arXiv:1902.08442v2 [gr-qc] 25 Feb 2019
LIGO-P1800391
Narrow-band search for gravitational waves from known puls
ars using the second
LIGO observing run
B. P. Abbott,
1
R. Abbott,
1
T. D. Abbott,
2
S. Abraham,
3
F. Acernese,
4, 5
K. Ackley,
6
C. Adams,
7
R. X. Adhikari,
1
V. B. Adya,
8, 9
C. Affeldt,
8, 9
M. Agathos,
10
K. Agatsuma,
11
N. Aggarwal,
12
O. D. Aguiar,
13
L. Aiello,
14, 15
A. Ain,
3
P. Ajith,
16
G. Allen,
17
A. Allocca,
18, 19
M. A. Aloy,
20
P. A. Altin,
21
A. Amato,
22
A. Ananyeva,
1
S. B. Anderson,
1
W. G. Anderson,
23
S. V. Angelova,
24
S. Antier,
25
S. Appert,
1
K. Arai,
1
M. C. Araya,
1
J. S. Areeda,
26
M. Ar`ene,
27
N. Arnaud,
25, 28
S. Ascenzi,
29, 30
G. Ashton,
6
S. M. Aston,
7
P. Astone,
31
F. Aubin,
32
P. Aufmuth,
9
K. AultONeal,
33
C. Austin,
2
V. Avendano,
34
A. Avila-Alvarez,
26
S. Babak,
35, 27
P. Bacon,
27
F. Badaracco,
14,15
M. K. M. Bader,
36
S. Bae,
37
P. T. Baker,
38
F. Baldaccini,
39, 40
G. Ballardin,
28
S. W. Ballmer,
41
S. Banagiri,
42
J. C. Barayoga,
1
S. E. Barclay,
43
B. C. Barish,
1
D. Barker,
44
K. Barkett,
45
S. Barnum,
12
F. Barone,
4,5
B. Barr,
43
L. Barsotti,
12
M. Barsuglia,
27
D. Barta,
46
J. Bartlett,
44
I. Bartos,
47
R. Bassiri,
48
A. Basti,
18, 19
M. Bawaj,
49, 40
J. C. Bayley,
43
M. Bazzan,
50, 51
B. B ́ecsy,
52
M. Bejger,
27, 53
I. Belahcene,
25
A. S. Bell,
43
D. Beniwal,
54
B. K. Berger,
48
G. Bergmann,
8, 9
S. Bernuzzi,
55, 56
J. J. Bero,
57
C. P. L. Berry,
58
D. Bersanetti,
59
A. Bertolini,
36
J. Betzwieser,
7
R. Bhandare,
60
J. Bidler,
26
I. A. Bilenko,
61
S. A. Bilgili,
38
G. Billingsley,
1
J. Birch,
7
R. Birney,
24
O. Birnholtz,
57
S. Biscans,
1, 12
S. Biscoveanu,
6
A. Bisht,
9
M. Bitossi,
28, 19
M. A. Bizouard,
25
J. K. Blackburn,
1
C. D. Blair,
7
D. G. Blair,
62
R. M. Blair,
44
S. Bloemen,
63
N. Bode,
8, 9
M. Boer,
64
Y. Boetzel,
65
G. Bogaert,
64
F. Bondu,
66
E. Bonilla,
48
R. Bonnand,
32
P. Booker,
8,9
B. A. Boom,
36
C. D. Booth,
67
R. Bork,
1
V. Boschi,
28
S. Bose,
68, 3
K. Bossie,
7
V. Bossilkov,
62
J. Bosveld,
62
Y. Bouffanais,
27
A. Bozzi,
28
C. Bradaschia,
19
P. R. Brady,
23
A. Bramley,
7
M. Branchesi,
14,15
J. E. Brau,
69
T. Briant,
70
J. H. Briggs,
43
F. Brighenti,
71, 72
A. Brillet,
64
M. Brinkmann,
8, 9
V. Brisson,
25,
∗
P. Brockill,
23
A. F. Brooks,
1
D. D. Brown,
54
S. Brunett,
1
A. Buikema,
12
T. Bulik,
73
H. J. Bulten,
74, 36
A. Buonanno,
35, 75
D. Buskulic,
32
C. Buy,
27
R. L. Byer,
48
M. Cabero,
8,9
L. Cadonati,
76
G. Cagnoli,
22, 77
C. Cahillane,
1
J. Calder ́on Bustillo,
6
T. A. Callister,
1
E. Calloni,
78, 5
J. B. Camp,
79
W. A. Campbell,
6
M. Canepa,
80, 59
K. C. Cannon,
81
H. Cao,
54
J. Cao,
82
E. Capocasa,
27
F. Carbognani,
28
S. Caride,
83
M. F. Carney,
58
G. Carullo,
18
J. Casanueva Diaz,
19
C. Casentini,
29, 30
S. Caudill,
36
M. Cavagli`a,
84
F. Cavalier,
25
R. Cavalieri,
28
G. Cella,
19
P. Cerd ́a-Dur ́an,
20
G. Cerretani,
18, 19
E. Cesarini,
85, 30
O. Chaibi,
64
K. Chakravarti,
3
S. J. Chamberlin,
86
M. Chan,
43
S. Chao,
87
P. Charlton,
88
E. A. Chase,
58
E. Chassande-Mottin,
27
D. Chatterjee,
23
M. Chaturvedi,
60
B. D. Cheeseboro,
38
H. Y. Chen,
89
X. Chen,
62
Y. Chen,
45
H.-P. Cheng,
47
C. K. Cheong,
90
H. Y. Chia,
47
A. Chincarini,
59
A. Chiummo,
28
G. Cho,
91
H. S. Cho,
92
M. Cho,
75
N. Christensen,
64, 93
Q. Chu,
62
S. Chua,
70
K. W. Chung,
90
S. Chung,
62
G. Ciani,
50, 51
A. A. Ciobanu,
54
R. Ciolfi,
94, 95
F. Cipriano,
64
A. Cirone,
80, 59
F. Clara,
44
J. A. Clark,
76
P. Clearwater,
96
F. Cleva,
64
C. Cocchieri,
84
E. Coccia,
14, 15
P.-F. Cohadon,
70
D. Cohen,
25
R. Colgan,
97
M. Colleoni,
98
C. G. Collette,
99
C. Collins,
11
L. R. Cominsky,
100
M. Constancio Jr.,
13
L. Conti,
51
S. J. Cooper,
11
P. Corban,
7
T. R. Corbitt,
2
I. Cordero-Carri ́on,
101
K. R. Corley,
97
N. Cornish,
52
A. Corsi,
83
S. Cortese,
28
C. A. Costa,
13
R. Cotesta,
35
M. W. Coughlin,
1
S. B. Coughlin,
67, 58
J.-P. Coulon,
64
S. T. Countryman,
97
P. Couvares,
1
P. B. Covas,
98
E. E. Cowan,
76
D. M. Coward,
62
M. J. Cowart,
7
D. C. Coyne,
1
R. Coyne,
102
J. D. E. Creighton,
23
T. D. Creighton,
103
J. Cripe,
2
M. Croquette,
70
S. G. Crowder,
104
T. J. Cullen,
2
A. Cumming,
43
L. Cunningham,
43
E. Cuoco,
28
T. Dal Canton,
79
G. D ́alya,
105
S. L. Danilishin,
8, 9
S. D’Antonio,
30
K. Danzmann,
9, 8
A. Dasgupta,
106
C. F. Da Silva Costa,
47
L. E. H. Datrier,
43
V. Dattilo,
28
I. Dave,
60
M. Davier,
25
D. Davis,
41
E. J. Daw,
107
D. DeBra,
48
M. Deenadayalan,
3
J. Degallaix,
22
M. De Laurentis,
78, 5
S. Del ́eglise,
70
W. Del Pozzo,
18,19
L. M. DeMarchi,
58
N. Demos,
12
T. Dent,
8, 9, 108
R. De Pietri,
109, 56
J. Derby,
26
R. De Rosa,
78, 5
C. De Rossi,
22, 28
R. DeSalvo,
110
O. de Varona,
8, 9
S. Dhurandhar,
3
M. C. D ́ıaz,
103
T. Dietrich,
36
L. Di Fiore,
5
M. Di Giovanni,
111, 95
T. Di Girolamo,
78,5
A. Di Lieto,
18, 19
B. Ding,
99
S. Di Pace,
112, 31
I. Di Palma,
112, 31
F. Di Renzo,
18, 19
A. Dmitriev,
11
Z. Doctor,
89
F. Donovan,
12
K. L. Dooley,
67, 84
S. Doravari,
8,9
I. Dorrington,
67
