# Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during their First and Second Observing Runs

B.P. Abbott, R. Abbott, T.D. Abbott, S. Abraham, F. Acernese, K. Ackley, C. Adams, R.X. Adhikari, V.B. Adya, C. Affeldt, et al.

► To cite this version:

B.P. Abbott, R. Abbott, T.D. Abbott, S. Abraham, F. Acernese, et al., Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during their First and Second Observing Runs. Astrophys.J., 2019, 883 (2), pp.149. 10.3847/1538-4357/ab3c2d. hal-02999728

HAL Id: hal-02999728

https://hal.science/hal-02999728

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Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced
Virgo during Their First and Second Observing Runs

B. P. Abbott¹, R. Abbott¹, T. D. Abbott², S. Abraham³, F. Acernese⁴,⁵, K. Ackley⁶, C. Adams⁷, R. X. Adhikari¹, V. B. Adya⁸,

C. Affeldt⁹,¹⁰, M. Agathos¹¹,¹², K. Agatsuma¹³, N. Aggarwal¹⁴, O. D. Aguiar¹⁵, L. Aiello¹⁶,¹⁷, A. Ain³, P. Ajith¹⁸, G. Allen¹⁹,
A. Allocca²⁰,²¹, M. A. Aloy²², P. A. Altin⁸, A. Amato²³, S. Anand¹, A. Ananyeva¹, S. B. Anderson¹, W. G. Anderson²⁴,

S. V. Angelova²⁵, S. Antier²⁶, S. Appert¹, K. Arai¹, M. C. Araya¹, J. S. Areeda²⁷, M. Arène²⁶, N. Arnaud²⁸,²⁹, S. M. Aronson³⁰,

K. G. Arun³¹, S. Ascenzi¹⁶,³², G. Ashton⁶, S. M. Aston⁷, P. Astone³³, F. Aubin³⁴, P. Aufmuth¹⁰, K. AultONeal³⁵, C. Austin²,

V. Avendano³⁶, A. Avila-Alvarez²⁷, S. Babak²⁶, P. Bacon²⁶, F. Badaracco¹⁶,¹⁷, M. K. M. Bader³⁷, S. Bae³⁸, J. Baird²⁶,

P. T. Baker³⁹, F. Baldaccini⁴⁰,⁴¹, G. Ballardin²⁹, S. W. Ballmer⁴², A. Bals³⁵, S. Banagiri⁴³, J. C. Barayoga¹, C. Barbieri⁴⁴,⁴⁵,

S. E. Barclay⁴⁶, B. C. Barish¹, D. Barker⁴⁷, K. Barkett⁴⁸, S. Barnum¹⁴, F. Barone⁵,⁴⁹, B. Barr⁴⁶, L. Barsotti¹⁴, M. Barsuglia²⁶,

D. Barta⁵⁰, J. Bartlett⁴⁷, I. Bartos³⁰, R. Bassiri⁵¹, A. Basti²⁰,²¹, M. Bawaj⁴¹,⁵², J. C. Bayley⁴⁶, M. Bazzan⁵³,⁵⁴, B. Bécsy⁵⁵,

M. Bejger²⁶,⁵⁶, I. Belahcene²⁸, A. S. Bell⁴⁶, D. Beniwal⁵⁷, M. G. Benjamin³⁵, G. Bergmann⁹,¹⁰, S. Bernuzzi¹¹, C. P. L. Berry⁵⁸,

D. Bersanetti⁵⁹, A. Bertolini³⁷, J. Betzwieser⁷, R. Bhandare⁶⁰, J. Bidler²⁷, E. Biggs²⁴, I. A. Bilenko⁶¹, S. A. Bilgili³⁹, G. Billingsley¹,

R. Birney²⁵, O. Birnholtz⁶², S. Biscans¹,¹⁴, M. Bischi⁶³,⁶⁴, S. Biscoveanu¹⁴, A. Bisht¹⁰, M. Bitossi²¹,²⁹, M. A. Bizouard⁶⁵,

J. K. Blackburn¹, J. Blackman⁴⁸, C. D. Blair⁷, D. G. Blair⁶⁶, R. M. Blair⁴⁷, S. Bloemen⁶⁷, F. Bobba⁶⁸,⁶⁹, N. Bode⁹,¹⁰, M. Boer⁶⁵,

Y. Boetzel⁷⁰, G. Bogaert⁶⁵, F. Bondu⁷¹, R. Bonnand³⁴, P. Booker⁹,¹⁰, B. A. Boom³⁷, R. Bork¹, V. Boschi²⁹, S. Bose³,

V. Bossilkov⁶⁶, J. Bosveld⁶⁶, Y. Bouffanais⁵³,⁵⁴, A. Bozzi²⁹, C. Bradaschia²¹, P. R. Brady²⁴, A. Bramley⁷, M. Branchesi¹⁶,¹⁷,

J. E. Brau⁷², M. Breschi¹¹, T. Briant⁷³, J. H. Briggs⁴⁶, F. Brighenti⁶³,⁶⁴, A. Brillet⁶⁵, M. Brinkmann⁹,¹⁰, P. Brockill²⁴, A. F. Brooks¹,

J. Brooks²⁹, D. D. Brown⁵⁷, S. Brunett¹, A. Buikema¹⁴, T. Bulik⁷⁴, H. J. Bulten³⁷,⁷⁵, A. Buonanno⁷⁶,⁷⁷, D. Buskulic³⁴, C. Buy²⁶,

R. L. Byer⁵¹, M. Cabero⁹,¹⁰, L. Cadonati⁷⁸, G. Cagnoli⁷⁹, C. Cahillane¹, J. Calderón Bustillo⁶, T. A. Callister¹, E. Calloni⁵,⁸⁰,

J. B. Camp⁸¹, W. A. Campbell⁶, M. Canepa⁵⁹,⁸², K. C. Cannon⁸³, H. Cao⁵⁷, J. Cao⁸⁴, G. Carapella⁶⁸,⁶⁹, F. Carbognani²⁹,

S. Caride⁸⁵, M. F. Carney⁵⁸, G. Carullo²⁰,²¹, J. Casanueva Diaz²¹, C. Casentini³²,⁸⁶, S. Caudill³⁷, M. Cavaglià⁸⁷,⁸⁸, F. Cavalier²⁸,

R. Cavalieri²⁹, G. Cella²¹, P. Cerdá-Duràr²², E. Cesarini³²,⁸⁹, O. Chaibi⁶⁵, K. Chakravarti³, S. J. Chamberlin⁹⁰, M. Chan⁴⁶,

S. Chao⁹¹, P. Charlton⁹², E. A. Chase⁵⁸, E. Chassande-Mottin²⁶, D. Chatterjee²⁴, M. Chaturvedi⁶⁰, B. D. Cheeseboro³⁹,

H. Y. Chen⁹³, X. Chen⁶⁶, Y. Chen⁴⁸, H.-P. Cheng³⁰, C. K. Cheong⁹⁴, H. Y. Chia³⁰, F. Chiadini⁹⁹,⁹⁵, A. Chincarini⁵⁹,

A. Chiummo²⁹, G. Cho⁹⁶, H. S. Cho⁹⁷, M. Cho⁷⁷, N. Christensen⁶⁵,⁹⁸, Q. Chu⁶⁶, S. Chua⁷³, K. W. Chung⁹⁴, S. Chung⁶⁶,

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F. Cleva⁶⁵, E. Coccia¹⁶,¹⁷, P.-F. Cohadon⁷³, D. Cohen²⁸, M. Colleoni¹⁰¹, C. G. Collette¹⁰², C. Collins¹³, M. Colpi⁴⁴,⁴⁵,

L. R. Cominsky¹⁰³, M. Constancio Jr.¹⁵, L. Conti⁵⁴, S. J. Cooper¹³, P. Corban⁷, T. R. Corbitt², I. Cordero-Carrión¹⁰⁴,

S. Corezzi⁴⁰,⁴¹, K. R. Corley¹⁰⁵, N. Cornish⁵⁵, D. Corre²⁸, A. Corsi⁸⁵, S. Cortese²⁹, C. A. Costa¹⁵, R. Cotesta⁷⁶, M. W. Coughlin¹,

S. B. Coughlin⁵⁸,¹⁰⁶, J.-P. Coulon⁶⁵, S. T. Countryman¹⁰⁵, P. Couvares¹, P. B. Covas¹⁰¹, E. E. Cowan⁷⁸, D. M. Coward⁶⁶,

M. J. Cowart¹, D. C. Coyne¹, R. Coyne¹⁰⁷, J. D. E. Creighton²⁴, T. D. Creighton¹⁰⁸, J. Cripe², M. Croquette⁷³, S. G. Crowder¹⁰⁹,

T. J. Cullen², A. Cumming⁴⁶, L. Cunningham⁴⁶, E. Cuoco²⁹, T. Dal Canton⁸¹, G. Dálya¹¹⁰, B. D'Angelo⁵⁹,⁸², S. L. Danilishin⁹,¹⁰,

S. D'Antonio³², K. Danzmann⁹,¹⁰, A. Dasgupta¹¹¹, C. F. Da Silva Costa³⁰, L. E. H. Datrier⁴⁶, V. Dattilo²⁹, I. Dave⁶⁰, M. Davier²⁸,

D. Davis⁴², E. J. Daw¹¹², D. DeBra⁵¹, M. Deenadayalan³, J. Degallaix²³, M. De Laurentis⁵,⁸⁰, S. Deléglise⁷³, W. Del Pozzo²⁰,²¹,

L. M. DeMarchi⁵⁸, N. Demos¹⁴, T. Dent¹¹³, R. De Pietri¹¹⁴,¹¹⁵, R. De Rosa⁵,⁸⁰, C. De Rossi²³,²⁹, R. DeSalvo¹¹⁶, O. de Varona⁹,¹⁰,

S. Dhurandhar³, M. C. Díaz¹⁰⁸, T. Dietrich³⁷, L. Di Fiore⁵, C. DiFronzo¹³, C. Di Giorgio⁶⁸,⁶⁹, F. Di Giovanni²²,

M. Di Giovanni¹¹⁷,¹¹⁸, T. Di Girolamo⁵,⁸⁰, A. Di Lieto²⁰,²¹, B. Ding¹⁰², S. Di Pace³³,¹¹⁹, I. Di Palma³³,¹¹⁹, F. Di Renzo²⁰,²¹,

A. K. Divakarla³⁰, A. Dmitriev¹³, Z. Doctor⁹³, F. Donovan¹⁴, K. L. Dooley⁸⁷,¹⁰⁶, S. Doravari³, I. Dorrington¹⁰⁶, T. P. Downes²⁴,

