of 14
Search for transient gravitational waves in coincidence with short-duration
radio transients during 2007
2013
B. P. Abbott
etal.
*
(LIGO Scientific Collaboration and Virgo Collaboration)
(Received 11 May 2016; published 20 June 2016)
We present an archival search for transient gravitational-wave bursts in coincidence with 27 single-pulse
triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo, and GEO interferometer
network. We also discuss a check for gravitational-wave signals in coincidence with Parkes fast radio bursts
using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Possible
sources of emission of both short-duration radio signals and transient gravitational-wave emission include
starquakes on neutron stars, binary coalescence of neutron stars, and cosmic string cusps. While no evidence
for gravitational-wave emission in coincidence with these radio transients was found, the current analysis
serves as a prototype for similar future searches using more sensitive second-generation interferometers.
DOI:
10.1103/PhysRevD.93.122008
I. INTRODUCTION
Plausible models for coincident or near-coincident emis-
sion of both radio and gravitational-wave (GW) transients
exist for a number of astrophysical phenomena, including
single neutron stars, merging neutron star binaries, and
cosmicstring cusps.Identificationof a GWin close temporal
and spatial coincidence with a fast radio burst or other radio
transient could place significant constraints on the source
of emission, with further constraints possible based on
the morphology of the gravitational-wave signal. In this
paper, we present a search for GWs in coincidence with
millisecond-scale duration radio transient pulses. We have
conducted externally triggered searches for gravitational
waves with the LIGO/Virgo/GEO network in coincidence
with both Galactic single-pulse pulsar candidates from the
Green Bank Telescope and a sample of cosmological fast
radio burst (FRB) candidates from the Parkes Telescope.
Individual radio pulses range from 1 to tens of ms in duration
and were observed in frequency bands from hundreds of
MHz to 1 GHz. The LIGO Scientific Collaboration (LSC)
and Virgo Collaboration regularly search for continuous
gravitational waves arriving from the direction of known
radiopulsars (see, e.g., Refs.
[1,2]
forrecent examples), and a
search for gravitational waves in coincidence with a Vela
pulsar glitch was conducted previously
[3]
.
The present work marks the first LIGO/Virgo search
in coincidence with radio transients and serves as a
prototype for searches with advanced interferometers.
Given that the origin of these radio transients is currently
unclear, our analysis is designed to search broadly for a
gravitational-wave transient burst, without requiring a
specific type of waveform.
The paper is organized asfollows. After briefly describing
the network of gravitational-wave interferometers used in
this analysis in Sec.
II
, we discuss possible mechanisms
leading to joint emission of
few hundred Hz gravitational
waves and radio transient signals. We describe the radio data
used in the analysis in Sec.
IV
, followed by the gravitational-
wave search methods and results in Secs.
V
and
VI
,
respectively. We conclude with a discussion of future
prospects for joint analysis of radio and gravitational-wave
data in Sec.
VII
.
II. GRAVITATIONAL-WAVE
INTERFEROMETER NETWORK
The LIGO Scientific Collaboration and Virgo
Collaboration operate a network of power-recycled
Fabry-Perot Michelson interferometers designed to be
sensitive to very small relative changes in length (on the
order of one part in
10
21
) of the two orthogonal detector
arms. LIGO operates two sites in the United States, one in
Livingston Parish, Louisiana, and another at the Hanford
site in Washington. Both LIGO facilities operate an
interferometer with an arm length of 4 km (called L1
and H1, respectively), and Hanford operated an additional
smaller, collocated interferometer (H2) until September
2007
[4]
. The LIGO Scientific Collaboration also operates
a 600 m interferometer, GEO 600, near Hannover,
Germany (G1)
[5]
. The Virgo Collaboration operates a
single 3 km interferometer near Cascina, Italy (V1)
[6]
.
Since this paper involves the analysis of radio transients
across a period of several years of initial detector data,
multiple science runs of these interferometers are used.
Data analyzed in this paper are drawn from summer 2007,
coincident with LIGO
s fifth and Virgo
s first science run,
as well as late 2009, coincident with LIGO
s sixth and
Virgo
s third science run. FRB candidates discussed in this
paper are coincident with GEO 600 Astrowatch data
ranging from 2011 to 2013 and in some cases Virgo
s
fourth science run, which took place in summer 2011. See
*
Full author list given at end of the article.
PHYSICAL REVIEW D
93,
122008 (2016)
2470-0010
=
2016
=
93(12)
=
122008(14)
122008-1
© 2016 American Physical Society
Ref.
[7]
for a comparison of sensitivities for these instru-
ments from 2007 to 2014.
The LIGO/Virgo network has undergone extensive
upgrades to second-generation instruments and during
the first Advanced LIGO observation run made the first
direct detection of a gravitational-wave transient
[8]
. After
reaching design sensitivity, the Advanced LIGO
[9]
and
Advanced Virgo
[10]
detectors will have an order of
magnitude improvement in range relative to their first-
generation counterparts. Additional advanced interferom-
eters are scheduled to join the global network in the future,
including Kagra in Japan
[11]
and a third LIGO site in
India
[12]
.
III. POTENTIAL SOURCES OF JOINT RADIO
AND GRAVITATIONAL-WAVE EMISSION
There are a number of astrophysical phenomena that
may plausibly produce gravitational waves in close coinci-
dence with radio frequency emission. We focus this
discussion on a few types of sources which may produce
both GWs and radio pulses with frequency and duration
suitable to the instruments being used in this analysis. More
detailed discussion can be found in Ref.
[13]
.
A. Single neutron stars
Transient gravitational-wave emission can occur when
a temporary deformation of a rapidly rotating neutron star
creates a quadrupolar moment. Typically, this is believed
to happen as a result of crust cracking from magnetic,
gravitational or superfluid forces, dubbed a starquake
[14,15]
; or from other asteroseismic phenomena result-
ing in the shifting of the neutron star
scrust
[16]
.
Asteroseismology may result in several types of quasi-
normal oscillatory modes of the neutron star which could
produce GW emission. These include torsional modes at
low frequencies
[17]
and the f-mode, with GW emission
believed to typically peak around 2 kHz
[18]
.The
amplitude of the GW emission even in optimistic cases,
however, is small enough that sensitivity to this type of
source will be limited to our own Galaxy even in the
advanced detector era.
Radio pulsars result from beamed emission from the
poles of a rapidly rotating, highly magnetized neutron star
sweeping past the Earth, producing reliably periodic radio
signals. The asteroseismic events described above may
result in a distinct increase in the rotation rates of these
neutron stars, typically followed by a gradual return to their
original period. This phenomenon, called a pulsar glitch,
has been observed across a large number of pulsars,
especially younger ones (see, e.g., Ref.
[19]
and references
therein). A search for gravitational-wave emission from
quasinormal modes in coincidence with the observed
glitching of pulsars was the subject of a previous LSC
publication
[3]
. Models for neutron star asteroseismic
phenomena similar to those under discussion have also
motivated previous gravitational-wave searches in coinci-
dence with soft gamma repeater flares
[20]
.
A related phenomenon to radio pulsars is the rotating
radio transient (RRAT). RRATs emit short-duration radio
pulses similar in character to pulsars but are distinguished
by their lack of predictable periodic behavior. RRATs may
be
dying
pulsars near the end of their life cycles, neutron
stars with especially high magnetization, or conventional
pulsars of which the observation is often obscured by
intervening matter between the pulsar and Earth, although
it is also possible that other phenomena may manifest
observationally as RRATs
[21]
.
The standard indication of an asteroseismic event in an
isolated neutron star is a pulsar glitch, but there are
plausible mechanisms that could result in the observation
of a transient radio pulse. This could simply be through the
pulsar radio emission coming into view from the Earth as
the pulsar
s orbit shifts slightly, but there is also some
evidence that pulsarlike radio emission can be
switched
on
in coincidence with a glitching mechanism
[22
24]
.
For some models, gravitational waves emitted by neutron
stars are predicted to be detectable at a distance scale on the
order of kiloparsecs with first generation of interferometers.
We therefore consider single neutron stars as possible
sources of coincident GW and radio transient events.
B. Binary neutron star coalescence
The most easily observable transient gravitational-wave
signature in the frequency range of LIGO and Virgo is the
merger of a binary system of compact objects, specifically
neutron stars or black holes. In the final moments before the
compact objects merge, the upward sweep in frequency of
the gravitational wave emission is predicted to produce a
characteristic chirplike signal. Recent evidence suggests
that neutron star binary mergers may create at least some
fraction of FRBs
[25]
.
Compact binary coalescence is currently the only con-
firmed source of directly detectable gravitational waves
[8]
.
Once design sensitivity is reached in the advanced detector
era, the ground-based network of interferometers is pre-
dicted to detect several to a few hundred binary coalescence
GW signals per year of operation
[26]
.
There are several models for radio emission in coinci-
dence with a compact binary coalescence GW signal. This
may be pulsarlike radio emission, either from the reac-
tivation of the dormant pulsar emission in one of the
neutron stars through interactions prior to merger
[27]
or by
a hypermassive neutron star, which may sometimes be
produced as an intermediate state before collapse to a black
hole
[28]
. Another possible mechanism is the radiation at
radio frequencies as a result of magnetospheric inter-
actions
[29]
.
Given an appropriate density in the surrounding envi-
ronment, the gravitational waves emitted by a compact
B. P. ABBOTT
et al.
PHYSICAL REVIEW D
93,
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122008-2
binary coalescence may induce electromagnetic radiation
through magnetohydrodynamic interactions. While this
interaction would directly produce radiation at the same
relatively low frequencies as the GWs themselves, up-
conversion through inverse Compton radiation may result
in emission at radio frequencies
[30]
. This particular
magnetohydrodynamic mechanism does not necessarily
require neutron star coalescence as the mechanism for
production of the GWs, but this class of source is likely to
be able to produce GWs of suitable amplitude and may be
surrounded by an environment suitable to this mecha-
nism
[31]
.
While the sensitivity of the LIGO/Virgo network to
gravitational waves from compact binary coalescence sce-
narios is dependent on the mass, spin, and other properties of
themergingobjects,interferometersintheinitialdetectorera
weretypicallysensitivetomergersoftwoneutronstarsoutto
a distance on the order of 10 Mpcs
[26]
.
C. Cosmic strings
Cosmic strings, formed during symmetry breaking in the
early Universe, are topological defects thought to be
capable of emitting large amounts of energy from their
cusps or kinks
[32]
. A cosmic string cusp may emit
gravitational waves with a
f
4
=
3
frequency dependence
up to a cutoff frequency
[33]
, potentially at frequencies and
amplitudes detectable by ground-based interferometers
[34,35]
. The same cusps may produce short-duration
linearly polarized radio bursts
[36]
, a mechanism that
has previously been proposed as the origin of the original
Lorimer burst
[37]
. Unlike GWs from other sources
discussed, cosmic string cusps could theoretically produce
detectable GWs at cosmological distances, which makes
them particularly interesting in the context of Parkes FRBs
with dispersion measures (DMs) indicative of cosmological
distances.
D. Other potential sources
The three classes of sources resulting in simultaneous
GW and radio emission described above are not an
exhaustive list of theoretical joint sources, but most other
types of sources are outside the scope of the analyses
described in this paper due to the frequency or duration of
the predicted GW and/or radio emission not being well
suited to the instruments described in this analysis. For
example, some scenarios in which gamma-ray bursts
(GRBs) may also result in radio emission are not explicitly
considered in developing this analysis; prompt radio
emission models
[38,39]
predict signals at much lower
frequencies than the Green Bank and Parkes telescopes can
detect, and GRB radio afterglows
[40]
occur on longer time
scales inconsistent with the short radio pulses that are the
subject of the searches described in this paper. Core-
collapse supernovae have also been proposed as plausible
sources of short-duration radio pulses
[22]
and GW
emission. However, we do not explicitly include super-
novae among the classes of emission for which we are
searching when designing the analysis as there are no
observed nearby core-collapse supernovae in close coinci-
dence with the radio transients under consideration.
IV. RADIO PULSE DATA
A. Green Bank single-pulse analysis data
The Robert C. Byrd Green Bank Telescope is the world
s
largest fully steerable single-dish radio telescope. In the
summer of 2007 a drift-scan pulsar survey was conducted
in a band of
350