T. P. Downes,
23
M. Drago,
14, 15
J. C. Driggers,
44
Z. Du,
82
J.-G. Ducoin,
25
P. Dupej,
43
S. E. Dwyer,
44
P. J. Easter,
6
T. B. Edo,
107
M. C. Edwards,
93
A. Effler,
7
P. Ehrens,
1
J. Eichholz,
1
S. S. Eikenberry,
47
M. Eisenmann,
32
R. A. Eisenstein,
12
R. C. Essick,
89
H. Estelles,
98
D. Estevez,
32
Z. B. Etienne,
38
T. Etzel,
1
M. Evans,
12
T. M. Evans,
7
V. Fafone,
29, 30, 14
H. Fair,
41
S. Fairhurst,
67
X. Fan,
82
S. Farinon,
59
B. Farr,
69
W. M. Farr,
11
E. J. Fauchon-Jones,
67
M. Favata,
34
M. Fays,
107
M. Fazio,
113
C. Fee,
114
J. Feicht,
1
M. M. Fejer,
48
F. Feng,
27
A. Fernandez-Galiana,
12
I. Ferrante,
18,19
E. C. Ferreira,
13
T. A. Ferreira,
13
F. Ferrini,
28
F. Fidecaro,
18, 19
I. Fiori,
28
D. Fiorucci,
27
M. Fishbach,
89
R. P. Fisher,
41, 115
J. M. Fishner,
12
M. Fitz-Axen,
42
R. Flaminio,
32, 116
M. Fletcher,
43
E. Flynn,
26
H. Fong,
117
J. A. Font,
20, 118
P. W. F. Forsyth,
21
J.-D. Fournier,
64
S. Frasca,
112, 31
F. Frasconi,
19
Z. Frei,
105
A. Freise,
11
R. Frey,
69
V. Frey,
25
P. Fritschel,
12
V. V. Frolov,
7
P. Fulda,
47
M. Fyffe,
7
H. A. Gabbard,
43
2
B. U. Gadre,
3
S. M. Gaebel,
11
J. R. Gair,
119
L. Gammaitoni,
39
M. R. Ganija,
54
S. G. Gaonkar,
3
A. Garcia,
26
C. Garc ́ıa-Quir ́os,
98
F. Garufi,
78, 5
B. Gateley,
44
S. Gaudio,
33
G. Gaur,
120
V. Gayathri,
121
G. Gemme,
59
E. Genin,
28
A. Gennai,
19
D. George,
17
J. George,
60
L. Gergely,
122
V. Germain,
32
S. Ghonge,
76
Abhirup Ghosh,
16
Archisman Ghosh,
36
S. Ghosh,
23
B. Giacomazzo,
111,95
J. A. Giaime,
2, 7
K. D. Giardina,
7
A. Giazotto,
19,
†
K. Gill,
33
G. Giordano,
4,5
L. Glover,
110
P. Godwin,
86
E. Goetz,
44
R. Goetz,
47
B. Goncharov,
6
G. Gonz ́alez,
2
J. M. Gonzalez Castro,
18, 19
A. Gopakumar,
123
M. L. Gorodetsky,
61
S. E. Gossan,
1
M. Gosselin,
28
R. Gouaty,
32
A. Grado,
124, 5
C. Graef,
43
M. Granata,
22
A. Grant,
43
S. Gras,
12
P. Grassia,
1
C. Gray,
44
R. Gray,
43
G. Greco,
71, 72
A. C. Green,
11, 47
R. Green,
67
E. M. Gretarsson,
33
P. Groot,
63
H. Grote,
67
S. Grunewald,
35
P. Gruning,
25
G. M. Guidi,
71, 72
H. K. Gulati,
106
Y. Guo,
36
A. Gupta,
86
M. K. Gupta,
106
E. K. Gustafson,
1
R. Gustafson,
125
L. Haegel,
98
O. Halim,
15, 14
B. R. Hall,
68
E. D. Hall,
12
E. Z. Hamilton,
67
G. Hammond,
43
M. Haney,
65
M. M. Hanke,
8, 9
J. Hanks,
44
C. Hanna,
86
O. A. Hannuksela,
90
J. Hanson,
7
T. Hardwick,
2
K. Haris,
16
J. Harms,
14, 15
G. M. Harry,
126
I. W. Harry,
35
C.-J. Haster,
117
K. Haughian,
43
F. J. Hayes,
43
J. Healy,
57
A. Heidmann,
70
M. C. Heintze,
7
H. Heitmann,
64
P. Hello,
25
G. Hemming,
28
M. Hendry,
43
I. S. Heng,
43
J. Hennig,
8, 9
A. W. Heptonstall,
1
Francisco Hernandez Vivanco,
6
M. Heurs,
8, 9
S. Hild,
43
T. Hinderer,
127, 36, 128
D. Hoak,
28
S. Hochheim,
8, 9
D. Hofman,
22
A. M. Holgado,
17
N. A. Holland,
21
K. Holt,
7
D. E. Holz,
89
P. Hopkins,
67
C. Horst,
23
J. Hough,
43
E. J. Howell,
62
C. G. Hoy,
67
A. Hreibi,
64
E. A. Huerta,
17
D. Huet,
25
B. Hughey,
33
M. Hulko,
1
S. Husa,
98
S. H. Huttner,
43
T. Huynh-Dinh,
7
B. Idzkowski,
73
A. Iess,
29, 30
C. Ingram,
54
R. Inta,
83
G. Intini,
112, 31
B. Irwin,
114
H. N. Isa,
43
J.-M. Isac,
70
M. Isi,
1
B. R. Iyer,
16
K. Izumi,
44
T. Jacqmin,
70
S. J. Jadhav,
129
K. Jani,
76
N. N. Janthalur,
129
P. Jaranowski,
130
A. C. Jenkins,
131
J. Jiang,
47
D. S. Johnson,
17
A. W. Jones,
11
D. I. Jones,
132
R. Jones,
43
R. J. G. Jonker,
36
L. Ju,
62
J. Junker,
8,9
C. V. Kalaghatgi,
67
V. Kalogera,
58
B. Kamai,
1
S. Kandhasamy,
84
G. Kang,
37
J. B. Kanner,
1
S. J. Kapadia,
23
S. Karki,
69
K. S. Karvinen,
8,9
R. Kashyap,
16
M. Kasprzack,
1
S. Katsanevas,
28
E. Katsavounidis,
12
W. Katzman,
7
S. Kaufer,
9
K. Kawabe,
44
N. V. Keerthana,
3
F. K ́ef ́elian,
64
D. Keitel,
43
R. Kennedy,
107
J. S. Key,
133
F. Y. Khalili,
61
H. Khan,
26
I. Khan,
14, 30
S. Khan,
8, 9
Z. Khan,
106
E. A. Khazanov,
134
M. Khursheed,
60
N. Kijbunchoo,
21
Chunglee Kim,
135
J. C. Kim,
136
K. Kim,
90
W. Kim,
54
W. S. Kim,
137
Y.-M. Kim,
138
C. Kimball,
58
E. J. King,
54
P. J. King,
44
M. Kinley-Hanlon,
126
R. Kirchhoff,
8, 9
J. S. Kissel,
44
L. Kleybolte,
139
J. H. Klika,
23
S. Klimenko,
47
T. D. Knowles,
38
P. Koch,
8, 9
S. M. Koehlenbeck,
8, 9
G. Koekoek,
36, 140
S. Koley,
36
V. Kondrashov,
1
A. Kontos,
12
N. Koper,
8, 9
M. Korobko,
139
W. Z. Korth,
1
I. Kowalska,
73
D. B. Kozak,
1
V. Kringel,
8, 9
N. Krishnendu,
141
A. Kr ́olak,
142,143
G. Kuehn,
8, 9
A. Kumar,
129
P. Kumar,
144
R. Kumar,
106
S. Kumar,
16
L. Kuo,
87
A. Kutynia,
142
S. Kwang,
23
B. D. Lackey,
35
K. H. Lai,
90
T. L. Lam,
90
M. Landry,
44
B. B. Lane,
12
R. N. Lang,
145
J. Lange,
57
B. Lantz,
48
R. K. Lanza,
12
A. Lartaux-Vollard,
25
P. D. Lasky,
6
M. Laxen,
7
A. Lazzarini,
1
C. Lazzaro,
51
P. Leaci,
112, 31
S. Leavey,
8,9
Y. K. Lecoeuche,
44
C. H. Lee,
92
H. K. Lee,
146
H. M. Lee,
147
H. W. Lee,
136
J. Lee,
91
K. Lee,
43
J. Lehmann,
8, 9
A. Lenon,
38
N. Leroy,
25
N. Letendre,
32
Y. Levin,
6, 97
J. Li,
82
K. J. L. Li,
90
T. G. F. Li,
90
X. Li,
45
F. Lin,
6
F. Linde,
36
S. D. Linker,
110
