The origin of spin in binary black holes

Abstract

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 χeff, the chirp mass Mchirp and the cosmological redshift of merger zmerger. 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 χeff < 0.1, while the remaining 20% of events with χeff ≥ 0.1 are split into ∼10% with Mchirp < 15 M⊙ and ∼10% with Mchirp ≥ 15 M⊙. Moreover, we find that Mchirp and χeff 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.

GW190412: Observation of a binary-black-hole coalescence with asymmetric masses

“…Binary interactions following the formation of the first-born BH, such as mass transfer from the companion star to the BH, are also inefficient at spinning up BHs significantly [237][238][239][240][241]. On the other hand, the naked helium star precursor of the second-born BH in an isolated binary system can potentially be spun up through tidal interactions with the alreadyborn BH if the system is in a tight enough orbital configuration [234,[242][243][244][245][246]. Hence, there is a range of expectations for the spin magnitudes of both the primary and secondary components of BBHs formed in isolation.…”

Bayesian inference for compact binary coalescences with bilby: validation and application to the first LIGO–Virgo gravitational-wave transient catalogue

“…To extract information from the observed signals requires careful statistical inference. The inferred source parameters can inform our understanding of binary stellar evolution (Stevenson et al 2015;Abbott et al 2016d;Zevin et al 2017;Abbott et al 2017h; Barrett et al 2018;Belczynski et al 2018;Bavera et al 2020), the equation of state of neutron-star matter (Abbott et al 2018c;Most et al 2018;Essick et al 2020;Abbott et al 2020b), and the nature of gravity (Yunes & Siemens 2013;Abbott et al 2016b;Yunes et al 2016;Abbott et al 2019i;Isi et al 2019). Multimessenger observations of gravitational and electromagnetic radiation (Abbott et al 2017e) can give an even richer understanding, enabling measurements of cosmological parameters (Abbott et al 2017d(Abbott et al , 2019dCantiello et al 2018;Hotokezaka et al 2019;Dhawan et al 2020;Chen et al 2018), insights into the structures of gamma-ray bursts (Abbott et al 2017f;Mooley et al 2018;Margutti et al 2018;Fong et al 2019;Biscoveanu et al 2020b), and identifying the origins of heavy elements (Abbott et al 2017g;Chornock et al 2017;Tanvir et al 2017;Kasliwal et al 2019;Watson et al 2019).…”

Fingerprints of Binary Black Hole Formation Channels Encoded in the Mass and Spin of Merger Remnants

“…For instance, chirp masses can be used to constrain the global BH natal kick distribution (Zevin et al 2017; Barrett et al 2018), while their spin distribution can carry information on BH natal spins and BBH spin alignment in isolated (Gerosa et al 2018) and dynamical environments (Morawski et al 2018). As LIGO and Virgo reach full sensitivity and the number of detections increases, it will be possible to determine the most likely BH spin amplitude and the BBH spin orientation (Farr et al 2017;Stevenson et al 2017;Talbot & Thrane 2017;Arca Sedda & Benacquista 2019;Bouffanais et al 2019;Bavera et al 2020). Dissecting the formation history of BBHs from GW observations is a multifaceted problem that requires simultaneous accounting for single and binary stellar evolution, stellar dynamics, general relativity, and cosmology.…”