M. Drago¹⁶,¹⁷, J. C. Driggers⁴⁷, Z. Du⁸⁴, J.-G. Ducoin²⁸, P. Dupej⁴⁶, O. Durante⁶⁸,⁶⁹, S. E. Dwyer⁴⁷, P. J. Easter⁶, G. Eddolls⁴⁶,

T. B. Edo¹¹², A. Effler⁷, P. Ehrens¹, J. Eichholz⁸, S. S. Eikenberry³⁰, M. Eisenmann³⁴, R. A. Eisenstein¹⁴, L. Errico⁵,⁸⁰,

R. C. Essick⁹³, H. Estelles¹⁰¹, D. Estevez³⁴, Z. B. Etienne³⁹, T. Etzel¹, M. Evans¹⁴, T. M. Evans⁷, V. Fafone¹⁶,³²,⁸⁶ S. Fairhurst¹⁰⁶,

X. Fan⁸⁴, S. Farinon⁵⁹, B. Farr⁷², W. M. Farr¹³, E. J. Fauchon-Jones¹⁰⁶, M. Favata³⁶, M. Fays¹¹², M. Fazio¹²⁰, C. Fee¹²¹, J. Feicht¹,

M. M. Fejer⁵¹, F. Feng²⁶, A. Fernandez-Galiana¹⁴, I. Ferrante²⁰,²¹, E. C. Ferreira¹⁵, T. A. Ferreira¹⁵, F. Fidecaro²⁰,²¹, I. Fiori²⁹,

D. Fiorucci¹⁶,¹⁷, M. Fishbach⁹³, R. P. Fisher¹²², J. M. Fishner¹⁴, R. Fittipaldi⁶⁹,¹²³, M. Fitz-Axen⁴³, V. Fiumara⁶⁹,¹²⁴,

R. Flaminio³⁴,¹²⁵, M. Fletcher⁴⁶, E. Floden⁴³, E. Flynn²⁷, H. Fong⁸³, J. A. Font²²,¹²⁶, P. W. F. Forsyth⁸, J.-D. Fournier⁶⁵,

Francisco Hernandez Vivanco⁶, S. Frasca³³,¹¹⁹, F. Frasconi²¹, Z. Frei¹¹⁰, A. Freise¹³, R. Frey⁷², V. Frey²⁸, P. Fritschel¹⁴,

V. V. Frolov⁷, G. Fronzè¹²⁷, P. Fulda³⁰, M. Fyffe⁷, H. A. Gabbard⁴⁶, B. U. Gadre⁷⁶, S. M. Gaebel¹³, J. R. Gair¹²⁸, L. Gammaitoni⁴⁰,

S. G. Gaonkar³, C. García-Quirós¹⁰¹, F. Garufi⁵,⁸⁰, B. Gateley⁴⁷, S. Gaudio³⁵, G. Gaur¹²⁹, V. Gayathri¹³⁰, G. Gemme⁵⁹, E. Genin²⁹,

A. Gennai²¹, D. George¹⁹, J. George⁶⁰, L. Gergely¹³¹, S. Ghonge⁷⁸, Abhirup Ghosh⁷⁶, Archisman Ghosh³⁷, S. Ghosh²⁴,

B. Giacomazzo¹¹⁷,¹¹⁸, J. A. Giaime²,⁷, K. D. Giardina⁷, D. R. Gibson¹³², K. Gill¹⁵⁰, L. Glover¹³³, J. Gniesmer¹³⁴, P. Godwin⁹⁰,

E. Goetz⁴⁷, R. Goetz³⁰, B. Goncharov⁶, G. González², J. M. Gonzalez Castro²⁰,²¹, A. Gopakumar¹³⁵, S. E. Gossan¹,

M. Gosselin²⁰,²¹,²⁹, R. Gouaty³⁴, B. Grace⁸, A. Grado⁵,¹³⁶, M. Granata²³, A. Grant⁴⁶, S. Gras¹⁴, P. Grassia¹, C. Gray⁴⁷, R. Gray⁴⁶,