T. B. Littenberg,
148
J. Liu,
62
X. Liu,
23
R. K. L. Lo,
90, 1
N. A. Lockerbie,
24
L. T. London,
67
A. Longo,
149, 150
M. Lorenzini,
14, 15
V. Loriette,
151
M. Lormand,
7
G. Losurdo,
19
J. D. Lough,
8, 9
G. Lovelace,
26
M. E. Lower,
152
H. L ̈uck,
9, 8
D. Lumaca,
29, 30
A. P. Lundgren,
153
R. Lynch,
12
Y. Ma,
45
R. Macas,
67
S. Macfoy,
24
M. MacInnis,
12
D. M. Macleod,
67
A. Macquet,
64
F. Maga ̃na-Sandoval,
41
L. Maga ̃na Zertuche,
84
R. M. Magee,
86
E. Majorana,
31
I. Maksimovic,
151
A. Malik,
60
N. Man,
64
V. Mandic,
42
V. Mangano,
43
G. L. Mansell,
44, 12
M. Manske,
23, 21
M. Mantovani,
28
F. Marchesoni,
49,40
F. Marion,
32
S. M ́arka,
97
Z. M ́arka,
97
C. Markakis,
10, 17
A. S. Markosyan,
48
A. Markowitz,
1
E. Maros,
1
A. Marquina,
101
S. Marsat,
35
F. Martelli,
71, 72
I. W. Martin,
43
R. M. Martin,
34
D. V. Martynov,
11
K. Mason,
12
E. Massera,
107
A. Masserot,
32
T. J. Massinger,
1
M. Masso-Reid,
43
S. Mastrogiovanni,
112,31
A. Matas,
42, 35
F. Matichard,
1, 12
L. Matone,
97
N. Mavalvala,
12
N. Mazumder,
68
J. J. McCann,
62
R. McCarthy,
44
D. E. McClelland,
21
S. McCormick,
7
L. McCuller,
12
S. C. McGuire,
154
J. McIver,
1
D. J. McManus,
21
T. McRae,
21
S. T. McWilliams,
38
D. Meacher,
86
G. D. Meadors,
6
M. Mehmet,
8, 9
A. K. Mehta,
16
J. Meidam,
36
A. Melatos,
96
G. Mendell,
44
R. A. Mercer,
23
L. Mereni,
22
E. L. Merilh,
44
M. Merzougui,
64
S. Meshkov,
1
C. Messenger,
43
C. Messick,
86
R. Metzdorff,
70
P. M. Meyers,
96
H. Miao,
11
C. Michel,
22
H. Middleton,
96
E. E. Mikhailov,
155
L. Milano,
78, 5
A. L. Miller,
47
A. Miller,
112, 31
M. Millhouse,
52
J. C. Mills,
67
M. C. Milovich-Goff,
110
O. Minazzoli,
64, 156
Y. Minenkov,
30
A. Mishkin,
47
C. Mishra,
157
T. Mistry,
107
S. Mitra,
3
V. P. Mitrofanov,
61
G. Mitselmakher,
47
R. Mittleman,
12
G. Mo,
93
D. Moffa,
114
K. Mogushi,
84
S. R. P. Mohapatra,
12
M. Montani,
71, 72
C. J. Moore,
10
D. Moraru,
44
G. Moreno,
44
S. Morisaki,
81
B. Mours,
32
C. M. Mow-Lowry,
11
Arunava Mukherjee,
8, 9
D. Mukherjee,
23
S. Mukherjee,
103
N. Mukund,
3
A. Mullavey,
7
J. Munch,
54
E. A. Mu ̃niz,
41
M. Muratore,
33
P. G. Murray,
43, 158, 159
I. Nardecchia,
29,30
L. Naticchioni,
112, 31
R. K. Nayak,
160
J. Neilson,
110
G. Nelemans,
63, 36
T. J. N. Nelson,
7
M. Nery,
8, 9
A. Neunzert,
125
K. Y. Ng,
12
S. Ng,
54
3
P. Nguyen,
69
D. Nichols,
127, 36
S. Nissanke,
127, 36
F. Nocera,
28
C. North,
67
L. K. Nuttall,
153
M. Obergaulinger,
20
J. Oberling,
44
B. D. O’Brien,
47
G. D. O’Dea,
110
G. H. Ogin,
161
J. J. Oh,
137
S. H. Oh,
137
F. Ohme,
8, 9
H. Ohta,
81
M. A. Okada,
13
M. Oliver,
98
P. Oppermann,
8, 9
Richard J. Oram,
7
B. O’Reilly,
7
R. G. Ormiston,
42
L. F. Ortega,
47
R. O’Shaughnessy,
57
S. Ossokine,
35
D. J. Ottaway,
54
H. Overmier,
7
B. J. Owen,
83
A. E. Pace,
86
G. Pagano,
18,19
M. A. Page,
62
A. Pai,
121
S. A. Pai,
60
J. R. Palamos,
69
O. Palashov,
134
C. Palomba,
31
A. Pal-Singh,
139
Huang-Wei Pan,
87
B. Pang,
45
P. T. H. Pang,
90
C. Pankow,
58
F. Pannarale,
112,31
B. C. Pant,
60
F. Paoletti,
19
A. Paoli,
28
A. Parida,
3
W. Parker,
7,154
D. Pascucci,
43
A. Pasqualetti,
28
R. Passaquieti,
18,19
D. Passuello,
19
M. Patil,
143
B. Patricelli,
18, 19
B. L. Pearlstone,
43
C. Pedersen,
67
M. Pedraza,
1
R. Pedurand,
22, 162
A. Pele,
7
S. Penn,
163
C. J. Perez,
44
A. Perreca,
111,95
H. P. Pfeiffer,
35, 117
M. Phelps,
8, 9
K. S. Phukon,
3
O. J. Piccinni,
112, 31
M. Pichot,
64
F. Piergiovanni,
71,72
G. Pillant,
28
L. Pinard,
22
M. Pirello,
44
M. Pitkin,
43
R. Poggiani,
18,19
D. Y. T. Pong,
90
S. Ponrathnam,
3
P. Popolizio,
28
E. K. Porter,
27
J. Powell,
152
A. K. Prajapati,
106
J. Prasad,
3
K. Prasai,
48
R. Prasanna,
129
G. Pratten,
98
T. Prestegard,
23
S. Privitera,
35
G. A. Prodi,
111, 95
L. G. Prokhorov,
61
O. Puncken,
8, 9
M. Punturo,
40
P. Puppo,
31
M. P ̈urrer,
35
H. Qi,
23
V. Quetschke,
103
P. J. Quinonez,
33
E. A. Quintero,
1
R. Quitzow-James,
69
F. J. Raab,
44
H. Radkins,
44
N. Radulescu,
64
P. Raffai,
105
S. Raja,
60
C. Rajan,
60
B. Rajbhandari,
83
M. Rakhmanov,
103
K. E. Ramirez,
103
A. Ramos-Buades,
98
Javed Rana,
3
K. Rao,
58
P. Rapagnani,
112, 31
V. Raymond,
67
M. Razzano,
18, 19
J. Read,
26
T. Regimbau,
32
L. Rei,
59
S. Reid,
24
D. H. Reitze,
1, 47
W. Ren,
17
F. Ricci,
112, 31
C. J. Richardson,
33
J. W. Richardson,
1
P. M. Ricker,
17
K. Riles,
125
M. Rizzo,
58
N. A. Robertson,
1, 43
R. Robie,
43
F. Robinet,
25
A. Rocchi,
30
L. Rolland,
32
J. G. Rollins,
1
V. J. Roma,
69
M. Romanelli,
66
R. Romano,
4, 5
C. L. Romel,
44
J. H. Romie,
7
K. Rose,
114
D. Rosi ́nska,
164, 53
S. G. Rosofsky,
17
M. P. Ross,
165
S. Rowan,
43
A. R ̈udiger,
8, 9,
‡
P. Ruggi,
28
G. Rutins,
166
K. Ryan,
44
S. Sachdev,
1
T. Sadecki,
44
M. Sakellariadou,
131
L. Salconi,
28
M. Saleem,
141
A. Samajdar,
36
L. Sammut,
6
E. J. Sanchez,
1
L. E. Sanchez,
1
N. Sanchis-Gual,
20
V. Sandberg,
44
J. R. Sanders,
41
K. A. Santiago,
34
N. Sarin,
6
B. Sassolas,
22,67
P. R. Saulson,
41
O. Sauter,
125
R. L. Savage,
44
P. Schale,
69
M. Scheel,
45
J. Scheuer,
58
