The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

doi:10.3847/2041-8205/830/1/L11© 2016. The American Astronomical Society. All rights reserved.

SEARCH FOR NEUTRINOS IN SUPER-KAMIOKANDE ASSOCIATED WITHGRAVITATIONAL-WAVE EVENTS GW150914 AND GW151226
K. Abe1,32, K. Haga1, Y. Hayato1,32, M. Ikeda1, K. Iyogi1, J. Kameda1,32, Y. Kishimoto1,32, M. Miura1,32, S. Moriyama1,32,
M. Nakahata1,32, T. Nakajima1, Y. Nakano1, S. Nakayama1,32, A. Orii1, H. Sekiya1,32, M. Shiozawa1,32, A. Takeda1,32,
H. Tanaka1, S. Tasaka1, T. Tomura1,32, R. Akutsu2, T. Kajita2,32, K. Kaneyuki2,32,37, Y. Nishimura2, E. Richard2,
K. Okumura2,32, L. Labarga3, P. Fernandez3, F. d. M. Blaszczyk4, J. Gustafson4, C. Kachulis4, E. Kearns4,32, J. L. Raaf4,
J. L. Stone4,32, L. R. Sulak4, S. Berkman5, C. M. Nantais5, S. Tobayama5, M. Goldhaber6,37, W. R. Kropp7, S. Mine7,
P. Weatherly7, M. B. Smy7,32, H. W. Sobel7,32, V. Takhistov7, K. S. Ganezer8, B. L. Hartﬁel8, J. Hill8, N. Hong9,
J. Y. Kim9, I. T. Lim9, R. G. Park9, A. Himmel10, Z. Li10, E. O’Sullivan10, K. Scholberg10,32, C. W. Walter10,32,
T. Ishizuka11, T. Nakamura12, J. S. Jang13, K. Choi14, J. G. Learned14, S. Matsuno14, S. N. Smith14, M. Friend15,
T. Hasegawa15, T. Ishida15, T. Ishii15, T. Kobayashi15, T. Nakadaira15, K. Nakamura15,32, Y. Oyama15, K. Sakashita15,
T. Sekiguchi15, T. Tsukamoto15, A. T. Suzuki16, Y. Takeuchi16,32, T. Yano16, S. V. Cao17, T. Hiraki17, S. Hirota17,
K. Huang17, M. Jiang17, A. Minamino17, T. Nakaya17,32, N. D. Patel17, R. A. Wendell17,32, K. Suzuki17, Y. Fukuda18,
Y. Itow19,20, T. Suzuki19, P. Mijakowski21, K. Frankiewicz21, J. Hignight22, J. Imber22, C. K. Jung22, X. Li22,
J. L. Palomino22, G. Santucci22, M. J. Wilking22, C. Yanagisawa22,38, D. Fukuda23, H. Ishino23, T. Kayano23,
A. Kibayashi23, Y. Koshio23,32, T. Mori23, M. Sakuda23, C. Xu23, Y. Kuno24, R. Tacik25,34, S. B. Kim26, H. Okazawa27,
Y. Choi28, K. Nishijima29, M. Koshiba30, Y. Totsuka30,37, Y. Suda31, M. Yokoyama31,32, C. Bronner32, R. G. Calland32,
M. Hartz32, K. Martens32, Ll. Marti32, Y. Suzuki32, M. R. Vagins7,32, J. F. Martin33, H. A. Tanaka33, A. Konaka34,
S. Chen35, L. Wan35, Y. Zhang35, and R. J. Wilkes36(The Super-Kamiokande Collaboration)
1
Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, Kamioka, Gifu 506-1205, Japan
Research Center for Cosmic Neutrinos, Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan3
Department of Theoretical Physics, University Autonoma Madrid, E-28049 Madrid, Spain
4
Department of Physics, Boston University, Boston, MA 02215, USA
5
Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T1Z4, Canada
6
Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA
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, Korea
10
Department of Physics, Duke University, Durham, NC 27708, USA
11
Junior College, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan
12
Department of Physics, Gifu University, Gifu, Gifu 501-1193, Japan
13
GIST College, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
14
Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822, USA
15High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
16
Department of Physics, Kobe University, Kobe, Hyogo 657-8501, Japan17
Department of Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japan18
Department of Physics, Miyagi University of Education, Sendai, Miyagi 980-0845, Japan
19
Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi 464-8602, Japan
20
Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya, Aichi 464-8602, Japan
21
National Centre For Nuclear Research, 00-681 Warsaw, Poland
22
Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY 11794-3800, USA
23
Department of Physics, Okayama University, Okayama, Okayama 700-8530, Japan
24
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
25
Department of Physics, University of Regina, 3737 Wascana Parkway, Regina, SK S4S OA2, Canada
26
Department of Physics, Seoul National University, Seoul 151-742, Korea
27
Department of Informatics in Social Welfare, Shizuoka University of Welfare, Yaizu, Shizuoka 425-8611, Japan
28
Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea
29
Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan
30
The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
31
Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
32
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
33
Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada
34
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T2A3, Canada
35
Department of Engineering Physics, Tsinghua University, Beijing, 100084, China
36
Department of Physics, University of Washington, Seattle, WA 98195-1560, USA
Received 2016 August 31; revised 2016 September 20; accepted 2016 September 20; published 2016 October 6