G. Greco⁶³,⁶⁴, A. C. Green³⁰, R. Green¹⁰⁶, E. M. Gretarsson³⁵, A. Grimaldi¹¹⁷,¹¹⁸, S. J. Grimm¹⁶,¹⁷, P. Groot⁶⁷, H. Grote¹⁰⁶,
S. Grunewald<sup>76</sup>, P. Gruning<sup>28</sup>, G. M. Guidi<sup>63,64</sup>, H. K. Gulati<sup>111</sup>, Y. Guo<sup>37</sup>, A. Gupta<sup>90</sup>, Anchal Gupta<sup>1</sup>, P. Gupta<sup>37</sup>, E. K. Gustafson<sup>1</sup>, R. Gustafson<sup>157</sup>, L. Haegel<sup>101</sup>, O. Halim<sup>16,17</sup>, B. R. Hall<sup>138</sup>, E. D. Hall<sup>14</sup>, E. Z. Hamilton<sup>106</sup>, G. Hammond<sup>46</sup>, M. Haney<sup>70</sup>, M. M. Hanke<sup>9,10</sup>, J. Hanks<sup>47</sup>, C. Hanna<sup>90</sup>, M. D. Hannam<sup>106</sup>, O. A. Hannuksela<sup>94</sup>, T. J. Hansen<sup>35</sup>, J. Hanson<sup>7</sup>, T. Harder<sup>65</sup>, T. Hardwick<sup>2</sup>, K. Haris<sup>18</sup>, J. Harms<sup>16,17</sup>, G. M. Harry<sup>139</sup>, I. W. Harry<sup>140</sup>, R. K. Hasskew<sup>7</sup>, C. J. Haster<sup>14</sup>, K. Haughian<sup>46</sup>, F. J. Hayes<sup>46</sup>, J. Healy<sup>62</sup>, A. Heidmann<sup>73</sup>, M. C. Heintze<sup>7</sup>, H. Heitmann<sup>65</sup>, F. Hellman<sup>141</sup>, P. Hello<sup>28</sup>, G. Hemming<sup>29</sup>, M. Hendry<sup>46</sup>, I. S. Heng<sup>46</sup>, J. Hennig<sup>9,10</sup>, M. Heurs<sup>9,10</sup>, S. Hild<sup>46</sup>, T. Hinderer<sup>37,142,143</sup>, S. Hochheim<sup>9,10</sup>, D. Hofman<sup>23</sup>, A. M. Holgado<sup>19</sup>, N. A. Holland<sup>8</sup>, K. Holt<sup>7</sup>, D. E. Holz<sup>93</sup>, P. Hopkins<sup>106</sup>, C. Horst<sup>24</sup>, J. Hough<sup>46</sup>, E. J. Howell<sup>66</sup>, C. G. Hoy<sup>106</sup>, Y. Huang<sup>14</sup>, M. T. Hübner<sup>6</sup>, E. A. Huerta<sup>19</sup>, D. Huet<sup>28</sup>, B. Hughey<sup>35</sup>, V. Hui<sup>34</sup>, S. Husa<sup>101</sup>, S. H. Huttner<sup>46</sup>, T. Huynh-Dinh<sup>7</sup>, B. Idzkowski<sup>74</sup>, A. Iess<sup>32,86</sup>, H. Inchauspe<sup>30</sup>, C. Ingram<sup>57</sup>, R. Inta<sup>85</sup>, G. Intini<sup>33,119</sup>, B. Irwin<sup>121</sup>, H. N. Isa<sup>46</sup>, J.-M. Isac<sup>73</sup>, M. Isi<sup>14</sup>, B. R. Iyer<sup>18</sup>, T. Jacqmin<sup>73</sup>, S. J. Jadhav<sup>144</sup>, K. Jani<sup>78</sup>, N. N. Janthalur<sup>144</sup>, P. Jaranowski<sup>145</sup>, D. Jariwala<sup>30</sup>, A. C. Jenkins<sup>146</sup>, J. Jiang<sup>30</sup>, D. S. Johnson<sup>19</sup>, A. W. Jones<sup>13</sup>, D. I. Jones<sup>147</sup>, J. D. Jones<sup>47</sup>, R. Jones<sup>46</sup>, R. J. G. Jonker<sup>37</sup>, L. Ju<sup>66</sup>, J. Junker<sup>9,10</sup>, C. V. Kalaghatgi<sup>106</sup>, V. Kalogera<sup>58</sup>, B. Kamai<sup>1</sup>, S. Kandhasamy<sup>3</sup>, G. Kang<sup>38</sup>, J. B. Kanner<sup>1</sup>, S. J. Kapadia<sup>24</sup>, S. Karki<sup>72</sup>, R. Kashyap<sup>18</sup>, M. Kasprzack<sup>1</sup>, S. Katsanevas<sup>29</sup>, E. Katsavounidis<sup>14</sup>, W. Katzman<sup>7</sup>, S. Kaufer<sup>10</sup>, K. Kawabe<sup>47</sup>, N. V. Keerthana<sup>3</sup>, F. Kéfélian<sup>65</sup>, D. Keitel<sup>140</sup>, R. Kennedy<sup>112</sup>, J. S. Key<sup>148</sup>, F. Y. Khalili<sup>61</sup>, I. Khan<sup>16,32</sup>, S. Khan<sup>9,10</sup>, E. A. Khazanov<sup>149</sup>, N. Khetan<sup>16,17</sup>, M. Khursheed<sup>60</sup>, N. Kijbunchoo<sup>8</sup>, Chunglee Kim<sup>150</sup>, J. C. Kim<sup>151</sup>, K. Kim<sup>94</sup>, W. Kim<sup>57</sup>, W. S. Kim<sup>152</sup>, Y.-M. Kim<sup>153</sup>, C. Kimball<sup>58</sup>, P. J. King<sup>47</sup>, M. Kinley-Hanlon<sup>46</sup>, R. Kirchhoff<sup>9,10</sup>, J. S. Kissel<sup>47</sup>, L. Kleybolte<sup>134</sup>, J. H. Klika<sup>24</sup>, S. Klimenko<sup>30</sup>, T. D. Knowles<sup>39</sup>, P. Koch<sup>9,10</sup>, S. M. Koehlenbeck<sup>9,10</sup>, G. Koekoek<sup>37,154</sup>, S. Koley<sup>37</sup>, V. Kondrashov<sup>1</sup>, A. Kontos<sup>155</sup>, N. Koper<sup>9,10</sup>, M. Korobko<sup>134</sup>, W. Z. Korth<sup>1</sup>, M. Kovalam<sup>66</sup>, D. B. Kozak<sup>1</sup>, C. Krämer<sup>9,10</sup>, V. Kringel<sup>9,10</sup>, N. Krishnendu<sup>31</sup>, A. Królak<sup>156,157</sup>, N. Krupinski<sup>24</sup>, G. Kuehn<sup>9,10</sup>, A. Kumar<sup>144</sup>, P. Kumar<sup>158</sup>, Rahul Kumar<sup>47</sup>, Rakesh Kumar<sup>111</sup>, L. Kuo<sup>91</sup>, A. Kutynia<sup>156</sup>, S. Kwang<sup>24</sup>, B. D. Lackey<sup>76</sup>, D. Laghi<sup>20,21</sup>, K. H. Lai<sup>94</sup>, T. L. Lam<sup>94</sup>, M. Landry<sup>47</sup>, B. B. Lane<sup>14</sup>, R. N. Lang<sup>159</sup>, J. Lange<sup>62</sup>, B. Lantz<sup>51</sup>, R. K. Lanza<sup>14</sup>, A. Lartaux-Vollard<sup>28</sup>, P. D. Lasky<sup>6</sup>, M. Laxen<sup>7</sup>, A. Lazzarini<sup>1</sup>, C. Lazzaro<sup>54</sup>, P. Leaci<sup>33,119</sup>, S. Leavey<sup>9,10</sup>, Y. K. Lecoeuche<sup>47</sup>, C. H. Lee<sup>97</sup>, H. K. Lee<sup>160</sup>, H. M. Lee<sup>161</sup>, H. W. Lee<sup>151</sup>, J. Lee<sup>96</sup>, K. Lee<sup>46</sup>, J. Lehmann<sup>9,10</sup>, A. K. Lenon<sup>39</sup>, N. Leroy<sup>28</sup>, N. Letendre<sup>34</sup>, Y. Levin<sup>6</sup>, A. Li<sup>94</sup>, J. Li<sup>84</sup>, K. J. L. Li<sup>94</sup>, T. G. F. Li<sup>94</sup>, X. Li<sup>48</sup>, F. Lin<sup>6</sup>, F. Linde<sup>37,162</sup>, S. D. Linker<sup>133</sup>, T. B. Littenberg<sup>163</sup>, J. Liu<sup>66</sup>, X. Liu<sup>24</sup>, M. Llorens-Monteagudo<sup>22</sup>, R. K. L. Lo<sup>1,94</sup>, L. T. London<sup>14</sup>, A. Longo<sup>164,165</sup>, M. Lorenzini<sup>16,17</sup>, V. Loriette<sup>166</sup>, M. Lormand<sup>7</sup>, G. Losurdo<sup>21</sup>, J. D. Lough<sup>9,10</sup>, C. O. Lousto<sup>62</sup>, G. Lovelace<sup>27</sup>, M. E. Lower<sup>167</sup>, H. Lück<sup>9,10</sup>, D. Lumaca<sup>32,86</sup>, A. P. Lundgren<sup>140</sup>, R. Lynch<sup>14</sup>, Y. Ma<sup>48</sup>, R. Macas<sup>106</sup>, S. Macfoy<sup>25</sup>, M. MacInnis<sup>14</sup>, D. M. Macleod<sup>106</sup>, A. Macquet<sup>65</sup>, I. Magaña Hernandez<sup>24</sup>, F. Magaña-Sandoval<sup>30</sup>, R. M. Magee<sup>90</sup>, E. Majorana<sup>33</sup>, I. Maksimovic<sup>166</sup>, A. Malik<sup>60</sup>, N. Man<sup>65</sup>, V. Mandic<sup>43</sup>, V. Mangano<sup>33,46,119</sup>, G. L. Mansell<sup>14,47</sup>, M. Manske<sup>24</sup>, M. Mantovani<sup>29</sup>, M. Mapelli<sup>53,54</sup>, F. Marchesoni<sup>41,52</sup>, F. Marion<sup>34</sup>, S. Márka<sup>105</sup>, Z. Márka<sup>105</sup>, C. Markakis<sup>19</sup>, A. S. Markosyan<sup>51</sup>, A. Markowitz<sup>1</sup>, E. Maros<sup>1</sup>, A. Marquina<sup>104</sup>, S. Marsat<sup>26</sup>, F. Martelli<sup>63,64</sup>, I. W. Martin<sup>46</sup>, R. M. Martin<sup>36</sup>, V. Martinez<sup>79</sup>, D. V. Martynov<sup>13</sup>, H. Masalehdan<sup>134</sup>, K. Mason<sup>14</sup>, E. Massera<sup>112</sup>, A. Masserot<sup>34</sup>, T. J. Massinger<sup>1</sup>, M. Masso-Reid<sup>46</sup>, S. Mastrogiovanni<sup>26</sup>, A. Matas<sup>76</sup>, F. Matichard<sup>1,14</sup>, L. Matone<sup>105</sup>, N. Mavalvala<sup>14</sup>, J. J. McCann<sup>66</sup>, R. McCarthy<sup>47</sup>, D. E. McClelland<sup>8</sup>, S. McCormick<sup>7</sup>, L. McCuller<sup>14</sup>, S. C. McGuire<sup>168</sup>, C. McIsaac<sup>140</sup>, J. McIver<sup>1</sup>, D. J. McManus<sup>8</sup>, T. McRae<sup>8</sup>, S. T. McWilliams<sup>39</sup>, D. Meacher<sup>24</sup>, G. D. Meadors<sup>6</sup>, M. Mehmet<sup>9,10</sup>, A. K. Mehta<sup>18</sup>, J. Meidam<sup>37</sup>, E. Mejuto Villa<sup>69,116</sup>, A. Melatos<sup>100</sup>, G. Mendell<sup>47</sup>, R. A. Mercer<sup>24</sup>, L. Mereni<sup>23</sup>, K. Merfeld<sup>72</sup>, E. L. Merilh<sup>47</sup>, M. Merzougui<sup>65</sup>, S. Meshkov<sup>1</sup>, C. Messenger<sup>46</sup>, C. Messick<sup>90</sup>, F. Messina<sup>44,45</sup>, R. Metzdorff<sup>73</sup>, P. M. Meyers<sup>100</sup>, F. Meylahn<sup>9,10</sup>, A. Miani<sup>117,118</sup>, H. Miao<sup>13</sup>, C. Michel<sup>23</sup>, H. Middleton<sup>100</sup>, L. Milano<sup>5,80</sup>, A. L. Miller<sup>30,33,119</sup>, M. Millhouse<sup>100</sup>, J. C. Mills<sup>106</sup>, M. C. Milovich-Goff<sup>133</sup>, O. Minazzoli<sup>65,169</sup>, Y. Minenkov<sup>32</sup>, A. Mishkin<sup>30</sup>, C. Mishra<sup>170</sup>, T. Mistry<sup>112</sup>, S. Mitra<sup>3</sup>, V. P. Mitrofanov<sup>61</sup>, G. Mitselmakher<sup>30</sup>, R. Mittleman<sup>14</sup>, G. Mo<sup>98</sup>, D. Moffa<sup>121</sup>, K. Mogushi<sup>87</sup>, S. R. P. Mohapatra<sup>14</sup>, M. Molina-Ruiz<sup>141</sup>, M. Mondin<sup>133</sup>, M. Montani<sup>63,64</sup>, C. J. Moore<sup>13</sup>, D. Moraru<sup>47</sup>, F. Morawski<sup>56</sup>, G. Moreno<sup>47</sup>, S. Morisaki<sup>83</sup>, B. Mours<sup>34</sup>, C. M. Mow-Lowry<sup>13</sup>, F. Muciaccia<sup>33,119</sup>, Arunava Mukherjee<sup>9,10</sup>, D. Mukherjee<sup>24</sup>, S. Mukherjee<sup>108</sup>, Subroto Mukherjee<sup>111</sup>, N. Mukund<sup>3,9,10</sup>, A. Mullavey<sup>7</sup>, J. Munch<sup>57</sup>, E. A. Muñiz<sup>42</sup>, M. Muratore<sup>35</sup>, P. G. Murray<sup>46</sup>, I. Nardecchia<sup>32,86</sup>, L. Naticchioni<sup>33,119</sup>, R. K. Nayak<sup>171</sup>, B. F. Neil<sup>66</sup>, J. Neilson<sup>69,116</sup>, G. Nelemans<sup>37,67</sup>, T. J. N. Nelson<sup>7</sup>, M. Nery<sup>9,10</sup>, A. Neunzert<sup>137</sup>, L. Nevin<sup>1</sup>, K. Y. Ng<sup>14</sup>, S. Ng<sup>57</sup>, C. Nguyen<sup>26</sup>, P. Nguyen<sup>72</sup>, D. Nichols<sup>37,142</sup>, S. A. Nichols<sup>2</sup>, S. Nissanke<sup>37,142</sup>, F. Nocera<sup>29</sup>, C. North<sup>106</sup>, L. K. Nuttall<sup>140</sup>, M. Obergaulinger<sup>22,172</sup>, J. Oberling<sup>47</sup>, B. D. O'Brien<sup>30</sup>, G. Oganesyan<sup>16,17</sup>, G. H. Ogin<sup>173</sup>, J. J. Oh<sup>152</sup>, S. H. Oh<sup>152</sup>, F. Ohme<sup>9,10</sup>, H. Ohta<sup>83</sup>, M. A. Okada<sup>15</sup>, M. Oliver<sup>101</sup>, P. Oppermann<sup>9,10</sup>, Richard