First narrow-band search for continuous gravitational waves from known pulsars in
advanced detector data
B. P. Abbott,
1
R. Abbott,
1
T. D. Abbott,
2
F. Acernese,
3
,
4
K. Ackley,
5
,
6
C. Adams,
7
T. Adams,
8
P. Addesso,
9
R. X. Adhikari,
1
V. B. Adya,
10
C. Affeldt,
10
M. Afrough,
11
B. Agarwal,
12
M. Agathos,
13
K. Agatsuma,
14
N. Aggarwal,
15
O. D. Aguiar,
16
L. Aiello,
17
,
18
A. Ain,
19
B. Allen,
10
,
20
,
21
G. Allen,
12
A. Allocca,
22
,
23
P. A. Altin,
24
A. Amato,
25
A. Ananyeva,
1
S. B. Anderson,
1
W. G. Anderson,
20
S. V. Angelova,
26
S. Antier,
27
S. Appert,
1
K. Arai,
1
M. C. Araya,
1
J. S. Areeda,
28
N. Arnaud,
27
,
29
K. G. Arun,
30
S. Ascenzi,
31
,
32
G. Ashton,
10
M. Ast,
33
S. M. Aston,
7
P. Astone,
34
D. V. Atallah,
35
P. Aufmuth,
21
C. Aulbert,
10
K. AultONeal,
36
C. Austin,
2
A. Avila-Alvarez,
28
S. Babak,
37
P. Bacon,
38
M. K. M. Bader,
14
S. Bae,
39
P. T. Baker,
40
F. Baldaccini,
41
,
42
G. Ballardin,
29
S. W. Ballmer,
43
S. Banagiri,
44
J. C. Barayoga,
1
S. E. Barclay,
45
B. C. Barish,
1
D. Barker,
46
K. Barkett,
47
F. Barone,
3
,
4
B. Barr,
45
L. Barsotti,
15
M. Barsuglia,
38
D. Barta,
48
J. Bartlett,
46
I. Bartos,
49
,
5
R. Bassiri,
50
A. Basti,
22
,
23
J. C. Batch,
46
M. Bawaj,
51
,
42
J. C. Bayley,
45
M. Bazzan,
52
,
53
B. B ́ecsy,
54
C. Beer,
10
M. Bejger,
55
I. Belahcene,
27
A. S. Bell,
45
B. K. Berger,
1
G. Bergmann,
10
J. J. Bero,
56
C. P. L. Berry,
57
D. Bersanetti,
58
A. Bertolini,
14
J. Betzwieser,
7
S. Bhagwat,
43
R. Bhandare,
59
I. A. Bilenko,
60
G. Billingsley,
1
C. R. Billman,
5
J. Birch,
7
R. Birney,
61
O. Birnholtz,
10
S. Biscans,
1
,
15
S. Biscoveanu,
62
,
6
A. Bisht,
21
M. Bitossi,
29
,
23
C. Biwer,
43
M. A. Bizouard,
27
J. K. Blackburn,
1
J. Blackman,
47
C. D. Blair,
1
,
63
D. G. Blair,
63
R. M. Blair,
46
S. Bloemen,
64
O. Bock,
10
N. Bode,
10
M. Boer,
65
G. Bogaert,
65
A. Bohe,
37
F. Bondu,
66
E. Bonilla,
50
R. Bonnand,
8
B. A. Boom,
14
R. Bork,
1
V. Boschi,
29
,
23
S. Bose,
67
,
19
K. Bossie,
7
Y. Bouffanais,
38
A. Bozzi,
29
C. Bradaschia,
23
P. R. Brady,
20
M. Branchesi,
17
,
18
J. E. Brau,
68
T. Briant,
69
A. Brillet,
65
M. Brinkmann,
10
V. Brisson,
27
P. Brockill,
20
J. E. Broida,
70
A. F. Brooks,
1
D. A. Brown,
43
D. D. Brown,
71
S. Brunett,
1
C. C. Buchanan,
2
A. Buikema,
15
T. Bulik,
72
H. J. Bulten,
73
,
14
A. Buonanno,
37
,
74
D. Buskulic,
8
C. Buy,
38
R. L. Byer,
50
M. Cabero,
10
L. Cadonati,
75
G. Cagnoli,
25
,
76
C. Cahillane,
1
J. Calder ́on Bustillo,
75
T. A. Callister,
1
E. Calloni,
77
,
4
J. B. Camp,
78
P. Canizares,
64
K. C. Cannon,
79
H. Cao,
71
J. Cao,
80
C. D. Capano,
10
E. Capocasa,
38
F. Carbognani,
29
S. Caride,
81
M. F. Carney,
82
J. Casanueva Diaz,
27
C. Casentini,
31
,
32
S. Caudill,
20
,
14
M. Cavagli`a,
11
F. Cavalier,
27
R. Cavalieri,
29
G. Cella,
23
C. B. Cepeda,
1
P. Cerd ́a-Dur ́an,
83
G. Cerretani,
22
,
23
E. Cesarini,
84
,
32
S. J. Chamberlin,
62
M. Chan,
45
S. Chao,
85
P. Charlton,
86
E. Chase,
87
E. Chassande-Mottin,
38
D. Chatterjee,
20
B. D. Cheeseboro,
40
H. Y. Chen,
88
X. Chen,
63
Y. Chen,
47
H.-P. Cheng,
5
H. Chia,
5
A. Chincarini,
58
A. Chiummo,
29
T. Chmiel,
82
H. S. Cho,
89
M. Cho,
74
J. H. Chow,
24
N. Christensen,
70
,
65
Q. Chu,
63
A. J. K. Chua,
13
S. Chua,
69
A. K. W. Chung,
90
S. Chung,
63
G. Ciani,
5
,
52
,
53
R. Ciolfi,
91
,
92
C. E. Cirelli,
50
A. Cirone,
93
,
58
F. Clara,
46
J. A. Clark,
75
P. Clearwater,
94
F. Cleva,
65
C. Cocchieri,
11
E. Coccia,
17
,
18
P.-F. Cohadon,
69
D. Cohen,
27
A. Colla,
95
,
34
C. G. Collette,
96
L. R. Cominsky,
97
M. Constancio Jr.,
16
L. Conti,
53
S. J. Cooper,
57
P. Corban,
7
T. R. Corbitt,
2
I. Cordero-Carri ́on,
98
K. R. Corley,
49
N. Cornish,
99
A. Corsi,
81
S. Cortese,
29
C. A. Costa,
16
M. W. Coughlin,
70
,
1
S. B. Coughlin,
87
J.-P. Coulon,
65
S. T. Countryman,
49
P. Couvares,
1
P. B. Covas,
100
E. E. Cowan,
75
D. M. Coward,
63
M. J. Cowart,
7
D. C. Coyne,
1
R. Coyne,
81
J. D. E. Creighton,
20
T. D. Creighton,
101
J. Cripe,
2
S. G. Crowder,
102
T. J. Cullen,
28
,
2
A. Cumming,
45
L. Cunningham,
45
E. Cuoco,
29
T. Dal Canton,
78
G. D ́alya,
54
S. L. Danilishin,
21
,
10
S. D’Antonio,
32
K. Danzmann,
21
,
10
A. Dasgupta,
103
C. F. Da Silva Costa,
5
V. Dattilo,
29
I. Dave,
59
M. Davier,
27
D. Davis,
43
E. J. Daw,
104
B. Day,
75
S. De,
43
D. DeBra,
50
J. Degallaix,
25
M. De Laurentis,
17
,
4
S. Del ́eglise,
69
W. Del Pozzo,
57
,
22
,
23
N. Demos,
15
T. Denker,
10
T. Dent,
10
R. De Pietri,
105
,
106
V. Dergachev,
37
R. De Rosa,
77
,
4
R. T. DeRosa,
7
C. De Rossi,
25
,
29
R. DeSalvo,
107
O. de Varona,
10
J. Devenson,
26
S. Dhurandhar,
19
M. C. D ́ıaz,
101
L. Di Fiore,
4
M. Di Giovanni,
108
,
92
T. Di Girolamo,
49
,
77
,
4
A. Di Lieto,
22
,
23
S. Di Pace,
95
,
34
I. Di Palma,
95
,
34
F. Di Renzo,
22
,
23
Z. Doctor,
88
V. Dolique,
25
F. Donovan,
15
K. L. Dooley,
11
S. Doravari,
10
I. Dorrington,
35
R. Douglas,
45
M. Dovale
́
Alvarez,
57
T. P. Downes,
20
M. Drago,
10
C. Dreissigacker,
10
J. C. Driggers,
46
Z. Du,
80
M. Ducrot,
8
P. Dupej,
45
S. E. Dwyer,
46
T. B. Edo,
104
M. C. Edwards,
70
A. Effler,
7
H.-B. Eggenstein,
37
,
10
P. Ehrens,
1
J. Eichholz,
1
S. S. Eikenberry,
