Observation of Gravitational Waves from Two Neutron Star-Black Hole Coalescences


R. Abbott, California Institute of Technology
T. D. Abbott, Louisiana State University
S. Abraham, Inter-University Centre for Astronomy and Astrophysics India
F. Acernese, Università degli Studi di Salerno
K. Ackley, Monash University
A. Adams, Christopher Newport University
C. Adams, LIGO Livingston
R. X. Adhikari, California Institute of Technology
V. B. Adya, The Australian National University
C. Affeldt, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
D. Agarwal, Inter-University Centre for Astronomy and Astrophysics India
M. Agathos, University of Cambridge
K. Agatsuma, University of Birmingham
N. Aggarwal, Northwestern University
O. D. Aguiar, Instituto Nacional de Pesquisas Espaciais
L. Aiello, Cardiff University
A. Ain, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
P. Ajith, Tata Institute of Fundamental Research, Mumbai
T. Akutsu, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
K. M. Aleman, California State University, Fullerton
G. Allen, University of Illinois Urbana-Champaign
A. Allocca, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
P. A. Altin, The Australian National University
A. Amato, Université Claude Bernard Lyon 1
S. Anand, California Institute of Technology
A. Ananyeva, California Institute of Technology
S. B. Anderson, California Institute of Technology
W. G. Anderson, University of Wisconsin-Milwaukee
M. Ando, The University of Tokyo
S. V. Angelova, University of Strathclyde
S. Ansoldi, Università degli Studi di Udine
J. M. Antelis, Embry-Riddle Aeronautical University, Prescott
S. Antier, Université de Paris

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We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star-black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO-Virgo detectors. The source of GW200105 has component masses, whereas the source of GW200115 has component masses and (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%-96% and 87%-98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are and, respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of when assuming that GW200105 and GW200115 are representative of the NSBH population or under the assumption of a broader distribution of component masses.

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Astrophysical Journal Letters

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