Zeki Eker

A catalogue of chromospherically active binary stars (third edition)

The catalogue of chromospherically active binaries (CABs) has been revised and updated. With 203 new identifications, the number of CAB stars is increased to 409. The catalogue is available in electronic format where each system has a number of lines (suborders) with a unique order number. The columns contain data of limited numbers of selected cross references, comments to explain peculiarities and the position of the binarity in case it belongs to a multiple system, classical identifications (RS Canum Venaticorum, BY Draconis), brightness and colours, photometric and spectroscopic data, a description of emission features (Ca II H and K, Hα, ultraviolet, infrared), X-ray luminosity, radio flux, physical quantities and orbital information, where each basic entry is referenced so users can go to the original sources.

Dynamical evolution of active detached binaries on the log Jo–log M diagram and contact binary formation

Orbital angular momentum (OAM, J o ), 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 J o -logP, logM-logP and log J o -log M were formed from 119 CAB and 102 W UMa stars. The log J o -log M diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the log J o -log M diagram. Since the orbital size (a) and period (P) of binaries are determined by their current J o , M and mass ratio, q, the rates of OAM loss (d log J o /dt) and mass loss (d log M/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a eontact system if its own dynamical evolution enables it to pass the contact border on the log J o -log M diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of Jo and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6 Gyr, respectively.

Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution

The kinematics of 237 chromospherically active binaries (CABs) were studied. The sample is heterogeneous with different orbits and physically different components from F to M spectral-type main-sequence stars to G and K giants and supergiants. The computed U, V, W space velocities indicate that the sample is also heterogeneous in velocity space. That is, both kinematically younger and older systems exist among the non-evolved main sequence and the evolved binaries containing giants and subgiants. The kinematically young (0.95 Gyr) subsample (N = 95), which is formed according to the kinematical criteria of moving groups, was compared with the rest (N = 142) of the sample (3.86 Gyr) to investigate any observational clues of binary evolution. Comparing the orbital period histograms between the younger and older subsamples, evidence was found supporting the finding of Demircan that the CABs lose mass (and angular momentum) and evolve towards shorter orbital periods. The evidence of mass loss is noticeable on the histograms of the total mass (M h + M c ), which is compared between the younger (only N = 53 systems available) and older subsamples (only N = 66 systems available). The orbital period decrease during binary evolution is found to be clearly indicated by the kinematical ages of 6.69, 5.19 and 3.02 Gyr which were found in the subsamples according to the period ranges of log P ≤ 0.8, 0.8 < log P ≤ 1.7 and 1.7 < log P ≤ 3, respectively, among the binaries in the older subsample.

Mass loss and orbital period decrease in detached chromospherically active binaries

The secular evolution of the orbital angular momentum (OAM), the systemic mass (M = M1+M2) and the orbital period of 114 chromospherically active binaries (CABs) were investigated after determining the kinematical ages of the sub-samples which were set according to OAM bins. OAMs, systemic masses and orbital periods were shown to be decreasing by the kinematical ages. The first order decreasing rates of OAM, systemic mass and orbital period have been determined as u J = 3.48× 10 10 yr 1 per systemic OAM, u M = 1.30× 10 10 yr 1 per systemic mass and u P = 3.96 × 10 10 yr 1 per orbital period respectively from the kinematical ages. The ratio of dlog J/dlog M = 2.68, which were derived from the kinematics of the present sample, implies that there must be a mechanism which amplifies the angular momentum loss ¯ A = 2.68 times in comparison to isotropic angular momentum loss of hypothetical isotropic wind from the components. It has been shown that simple isotropic mass loss from the surface of a component or both components would increase the orbital period.

MAIN-SEQUENCE EFFECTIVE TEMPERATURES FROM A REVISED MASS–LUMINOSITY RELATION BASED ON ACCURATE PROPERTIES

The mass-luminosity (M-L), mass-radius (M-R) and mass-effective temperature (

Synthetic Light Curves of Spotted Stars: Unique or Not Unique?

M-T_{eff}

Reliability of Light Curves for Photometric Imaging

) diagrams for a subset of galactic nearby main-sequence stars with masses and radii accurate to

The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way

\leq 3\%

SDSS J162520.29+120308.7 – a new SU Ursae Majoris star in the period gap

and luminosities accurate to

Kinematics and age of RS Canum Venaticorum and BY Draconis stars

\leq 30\%