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Abstract The formation histories of compact binary mergers, especially stellar-mass binary black hole mergers, have recently come under increased scrutiny and revision. We revisit the question of the dominant formation channel and efficiency of forming binary neutron star (BNS) mergers. We use the stellar and binary evolution codeMESAand implement a detailed method for common envelope and mass transfer. We perform simulations for donor masses between 7 M⊙and 20 M⊙with a neutron star (NS) companion of 1.4 M⊙and 2.0 M⊙ at two metallicities, using varying common envelope efficiencies and two different prescriptions to determine if the donor undergoes core collapse or electron capture, given their helium and carbon–oxygen cores. In contrast to the case of binary black hole mergers, for an NS companion of 1.4 M⊙, all BNS mergers are formed following a common envelope phase. For an NS mass of 2.0 M⊙, we identify a small subset of mergers following only stable mass transfer if the NS receives a natal kick sampled from a Maxwellian distribution with velocity dispersionσ= 265 km s−1. Regardless of the supernova prescription, we find more BNS mergers at subsolar metallicity compared to solar.
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The Redshift Evolution of the Binary Black Hole Merger Rate: A Weighty Matter
Abstract Gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (BBH) merger rate,RBBH(z). We make predictions forRBBH(z) as a function of black hole mass for systems originating from isolated binaries. To this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations,COMPAS. We distinguish two channels: the common envelope (CE), and the stable Roche-lobe overflow (RLOF) channel, characterized by whether the system has experienced a common envelope or not. We find that the CE channel preferentially produces BHs with masses below about 30M⊙and short delay times (tdelay≲ 1 Gyr), while the stable RLOF channel primarily forms systems with BH masses above 30M⊙and long delay times (tdelay≳ 1 Gyr). We provide a new fit for the metallicity-dependent specific star formation rate density based on the Illustris TNG simulations, and use this to convert the delay time distributions into a prediction ofRBBH(z). This leads to a distinct redshift evolution ofRBBH(z) for high and low primary BH masses. We furthermore find that, at high redshift,RBBH(z) is dominated by the CE channel, while at low redshift, it contains a large contribution (∼40%) from the stable RLOF channel. Our results predict that, for increasing redshifts, BBHs with component masses above 30M⊙will become increasingly scarce relative to less massive BBH systems. Evidence of this distinct evolution ofRBBH(z) for different BH masses can be tested with future detectors.
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- Award ID(s):
- 2009131
- PAR ID:
- 10367221
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 931
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 17
- Size(s):
- Article No. 17
- Sponsoring Org:
- National Science Foundation
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