25
MHz
[41]
. This time frame was
during Initial LIGO
s fifth science run and Initial Virgo
s
first science run. In addition to the identification of
continuously observable pulsars, a
single-pulse
archival
search was performed to look for transient emission of
millisecond-scale duration radio pulses. The drift-scan
team provided LIGO/Virgo with 33 of these observed
single-pulse triggers, ten of which were confirmed to
originate from sources with repeated emission through
followup observations, thus most likely originating from a
pulsar or RRAT. Some of the triggers exhibited only a
single radio pulse, while others show several pulses within
a 2 min window, but in order to be considered a viable
astrophysical signal, all pulses were required to exhibit the
1
=f
2
dispersion behavior expected as a result of dispersion
in the interstellar medium.
For each of the 33 candidates, right ascension, declina-
tion, dispersion measure, and arrival time at solar system
barycenter were provided. The dispersion measures pro-
vided (between 15 and
170
pc cm
3
) are in general con-
sistent with a population of sources from within our own
Galaxy. For purposes of the gravitational-wave search,
barycentric arrival times were adjusted to UTC arrival times
at the detector using code previously applied to LIGO
pulsar analyses
[2]
and cross-checked against conversions
to the detector frame provided by Green Bank for a subset
of triggers.
A survey of the Galaxy
s Northern Celestial Cap was
conducted with the Green Bank Telescope in 2009 and
2010
[42]
. The single-pulse analysis searching for RRATs
or related phenomena was more automated than in the drift-
scan analysis and resulted in seven published candidates
being reported. These radio triggers corresponded to Initial
LIGO
s sixth and Initial Virgo
s third science runs and were
treated identically to drift-scan triggers for GW analysis
purposes.
B. Parkes fast radio bursts
The report of FRBs originating from apparently cosmo-
logical distances
[43
45]
has led to an increased interest in
short-duration radio transients. These radio transients
resemble the original Lorimer burst
[46]
reported by
Parkes in 2007. Since then, Arecibo and Green Bank have
SEARCH FOR TRANSIENT GRAVITATIONAL WAVES IN
...
PHYSICAL REVIEW D
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122008-3
each reported an FRB
[47,48]
. The origin of these FRBs is
unclear, with several possible astrophysical sources and
terrestrial backgrounds posited as the origin of these radio
bursts. Recent followup observations of the Arecibo burst
in particular indicate it is a repeating phenomenon
[49]
,
which substantially narrows the range of plausible sources.
An observed correlation with another astrophysical signal
would do much to clarify the nature of these bursts and help
confirm their nature as a previously unknown astrophysical
phenomenon.
The FRBs of interest for a gravitational-wave search
(i.e., omitting bursts from 2001, prior to the construction
of sensitive GW interferometers) have observed fluences
ranging from 0.55 to 7.3 Jy ms, observed width from 0.64
to 15.6 ms, and dispersion measures suggesting cosmo-
logical origin, ranging from 563 to
1629
pc cm
3
[50]
.
While most of these FRBs did not occur during
LIGO/Virgo science runs, we performed a check in the
Virgo science run data and GEO 600 Astrowatch data when
available.
Given the difference in the dispersion measure and other
properties, the FRBs are most likely primarily a distinct
class of sources compared to the RRAT-like observations in
the previous section. Current evidence points to an astro-
physical origin, especially as known perytons exhibit
properties distinct from FRBs
[51]
. Several of the emission
mechanisms discussed in Sec.
III
are considered viable
candidate progenitors, including neutron star and compact
binary coalescing systems
[52
54]
.
C. Short duration radio transients not analyzed
Potential FRBs from sources other than the above were
considered but were not coincident with an active network
of GW interferometers. In some cases, this was because
they occurred during times before sensitive GW data were
available
[55,56]
. This includes the original Lorimer burst
[46]
. Neither radio transient reported to be observed in
coincidence with a GRB in Ref.
[57]
was coincident with
LIGO/Virgo data
[58]
. The first observation of Arecibo
s
reported FRB
[48,49]
occurred during the LIGO and Virgo
network upgrade to advanced interferometers and fell
during a time in which GEO 600 was not collecting science
data as part of its Astrowatch program, with published
followup observations also occurring prior to the first
Advanced LIGO observation run. Although FRB110523,
identified by Green Bank Telescope
[47]
, occurred during
Initial Virgo
s fourth science run, Virgo was not taking data
at the time of the event.
V. ANALYSIS METHOD
A. Procedure
The search for gravitational waves in coincidence with
short radio transients was conducted using the X-P
IPELINE
analysis package
[59]
. This software has been used for a
number of GW searches in coincidence with astrophysical
triggers. The analysis procedure for this search was
modeled directly after conceptually similar searches for
GWs in coincidence with gamma-ray bursts
[58,60]
, but the
parameters were modified to account for the particular
types of GW sources under consideration. Similar adjust-
ments between GRB and radio transient searches can be
used to design radio transient searches in advanced
interferometers.
For each radio trigger analyzed, we use X-P
IPELINE
to
conduct a coherent search for a GW signal consistent with
the location and time of the radio signal. The physical
locations of the individual GW interferometers in the
network and the antenna patterns based on their orienta-
tions are used to reject potential GW signals that are not
consistent with the radio signal
s sky location, and
only signals within

