erg cm^-2 

Further analysis will be reported in the following circulars.

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (record energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the telescope.

Insight-HXMT is the first Chinese space X-ray telescope, which was 
fundedjointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information could be found at: http://www.hxmt.org.