The Astrophysical Journal Letters, 857:L4 (6pp), 2018 April 10

https://doi.org/10.3847/2041-8213/aabaca© 2018. The American Astronomical Society. All rights reserved.

Search for Neutrinos in Super-Kamiokande Associatedwith the GW170817 Neutron-star Merger
K. Abe1,2, C. Bronner1, Y. Hayato1,2, M. Ikeda1, K. Iyogi1, J. Kameda1,2, Y. Kato1,2, Y. Kishimoto1,2, Ll. Marti1, M. Miura1,2,
S. Moriyama1,2, M. Nakahata1,2, Y. Nakajima1, Y. Nakano1, S. Nakayama1,2, A. Orii1, G. Pronost1, H. Sekiya1,2, M. Shiozawa1,2,
Y. Sonoda1, A. Takeda1,2, A. Takenaka1,2, H. Tanaka1, S. Tasaka1, T. Yano1, R. Akutsu3, T. Kajita2,3, Y. Nishimura3,
K. Okumura2,3, K. M. Tsui3, L. Labarga4, P. Fernandez4, F. d. M. Blaszczyk5, C. Kachulis5, E. Kearns2,5, J. L. Raaf5, J. L. Stone2,5,
L. R. Sulak5, S. Berkman6, S. Tobayama6, J. Bian7, M. Elnimr7, W. R. Kropp7, S. Locke7, S. Mine7, P. Weatherly7, M. B. Smy2,7,
H. W. Sobel2,7, V. Takhistov7,49, K. S. Ganezer8, J. Hill8, J. Y. Kim9, I. T. Lim9, R. G. Park9, Z. Li10, E. O’Sullivan10,
K. Scholberg2,10, C. W. Walter2,10, M. Gonin11, J. Imber11, Th. A. Mueller11, T. Ishizuka12, T. Nakamura13, J. S. Jang14, K. Choi15,
J. G. Learned15, S. Matsuno15, J. Amey16, R. P. Litchﬁeld16, W. Y. Ma16, Y. Uchida16, M. O. Wascko16, M. G. Catanesi17,
R. A. Intonti17, E. Radicioni17, G. De Rosa18, A. Ali19, G. Collazuol19, L. Ludovici20, S. Cao21 , M. Friend21, T. Hasegawa21,
T. Ishida21, T. Ishii21, T. Kobayashi21, T. Nakadaira21, K. Nakamura21,22, Y. Oyama21, K. Sakashita21, T. Sekiguchi21,
T. Tsukamoto21, KE. Abe23, M. Hasegawa23, A. T. Suzuki23, Y. Takeuchi22,23, T. Hayashino24, S. Hirota24, M. Jiang24, M. Mori24,
KE. Nakamura24, T. Nakaya22,24, R. A. Wendell22,24, L. H. V. Anthony25, N. McCauley25, A. Pritchard25, Y. Fukuda26,
Y. Itow27,28 , M. Murase27, F. Muto27, P. Mijakowski29, K. Frankiewicz29, C. K. Jung30, X. Li30, J. L. Palomino30, G. Santucci30,
C. Viela30, M. J. Wilking30, C. Yanagisawa30,50, D. Fukuda31, H. Ishino31, S. Ito31, A. Kibayashi31, Y. Koshio22,31, H. Nagata31,
M. Sakuda31, C. Xu31 , Y. Kuno32, D. Wark2,33, F. Di Lodovico34, B. Richards34, S. Molina Sedgwick34, R. Tacik35,36,
S. B. Kim37, A. Cole38, L. Thompson38, H. Okazawa39, Y. Choi40, K. Ito41, K. Nishijima41, M. Koshiba42, Y. Suda43,
M. Yokoyama22,43, R. G. Calland22, M. Hartz22, K. Martens22, M. Murdoch22, B. Quilain22, C. Simpson22,33, Y. Suzuki22,
M. R. Vagins7,22, D. Hamabe44, M. Kuze44, Y. Okajima44, T. Yoshida44, M. Ishitsuka45, J. F. Martin46, C. M. Nantais46,
H. A. Tanaka46, T. Towstego46, A. Konaka36, S. Chen47, L. Wan47, and A. Minamino48
The Super-Kamiokande Collaboration
1
Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, Kamioka, Gifu 506-1205, Japan
2