2

ABSTRACTWe report the results from a search in Super-Kamiokande for neutrino signals coincident with the ﬁrst detected
gravitational-wave events, GW150914 and GW151226, as well as LVT151012, using a neutrino energy range
37
38

Deceased.
Also at BMCC/CUNY, Science Department, New York, NY, USA.

1

The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

Abe et al.

from 3.5 MeV to 100PeV. We searched for coincident neutrino events within a time window of±500 s around thegravitational-wave detection time. Four neutrino candidates are found for GW150914, and no candidates are foundfor GW151226. The remaining neutrino candidates are consistent with the expected background events. We
calculated the 90% conﬁdence level upper limits on the combined neutrino ﬂuence for both gravitational-wave
events, which depends on event energy and topologies. Considering the upward-going muon data set (1.6 GeV–
100 PeV), the neutrino ﬂuence limit for each gravitational-wave event is 14–37 (19–50) cm−2 for muon neutrinos(muon antineutrinos), depending on the zenith angle of the event. In the other data sets, the combined ﬂuence limits
for both gravitational-wave events range from 2.4×104 to 7.0×109 cm−2.
Key words: astroparticle physics – gravitational waves – neutrinos
1. INTRODUCTION

to search for core-collapse supernova neutrinos. The background events in the search for astrophysical neutrinos for thehigh-energy data sample are almost entirely atmospheric
neutrinos, while radioactive impurities, spallation products
from cosmic-ray muons, atmospheric and solar neutrinos are
the main backgrounds in the low-energy data sample.

