Our understanding of the formation and evolution of binary black holes (BBHs) is significantly impacted by the recent discoveries made by the LIGO/Virgo collaboration. Of utmost importance is the detection of the most massive BBH system, GW190521. Here we investigate what it takes for field massive stellar binaries to account for the formation of such massive BBHs. Whether the high mass end of the BH mass function is populated by remnants of massive stars that either formed at extremely low metallicities and avoid the pairinstability mass gap or increase their birth mass beyond the pairinstability mass gap through the accretionmore »
Evolutionary roads leading to low effective spins, high black hole masses, and O1/O2 rates for LIGO/Virgo binary black holes
All ten LIGO/Virgo binary black hole (BHBH) coalescences reported following the O1/O2 runs have nearzero effective spins. There are only three potential explanations for this. If the BH spin magnitudes are large, then: (i) either both BH spin vectors must be nearly in the orbital plane or (ii) the spin angular momenta of the BHs must be oppositely directed and similar in magnitude. Then there is also the possibility that (iii) the BH spin magnitudes are small. We consider the third hypothesis within the framework of the classical isolated binary evolution scenario of the BHBH merger formation. We test three models of angular momentum transport in massive stars: a mildly efficient transport by meridional currents (as employed in the Geneva code), an efficient transport by the TaylerSpruit magnetic dynamo (as implemented in the MESA code), and a veryefficient transport (as proposed by Fuller et al.) to calculate natal BH spins. We allow for binary evolution to increase the BH spins through accretion and account for the potential spinup of stars through tidal interactions. Additionally, we update the calculations of the stellarorigin BH masses, including revisions to the history of star formation and to the chemical evolution across cosmic time. We more »
 Authors:
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 Publication Date:
 NSFPAR ID:
 10160687
 Journal Name:
 Astronomy & Astrophysics
 Volume:
 636
 Page Range or eLocationID:
 A104
 ISSN:
 00046361
 Sponsoring Org:
 National Science Foundation
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