2
minutes of the radio trigger
are considered. Coherent and incoherent energy combina-
tions are calculated for each potential trigger, and a series
of two-dimensional cuts is applied to reject triggers
physically inconsistent with a GW. The false alarm prob-
ability of any surviving triggers after all cuts is estimated
based on the
time-lag
method. This utilizes interfero-
metric data outside but near the on-source window but
introduces hundreds of artificial time offsets between the
interferometers that are much larger than the time of flight
of a real GW signal in order to obtain statistics on the
significance of background in which no coherent signal is
present. These procedures are discussed in more detail in
Ref.
[58]
, with adjustments for our specific analysis as
described below.
B. Analysis-specific search parameters
Our frequency range, temporal and spatial coincidence
windows, veto methods, and other parameters were
selected to handle a range of possible astrophysical
emission mechanisms consistent with short radio pulses
as discussed in Sec.
III
. Where allowed by calibration
[61]
,
the frequency range was between 64 Hz and approximately
3 kHz. The majority of GW searches cut off at 2 kHz due to
rising shot noise and increased computational costs at
higher frequency. However, increasing the upper frequency
range for this analysis allows us to include a large subset of
possible GW emission from single neutron stars. This
increase in frequency also requires us to perform the search
over a much denser grid of points on the sky, but the
excellent spatial resolution of radio telescopes relative to
many other astrophysical observations makes this adjust-
ment feasible.
The on-source time window when searching for GW
signals around the radio pulse was taken to be