On 2015 September 14 at 09:50:45 UT, LIGO identiﬁed theﬁrst evident signal of a gravitational wave as a coincidence of
two chirp signals observed by two distant independentinterferometers (Abbott et al. 2016c). It has been suggested
that the gravitational-wave event, namely, GW150914, was due
to a merger of two black holes having masses of approximately
30 to 60 solar mass. After the announcement of the discovery
by the LIGO team on 2016 February 11, many efforts to searchfor coincidences in the observational data in complementary
experiments have been made (Abbott et al. 2016b); no
astronomical counterpart has been identiﬁed, except a weak
coincident excess reported by Fermi GBM ∼0.4 s after
GW159014 (Connaughton et al. 2016), although this result is
controversial (Greiner et al. 2016). Because of the tremendous
energies involved and the unknown nature of the region of theblack hole merger, it is possible to imagine coincident
production of neutrinos. For example, the possibility of highenergy neutrino emission from relativistic jets when an
accretion disk is formed around the source has been discussed(Eichler et al. 1989; Woosley 1993). IceCube and ANTARES
have searched for high-energy neutrinos above ∼100 GeV in atime window of±500 s around the real-time alert for
GW150914 issued by LIGO, but reported no positive evidence
for coincident neutrino events (Adrián-Martínez et al. 2016).
Following this event the second gravitational-wave signal,
GW151226, was reported (Abbott et al. 2016a). It wasobserved on 2015 December 26 at 03:38:53 UT and was
predicted to be due to a merger of two black holes having
masses of 14.2 and 7.5 solar mass. KamLAND reported no
positive coincident neutrino events for both of these two
gravitational-wave events (Gando et al. 2016).
We report the results of a search for neutrinos in coincidencewith GW150914 and GW151226 in Super-Kamiokande (SK).
It is a water Cherenkov detector located at2700-meters-waterequivalent underground in Kamioka, Japan. A detailed
description of the detector can be found elsewhere (Fukuda
et al. 2003). 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. Our search includes the neutrino energy region of
1–100 GeV, which is not covered by the previous searcheswith neutrino telescopes. Moreover, SK has unique sensitivity
to MeV neutrinos either from a core-collapse supernova in the
Local Group or from some other similarly efﬁcient mechanism.
The neutrino events with reconstructed energies above
100 MeV are categorized as the “high-energy data sample” inSK and are typically used to study atmospheric neutrinos andsearch for proton decay. Neutrino events with reconstructedenergies down to 3.5 MeV are categorized as the “low-energy
data sample” and are typically used to study solar neutrinos and2. SEARCH METHOD AND RESULTS
2.1. High-energy Data Sample
The high-energy data samples consist of three distinct
topologies: fully contained (FC), partially contained (PC), andupward-going muon (UPMU). FC neutrino events have reconstructed interaction vertices inside the ﬁducial volume with little
light detected in the outer detector. PC neutrino events also haveinteraction vertices within the ﬁducial volume of the innerdetector, but there is signiﬁcant light in the outer detector volume.
UPMU neutrino events are the highest-energy events in the SK
detector and are due to muon neutrino interactions in thesurrounding rock that produce penetrating muons. These muons
either stop in the inner detector volume (stopping events) orcontinue through the inner detector (through-going events). All
three data topologies are considered for this search. Further
information about the event topologies, as well as the selection
cuts used to identify them, can be found in Ashie et al. (2005).
A search window of±500 s around the LIGO detection timeof each gravitational-wave event is selected. This is consistent
with the time window chosen by the authors of AdriánMartínez et al. (2016). Using data from 2339.4 days of livetime
in SK, the number of neutrino events we expect to see in a1000 s time window is (9.41 ± 0.07)×10−2 for the FC dataset, (7.52 ± 0.23)×10−3 for the PC data set, and(1.65 ± 0.03)×10−2 for the UPMU data set. In the searchwindow around both GW150914 and GW151226, no neutrino
events were 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 sections of this Letter.
2.2. Low-energy Data Sample
There are two neutrino event selection algorithms for the lowenergy data sample: the supernova relic neutrino (SRN) search(Bays et al. 2012) and the solar neutrino analysis (Abe et al.
2016). The largest cross section in this energy region is theinverse beta decay of electron antineutrinos (n¯e + p  e+ + n ).
Neutrino elastic scattering (n + e-  n + e-) is sensitive to allneutrino ﬂavors, but dominated by electron neutrinos. The
observable signal in the detector originates from the charged
particle, i.e., positron or electron in these interactions. There areother charged-current and neutral-current interactions with 16O
nuclei that are subdominant.
2The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

Abe et al.

Figure 1. Detection time and the observed kinetic energy of the charged particle (left) and the energy spectrum with the expected background spectrum (right) after
reduction cuts for the solar neutrino analysis are applied to the 1000 s search window around GW150914. The detection time of the four neutrino event candidates are
as follows; No.1 9:46:07, No.2 9:51:00, No.3 9:57:40, No.4 9:58:28 UT. The energy threshold of this analysis, shown with the blue dashed line, is 3.5 MeV in kinetic
energy.

