of 15
ASTROPHYSICAL IMPLICATIONS OF THE BINARY BLACK HOLE MERGER GW150914
B. P. Abbott
1
, R. Abbott
1
, T. D. Abbott
2
, M. R. Abernathy
1
, F. Acernese
3
,
4
, K. Ackley
5
, C. Adams
6
, T. Adams
7
,
P. Addesso
3
, R. X. Adhikari
1
,V.B.Adya
8
, C. Affeldt
8
, M. Agathos
9
, K. Agatsuma
9
, N. Aggarwal
10
, O. D. Aguiar
11
,
L. Aiello
12
,
13
, A. Ain
14
, P. Ajith
15
, B. Allen
8
,
16
,
17
, A. Allocca
18
,
19
, P. A. Altin
20
, S. B. Anderson
1
, W. G. Anderson
16
,
K. Arai
1
, M. C. Araya
1
, C. C. Arceneaux
21
, J. S. Areeda
22
, N. Arnaud
23
, K. G. Arun
24
, S. Ascenzi
13
,
25
, G. Ashton
26
,
M. Ast
27
, S. M. Aston
6
, P. Astone
28
, P. Aufmuth
8
, C. Aulbert
8
, S. Babak
29
,P.Bacon
30
, M. K. M. Bader
9
, P. T. Baker
31
,
F. Baldaccini
32
,
33
, G. Ballardin
34
, S. W. Ballmer
35
, J. C. Barayoga
1
, S. E. Barclay
36
, B. C. Barish
1
, D. Barker
37
,
F. Barone
3
,
4
, B. Barr
36
, L. Barsotti
10
, M. Barsuglia
30
, D. Barta
38
, J. Bartlett
37
, I. Bartos
39
, R. Bassiri
40
, A. Basti
18
,
19
,
J. C. Batch
37
, C. Baune
8
, V. Bavigadda
34
, M. Bazzan
41
,
42
, B. Behnke
29
, M. Bejger
43
, C. Belczynski
44
, A. S. Bell
36
,
C. J. Bell
36
, B. K. Berger
1
, J. Bergman
37
, G. Bergmann
8
, C. P. L. Berry
45
, D. Bersanetti
46
,
47
, A. Bertolini
9
,
J. Betzwieser
6
, S. Bhagwat
35
, R. Bhandare
48
, I. A. Bilenko
49
, G. Billingsley
1
, J. Birch
6
, R. Birney
50
, S. Biscans
10
,
A. Bisht
8
,
17
, M. Bitossi
34
, C. Biwer
35
, M. A. Bizouard
23
, J. K. Blackburn
1
, C. D. Blair
51
, D. G. Blair
51
, R. M. Blair
37
,
S. Bloemen
52
, O. Bock
8
, T. P. Bodiya
10
, M. Boer
53
, G. Bogaert
53
, C. Bogan
8
, A. Bohe
29
, P. Bojtos
54
, C. Bond
45
,
F. Bondu
55
, R. Bonnand
7
, B. A. Boom
9
, R. Bork
1
, V. Boschi
18
,
19
, S. Bose
14
,
56
, Y. Bouffanais
30
, A. Bozzi
34
,
C. Bradaschia
19
, P. R. Brady
16
, V. B. Braginsky
49
, M. Branchesi
57
,
58
, J. E. Brau
59
, T. Briant
60
, A. Brillet
53
,
M. Brinkmann
8
, V. Brisson
23
, P. Brockill
16
, A. F. Brooks
1
, D. A. Brown
35
, D. D. Brown
45
, N. M. Brown
10
,
C. C. Buchanan
2
, A. Buikema
10
, T. Bulik
44
, H. J. Bulten
9
,
61
, A. Buonanno
29
,
62
, D. Buskulic
7
, C. Buy
30
, R. L. Byer
40
,
L. Cadonati
63
, G. Cagnoli
64
,
65
, C. Cahillane
1
, J. Calder
Ó
n Bustillo
63
,
66
, T. Callister
1
, E. Calloni
4
,
67
, J. B. Camp
68
,
K. C. Cannon
69
,J.Cao
70
, C. D. Capano
8
, E. Capocasa
30
, F. Carbognani
34
, S. Caride
71
, J. Casanueva Diaz
23
,
C. Casentini
13
,
25
, S. Caudill
16
, M. Cavaglià
21
, F. Cavalier
23
, R. Cavalieri
34
, G. Cella
19
, C. Cepeda
1
,
L. Cerboni Baiardi
57
,
58
, G. Cerretani
18
,
19
, E. Cesarini
13
,
25
, R. Chakraborty
1
, T. Chalermsongsak
1
, S. J. Chamberlin
72
,
M. Chan
36
, S. Chao
73
, P. Charlton
74
, E. Chassande-Mottin
30
, H. Y. Chen
75
, Y. Chen
76
, C. Cheng
73
, A. Chincarini
47
,
A. Chiummo
34
,H.S.Cho
77
, M. Cho
62
, J. H. Chow
20
, N. Christensen
78
, Q. Chu
51
, S. Chua
60
, S. Chung
51
, G. Ciani
5
,
F. Clara
37
, J. A. Clark
63
, F. Cleva
53
, E. Coccia
12
,
13
,
25
, P.-F. Cohadon
60
, A. Colla
28
,
79
, C. G. Collette
80
, L. Cominsky
81
,
M. Constancio Jr.
11
, A. Conte
28
,
79
, L. Conti
42
, D. Cook
37
, T. R. Corbitt
2
, N. Cornish
31
, A. Corsi
82
, S. Cortese
34
,
C. A. Costa
11
, M. W. Coughlin
78
, S. B. Coughlin
83
, J.-P. Coulon
53
, S. T. Countryman
39
, P. Couvares
1
,E.E.Cowan
63
,
D. M. Coward
51
, M. J. Cowart
6
, D. C. Coyne
1
, R. Coyne
82
, K. Craig
36
, J. D. E. Creighton
16
, J. Cripe
2
, S. G. Crowder
84
,
A. Cumming
36
, L. Cunningham
36
, E. Cuoco
34
, T. Dal Canton
8
, S. L. Danilishin
36
,S.D
Antonio
13
, K. Danzmann
8
,
17
,
N. S. Darman
85
, V. Dattilo
34
,I.Dave
48
, H. P. Daveloza
86
, M. Davier
23
, G. S. Davies
36
,E.J.Daw
87
,R.Day
34
, D. DeBra
40
,
G. Debreczeni
38
, J. Degallaix
65
, M. De Laurentis
4
,
67
, S. Deléglise
60
, W. Del Pozzo
45
, T. Denker
8
,
17
, T. Dent
8
,
H. Dereli
53
, V. Dergachev
1
, R. DeRosa
6
, R. T. DeRosa
4
,
67
, R. DeSalvo
88
, S. Dhurandhar
14
, M. C. Díaz
86
, L. Di Fiore
4
,
M. Di Giovanni
28
,
79