5
R. A. Eisenstein,
15
R. C. Essick,
15
D. Estevez,
8
Z. B. Etienne,
40
T. Etzel,
1
M. Evans,
15
T. M. Evans,
7
M. Factourovich,
49
V. Fafone,
31
,
32
,
17
H. Fair,
43
S. Fairhurst,
35
X. Fan,
80
S. Farinon,
58
B. Farr,
88
W. M. Farr,
57
E. J. Fauchon-Jones,
35
M. Favata,
109
M. Fays,
35
C. Fee,
82
H. Fehrmann,
10
J. Feicht,
1
M. M. Fejer,
50
A. Fernandez-Galiana,
15
I. Ferrante,
22
,
23
E. C. Ferreira,
16
F. Ferrini,
29
F. Fidecaro,
22
,
23
D. Finstad,
43
I. Fiori,
29
D. Fiorucci,
38
M. Fishbach,
88
R. P. Fisher,
43
M. Fitz-Axen,
44
R. Flaminio,
25
,
110
M. Fletcher,
45
H. Fong,
111
J. A. Font,
83
,
112
P. W. F. Forsyth,
24
S. S. Forsyth,
75
J.-D. Fournier,
65
S. Frasca,
95
,
34
F. Frasconi,
23
Z. Frei,
54
A. Freise,
57
R. Frey,
68
V. Frey,
27
E. M. Fries,
1
P. Fritschel,
15
V. V. Frolov,
7
P. Fulda,
5
M. Fyffe,
7
H. Gabbard,
45
B. U. Gadre,
19
S. M. Gaebel,
57
J. R. Gair,
113
L. Gammaitoni,
41
M. R. Ganija,
71
S. G. Gaonkar,
19
C. Garcia-Quiros,
100
F. Garufi,
77
,
4
B. Gateley,
46
S. Gaudio,
36
G. Gaur,
114
V. Gayathri,
115
arXiv:1710.02327v2 [gr-qc] 5 Dec 2017
2
N. Gehrels
†
,
78
G. Gemme,
58
E. Genin,
29
A. Gennai,
23
D. George,
12
J. George,
59
L. Gergely,
116
V. Germain,
8
S. Ghonge,
75
Abhirup Ghosh,
117
Archisman Ghosh,
117
,
14
S. Ghosh,
64
,
14
,
20
J. A. Giaime,
2
,
7
K. D. Giardina,
7
A. Giazotto,
23
K. Gill,
36
L. Glover,
107
E. Goetz,
118
R. Goetz,
5
S. Gomes,
35
B. Goncharov,
6
G. Gonz ́alez,
2
J. M. Gonzalez Castro,
22
,
23
A. Gopakumar,
119
M. L. Gorodetsky,
60
S. E. Gossan,
1
M. Gosselin,
29
R. Gouaty,
8
A. Grado,
120
,
4
C. Graef,
45
M. Granata,
25
A. Grant,
45
S. Gras,
15
C. Gray,
46
G. Greco,
121
,
122
A. C. Green,
57
E. M. Gretarsson,
36
P. Groot,
64
H. Grote,
10
S. Grunewald,
37
P. Gruning,
27
G. M. Guidi,
121
,
122
X. Guo,
80
A. Gupta,
62
M. K. Gupta,
103
K. E. Gushwa,
1
E. K. Gustafson,
1
R. Gustafson,
118
O. Halim,
18
,
17
B. R. Hall,
67
E. D. Hall,
15
E. Z. Hamilton,
35
G. Hammond,
45
M. Haney,
123
M. M. Hanke,
10
J. Hanks,
46
C. Hanna,
62
M. D. Hannam,
35
O. A. Hannuksela,
90
J. Hanson,
7
T. Hardwick,
2
J. Harms,
17
,
18
G. M. Harry,
124
I. W. Harry,
37
M. J. Hart,
45
C.-J. Haster,
111
K. Haughian,
45
J. Healy,
56
A. Heidmann,
69
M. C. Heintze,
7
H. Heitmann,
65
P. Hello,
27
G. Hemming,
29
M. Hendry,
45
I. S. Heng,
45
J. Hennig,
45
A. W. Heptonstall,
1
M. Heurs,
10
,
21
S. Hild,
45
T. Hinderer,
64
W. C. G. Ho,
126
D. Hoak,
29
D. Hofman,
25
K. Holt,
7
D. E. Holz,
88
P. Hopkins,
35
C. Horst,
20
J. Hough,
45
E. A. Houston,
45
E. J. Howell,
63
A. Hreibi,
65
Y. M. Hu,
10
E. A. Huerta,
12
D. Huet,
27
B. Hughey,
36
S. Husa,
100
S. H. Huttner,
45
T. Huynh-Dinh,
7
N. Indik,
10
R. Inta,
81
G. Intini,
95
,
34
H. N. Isa,
45
J.-M. Isac,
69
M. Isi,
1
B. R. Iyer,
117
K. Izumi,
46
T. Jacqmin,
69
K. Jani,
75
P. Jaranowski,
125
S. Jawahar,
61
F. Jim ́enez-Forteza,
100
W. W. Johnson,
2
D. I. Jones,
126
R. Jones,
45
R. J. G. Jonker,
14
L. Ju,
63
J. Junker,
10
C. V. Kalaghatgi,
35
V. Kalogera,
87
B. Kamai,
1
S. Kandhasamy,
7
G. Kang,
39
J. B. Kanner,
1
S. J. Kapadia,
20
S. Karki,
68
K. S. Karvinen,
10
M. Kasprzack,
2
M. Katolik,
12
E. Katsavounidis,
15
W. Katzman,
7
S. Kaufer,
21
K. Kawabe,
46
F. K ́ef ́elian,
65
D. Keitel,
45
A. J. Kemball,
12
R. Kennedy,
104
C. Kent,
35
J. S. Key,
127
F. Y. Khalili,
60
I. Khan,
17
,
32
S. Khan,
10
Z. Khan,
103
E. A. Khazanov,
128
N. Kijbunchoo,
24
Chunglee Kim,
129
J. C. Kim,
130
K. Kim,
90
W. Kim,
71
W. S. Kim,
131
Y.-M. Kim,
89
S. J. Kimbrell,
75
E. J. King,
71
P. J. King,
46
M. Kinley-Hanlon,
124
R. Kirchhoff,
10
J. S. Kissel,
46
L. Kleybolte,
33
S. Klimenko,
5
T. D. Knowles,
40
P. Koch,
10
S. M. Koehlenbeck,
10
S. Koley,
14
V. Kondrashov,
1
A. Kontos,
15
M. Korobko,
33
W. Z. Korth,
1
I. Kowalska,
72
D. B. Kozak,
1
C. Kr ̈amer,
10
V. Kringel,
10
B. Krishnan,
10
A. Kr ́olak,
132
,
133
G. Kuehn,
10
P. Kumar,
111
R. Kumar,
103
S. Kumar,
117
L. Kuo,
85
A. Kutynia,
132
S. Kwang,
20
B. D. Lackey,
37
K. H. Lai,
90
M. Landry,
46
R. N. Lang,
134
J. Lange,
56
B. Lantz,
50
R. K. Lanza,
15
A. Lartaux-Vollard,
27
P. D. Lasky,
6
M. Laxen,
7
A. Lazzarini,
1
C. Lazzaro,
53
P. Leaci,
95
,
34
S. Leavey,
45
C. H. Lee,
89
H. K. Lee,
135
H. M. Lee,
136
H. W. Lee,
130
K. Lee,
45
J. Lehmann,
10
A. Lenon,
40
M. Leonardi,
108
,
92
N. Leroy,
27
N. Letendre,
8
Y. Levin,
6
T. G. F. Li,
90
S. D. Linker,
107
T. B. Littenberg,
137
J. Liu,
63
R. K. L. Lo,
90
N. A. Lockerbie,
61
L. T. London,
35
J. E. Lord,
43
M. Lorenzini,
17
,
18
V. Loriette,
138
M. Lormand,
7
G. Losurdo,
23
J. D. Lough,
10
G. Lovelace,
28
H. L ̈uck,
21
,
10
D. Lumaca,
31
,
32
A. P. Lundgren,
10
R. Lynch,
15
Y. Ma,
47
R. Macas,
35
S. Macfoy,
26
B. Machenschalk,
10
M. MacInnis,
15
D. M. Macleod,
35
I. Maga ̃na Hernandez,
20
F. Maga ̃na-Sandoval,
43
L. Maga ̃na Zertuche,
43
R. M. Magee,
62
E. Majorana,
34
I. Maksimovic,
138
N. Man,
65
V. Mandic,
44
V. Mangano,
45
G. L. Mansell,
24
M. Manske,
20
,
24
M. Mantovani,
29
F. Marchesoni,
51
,
42
F. Marion,
8
S. M ́arka,
49
Z. M ́arka,
49
C. Markakis,
12
A. S. Markosyan,
50
A. Markowitz,
1
E. Maros,
1
A. Marquina,
98
F. Martelli,
121
,
122
L. Martellini,
65