120
s
around the observed radio pulse. While it is difficult to
exhaustively cover all possible scenarios for time separa-
tion between radio and GW emission, the time window
selected covers the offsets between emission for the range
B. P. ABBOTT
et al.
PHYSICAL REVIEW D
93,
122008 (2016)
122008-4
of scenarios informing the design of the analysis. Since the
radio pulse arrival times are corrected for dispersion, there
is very little additional uncertainty in the time-of-flight
difference between the two types of emission. For analyses
in coincidence with Green Bank triggers, the angular
uncertainty on the sky is taken to be 0.55 deg. This
accounts for two effects, including 95% of Green
Bank
s total beam width for a 350 MHz signal and
including a small adjustment for the drift of the source
across the sky during the time span over which X-P
IPELINE
conducts a test for a self-consistent GW signal.
UnlikerecentGWsearchesincoincidencewithGRBsthat
used similar procedures
[60]
, our background vetoing pro-
ceduresdonotrelyontheassumptionthattheGWsignalwill
becircularlypolarized.Whilethisisareasonableassumption
for signalsin coincidencewithgamma-raybursts,thegreater
variety of possible astrophysical sources we consider in this
analysis does not justify this assumption.
C. Simulated waveforms
While we do not require a particular signal morphology
for our gravitational wave signal, we tune the analysis and
characterize its performance based on an ensemble of
simulated waveforms. These ten waveforms include:
(i) damped sinusoids at peak frequencies of 1750 and
2300 Hz and decay time constants of 0.26 and
0.13 s, respectively, representing typical emission
expected from neutron star asteroseismic events
under different assumptions for the neutron star
equation of state
[18]
;
(ii) cosmic string cusp waveforms with upper frequency
limits of 300 and 1000 Hz;
(iii) linearly polarized Gaussian-envelope sine waves at
central frequencies of 235 and 945 Hz with a quality
factor of 9;
(iv) circularly polarized Gaussian-envelope sine waves at
central frequencies of 150 and 300 Hz, also with a
quality factor of 9;
TABLE I. Analyzed Green Bank Telescope single-pulse candidates.
90% C.L. upper limit
ð
h
rss
×
10
22
Hz
1
2
Þ
Trigger name
Modified
Julian day
(geocentric)
Right
ascension
Declination
Dispersion
measure
(pc cm
3
)
Interferometer
network
150 Hz
sinusoid
Neutron
star-neutron
star
1750 Hz
sinusoid
RRAT 1704-0440 54240.38329
17
h
04
m
54
:
4
s
4
°
40
0
37
.
9
00
43