J. Oram<sup>7</sup>, B. O'Reilly<sup>7</sup>, R. G. Ormiston<sup>43</sup>, L. F. Ortega<sup>30</sup>, R. O'Shaughnessy<sup>62</sup>, S. Ossokine<sup>76</sup>, D. J. Ottaway<sup>57</sup>, H. Overmier<sup>7</sup>, B. J. Owen<sup>85</sup>, A. E. Pace<sup>90</sup>, G. Pagano<sup>20,21</sup>, M. A. Page<sup>66</sup>, G. Pagliaroli<sup>16,17</sup>, A. Pai<sup>130</sup>, S. A. Pai<sup>60</sup>, J. R. Palamos<sup>72</sup>, O. Palashov<sup>149</sup>, C. Palomba<sup>33</sup>, H. Pan<sup>91</sup>, P. K. Panda<sup>144</sup>, P. T. H. Pang<sup>37,94</sup>, C. Pankow<sup>58</sup>, F. Pannarale<sup>33,119</sup>, B. C. Pant<sup>60</sup>, F. Paoletti<sup>21</sup>, A. Paoli<sup>29</sup>, A. Parida<sup>3</sup>, W. Parker<sup>7,168</sup>, D. Pascucci<sup>37,46</sup>, A. Pasqualetti<sup>29</sup>, R. Passaquietti<sup>20,21</sup>, D. Passuello<sup>21</sup>, M. Patil<sup>157</sup>, B. Patricelli<sup>20,21</sup>, E. Payne<sup>6</sup>, B. L. Pearlstone<sup>46</sup>, T. C. Pechsiri<sup>30</sup>, A. J. Pedersen<sup>42</sup>, M. Pedraza<sup>1</sup>, R. Pedurand<sup>23,174</sup>, A. Pele<sup>7</sup>, S. Penn<sup>175</sup>, A. Perego<sup>117,118</sup>, C. J. Perez<sup>47</sup>, C. Périgois<sup>34</sup>, A. Perreca<sup>117,118</sup>, J. Petermann<sup>134</sup>, H. P. Pfeiffer<sup>76</sup>, M. Phelps<sup>9,10</sup>, K. S. Phukon<sup>3</sup>, O. J. Piccinni<sup>33,119</sup>, M. Pichot<sup>65</sup>, F. Piergiovanni<sup>63,64</sup>, V. Pierro<sup>69,116</sup>, G. Pillant<sup>29</sup>, L. Pinard<sup>23</sup>, I. M. Pinto<sup>69,89,116</sup>, M. Pirello<sup>47</sup>, M. Pitkin<sup>46</sup>, W. Plastino<sup>164,165</sup>, R. Poggiani<sup>20,21</sup>, D. Y. T. Pong<sup>94</sup>, S. Ponrathnam<sup>3</sup>, P. Popolizio<sup>29</sup>, E. K. Porter<sup>26</sup>, J. Powell<sup>167</sup>, A. K. Prajapati<sup>111</sup>, J. Prasad<sup>3</sup>, K. Prasai<sup>51</sup>, R. Prasanna<sup>144</sup>, G. Pratten<sup>101</sup>, T. Prestegard<sup>24</sup>, M. Principe<sup>69,89,116</sup>, G. A. Prodi<sup>117,118</sup>, L. Prokhorov<sup>13</sup>, M. Punturo<sup>41</sup>, P. Puppo<sup>33</sup>, M. Pürrer<sup>76</sup>, H. Qi<sup>106</sup>, V. Quetschke<sup>108</sup>, P. J. Quinonez<sup>35</sup>, F. J. Raab<sup>47</sup>, G. Raaijmakers<sup>37,142</sup>, H. Radkins<sup>47</sup>, N. Radulesco<sup>65</sup>, P. Raffai<sup>110</sup>, S. Raja<sup>60</sup>, C. Rajan<sup>60</sup>, B. Rajbhandari<sup>85</sup>, M. Rakhmanov<sup>108</sup>, K. E. Ramirez<sup>108</sup>, A. Ramos-Buades<sup>101</sup>, Javed Rana<sup>3</sup>, K. Rao<sup>58</sup>, P. Rapagnani<sup>33,119</sup>, V. Raymond<sup>106</sup>
M. Razzano<sup>20,21</sup>, J. Read<sup>27</sup>, T. Regimbau<sup>34</sup>, L. Rei<sup>59</sup>, S. Reid<sup>25</sup>, D. H. Reitzel<sup>1,30</sup>, P. Rettegno<sup>127,176</sup>, F. Ricci<sup>33,119</sup>, C. J. Richardson<sup>35</sup>, J. W. Richardson<sup>1</sup>, P. M. Ricker<sup>19</sup>, G. Riemenschneider<sup>127,176</sup>, K. Riles<sup>137</sup>, M. Rizzo<sup>58</sup>, N. A. Robertson<sup>1,46</sup>, F. Robinet<sup>28</sup>, A. Rocchi<sup>32</sup>, L. Rolland<sup>34</sup>, J. G. Rollins<sup>1</sup>, V. J. Roma<sup>72</sup>, M. Romanelli<sup>71</sup>, R. Romano<sup>4,5</sup>, C. L. Romel<sup>47</sup>, J. H. Romie<sup>7</sup>, C. A. Rose<sup>24</sup>, D. Rose<sup>27</sup>, K. Rose<sup>121</sup>, D. Rosińska<sup>74</sup>, S. G. Rosofsky<sup>19</sup>, M. P. Ross<sup>177</sup>, S. Rowan<sup>46</sup>, A. Rüdiger<sup>9,10,192</sup>, P. Ruggi<sup>29</sup>, G. Rutins<sup>132</sup>, K. Ryan<sup>47</sup>, S. Sachdev<sup>90</sup>, T. Sadecki<sup>47</sup>, M. Sakellariadou<sup>146</sup>, O. S. Salafia<sup>44,45,178</sup>, L. Salconi<sup>29</sup>, M. Saleem<sup>31</sup>, A. Samajdar<sup>37</sup>, L. Sammut<sup>6</sup>, E. J. Sanchez<sup>1</sup>, L. E. Sanchez<sup>1</sup>, N. Sanchis-Gual<sup>179</sup>, J. R. Sanders<sup>180</sup>, K. A. Santiago<sup>36</sup>, E. Santos<sup>65</sup>, N. Sarin<sup>6</sup>, B. Sassolas<sup>23</sup>, O. Sauter<sup>34,137</sup>, R. L. Savage<sup>47</sup>, P. Schale<sup>72</sup>, M. Scheel<sup>48</sup>, J. Scheuer<sup>58</sup>, P. Schmidt<sup>13,67</sup>, R. Schnabel<sup>134</sup>, R. M. S. Schofield<sup>72</sup>, A. Schönbeck<sup>134</sup>, E. Schreiber<sup>9,10</sup>, B. W. Schulte<sup>9,10</sup>, B. F. Schutz<sup>106</sup>, J. Scott<sup>46</sup>, S. M. Scott<sup>8</sup>, E. Seidel<sup>19</sup>, D. Sellers<sup>7</sup>, A. S. Sengupta<sup>181</sup>, N. Sennett<sup>76</sup>, D. Sentenac<sup>29</sup>, V. Sequino<sup>59</sup>, A. Sergeev<sup>149</sup>, Y. Setyawati<sup>9,10</sup>, D. A. Shaddock<sup>8</sup>, T. Shaffer<sup>47</sup>, M. S. Shahriar<sup>58</sup>, M. B. Shaner<sup>133</sup>, A. Sharma<sup>16,17</sup>, P. Sharma<sup>60</sup>, P. Shawhan<sup>77</sup>, H. Shen<sup>19</sup>, R. Shink<sup>182</sup>, D. H. Shoemaker<sup>14</sup>, D. M. Shoemaker<sup>78</sup>, K. Shukla<sup>141</sup>, S. ShyamSundar<sup>60</sup>, K. Siellez<sup>78</sup>, M. Sieniawska<sup>56</sup>, D. Sigg<sup>47</sup>, L. P. Singer<sup>81</sup>, D. Singh<sup>90</sup>, N. Singh<sup>74</sup>, A. Singhal<sup>16,33</sup>, A. M. Sintes<sup>101</sup>, S. Sitmukhambetov<sup>108</sup>, V. Skliris<sup>106</sup>, B. J. J. Slagmolen<sup>8</sup>, T. J. Slaven-Blair<sup>66</sup>, J. R. Smith<sup>27</sup>, R. J. E. Smith<sup>6</sup>, S. Somala<sup>183</sup>, E. J. Son<sup>152</sup>, S. Soni<sup>2</sup>, B. Sorazu<sup>46</sup>, F. Sorrentino<sup>59</sup>, T. Souradeep<sup>3</sup>, E. Sowell<sup>85</sup>, A. P. Spencer<sup>46</sup>, M. Spera<sup>53,54</sup>, A. K. Srivastava<sup>111</sup>, V. Srivastava<sup>42</sup>, K. Staats<sup>58</sup>, C. Stachie<sup>65</sup>, M. Standke<sup>9,10</sup>, D. A. Steer<sup>26</sup>, M. Steinke<sup>9,10</sup>, J. Steinlechner<sup>46,134</sup>, S. Steinlechner<sup>134</sup>, D. Steinmeyer<sup>9,10</sup>, S. P. Stevenson<sup>167</sup>, D. Stocks<sup>51</sup>, R. Stone<sup>108</sup>, D. J. Stops<sup>13</sup>, K. A. Strain<sup>46</sup>, G. Stratta<sup>64,184</sup>, S. E. Strigin<sup>61</sup>, A. Strunk<sup>47</sup>, R. Sturani<sup>185</sup>, A. L. Stuver<sup>186</sup>, V. Sudhir<sup>14</sup>, T. Z. Summerscales<sup>187</sup>, L. Sun<sup>1</sup>, S. Sunil<sup>111</sup>, A. Sur<sup>56</sup>, J. Suresh<sup>83</sup>, P. J. Sutton<sup>106</sup>, B. L. Swinkels<sup>37</sup>, M. J. Szczepańczyk<sup>35</sup>, M. Tacca<sup>37</sup>, S. C. Tait<sup>46</sup>, C. Talbot<sup>6</sup>, D. B. Tanner<sup>30</sup>, D. Tao<sup>1</sup>, M. Tápai<sup>131</sup>, A. Tapia<sup>27</sup>, J. D. Tasson<sup>98</sup>, R. Taylor<sup>1</sup>, R. Tenorio<sup>101</sup>, L. Terkowski<sup>134</sup>, M. Thomas<sup>7</sup>, P. Thomas<sup>47</sup>, S. R. Thondapu<sup>60</sup>, K. A. Thorne<sup>7</sup>, E. Thrane<sup>6</sup>, Shubhanshu Tiwari<sup>117,118</sup>, Srishti Tiwari<sup>135</sup>, V. Tiwari<sup>106</sup>, K. Toland<sup>46</sup>, M. Tonelli<sup>20,21</sup>, Z. Tornasi<sup>46</sup>, A. Torres-Forné<sup>188</sup>, C. I. Torrie<sup>1</sup>, D. Töyrä<sup>13</sup>, F. Travasso<sup>29,41</sup>, G. Traylor<sup>7</sup>, M. C. Tringali<sup>74</sup>, A. Tripathe<sup>137</sup>, A. Trovato<sup>26</sup>, L. Trozzo<sup>21,189</sup>, K. W. Tsang<sup>37</sup>, M. Tse<sup>14</sup>, R. Tso<sup>48</sup>, L. Tsukada<sup>83</sup>, D. Tsuna<sup>83</sup>, T. Tsutsui<sup>83</sup>, D. Tuyenbayev<sup>108</sup>, K. Ueno<sup>83</sup>, D. Ugolini<sup>190</sup>, C. S. Unnikrishnan<sup>135</sup>, A. L. Urban<sup>2</sup>, S. A. Usman<sup>93</sup>, H. Vahlbruch<sup>10</sup>, G. Vajente<sup>1</sup>, G. Valdes<sup>2</sup>, M. Valentini<sup>117,118</sup>, N. van Bakel<sup>37</sup>, M. van Beuzekom<sup>37</sup>, J. F. J. van den Brand<sup>37,75</sup>, C. Van Den Broeck<sup>37,191</sup>, D. C. Vander-Hyde<sup>42</sup>, L. van der Schaaf<sup>37</sup>, J. V. VanHeijningen<sup>66</sup>, A. A. van Veggel<sup>46</sup>, M. Vardaro<sup>53,54</sup>, V. Varma<sup>48</sup>, S. Vass<sup>1</sup>, M. Vasúth<sup>50</sup>, A. Vecchio<sup>13</sup>, G. Vedovato<sup>54</sup>, J. Veitch<sup>46</sup>, P. J. Veitch<sup>57</sup>, K. Venkateswara<sup>177</sup>, G. Venugopalan<sup>1</sup>, D. Verkindt<sup>34</sup>, F. Vetrano<sup>63,64</sup>, A. Vicere<sup>63,64</sup>, A. D. Viets<sup>24</sup>, S. Vinciguerra<sup>13</sup>, D. J. Vine<sup>132</sup>, J.-Y. Vinet<sup>65</sup>, S. Vitale<sup>14</sup>, T. Vo<sup>42</sup>, H. Vocca<sup>40,41</sup>, C. Vorvick<sup>47</sup>, S. P. Vyatchanin<sup>61</sup>, A. R. Wade<sup>1</sup>, L. E. Wade<sup>121</sup>, M. Wade<sup>121</sup>, R. Walet<sup>37</sup>, M. Walker<sup>27</sup>, L. Wallace<sup>1</sup>, S. Walsh<sup>24</sup>, H. Wang<sup>13</sup>, J. Z. Wang<sup>137</sup>, S. Wang<sup>19</sup>, W. H. Wang<sup>108</sup>, Y. F. Wang<sup>94</sup>, R. L. Ward<sup>8</sup>, Z. A. Warden<sup>35</sup>, J. Warner<sup>47</sup>, M. Was<sup>34</sup>, J. Watchi<sup>102</sup>, B. Weaver<sup>47</sup>, L.-W. Wei<sup>9,10</sup>, M. Weinert<sup>9,10</sup>, A. J. Weinstein<sup>1</sup>, R. Weiss<sup>14</sup>, F. Wellmann<sup>9,10</sup>, L. Wen<sup>66</sup>, E. K. Wessel<sup>19</sup>, P. Weßels<sup>9,10</sup>, J. W. Westhouse<sup>35</sup>, K. Wette<sup>8</sup>, J. T. Whelan<sup>62</sup>, B. F. Whiting<sup>30</sup>, C. Whittle<sup>14</sup>, D. M. Wilken<sup>9,10</sup>, D. Williams<sup>46</sup>, A. R. Williamson<sup>37,142</sup>, J. L. Willis<sup>1</sup>, B. Willke<sup>9,10</sup>, W. Winkler<sup>9,10</sup>, C. C. Wipf<sup>1</sup>, H. Wittel<sup>9,10</sup>, G. Woan<sup>46</sup>, J. Woehler<sup>9,10</sup>, J. K. Wofford<sup>62</sup>, J. L. Wright<sup>46</sup>, D. S. Wu<sup>9,10</sup>, D. M. Wysocki<sup>62</sup>, S. Xiao<sup>1</sup>, R. Xu<sup>109</sup>, H. Yamamoto<sup>1</sup>, C. C. Yancey<sup>77</sup>, L. Yang<sup>120</sup>, Y. Yang<sup>30</sup>, Z. Yang<sup>43</sup>, M. J. Yap<sup>8</sup>, M. Yazback<sup>30</sup>, D. W. Yeeles<sup>106</sup>, Hang Yu<sup>14</sup>, Haocun Yu<sup>14</sup>, S. H. R. Yuen<sup>94</sup>, A. K. Zadrożny<sup>108</sup>, A. Zadrożny<sup>156</sup>, M. Zanolin<sup>35</sup>, T. Zelenova<sup>29</sup>, J.-P. Zendri<sup>54</sup>, M. Zevin<sup>58</sup>, J. Zhang<sup>66</sup>, L. Zhang<sup>1</sup>, T. Zhang<sup>46</sup>, C. Zhao<sup>66</sup>, G. Zhao<sup>102</sup>, M. Zhou<sup>58</sup>, Z. Zhou<sup>58</sup>, X. J. Zhu<sup>6</sup>, M. E. Zucker<sup>1,14</sup>, J. Zweizig<sup>1</sup>