I. W. Martin,
45
R. M. Martin,
109
D. V. Martynov,
15
K. Mason,
15
E. Massera,
104
A. Masserot,
8
T. J. Massinger,
1
M. Masso-Reid,
45
S. Mastrogiovanni,
95
,
34
A. Matas,
44
F. Matichard,
1
,
15
L. Matone,
49
N. Mavalvala,
15
N. Mazumder,
67
R. McCarthy,
46
D. E. McClelland,
24
S. McCormick,
7
L. McCuller,
15
S. C. McGuire,
139
G. McIntyre,
1
J. McIver,
1
D. J. McManus,
24
L. McNeill,
6
T. McRae,
24
S. T. McWilliams,
40
D. Meacher,
62
G. D. Meadors,
37
,
10
M. Mehmet,
10
J. Meidam,
14
E. Mejuto-Villa,
9
A. Melatos,
94
G. Mendell,
46
R. A. Mercer,
20
E. L. Merilh,
46
M. Merzougui,
65
S. Meshkov,
1
C. Messenger,
45
C. Messick,
62
R. Metzdorff,
69
P. M. Meyers,
44
H. Miao,
57
C. Michel,
25
H. Middleton,
57
E. E. Mikhailov,
140
L. Milano,
77
,
4
A. L. Miller,
5
,
95
,
34
B. B. Miller,
87
J. Miller,
15
M. Millhouse,
99
M. C. Milovich-Goff,
107
O. Minazzoli,
65
,
141
Y. Minenkov,
32
J. Ming,
37
C. Mishra,
142
S. Mitra,
19
V. P. Mitrofanov,
60
G. Mitselmakher,
5
R. Mittleman,
15
D. Moffa,
82
A. Moggi,
23
K. Mogushi,
11
M. Mohan,
29
S. R. P. Mohapatra,
15
M. Montani,
121
,
122
C. J. Moore,
13
D. Moraru,
46
G. Moreno,
46
S. R. Morriss,
101
B. Mours,
8
C. M. Mow-Lowry,
57
G. Mueller,
5
A. W. Muir,
35
Arunava Mukherjee,
10
D. Mukherjee,
20
S. Mukherjee,
101
N. Mukund,
19
A. Mullavey,
7
J. Munch,
71
E. A. Mu ̃niz,
43
M. Muratore,
36
P. G. Murray,
45
K. Napier,
75
I. Nardecchia,
31
,
32
L. Naticchioni,
95
,
34
R. K. Nayak,
143
J. Neilson,
107
G. Nelemans,
64
,
14
T. J. N. Nelson,
7
M. Nery,
10
A. Neunzert,
118
L. Nevin,
1
J. M. Newport,
124
G. Newton
‡
,
45
K. K. Y. Ng,
90
T. T. Nguyen,
24
D. Nichols,
64
A. B. Nielsen,
10
S. Nissanke,
64
,
14
A. Nitz,
10
A. Noack,
10
F. Nocera,
29
D. Nolting,
7
C. North,
35
L. K. Nuttall,
35
J. Oberling,
46
G. D. O’Dea,
107
G. H. Ogin,
144
J. J. Oh,
131
S. H. Oh,
131
F. Ohme,
10
M. A. Okada,
16
M. Oliver,
100
P. Oppermann,
10
Richard J. Oram,
7
B. O’Reilly,
7
R. Ormiston,
44
L. F. Ortega,
5
R. O’Shaughnessy,
56
S. Ossokine,
37
D. J. Ottaway,
71
H. Overmier,
7
B. J. Owen,
81
A. E. Pace,
62
J. Page,
137
M. A. Page,
63
A. Pai,
115
,
145
S. A. Pai,
59
J. R. Palamos,
68
O. Palashov,
128
3
C. Palomba,
34
A. Pal-Singh,
33
Howard Pan,
85
Huang-Wei Pan,
85
B. Pang,
47
P. T. H. Pang,
90
C. Pankow,
87
F. Pannarale,
35
B. C. Pant,
59
F. Paoletti,
23
A. Paoli,
29
M. A. Papa,
37
,
20
,
10
A. Parida,
19
W. Parker,
7
D. Pascucci,
45
A. Pasqualetti,
29
R. Passaquieti,
22
,
23
D. Passuello,
23
M. Patil,
133
B. Patricelli,
146
,
23
B. L. Pearlstone,
45
M. Pedraza,
1
R. Pedurand,
25
,
147
L. Pekowsky,
43
A. Pele,
7
S. Penn,
148
C. J. Perez,
46
A. Perreca,
1
,
108
,
92
L. M. Perri,
87
H. P. Pfeiffer,
111
,
37
M. Phelps,
45
O. J. Piccinni,
95
,
34
M. Pichot,
65
F. Piergiovanni,
121
,
122
V. Pierro,
9
G. Pillant,
29
L. Pinard,
25
I. M. Pinto,
9
M. Pirello,
46
M. Pitkin,
45
M. Poe,
20
R. Poggiani,
22
,
23
P. Popolizio,
29
E. K. Porter,
38
A. Post,
10
J. Powell,
45
,
149
J. Prasad,
19
J. W. W. Pratt,
36
G. Pratten,
100
V. Predoi,
35
T. Prestegard,
20
M. Prijatelj,
10
M. Principe,
9
S. Privitera,
37
G. A. Prodi,
108
,
92
L. G. Prokhorov,
60
O. Puncken,
10
M. Punturo,
42
P. Puppo,
34
M. P ̈urrer,
37
H. Qi,
20
V. Quetschke,
101
E. A. Quintero,
1
R. Quitzow-James,
68
F. J. Raab,
46
D. S. Rabeling,
24
H. Radkins,
46
P. Raffai,
54
S. Raja,
59
C. Rajan,
59
B. Rajbhandari,
81
M. Rakhmanov,
101
K. E. Ramirez,
101
A. Ramos-Buades,
100
P. Rapagnani,
95
,
34
V. Raymond,
37
M. Razzano,
22
,
23
J. Read,
28
T. Regimbau,
65
L. Rei,
58
S. Reid,
61
D. H. Reitze,
1
,
5
W. Ren,
12
S. D. Reyes,
43
F. Ricci,
95
,
34
P. M. Ricker,
12
S. Rieger,
10
K. Riles,
118
M. Rizzo,
56
N. A. Robertson,
1
,
45
R. Robie,
45
F. Robinet,
27
A. Rocchi,
32
L. Rolland,
8
J. G. Rollins,
1
V. J. Roma,
68
R. Romano,
3
,
4
C. L. Romel,
46
J. H. Romie,
7
D. Rosi ́nska,
150
,
55
M. P. Ross,
151
S. Rowan,
45
A. R ̈udiger,
10
P. Ruggi,
29
G. Rutins,
26
K. Ryan,
46
S. Sachdev,
1
T. Sadecki,
46
L. Sadeghian,
20
M. Sakellariadou,
152
L. Salconi,
29
M. Saleem,
115
F. Salemi,
10
A. Samajdar,
143
L. Sammut,
6
L. M. Sampson,
87
E. J. Sanchez,
1
L. E. Sanchez,
1
N. Sanchis-Gual,
83
V. Sandberg,
46
J. R. Sanders,
43
B. Sassolas,
25
B. S. Sathyaprakash,
62
,
35
P. R. Saulson,
43
O. Sauter,
118
R. L. Savage,
46
A. Sawadsky,
33
P. Schale,
68
M. Scheel,
47
J. Scheuer,
87
J. Schmidt,
10
P. Schmidt,
1
,
64
R. Schnabel,
33
R. M. S. Schofield,
68
A. Sch ̈onbeck,
33
E. Schreiber,
10
D. Schuette,
10
,
21
B. W. Schulte,
10
B. F. Schutz,
35
,
10
S. G. Schwalbe,
36
J. Scott,
45
S. M. Scott,
24
E. Seidel,
12
D. Sellers,
7
A. S. Sengupta,
153
D. Sentenac,
29
V. Sequino,
31
,
32
,
17
A. Sergeev,
128
D. A. Shaddock,
24
T. J. Shaffer,
46
A. A. Shah,
137
M. S. Shahriar,
87
M. B. Shaner,
107
L. Shao,
37
B. Shapiro,
50
P. Shawhan,
74
A. Sheperd,
20
D. H. Shoemaker,
15
D. M. Shoemaker,
75
K. Siellez,
75
X. Siemens,
20
M. Sieniawska,
55
D. Sigg,
46
A. D. Silva,
16
L. P. Singer,
78
A. Singh,
37
,
10
,
21
A. Singhal,
17
,
34
A. M. Sintes,
100
B. J. J. Slagmolen,
24
B. Smith,
7
J. R. Smith,
28
R. J. E. Smith,
1
,
6
S. Somala,
154
E. J. Son,
131
J. A. Sonnenberg,
20
B. Sorazu,