1
H1H2L1V1
3.51
4.08
18.6
RRAT 1537+2350 54243.25237
15
h
37
m
47
:
4
s
23
°
50
0
51
.
1
00
15

1
H1H2L1V1
2.33
2.91
10.5
RRAT 1636+0131 54317.05160
16
h
36
m
19
:
4
s
01
°
31
0
07
.
1
00
30

2
H1H2L1V1
3.03
3.60
31.7
RRAT 1651+0130 54317.06177
16
h
51
m
42
:
0
s
01
°
30
0
57
.
4
00
29

1
H1H2L1V1
3.21
3.91
27.8
RRAT 0206-0443 54239.76133
02
h
06
m
11
:
0
s
04
°
43
0
33
.
4
00
15

1
H1H2L1V1
4.17
5.29
23.2
RRAT 0801-0746 54289.78625
08
h
01
m
37
:
5
s
07
°
47
0
03
.
2
00
38

1
H1H2L1V1
3.85
4.24
193.
RRAT 0808-0746 54289.79101
08
h
08
m
43
:
3
s
07
°
46
0
58
.
9
00
36

1
H1H2L1V1
3.55
4.32
72.5
RRAT 0858-0746 54289.82543
08
h
58
m
23
:
9
s
07
°
46
0
31
.
4
00
40

3
H1H2L1V1
4.35
4.32
14.4
RRAT 0719-1907 54296.74455
07
h
19
m
38
:
3
s
19
°
07
0
30
.
2
00
27

1
H1H2L1V1
3.96
4.66
21.8
RRAT 2324-0507 54240.64681
23
h
24
m
22
:
2
s
05
°
07
0
36
.
0
00
15

1
H1H2V1
6.09
5.95
28.6
RRAT 2006+2021 54272.36809
20
h
06
m
54
:
8
s
20
°
21
0
05
.
8
00
66

1
H1H2V1
6.01
6.77
17.4
RRAT 1610-0128 54268.26252
16
h
10
m
58
:
4
s
01
°
28
0
04
.
0
00
27

1
H1H2V1
5.90
6.71
21.7
RRAT 0706-1058 54315.66206
07
h
06
m
43
:
2
s
10
°
58
0
20
.
3
00
19

1
H1H2V1
5.21
5.79
25.6
RRAT 0606-0129 54267.84394
06
h
06
m
37
:
5
s
01
°
29
0
23
.
9
00
17

3
H1H2V1
5.86
5.89
25.2
RRAT 0645-0128 54267.87160
06
h
45
m
39
:
5
s
01
°
28
0
58
.
1
00
15

2
H1H2V1
5.14
5.65
24.2
RRAT 1336-2034 54294.01362
13
h
36
m
28
:
2
s
20
°
34
0
21
.
8
00
19

1
H1H2V1
5.63
5.98
25.1
RRAT 0526-1908 54296.66537
05
h
26
m
04
:
9
s
19
°
08
0
48
.
8
00
26

2
H1H2V1
5.64
5.90
25.0
RRAT 1926+2021 54272.33975
19
h
26
m
41
:
9
s
20
°
21
0
29
.
1
00
21

1
H2L1V1
7.39
115.
17.5
RRAT 1914-1129 54315.16846
19
h
14
m
46
:
3
s
11
°
29
0
33
.
5
00
91

1
H1H2L1
3.01
3.32
15.4
RRAT 1132+2455 54228.11976
11
h
32
m
09
:
2
s
24
°
55
0
58
.
7
00
24

1
H1H2L1
2.65
2.90
12.8
RRAT 1059-0102 54274.03007
10
h
59
m
31
:
9
s
01
°
02
0
01
.
6
00
18

1
H1L1V1
4.35
5.67
70.5
RRAT 1944-1017 54281.29872
19
h
44
m
08
:
6
s
10
°
17
0
07
.
2
00
31

1
H1H2L1
2.84
3.33
15.6
RRAT 0807-1057 54315.70287
08
h
07
m
02
:
7
s
10
°
57
0
41
.
4
00
18

1
H1H2
5.66
5.39
22.8
RRAT 0614-0328 54224.97146
6
h
14
m
37
:
8
s
3
°
28
0
44
.
9
00
18

1
H1L1
2.50
3.06
1062
RRAT 0544-0309 54226.94475
5
h
44
m
46
:
3
s
3
°
9
0
44
.
8
00
67

1
H1L1
2.51
3.05
165.0
GBNCC 04413
55163.27053
2
h
3
m
27
:
6
s
70
°
22
0
43
.
7
00
21

1
H1V1
5.78
5.55
328.0
GBNCC 04743
55169.16190
0
h
53
m
24
:
0
s
69
°
38
0
45
.
2
00
90

1
H1V1
8.43
9.03
138.0
SEARCH FOR TRANSIENT GRAVITATIONAL WAVES IN
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PHYSICAL REVIEW D
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(v) a compact binary coalescence signal from merging
1.4 solar mass neutron stars;
(vi) a compact binary coalescence signal from a 1.4 solar
mass neutron star and a 50 solar mass black hole.
These waveforms were selected to broadly represent the
types of gravitational wave signals that may occur in
coincidence with radio pulses without focusing too heavily
on a specific morphology. In addition, the last three
waveform types describe specific signals used in previous
LIGO searches in order to facilitate sensitivity comparisons
with previous work.
VI. ANALYSIS RESULTS
A. Green Bank pulsar surveys
Of the 33 single-pulse radio candidates from the
Green Bank drift-scan survey, 25 were analyzable with
at least three interferometers in the LIGO/Virgo network.
Of the seven RRAT candidates identified in the Northern
Celestial Cap survey, only two were analyzable with
two or more interferometers in the gravitational wave
network.
None of these 27 radio pulses resulted in viable GW
candidates. The most significant result for a single
candidate was a 2.7% single trial false alarm probability
for RRAT 1944-1017, which is completely consistent
with background for an ensemble of 27 trials. Table
I
shows information about each radio candidate, including
information about the radio source, as well as GW
network and upper limits on h
rss
(root sum squared
strain) for three of the simulated GW waveforms. The
last two entries in the table are the Northern Celestial
Cap survey triggers.
In addition to individual analysis of the radio candidates,
we also perform a weighted binomial test of the p-value
distribution of the most significant surviving trigger from
the GWanalysis, using the same methodology as employed
previously in searches for GWs in coincidence with GRBs
[7,58]
. This distribution is plotted against expectation in
Fig.
1
. The test yields a background probability of 30%,
which is consistent with the null hypothesis.
Possible association between GRBs and FRBs has been
widely discussed (see, e.g., Refs.
[25,57,62,63]
), with
indications that at least a subset of radio bursts may be
coupled with gamma-ray bursts. We therefore follow
previous LIGO analyses
[60]
and calculate 90% confidence
level exclusion distances, for two of our simulated circu-
larly polarized waveforms, assuming an optimistic standard
siren in which
1%
of a solar mass is converted to
gravitational-wave energy. A histogram of these distance
constraints is shown in Fig.
2
. In general, limits in the few
to tens of Mpc range indicate that we would be sensitive to
a GW signal under these assumptions well outside of our
own Galaxy, but at substantially less than the cosmological
distances measured for FRBs. For the 150 Hz sine-
Gaussian waveform, using standard calculations
[64]
about
4
×
10
52