(The LIGO Scientific Collaboration and the Virgo Collaboration), and
F. Salemi<sup>9</sup>

<footnote n="1"><sup>1</sup> LIGO, California Institute of Technology, Pasadena, CA 91125, USA</footnote>

<footnote n="2"><sup>2</sup> Louisiana State University, Baton Rouge, LA 70803, USA</footnote>

<footnote n="3"><sup>3</sup> Inter-University Centre for Astronomy and Astrophysics, Pune 411007, India</footnote>

<footnote n="4"><sup>4</sup> Dipartimento di Farmacia, Università di Salerno, I-84084 Fisciano, Salerno, Italy</footnote>

<footnote n="5"><sup>5</sup> INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, I-80126 Napoli, Italy</footnote>

<footnote n="6"><sup>6</sup> OzGrav, School of Physics & Astronomy, Monash University, Clayton 3800, Victoria, Australia</footnote>

<footnote n="7"><sup>7</sup> LIGO Livingston Observatory, Livingston, LA 70754, USA</footnote>

<footnote n="8"><sup>8</sup> OzGrav, Australian National University, Canberra, Australian Capital Territory 0200, Australia</footnote>

<footnote n="9"><sup>9</sup> Max Planck Institute for Gravitational Physics (Albert Einstein Institute), D-30167 Hannover, Germany</footnote>

<footnote n="10"><sup>10</sup> Leibniz Universität Hannover, D-30167 Hannover, Germany</footnote>

<footnote n="11"><sup>11</sup> Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, D-07743 Jena, Germany</footnote>

<footnote n="12"><sup>12</sup> University of Cambridge, Cambridge CB2 1TN, UK</footnote>

<footnote n="13"><sup>13</sup> University of Birmingham, Birmingham B15 2TT, UK</footnote>

<footnote n="14"><sup>14</sup> LIGO, Massachusetts Institute of Technology, Cambridge, MA 02139, USA</footnote>

<footnote n="15"><sup>15</sup> Instituto Nacional de Pesquisas Espaciais, 12227-010 São José dos Campos, São Paulo, Brazil</footnote>

<footnote n="16"><sup>16</sup> Gran Sasso Science Institute (GSSI), I-67100 L'Aquila, Italy</footnote>

<footnote n="17"><sup>17</sup> INFN, Laboratori Nazionali del Gran Sasso, I-67100 Assergi, Italy</footnote>

<footnote n="18"><sup>18</sup> International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India</footnote>

<footnote n="19"><sup>19</sup> NCSA, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA</footnote>

<footnote n="20"><sup>20</sup> Università di Pisa, I-56127 Pisa, Italy</footnote>

<footnote n="21"><sup>21</sup> INFN, Sezione di Pisa, I-56127 Pisa, Italy</footnote>

<footnote n="22"><sup>22</sup> Departamento de Astronomía y Astrofísica, Universitat de València, E-46100 Burjassot, València, Spain</footnote>

<footnote n="23"><sup>23</sup> Laboratoire des Matériaux Avancés (LMA), CNRS/IN2P3, F-69622 Villeurbanne, France</footnote>

<footnote n="24"><sup>24</sup> University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA</footnote>

<footnote n="25"><sup>25</sup> SUPA, University of Strathclyde, Glasgow G1 XQ, UK</footnote>
²⁶ APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, F-75205 Paris Cedex 13, France

²⁷ California State University Fullerton, Fullerton, CA 92831, USA

²⁸ LAL, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, F-91898 Orsay, France

²⁹ European Gravitational Observatory (EGO), I-56021 Cascina, Pisa, Italy

³⁰ University of Florida, Gainesville, FL 32611, USA

³¹ Chennai Mathematical Institute, Chennai 603103, India

³² INFN, Sezione di Roma Tor Vergata, I-00133 Roma, Italy

³³ INFN, Sezione di Roma, I-00185 Roma, Italy

³⁴ Laboratoire d'Annecy de Physique des Particules (LAPP), Univ. Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, F-74941 Annecy, France

³⁵ Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA

³⁶ Montclair State University, Montclair, NJ 07043, USA

³⁷ Nikhef, Science Park 105, 1098 XG Amsterdam, The Netherlands

³⁸ Korea Institute of Science and Technology Information, Daejeon 34141, Republic of Korea

³⁹ West Virginia University, Morgantown, WV 26506, USA

⁴⁰ Università di Perugia, I-06123 Perugia, Italy

⁴¹ INFN, Sezione di Perugia, I-06123 Perugia, Italy

⁴² Syracuse University, Syracuse, NY 13244, USA

⁴³ University of Minnesota, Minneapolis, MN 55455, USA

⁴⁴ Università degli Studi di Milano-Bicocca, I-20126 Milano, Italy

⁴⁵ INFN, Sezione di Milano-Bicocca, I-20126 Milano, Italy

⁴⁶ SUPA, University of Glasgow, Glasgow G12 8QQ, UK

⁴⁷ LIGO Hanford Observatory, Richland, WA 99352, USA

⁴⁸ Caltech CaRT, Pasadena, CA 91125, USA

⁴⁹ Dipartimento di Medicina, Chirurgia e Odontoiatria “Scuola Medica Salernitana,” Università di Salerno, I-84081 Baronissi, Salerno, Italy

⁵⁰ Wigner RCP, RMIK, H-1121 Budapest, Konkoly Thege Miklós út 29-33, Hungary

⁵¹ Stanford University, Stanford, CA 94305, USA

⁵² Università di Camerino, Dipartimento di Fisica, I-62032 Camerino, Italy

⁵³ Università di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova, Italy

⁵⁴ INFN, Sezione di Padova, I-35131 Padova, Italy

⁵⁵ Montana State University, Bozeman, MT 59717, USA

⁵⁶ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, 00-716, Warsaw, Poland

⁵⁷ OzGrav, University of Adelaide, Adelaide, South Australia 5005, Australia

⁵⁸ Center for Interdisciplinary Exploration & Research in Astrophysics (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, Moscow 119991, Russia