The target energy range for the SRN analysis is from 15.5 to79.5 MeV. Backgrounds relevant to the SRN analysis areatmospheric neutrino interactions (decay electrons frominvisible muons, neutral-current interactions, low-energy pions
and muons), solar neutrino interactions, and spallation products
from cosmic-ray muons. The detailed analysis method and the
reduction criteria are described in Bays et al. (2012), which, aswell as this analysis, does not require a neutron capture indelayed coincidence (Zhang et al. 2015). After all the reduction
steps, no neutino events are observed for the SRN analysis in
the ±500s search window around both GW150914 and
GW151226. The expected number of background events in a1000 s time window is (1.45±0.09)×10−3 based on 1888.9
days of data. The absence of neutrino events in this energy
region excludes the scenario of a coincidence between thegravitational-wave and a core-collapse supernova within adistance of 260kpc at 90% C.L.
The energy region considered in the solar neutrino analysis
is lower than that of the SRN search, from 3.5 to 19.5 MeV.
The ﬂuence calculation will be applied below 15.5 MeV toavoid double counting with the SRN sample. After applying all
the reduction steps for the solar neutrino analysis, four neutrino
event candidates remain within the ±500 s search window
around the LIGO detection time of GW150914, while noneutrino event candidates remain around GW151226. Figure 1
shows the detection time and the energy of neutrino event
candidates passing the reduction cuts for GW150914 (left) andthe energy spectrum of the remaining events, which isconsistent with the background spectrum (right). On 2015
May 1, the trigger threshold was changed from 34 observed
PMT signals within 200ns to 31hits (Yamada et al. 2009;
Nakano 2016). Using the data after that (306.6 days of
livetime) we expect (2.90±0.01) events due to random
coincidence for each 1000 s time window centered around agravitational-wave incident. For GW150914 the probability ofseeing four or more events passing the reduction cuts is

calculated to be 33.0%, the probability of seeing none for
GW151226 is 5.5%. Therefore, our ﬁndings are consistent withall of these neutrino event candidates being background.
The background events in the solar neutrino analysis consist
mainly of radioactive impurities below 5.5 MeV and spallation
products above 5.5 MeV. The ﬁrst and second events are most
likely remaining spallation events caused by 16N (Zhang et al.
2016). The transverse distance between each event and its
preceding muon are 1.7 and 1.2 m, the timing differences
between the event and the preceding muon are 10.77 and17.38 s, and the energies are above 6 MeV, making these
consistent with spallation production. Additionally, the likelihood value of the spallation product falls close to the cut
value applied in the reduction steps. The expected number ofbackground events above 5.5 MeV that survive the reduction
cuts is (1.169±0.007); therefore the probability of two or
more events remaining in our sample is 32.6%. The third event
is most likely a radioactive background event caused by thebeta decay of 214Bi from the radon decay chain. This is thedominant background near this energy region (3.6 MeV;
Nakano 2016). The expected number of background events
below 5.5 MeV that survive the reduction cuts is(1.735±0.008); therefore, the probability that one or more
events remains in our sample is 82.4%. The fourth event ismost likely a solar neutrino event because the reconstructed
direction is close to the solar direction (cosine of the angle
between them (cos qSun ) is 0.96 with an angular resolution of
22.9°) and its recoil electron kinetic energy is 11.3 MeV, which
is typical for solar neutrino event. The main background of thisenergy region is spallation events; however, the chance ofaccidental coincidence of these background events with thesolar direction is quite small since the reduction of spallation
events are already fairly efﬁcient. The expected number of solar
neutrino events is (0.229±0.005) from the latest solar
neutrino measurement in SK. The probability of one or more
solar events remaining in our sample is 20.5%.
3The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

Abe et al.

distribution with a background, NT is the number of target
nuclei, σ is the combined cross section for all interactions
particular to that neutrino ﬂavor, ò is the efﬁciency formeasuring the neutrino event in the detector, and λ is thenumber density of the events for a given energy spectrum withan index of −2. This spectral index is commonly used for
astrophysical neutrinos accelerated by shocks (Gaisser et al.
1995). Since no neutrino candidate events pass cuts within the
search window for the FC and PC data sets, we derive N90
using N90 = -ln (0.1) = 2.3. Fluence limits are calculated
separately for each neutrino species by considering the crosssection and detection efﬁciency speciﬁc to the neutrino type.
Cross sections from NEUT 5.3.5 (Hayato 2009) are used in
the calculation of Equation (1). To determine the detector
efﬁciency, mono-energetic neutrino interaction ﬁles producedwith NEUT 5.3.5 are passed as inputs to the SK Monte Carlodetector simulation. The resulting output ﬁles then undergo thesame reconstruction and reduction procedures that are applied
to the data. The efﬁciency is determined by calculating thefraction of remaining events after reduction and selection cuts.
The energy range of 100 MeV–10 GeV is considered.
For the UPMU data set, the neutrino ﬂuence is calculatedusing Equation (2):Figure 2. Reconstructed directions of the charged particle in the remaining four
events associated with GW150914 (black points), shown here with the 90% CL
contour for the location of GW150914 according to LALInterference data. The
shaded area around SK events shows the 1σ angular resolution of the charged
particle corresponding to the energy of each event. The “×” shows the Sun’s
direction at the time of the GW event.