45
F. Sorrentino,
58
T. Souradeep,
19
A. P. Spencer,
45
A. K. Srivastava,
103
K. Staats,
36
A. Staley,
49
M. Steinke,
10
J. Steinlechner,
33
,
45
S. Steinlechner,
33
D. Steinmeyer,
10
S. P. Stevenson,
57
,
149
R. Stone,
101
D. J. Stops,
57
K. A. Strain,
45
G. Stratta,
121
,
122
S. E. Strigin,
60
A. Strunk,
46
R. Sturani,
155
A. L. Stuver,
7
T. Z. Summerscales,
156
L. Sun,
94
S. Sunil,
103
J. Suresh,
19
P. J. Sutton,
35
B. L. Swinkels,
29
M. J. Szczepa ́nczyk,
36
M. Tacca,
14
S. C. Tait,
45
C. Talbot,
6
D. Talukder,
68
D. B. Tanner,
5
M. T ́apai,
116
A. Taracchini,
37
J. D. Tasson,
70
J. A. Taylor,
137
R. Taylor,
1
S. V. Tewari,
148
T. Theeg,
10
F. Thies,
10
E. G. Thomas,
57
M. Thomas,
7
P. Thomas,
46
K. A. Thorne,
7
E. Thrane,
6
S. Tiwari,
17
,
92
V. Tiwari,
35
K. V. Tokmakov,
61
K. Toland,
45
M. Tonelli,
22
,
23
Z. Tornasi,
45
A. Torres-Forn ́e,
83
C. I. Torrie,
1
D. T ̈oyr ̈a,
57
F. Travasso,
29
,
42
G. Traylor,
7
J. Trinastic,
5
M. C. Tringali,
108
,
92
L. Trozzo,
157
,
23
K. W. Tsang,
14
M. Tse,
15
R. Tso,
1
L. Tsukada,
79
D. Tsuna,
79
D. Tuyenbayev,
101
K. Ueno,
20
D. Ugolini,
158
C. S. Unnikrishnan,
119
A. L. Urban,
1
S. A. Usman,
35
H. Vahlbruch,
21
G. Vajente,
1
G. Valdes,
2
N. van Bakel,
14
M. van Beuzekom,
14
J. F. J. van den Brand,
73
,
14
C. Van Den Broeck,
14
D. C. Vander-Hyde,
43
L. van der Schaaf,
14
J. V. van Heijningen,
14
A. A. van Veggel,
45
M. Vardaro,
52
,
53
V. Varma,
47
S. Vass,
1
M. Vas ́uth,
48
A. Vecchio,
57
G. Vedovato,
53
J. Veitch,
45
P. J. Veitch,
71
K. Venkateswara,
151
G. Venugopalan,
1
D. Verkindt,
8
F. Vetrano,
121
,
122
A. Vicer ́e,
121
,
122
A. D. Viets,
20
S. Vinciguerra,
57
D. J. Vine,
26
J.-Y. Vinet,
65
S. Vitale,
15
T. Vo,
43
H. Vocca,
41
,
42
C. Vorvick,
46
S. P. Vyatchanin,
60
A. R. Wade,
1
L. E. Wade,
82
M. Wade,
82
R. Walet,
14
M. Walker,
28
L. Wallace,
1
S. Walsh,
37
,
10
,
20
G. Wang,
17
,
122
H. Wang,
57
J. Z. Wang,
62
W. H. Wang,
101
Y. F. Wang,
90
R. L. Ward,
24
J. Warner,
46
M. Was,
8
J. Watchi,
96
B. Weaver,
46
L.-W. Wei,
10
,
21
M. Weinert,
10
A. J. Weinstein,
1
R. Weiss,
15
L. Wen,
63
E. K. Wessel,
12
P. Weßels,
10
J. Westerweck,
10
T. Westphal,
10
K. Wette,
24
J. T. Whelan,
56
B. F. Whiting,
5
C. Whittle,
6
D. Wilken,
10
D. Williams,
45
R. D. Williams,
1
A. R. Williamson,
64
J. L. Willis,
1
,
159
B. Willke,
21
,
10
M. H. Wimmer,
10
W. Winkler,
10
C. C. Wipf,
1
H. Wittel,
10
,
21
G. Woan,
45
J. Woehler,
10
J. Wofford,
56
K. W. K. Wong,
90
J. Worden,
46
J. L. Wright,
45
D. S. Wu,
10
D. M. Wysocki,
56
S. Xiao,
1
H. Yamamoto,
1
C. C. Yancey,
74
L. Yang,
160
M. J. Yap,
24
M. Yazback,
5
Hang Yu,
15
Haocun Yu,
15
M. Yvert,
8
A. Zadro ̇zny,
132
M. Zanolin,
36
T. Zelenova,
29
J.-P. Zendri,
53
M. Zevin,
87
L. Zhang,
1
M. Zhang,
140
T. Zhang,
45
Y.-H. Zhang,
56
C. Zhao,
63
M. Zhou,
87
Z. Zhou,
87
S. J. Zhu,
37
,
10
X. J. Zhu,
6
M. E. Zucker,
1
,
15
and J. Zweizig
1
(LIGO Scientific Collaboration and Virgo Collaboration)
†
Deceased, February 2017.
‡
Deceased, December 2016.
1
LIGO, California Institute of Technology, Pasadena, CA 91125, USA
2
Louisiana State University, Baton Rouge, LA 70803, USA
4
3
Universit`a di Salerno, Fisciano, I-84084 Salerno, Italy
4
INFN, Sezione di Napoli, Complesso Universitario di Monte S.Angelo, I-80126 Napoli, Italy
5
University of Florida, Gainesville, FL 32611, USA
6
OzGrav, School of Physics & Astronomy, Monash University, Clayton 3800, Victoria, Australia
7
LIGO Livingston Observatory, Livingston, LA 70754, USA
8
Laboratoire d’Annecy-le-Vieux de Physique des Particules (LAPP),
Universit ́e Savoie Mont Blanc, CNRS/IN2P3, F-74941 Annecy, France
9
University of Sannio at Benevento, I-82100 Benevento,
Italy and INFN, Sezione di Napoli, I-80100 Napoli, Italy
10
Max Planck Institute for Gravitational Physics (Albert Einstein Institute), D-30167 Hannover, Germany
11
The University of Mississippi, University, MS 38677, USA
12
NCSA, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
13
University of Cambridge, Cambridge CB2 1TN, United Kingdom
14
Nikhef, Science Park, 1098 XG Amsterdam, The Netherlands
15
LIGO, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
16
Instituto Nacional de Pesquisas Espaciais, 12227-010 S ̃ao Jos ́e dos Campos, S ̃ao Paulo, Brazil
17
Gran Sasso Science Institute (GSSI), I-67100 L’Aquila, Italy
18
INFN, Laboratori Nazionali del Gran Sasso, I-67100 Assergi, Italy
19
Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India
20
University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
21
Leibniz Universit ̈at Hannover, D-30167 Hannover, Germany
22
Universit`a di Pisa, I-56127 Pisa, Italy
23
INFN, Sezione di Pisa, I-56127 Pisa, Italy
24
OzGrav, Australian National University, Canberra, Australian Capital Territory 0200, Australia
25
Laboratoire des Mat ́eriaux Avanc ́es (LMA), CNRS/IN2P3, F-69622 Villeurbanne, France
26
SUPA, University of the West of Scotland, Paisley PA1 2BE, United Kingdom
27
LAL, Univ. Paris-Sud, CNRS/IN2P3, Universit ́e Paris-Saclay, F-91898 Orsay, France
28
California State University Fullerton, Fullerton, CA 92831, USA
29
European Gravitational Observatory (EGO), I-56021 Cascina, Pisa, Italy