3

STFC, Rutherford Appleton Laboratory, Harwell Oxford, and Daresbury Laboratory, Warrington, OX11 0QX, UK
Research Center for Cosmic Neutrinos, Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
4
Department of Theoretical Physics, University Autonoma Madrid, E-28049 Madrid, Spain
5
Department of Physics, Boston University, Boston, MA 02215, USA
6
Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T1Z4, Canada
7
Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
8
Department of Physics, California State University, Dominguez Hills, Carson, CA 90747, USA
9
Department of Physics, Chonnam National University, Kwangju 500-757, Republic of Korea
10
Department of Physics, Duke University, Durham, NC 27708, USA
11
Ecole Polytechnique, IN2P3-CNRS, Laboratoire Leprince-Ringuet, F-91120 Palaiseau, France
12
Junior College, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan
13
Department of Physics, Gifu University, Gifu, Gifu 501-1193, Japan
14
GIST College, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea
15
Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822, USA
16
Department of Physics, Imperial College London, London SW7 2AZ, UK
17
Dipartimento Interuniversitario di Fisica, INFN Sezione di Bari and Università e Politecnico di Bari, I-70125, Bari, Italy
18
Dipartimento di Fisica, INFN Sezione di Napoli and Università di Napoli, I-80126, Napoli, Italy
19
INFN Sezione di Roma and Università di Roma “La Sapienza”, I-00185, Roma, Italy
20
Dipartimento di Fisica, INFN Sezione di Padova and Università di Padova, I-35131, Padova, Italy
21
High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
22
Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes
for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583, Japan
23
Department of Physics, Kobe University, Kobe, Hyogo 657-8501, Japan
24
Department of Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japan
25
Department of Physics, University of Liverpool, Liverpool L69 7ZE, UK
26
Department of Physics, Miyagi University of Education, Sendai, Miyagi 980-0845, Japan
27
Institute for Space-Earth Enviromental Research, Nagoya University, Nagoya, Aichi 464-8602, Japan
28
Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, Aichi 464-8602, Japan
29
National Centre For Nuclear Research, 00-681 Warsaw, Poland
30
Department of Physics and Astronomy, State University of New York at Stony Brook, NY 11794-3800, USA
31
Department of Physics, Okayama University, Okayama, Okayama 700-8530, Japan
32
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
33
Department of Physics, Oxford University, Oxford OX1 3PU, UK
34
School of Physics and Astronomy, Queen Mary University of London, London E1 4NS, UK
35
Department of Physics, University of Regina, 3737 Wascana Parkway, Regina, SK S4SOA2, Canada
36
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T2A3, Canada
37
Department of Physics, Seoul National University, Seoul 151-742, Republic of Korea
38
Department of Physics and Astronomy, University of Shefﬁeld, Shefﬁeld S10 2TN, UK
39
Department of Informatics in Social Welfare, Shizuoka University of Welfare, Yaizu, Shizuoka 425-8611, Japan40
Department of Physics, Sungkyunkwan University, Suwon 440-746, Republic of Korea
41
Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan

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The Astrophysical Journal Letters, 857:L4 (6pp), 2018 April 10

Abe et al.