Figure 2 shows the sky map using the reconstructed directionof the charged particle in the remaining four events associatedwith GW150914, along with the 90% CL contour for thelocation of GW150914 according to LALInterference data
(Abbott et al. 2016b). The angular resolution of the charged
particle is calibrated by electron LINAC (Nakahata et al. 1999).
Because the energy spectrum and species of the incoming
neutrinos is not known, an estimate of the angular uncertainty
on the direction of the incoming neutrino is difﬁcult; however,the direction of the charged particle has a strong correlation
with the incident neutrino direction for the case of neutrino–
electron scattering, while a very weak anti-correlation exists inthe case of inverse beta decay (Strumia & Vissani 2003).

FUPMU =In addition to two gravitational-wave signals, LIGO reported
a third binary black hole candidate with a smaller signiﬁcance,
named LVT151012, on 2015 October 12 at 09:54:43 UT(Abbott et al. 2016a). We also searched for a coincident
neutrino signal within a±500 s search window around the
LVT151012 event. No neutrino events are found in the FC, PC,
UPMU, and relic supernova neutrino data sample, while ﬁve
neutrino event candidates remain after applying reduction steps
for the solar neutrino analysis. The probability of ﬁve or more
events remaining in the solar neutrino data sample is calculated
to be 16.8%, which is also consistent with background events.
3. NEUTRINO FLUENCE LIMITThe number of neutrino candidate events observed in the
search window can be converted to an upper limit on neutrino
ﬂuence for both of the gravitational-wave events. This is done
separately for the low-energy, FC+PC, and UPMU data sets.
The procedure used to extract the ﬂuence limit will be
described brieﬂy here, but uses the same prescription laid out
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):N90,
NT ò dEn s (En )  (En ) l (En-2)(2 )Here, ﬂuence depends on the zenith-dependent effective area
(Aeff(z)), where z is the zenith angle of the incoming neutrino,
the probability for a neutrino to create a muon with energy
greater than Enmin (P(Eν)), the shadowing of the neutrinos due
to interactions in the Earth (S (z, En )), and the number density(λ) of the neutrino events for the given energy spectrum withan index of −2. Again, since there are no neutrino candidate
events within the search window for the UPMU data set, we
use N90=2.3. The energy range considered for the UPMU
ﬂuence is 1.6 GeV–100 PeV.
For the low-energy data sample, the neutrino ﬂuencecalculation is similar to Equation (1); however, since there is
no reason to assume a power spectrum nor any reliable theoryof neutrino emission spectrum in this energy region, we set theneutrino energy spectrum to have an index of 0, which is ﬂat.
Therefore, the ﬂuence limit is calculated with the assumption of
ﬂat spectrum of neutrino energy from 3.5 to 75 MeV as shownin Equation (3):2.3. LVT151012

FFC,PC =N90.
A eff (z) ò dEn P (En ) S (z , En ) l (En-2)

Flowe =

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

(3 )where R is the response function from electron or positronenergy (Ee) to the kinetic energy in SK (Evis). The response
function and the detection efﬁciency (ò) is calculated using the
SK detector Monte Carlo simulation. N90 is calculated to be
5.41 (2.30) from the remaining four (zero) neutrino candidate
events compared to the expected 2.90 events in this data sample
for GW150914 (GW151226). The accidental coincidence of
solar neutrinos with a gravitational-wave signal are easily
reduced by a factor of 0.9 with an angular cut on the recoil
electron’s direction (cos qSun > 0.8). In this case, the number ofremaining neutrino candidate events is three (zero) compared to
2.46 expected events, and N90 is 4.64 (2.30) for GW150914(1 )where N90 is the 90% C.L. limit on the number of neutrino
events in the search window calculated using a Poisson
4The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

Abe et al.