30
Chennai Mathematical Institute, Chennai 603103, India
31
Universit`a di Roma Tor Vergata, I-00133 Roma, Italy
32
INFN, Sezione di Roma Tor Vergata, I-00133 Roma, Italy
33
Universit ̈at Hamburg, D-22761 Hamburg, Germany
34
INFN, Sezione di Roma, I-00185 Roma, Italy
35
Cardiff University, Cardiff CF24 3AA, United Kingdom
36
Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA
37
Max Planck Institute for Gravitational Physics (Albert Einstein Institute), D-14476 Potsdam-Golm, Germany
38
APC, AstroParticule et Cosmologie, Universit ́e Paris Diderot,
CNRS/IN2P3, CEA/Irfu, Observatoire de Paris,
Sorbonne Paris Cit ́e, F-75205 Paris Cedex 13, France
39
Korea Institute of Science and Technology Information, Daejeon 34141, Korea
40
West Virginia University, Morgantown, WV 26506, USA
41
Universit`a di Perugia, I-06123 Perugia, Italy
42
INFN, Sezione di Perugia, I-06123 Perugia, Italy
43
Syracuse University, Syracuse, NY 13244, USA
44
University of Minnesota, Minneapolis, MN 55455, USA
45
SUPA, University of Glasgow, Glasgow G12 8QQ, United Kingdom
46
LIGO Hanford Observatory, Richland, WA 99352, USA
47
Caltech CaRT, Pasadena, CA 91125, USA
48
Wigner RCP, RMKI, H-1121 Budapest, Konkoly Thege Mikl ́os ́ut 29-33, Hungary
49
Columbia University, New York, NY 10027, USA
50
Stanford University, Stanford, CA 94305, USA
51
Universit`a di Camerino, Dipartimento di Fisica, I-62032 Camerino, Italy
52
Universit`a di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova, Italy
53
INFN, Sezione di Padova, I-35131 Padova, Italy
54
Institute of Physics, E ̈otv ̈os University, P ́azm ́any P. s. 1/A, Budapest 1117, Hungary
55
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, 00-716, Warsaw, Poland
56
Rochester Institute of Technology, Rochester, NY 14623, USA
57
University of Birmingham, Birmingham B15 2TT, United Kingdom
58
INFN, Sezione di Genova, I-16146 Genova, Italy
59
RRCAT, Indore MP 452013, India
60
Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
61
SUPA, University of Strathclyde, Glasgow G1 1XQ, United Kingdom
62
The Pennsylvania State University, University Park, PA 16802, USA
5
63
OzGrav, University of Western Australia, Crawley, Western Australia 6009, Australia
64
Department of Astrophysics/IMAPP, Radboud University Nijmegen,
P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
65
Artemis, Universit ́e Cˆote d’Azur, Observatoire Cˆote d’Azur,
CNRS, CS 34229, F-06304 Nice Cedex 4, France
66
Institut FOTON, CNRS, Universit ́e de Rennes 1, F-35042 Rennes, France
67
Washington State University, Pullman, WA 99164, USA
68
University of Oregon, Eugene, OR 97403, USA
69
Laboratoire Kastler Brossel, UPMC-Sorbonne Universit ́es, CNRS,
ENS-PSL Research University, Coll`ege de France, F-75005 Paris, France
70
Carleton College, Northfield, MN 55057, USA
71
OzGrav, University of Adelaide, Adelaide, South Australia 5005, Australia
72
Astronomical Observatory Warsaw University, 00-478 Warsaw, Poland
73
VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
74
University of Maryland, College Park, MD 20742, USA
75
Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, GA 30332, USA
76
Universit ́e Claude Bernard Lyon 1, F-69622 Villeurbanne, France
77
Universit`a di Napoli ‘Federico II,’ Complesso Universitario di Monte S.Angelo, I-80126 Napoli, Italy
78
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
79
RESCEU, University of Tokyo, Tokyo, 113-0033, Japan.
80
Tsinghua University, Beijing 100084, China
81
Texas Tech University, Lubbock, TX 79409, USA
82
Kenyon College, Gambier, OH 43022, USA
83
Departamento de Astronom ́ıa y Astrof ́ısica, Universitat de Val`encia, E-46100 Burjassot, Val`encia, Spain
84
Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, I-00184 Roma, Italy
85
National Tsing Hua University, Hsinchu City, 30013 Taiwan, Republic of China
86
Charles Sturt University, Wagga Wagga, New South Wales 2678, Australia
87
Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA),
Northwestern University, Evanston, IL 60208, USA
88
University of Chicago, Chicago, IL 60637, USA
89
Pusan National University, Busan 46241, Korea
90
The Chinese University of Hong Kong, Shatin, NT, Hong Kong
91
INAF, Osservatorio Astronomico di Padova, I-35122 Padova, Italy
92
INFN, Trento Institute for Fundamental Physics and Applications, I-38123 Povo, Trento, Italy
93
Dipartimento di Fisica, Universit`a degli Studi di Genova, I-16146 Genova, Italy
94
OzGrav, University of Melbourne, Parkville, Victoria 3010, Australia
95
Universit`a di Roma ‘La Sapienza,’ I-00185 Roma, Italy
96
Universit ́e Libre de Bruxelles, Brussels 1050, Belgium
97
Sonoma State University, Rohnert Park, CA 94928, USA
98
Departamento de Matem ́aticas, Universitat de Val`encia, E-46100 Burjassot, Val`encia, Spain
99
Montana State University, Bozeman, MT 59717, USA
100
Universitat de les Illes Balears, IAC3—IEEC, E-07122 Palma de Mallorca, Spain
101
The University of Texas Rio Grande Valley, Brownsville, TX 78520, USA
102
Bellevue College, Bellevue, WA 98007, USA
103
Institute for Plasma Research, Bhat, Gandhinagar 382428, India