, A. Di Lieto
18
,
19
, S. Di Pace
28
,
79
, I. Di Palma
8
,
29
, A. Di Virgilio
19
, G. Dojcinoski
89
, V. Dolique
65
,
F. Donovan
10
, K. L. Dooley
21
, S. Doravari
6
,
8
, R. Douglas
36
, T. P. Downes
16
, M. Drago
8
,
90
,
91
, R. W. P. Drever
1
,
J. C. Driggers
37
,Z.Du
70
, M. Ducrot
7
, S. E. Dwyer
37
,T.B.Edo
87
, M. C. Edwards
78
,A.Ef
fl
er
6
, H.-B. Eggenstein
8
,
P. Ehrens
1
, J. Eichholz
5
, S. S. Eikenberry
5
, W. Engels
76
, R. C. Essick
10
, T. Etzel
1
, M. Evans
10
, T. M. Evans
6
, R. Everett
72
,
M. Factourovich
39
, V. Fafone
12
,
13
,
25
, H. Fair
35
, S. Fairhurst
92
,X.Fan
70
, Q. Fang
51
, S. Farinon
47
, B. Farr
75
,W.M.Farr
45
,
M. Favata
89
,M.Fays
92
, H. Fehrmann
8
, M. M. Fejer
40
, I. Ferrante
18
,
19
, E. C. Ferreira
11
, F. Ferrini
34
, F. Fidecaro
18
,
19
,
I. Fiori
34
, D. Fiorucci
30
, R. P. Fisher
35
, R. Flaminio
65
,
93
, M. Fletcher
36
, J.-D. Fournier
53
, S. Franco
23
, S. Frasca
28
,
79
,
F. Frasconi
19
, Z. Frei
54
, A. Freise
45
, R. Frey
59
, V. Frey
23
, T. T. Fricke
8
, P. Fritschel
10
, V. V. Frolov
6
, P. Fulda
5
, M. Fyffe
6
,
H. A. G. Gabbard
21
, J. R. Gair
94
, L. Gammaitoni
32
,
33
, S. G. Gaonkar
14
, F. Garu
fi
4
,
67
, A. Gatto
30
,G.Gaur
95
,
96
,
N. Gehrels
68
, G. Gemme
47
, B. Gendre
53
, E. Genin
34
, A. Gennai
19
, J. George
48
, L. Gergely
97
, V. Germain
7
,
Archisman Ghosh
15
, S. Ghosh
9
,
52
, J. A. Giaime
2
,
6
, K. D. Giardina
6
, A. Giazotto
19
, K. Gill
98
, A. Glaefke
36
, E. Goetz
71
,
R. Goetz
5
, L. Gondan
54
, G. González
2
, J. M. Gonzalez Castro
18
,
19
, A. Gopakumar
99
, N. A. Gordon
36
,
M. L. Gorodetsky
49
, S. E. Gossan
1
, M. Gosselin
34
, R. Gouaty
7
, C. Graef
36
, P. B. Graff
62
, M. Granata
65
, A. Grant
36
,
S. Gras
10
, C. Gray
37
, G. Greco
57
,
58
, A. C. Green
45
, P. Groot
52
, H. Grote
8
, S. Grunewald
29
, G. M. Guidi
57
,
58
, X. Guo
70
,
A. Gupta
14
, M. K. Gupta
96
, K. E. Gushwa
1
, E. K. Gustafson
1
, R. Gustafson
71
, J. J. Hacker
22
, B. R. Hall
56
, E. D. Hall
1
,
G. Hammond
36
, M. Haney
99
, M. M. Hanke
8
, J. Hanks
37
, C. Hanna
72
, M. D. Hannam
92
, J. Hanson
6
, T. Hardwick
2
,
J. Harms
57
,
58
, G. M. Harry
100
, I. W. Harry
29
, M. J. Hart
36
, M. T. Hartman
5
, C.-J. Haster
45
, K. Haughian
36
, A. Heidmann
60
,
M. C. Heintze
5
,
6
, H. Heitmann
53
, P. Hello
23
, G. Hemming
34
, M. Hendry
36
, I. S. Heng
36
, J. Hennig
36
, A. W. Heptonstall
1
,
M. Heurs
8
,
17
, S. Hild
36
, D. Hoak
101
, K. A. Hodge
1
, D. Hofman
65
, S. E. Hollitt
102
, K. Holt
6
, D. E. Holz
75
, P. Hopkins
92
,
D. J. Hosken
102
, J. Hough
36
, E. A. Houston
36
, E. J. Howell
51
,Y.M.Hu
36
, S. Huang
73
, E. A. Huerta
83
,
103
, D. Huet
23
,
B. Hughey
98
, S. Husa
66
, S. H. Huttner
36
, T. Huynh-Dinh
6
, A. Idrisy
72
, N. Indik
8
, D. R. Ingram
37
, R. Inta
82
, H. N. Isa
36
,
J.-M. Isac
60
, M. Isi
1
, G. Islas
22
, T. Isogai
10
, B. R. Iyer
15
, K. Izumi
37
, T. Jacqmin
60
, H. Jang
77
, K. Jani
63
, P. Jaranowski
104
,
S. Jawahar
105
, F. Jiménez-Forteza
66
, W. W. Johnson
2
, D. I. Jones
26
, R. Jones
36
, R. J. G. Jonker
9
,L.Ju
51
, Haris K
106
,
C. V. Kalaghatgi
24
,
92
, V. Kalogera
83
, S. Kandhasamy
21
, G. Kang
77
, J. B. Kanner
1
, S. Karki
59
, M. Kasprzack
2
,
23
,
34
,
The Astrophysical Journal Letters,
818:L22
(
15pp
)
, 2016 February 20
doi:10.3847
/
2041-8205
/
818
/
2
/
L22
© 2016. The American Astronomical Society. All rights reserved.
1
E. Katsavounidis
10
, W. Katzman
6
, S. Kaufer
17
,T.Kaur
51
, K. Kawabe
37
, F. Kawazoe
8
, F. Kéfélian
53
, M. S. Kehl
69
,
D. Keitel
8
,
66
, D. B. Kelley
35
, W. Kells
1
, R. Kennedy
87
, J. S. Key
86
, A. Khalaidovski
8
, F. Y. Khalili
49
, I. Khan
12
,
S. Khan
92
, Z. Khan
96
, E. A. Khazanov
107
, N. Kijbunchoo
37
, C. Kim
77
, J. Kim
108
, K. Kim
109
, Nam-Gyu Kim
77
, Namjun Kim
40
,
Y.-M. Kim
108
, E. J. King
102
, P. J. King
37
, D. L. Kinzel
6
, J. S. Kissel
37
, L. Kleybolte
27
, S. Klimenko
5
, S. M. Koehlenbeck
8
,
K. Kokeyama
2
, S. Koley
9
, V. Kondrashov
1
, A. Kontos
10
, M. Korobko
27
, W. Z. Korth
1
, I. Kowalska
44