P. Schmidt,
63
R. Schnabel,
139
R. M. S. Schofield,
69
A. Sch ̈onbeck,
139
E. Schreiber,
8, 9
B. W. Schulte,
8, 9
B. F. Schutz,
67
S. G. Schwalbe,
33
J. Scott,
43
S. M. Scott,
21
E. Seidel,
17
D. Sellers,
7
A. S. Sengupta,
167
N. Sennett,
35
D. Sentenac,
28
V. Sequino,
29, 30, 14
A. Sergeev,
134
Y. Setyawati,
8, 9
D. A. Shaddock,
21
T. Shaffer,
44
M. S. Shahriar,
58
M. B. Shaner,
110
L. Shao,
35
P. Sharma,
60
P. Shawhan,
75
H. Shen,
17
R. Shink,
168
D. H. Shoemaker,
12
D. M. Shoemaker,
76
S. ShyamSundar,
60
K. Siellez,
76
M. Sieniawska,
53
D. Sigg,
44
A. D. Silva,
13
L. P. Singer,
79
N. Singh,
73
A. Singhal,
14, 31
A. M. Sintes,
98
S. Sitmukhambetov,
103
V. Skliris,
67
B. J. J. Slagmolen,
21
T. J. Slaven-Blair,
62
J. R. Smith,
26
R. J. E. Smith,
6
S. Somala,
169
E. J. Son,
137
B. Sorazu,
43
F. Sorrentino,
59
T. Souradeep,
3
E. Sowell,
83
A. P. Spencer,
43
A. K. Srivastava,
106
V. Srivastava,
41
K. Staats,
58
C. Stachie,
64
M. Standke,
8, 9
D. A. Steer,
27
M. Steinke,
8, 9
J. Steinlechner,
139, 43
S. Steinlechner,
139
D. Steinmeyer,
8, 9
S. P. Stevenson,
152
D. Stocks,
48
R. Stone,
103
D. J. Stops,
11
K. A. Strain,
43
G. Stratta,
71, 72
S. E. Strigin,
61
A. Strunk,
44
R. Sturani,
170
A. L. Stuver,
171
V. Sudhir,
12
T. Z. Summerscales,
172
L. Sun,
1
S. Sunil,
106
J. Suresh,
3
P. J. Sutton,
67
B. L. Swinkels,
36
M. J. Szczepa ́nczyk,
33
M. Tacca,
36
S. C. Tait,
43
C. Talbot,
6
D. Talukder,
69
D. B. Tanner,
47
M. T ́apai,
122
A. Taracchini,
35
J. D. Tasson,
93
R. Taylor,
1
F. Thies,
8, 9
M. Thomas,
7
P. Thomas,
44
S. R. Thondapu,
60
K. A. Thorne,
7
E. Thrane,
6
Shubhanshu Tiwari,
111, 95
Srishti Tiwari,
123
V. Tiwari,
67
K. Toland,
43
M. Tonelli,
18, 19
Z. Tornasi,
43
A. Torres-Forn ́e,
173
C. I. Torrie,
1
D. T ̈oyr ̈a,
11
F. Travasso,
28,40
G. Traylor,
7
M. C. Tringali,
73
A. Trovato,
27
L. Trozzo,
174,19
R. Trudeau,
1
K. W. Tsang,
36
M. Tse,
12
R. Tso,
45
L. Tsukada,
81
D. Tsuna,
81
D. Tuyenbayev,
103
K. Ueno,
81
D. Ugolini,
175
C. S. Unnikrishnan,
123
A. L. Urban,
2
S. A. Usman,
67
H. Vahlbruch,
9
G. Vajente,
1
G. Valdes,
2
N. van Bakel,
36
M. van Beuzekom,
36
J. F. J. van den Brand,
74, 36
C. Van Den Broeck,
36, 176
D. C. Vander-Hyde,
41
J. V. van Heijningen,
62
L. van der Schaaf,
36
A. A. van Veggel,
43
M. Vardaro,
50,51
V. Varma,
45
S. Vass,
1
M. Vas ́uth,
46
A. Vecchio,
11
G. Vedovato,
51
J. Veitch,
43
P. J. Veitch,
54
K. Venkateswara,
165
G. Venugopalan,
1
D. Verkindt,
32
F. Vetrano,
71, 72
A. Vicer ́e,
71,72
A. D. Viets,
23
D. J. Vine,
166
J.-Y. Vinet,
64
S. Vitale,
12
T. Vo,
41
H. Vocca,
39, 40
C. Vorvick,
44
S. P. Vyatchanin,
61
A. R. Wade,
1
L. E. Wade,
114
M. Wade,
114
R. Walet,
36
M. Walker,
26
L. Wallace,
1
S. Walsh,
23
G. Wang,
14, 19
H. Wang,
11
J. Z. Wang,
125
W. H. Wang,
103
Y. F. Wang,
90
R. L. Ward,
21
Z. A. Warden,
33
J. Warner,
44
M. Was,
32
J. Watchi,
99
B. Weaver,
44
L.-W. Wei,
8, 9
M. Weinert,
8, 9
A. J. Weinstein,
1
R. Weiss,
12
F. Wellmann,
8, 9
L. Wen,
62
E. K. Wessel,
17
P. Weßels,
8, 9
J. W. Westhouse,
33
K. Wette,
21
J. T. Whelan,
57
B. F. Whiting,
47
C. Whittle,
12
D. M. Wilken,
8, 9
D. Williams,
43
A. R. Williamson,
127, 36
J. L. Willis,
1
B. Willke,
8, 9
M. H. Wimmer,
8, 9
W. Winkler,
8, 9
C. C. Wipf,
1
H. Wittel,
8, 9
G. Woan,
43
J. Woehler,
8, 9
J. K. Wofford,
57
J. Worden,
44
J. L. Wright,
43
D. S. Wu,
8, 9
D. M. Wysocki,
57
L. Xiao,
1
H. Yamamoto,
1
C. C. Yancey,
75
L. Yang,
113
M. J. Yap,
21
M. Yazback,
47
D. W. Yeeles,
67
Hang Yu,
12
Haocun Yu,
12
S. H. R. Yuen,
90
M. Yvert,
32
A. K. Zadro ̇zny,
103,142
M. Zanolin,
33
T. Zelenova,
28
J.-P. Zendri,
51
M. Zevin,
58
4
J. Zhang,
62
L. Zhang,
1
T. Zhang,
43
C. Zhao,
62
M. Zhou,
58
Z. Zhou,
58
X. J. Zhu,
6
M. E. Zucker,
1,12
and J. Zweizig
1
(The LIGO Scientific Collaboration and the Virgo Collaboration)
M. Keith,
177
A. Lyne,
177
B. Stappers,
177
and P. Weltervrede
177
1
LIGO, California Institute of Technology, Pasadena, CA 911
25, USA
2
Louisiana State University, Baton Rouge, LA 70803, USA
3
Inter-University Centre for Astronomy and Astrophysics, P
une 411007, India
4
Universit`a di Salerno, Fisciano, I-84084 Salerno, Italy
5
INFN, Sezione di Napoli, Complesso Universitario di Monte S
.Angelo, I-80126 Napoli, Italy
6
OzGrav, School of Physics & Astronomy, Monash University, C
layton 3800, Victoria, Australia
7
LIGO Livingston Observatory, Livingston, LA 70754, USA
8
Max Planck Institute for Gravitational Physics (Albert Ein
stein Institute), D-30167 Hannover, Germany
9
Leibniz Universit ̈at Hannover, D-30167 Hannover, Germany
10
University of Cambridge, Cambridge CB2 1TN, United Kingdom
11
University of Birmingham, Birmingham B15 2TT, United Kingd
om
12
LIGO, Massachusetts Institute of Technology, Cambridge, M
A 02139, USA
13
Instituto Nacional de Pesquisas Espaciais, 12227-010 S ̃ao
Jos ́e dos Campos, S ̃ao Paulo, Brazil
14
Gran Sasso Science Institute (GSSI), I-67100 L’Aquila, Ita
ly
15
INFN, Laboratori Nazionali del Gran Sasso, I-67100 Assergi
, Italy
16