104
The University of Sheffield, Sheffield S10 2TN, United Kingdom
105
Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Universit`a di Parma, I-43124 Parma, Italy
106
INFN, Sezione di Milano Bicocca, Gruppo Collegato di Parma, I-43124 Parma, Italy
107
California State University, Los Angeles, 5151 State University Dr, Los Angeles, CA 90032, USA
108
Universit`a di Trento, Dipartimento di Fisica, I-38123 Povo, Trento, Italy
109
Montclair State University, Montclair, NJ 07043, USA
110
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
111
Canadian Institute for Theoretical Astrophysics,
University of Toronto, Toronto, Ontario M5S 3H8, Canada
112
Observatori Astron`omic, Universitat de Val`encia, E-46980 Paterna, Val`encia, Spain
113
School of Mathematics, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
114
University and Institute of Advanced Research,
Koba Institutional Area, Gandhinagar Gujarat 382007, India
115
IISER-TVM, CET Campus, Trivandrum Kerala 695016, India
116
University of Szeged, D ́om t ́er 9, Szeged 6720, Hungary
117
International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India
118
University of Michigan, Ann Arbor, MI 48109, USA
119
Tata Institute of Fundamental Research, Mumbai 400005, India
120
INAF, Osservatorio Astronomico di Capodimonte, I-80131, Napoli, Italy
6
121
Universit`a degli Studi di Urbino ‘Carlo Bo,’ I-61029 Urbino, Italy
122
INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Firenze, Italy
123
Physik-Institut, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
124
American University, Washington, D.C. 20016, USA
125
University of Bia lystok, 15-424 Bia lystok, Poland
126
University of Southampton, Southampton SO17 1BJ, United Kingdom
127
University of Washington Bothell, 18115 Campus Way NE, Bothell, WA 98011, USA
128
Institute of Applied Physics, Nizhny Novgorod, 603950, Russia
129
Korea Astronomy and Space Science Institute, Daejeon 34055, Korea
130
Inje University Gimhae, South Gyeongsang 50834, Korea
131
National Institute for Mathematical Sciences, Daejeon 34047, Korea
132
NCBJ, 05-400
́
Swierk-Otwock, Poland
133
Institute of Mathematics, Polish Academy of Sciences, 00656 Warsaw, Poland
134
Hillsdale College, Hillsdale, MI 49242, USA
135
Hanyang University, Seoul 04763, Korea
136
Seoul National University, Seoul 08826, Korea
137
NASA Marshall Space Flight Center, Huntsville, AL 35811, USA
138
ESPCI, CNRS, F-75005 Paris, France
139
Southern University and A&M College, Baton Rouge, LA 70813, USA
140
College of William and Mary, Williamsburg, VA 23187, USA
141
Centre Scientifique de Monaco, 8 quai Antoine Ier, MC-98000, Monaco
142
Indian Institute of Technology Madras, Chennai 600036, India
143
IISER-Kolkata, Mohanpur, West Bengal 741252, India
144
Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362 USA
145
Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India
146
Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
147
Universit ́e de Lyon, F-69361 Lyon, France
148
Hobart and William Smith Colleges, Geneva, NY 14456, USA
149
OzGrav, Swinburne University of Technology, Hawthorn VIC 3122, Australia
150
Janusz Gil Institute of Astronomy, University of Zielona G ́ora, 65-265 Zielona G ́ora, Poland
151
University of Washington, Seattle, WA 98195, USA
152
King’s College London, University of London, London WC2R 2LS, United Kingdom
153
Indian Institute of Technology, Gandhinagar Ahmedabad Gujarat 382424, India
154
Indian Institute of Technology Hyderabad, Sangareddy, Khandi, Telangana 502285, India
155
International Institute of Physics, Universidade Federal do Rio Grande do Norte, Natal RN 59078-970, Brazil
156
Andrews University, Berrien Springs, MI 49104, USA
157
Universit`a di Siena, I-53100 Siena, Italy
158
Trinity University, San Antonio, TX 78212, USA
159
Abilene Christian University, Abilene, TX 79699, USA
160
Colorado State University, Fort Collins, CO 80523, USA
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known
pulsars a fully coherent search, based on matched filtering, which uses the position and rotational
parameters obtained from electromagnetic observations, can be carried out. Matched filtering max-
imizes the signal-to-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very
small mismatch between the assumed and the true signal parameters. For this reason,
narrow-band
analyses methods have been developed, allowing a fully coherent search for gravitational waves from
known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe
a narrow-band search of eleven pulsars using data from Advanced LIGO’s first observing run. Al-
though we have found several initial outliers, further studies show no significant evidence for the
presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain
amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched: in the case
of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the
median upper limit across the search bands is below the spin-down limit. This is the most sensitive
narrow-band search for continuous gravitational waves carried out so far.