Figure 3. The 90% C.L. limit for GW150914 (left) and GW151226 (right) on ﬂuence obtained by mono-energetic neutrinos at different speciﬁc energies from thelow-energy data sample.

(GW151226). In addition, since any emission models for lowenergy neutrinos are not well motivated, we express the ﬂuence
limit that is calculated for monochromatic neutrino energy Eνobtained by replacing λ(Eν) with a delta function d (E - En ).
The ﬂuence limits for both GW events are shown in Figure 3.
Table 1 shows the ﬂuence limit results for the FC+PC,
UPMU, and low-energy data sets for both gravitational-wave
events separately, as well as for both events combined. To
calculate the combined neutrino ﬂuence limit, the N90 is
calculated using the search windows around both gravitationalwave events and is then weighted by the number ofgravitational-wave events, which in this case is two. For the
UPMU events, ﬂuence is dependent on zenith angle, and thus weshow the upper limit of neutrino ﬂuence from UPMU events as asky map of possible ﬂuence limits in Figure 4. Since thegravitational-wave events are not well localized, a combined
ﬂuence limit for the UPMU data set is not reported. The UPMU
upper limit ﬂuence values range from (14–37) cm−2 forneutrinos and from (19–50) cm−2 for antineutrinos, dependingon the direction of the gravitational-wave event. We convert our
UPMU ﬂuence limit to an upper limit on total energy radiated inneutrinos by convolving Equation (2) by the energy spectrum
2
where dGW is the distance between
and weighting by 4pd GW
the detector and the gravitational-wave source. The resulting
upper limit on total energy is Entot ~ (1–6) ´ 10 55 erg for
GW150914 assuming the LIGO-determined distance of
410 Mpc and Entot ~ (2–7) ´ 10 55 erg for GW151226 assuming the LIGO-determined distance of 440 Mpc. For comparison,
the total energy radiated in gravitational waves by GW150914 is∼5×1054 erg (Adrián-Martínez et al. 2016), and the totalenergy radiated in neutrinos from a typical supernova is ∼ a few
×1053 erg (Bethe 1990).

Table 1
Limits at 90% C.L. on the Fluence of Neutrinos from GW150914 and
GW151226 Given a Spectral Index of −2 and an Energy Range of 100 MeV–
10 GeV for the FC+PC and 1.6 GeV−100 PeV for the UPMU Data Samples,and a Flat Spectrum for the Low-energy Data Sample whose Energy Region Is
from 3.5 to 75 MeV
GW150914Φν (cm−2)

GW151226 Fn (cm−2)

CombinedΦν (cm−2)

νμ
n¯m
νe
n¯e

From FC+PC only
5.6×104
1.3×105
4.8×104
1.2×105

5.6×104
1.3×105
4.8×104
1.2×105

2.8×104
6.5×104
2.4×104
6.0×104νμn¯m

From UPMU only
14–37
19–50

14–37
19–50

K
K

n¯e
νe
νx

From low-energy only
4.2/3.6×107
3.0/2.6×109
1.9/1.6×1010

1.8/1.8×107
1.3/1.3×109
8.1/8.1×109

1.6/1.5×107
1.2/1.1×109
7.0/7.0×109

Note.The values on the left/right in the low-energy sample show the ﬂuence
limit without/with the solar direction cut, respectively.

Low-energy neutrino events are also examined using the
SRN and the solar neutrino data samples in the same searchtime window. No neutrino candidate events are found in the
SRN data sample for both gravitational-wave signals. No
neutrino candidate events are found in the solar neutrino data
for GW151226; however, four neutrino candidate events arefound for GW150914. These four events are consistent with theestimated background, with one of them possibly associatedwith solar neutrinos.
The obtained neutrino ﬂuence limits give the most stringent
limits for neutrino emission in the energy region below∼100GeV, assuming an E−2 spectrum from GW150914 and
GW151226. The absence of MeV neutrino emission in thesolar neutrino and the SRN data samples is inconsistent withthe source of the gravitational-wave signals being a nearby
core-collapsed astronomical object.