, D. B. Kozak
1
,
V. Kringel
8
, B. Krishnan
8
,A.Kr
Ó
lak
110
,
111
, C. Krueger
17
, G. Kuehn
8
, P. Kumar
69
,L.Kuo
73
, A. Kutynia
110
,
B. D. Lackey
35
, M. Landry
37
, J. Lange
112
, B. Lantz
40
, P. D. Lasky
113
, A. Lazzarini
1
, C. Lazzaro
42
,
63
, P. Leaci
28
,
29
,
79
,
S. Leavey
36
, E. O. Lebigot
30
,
70
, C. H. Lee
108
, H. K. Lee
109
, H. M. Lee
114
, K. Lee
36
, A. Lenon
35
, M. Leonardi
90
,
91
,
J. R. Leong
8
, N. Leroy
23
, N. Letendre
7
, Y. Levin
113
, B. M. Levine
37
,T.G.F.Li
1
, A. Libson
10
, T. B. Littenberg
115
,
N. A. Lockerbie
105
, J. Logue
36
, A. L. Lombardi
101
, J. E. Lord
35
, M. Lorenzini
12
,
13
, V. Loriette
116
, M. Lormand
6
,
G. Losurdo
58
, J. D. Lough
8
,
17
, H. Lück
8
,
17
, A. P. Lundgren
8
, J. Luo
78
, R. Lynch
10
,Y.Ma
51
, T. MacDonald
40
,
B. Machenschalk
8
, M. MacInnis
10
, D. M. Macleod
2
, F. Magaña-Sandoval
35
, R. M. Magee
56
, M. Mageswaran
1
,
E. Majorana
28
, I. Maksimovic
116
, V. Malvezzi
13
,
25
, N. Man
53
, I. Mandel
45
, V. Mandic
84
, V. Mangano
36
, G. L. Mansell
20
,
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16
, M. Mantovani
34
, F. Marchesoni
33
,
117
, F. Marion
7
, S. Márka
39
, Z. Márka
39
, A. S. Markosyan
40
, E. Maros
1
,
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57
,
58
, L. Martellini
53
, I. W. Martin
36
, R. M. Martin
5
, D. V. Martynov
1
, J. N. Marx
1
, K. Mason
10
,
A. Masserot
7
, T. J. Massinger
35
, M. Masso-Reid
36
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10
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39
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10
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56
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20
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103
, D. Meacher
72
, G. D. Meadors
8
,
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, J. Meidam
9
, A. Melatos
85
, G. Mendell
37
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8
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16
, E. Merilh
37
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1
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36
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72
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45
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65
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4
,
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10
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31
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13
, J. Ming
8
,
29
, S. Mirshekari
120
, C. Mishra
15
, S. Mitra
14
, V. P. Mitrofanov
49
,
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5
, R. Mittleman
10
, A. Moggi
19
, M. Mohan
34
, S. R. P. Mohapatra
10
, M. Montani
57
,
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, B. C. Moore
89
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121
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8
, B. Mours
7
, C. M. Mow-Lowry
45
, C. L. Mueller
5
,
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5
, A. W. Muir
92
, Arunava Mukherjee
15
, D. Mukherjee
16
, S. Mukherjee
86
, N. Mukund
14
, A. Mullavey
6
,
J. Munch
102
, D. J. Murphy
39
, P. G. Murray
36
, A. Mytidis
5
, I. Nardecchia
13
,
25
, L. Naticchioni
28
,
79
,R.K.Nayak
122
,
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5
, K. Nedkova
101
, G. Nelemans
9
,
52
, M. Neri
46
,
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, A. Neunzert
71
, G. Newton
36
, T. T. Nguyen
20
, A. B. Nielsen
8
,
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9
,
52
, A. Nitz
8
, F. Nocera
34
, D. Nolting
6
, M. E. N. Normandin
86
, L. K. Nuttall
35
, J. Oberling
37
, E. Ochsner
16
,
J. O
Dell
123
, E. Oelker
10
, G. H. Ogin
124
,J.J.Oh
125
,S.H.Oh
125
, F. Ohme
92
, M. Oliver
66
, P. Oppermann
8
, Richard J. Oram
6
,
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6
,R.O
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112
, C. D. Ott
76
, D. J. Ottaway
102
, R. S. Ottens
5
, H. Overmier
6
, B. J. Owen
82