⁶² Rochester Institute of Technology, Rochester, NY 14623, USA

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⁶⁴ INFN, Sezione di Firenze, I-50019 Sesto Fiorentino, Firenze, Italy

⁶⁵ Artemis, Université Côte d'Azur, Observatoire Côte d'Azur, CNRS, CS 34229, F-06304 Nice Cedex 4, France

⁶⁶ OzGrav, University of Western Australia, Crawley, Western Australia 6009, Australia

⁶⁷ Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands

⁶⁸ Dipartimento di Fisica “E.R. Caianiello,” Università di Salerno, I-84084 Fisciano, Salerno, Italy

⁶⁹ INFN, Sezione di Napoli, Gruppo Collegato di Salerno, Complesso Universitario di Monte S. Angelo, I-80126 Napoli, Italy

⁷⁰ Physik-Institut, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland

⁷¹ Univ Rennes, CNRS, Institut FOTON—UMR6082, F-3500 Rennes, France

⁷² University of Oregon, Eugene, OR 97403, USA

⁷³ Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-Université PSL, Collège de France, F-75005 Paris, France

⁷⁴ Astronomical Observatory Warsaw University, 00-478 Warsaw, Poland

⁷⁵ VU University Amsterdam, 1081 HV Amsterdam, The Netherlands

⁷⁶ Max Planck Institute for Gravitational Physics (Albert Einstein Institute), D-14476 Potsdam-Golm, Germany

⁷⁷ University of Maryland, College Park, MD 20742, USA

⁷⁸ School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA

⁷⁹ Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France

⁸⁰ Università di Napoli “Federico II,” Complesso Universitario di Monte S. Angelo, I-80126 Napoli, Italy

⁸¹ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

⁸² Dipartimento di Fisica, Università degli Studi di Genova, I-16146 Genova, Italy

⁸³ RESCEU, University of Tokyo, Tokyo, 113-0033, Japan

⁸⁴ Tsinghua University, Beijing 100084, People's Republic of China

⁸⁵ Texas Tech University, Lubbock, TX 79409, USA

⁸⁶ Università di Roma Tor Vergata, I-00133 Roma, Italy

⁸⁷ The University of Mississippi, University, MS 38677, USA

⁸⁸ Missouri University of Science and Technology, Rolla, MO 65409, USA

⁸⁹ Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi,” I-00184 Roma, Italy

⁹⁰ The Pennsylvania State University, University Park, PA 16802, USA

⁹¹ National Tsing Hua University, Hsinchu City, 30013 Taiwan, Republic of People's Republic of China

⁹² Charles Sturt University, Wagga Wagga, New South Wales 2678, Australia

⁹³ University of Chicago, Chicago, IL 60637, USA

⁹⁴ The Chinese University of Hong Kong, Shatin, NT, Hong Kong

⁹⁵ Dipartimento di Ingegneria Industriale (DIIN), Università di Salerno, I-84084 Fisciano, Salerno, Italy

⁹⁶ Seoul National University, Seoul 08826, Republic of Korea

⁹⁷ Pusan National University, Busan 46241, Republic of Korea

⁹⁸ Carleton College, Northfield, MN 55057, USA

⁹⁹ INAF, Osservatorio Astronomico di Padova, I-35122 Padova, Italy

¹⁰⁰ OzGrav, University of Melbourne, Parkville, Victoria 3010, Australia
101 Universitat de les Illes Balears, IAC3—IEEC, E-07122 Palma de Mallorca, Spain

102 Université Libre de Bruxelles, Brussels B-1050, Belgium

103 Sonoma State University, Rohnert Park, CA 94928, USA

104 Departamento de Matemáticas, Universitat de València, E-46100 Burjassot, València, Spain

105 Columbia University, New York, NY 10027, USA

106 Cardiff University, Cardiff CF24 3AA, UK

107 University of Rhode Island, Kingston, RI 02881, USA

108 The University of Texas Rio Grande Valley, Brownsville, TX 78520, USA

109 Bellevue College, Bellevue, WA 98007, USA

110 MTA-ELTE Astrophysics Research Group, Institute of Physics, Eötvös University, Budapest 1117, Hungary

111 Institute for Plasma Research, Bhat, Gandhinagar 382428, India

112 The University of Sheffield, Sheffield S10 2TN, UK

113 IGFAE, Campus Sur, Universidade de Santiago de Compostela, E-15782 Spain

114 Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università di Parma, I-43124 Parma, Italy

115 INFN, Sezione di Milano Bicocca, Gruppo Collegato di Parma, I-43124 Parma, Italy

116 Dipartimento di Ingegneria, Università del Sannio, I-82100 Benevento, Italy

117 Università di Trento, Dipartimento di Fisica, I-38123 Povo, Trento, Italy

118 INFN, Trento Institute for Fundamental Physics and Applications, I-38123 Povo, Trento, Italy

119 Università di Roma “La Sapienza,” I-00185 Roma, Italy

120 Colorado State University, Fort Collins, CO 80523, USA

121 Kenyon College, Gambier, OH 43022, USA

122 Christopher Newport University, Newport News, VA 23606, USA

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124 Scuola di Ingegneria, Università della Basilicata, I-85100 Potenza, Italy

125 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

126 Observatori Astronòmic, Universitat de València, E-46980 Paterna, València, Spain

127 INFN Sezione di Torino, I-10125 Torino, Italy

128 School of Mathematics, University of Edinburgh, Edinburgh EH9 3FD, UK

129 Institute Of Advanced Research, Gandhinagar 382426, India

130 Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India

131 University of Szeged, Döm tér 9, Szeged 6720, Hungary

132 SUPA, University of the West of Scotland, Paisley PA1 2BE, UK

133 California State University, Los Angeles, 5151 State University Dr, Los Angeles, CA 90032, USA

134 Universität Hamburg, D-22761 Hamburg, Germany

135 Tata Institute of Fundamental Research, Mumbai 400005, India

136 INAF, Osservatorio Astronomico di Capodimonte, I-80131 Napoli, Italy

137 University of Michigan, Ann Arbor, MI 48109, USA

138 Washington State University, Pullman, WA 99164, USA

139 American University, Washington, D.C. 20016, USA

140 University of Portsmouth, Portsmouth, PO1 3FX, UK

141 University of California, Berkeley, CA 94720, USA

142 GRAPPA, Anton Pannekoek Institute for Astronomy and Institute for High-Energy Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

143 Delta Institute for Theoretical Physics, Science Park 904, 1090 GL Amsterdam, The Netherlands

144 Directorate of Construction, Services & Estate Management, Mumbai 400094 India

145 University of Białystok, 15-424 Białystok, Poland

146 King's College London, University of London, London WC2R 2LS, UK

147 University of Southampton, Southampton SO17 1BJ, UK

148 University of Washington Bothell, Bothell, WA 98011, USA

149 Institute of Applied Physics, Nizhny Novgorod, 603950, Russia

150 Ewha Womans University, Seoul 03760, Republic of Korea

151 Inje University Gimhae, South Gyeongsang 50834, Republic of Korea

152 National Institute for Mathematical Sciences, Daejeon 34047, Republic of Korea

153 Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea

154 Maastricht University, P.O. Box 616, 6200 MD Maastricht, The Netherlands

155 Bard College, 30 Campus Rd, Annandale-On-Hudson, NY 12504, USA

156 NCBJ, 05-400 Świerk-Otwock, Poland

157 Institute of Mathematics, Polish Academy of Sciences, 00656 Warsaw, Poland

158 Cornell University, Ithaca, NY 14850, USA

159 Hillsdale College, Hillsdale, MI 49242, USA

160 Hanyang University, Seoul 04763, Republic of Korea

161 Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea

162 Institute for High-Energy Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

163 NASA Marshall Space Flight Center, Huntsville, AL 35811, USA

164 Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, I-00146 Roma, Italy

165 INFN, Sezione di Roma Tre, I-00146 Roma, Italy

166 ESPCI, CNRS, F-75005 Paris, France

167 OzGrav, Swinburne University of Technology, Hawthorn VIC 3122, Australia

168 Southern University and A&M College, Baton Rouge, LA 70813, USA

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170 Indian Institute of Technology Madras, Chennai 600036, India

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172 Institut für Kernphysik, Theoriezentrum, D-64289 Darmstadt, Germany

173 Whitman College, 345 Boyer Avenue, Walla Walla, WA 99362 USA

174 Université de Lyon, F-69361 Lyon, France

175 Hobart and William Smith Colleges, Geneva, NY 14456, USA
## Abstract

When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits ($e > 0.1$ at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template-based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates $\gtrsim 100 \text{ Gpc}^{-3} \text{ yr}^{-1}$ for $e > 0.1$, assuming a black hole mass spectrum with a power-law index $\lesssim 2$.

*Unified Astronomy Thesaurus concepts: Gravitational waves (678); Elliptical orbits (457); Astrophysical black holes (98)*

## 1. Introduction

In their first two observing runs, the Advanced LIGO and Advanced Virgo detectors discovered 10 binary black hole (BBH) mergers and a binary neutron star merger (Abbott et al. 2019e). These detections have already provided a wealth of information on cosmic processes, including the rate, mass, spin, and redshift distribution of BBH mergers (Abbott et al. 2016f, 2019d), constraints on general relativity (Abbott et al. 2016e, 2019c), estimates of the Hubble constant (Abbott et al. 2017a, 2019b; Soares-Santos et al. 2019), and constraints on multi-messenger emission from the mergers (Abbott et al. 2008, 2016d, 2019a; Adrián-Martínez et al. 2016; Albert et al. 2017; Burns et al. 2019).

