E. Sipahi

T-Cyg1-12664: a low-mass chromospherically active eclipsing binary in the Kepler field

The eclipsing binary T-Cyg1-12664 has been observed both spectroscopically and photo- metrically, and the radial velocities of both the components and the ground-based VRI light curves have been obtained. The Kepler R data and radial velocities for the system have been analysed simultaneously. Masses and radii have been obtained as 0.680 ± 0.021 Mand 0.613 ± 0.007 Rfor the primary star and 0.341 ± 0.012 Mand 0.897 ± 0.012 Rfor the secondary star. The distance to the system has been estimated as 127 ± 14 pc. The ob- served wave-like distortion at out-of-eclipse is modelled with two separate spots on the more massive star, which is also confirmed by the Ca II K and H emission lines in its spectra. The locations of the components in the mass-radius and mass-effective temperature planes have been compared with the well-determined low-mass components of eclipsing binaries as well as with the theoretical models. While the radius of the primary star is consistent with the main-sequence stars, the radius of the less massive component appears to be 2.8 times larger than that of the main-sequence models. A comparison of the radii of low-mass stars with the models reveals that the observationally determined radii begin to deviate from the models with a mass of 0.27 M� , and suddenly reach to maximum deviation at a mass of 0.34 M� . Then, the deviations begin to decrease up to the solar mass. The maximum deviation, seen at a mass of about 0.34 M� , is very close to the mass of fully convective stars, as suggested by theoretical studies. A third star in the direction of the eclipsing pair has been detected from our VRI images. The observed infrared excess of the binary most probably arises from this star, which can be radiated mostly in the infrared bands.

MY Serpentis: a high-mass triple system in the Ser OB2 association

We present spectroscopic observations of the massive multiple system HD,167971, located in the open cluster NGC,6604. The brighter component of the triple system is the overcontact eclipsing binary MY,Ser with an orbital period of 3.32,days. The radial velocities and the previously published UBV data obtained by citet{may10} and the UBVRI light curves by citet{dav88} are analysed for the physical properties of the components. We determine the following absolute parameters: for the primary star M

Absolute parameters of the eclipsing binary V821 Cas from UBVRI light curves and radial velocities

_p

TYC 1031 1262 1: an anomalous Cepheid in a double-lined eclipsing binary★

=32.23

Spectroscopic observations of the interacting massive binary AQ Cassiopea

pm

Analysis of the massive eclipsing binary V1441Aql

0.54 M

The mass and radius of the M-dwarf companion in the double-lined eclipsing binary T-Cyg1-01385

_{odot}

Spectroscopic and photometric observations of the selected Algol-type binaries -II. V2080 Cygni and V2365 Ophiuchi

, R

Spectroscopic and photometric observations of the selected Algol-type binaries* -IV. V799 Cassiopeiae, BX Piscium and HD 172189

_p

Spectroscopic and photometric observations of selected Algol‐type binaries – I. V1665 Aquilae and AG Arietis

=14.23