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Paper: Tidal Flows from Asynchronous Rotation in Binaries
Volume: 425, Hot and Cool: Bridging Gaps in Massive Star Evolution
Page: 209
Authors: Koenigsberger, G.; Moreno, E.; Harrington, D. M.
Abstract: Asynchronous rotation in binary stars produces non-radial oscillations that are known to cause observable variability on orbital timescales. The horizontal perturbations of the surface velocity fields are referred to as “tidal flows.” In this paper we illustrate the manner in which tidal flows perturb the surface velocity field from that of uniform rotation, using a one-layer stellar model for the calculations. We justify the validity of this simplified model by the striking similarity between the photospheric absorption line-profiles it predicts and observational data of the binary system α Virginis. The velocity perturbations are used to compute the mechanical energy dissipation rates, E, due to the shearing flows for the case of a massive (50 + 28 Msun) binary system having a moderately eccentric (e = 0.3) orbit. The largest value of E around periastron phases is found on the hemisphere facing the companion. However, at other orbital phases the maximum E may migrate towards the poles. Assuming that E plays a role in the mass-loss characteristics of massive binary systems, this suggests that peculiar binaries such as HD 5980 and η Carinae may have a highly non-spherically symmetric mass-loss distribution which, in addition, is time-variable.
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