Angular momentum loss by a star that belongs to a close binary system and has a rapidly rotating core

Astrophysics ◽  
1978 ◽  
Vol 14 (2) ◽  
pp. 122-127
Author(s):  
V. G. Gorbatskii
Keyword(s):  
Angular Momentum ◽  
Binary System ◽  
Close Binary System ◽  
Close Binary ◽  
Momentum Loss ◽  
Angular Momentum Loss

scholarly journals Aspects of Mass Loss and Angular Momentum Loss in Binaries Containing Cool Components

1992 ◽  
Vol 151 ◽  
pp. 167-173
Author(s):  
Peter P. Eggleton
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Orbital Angular Momentum ◽  
Cataclysmic Variables ◽  
Close Binary ◽  
Rapid Rotation ◽  
Momentum Loss ◽  
Cool Stars ◽  
Angular Momentum Loss ◽  
Show Evidence

Cool stars show evidence of dynamo activity which is stronger with more rapid rotation. Tidal friction in a moderately close binary can be a cause of relatively rapid rotation, so that cool components in such binaries are presumably liable to stronger stellar winds than single cool stars. As a consequence, the binary can be subject to orbital angular momentum loss. Both the mass loss and the orbital angular momentum loss can be on a timescale comparable to nuclear evolution in a red subgiant, or even faster. RS CVn stars probably give the best possibility of measuring these processes, although some observational data are difficult to reconcile with simple theories.Barium stars, and symbiotics, may both be affected by these processes. They must be the products of evolution of moderately wide binaries, as must such objects as cataclysmic variables. I attempt to define the ranges of zero-age parameters necessary to produce such varied objects. A simplistic model of the distribution of stars brighter than 6th magnitude (a ‘Theoretical Bright Star Catalogue’) suggests that for every three Ba stars with a measurable orbit, there should be one main sequence ‘Ba star’.

scholarly journals Close binary evolution

2017 ◽  
Vol 609 ◽  
pp. A3 ◽  
Author(s):  
H. F. Song ◽  
G. Meynet ◽  
A. Maeder ◽  
S. Ekström ◽  
P. Eggenberger ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Binary System ◽  
Magnetic Fields ◽  
Close Binary System ◽  
Momentum Transport ◽  
Close Binary ◽  
Surface Magnetic Field ◽  
Angular Momentum Transport ◽  
Magnetic Braking

Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims. We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods. We discuss the evolution of a 10 M⊙ star in a close binary system with a 7 M⊙ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M⊙ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results. We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This “equilibrium angular velocity” is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The treatment of the internal angular momentum transport has a strong impact on the evolutionary tracks in the Hertzsprung-Russell Diagram as well as on the changes of the surface abundances resulting from rotational mixing. Our modelling suggests that the presence of an undetected close companion might explain rapidly rotating stars with strong surface magnetic fields, having ages well above the magnetic braking timescale. Our models predict that the rotation of most stars of this type increases as a function of time, except for a first initial phase in spin-down systems. The measure of their surface abundances, together, when possible, with their mass-luminosity ratio, provide interesting constraints on the transport efficiencies of angular momentum and chemical species. Conclusions. Close binaries, when studied at phases predating any mass transfer, are key objects to probe the physics of rotation and magnetic fields in stars.

Gravitational Radiation and the Evolution of Low Mass Binaries

1976 ◽  
Vol 73 ◽  
pp. 193-204 ◽  
Author(s):  
John Faulkner
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Binary System ◽  
Observational Study ◽  
Gravitational Radiation ◽  
Region Of Interest ◽  
Close Binary System ◽  
Close Binary ◽  
Theoretical Studies ◽  
Low Mass

Gravitational radiation of energy and angular momentum can modify and in some cases, control the evolution of a close binary system. The region of interest is briefly delineated. Recent work of the author and colleagues of relevance to this area is discussed, including theoretical studies of accretion, mass loss and mass transfer, and an observational study of a system, HZ 29 where gravitational radiation may dictate its behaviour.

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