International Centre for Theoretical Sciences, Tata Insti
tute of Fundamental Research, Bengaluru 560089, India
17
NCSA, University of Illinois at Urbana-Champaign, Urbana,
IL 61801, USA
18
Universit`a di Pisa, I-56127 Pisa, Italy
19
INFN, Sezione di Pisa, I-56127 Pisa, Italy
20
Departamento de Astronom ́ıa y Astrof ́ısica, Universitat d
e Val`encia, E-46100 Burjassot, Val`encia, Spain
21
OzGrav, Australian National University, Canberra, Austra
lian Capital Territory 0200, Australia
22
Laboratoire des Mat ́eriaux Avanc ́es (LMA), CNRS/IN2P3, F-
69622 Villeurbanne, France
23
University of Wisconsin-Milwaukee, Milwaukee, WI 53201, U
SA
24
SUPA, University of Strathclyde, Glasgow G1 1XQ, United Kin
gdom
25
LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit ́e Paris-Sacl
ay, F-91898 Orsay, France
26
California State University Fullerton, Fullerton, CA 9283
1, USA
27
APC, AstroParticule et Cosmologie, Universit ́e Paris Dide
rot,
CNRS/IN2P3, CEA/Irfu, Observatoire de Paris,
Sorbonne Paris Cit ́e, F-75205 Paris Cedex 13, France
28
European Gravitational Observatory (EGO), I-56021 Cascin
a, Pisa, Italy
29
Universit`a di Roma Tor Vergata, I-00133 Roma, Italy
30
INFN, Sezione di Roma Tor Vergata, I-00133 Roma, Italy
31
INFN, Sezione di Roma, I-00185 Roma, Italy
32
Laboratoire d’Annecy de Physique des Particules (LAPP), Un
iv. Grenoble Alpes,
Universit ́e Savoie Mont Blanc, CNRS/IN2P3, F-74941 Annecy
, France
33
Embry-Riddle Aeronautical University, Prescott, AZ 86301
, USA
34
Montclair State University, Montclair, NJ 07043, USA
35
Max Planck Institute for Gravitational Physics (Albert Ein
stein Institute), D-14476 Potsdam-Golm, Germany
36
Nikhef, Science Park 105, 1098 XG Amsterdam, The Netherland
s
37
Korea Institute of Science and Technology Information, Dae
jeon 34141, South Korea
38
West Virginia University, Morgantown, WV 26506, USA
39
Universit`a di Perugia, I-06123 Perugia, Italy
40
INFN, Sezione di Perugia, I-06123 Perugia, Italy
41
Syracuse University, Syracuse, NY 13244, USA
42
University of Minnesota, Minneapolis, MN 55455, USA
43
SUPA, University of Glasgow, Glasgow G12 8QQ, United Kingdo
m
44
LIGO Hanford Observatory, Richland, WA 99352, USA
45
Caltech CaRT, Pasadena, CA 91125, USA
46
Wigner RCP, RMKI, H-1121 Budapest, Konkoly Thege Mikl ́os ́u
t 29-33, Hungary
47
University of Florida, Gainesville, FL 32611, USA
48
Stanford University, Stanford, CA 94305, USA
49
Universit`a di Camerino, Dipartimento di Fisica, I-62032 C
amerino, Italy
50
Universit`a di Padova, Dipartimento di Fisica e Astronomia
, I-35131 Padova, Italy
51
INFN, Sezione di Padova, I-35131 Padova, Italy
52
Montana State University, Bozeman, MT 59717, USA
53
Nicolaus Copernicus Astronomical Center, Polish Academy o
f Sciences, 00-716, Warsaw, Poland
54
OzGrav, University of Adelaide, Adelaide, South Australia
5005, Australia
55
Theoretisch-Physikalisches Institut, Friedrich-Schill
er-Universit ̈at Jena, D-07743 Jena, Germany
56
INFN, Sezione di Milano Bicocca, Gruppo Collegato di Parma,
I-43124 Parma, Italy
5
57
Rochester Institute of Technology, Rochester, NY 14623, US
A
58
Center for Interdisciplinary Exploration & Research in Ast
rophysics (CIERA),
Northwestern University, Evanston, IL 60208, USA
59
INFN, Sezione di Genova, I-16146 Genova, Italy
60
RRCAT, Indore, Madhya Pradesh 452013, India
61
Faculty of Physics, Lomonosov Moscow State University, Mos
cow 119991, Russia
62
OzGrav, University of Western Australia, Crawley, Western
Australia 6009, Australia
63
Department of Astrophysics/IMAPP, Radboud University Nij
megen,
P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
64
Artemis, Universit ́e Cˆote d’Azur, Observatoire Cˆote d’A
zur,
CNRS, CS 34229, F-06304 Nice Cedex 4, France
65
Physik-Institut, University of Zurich, Winterthurerstras
se 190, 8057 Zurich, Switzerland
66
Univ Rennes, CNRS, Institut FOTON - UMR6082, F-3500 Rennes,
France
67
Cardiff University, Cardiff CF24 3AA, United Kingdom
68
Washington State University, Pullman, WA 99164, USA
69
University of Oregon, Eugene, OR 97403, USA
70
Laboratoire Kastler Brossel, Sorbonne Universit ́e, CNRS,
ENS-Universit ́e PSL, Coll`ege de France, F-75005 Paris, Fr
ance
71
Universit`a degli Studi di Urbino ’Carlo Bo,’ I-61029 Urbin
o, Italy
72
INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Firenz
e, Italy
73
Astronomical Observatory Warsaw University, 00-478 Warsa
w, Poland
74
VU University Amsterdam, 1081 HV Amsterdam, The Netherland
s
75
University of Maryland, College Park, MD 20742, USA
76
School of Physics, Georgia Institute of Technology, Atlant
a, GA 30332, USA
77
Universit ́e Claude Bernard Lyon 1, F-69622 Villeurbanne, F
rance
78
Universit`a di Napoli ’Federico II,’ Complesso Universita
rio di Monte S.Angelo, I-80126 Napoli, Italy
79
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
80
Dipartimento di Fisica, Universit`a degli Studi di Genova,
I-16146 Genova, Italy
81
RESCEU, University of Tokyo, Tokyo, 113-0033, Japan.