42

The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
44
Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan
45
Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan46
Department of Physics, University of Toronto, ON M5S 1A7, Canada
47
Department of Engineering Physics, Tsinghua University, Beijing, 100084, Peopleʼs Republic of China
48
Faculty of Engineering, Yokohama National University, Yokohama, 240-8501, Japan
Received 2018 February 11; revised 2018 March 28; accepted 2018 March 29; published 2018 April 9
43

Abstract
We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the ﬁrst detected
gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which was followed by a shortgamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in therange from 3.5MeV to ∼100 PeV, in a time window ±500 s around the gravitational wave detection time, as wellas during a 14-day period after the detection. No signiﬁcant neutrino signal was observed for either time window.
We calculated 90% conﬁdence level upper limits on the neutrino ﬂuence for GW170817. From the upward-going−2
+0.7
+1.1
for muon
muon events in the energy region above 1.6 GeV, the neutrino ﬂuence limit is 16.00.6 (21.3-0.8) cm
neutrinos (muon antineutrinos), with an error range of ±5° around the zenith angle of NGC4993, and the energy
spectrum is under the assumption of an index of −2. The ﬂuence limit for neutrino energies less than 100MeV, forwhich the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is
6.6×107 cm−2 for anti-electron neutrinos under the assumption of a Fermi–Dirac spectrum with average energy
of 20 MeV.
Key words: astroparticle physics – gravitational waves – neutrinos
performance can be found in Fukuda et al. (2003) and Abe
et al. (2014). In this detector, the Cherenkov ring patternreconstruction identiﬁes ﬁnal-state electron and muon directionand energy, from which we infer the neutrino direction, ﬂavor,
and energy. SK has sensitivity to a wide neutrino energy region
and is able to reconstruct neutrino event energies from a few
MeV to ∼100PeV. Neutrino events with reconstructedenergies above 100MeV are categorized as the “high-energy
data sample” in SK and are typically used to study atmospheric
neutrinos and to search for proton decay. Neutrino events withreconstructed energies down to 3.5MeV are categorized as the“low-energy data sample” and are typically used to study solar
neutrinos and search for core-collapse supernova neutrinos.
The directional determination accuracy varies according tosample and direction, but can be as accurate as ∼1° for upwardgoing muons. Some theoretical predictions of neutrino
emission mechanism via binary neutron-star mergers havebeen proposed; for example, some fraction of the kinetic
energy in relativistic ejecta from gamma-ray bursts could
convert to high-energy (∼1014 eV) neutrinos (Waxman &Bahcall 1997), or a similar mechanism as for core-collapse
supernovae could produce few-tens-of-MeV neutrinos (Sekiguchi et al. 2011; Kyutoku & Kashiyama 2017); the expected
ﬂuence is roughly estimated to be 104 cm−2 for 10 MeV
neutrinos within 1 s after merger. Neutrino observations
associated with a binary neutron-star merger using the uniquecharacteristics in SK would validate such proposed mechanisms. We searched for coincident events in the full data sample
using the same time window as ANTARES-IceCube-Pierre
Auger, i.e., ±500 s around the merger time and in a 14-daytime window relevant for longer-lived emission processes. The
primary background events for this search in the high-energy
data sample are almost entirely atmospheric neutrinos, while
radioactive impurities, spallation products from cosmic-ray
muons, and atmospheric and solar neutrinos are the main
backgrounds in the low-energy data sample. We note that SK
carried out a LINAC calibration (Nakahata et al. 1999) from2017 August 3 to 22. Fortunately, physics data-taking operated