I. INTRODUCTION
On September 14th 2015 the gravitational wave (GW)
signal emitted by a binary black hole merger was de-
tected by the LIGO interferometers (IFOs) [1] followed
on 26th December 2015, by the detection of a second
event again associated to a binary black hole merger[2],
thus opening the era of gravitational waves astronomy.
More recently, the detection of a third binary black hole
merger on Jan 4th 2017 has been announced[3]. Binary
black hole mergers, however, are not the only detectable
7
FIG. 1. Simplified flowchart of the narrow-band search pipeline for CW. The method relies on the use of FFTs to simultaneously
compute the detection statistic, for each given spin-down value, over the full explored frequency range. See [28] for more details
on the method.
sources of GW. Among the potential sources of GW there
are also spinning neutron stars (NS) asymmetric with re-
spect to their rotation axis. These sources are expected
to emit nearly monochromatic continuous waves (CW),
with a frequency at a given fixed ratio with respect to
the star’s rotational frequency, e.g. two times the rota-
tional frequency for an asymmetric NS rotating around
one of its principal axis of inertia. Different flavors of
CW searches exist, depending on the degree of knowl-
edge on the source parameters.
Targeted
searches assume
source position and rotational parameters to be known
with high accuracy, while
all-sky
searches aim at neu-
tron stars with no observed electromagnetic counterpart.
Various intermediate searches have also been developed.
Among these,
narrow-band
searches are an extension of
targeted searches for which the position of the source
is accurately known but, the rotational parameters are
slightly uncertain. Narrow-band searches allow for a pos-
sible small mismatch between the GW rotational param-
eters and those inferred from electromagnetic observa-
tions. This can be crucial if, for instance, the CW signal
is emitted by a freely precessing neutron star [4], or in the
case no updated ephemeris is available for a given pul-
sar. In both cases a targeted search could assume wrong
rotational parameters, resulting in a significant sensitiv-
ity loss. In this paper we present the results of a fully
coherent, narrow-band search for 11 known pulsars using
data from the first observation run (O1) of the Advanced
LIGO detectors[5]. The paper is organized as follows. In
Sec. II we briefly summarise the main concepts of the
analysis. Sec. III is dedicated to an outline of the anal-
ysis method. Sec. IV describes the selected pulsars. In
Sec. V we discuss the analysis results, while the reader
can refer to the Appendix for some technical details on
the computation of upper limits. Finally, Sec. VI is ded-
icated to the conclusions and future prospects.
II. BACKGROUND
The GW signal emitted by an asymmetric spinning NS
can be written, following the formalism first introduced
in [6], as the real part of:
h
(
t
) =
H
0
(
H
+
A
+
(
t
) +
H
×
A
×
(
t
))
e
2
πif
gw
(
t
)
t
+
iφ
0
(1)
where
f
gw
(
t
) is the GW frequency,
φ
0
an initial phase.
The polarisation amplitudes
H
+
,H
×
are given by:
H
+
=
cos(2
ψ
)
−
iη
sin(2
ψ
)
√
1 +
η
2
, H
×
=
sin(2
ψ
)
−
iη
cos(2
ψ
)
√
1 +
η
2
,
η
being the ratio of the polarisation ellipse semi-minor to
semi-major axis and
ψ
the polarization angle, defined as
the direction of the major axis with respect to the celes-
tial parallel of the source (measured counter-clockwise).
The detector
sidereal response
to the GW polarisations is
encoded in the functions
A
+
(
t
)
,A
×
(
t
). It can be shown
that the waveform defined by Eq. 1 is equivalent to the
GW signal expressed in the more standard formalism of
[8], given the following relations:
η
=
−
2 cos
ι
1 + cos
2
ι
,
(2)
where
ι
is the angle between the line of sight and the star
rotation axis, and
H
0
=
h
0
√
1 + 6 cos
2
ι
+ cos
4
ι
4
(3)
with
h
0
=
1
d
4
π
2
G
c
4
I
zz
f
2
gw
,
(4)
where
d,I
zz
and
are respectively the star’s distance, its
moment of inertia with respect to the rotation axis and
the
ellipticity
, which measures the star’s degree of asym-
metry. The signal at the detector is not monochromatic,
i.e. the frequency
f
gw
(
t
) in Eq. 1 is a function of time.
In fact the signal is modulated by several effects, such
as the
R ̈omer delay
due to the detector motion and the
source’s intrinsic spin-down due to the rotational energy
loss from the source. In order to recover all the signal to
noise ratio all these effects must be properly taken into
account. If we have a measure of the pulsar rotational
8
frequency
f
rot
, frequency derivative
̇
f
rot
and distance
d
,
the GW signal amplitude can be constrained, assuming
that all the rotational energy is lost via gravitational ra-
diation. This strict upper limit, 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
(5)
where
I
38
is the star moment of inertia in unit of
10
38
kg m
2
. The corresponding spin-down limit on the
star equatorial fiducial ellipticity can be easily obtained
from Eq. 4.
sd
= 0
.
237
I
−
1
38
[
h
sd
10
−
24
][
Hz
f
rot
]
2
[
d
1kpc
]
.
(6)
Even in the absence of a detection, establishing an am-
plitude upper limit below the spin-down limit for a given
source is an important milestone, as it allows us to put a
non-trivial constraint on the fraction of rotational energy
lost through GWs.