82
Tsinghua University, Beijing 100084, China
83
Texas Tech University, Lubbock, TX 79409, USA
84
The University of Mississippi, University, MS 38677, USA
85
Museo Storico della Fisica e Centro Studi e Ricerche “Enrico
Fermi”,
I-00184 Roma, Italyrico Fermi, I-00184 Roma, Italy
86
The Pennsylvania State University, University Park, PA 168
02, USA
87
National Tsing Hua University, Hsinchu City, 30013 Taiwan,
Republic of China
88
Charles Sturt University, Wagga Wagga, New South Wales 2678
, Australia
89
University of Chicago, Chicago, IL 60637, USA
90
The Chinese University of Hong Kong, Shatin, NT, Hong Kong
91
Seoul National University, Seoul 08826, South Korea
92
Pusan National University, Busan 46241, South Korea
93
Carleton College, Northfield, MN 55057, USA
94
INAF, Osservatorio Astronomico di Padova, I-35122 Padova,
Italy
95
INFN, Trento Institute for Fundamental Physics and Applica
tions, I-38123 Povo, Trento, Italy
96
OzGrav, University of Melbourne, Parkville, Victoria 3010
, Australia
97
Columbia University, New York, NY 10027, USA
98
Universitat de les Illes Balears, IAC3—IEEC, E-07122 Palma
de Mallorca, Spain
99
Universit ́e Libre de Bruxelles, Brussels 1050, Belgium
100
Sonoma State University, Rohnert Park, CA 94928, USA
101
Departamento de Matem ́aticas, Universitat de Val`encia, E
-46100 Burjassot, Val`encia, Spain
102
University of Rhode Island, Kingston, RI 02881, USA
103
The University of Texas Rio Grande Valley, Brownsville, TX 7
8520, USA
104
Bellevue College, Bellevue, WA 98007, USA
105
MTA-ELTE Astrophysics Research Group, Institute of Physic
s, E ̈otv ̈os University, Budapest 1117, Hungary
106
Institute for Plasma Research, Bhat, Gandhinagar 382428, I
ndia
107
The University of Sheffield, Sheffield S10 2TN, United Kingdom
108
IGFAE, Campus Sur, Universidade de Santiago de Compostela,
15782 Spain
109
Dipartimento di Scienze Matematiche, Fisiche e Informatic
he, Universit`a di Parma, I-43124 Parma, Italy
110
California State University, Los Angeles, 5151 State Unive
rsity Dr, Los Angeles, CA 90032, USA
111
Universit`a di Trento, Dipartimento di Fisica, I-38123 Pov
o, Trento, Italy
112
Universit`a di Roma ’La Sapienza,’ I-00185 Roma, Italy
113
Colorado State University, Fort Collins, CO 80523, USA
114
Kenyon College, Gambier, OH 43022, USA
115
Christopher Newport University, Newport News, VA 23606, US
A
6
116
National Astronomical Observatory of Japan, 2-21-1 Osawa,
Mitaka, Tokyo 181-8588, Japan
117
Canadian Institute for Theoretical Astrophysics,
University of Toronto, Toronto, Ontario M5S 3H8, Canada
118
Observatori Astron`omic, Universitat de Val`encia, E-469
80 Paterna, Val`encia, Spain
119
School of Mathematics, University of Edinburgh, Edinburgh
EH9 3FD, United Kingdom
120
Institute Of Advanced Research, Gandhinagar 382426, India
121
Indian Institute of Technology Bombay, Powai, Mumbai 400 07
6, India
122
University of Szeged, D ́om t ́er 9, Szeged 6720, Hungary
123
Tata Institute of Fundamental Research, Mumbai 400005, Ind
ia
124
INAF, Osservatorio Astronomico di Capodimonte, I-80131, N
apoli, Italy
125
University of Michigan, Ann Arbor, MI 48109, USA
126
American University, Washington, D.C. 20016, USA
127
GRAPPA, Anton Pannekoek Institute for Astronomy and Instit
ute of High-Energy Physics,
University of Amsterdam, Science Park 904, 1098 XH Amsterda
m, The Netherlands
128
Delta Institute for Theoretical Physics, Science Park 904,
1090 GL Amsterdam, The Netherlands
129
Directorate of Construction, Services & Estate Management
, Mumbai 400094 India
130
University of Bia lystok, 15-424 Bia lystok, Poland
131
King’s College London, University of London, London WC2R 2L
S, United Kingdom
132
University of Southampton, Southampton SO17 1BJ, United Ki
ngdom
133
University of Washington Bothell, Bothell, WA 98011, USA
134
Institute of Applied Physics, Nizhny Novgorod, 603950, Rus
sia
135
Ewha Womans University, Seoul 03760, South Korea
136
Inje University Gimhae, South Gyeongsang 50834, South Kore
a
137
National Institute for Mathematical Sciences, Daejeon 340
47, South Korea
138
Ulsan National Institute of Science and Technology, Ulsan 4
4919, South Korea
139
Universit ̈at Hamburg, D-22761 Hamburg, Germany
140
Maastricht University, P.O. Box 616, 6200 MD Maastricht, Th
e Netherlands
141
Chennai Mathematical Institute, Chennai 603103, India
142
NCBJ, 05-400
́
Swierk-Otwock, Poland
143
Institute of Mathematics, Polish Academy of Sciences, 0065
6 Warsaw, Poland
144
Cornell University, Ithaca, NY 14850, USA
145
Hillsdale College, Hillsdale, MI 49242, USA
146
Hanyang University, Seoul 04763, South Korea
147
Korea Astronomy and Space Science Institute, Daejeon 34055
, South Korea
148
NASA Marshall Space Flight Center, Huntsville, AL 35811, US
A
149
Dipartimento di Matematica e Fisica, Universit`a degli Stu
di Roma Tre, I-00146 Roma, Italy
150
INFN, Sezione di Roma Tre, I-00146 Roma, Italy
151
ESPCI, CNRS, F-75005 Paris, France
152
OzGrav, Swinburne University of Technology, Hawthorn VIC 3
122, Australia
153
University of Portsmouth, Portsmouth, PO1 3FX, United King
dom
154
Southern University and A&M College, Baton Rouge, LA 70813,
USA
155
College of William and Mary, Williamsburg, VA 23187, USA
156
Centre Scientifique de Monaco, 8 quai Antoine Ier, MC-98000,
Monaco
157
Indian Institute of Technology Madras, Chennai 600036, Ind
ia
158
INFN Sezione di Torino, Via P. Giuria 1, I-10125 Torino, Ital
y
159
Institut des Hautes Etudes Scientifiques, F-91440 Bures-su
r-Yvette, France
160
IISER-Kolkata, Mohanpur, West Bengal 741252, India
161
Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362 USA
162
Universit ́e de Lyon, F-69361 Lyon, France
163
Hobart and William Smith Colleges, Geneva, NY 14456, USA
164
Janusz Gil Institute of Astronomy, University of Zielona G ́o
ra, 65-265 Zielona G ́ora, Poland
165
University of Washington, Seattle, WA 98195, USA
166
SUPA, University of the West of Scotland, Paisley PA1 2BE, Un
ited Kingdom
167
Indian Institute of Technology, Gandhinagar Ahmedabad Guj
arat 382424, India
168
Universit ́e de Montr ́eal/Polytechnique, Montreal, Quebe
c H3T 1J4, Canada
169
Indian Institute of Technology Hyderabad, Sangareddy, Kha
ndi, Telangana 502285, India
170
International Institute of Physics, Universidade Federal
do Rio Grande do Norte, Natal RN 59078-970, Brazil
171
Villanova University, 800 Lancaster Ave, Villanova, PA 190
85, USA
172
Andrews University, Berrien Springs, MI 49104, USA
173
Max Planck Institute for Gravitationalphysik (Albert Eins
tein Institute), D-14476 Potsdam-Golm, Germany
174
Universit`a di Siena, I-53100 Siena, Italy
175
Trinity University, San Antonio, TX 78212, USA
176
Van Swinderen Institute for Particle Physics and Gravity,
University of Groningen, Nijenborgh 4, 9747 AG Groningen, T
he Netherlands
7
177
School of Physics and Astronomy, University of Manchester,
Manchester, M13 9PL, UK
(Dated: February 26, 2019)
Isolated spinning neutron stars, asymmetric with respect t
o their rotation axis, are expected to be
sources of continuous gravitational waves. The most sensit
ive searches for these sources are based
on accurate matched filtering techniques, that assume the co
ntinuous wave to be phase-locked with
the pulsar beamed emission. While matched filtering maximiz
es the search sensitivity, a significant
signal-to-noise ratio loss will happen in case of a mismatch
between the assumed and the true signal
phase evolution. Narrow-band algorithms allow for a small m
ismatch in the frequency and spin-down
values of the pulsar while integrating coherently the entir
e data set. In this paper we describe a
narrow-band search using LIGO O2 data for the continuous wav
e emission of 33 pulsars. No evidence
for a continuous wave signal has been found and upper-limits
on the gravitational wave amplitude,
over the analyzed frequency and spin-down volume, have been
computed for each of the targets.