1. Introduction
On 2017 August 17 at 12:41:04 UTC, the Advanced Laser
Interferometer Gravitational-wave Observatory (LIGO) and
Advanced Virgo experiment identiﬁed the ﬁrst evident signalof a gravitational wave (GW) from the binary neutron-starmerger, named GW170817 (Abbott et al. 2017b). Theinterpretation is that this is a merger of two compact objects
consistent with neutron stars, having total system mass of 2.74
solar masses and a luminosity distance of 40 Mpc. Associatedwith this gravitational wave signal, the Fermi Gamma-ray
Burst Monitor and the International Gamma-ray Astrophysics
Laboratory also detected a short gamma-ray burst,
GRB170817A, which has a consistent location with the merger
and a 1.7 s delay to the merger time (Abbott et al. 2017a).
Subsequent extensive electromagnetic follow-up observations
in ultra-violet, optical, and infrared wavelengths were
performed. These observations led to the conclusion that themerger happened in galaxy NGC4993 and was followed by ashort gamma-ray burst and a kilonova/macronova Abbott et al.
(2017c); Coulter et al. (2017). High-energy neutrino signals
associated with the merger were also searched for by the
Astronomy with a Neutrino Telescope and Abyss Environmental RESearch (ANTARES), IceCube, and Pierre Auger
Observatories. It was concluded that no signiﬁcant neutrinosignal was observed (Albert et al. 2017).
We report the results of a search for neutrinos in SuperKamiokande (SK) associated with this gravitational wave
signal produced by the binary neutron-star merger in
NGC4993. The analysis method is similar to that for theprevious neutrino search in SK for GW150914 and GW151226(Abe et al. 2016a). SK is a water Cherenkov detector with 50kton water mass and 22.5-kton ﬁducial volume. It is located2700 m water-equivalent underground in Kamioka, Japan. A
detailed description of the detector, its calibration, and49
Also at Department of Physics and Astronomy, UCLA, CA 900951547, USA.
50
Also at BMCC/CUNY, Science Department, New York, NY, USA.

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Abe et al.

sample only contains upgoing muons, so it is sensitive to only
half of the sky. In 60.4% of the subsequent 14 days, NGC4993
is within the sensitive half. Because the direction of NGC4993
is well known Abbott et al. (2017c); Coulter et al. (2017), for
UPMU data, for which the angular resolution is better than forthe other two samples, we concentrated on a ±5° cone around
NGC4993 for the event search in the subsequent 14 days. Thismethod was previously used in SK to search for neutrinosignals associated with astrophysical objects (Abe et al. 2017).
The ±5° constraint was not used for the ±500 s search in
Table 1 because no event was observed in all sky during thiswindow, and unlike the 14-day-window case, the zenith angle
change of NGC4993 in ±500 s can be ignored. All of theresults listed in Table 1 are consistent with our expected event
rates.

Table 1
Numbers of Expected and Observed Events in FC, PC, and UPMU
Data Sets, Respectively, for a ±500-s Time Window around
GW170817 and for 14 Days after GW170817
Observed Num. of Event

Expected Num. of Eventin ±500 s
FC
PC
UPMU

0
0
0

(9.36±0.06)×10−2(7.52±0.23)×10−3(1.64±0.02)×10−2

following 14 days for all sky
FCPC

76±8.72
8±2.83

91.44±0.57
7.35±0.23

following 14 days for 5° solid angle
UPMU

0(6.11±0.04)×10−2

2.2. Low-energy Data Sample
Note. The errors on the observed number of events in the subsequent 14 days
for the entire sky are N . For UPMU event search in the subsequent 14 days,
the event number in a solid angle of ±5° around NGC4993 was shown instead.
The total livetime for the following 14 days is 11.30 days.

