Stegmann, Jakob and Antonini, Fabio ![]() ![]() |
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Abstract
Close stellar binaries are prone to undergo a phase of stable mass transfer in which a star loses mass to its companion. Assuming that the donor star loses mass along the instantaneous interstellar axis, we derive the orbit-averaged equations of motion describing the evolution of the donor rotational angular momentum vector (spin) that accompanies the transfer of mass. We consider: (i) a model in which the mass transfer rate is constant within each orbit and (ii) a phase-dependent rate in which all mass per orbit is lost at periapsis. In both cases, we find that the ejection of ≳ 30 percent of the donor’s initial mass causes its spin to nearly flip onto the orbital plane of the binary, independently of the initial spin-orbit alignment. Moreover, we show that the spin flip due to mass transfer can easily dominate over tidal synchronization in any giant stars and main-sequence stars with masses ∼ 1.5 to 5 M ⊙ . Finally, the general equations of motion, including tides, are used to evolve a realistic population of massive binary stars, leading to the formation of binary black holes. Assuming that the stellar core and envelope are fully coupled, the resulting tilt of the first-born black hole reduces its spin projection onto the orbit normal by a factor ∼ O ( 0.1 ) . This result supports previous studies in favor of an insignificant contribution to the effective spin projection, χ eff , in binary black holes formed from the evolution of field binaries.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Advanced Research Computing @ Cardiff (ARCCA) Physics and Astronomy |
Publisher: | American Physical Society |
ISSN: | 2470-0010 |
Date of First Compliant Deposit: | 4 February 2021 |
Date of Acceptance: | 1 February 2021 |
Last Modified: | 18 Jun 2024 16:09 |
URI: | https://orca.cardiff.ac.uk/id/eprint/138273 |
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