,A.Pai
106
,
S. A. Pai
48
, J. R. Palamos
59
, O. Palashov
107
, C. Palomba
28
, A. Pal-Singh
27
,H.Pan
73
, C. Pankow
83
, F. Pannarale
92
,
B. C. Pant
48
, F. Paoletti
19
,
34
, A. Paoli
34
, M. A. Papa
8
,
16
,
29
, H. R. Paris
40
, W. Parker
6
, D. Pascucci
36
, A. Pasqualetti
34
,
R. Passaquieti
18
,
19
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19
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1
D
eceased, May 2015.
D
eceased, March 2015.
(
LIGO Scienti
fi
c Collaboration and Virgo Collaboration
)
1
LIGO, California Institute of Technology, Pasadena, CA 91125, USA
2
Louisiana State University, Baton Rouge, LA 70803, USA
3
Università 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
LIGO Livingston Observatory, Livingston, LA 70754, USA
7
Laboratoire d
Annecy-le-Vieux de Physique des Particules
(
LAPP
)
, Université Savoie Mont Blanc, CNRS
/
IN2P3, F-74941 Annecy-le-Vieux, France
8
Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-30167 Hannover, Germany
9
Nikhef, Science Park, 1098 XG Amsterdam, The Netherlands
10
LIGO, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
11
Instituto Nacional de Pesquisas Espaciais, 12227-010 São José, dos Campos, SP, Brazil
12
INFN, Gran Sasso Science Institute, I-67100 L
Aquila, Italy
13
INFN, Sezione di Roma Tor Vergata, I-00133 Roma, Italy
14
Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India
15
International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bangalore 560012, India
16
University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA
17
Leibniz Universität Hannover, D-30167 Hannover, Germany
18
Università di Pisa, I-56127 Pisa, Italy
19
INFN, Sezione di Pisa, I-56127 Pisa, Italy
20
Australian National University, Canberra, Australian Capital Territory 0200, Australia
21
The University of Mississippi, Oxford, MS 38677, USA
22
California State University Fullerton, Fullerton, CA 92831, USA
23
LAL, Univ. Paris-Sud, CNRS
/
IN2P3, Université Paris-Saclay, Orsay, France
24
Chennai Mathematical Institute, Chennai, India
25
Università di Roma Tor Vergata, I-00133 Roma, Italy
26
University of Southampton, Southampton SO17 1BJ, UK
27
Universität Hamburg, D-22761 Hamburg, Germany
28
INFN, Sezione di Roma, I-00185 Roma, Italy
29
Albert-Einstein-Institut, Max-Planck-Institut für Gravitationsphysik, D-14476 Potsdam-Golm, Germany
30
APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS
/
IN2P3, CEA
/
Irfu, Observatoire de Paris, Sorbonne Paris Cité, F-75205 Paris Cedex 13,
France
31
Montana State University, Bozeman, MT 59717, USA
32
Università di Perugia, I-06123 Perugia, Italy
33
INFN, Sezione di Perugia, I-06123 Perugia, Italy
34
European Gravitational Observatory
(
EGO
)
, I-56021 Cascina, Pisa, Italy
35
Syracuse University, Syracuse, NY 13244, USA
36
SUPA, University of Glasgow, Glasgow G12 8QQ, UK
37
LIGO Hanford Observatory, Richland, WA 99352, USA
38
Wigner RCP, RMKI, H-1121 Budapest, Konkoly Thege Miklós út 29-33, Hungary
39
Columbia University, New York, NY 10027, USA
40
Stanford University, Stanford, CA 94305, USA
41
Università di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova, Italy
42
INFN, Sezione di Padova, I-35131 Padova, Italy
43
CAMK-PAN, 00-716 Warsaw, Poland
44
Astronomical Observatory Warsaw University, 00-478 Warsaw, Poland
45
University of Birmingham, Birmingham B15 2TT, UK
46
Università degli Studi di Genova, I-16146 Genova, Italy
47
INFN, Sezione di Genova, I-16146 Genova, Italy
48
RRCAT, Indore MP 452013, India
49
Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia
50
SUPA, University of the West of Scotland, Paisley PA1 2BE, UK
51
University of Western Australia, Crawley, Western Australia 6009, Australia
52
Department of Astrophysics
/
IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
53
Artemis, Université Côte d
Azur, CNRS, Observatoire Côte d
Azur, CS F-34229, Nice cedex 4, France
54
MTA Eötvös University,
Lendulet
Astrophysics Research Group, Budapest 1117, Hungary
3
The Astrophysical Journal Letters,
818:L22
(
15pp
)
, 2016 February 20
Abbott et al.