In this search we have surpassed the spin-down limit for some
of the pulsars already present in the
O1 LIGO narrow-band search, such as J1400
−
6325 J1813
−
1246, J1833
−
1034, J1952+3252, and for
new targets such as J0940
−
5428 and J1747
−
2809. For J1400
−
6325, J1833
−
1034 and J1747
−
2809
this is the first time the spin-down limit is surpassed.
I. INTRODUCTION
Eleven gravitational wave (GW) signals have so far
been detected by the LIGO [
1
,
2
] and Virgo GW inter-
ferometers [
3
] in their first and second observing runs (O1
and O2, respectively) [
4
]. All the signals detected so far
come from the coalescence of two compact objects. These
signals belong to the class of
transient signals
, since they
are observed only within a short time window during the
observing run. In particular ten detection from binary
black holes merger [
4
–
9
] (with signals lasting a fraction
of a second) and a detection from a binary neutron star
(NS) merger [
10
] (observed for tens of seconds) have been
made.
Another class of GW signals potentially observable by
the LIGO and Virgo detectors are the so-called
continu-
ous wave
(CW). CWs could be potentially present during
the entire data taking period of the GW detectors. Po-
tential sources of CWs are isolated spinning NSs asym-
metric with respect to their rotation axis. If the star has
an equatorial ellipticity, CWs are emitted at a frequency
of two times its rotational frequency.
Different types of CW searches can be performed ac-
cording to the astrophysical scenario in which the NS is
observed. If the NS is a pulsar, an accurate ephemeris
may be available and matched filtering techniques can
be employed to reach, ideally, the best possible sensi-
tivity by using waveform templates that cover the en-
tire observing run. These type of searches are referred
as
targeted searches
. The LIGO and Virgo Collabora-
tions have already searched for this type of emission from
known pulsars (both isolated and some in binaries) [
11
–
19
], for which accurate ephemerides were available. An-
other scenario is when the NS is observed as a central
compact object of a supernova remnant or in a binary
system but no evaluation of its rotational frequency is
∗
Deceased, February 2018.
†
Deceased, November 2017.
‡
Deceased, July 2018.
available. In this case we can pinpoint the source and
look for the CW signal over a wide frequency range using
semi-coherent analysis, e.g. dividing the observing run in
several data chunks and looking for a waveform template
in each of them. Such searches are called
‘directed”
and
offer the possibility to explore a large number of tem-
plates at the price of a lower sensitivity with respect to
targeted searches. This is the case of CW searches from
central compact object in supernova remnants [
20
,
21
]
or NSs in binary systems [
22
–
24
]. Recently, there has
been also a study for a possible deviation of CW sig-
nals from the General Relativity model[
25
], by including
non-tensorial modes.
Between targeted and directed searches we find the
narrow-band
searches. Such pipelines are based on algo-
rithms which allow to make a full coherent search and,
at the same time, are able to deal with a frequency mis-
match between the CW signal and the electromagnetic
inferred value of the order of 500 mHz [
14
,
26
,
27
]. Usu-
ally, this will correspond to the evaluation of millions of
waveform templates for each pulsar considered into the
analysis.
Hence, narrow-band searches offers a sensitivity com-
parable to the one of targeted searches while relaxing
the phase-lock assumption of the CW signal with the NS
rotation. The CW phase-locking is indeed a strong as-
sumption that may prevent the detection of a CW signal.
In fact, a coherent (or targeted) CW search that uses 1
year of data has a frequency resolution of about 3
×
10
−
8
Hz. A mismatch between the rotational frequency in-
ferred from the ephemeris and the CW signal frequency,
of this size or larger, is enough to drastically reduce the
chance of detection.
A small frequency mismatch may arise for several phys-
ical reasons, that usually are parametrized in a frequency
mismatch of the form ∆
f
gw
∼
f
gw
(1+
δ
) [
14
]. In the case
of a differential rotation between the GW engine and the
electromagnetic pulse engine, the factor
δ
will be pro-
portional to the timescale of some torque which enforce
correlation between the two engines. Another possibility
is that the NS is freely-precessing. In this scenario the
δ
8
factor will be proportional to the angle between the star
symmetry axis and the star rotation axis [
28
]. In some
of the previous narrow-band searches [
14
,
26
] we used a
value of
δ
∼
10
−
4
, which can accommodate the previ-
ous theoretical models. However starting from the first
narrow-band search with advanced detector data [
27
], we
explore a frequency/spin-down range corresponding to
δ
∼
10
−
3
.
Another possibility is that the pulsar ephemeris pro-
vided are not accurate enough to carry on targeted
searches with the needed resolution, or they are not avail-
able during the observing time of our detectors. That
is the case of many low frequency and energetic pul-
sars observed in the X and
γ
-ray bands, such as J1833-
1034 and J1813-1749. For these reasons, along with tar-
geted searches, we search for CWs also with narrow-band
searches.
In this paper we present the narrow-band search for
CWs from 33 known pulsars using LIGO O2 data. In
Sec.
II
we provide a brief background on the CW signal
model and the algorithm used. In Sec.
III
we summarize
the main features of the O2 narrow-band analysis, while
in Sec.
IV
we introduce the pulsars that we have selected
for this search. The results of the search, followed by the
upper-limits on the signal strain amplitude, are discussed
in Sec.
V
. Finally in Sec.
VI
we draw the conclusion of
this work.
II. BACKGROUND
A. The signal
The GW signal emitted by an asymmetric spinning NS
can be written, using the formalism introduced in [
29
],
as the real part of
h
(
t
) =
H
0
(
H
+
(
η,ψ
)
A
+
(
t
)+
H
×
(
η,ψ
)
A
×
(
t
))
e
2
πif
gw
(
t
)
t
+
iφ
0
(1)
where
f
gw
(
t
) is the GW frequency (which incorporates
all the modulation of the signal at the detector frame)
and
φ
0
an initial phase. The polarization amplitudes
H
+
(
η,ψ
)
,H
×
(
η,ψ
) are function of the ratio of the po-
larization ellipse semi-minor to semi-major axis
η
and the
polarization angle
ψ
, see [
29
] for more details. The func-
tions
A
+
(
t
)
,A
×
(
t
) are the detector responses to the two
wave polarizations. In Eq. (
1
), the amplitude of the GW
H
0
is related to the canonical strain amplitude
h
0
given
the angle between the line of sight and the star rotation
axis
ι
:
H
0
=
h
0
√
1 + 6 cos
2
ι
+ cos
4
ι
4
(2)
and
h
0
=
1
d
4
π
2
G
c
4
I
zz
f
2
gw
ǫ.
(3)
Being
d, I
zz
and
ǫ
the star distance, moment of inertia
with respect to the rotation axis and
ellipticity
. The el-
lipticity measures the degree of asymmetry of the star
with respect to its rotation axis. In the detector refer-
ence frame the signal is modulated by several effects, the
most important being the
R ̈omer delay
due to the detec-
tor motion (also called barycentric modulation) and the
source’s intrinsic spin-down, due to the rotational energy
loss from the source. Given a measure of the pulsar ro-
tational frequency
f
rot
, its derivative
̇
f
rot
and distance
d
,
the GW signal amplitude can be constrained, assuming
that all the star’s rotational energy is lost via gravita-
tional radiation. This theoretical value, called
spin-down
limit
, is given by [
30
]:
h
sd
= 8
.