Assuming that the ﬂux is approximately equally distributed
among ﬂavors, as for a core-collapse supernova, the dominantchannel in the 3.5–100 MeV range is the inverse beta decay ofelectron antineutrinos (n¯e + p  e+ + n ). The second-mostdominant one is neutrino elastic scattering (n + e-  n + e-),which is sensitive to all neutrino ﬂavors but dominated byelectron neutrinos. Positrons or electrons from these interactions can produce observable signals in the SK detector. There
are other charged-current and neutral-current interactions with
16
O nuclei that are subdominant.
There are two data samples used by SK for low-energy
analysis: one tuned for the supernova relic neutrino (SRN)
search (Bays et al. 2012) and another for the solar neutrino
analysis (Abe et al. 2016b). These are independent selection
methods and apply to different energy ranges for the
GW170817 event search. The solar neutrino analysis is appliedin the 3.5–15.5 MeV range, while the SRN analysis focuses on
the 15.5–100 MeV range. In the low-energy analysis, the main
background under 20 MeV is spallation products from cosmicray muons, and above 20 MeV the dominant background isfrom atmospheric-neutrino interactions (decay electrons frominvisible muons, neutral-current interactions, and low-energy
pions and muons). It should be mentioned that, in this analysis
for the GW170817 event search, we do not require a neutron
signal (Zhang et al. 2015).
After all of the reduction steps, no neutrino was observed in
the SRN analysis within the ±500-s search window around
GW170817. The expected number of background events in a
±500-s time window is (1.93±0.08)×10−3, based on 2887
days of data.
In the SRN sample for the 14 days after GW170817, twoevents were found, on 2017 August 24 10:33:04 UTC and on
2017 August 28 14:36:34 UTC. The reconstructed energies ofthese two events are 22.0 and 40.4 MeV in kinetic energy, andthe angles between their reconstructed directions andNGC4993 are (55.41±15.81)° and (145.24±11.30)°.
Because of the LINAC calibration, livetime for the subsequent
14 days of SRN-analysis data is 9.15 days, and the expected
number of events is 1.53±0.06, so the probability ofobserving two or more events is 45.1%. This is consistent
with the expected signal rate and we do not classify these as
GW170817 neutrinos rather than SRN candidates. Therefore,
the ﬂuence limit calculation, which will be discussed in next
section, is performed based on the result of the ±500-s window
search.

at the time when the neutron-star merger occurred; however,there were unavoidable radioactive impurities adhered on thesurface of the linear accelerator (LINAC) beam pipe present in
the low-energy data sample.
2. Search Method and Results
2.1. High-energy Data Sample
The high-energy data sample has three different categories:
fully contained (FC), partially contained (PC), and upwardgoing muon (UPMU). FC neutrinos have reconstructedinteraction vertices inside the ﬁducial volume of the innerdetector, combined with low light levels in the outer detector.
PC neutrinos also have interaction vertices inside the ﬁducial
volume, but have signiﬁcant light in the outer detector volume
indicating exiting particles. UPMU neutrinos are the highestenergy SK sample; they result from muon-neutrino interactionsin the rock surrounding the detector, which produce penetrating
muons. These muons either stop in the inner-detector volume
as stopping events, or go through the inner detector as throughgoing events. The energy range for neutrino parents in FC andPC sample is 100 MeV–10 GeV, and for UPMU it is 1.6 GeV–
100 PeV. All three event topologies are considered for thissearch. Further information about the selection and reconstruction methods for the three categories can be found in Ashieet al. (2005).
A ±500-s window search around the LIGO detection time of
GW170817, as well as a 14-day window search following the
GW detection, have been conducted in the SK detector. These
windows are consistent with those selected in Albert et al.
(2017). The expected number of events based on 2976.01 daysof SK data, and the number of events that we actually observed,
are listed in Table 1 for a ±500-s window and for the following
14-day interval. The livetime for the high-energy analysis after
removing LINAC beam runs for the following 14 days after
GW170817 is 11.30 days. In a ±500-s window around
GW170817, no neutrino event was found in the FC, PC, or
UPMU data sets. This null result is used in the calculation of
the upper limit on neutrino ﬂuence in the subsequent sectionsof this Letter. Unlike the FC and PC samples, the UPMU
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Abe et al.

The same search windows were applied to the solar neutrino
data and no event was found in a ±500-s window around
GW170817. Using the data after 2015 May 1, with a livetimeof 306.6 days, we expect 2.90±0.01 events in ±500 s; theprobability of no event is 5.5%. Due to LINAC calibration
work during 2017 August, tank opening and hardware changes
were carried out so frequently that the quality of the event
selection and reconstruction in the solar neutrino data sample
was not stable, primarily due to radioactive impurities from the
LINAC pipe. Therefore, we omit discussion of the subsequent
14-day data sample.
3. Neutrino Fluence Limit
As there is no event observed within a ±500-s window,
either in low- or high-energy data, the null number can beconverted to an upper limit on neutrino ﬂuence. This is done
separately for the low-energy, FC+PC, and UPMU data sets.
The ﬂuence limit was calculated using the same procedure laidout in Thrane et al. (2009), which follows from Swanson
et al. (2006).
For the FC and PC data set, the neutrino ﬂuence can becalculated using Equation (1),
FFC,PC =N90,
NT ò dEn s (En )  (En ) l (En-2)