55
Institut de Physique de Rennes, CNRS, Université de Rennes 1, F-35042 Rennes, France
56
Washington State University, Pullman, WA 99164, USA
57
Università degli Studi di Urbino
Carlo Bo,
I-61029 Urbino, Italy
58
INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Firenze, Italy
59
University of Oregon, Eugene, OR 97403, USA
60
Laboratoire Kastler Brossel, UPMC-Sorbonne Universités, CNRS, ENS-PSL Research University, Collège de France, F-75005 Paris, France
61
VU University Amsterdam, 1081 HV Amsterdam, The Netherlands
62
University of Maryland, College Park, MD 20742, USA
63
Center for Relativistic Astrophysics and School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
64
Institut Lumière Matière, Université, de Lyon, Université, Claude Bernard Lyon 1, UMR CNRS 5306, F-69622 Villeurbanne, France
65
Laboratoire des Matériaux Avancés
(
LMA
)
, IN2P3
/
CNRS, Université de Lyon, F-69622 Villeurbanne, Lyon, France
66
Universitat de les Illes Balears, IAC3
IEEC, E-07122 Palma de Mallorca, Spain
67
Università di Napoli
Federico II,
Complesso Universitario di Monte S.Angelo, I-80126 Napoli, Italy
68
NASA
/
Goddard Space Flight Center, Greenbelt, MD 20771, USA
69
Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8, Canada
70
Tsinghua University, Beijing 100084, China
71
University of Michigan, Ann Arbor, MI 48109, USA
72
The Pennsylvania State University, University Park, PA 16802, USA
73
National Tsing Hua University, Hsinchu City 30013, Taiwan ROC
74
Charles Sturt University, Wagga Wagga, New South Wales 2678, Australia
75
University of Chicago, Chicago, IL 60637, USA
76
Caltech CaRT, Pasadena, CA 91125, USA
77
Korea Institute of Science and Technology Information, Daejeon 305-806, Korea
78
Carleton College, North
fi
eld, MN 55057, USA
79
Università di Roma
La Sapienza,
I-00185 Roma, Italy
80
University of Brussels, Brussels 1050, Belgium
81
Sonoma State University, Rohnert Park, CA 94928, USA
82
Texas Tech University, Lubbock, TX 79409, USA
83
Northwestern University, Evanston, IL 60208, USA
84
University of Minnesota, Minneapolis, MN 55455, USA
85
The University of Melbourne, Parkville, Victoria 3010, Australia
86
The University of Texas Rio Grande Valley, Brownsville, TX 78520, USA
87
The University of Shef
fi
eld, Shef
fi
eld S10 2TN, UK
88
University of Sannio at Benevento, I-82100 Benevento, Italy and INFN, Sezione di Napoli, I-80100 Napoli, Italy
89
Montclair State University, Montclair, NJ 07043, USA
90
Università di Trento, Dipartimento di Fisica, I-38123 Povo, Trento, Italy
91
INFN, Trento Institute for Fundamental Physics and Applications, I-38123 Povo, Trento, Italy
92
Cardiff University, Cardiff CF24 3AA, UK
93
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
94
School of Mathematics, University of Edinburgh, Edinburgh EH9 3FD, UK
95
Indian Institute of Technology, Gandhinagar Ahmedabad Gujarat 382424, India
96
Institute for Plasma Research, Bhat, Gandhinagar 382428, India
97
University of Szeged, Dóm tér 9, Szeged 6720, Hungary
98
Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA
99
Tata Institute of Fundamental Research, Mumbai 400005, India
100
American University, Washington, DC 20016, USA
101
University of Massachusetts-Amherst, Amherst, MA 01003, USA
102
University of Adelaide, Adelaide, South Australia 5005, Australia
103
West Virginia University, Morgantown, WV 26506, USA
104
University of Bia
ł
ystok, 15-424 Bia
ł
ystok, Poland
105
SUPA, University of Strathclyde, Glasgow G1 1XQ, UK
106
IISER-TVM, CET Campus, Trivandrum Kerala 695016, India
107
Institute of Applied Physics, Nizhny Novgorod, 603950, Russia
108
Pusan National University, Busan 609-735, Korea
109
Hanyang University, Seoul 133-791, Korea
110
NCBJ, 05-400
Ś
wierk-Otwock, Poland
111
IM-PAN, 00-956 Warsaw, Poland
112
Rochester Institute of Technology, Rochester, NY 14623, USA
113
Monash University, Victoria 3800, Australia
114
Seoul National University, Seoul 151-742, Korea
115
University of Alabama in Huntsville, Huntsville, AL 35899, USA
116
ESPCI, CNRS, F-75005 Paris, France
117
Università di Camerino, Dipartimento di Fisica, I-62032 Camerino, Italy
118
Southern University and A&M College, Baton Rouge, LA 70813, USA