III. THE ANALYSIS
The results discussed in this paper have been obtained
by searching for CW signals from 11 known pulsars us-
ing data from the O1 run from the Advanced LIGO de-
tectors (Hanford - LIGO H, and Livingston - LIGO L
jointly). The run started on September 12th 2015 at
01:25:03 UTC and 18:29:03 UTC, respectively, and fin-
ished on January 19th 2016 at 17:07:59. LIGO H had
a duty cycle of
∼
60% and LIGO L had a duty cycle of
∼
51%, which correspond respectively to 72 and 62 days
of science data available for the analysis. In this paper we
have used an initial calibration of the data [9]. In order to
perform joint search between the two detectors a common
period from September 13th 2015 to January 12th 2016
1
, with a total observation time of about
T
obs
≈
121 days
is selected. The natural frequency and spin-down grid
spacings of the search are
δf
= 1
/T
obs
≈
9
.
5
·
10
−
8
Hz
and
δ
̇
f
= 1
/T
2
obs
≈
4
.
57
·
10
−
15
Hz/s. A follow-up anal-
ysis based on the LIGO’s second observation Run (O2)
has been carried out, for this dataset we have analysed
data from December 16th 2016 to May 8th 2017, more de-
tails will be given in Appendix C. The analysis pipeline
consists of several steps, schematically depicted in Fig.
1, which we summarise here. The starting point is a
collection of FFTs obtained from several interlaced data
chunks (the short FFT Database - SFDB) built from cal-
ibrated detector data chunks of duration 1024 seconds
[26]. At this stage, a first cleaning procedure is applied
to the data in order to remove large, short-duration dis-
turbances, that could reduce the search sensitivity. A
1
An exception is pulsar J0205+6449, see later.
frequency band is then extracted from the SFDBs cov-
ering typically a range larger (of the order of a factor
of 2) than the frequency region analysed in the narrow-
band search. The actual search frequency and spin-down
bands, ∆
f
and ∆
̇
f
, around the reference values,
f
0
and
̇
f
0
, have been chosen according to the following relations
[10]:
∆
f
= 2
f
0
δ
(7)
∆
̇
f
= 2
̇
f
0
δ,
(8)
δ
being a factor parametrizing a possible discrepancy be-
tween the GW rotation parameters and those derived
from electromagnetic observations.
Previous narrow-
band searches used values of
δ
of the order
∼ O
(10
−
4
),
motivated partly by astrophysical considerations[4], and
partly by computational limitations [27]. Here we exploit
the high computation efficiency of our pipeline to enlarge
the search somewhat, depending on the pulsar, to a range
between
δ
∼
10
−
4
−
10
−
3
. The frequency and spin-down
ranges explored in this analysis are listed in Tab. V.
The narrow-band search is performed using a pipeline
based on the
5-vector method
[27] and, in particular, its
latest implementation, fully described in [28], to which
the reader is referred for more details. The basic idea
is that of exploring a range of frequency and spin-down
values by properly applying barycentric and spin-down
corrections to the data in such a way that a signal would
become monochromatic apart from the sidereal modula-
tion. While a single barycentric correction applied in the
time domain holds for all the explored frequency band,
several spin-down corrections, one for each point in the
spin-down grid, are needed. A detection statistic (DS) is
then computed for each point of the explored parameter
space. By using the FFT algorithm for each given spin-
down value it is possible to compute the statistic simulta-
neously over the whole range of frequencies, this process
is done for each detector, and then data is combined.
The frequency/spin-down plane is then divided into fre-
quency sub-bands (10
−
4
Hz) and, for each of them, the
local maximum, over the spin-down grid, of the DS is
selected as a
candidate
. The initial
outliers
are identi-
fied among the candidates using a threshold nominally
corresponding to 1% (taking into account the number of
trials[27]) on the p-value of the DS’s noise-only distri-
bution
2
and are subject to a follow-up stage in order to
understand their nature. The follow-up procedure con-
sists of the following steps: check if the outlier is close to
known instrumental noise lines; compute the signal am-
plitude and check if it is constant throughout the run,
compute the time evolution of the SNR (which we ex-
pect to increase as the square root of the observation
time for stationary noise) and compute the
5-vector co-
herence
, which is an indicator measuring the degree of
2
The noise-only distribution is computed from the values of the
DS excluded in each frequency sub-band when selecting the local
maxima and then an extrapolation of the long tail of the done
9
FIG. 2. Blue points: Value of the theoretical spin-down limit computed for the 11 known pulsars in our analysis, corresponding
to Tab. I, error bars correspond to 1
σ
confidence level. Black triangles: median over the analysed frequency band of the
upper-limits on the GW amplitude, corresponding to Tab. IV. Red dashed line: Estimated sensitivity at 95% confidence
level of a narrow-band search using data from LIGO H. Green dashed line: Estimated sensitivity at 95% confidence level of a
narrow-band search using data from LIGO L.
consistency between the data and the estimated wave-
form [6]. For each target, if no outlier is confirmed by
the follow-up we set an upper-limit on the GW ampli-
tude and NS ellipticity, see Appendix A for more details.
IV. SELECTED TARGETS
We have selected pulsars whose spin-down limit could
possibly be beaten, or at least approached, based on the
average sensitivity of O1 data, see Fig.2. Pulsar distances
and spin-down limits are listed in Tab. I. As distance es-
timations for the pulsars we have used the best fit value
and relative uncertainties given by each indipendet mea-
sure, see pulsars list below and Tab. I for more details.
The uncertainty on the spin-down limit in Tab. I can
be computed using the relation for the variance propaga-
tion
3
.For two of these pulsars (Crab and Vela) the spin-
3
If variable
Y
is defined from
x
i
random variables with variance
σ
2
x
i
, then the variance
σ
2
Y
can be estimated as:
σ
2
Y
=
∑
i
(
∂Y
∂x
i
)
2
σ
2
x
i
down limit has been already beaten in a past narrow-
band search using Virgo VSR4 data [10]. The other tar-
gets are analysed in a narrow-band search for the first
time. The timing measures for the 11 pulsars were pro-
vided by the 76-meters Lovell telescope and the 42-foot
radio telescopes at Jodrell Bank (UK), the 26-meters tele-
scope telescope at Hartebeesthoek (South Africa), the 64-
meters Parkes radio telescope (Australia) and the Fermi
Large Area Telescope (LAT) which is a space satellite.
For 7 of these pulsars (Crab, Vela, J0205+6449, J1813-
1246, J1952+3252, J2043 +2740 and J2229+6114) up-
dated ephemerides covering O1 period were available and
a targeted search was done in a recent work [8] beating
the spin-down limit for all of them, while for the remain-
ing 4 pulsars we have used older measures extrapolating
the rotational parameters to the O1 epoch. A list of the
analysed pulsars follows:
J0205+6449
: Ephemerides obtained from Jodrell
Bank. This pulsar had a glitch on November 11th 2015
which can affect the CW search [7]. For this reason we
have performed the narrow-band search only on data be-
fore the glitch as done in [8]. The distance are set ac-
cordingly to [14].
J0534+2200 (Crab)
: One of the high value targets
for CW searches [8] due to its large spin-down value.
For this pulsar it was possible to beat the spin-down
limit in a narrow-band search using Virgo VSR4 data
[10]. Ephemerides have been obtained from Jodrell Bank