Figure 1. 90% CL limits for GW170817 events on ﬂuence obtained for monoenergetic neutrinos at 4, 7, 10, 14, 20, 30, 50, 80, and 100 MeV.
Table 2
Limits at 90% CL on the Fluence of Neutrinos from GW170817, Given a
Spectral Index of −2 and a Range of 100 MeV–10 GeV for FC+PC and1.6 GeV–100PeV for UPMU Data
GW170817 Φν (cm−2)
from FC+PC only

N90 is the 90% Chandrasekhar limit (CL) calculated from a
Poisson distribution for the observed neutrino events in a
±500-s window with the expected background number. As
there is no neutrino event found in a ±500-s window for FC,
PC, or UPMU data, N90 can be ﬁxed as N90=−ln(0.1)=2.3.
NT is the number of target nuclei relevant to the neutrino
interactions. σ is the combined cross section for all interactions.
ò is detection efﬁciency, and λ is the density of Eν assuming anenergy spectrum with index of −2. This spectral index iscommonly assumed for astrophysical neutrinos accelerated byshocks (Gaisser et al. 1995).
Fluence limits are calculated separately for each neutrino
type because the cross section and detection efﬁciency dependon neutrino type. Cross sections in Equation (1) are from
NEUT 5.3.5 Hayato (2009). NEUT 5.3.5 is also used to
produce mono-energetic neutrino interactions in the SK Monte
Carlo detector simulation in order to determine the detection
efﬁciency.
For the UPMU data set, the neutrino ﬂuence is calculatedusing Equation (2),FUPMU =N90.
A eff (z) ò dEn P (En ) S (z , En ) l (En-2)

from UPMU only

5.6×10
1.3×105
4.8×104
1.2×105+0.7
16.00.6+1.1
21.30.8
L
Lfrom low-energy only
ﬂat spectrum

Fermi–Dirac with Eave=20MeV

νμ
n¯m
νe
n̄e

(1 )

4

n̄e
νe
n̄x
νx

7

1.2×10
1.0×109
7.5×109
6.3×109

6.6×107
3.4×109
2.6×1010
2.1×1010

Note. The error of the UPMU limit is made with ±5° range around zenith angleof NGC4993. Low-energy limits assume a ﬂat spectrum as well as a Fermi–
Dirac spectrum with Eaverage=20MeV from 3.5 to 100MeV. νx(n̄x )represents νe(n̄e ) and νμ(n¯m )with average energy of 20 MeV:
Flowe =

N90,
NT ò dEn l (En ) s (En ) R (Ee, E vis)  (E vis)

(3 )R is the response function to convert electron or positronenergy (Ee) to kinetic energy in SK (Evis). The response
function and the detection efﬁciency (ò) are calculated using
SK detector Monte Carlo simulation. Again, no event wasobserved in ±500s, so N90 is 2.3.
We also express the ﬂuence limit that is calculated formonochromatic neutrino energy Eν. The ﬂuence limits at
various energies are shown in Figure 1. The results of ﬂuence
limits for FC+PC, UPMU, and low-energy data are summarized in Table 2. The UPMU upper limit ﬂuence values range
from (14–37) cm−2 for neutrinos and from (18–50) cm−2
for antineutrinos, depending on zenith angle from 90° to 0°.
To focus on the direction of NGC4993, the UPMU limit is
−2
−2
+0.7
+1.1
16.0and 21.3for neutrinos and antineutri0.6 cm
0.8 cmnos, while the error is calculated by a range of ±5° around thezenith angle of NGC4993. We show the upper limit of neutrino
ﬂuence from UPMU events as a sky map in Figure 2. We note