4. CONCLUSION
We search for possible neutrino signals coincident with
GW150914, GW151226, and LVT151012 in the SK detector
using a wide energy range from 3.5 MeV to 100PeV. In thehigh-energy data sample, three neutrino interaction categories
are considered: FC, PC, and UPMU. No neutrino candidate
events are found in the search window of±500 s around the
LIGO detection time for both gravitational-wave signals.
5The Astrophysical Journal Letters, 830:L11 (6pp), 2016 October 10

Abe et al.

Figure 4. The 90% C.L. limit on ﬂuence for neutrinos considering only the UPMU data set, overlaid with the 90% C.L. contour for the location of the gravitationalwave event according to LALInterference data (solid blue line). The upper (lower) panel shows the information for GW150914 (GW151226), and the left (right) panel
shows the information for neutrinos (antineutrinos). For this limit, an energy range of 1.6 GeV–100 PeV was used.

We gratefully acknowledge the cooperation of the Kamioka
Mining and Smelting Company. The Super-Kamiokande experiment has been built and operated from funding by the Japanese
Ministry of Education, Culture, Sports, Science and Technology,
the U.S. Department of Energy, and the U.S. National Science
Foundation. Some of us have been supported by funds from the
Korean Research Foundation (BK21 and KNRC), the National
Research Foundation of Korea (NRF-20110024009), the European Union (H2020 RISE-GA641540-SKPLUS), the Japan
Society for the Promotion of Science, the National Natural
Science Foundation of China under grant No. 11235006, and theScinet and Westgrid consortia of Compute Canada.

Adrián-Martínez, S., Albert, A., André, M., et al. 2016, PhRvD, 93, 122010
Ashie, Y., Hosaka, J., Ishihara, K., et al. 2005, PhRvD, 71, 112005
Bays, K., Iida, T., Abe, K., et al. 2012, PhRvD, 85, 052007
Bethe, H. A. 1990, RvMP, 62, 801
Connaughton, V., Burns, E., Goldstein, A., et al. 2016, ApJL, 826, L6
Eichler, D., Livio, M., Piran, T., & Schramm, D. N. 1989, Natur, 340, 126
Fukuda, S., Fukuda, Y., Hayakawa, T., et al. 2003, NIMPA, 501, 418
Gaisser, T. K., Halzen, F., & Stanev, T. 1995, PhR, 258, 173 [Erratum: 1996,
PhR, 271, 355]
Gando, A., Gando, Y., Hachiya, T., et al. 2016, arXiv:1606.07155
Greiner, J., Burgess, J. M., Savchenko, V., & Yu, H.-F. 2016, arXiv:1606.
00314
Hayato, Y. 2009, AcPP, B40, 2477
Nakahata, M., Fukuda, Y., Hayakawa, T., et al. 1999, NIMPA, 421, 113
Nakano, Y. 2016, PhD thesis, Univ. Tokyo
Strumia, A., & Vissani, F. 2003, PhLB, 564, 42
Swanson, M. E. C., Abe, K., Hosaka, J., et al. 2006, ApJ, 652, 206
Thrane, E., Abe, K., Hayato, Y., et al. 2009, ApJ, 704, 503
Woosley, S. E. 1993, ApJ, 405, 273
Yamada, S., Awai, K., Hayato, Y., et al. 2009, ITNS, 57, 428
Zhang, H., Abe, K., Hayato, Y., et al. 2015, APh, 60, 41
Zhang, Y., Abe, K., Haga, Y., et al. 2016, PhRvD, 93, 012004

REFERENCES
Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2016a, PhRvL, 116, 241103
Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2016b, ApJL, 826, L13
Abbott, B. P., Abbott, R., Abbott, T. D., et al. 2016c, PhRvL, 116, 061102
Abe, K., Haga, Y., Hayato, Y., et al. 2016, PhRvD, 94, 052010

6