119
College of William and Mary, Williamsburg, VA 23187, USA
120
Instituto de Física Teórica, University Estadual Paulista
/
ICTP South American Institute for Fundamental Research, São Paulo SP 01140-070, Brazil
121
University of Cambridge, Cambridge CB2 1TN, UK
122
IISER-Kolkata, Mohanpur, West Bengal 741252, India
123
Rutherford Appleton Laboratory, HSIC, Chilton, Didcot, Oxon OX11 0QX, UK
124
Whitman College, 345 Boyer Ave, Walla Walla, WA 99362 USA
125
National Institute for Mathematical Sciences, Daejeon 305-390, Korea
126
Hobart and William Smith Colleges, Geneva, NY 14456, USA
127
Institute of Astronomy, 65-265 Zielona Góra, Poland
128
Andrews University, Berrien Springs, MI 49104, USA
129
Università di Siena, I-53100 Siena, Italy
130
Trinity University, San Antonio, TX 78212, USA
4
The Astrophysical Journal Letters,
818:L22
(
15pp
)
, 2016 February 20
Abbott et al.
131
University of Washington, Seattle, WA 98195, USA
132
Kenyon College, Gambier, OH 43022, USA
133
Abilene Christian University, Abilene, TX 79699, USA
Received 2016 January 29; accepted 2016 February 3; published 2016 February 11
ABSTRACT
The discovery of the gravitational-wave
(
GW
)
source GW150914 with the Advanced LIGO detectors provides the
fi
rst observational evidence for the existence of binary black hole
(
BH
)
systems that inspiral and merge within the
age of the universe. Such BH mergers have been predicted in two main types of formation models, involving
isolated binaries in galactic
fi
elds or dynamical interactions in young and old dense stellar environments. The
measured masses robustly demonstrate that relatively
heavy
BHs
(
25
M
)
can form in nature. This discovery
implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with a
metallicity lower than about 1
/
2 of the solar value. The rate of binary-BH
(
BBH
)
mergers inferred from the
observation of GW150914 is consistent with the higher end of rate predictions
(
1
Gpc
3
yr
1
)
from both types of
formation models. The low measured redshift
(
z
0.
1
)
of GW150914 and the low inferred metallicity of the
stellar progenitor imply either BBH formation in a low-mass galaxy in the local universe and a prompt merger, or
formation at high redshift with a time delay between formation and merger of several Gyr. This discovery
motivates further studies of binary-BH formation astrophysics. It also has implications for future detections and
studies by Advanced LIGO and Advanced Virgo, and GW detectors in space.
Key words:
gravitational waves
stars: black holes
stars: massive
1. INTRODUCTION
When in the 1970s the mass of the compact object in the X-ray
binary
(
XRB
)
Cygnus X-1 was measured to exceed the maximum
mass of a neutron star
(
Webster & Murdin
1972
;Bolton
1972
)
,
black holes
(
BHs
)
turned from a theoretical concept into an
observational reality. Around the same time and over several years,
evidence for supermassive BHs in the centers of galaxies mounted
(
see Kormendy & Richstone
1995
)
. The formation of the stellar-
mass BHs found in XRBs is assoc
iated with the core collapse
(
and
potential supernova
[
SN
]
explosion
)
of massive stars when they
have exhausted their nuclear fuel
(
e.g., Heger et al.
2003
)
.The
origin of supermassive BHs is less clear. They may have small
seeds that originate from
heavy
stellar-mass BHs
(
more massive
than about 25
M
)
or large seeds from intermediate-mass BHs
formed in the earliest generations of massive stars or directly from
large clouds
(
see Volonteri
2010
)
.
The gravitational-wave
(
GW
)
signal GW150914 detected on
2015 September 14 09:50:45 UTC by the Advanced LIGO
(
aLIGO
)
detectors
(
Abbott et al.
2016a
, hereafter LVC16a;
henceforth we refer similarly to all other forthcoming
papers from the LIGO-Virgo Collaborations and related to
GW150914
)
has been shown to originate from the coalescence
of a binary BH
(
BBH
)
with masses of
3
6
4
5
-
+
M
and
2
9
4
4
-
+
M
(
in
the source frame, see Section
2
)
. This GW discovery provides
the
fi
rst robust con
fi
rmation of several theoretical predictions:
(
i
)
that
heavy
BHs exist,
(
ii
)
that BBHs form in nature, and
(
iii
)
that BBHs merge within the age of the universe at a
detectable rate.