06
×
10
−
19
I
1
/
2
38
[
1kpc
d
][
̇
f
rot
Hz
/
s
]
1
/
2
[
Hz
f
rot
]
1
/
2
(4)
where
I
38
is the star’s moment of inertia in units of
10
38
kg m
2
. Different values of the moment of inertia are
possible according to the NS equation of state, mass and
spin[
31
], however in this work we will assume its canon-
ical value to be
I
≈
10
38
kg m
2
. The corresponding spin-
down limit on the star’s equatorial fiducial ellipticity can
be obtained from Eq. (
3
):
ǫ
sd
= 0
.
237
I
−
1
38
[
h
sd
10
−
24
][
Hz
f
rot
]
2
[
d
1kpc
]
.
(5)
which does not depend on the star’s distance.
B. The 5-vector narrowband pipeline
The narrow-band pipeline uses the 5-vector method
[
32
] and, in particular, its latest implementation for
narrow-band searches described in [
33
]. The pipeline ex-
plores a volume of frequency and spin-down values by ap-
plying barycentric and spin-down corrections to the data,
and then identifies the GW signal using its characteristic
frequency components.
Once we have properly demodulated the data, the
GW signal power is spread among five frequencies, given
by the detector sidereal responses
A
+
(
t
)
,A
×
(
t
):
f
gw
−
2
F
sid
,f
gw
−
F
sid
,f
gw
,f
gw
+
F
sid
and
f
gw
+ 2
F
sid
, where
F
sid
is the sidereal frequency of the Earth.
The barycentric corrections are applied using a
frequency-independent non-uniform resampling. The
spin-down is removed by applying a phase correction on
the data time series. Also the Einstein delay is prop-
erly corrected in the time domain. Once all the modula-
tions have been taken into account, a pair of matched fil-
ters, one for each sidereal response function, is computed
for each point of the explored parameter space. This is
done using a frequency grid which allows to compute the
matched filters simultaneously over the whole analyzed
frequency band. These steps are done separately for each
detector. Then, the output of the matched filters, at each
9
point of the parameter space, are combined, taking into
account the phase shift
1
between the two data sets, in
order to build a detection statistic.
The next step consists in selecting the maximum of the
detection statistic for every 10
−
4
Hz interval and over the
whole spin-down range. Within this set, points in the pa-
rameter space with a p-value below a given threshold are
considered potentially interesting outliers and are subject
to further analysis steps.
III. THE ANALYSIS
The LIGO second observing run O2 started on Novem-
ber 30th 2016 16:00:00 UTC and ended on August 25th
2017 22:00:00 UTC, while Virgo joined the run later, on
August 1st 2017 12:00:00 UTC, and ended on August
25th 2017 22:00:00 UTC. The narrow-band search can
be performed jointly between different detectors if the
data sets cover the same observing time. Since Virgo
O2 data covered just
∼
1 month at the end of O2, and
was characterized by a lower sensitivity with respect to
LIGO data, we have decided to exclude it from the anal-
ysis. For this analysis we have used the second version
of calibratated LIGO data (C02) [
34
?
]. We jointly ana-
lyzed LIGO Hanford (LHO) and LIGO Livingston (LLO)
data over the period between January 4th 2017 00:00:00
UTC and August 25th 2017 22:00:00 UTC. LLO data be-
tween the beginning of the run and December 22th 2016
have been excluded due to bad spectral contamination,
while both detectors underwent a commissioning break
between December 22th 2016 and January 4th 2017. The
observing time
T
obs
was
∼
232 days, implying frequency
and spin-down bins of, respectively,
δf
= 5
×
10
−
8
Hz
and
δ
̇
f
= 2
.
5
×
10
−
15
Hz/s. LHO and LLO duty cy-
cles were about 45% and the 56% and corresponded to
an effective observing time of 104 days and 129 days re-
spectively.
2
The sensitivity of the O2 search is reported
in Fig.
1
, where we show also O1 sensitivity. While at
lower frequency only O2 LLO seems to be much better
than O1, at higher frequencies the sensitivity is signifi-
cantly better for both the detectors. In order to validate
the analysis, we have looked for 4 hardware injections
in the data checking if their parameters were recovered
correctly, see Appendix A.
The explored frequency and spindown volumes were set
to 0.4% of the pulsar rotational frequency and spindown
reported in the ephemeris. Since in this analysis we sub-
sampled data at 1 Hz, the explored frequency region of
some pulsars has been chosen manually in order to avoid
a possible signal aliasing.
1
This is given by the fact that the data sampling usually does n
ot
begin at the exact same time for different detectors.
2
With the exception of pulsars that have glitched during the a
nal-
ysis. For those we have performed two independent analysis b
e-
fore and after the glitch.
We have decided to select as
outliers
for the follow-
up the points in the parameter space with a value of
the detection statistic corresponding to a p-value of 0
.
1%
(taking into account the number of trials) or smaller.
In the previous O1 search we used a threshold of 1%,
due to the fact that data quality of LHO and LLO was
significantly different at lower frequencies, see Appendix
B for more details.
IV. SELECTED TARGETS
In our O2 analysis we have selected as an initial set
of targets all the pulsars present in the O1 narrow-band
search[
27
]. Then we have enlarged it, deciding to an-
alyze all the pulsars with rotation frequency above 10
Hz and with spin-down limit, given in Eq. (
4
), within
a factor 10 from the optimal sensitivity of the search of
O2 LLO (in most cases). This choice has been driven
by the fact that available pulsar distances can be af-
fected by a large error. Among these, we have considered
pulsars with rotational frequencies between 10 Hz and
350 Hz and computed their spindown limit according to
the most recent estimation of the distance given in the
ATNF catalog[
35
] (
v1.58
). For the pulsars J0205+6449,
J0534+2200, J1913+1011, J1952+3252, J2229+6114 we
have used updated ephemerides provided by the tele-
scopes at Jodrell Bank (UK). Tab.
III
reports the spin-
down limit on amplitude
h
0
and ellipticity
ǫ
for each
target, given their distance estimation and uncertainty.
Hereafter, the distance uncertainties are propagated to
the derived quantities (such as the spin-down limit) as-
suming normal distributions, namely:
σ
2
Y
=
(
∂Y
∂d
)
2
σ
2
d
,
with
Y
being a function of the distance and
σ
2
the dis-
tribution variance.
The spindown limits are compared to the estimated
narrow-band search sensitivity in Fig
1
. The analysis
covers the 11 targets that we have already analyzed for
O1 plus 22 new targets. Based on the estimated sensi-
tivity we expected to surpass the spin-down limit, in the
O2 analysis, for 9 of the 11 O1 targets. The exceptions
are J2043+2740 and J2229+6114, for which the current
distance estimation has been increased with respect to
the ATNF catalog
v1.54
(the catalog used for O1 [
27
]).
The new O2 targets mainly consist of low-frequency
pulsars, but there are also a few millisecond pulsars, for
which we can approach the spin-down limit. Among
these there is the millisecond pulsar J2124+3358, for
which we expect to barely approach the spin-down limit
with targeted searches. One of these millisecond pulsars,
J1300+1240, is located in a binary system. However, ac-
cording to the orbital parameters in the ephemeris, the
intrinsic binary orbital modulation on a possible CW sig-
nal would be of the order of ∆
f
bin
≈
10
−
10
Hz, that
10
20
100
400
10
-26
10
-25
10
-24
O1 Upper-limits
O2 Upper-limits
O2 Opper-limits BG
O2 Upper-limits AG
LHO O2 sensitivity (232 days)
LLO O2 sensitivity (232 days)
LLO O1 sensitivity (141 days)
LHO O1 sensitivity (141 days)
Spin-down limit
FIG. 1.
Vertical axis:
CW amplitude,
horizontal axis:
searched GW frequencies. The different lines indicate the es
timated
search sensitivity for O1 and O2 narrow-band searches, whil
e the different markers indicate ULs. The labels “AG” and “ BG”
refers to a search performed after or before the glitch of a gi
ven pulsar. The error bars correspond to the uncertainties o
n the
pulsar distance and correspond to 1
σ
confidence level.