ergs of energy would have to be emitted for a
detectable source emitting isotropically at a distance
of 20 Mpc.
FIG. 1. Cumulative distribution of p-values from the analysis of
27 radio triggers from Green Bank for evidence of a GW transient
associated with the event. The expected distribution in the
absence of a signal is indicated by the dashed line. Points at
p-value of unity are triggers with no event in the on-source region
after selection cuts.
FIG. 2. Histograms for the sample of Green Bank radio
transients of distance exclusions at 90% confidence level for
possible GRBs associated with radio transients. Waveforms are
circularly polarized sine-Gaussian GW burst models with central
frequency of 150 and 300 Hz.
B. P. ABBOTT
et al.
PHYSICAL REVIEW D
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B. Parkes telescope FRBs
We examined a list of 14 FRBs
[50]
from Parkes,
occurring as early as 2001 but primarily concentrated
within the last five years. While none of the event times
corresponded to science runs for Hanford or Livingston,
eight of the FRBs corresponded to times when GEO 600
Astrowatch data were available, and two of these also
corresponded to data from Initial Virgo
s fourth science
run. After omitting two of these FRBs for which GEO
data were too nonstationary to yield a quality GW
analysis, we searched for GWs in coincidence with a
total of six Parkes FRBs. Analysis parameters were kept
as similar as feasible to the Green Bank drift-scan
analysis described previously. However, the upper end
of the frequency range was lowered to 1764 Hz due to
the range over which GEO data are calibrated
[7]
,
and the higher frequency damped sinusoids were left
out of the set of GW morphologies simulated. Since the
triggers are nominally at cosmological distances and we
are unlikely to be sensitive to damped sinusoid-type
signals from neutron stars outside our own Galaxy, this
limitation is not a major concern.
There was no evidence of a gravitational-wave signal for
any of these FRBs (the most significant single trial p-value
was 0.07), although it should be noted that the smaller GEO
interferometer is less sensitive than the larger interferom-
eters. As such we treat this analysis primarily as a check for
loud candidates and do not quote sensitivity upper limits for
this search. Instead a list of currently published FRBs
without evidence for corresponding GW emission is given
in Table
II
. Since these are not consistent in terms of DM or
other characteristics with the RRAT-like candidates iden-
tified by Green Bank, we do not include these in the
binomial test or other distributional studies presented in
Figs.
1
and
2
.
VII. CONCLUSIONS AND FUTURE PROSPECTS
The searches described in this current paper should be
viewed largely as prototypes for future searches with
instruments that will eventually be an order of magnitude
more sensitive than the best sensitivities presented here.
Since much is currently unknown about FRBs and related
phenomena, identification of a GW in close coincidence
with a radio burst could provide insight into both the
distance and, depending on the GW morphology, astro-
physical origin of the radio transient.
In addition to more sensitive searches in coincidence
with fast radio bursts, efforts are also underway within the
LIGO and Virgo collaborations to analyze radio transients
of longer durations resulting from instruments operating at
lower frequency than the Green Bank or Parkes telescopes.
Since these transients have properties very different than
the ones described here and are not generally expected to
come from the same sources, substantially different analy-
sis methods are required to address searches for GWs in
coincidence with these signals
[65]
.
In the case of fast radio bursts, it is worth noting that
arguments based on the Parkes field of view and observa-
tion time suggest that if FRBs are in fact of astrophysical
origin, the vast majority of FRBs are currently missed by
radio telescopes
[45,66]
. Accounting for possible anisot-
ropies in the distribution of FRBs and including both mid-
galactic and high-latitude survey data, the all-sky rate for
FRBs is estimated to be between 1100 to 9600 FRBs per
day above a threshold fluence of 4.0 Jy ms
[67]
. While
externally triggered searches can look for signals with
amplitudes of as much as
3
lower than all-sky searches
[68]
, if such a population of FRBs generated detectable
gravitational-wave signals, statistical arguments suggest
they would be likely to show up in all-sky transient
searches (e.g., Ref.
[69]
) as well. However, these detections
would not be clearly associated with a FRB and thus lack
the ability of a multimessenger search in constraining
the possible source of FRBs. In the coming years, statistical
information on FRBs is likely to be dramatically improved,
especially as wider field radio instruments come online
[70
72]
.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the support of the
United States National Science Foundation (NSF) for
the construction and operation of the LIGO Laboratory
and Advanced LIGO as well as the Science and Technology
Facilities Council (STFC) of the United Kingdom,
TABLE II. Analyzed FRB candidates from the Parkes telescope. No evidence of gravitational-wave emission was observed in
coincidence with these FRBs.
Trigger name Modified Julian day (geocentric) Right ascension Declination Dispersion measure (pc cm
3
) Interferometer network