The inspiral and merger of binaries with BHs or neutron stars
(
NSs
)
have been discussed as the primary source for ground-
based GW interferometers for many decades
(
e.g., Thorne
1987
;
Schutz
1989
)
. The existence of GWs was established with radio
observations of the orbital decay of the
fi
rst binary pulsar, PSR
B1913
+
16
(
Hulse & Taylor
1975
; Taylor & Weisberg
1982
)
.
Even before the binary pulsar discovery, Tutukov & Yungelson
(
1973
)
described the evolution of isolated massive binaries
(
i.e.,
those not in
fl
uenced dynamically by surrounding stars
)
and
predicted the formation of binary compact objects, including
BBHs. Some of the
fi
rst
population
studies of massive stellar
binaries and their evolution even predicted that BBH mergers
could dominate detection rates for ground-based GW interfero-
metric detectors
(
Lipunov et al.
1997
)
. Furthermore, Sigurdsson
&Hernquist
(
1993
)
recognized that dense star clusters provide
another possible way of forming merging BBHs: BHs in dense
star clusters quickly become the most massive objects, sink
toward the cluster core, subsequently form pairs through
dynamical interactions, and are most commonly ejected in binary
con
fi
gurations with inspiral times shorter than the age of the
universe. For the most recent review articles on the formation of
binary compact objects in galactic
fi
elds and dense stellar
systems, see Postnov & Yungelson
(
2014
)
and Benacquista &
Downing
(
2013
)
, respectively.
In this paper we discuss GW150914 in the context of
astrophysical predictions in the
literature and we identify the most
robust constraints on BBH fo
rmation models. In Section
2
we
report the properties of GW150914. In Section
3
and Section
4
we
discuss the implications of the measured BH masses and distance to
the source. In Section
5
and Section
6
we examine conclusions that
can be drawn from the GW constraint
s on the orbital eccentricity,
BH spins, and BBH merger rates. In Section
7
we discuss prospects
for future detections and the types of astrophysical studies we
would need to further advance our understanding of BBH
formation. In Section
8
we summarize our key conclusions.
2. THE PROPERTIES OF GW150914
GW150914 was discovered
fi
rst through a low-latency search
for GW transients, and later in subsequent match-
fi
lter analyses of
16 days of coincident data collected by the two aLIGO detectors
between September 12 and October 20
(
LVC16a
)
. The signal
matches the waveform expected for the inspiral, merger, and
ringdown from a compact binary. In 0.2 s it swept in frequency
from35to250Hz,reachingapeakGWstrainof1.0
×
10
21
with a signal-to-noise ratio of 24
(
LVC16b
,
LVC16c
)
.
Consideration of these basic signal properties of frequency
and frequency derivative indicate that the source is a BH
merger
(
LVC16a
)
. Coherent Bayesian analyses
(
LVC16d
)
using advanced waveforms
(
Hannam et al.
2014
; Pürrer
2014
; Taracchini et al.
2014
; Khan et al.
2015
)
allow us to
5
The Astrophysical Journal Letters,
818:L22
(
15pp
)
, 2016 February 20
Abbott et al.
measure several of the source physical parameters
(
all quoted at
90% credible level
)
. In the detector frame, the chirp mass
1
is
3
0
2
2
-
+
M
and the total mass is
7
1
4
5
-
+
M
; the mass ratio is
0
.82
0.21
0.16
-
+
and the luminosity distance is determined to be
4
10
180
160
-
+
Mpc
(
redshift
0
.09
0.04
0.03
-
+
)
. The two BH masses in the
source frame then are
3
6
4
5
-
+
M
and
2
9
4
4
-
+
M
, and the chirp
mass in the source frame is
2
8
2
2
-
+
M
. The source-frame mass
and spin of the
fi
nal BH are
62
4
4
-
+
M
and
0
.67
0.07
0.0
5
-
+
and the
source is localized to a sky area of 600 deg
2
(
see also
LVC16d
;
LVC16h
)
. The signal does not show deviations from the
expectations of general relativity, as discussed in detail in
LVC16e
.
Assuming that the source-frame BBH merger rate is constant
within the volume in which GW150914 could have been
detected
(
found to extend out to redshift of
;
0.5
)
and that
GW150914 is representative of the underlying BBH popula-
tion, the BBH merger rate is inferred to be 2
53 Gpc
3
yr
1
in
the comoving frame at the 90% credible level
(
Kim et al.
2003
;
LVC16f
)
. The match-
fi
lter searches of these 16 days of
coincident data also revealed a number of sub-threshold
triggers with associated probabilities of being astrophysical or
noise in nature
(
LVC16b
)
. If we account for the probability
of these sub-threshold triggers and we consider a wide range
of models for the underlying BBH mass distribution, the
estimated BBH merger rates extend to the range 2
400 Gpc
3
yr
1
(
Farr et al.
2015
;
LVC16f
)
.