(2 )The ﬂuence of UPMU events depends on zenith angle.
Aeff(z) is the zenith-dependent effective area, where z is the thezenith angle of the incoming neutrino. P(Eν) is the probability
for a neutrino to create a muon with energy greater than Enmin . S(z, Eν) is the shadowing of the neutrinos due to interactions in
the Earth. As for the FC and PC analysis, λ here is the number
density of Eν in a spectrum with index of −2.
The ﬂuence calculation for low-energy neutrinos uses anexpression similar to (1) but with different energy spectra. Here
we assume two kind of spectra, one with an index of 0, i.e., a
ﬂat spectrum, and another being a Fermi–Dirac distribution
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Abe et al.

Figure 2. 90% CL limit on ﬂuence for neutrinos (left) and antineutrinos (right) in the UPMU data set, overlaid with the 90% CL contour for the location of GW170817
according to LIGO and Virgo released data (solid red line).

in a limited spatial region around NGC4993, is consistent withthe expectation.
Low-energy neutrino events were also examined using the
SRN and the solar neutrino data samples in the same window.
No neutrino candidate was found in the SRN and solar neutrino
data samples in the ±500-s window. Two candidates were
found in the SRN data sample in the 14-day search window,
which is consistent with the estimated background rate.
Considering the observation of no signiﬁcant neutrino signal
associated with the GW170817 in SK, we calculated theneutrino ﬂuence limits. The obtained results give the moststringent limits for neutrino emission in the energy region
below 100GeV.
We gratefully acknowledge the cooperation of the Kamioka
Mining and Smelting Company. The Super-Kamiokande
experiment has been built and operated from funding by theJapanese Ministry of Education, Culture, Sports, Science andTechnology, the U.S. Department of Energy, and the U.S.
National Science Foundation. Some of us have been supported
by funds from the National Research Foundation of Korea
NRF-2009-0083526 (KNRC) funded by the Ministry of
Science, ICT, and Future Planning, the European Union
H2020 RISE-GA641540-SKPLUS, the Japan Society for the
Promotion of Science, the National Natural Science Foundationof China under grants No. 11235006, the National Science andEngineering Research Council (NSERC) of Canada, the Scinet
and Westgrid Consortia of Compute Canada, and the National
Science Centre, Poland (2015/17/N/ST2/04064, 2015/18/
E/ST2/00758).

Figure 3. 90% CL limits for the UPMU data set during a ±500-s window inthe direction of NGC4993. Limits are calculated separately for each energy
range, by assuming a spectrum with index of −2.

that the present study is sensitive to neutrinos between 1.6 and100 GeV, which is not covered in other searches (Albert et al.
2017). Our UPMU data may be compared or combined directlywith that of other neutrino telescopes. We provide a UPMU
ﬂuency limit in Figure 3.
Considering dGW as the distance from the detector to
NGC4993, our upper limit on ﬂuence of UPMU data can beconverted into an upper limit on total radiated energy in2in Equation (2). The
neutrinos, by weighting by 4pd GW
resulting upper limit on total energy is Entot ~ (1–6)×1053 erg
for GW170817, assuming the luminosity distance of 40 Mpc.

ORCID iDs

4. Conclusion

S. Cao https://orcid.org/0000-0002-8870-981X
Y. Itow https://orcid.org/0000-0002-8198-1968
C. Xu https://orcid.org/0000-0002-4968-2466

We made a coincidence search for neutrino signals with thegravitational wave GW170817 produced by a binary neutronstar merger in NGC4993, in the SK detector in an energy range
from 3.5MeV to ∼100PeV. The analysis was performed
within a time window of ±500 s of GW170817 and 14 days
after the neutron-star merger.
In the high-energy data sample, three neutrino interaction
categories are considered: FC, PC, and UPMU. No neutrino
candidate was found in the ±500-s window. The number ofcandidates in a 14-day time window in the entire sky, as well as

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