FRB 110626
55738.89810
21
h
03
m
43
s
44
°
44
0
19
00
723.0
G1V1
FRB 110703
55745.79142
23
h
30
m
51
s
02
°
52
0
24
00
1103.6
G1V1
FRB 110220
55612.08041
22
h
34
m
38
:
2
s
12
°
33
0
44
00
944.8
G1
FRB 120127
55953.34122
23
h
15
m
6
.
3
s
18
°
25
0
37
00
555.2
G1
FRB 130628
56471.16527
9
h
03
m
2
.
5
s
3
°
26
0
16
00
469.7
G1
FRB 131104
56600.75279
6
h
44
m
10
:
4
s
51
°
16
0
40
00
779.3
G1
SEARCH FOR TRANSIENT GRAVITATIONAL WAVES IN
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PHYSICAL REVIEW D
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the Max-Planck-Society (MPS), and the State of
Niedersachsen/Germany for support of the construction
of Advanced LIGO and construction and operation of the
GEO600 detector. Additional support for Advanced LIGO
was provided by the Australian Research Council. The
authors gratefully acknowledge the Italian Istituto
Nazionale di Fisica Nucleare (INFN), the French Centre
National de la Recherche Scientifique (CNRS), and the
Foundation for Fundamental Research on Matter supported
by Netherlands Organisation for Scientific Research for the
construction and operation of the Virgo detector and the
creation and support of the EGO consortium. The authors
also gratefully acknowledge research support from these
agencies as well as by the Council of Scientific and
Industrial Research of India, Department of Science and
Technology, India; Science and Engineering Research
Board (SERB), India; Ministry of Human Resource
Development, India; the Spanish Ministerio de Economía
y Competitividad; the Conselleria d
Economia i
Competitivitat and Conselleria d
Educació; Cultura i
Universitats of the Govern de les Illes Balears; the
National Science Centre of Poland; the European
Commission; the Royal Society; the Scottish Funding
Council; the Scottish Universities Physics Alliance; the
Hungarian Scientific Research Fund (OTKA); the Lyon
Institute of Origins (LIO); the National Research
Foundation of Korea; Industry Canada and the Province
of Ontario through the Ministry of Economic Development
and Innovation; the Natural Science and Engineering
Research Council Canada; Canadian Institute for
Advanced Research; the Brazilian Ministry of Science,
Technology, and Innovation; Russian Foundation for
Basic Research; the Leverhulme Trust, the Research
Corporation, Ministry of Science and Technology
(MOST), Taiwan; and the Kavli Foundation. Some authors
were supported by the European Research Council, includ-
ing Grant No. 617199 to J. v. L. The authors gratefully
acknowledge the support of the NSF, STFC, MPS, INFN,
CNRS, and the State of Niedersachsen/Germany for provi-
sion of computational resources.
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53
G. Bogaert,
53
C. Bogan,
9
A. Bohe,
30
P. Bojtos,
54
C. Bond,
45
F. Bondu,
55
R. Bonnand,
7
B. A. Boom,
10
R. Bork,
1
V. Boschi,
19,20
S. Bose,
56,15
Y. Bouffanais,
31
A. Bozzi,
35
C. Bradaschia,
20
P. R. Brady,
17
V. B. Braginsky,
49
M. Branchesi,
57,58
J. E. Brau,
59
T. Briant,
60
A. Brillet,
53
M. Brinkmann,
9
V. Brisson,
24
P. Brockill,
17
A. F. Brooks,
1
D. A. Brown,
36
D. D. Brown,
45
N. M. Brown,
11
C. C. Buchanan,
2
A. Buikema,
11
T. Bulik,
61
H. J. Bulten,
62,10
A. Buonanno,
30,63
D. Buskulic,
7
C. Buy,
31
R. L. Byer,
41
L. Cadonati,
64
G. Cagnoli,
65,66
C. Cahillane,
1
J. Calderón Bustillo,
67,64
T. Callister,
1
E. Calloni,
68,4
J. B. Camp,
69
K. C. Cannon,
70
J. Cao,
71
C. D. Capano,
9
E. Capocasa,
31
F. Carbognani,
35
S. Caride,
72
J. Casanueva Diaz,
24
C. Casentini,
26,14
S. Caudill,
17
M. Cavaglià,
22
F. Cavalier,
24
R. Cavalieri,
35
G. Cella,
20
C. B. Cepeda,
1
L. Cerboni Baiardi,
57,58
G. Cerretani,
19,20
E. Cesarini,
26,14
R. Chakraborty,
1
T. Chalermsongsak,
1
S. J. Chamberlin,
17
M. Chan,
37
S. Chao,
73
P. Charlton,
74
E. Chassande-Mottin,
31
H. Y. Chen,
75
Y. Chen,
76
C. Cheng,
73
A. Chincarini,
47
A. Chiummo,
35
H. S. Cho,
77
M. Cho,
63
J. H. Chow,
21
N. Christensen,
78
Q. Chu,
51
S. Chua,
60
S. Chung,
51
G. Ciani,
5
F. Clara,
38
J. A. Clark,
64
F. Cleva,
53
E. Coccia,
26,13
P.-F. Cohadon,
60
A. Colla,
79,29
C. G. Collette,
80
L. Cominsky,
81
M. Constancio Jr.,
12
A. Conte,
79,29
L. Conti,
43
D. Cook,
38
T. R. Corbitt,
2
N. Cornish,
32
A. Corsi,
82
S. Cortese,
35
C. A. Costa,
12
M. W. Coughlin,
78
S. B. Coughlin,
83
J.-P. Coulon,
53
S. T. Countryman,
40
P. Couvares,
1
D. M. Coward,
51
M. J. Cowart,
6
D. C. Coyne,
1
R. Coyne,
82
K. Craig,
37
J. D. E. Creighton,
17
J. Cripe,
2
S. G. Crowder,
84
A. Cumming,
37
SEARCH FOR TRANSIENT GRAVITATIONAL WAVES IN
...
PHYSICAL REVIEW D
93,
122008 (2016)
122008-9
L. Cunningham,
37
E. Cuoco,
35
T. Dal Canton,
9
S. L. Danilishin,
37
S. D
Antonio,
14
K. Danzmann,
18,9
N. S. Darman,
85
V. Dattilo,
35
I. Dave,
48
H. P. Daveloza,
86
M. Davier,
24
G. S. Davies,
37
E. J. Daw,
87
R. Day,
35
D. DeBra,
41
G. Debreczeni,
39
J. Degallaix,
65
M. De Laurentis,
68,4
S. Deléglise,
60
W. Del Pozzo,
45
T. Denker,
9,18
T. Dent,
9
V. Dergachev,
1
R. De Rosa,
68,4
R. T. DeRosa,
6
R. DeSalvo,
8
S. Dhurandhar,
15
M. C. Díaz,
86
L. Di Fiore,
4
M. Di Giovanni,
88,89
T. Di Girolamo,
68,4
A. Di Lieto,
19,20
S. Di Pace,
79,29
I. Di Palma,
30,9
A. Di Virgilio,
20
G. Dojcinoski,
90
V. Dolique,
65
F. Donovan,
11
K. L. Dooley,
22
S. Doravari,
6
R. Douglas,
37
T. P. Downes,
17
M. Drago,
9
R. W. P. Drever,
1
J. C. Driggers,
38
Z. Du,
71
M. Ducrot,
7
S. E. Dwyer,
38
T. B. Edo,
87
M. C. Edwards,
78
A. Effler,
6
H.-B. Eggenstein,
9
P. Ehrens,
1