3. BH MASSES IN MERGING BINARIES
3.1. Brief Review of Measured BH Masses
Prior to the discovery of GW150914, our knowledge of
stellar BH masses has come from the study of XRBs where a
compact object accretes matter from a stellar companion
(
e.g.,
McClintock & Remillard
2006
)
. Dynamical compact-object
mass measurements in these binaries rely on measurements of
the system
ʼ
s orbital period, the amplitude of the stellar-
companion
ʼ
s radial velocity curve, and quantitative constraints
on the binary inclination and the companion mass
(
e.g., Casares
& Jonker
2014
)
. When the mass of the compact object is found
to exceed 3
M
, which is the conservative upper limit for stable
NSs
(
Rhoades & Ruf
fi
ni
1974
; Kalogera & Baym
1996
)
, then
the XRB is considered to host a BH. At present, 22 BH XRBs
have con
fi
rmed dynamical mass measurements, 19 of which lie
in our Galaxy. For the majority of the systems, the measured
BH masses are 5
10
M
, while some have masses of
10
20
M
.
2
BH masses have been claimed to be measured
dynamically in two other extragalactic systems, IC10 X-1
(
Prestwich et al.
2007
; Silverman & Filippenko
2008
,
M
BH
=
21
35
M
)
and NGC300 X-1
(
Crowther et al.
2010
,
M
BH
=
12
24
M
)
. On the basis of these observations, Bulik et al.
(
2011
)
argue that these two systems are likely immediate
progenitors of BBH systems. However, recent work casts doubt
on these BH masses: it now appears more likely that the
measured velocities are due to stellar-wind features instead of
the BH companion
ʼ
s orbital motion
(
Laycock et al.
2015
, and
references therein
)
, and therefore we do not consider the
claimed BH masses in these systems as reliable.
All of these observed BH systems are found in low stellar
density galactic
fi
elds. Based on multi-wavelength electromagnetic
studies of X-ray point sources
,BHXRBshavealsobeenclaimed
to exist in globular clusters
(
Maccarone et al.
2007
; Chomiuk et al.
2013
, and references therein
)
; however, dynamical mass measure-
ments for these systems have not been possible, and hence reliable
BH mass constraints are not available.
Both BHs of the GW150914 coalescence are more massive
than the BHs in known XRBs with reliably measured masses:
this GW discovery provides the most robust evidence for the
existence of
heavy
(
25
M
)
stellar-mass BHs.
In what
follows, we review our current understanding of BH and BBH
formation both in isolation and in dense environments, and we
examine the implications of the high GW150914 BH masses.
3.2. Predicted Masses for Single BHs
BHs are expected to form at the end of the nuclear lifetimes
of massive stars. The stellar core collapses to form a proto-NS
and the occurrence and strength of an SN explosion determines
how much material is ejected, and whether a BH is formed.
Fryer & Kalogera
(
2001
)
distinguish BH formation through
partial or full fallback of the initially exploding envelope, or
through the complete collapse of the BH progenitor due to a
core collapse that is not powerful enough to drive an explosion.
Fryer et al.
(
2012
)
fi
nd that the transition from NS to BH
formation occurs at initial progenitor masses of
;
18
20
M
and the transition from fallback to complete BH
collapse takes place at initial progenitor masses of
;
40
M
.
Other studies
(
e.g., Ugliano et al.
2012
)
fi
nd that either the SN
is successful and an NS is formed, or the whole star collapses to
a BH; there is a range of progenitor masses
(
15
40
M
for solar
metallicity
)
where either an NS or a BH could form.
This relatively simple picture of BH formation from single
stars is greatly affected by several key factors: the strength of
massive-star winds and their dependence on the star
ʼ
s
metallicity
(
Z
, e.g., Maeder
1992
)
, stellar rotation
(
e.g., de
Mink et al.
2009
)
, and the microphysics of stellar evolution.
These factors affect the relationship between the initial
progenitor mass and the stellar
(
core
)
mass at the time of
collapse, and thus the mass of the resulting BH.
Winds are understood to be radiation-driven. Their strengths
depend on stellar properties, but cannot be derived from
fi
rst
principles; instead they are empirically derived and calibrated based
on observations
(
for a review, see Smith
2014
)
.Overthelast
decades, wind strengths for different evolutionary stages have been
signi
fi
cantly revised, mainly downwards, leading to more massive
progenitors at core collapse
(
for a review, see Vink
2008
)
.In
general, stars at
lower metallicities exhibit weaker winds, since the
lower metal content reduces opacity, enables easier radiation
transport, and reduces radiation momentum transfer and hence mass
loss from the stellar surface. Th
e functional dependence on
metallicity is also empirically constrained by studying massive stars
in environments of different metallicities. However, the range in
metallicities probed by observati
ons is much smaller than the range
where massive stars are formed
over cosmic history, and hence
extrapolations to meta
llicities orders of magnitude smaller than
solar
Z
(
i.e.,
Z
0.0
2
=
)
are adopted. Although we have no way
of validating such extrapolations, here we consider the published
low-metallicity models.
Heger et al.
(
2003
)
and Mapelli et al.
(
2009
)
were among the
fi
rst to examine how compact object formation depends on
progenitor masses, stellar winds
, and metallicity, albeit in a rather
1
The chirp mass is
mm
m m
12
35
12
15
()()
=+
, where
m
1
and
m
2
are the
component masses.
2
For probability distribution functions of measured BH masses see
Farr et al.
(
2011
)
and Özel et al.
(
2010
)
.
6
The Astrophysical Journal Letters,
818:L22
(
15pp
)
, 2016 February 20
Abbott et al.