TY - JOUR

T1 - The origin of spin in binary black holes

T2 - Predicting the distributions of the main observables of Advanced LIGO

AU - Bavera, Simone S.

AU - Fragos, Tassos

AU - Qin, Ying

AU - Zapartas, Emmanouil

AU - Neijssel, Coenraad J.

AU - Mandel, Ilya

AU - Batta, Aldo

AU - Gaebel, Sebastian M.

AU - Kimball, Chase

AU - Stevenson, Simon

PY - 2020/3/16

Y1 - 2020/3/16

N2 - Context. After years of scientific progress, the origin of stellar binary black holes is still a great mystery. Several formation channels for merging black holes have been proposed in the literature. As more merger detections are expected with future gravitational-wave observations, population synthesis studies can help to distinguish between them.Aims. We study the formation of coalescing binary black holes via the evolution of isolated field binaries that go through the common envelope phase in order to obtain the combined distributions of observables such as black-hole spins, masses and cosmological redshifts of mergers.Methods. To achieve this aim, we used a hybrid technique that combines the parametric binary population synthesis code COMPAS with detailed binary evolution simulations performed with the MESA code. We then convolved our binary evolution calculations with the redshift- and metallicity-dependent star-formation rate and the selection effects of gravitational-wave detectors to obtain predictions of observable properties.Results. By assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the following three main gravitational-wave observables: the effective inspiral spin parameter chi (eff), the chirp mass M-chirp and the cosmological redshift of merger z(merger). We find an excellent agreement between our model and the ten events from the first two advanced detector observing runs. We make predictions for the third observing run O3 and for Advanced LIGO design sensitivity. We expect approximately 80% of events with chi (eff)<0.1, while the remaining 20% of events with (eff)>= 0.1 are split into similar to 10% with M-chirp<15 M- and similar to 10% with M-chirp >= 15 M-circle dot. Moreover, we find that M-chirp and chi (eff) distributions are very weakly dependent on the detector sensitivity.Conclusions. The favorable comparison of the existing LIGO/Virgo observations with our model predictions gives support to the idea that the majority, if not all of the observed mergers, originate from the evolution of isolated binaries. The first-born black hole has negligible spin because it lost its envelope after it expanded to become a giant star, while the spin of the second-born black hole is determined by the tidal spin up of its naked helium star progenitor by the first-born black hole companion after the binary finished the common-envelope phase.

AB - Context. After years of scientific progress, the origin of stellar binary black holes is still a great mystery. Several formation channels for merging black holes have been proposed in the literature. As more merger detections are expected with future gravitational-wave observations, population synthesis studies can help to distinguish between them.Aims. We study the formation of coalescing binary black holes via the evolution of isolated field binaries that go through the common envelope phase in order to obtain the combined distributions of observables such as black-hole spins, masses and cosmological redshifts of mergers.Methods. To achieve this aim, we used a hybrid technique that combines the parametric binary population synthesis code COMPAS with detailed binary evolution simulations performed with the MESA code. We then convolved our binary evolution calculations with the redshift- and metallicity-dependent star-formation rate and the selection effects of gravitational-wave detectors to obtain predictions of observable properties.Results. By assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the following three main gravitational-wave observables: the effective inspiral spin parameter chi (eff), the chirp mass M-chirp and the cosmological redshift of merger z(merger). We find an excellent agreement between our model and the ten events from the first two advanced detector observing runs. We make predictions for the third observing run O3 and for Advanced LIGO design sensitivity. We expect approximately 80% of events with chi (eff)<0.1, while the remaining 20% of events with (eff)>= 0.1 are split into similar to 10% with M-chirp<15 M- and similar to 10% with M-chirp >= 15 M-circle dot. Moreover, we find that M-chirp and chi (eff) distributions are very weakly dependent on the detector sensitivity.Conclusions. The favorable comparison of the existing LIGO/Virgo observations with our model predictions gives support to the idea that the majority, if not all of the observed mergers, originate from the evolution of isolated binaries. The first-born black hole has negligible spin because it lost its envelope after it expanded to become a giant star, while the spin of the second-born black hole is determined by the tidal spin up of its naked helium star progenitor by the first-born black hole companion after the binary finished the common-envelope phase.

KW - stars: black holes

KW - gravitational waves

KW - binaries close

KW - black hole physics

KW - HUBBLE FRONTIER FIELDS

KW - ROTATING MASSIVE STARS

KW - COMMON ENVELOPE

KW - STELLAR EVOLUTION

KW - GRAVITATIONAL-RADIATION

KW - PRESUPERNOVA EVOLUTION

KW - DIFFERENTIAL ROTATION

KW - LUMINOSITY FUNCTION

KW - NEUTRON-STAR

KW - MERGER RATE

U2 - 10.1051/0004-6361/201936204

DO - 10.1051/0004-6361/201936204

M3 - Journal article

VL - 635

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A97

ER -