Interacting binary star
Interacting binary stars are binary stars, which show a significant interaction between its components, beyond the influence of their mutual gravitational forces. The interference can take place through mass exchange between the stars, by the action of electromagnetic or particle radiation or by tidal forces. The interaction between the stars, the stars can follow development paths, they can not run as a single star. Interacting binary stars are somewhat imprecisely referred to as a close binary stars.
Interaction by mass exchange
Mass transfer between the components of a binary star can be done by stellar wind or by exceeding the Roche limit. In a Windakkretion a wind flowing from a massive star and is directed by the gravitational field of the companion on these. For reasons of conservation of angular momentum forms around the mass receiving star an accretion disk from which the matter falling onto the star. The accretion rates are usually too small to influence the development paths of the stars, but many eruptions of variable stars are caused by the Windakkretion. In the collisions of stellar winds in close binary stars can accelerate particles to extremely high energies and are observed as gamma-ray binaries.
Exceeding a Roche limit of the star has reached an extent in the double star, with parts of its atmosphere are no longer gravitationally bound to the star. This can leave the binary system or usually pass through a accretion disk to the pet. The mass transfer results in a change of the path axis, changing the mass of the components and changed rotational periods of the components. The transfer of matter, the chemical signature may change in the atmospheres of stars like the barium stars or the stars can follow development paths, which they would not be able to achieve as a single star in an undisturbed development. As an example, the blue sub- dwarfs, blue stragglers and a part of the thermonuclear supernovae of type Ia apply.
The interacting binary systems with active mass transfer between the components include:
- Algolsterne
- Beta Lyrae stars
- Double Periodic Variable
- Cataclysmic variables
- X-ray binaries
- Symbiotic stars
- Colliding - Wind Binary
Interaction by tidal forces
The tidal forces deform the star and influence the light curve of the binary system, showing the signs of an ellipsoidal light variation. In addition, the tidal forces also lead to a synchronization of the rotational period of the star with the web orbital period of the binary system. Older stars in close binary systems therefore rotate much faster than single stars with corresponding age and because the rotation of the cause of magnetic activity in the chromosphere of these stars is show these stars in interacting binary systems pronounced signs of chromospheric activity in the form of star spots, coronal mass ejections, flares and radio bursts.
Many types of variable stars with magnetic activity therefore occur preferentially in interacting binary stars on how the UV Ceti stars, the BY Draconis stars and the RS Canum - Venaticorum stars.
The tidal locking in close binary systems also affects the mixing inside the star, and thus the composition of the space available in the core for thermonuclear reactions matter. This leads to an altered development path of the stars, regardless of mass transfer between the components.
Interaction with radiation
The heating of the companion side facing even the companion can be evaporated in extreme cases. This is the case where particles and electromagnetic radiation resolve the companion completely within a few million years ago when the Black Widows. The interaction of radiation has otherwise in double stars only influence on the light curve, showing a lighting effect, as the day side is brighter by the additional energy which keeps the star from its companion. The star responded with an expansion of its radius, which he in turn can exceed its Roche limit volume.
Interaction in a common sheath
All variants of the interaction are based on double stars with a common sheath for carrying. These include the W Ursae Majoris stars whose components are hidden under a common sheath with a uniform temperature. The common temperature measurement requires not yet fully understood energy transport in the atmosphere of the binary system. A Common Envelope is when a star enters the atmosphere of his companion. Depending on the mass ratio and the development status of the star can lead to different final results. If there is a merger of the two stars so the result is a Luminous Red Nova. If a neutron star merging with a star, the hypothetical result is a Thorne - Żytkow object.