Related papers: Formation and Evolution of W UMa Stars: Fallacies …
Recently, our understanding of the origin of W UMa-type contact binaries has become clearer. Initial masses of their components were successfully estimated by Y{\i}ld{\i}z and Do\u{g}an using a new method mainly based on observational…
Contact binary systems (also known as W UMa systems) consist of a pair of hydrogen-burning dwarf stars orbiting each other so closely that they share a common envelope. Although they are relatively common, there is as yet no established…
ASAS is a long term project to monitor bright variable stars over the whole sky. It has discovered 50,122 variables brighter than V < 14 mag south of declination +28 degrees, and among them 11,099 eclipsing binaries. We present a…
W UMi is a near contact, semi-detached, double-lined eclipsing binary star with an orbital period of 1.7 days. Simultaneous analysis of new BVR multi-color light curves and radial velocity data yields the main astrophysical parameters of…
The search-volume corrected period distribution of contact binaries of the W UMa type appears to reflect primarily the constant number ratio of ~1/500 to the number of stars along the Main Sequence; there exist no evidence for angular…
A new scenario for evolution of contact binaries is presented and discussed. Arguments are given that W UMa-type systems are formed from detached binaries which lose angular momentum via magnetized wind. This takes typically several Gyr.…
In a preceding paper, using Eggleton's evolution code we have discussed the structure and evolution of low-mass W UMa type contact binaries without angular momentum loss (AML). The models exhibit cyclic behavior about a state of marginal…
Various scenarios of contact binary evolution have been proposed in the past, giving hints of (sometimes contradictory) evolutionary sequence connecting A-type and W-type systems. As the components of close detached binaries approach each…
A set of 27 evolutionary models of cool close binaries was computed under the assumption that their evolution is influenced by the magnetized winds. Initial periods of 1.5, 2.0 and 2.5 d were considered. For each period three values of 1.3,…
Orbital angular momentum (Jo), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of log Jo - log P, log M - log P and log…
Close detached binaries were theoretically predicted to evolve into contact by three subtypes of case A binary evolution: case AD, AR, and AS, which correspond to the formation of contact during dynamic-, thermal-, and nuclear-timescale…
Eclipsing binary stars provide highly accurate measurements of the fundamental physical properties of stars. They therefore serve as stringent tests of the predictions of evolutionary models upon which most stellar age determinations are…
Despite being the most abundant (by space density) of interacting binary stars, W Ursae Majoris (W UMa) stars are not understood structurally. Their stellar components are in physical contact, and share a common convective envelope.…
The kinematics of 129 W UMa binaries is studied and its implications on the contact binary evolution is discussed. The sample is found to be heterogeneous in the velocity space that kinematically younger and older contact binaries exist in…
Results are presented on component masses and system angular momenta for over a hundred low-temperature contact binaries. It is found that the secondary components in close binary systems are very similar in mass. Our observational evidence…
The structure and evolution of low mass W UMa type contact binaries are discussed by employing Eggleton's stellar evolution code. Assuming that these systems completely satisfy Roche geometry, we calculate the relative radii of both…
W UMa type binaries have two defining characteristics. These are (i) the effective temperatures of both components are very similar, and (ii) the secondary (currently less massive) component is overluminous for its current mass. We consider…
In this study, all unpublished time series photometric data of BM UMa ($q \sim$ 2.0, P = 0.2712\,d) from available archives were re-investigated together with new data taken from the TNT-2.4m of the Thai National Observatory (TNO). Based on…
High resolution spectroscopic observations of AW UMa, obtained on three consecutive nights with the median time resolution of 2.1 minutes, have been analyzed using the Broadening Functions method in the spectral window Doppler images of the…
The luminosity function for contact binary stars of the W~UMa-type is evaluated on the basis of the ASAS photometric project covering all stars south of delta= +28 within a magnitude range 8<V<13. Lack of colour indices enforced a…