J. Eichholz,
5
S. S. Eikenberry,
5
W. Engels,
76
R. C. Essick,
11
T. Etzel,
1
M. Evans,
11
T. M. Evans,
6
R. Everett,
91
M. Factourovich,
40
V. Fafone,
26,14
H. Fair,
36
S. Fairhurst,
83
X. Fan,
71
Q. Fang,
51
S. Farinon,
47
B. Farr,
75
W. M. Farr,
45
M. Favata,
90
M. Fays,
83
H. Fehrmann,
9
M. M. Fejer,
41
I. Ferrante,
19,20
E. C. Ferreira,
12
F. Ferrini,
35
F. Fidecaro,
19,20
I. Fiori,
35
D. Fiorucci,
31
R. P. Fisher,
36
R. Flaminio,
65,92
M. Fletcher,
37
J.-D. Fournier,
53
S. Frasca,
79,29
F. Frasconi,
20
Z. Frei,
54
A. Freise,
45
R. Frey,
59
V. Frey,
24
T. T. Fricke,
9
P. Fritschel,
11
V. V. Frolov,
6
P. Fulda,
5
M. Fyffe,
6
H. A. G. Gabbard,
22
J. R. Gair,
93
L. Gammaitoni,
33
S. G. Gaonkar,
15
F. Garufi,
68,4
G. Gaur,
94,95
N. Gehrels,
69
G. Gemme,
47
E. Genin,
35
A. Gennai,
20
J. George,
48
L. Gergely,
96
V. Germain,
7
Archisman Ghosh,
16
S. Ghosh,
52,10
J. A. Giaime,
2,6
K. D. Giardina,
6
A. Giazotto,
20
K. Gill,
97
A. Glaefke,
37
E. Goetz,
72
R. Goetz,
5
L. Gondan,
54
G. González,
2
J. M. Gonzalez Castro,
19,20
A. Gopakumar,
98
N. A. Gordon,
37
M. L. Gorodetsky,
49
S. E. Gossan,
1
M. Gosselin,
35
R. Gouaty,
7
A. Grado,
99,4
C. Graef,
37
P. B. Graff,
69,63
M. Granata,
65
A. Grant,
37
S. Gras,
11
C. Gray,
38
G. Greco,
57,58
A. C. Green,
45
P. Groot,
52
H. Grote,
9
S. Grunewald,
30
G. M. Guidi,
57,58
X. Guo,
71
A. Gupta,
15
M. K. Gupta,
95
K. E. Gushwa,
1
E. K. Gustafson,
1
R. Gustafson,
72
J. J. Hacker,
23
B. R. Hall,
56
E. D. Hall,
1
G. Hammond,
37
M. Haney,
98
M. M. Hanke,
9
J. Hanks,
38
C. Hanna,
91
M. D. Hannam,
83
J. Hanson,
6
T. Hardwick,
2
J. Harms,
57,58
G. M. Harry,
100
I. W. Harry,
30
M. J. Hart,
37
M. T. Hartman,
5
C.-J. Haster,
45
K. Haughian,
37
A. Heidmann,
60
M. C. Heintze,
5,6
H. Heitmann,
53
P. Hello,
24
G. Hemming,
35
M. Hendry,
37
I. S. Heng,
37
J. Hennig,
37
A. W. Heptonstall,
1
M. Heurs,
9,18
S. Hild,
37
D. Hoak,
101,35
K. A. Hodge,
1
D. Hofman,
65
S. E. Hollitt,
102
K. Holt,
6
D. E. Holz,
75
P. Hopkins,
83
D. J. Hosken,
102
J. Hough,
37
E. A. Houston,
37
E. J. Howell,
51
Y. M. Hu,
37
S. Huang,
73
E. A. Huerta,
103
D. Huet,
24
B. Hughey,
97
S. Husa,
67
S. H. Huttner,
37
T. Huynh-Dinh,
6
A. Idrisy,
91
N. Indik,
9
D. R. Ingram,
38
R. Inta,
82
H. N. Isa,
37
J.-M. Isac,
60
M. Isi,
1
G. Islas,
23
T. Isogai,
11
B. R. Iyer,
16
K. Izumi,
38
T. Jacqmin,
60
H. Jang,
77
K. Jani,
64
P. Jaranowski,
104
S. Jawahar,
105
F. Jiménez-Forteza,
67
W. W. Johnson,
2
D. I. Jones,
27
R. Jones,
37
R. J. G. Jonker,
10
L. Ju,
51
Haris K.,
106
C. V. Kalaghatgi,
25
V. Kalogera,
107
S. Kandhasamy,
22
G. Kang,
77
J. B. Kanner,
1
S. Karki,
59
M. Kasprzack,
2,35
E. Katsavounidis,
11
W. Katzman,
6
S. Kaufer,
18
T. Kaur,
51
K. Kawabe,
38
F. Kawazoe,
9
F. Kéfélian,
53
M. S. Kehl,
70
D. Keitel,
9
D. B. Kelley,
36
W. Kells,
1
R. Kennedy,
87
J. S. Key,
86
A. Khalaidovski,
9
F. Y. Khalili,
49
I. Khan,
13
S. Khan,
83
Z. Khan,
95
E. A. Khazanov,
108
N. Kijbunchoo,
38
Chunglee Kim,
77
J. Kim,
109
K. Kim,
110
Nam-Gyu Kim,
77
Namjun Kim,
41
Y.-M. Kim,
109
E. J. King,
102
P. J. King,
38
D. L. Kinzel,
6
J. S. Kissel,
38
L. Kleybolte,
28
S. Klimenko,
5
S. M. Koehlenbeck,
9
K. Kokeyama,
2
S. Koley,
10
V. Kondrashov,
1
A. Kontos,
11
M. Korobko,
28
W. Z. Korth,
1
I. Kowalska,
61
D. B. Kozak,
1
V. Kringel,
9
A. Królak,
111,112
C. Krueger,
18
G. Kuehn,
9
P. Kumar,
70
L. Kuo,
73
A. Kutynia,
111
B. D. Lackey,
36
M. Landry,
38
J. Lange,
113
B. Lantz,
41
P. D. Lasky,
114
A. Lazzarini,
1
C. Lazzaro,
64,43
P. Leaci,
79,29
S. Leavey,
37
E. O. Lebigot,
31,71
C. H. Lee,
109
H. K. Lee,
110
H. M. Lee,
115
K. Lee,
37
A. Lenon,
36
M. Leonardi,
88,89
J. R. Leong,
9
N. Leroy,
24
N. Letendre,
7
Y. Levin,
114
B. M. Levine,
38
T. G. F. Li,
1
A. Libson,
11
T. B. Littenberg,
116
N. A. Lockerbie,
105
J. Logue,
37
A. L. Lombardi,
101
J. E. Lord,
36
M. Lorenzini,
13,14
V. Loriette,
117
M. Lormand,
6
G. Losurdo,
58
J. D. Lough,
9,18
H. Lück,
18,9
A. P. Lundgren,
9
J. Luo,
78
R. Lynch,
11
Y. Ma,
51
T. MacDonald,
41
B. Machenschalk,
9
M. MacInnis,
11
D. M. Macleod,
2
F. Magaña-Sandoval,
36
R. M. Magee,
56
M. Mageswaran,
1
E. Majorana,
29
I. Maksimovic,
117
V. Malvezzi,
26,14
N. Man,
53
V. Mandic,
84
V. Mangano,
37
G. L. Mansell,
21
M. Manske,
17
M. Mantovani,
35
F. Marchesoni,
118,34
F. Marion,
7
S. Márka,
40
Z. Márka,
40
A. S. Markosyan,
41
E. Maros,
1
F. Martelli,
57,58
L. Martellini,
53
I. W. Martin,
37
R. M. Martin,
5
D. V. Martynov,
1
J. N. Marx,
1
K. Mason,
11
A. Masserot,
7
T. J. Massinger,
36
M. Masso-Reid,
37
S. Mastrogiovanni,
79,29
F. Matichard,
11
L. Matone,
40
N. Mavalvala,
11
N. Mazumder,
56
G. Mazzolo,
9
R. McCarthy,
38
D. E. McClelland,
21
S. McCormick,
6
S. C. McGuire,
119
G. McIntyre,
1
J. McIver,
101
D. J. McManus,
21
S. T. McWilliams,
103
D. Meacher,
53
G. D. Meadors,
30,9
J. Meidam,
10
A. Melatos,
85
G. Mendell,
38
D. Mendoza-Gandara,
9
R. A. Mercer,
17
E. L. Merilh,
38
M. Merzougui,
53
S. Meshkov,
1
C. Messenger,
37
C. Messick,
91
R. Metzdorff,
60
P. M. Meyers,
84
F. Mezzani,
29,79
H. Miao,
45
C. Michel,
65
H. Middleton,
45
E. E. Mikhailov,
120
L. Milano,
68,4
A. L. Miller,
5,79,29
J. Miller,
11
M. Millhouse,
32
Y. Minenkov,
14
J. Ming,
30,9
S. Mirshekari,
121
C. Mishra,
16
S. Mitra,
15
V. P. Mitrofanov,
49
G. Mitselmakher,
5
R. Mittleman,
11
A. Moggi,
20
M. Mohan,
35
S. R. P. Mohapatra,
11
M. Montani,
57,58
B. C. Moore,
90
C. J. Moore,
122
D. Moraru,
38
G. Moreno,
38
S. R. Morriss,
86
K. Mossavi,
9
B. Mours,
7
B. P. ABBOTT
et al.
PHYSICAL REVIEW D
93,
122008 (2016)
122008-10