A key question that remains unanswered is how BBHs are formed. Viable formation channels include isolated binary evolution (e.g., Bethe & Brown 1998; Belczynski et al. 2002, 2014, 2016; Dominik et al. 2013; Mennekens & Vanbeveren 2014; Spera et al. 2015; Eldridge & Stanway 2016; Mandel & de Mink 2016; Marchant et al. 2016; Mapelli et al. 2017; Stevenson et al. 2017; Barrett et al. 2018; Giacobbo & Mapelli 2018; Kruckow et al. 2018; Mapelli & Giacobbo 2018) and dynamical encounters in dense stellar environments, such as globular clusters (e.g., Portegies Zwart & McMillan 2000;

O'Leary et al. 2006; Sadowski et al. 2008; Downing et al. 2010, 2011; Rodriguez et al. 2015, 2016a, 2016b; Askar et al. 2017; Fragione & Kocsis 2018; Rodriguez & Loeb 2018; Samsing 2018; Samsing et al. 2018; Zevin et al. 2019), young star clusters (e.g., Banerjee et al. 2010; Ziosi et al. 2014; Mapelli 2016; Banerjee 2017, 2018; Di Carlo et al. 2019; Kumamoto et al. 2019), and galactic nuclei (e.g., O'Leary et al. 2009; Antonini & Perets 2012; Antonini & Rasio 2016; Petrovich & Antonini 2017; Stone et al. 2017a, 2017b; Rasskazov & Kocsis 2019). Moreover, the dynamical process known as Kozai-Lidov (KL) resonance (Kozai 1962; Lidov 1962) can trigger the merger of a BBH, even if the BBH has not been formed in a dense star cluster. In fact, if the BBH is orbited by a tertiary body (i.e., the BBH is the inner binary of a stable hierarchical triple system), the KL mechanism triggers oscillations of the BBH's eccentricity, which might speed up the merger by gravitational-wave emission. Each channel is expected to produce black hole mergers with different mass and spin distributions (Mandel & O'Shaughnessy 2010; Abbott et al. 2016a; Rodriguez et al. 2016c; Farr et al. 2017; Abbott et al. 2019d). The limited statistics from the low number of systems detected through gravitational waves and model uncertainties so far do not allow strong constraints on the formation channels.

Orbital eccentricity is a distinguishing feature of dynamical formation channels. Gravitational-wave emission acts to circularize binary orbits by the time they reach the orbital frequencies to which Advanced LIGO and Advanced Virgo are sensitive ($\gtrsim 10$ Hz). Eccentric orbits in the Advanced LIGO and Advanced Virgo band indicate either that the binary was

<figure><img src="image_3.png" /></figure>

<footnote n="176">¹⁷⁶ Dipartimento di Fisica, Università degli Studi di Torino, I-10125 Torino, Italy</footnote>

<footnote n="177">¹⁷⁷ University of Washington, Seattle, WA 98195, USA</footnote>

<footnote n="178">¹⁷⁸ INAF, Osservatorio Astronomico di Brera sede di Merate, I-23807 Merate, Lecco, Italy</footnote>

<footnote n="179">¹⁷⁹ Centro de Astrofísica e Gravitação (CENTRA), Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal</footnote>

<footnote n="180">¹⁸⁰ Marquette University, 11420 W. Clybourn St., Milwaukee, WI 53233, USA</footnote>

<footnote n="181">¹⁸¹ Indian Institute of Technology, Gandhinagar Ahmedabad Gujarat 382424, India</footnote>

<footnote n="182">¹⁸² Université de Montréal/Polytechnique, Montreal, Quebec H3T 1J4, Canada</footnote>

<footnote n="183">¹⁸³ Indian Institute of Technology Hyderabad, Sangareddy, Khandi, Telangana 502285, India</footnote>

<footnote n="184">¹⁸⁴ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, I-40129 Bologna, Italy</footnote>

<footnote n="185">¹⁸⁵ International Institute of Physics, Universidade Federal do Rio Grande do Norte, Natal RN 59078-970, Brazil</footnote>

<footnote n="186">¹⁸⁶ Villanova University, 800 Lancaster Ave, Villanova, PA 19085, USA</footnote>

<footnote n="187">¹⁸⁷ Andrews University, Berrien Springs, MI 49104, USA</footnote>

<footnote n="188">¹⁸⁸ Max Planck Institute for Gravitational physics (Albert Einstein Institute), D-14476 Potsdam-Golm, Germany</footnote>

<footnote n="189">¹⁸⁹ Università di Siena, I-53100 Siena, Italy</footnote>

<footnote n="190">¹⁹⁰ Trinity University, San Antonio, TX 78212, USA</footnote>

<footnote n="191">¹⁹¹ Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
*Received 2019 July 31; revised 2019 August 10; accepted 2019 August 14; published 2019 September 30*</footnote>

<footnote n="192">¹⁹² Deceased, 2018 July.</footnote>

<footnote>Original content from this work may be used under the terms of the [Creative Commons Attribution 3.0 licence](https://creativecommons.org/licenses/by/3.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.</footnote>
formed with small orbital separation and therefore did not have time to circularize, or that some dynamical process increased the eccentricity. For example, KL-induced mergers are expected to be associated with high eccentricities (Antonini et al. 2017; Fragione & Bromberg 2019; Fragione & Kocsis 2019; Fragione et al. 2019a). The detection of gravitational waves from an eccentric binary would suggest that binary systems can form dynamically, and could help distinguish between different dynamical formation scenarios (KL oscillations in triple systems or dynamical encounters in dense stellar clusters; Lower et al. 2018).

In the following we define eccentricity at the time when the gravitational-wave frequency of the binary is at 10 Hz (Peters & Mathews 1963). Eccentricity constantly evolves during the inspiral.

Template-based gravitational-wave searches used by Advanced LIGO and Advanced Virgo currently do not include eccentric orbital templates (Abbott et al. 2019e). Quasicircular waveform templates are able to detect binaries with small eccentricities ($e \lesssim 0.1$), but are inefficient at extracting moderately to highly eccentric binaries (Brown & Zimmerman 2010). Multiple efforts for generating the full inspiral-merger ringdown waveforms for the binaries with eccentric orbits are underway (Cao & Han 2017; Hinderer & Babak 2017; Hinder et al. 2018; Huerta et al. 2018; Ireland et al. 2019). However, the lack of a reliable and complete waveform model prevents the implementation of a matched-filtering search at this time, and led to the development of alternative search methods (Coughlin et al. 2015; Tiwari et al. 2016; Lower et al. 2018).

Here we report the results of a search for eccentric BBH mergers with the coherent WaveBurst (cWB) algorithm that does not rely on binary system waveforms. cWB is sensitive to binaries of any eccentricity, and in particular to high-mass black holes. The search has been carried out over data from Advanced LIGO and Advanced Virgo's O1 and O2 observing runs, and found no evidence of eccentric binary signals. This paper evaluates the sensitivity of cWB to eccentric binary mergers, and infers constraints from non-detection on the rate of eccentric mergers.

## 2. Detectors and Analysis Method

### 2.1. Advanced LIGO and Advanced Virgo

The Advanced LIGO detectors began their first observing run O1 on 2015 September 12, which lasted until 2016 January 19 (Abbott et al. 2016b). During this time they accumulated $T_{\text{obs},1} = 48$ days of coincident data during which both the LIGO Hanford and LIGO Livingston detectors were operating. The second observing run O2 started on 2016 November 30 and lasted until 2017 August 25, resulting in $T_{\text{obs},2} = 118$ days of coincident data (Abbott et al. 2019e). Advanced Virgo joined the Advanced LIGO detectors on 2017 August 1. The detectors' sensitivity was not uniform during these runs, and there was a marked sensitivity increase from O1 to O2 (Abbott et al. 2018). As adding Advanced Virgo data was not improving the sensitivity of the search, this analysis only uses data from the Advanced LIGO detectors.

### 2.2. Search Description

The search for eccentric BBH mergers uses the same configuration of the cWB pipeline (Klimenko et al. 2008, 2016)

as the BBH merger search reported in Abbott et al. (2019e). An early version of the search is described in Tiwari et al. (2016). cWB is designed to search for transient signals, without specifying a waveform model. It identifies coherent excess power in multi-resolution time-frequency representations of the detectors' strain data, for signal frequencies up to 1 kHz and duration up to a few seconds. The excess power is collected in the time-frequency plane assuming monotonically increasing frequency for better collection of the signal energy from BBHs. The search identifies events that are coherent in multiple detectors and reconstructs the source sky location and signal waveforms using the constrained maximum likelihood method.

The cWB detection statistic $\rho$ is based on the coherent energy $E_c$ obtained by cross-correlating the signal waveforms reconstructed in the network of detectors. It is proportional to the coherent network signal-to-noise ratio. The estimation of statistical significance of an event is done by ranking the $\rho$ of the event against the $\rho$ distribution for background events obtained by repeating the analysis on time-shifted data. To exclude astrophysical events from the background sample, the time shifts are much larger than the expected signal delay between the detectors. Each cWB event was assigned a False Alarm Rate based on the rate of background triggers with a $\rho$ higher than that of the event.

To increase the robustness against non-stationary detector noise-generating glitches, cWB uses signal-independent vetoes: the network correlation $c_c = E_c/(E_c + E_n)$, where $E_n$ is the residual noise energy estimated after the reconstructed signal pixels are subtracted from the data. For a gravitational-wave signal we expected $c_c \approx 1$, while for glitches $c_c \ll 1$. Events with $c_c < 0.7$ are rejected.

Detector characterization studies are also carried out to ensure that candidate events are not due to instrumental or environmental artifacts. We have rejected the times where significant instrumental artifacts make the data unusable (Abbott et al. 2016c).

### 2.3. Simulated Astrophysical Signals

In order to estimate the sensitivity of our search, we simulated eccentric BBH signals, injected them into detector data and searched for them using cWB. We used a BH mass range of $5 M_{\odot} - 50 M_{\odot}$ (Abbott et al. 2019d), and eccentricities in the $e \in [0, 0.99]$ range. We assumed that BHs have zero spin. These simulations were carried out to quantify the search sensitivity for individual binaries. Below we considered different mass distributions to characterize our sensitivity.

At the time of the analysis only one set of templates was available for the generation of full inspiral-merger-ringdown eccentric binary waveforms, including generic spin configurations by East et al. (2013). It uses a prescription based on the equations of motion of a geodesic in a Kerr spacetime, coupled with the quadrupole formula for the gravitational radiation. The model defines an effective Kerr spacetime whose mass and spin parameters are set equal to the total mass and orbital angular momentum of the binary. The binary is evolved based on the behavior of a timelike geodesic in the effective Kerr spacetime, but the mass and angular momentum of this spacetime are changed at each time step based on the emitted energy and angular momentum calculated in the quadrupole approximation. This approach reproduces the correct orbital dynamics in the Newtonian limit and general-relativistic test particle limit. This model also incorporates strong-field features such as
<figure><img src="image_4.png" /><figcaption>**Figure 1.** Examples of gravitational waveforms for a 10 $M_{\odot}$–10 $M_{\odot}$ BBH system with eccentricities 0 (black) and 0.5 (red).</figcaption></figure>

pericenter precession, frame dragging, and the existence of unstable orbits and related zoom-whirl dynamics (East et al. 2013). The inspiral waveforms obtained using the above treatment are stitched to a merger model that was developed for quasicircular mergers but also performs well for eccentric mergers with little modification (Baker et al. 2008; Kelly et al. 2011). In Figure 1 we show this waveform for the case of circular and eccentric ($e = 0.5$) orbits.

The waveforms we used here to simulate gravitational waves from eccentric binaries are approximate. Compared to gravitational waveforms obtained using general-relativistic numerical simulations, the waveforms differ in overlap by up to a few percent (East et al. 2013). However, we found that cWB can detect the waveforms used here with equal sensitivity to precise waveforms obtained using numerical simulations, making their use appropriate to characterize search sensitivity. This is due to the fact that cWB does not rely on the precise gravitational waveform, making a few percent difference negligible.

## 3. Results

This search has detected 7 of the 10 BBH events that were identified by template-based searches (its sensitivity compared to template-based searches is higher for higher-mass binaries; see Table 1 in Abbott et al. 2019e). We considered these events to have no eccentricity. Our search did not detect any gravitational-wave event beyond these. Therefore, we concluded that no eccentric BBH merger has been detected. Below we present our search sensitivity to interpret this non-detection.

We note that the detection of only 7 out of 10 BBH events by cWB is consistent with its relative sensitivity compared to template-based searches, which are more sensitive in particular at low black hole masses (see Figure 2). Our interpretation below does not depend on or make use of this fractional overlap between the two search types.

We further note that the detection by cWB and the less-confident template-based detection of an event would not necessarily mean that the event was an eccentric binary (see, e.g., Abbott et al. 2019e). The eccentricity of a detected event would need to be independently measured (e.g., Lower et al. 2018).

### 3.1. Sensitivity to Eccentric Mergers

We characterized the sensitivity of our search by calculating its range—the distance, averaged over observation time, sky location, and orientation, within which a BBH can be detected with false alarm rate $\le 10^{-2}$ yr$^{-1}$. For this calculation we

<figure><img src="image_5.png" /><figcaption>**Figure 2.** Range of the cWB analysis to BBH mergers as a function of the binary's chirp mass, separately for the O1 and O2 observing runs, and for different orbital eccentricities (see the legend). The shaded regions represent $1\sigma$ uncertainties. The dotted lines are linear fits on the ranges at chirp masses $>30 M_{\odot}$ for $e = 0$. For comparison, we show the sensitive ranges for template-based searches for compact binary coalescence (CBC), assuming $e = 0$, for O1 and O2 (Abbott et al. 2018). Masses are given in source frame.</figcaption></figure>

adopted a standard cosmological model with Hubble parameter $H_0 = 67.9$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_M = 0.3065$ (Ade et al. 2016). The range depends on the black hole masses, and is different for the O1 and O2 observing runs. In particular it depends on the chirp mass $M$ of the binary, where $M \equiv (m_1m_2)^{3/5}(m_1 + m_2)^{-1/5}$ for black hole masses $m_1$ and $m_2$. We find that cWB range is independent of the eccentricity for the whole mass range considered (see also Tiwari et al. 2016). Our ranges, using the eccentric waveforms described in Section 2.3, are shown in Figure 2. We additionally see that the sensitive range of cWB grows faster with chirp mass than the range of template-based searches, making cWB additionally useful for circular binaries at higher masses (see also Abbott et al. 2017b).

### 3.2. Astrophysical Constraints

In order to compare our results to astrophysical source populations, we calculated the volume-time (VT) probed by our search. VT depends on the mass distribution of the BBH population. Dynamical formation channels are expected to
result in different BH mass and mass ratio distributions than BBH mergers from field binaries (Kimpson et al. 2016; Rodriguez et al. 2018). We considered a BBH mass distribution such that the mass of the more massive BH, $m_1$, follows a power-law distribution $m^{-\beta}$ within the range $[5 M_\odot, 50 M_\odot]$ for different $\beta$ values (see below), while the second BH's mass, $m_2$ is uniformly distributed within the range $[5 M_\odot, m_1]$. The mass distribution of BBH mergers detected by Advanced LIGO and Advanced Virgo so far is somewhat different from this assumed distribution (Abbott et al. 2019d, 2019e). However, eccentric BBH merger channels are likely responsible for only a subset of these observations and therefore they do not fully determine the overall spectrum. With this mass distribution model, we find that $VT(\beta) \approx \{6.6, 2.4, 0.75\} \times 10^{-2} \text{Gpc}^3 \text{yr}$ for $\beta = \{1, 2, 3\}$, respectively.

The BBH merger rate density for processes that can lead to eccentric orbits in the Advanced LIGO and Advanced Virgo band is mostly predicted to be up to a few $\text{Gpc}^{-3} \text{yr}^{-1}$ (Kocsis et al. 2006; Antonini & Rasio 2016; Rodriguez et al. 2016b; Bartos et al. 2017; Petrovich & Antonini 2017; Silsbee & Tremaine 2017; Hamers et al. 2018; Hoang et al. 2018; Yang et al. 2019), while some more extreme models predict merger rate densities up to $100 \text{Gpc}^{-3} \text{yr}^{-1}$ (Rasskazov & Kocsis 2019; VanLandingham et al. 2016). The fraction of mergers from these processes that have high eccentricity ($e \gtrsim 0.1$) ranges from ~1% (Randall & Xianyu 2018a, 2018b) to close to all mergers (Petrovich & Antonini 2017; Gondán et al. 2018).

In order to understand the astrophysical rate density constraints of our results, we considered a dynamical formation channel that produces BBH mergers at rate density $R_{dyn}$, with a mass power-law index $\beta$ (see above). We assumed that a fraction $f_{ecc}$ of mergers from this channel have eccentricities $e > 0.1$, and that this BBH sub-population follows the mass distribution considered here. We further assumed that all BBH mergers detected by Advanced LIGO and Advanced Virgo so far have eccentricities $e < 0.1$. The expected number of eccentric mergers ($e > 0.1$) from this model detected by cWB during O1 and O2 is then

$$ \langle N_{cWB, ecc} \rangle = R_{dyn} f_{ecc} VT(\beta). \quad (1) $$

Given that no such eccentric merger was detected, the Neyman 90% confidence-level upper limit is

$$ R_{ul, ecc} = \frac{2.3}{f_{ecc}VT(\beta)} \quad (2) $$

where $\beta = \{1, 2, 3\}$. We obtained

$$ R_{ul, ecc} = \{30, 90, 300\} f_{ecc}^{-1} \text{Gpc}^{-3} \text{yr}^{-1} \quad (3) $$

for $\beta = \{1, 2, 3\}$, respectively. The quoted approximate values were rounded to the first significant digit. We found that this result does not depend on the eccentricity distribution of the source population, as our search sensitivity only weakly depends on eccentricity.

Our results rule out models predicting $\gtrsim 100 \text{Gpc}^{-3} \text{yr}^{-1}$ merger rate densities (VanLandingham et al. 2016; Rasskazov & Kocsis 2019) for $\beta \lesssim 2$ if the majority of mergers in the given model have eccentricities $e > 0.1$, while the results are consistent with a number of other models (e.g., Antonini & Perets 2012; Antonini et al. 2017; Fragione et al. 2019b).

## 4. Conclusion

We searched for eccentric BBH mergers using the cWB algorithm. We showed that the sensitivity of our method is independent of the eccentricity at the time the binary enters Advanced LIGO and Advanced Virgo's frequency band at ~10 Hz.

Our search only uncovered binaries that have also been found by template-based searches that do not appear to have eccentric orbits. We interpreted this non-detection in light of the expected merger rate density of BBH formation channels that can produce eccentric orbits, and the fraction of these mergers that have eccentricities $\gtrsim 0.1$. Our results rule out the highest end of the rate density predictions ($\gtrsim 100 \text{Gpc}^{-3} \text{yr}^{-1}$) assuming that the majority of the binaries from these channels have $e > 0.1$, and that the power-law index of the BH mass spectrum is $\lesssim 2$.

Future observing runs by Advanced LIGO, Advanced Virgo and KAGRA (Aso et al. 2013) will provide substantially improved sensitivity to probe formation mechanisms resulting in eccentric binaries (Abbott et al. 2018).

The authors gratefully acknowledge the support of the United States National Science Foundation (NSF) for the construction and operation of the LIGO Laboratory and Advanced LIGO, as well as the Science and Technology Facilities Council (STFC) of the United Kingdom, the Max-Planck-Society (MPS), and the State of Niedersachsen/Germany for support of the construction of Advanced LIGO and construction and operation of the GEO600 detector. Additional support for Advanced LIGO was provided by the Australian Research Council. The authors gratefully acknowledge the Italian Istituto Nazionale di Fisica Nucleare (INFN), the French Centre National de la Recherche Scientifique (CNRS) and the Foundation for Fundamental Research on Matter supported by the Netherlands Organisation for Scientific Research, for the construction and operation of the Virgo detector and the creation and support of the EGO consortium. The authors also gratefully acknowledge research support from these agencies as well as by the Council of Scientific and Industrial Research of India, the Department of Science and Technology, India, the Science & Engineering Research Board (SERB), India, the Ministry of Human Resource Development, India, the Spanish Agencia Estatal de Investigación, the Vicepresidència i Conselleria d'Innovació Recerca i Turisme and the Conselleria d'Educació i Universitat del Govern de les Illes Balears, the Conselleria d'Educació Investigació Cultura i Esport de la Generalitat Valenciana, the National Science Centre of Poland, the Swiss National Science Foundation (SNSF), the Russian Foundation for Basic Research, the Russian Science Foundation, the European Commission, the European Regional Development Funds (ERDF), the Royal Society, the Scottish Funding Council, the Scottish Universities Physics Alliance, the Hungarian Scientific Research Fund (OTKA), the Lyon Institute of Origins (LIO), the Paris Île-de-France Region, the National Research, Development and Innovation Office Hungary (NKFIH), the National Research Foundation of Korea, Industry Canada and the Province of Ontario through the Ministry of Economic Development and Innovation, the Natural Science and Engineering Research Council Canada, the Canadian Institute for Advanced Research, the Brazilian Ministry of Science, Technology, Innovations, and Communications, the International Center for
Theoretical Physics South American Institute for Fundamental Research (ICTP-SAIFR), the Research Grants Council of Hong Kong, the National Natural Science Foundation of China (NSFC), the Leverhulme Trust, the Research Corporation, the Ministry of Science and Technology (MOST), Taiwan and the Kavli Foundation. The authors gratefully acknowledge the support of the NSF, STFC, MPS, INFN, CNRS, and the State of Niedersachsen/Germany for provision of computational resources.

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