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 radi
al 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$_p$=32.23$pm$0.54 M$_{odot}$, R$_p$=14.23$pm$0.75 R$_{odot}$; and for the secondary star M$_s$=30.59$pm$0.53 M$_{odot}$, R$_s$=13.89$pm$0.75 R$_{odot}$. Photoelectric times of minimum light are analyzed under the consideration of the light-time orbit. The center-of-mass of the eclipsing binary is orbiting around the common center-of-gravity of the triple system with a period of 21.2$pm$0.7,yr and with a projected semi-major axis of 5.5$pm$0.7,AU. The mass function for the third star was calculated as 0.370$pm$0.036 M$_{odot}$. The light contributions of the third star to the triple system in the UBV pass-bands were derived and the intrinsic magnitudes and colors were calculated individually for the three stars. The components of the eclipsing pair were classified as O7.5 {sc iii} and O9.5 {sc iii}. The intrinsic color indices for the third star yield a spectral type of (O9.5-B0) {sc iii-i}. {bf This classification leads to constrain the inclination of the third-body orbit, which should be about 30$^{o}$, and therefore its mass should be about 29 M$_{odot}$. MY,Ser is one of the rare massive O-type triple system at a distance of 1.65$pm$0.13,kpc, the same as for the NGC,6604 embedded in the Ser,OB2 association.}
BVR light curves and radial velocities for the double-lined eclipsing binary V1135,Her were obtained. The brighter component of V1135,Her is a Cepheid variable with a pulsation period of 4.22433$pm$0.00026 days. The orbital period of the system is ab
out 39.99782$pm$0.00233 days, which is the shortest value among the known Type,II Cepheid binaries. The observed B, V, and R magnitudes were cleaned for the intrinsic variations of the primary star. The remaining light curves, consisting of eclipses and proximity effects, are obtained. Our analyses of the multi-colour light curves and radial velocities led to the determination of fundamental stellar properties of both components of the interesting system V1135,Her. The system consists of two evolved stars, G1+K3 between giants and supergiants, with masses of M$_1$=1.461$pm$0.054 Msun ~and M$_2$=0.504$pm$0.040 {Msun} and radii of R$_1$=27.1$pm$0.4 {Rsun} and R$_2$=10.4$pm$0.2 {Rsun}. The pulsating star is almost filling its corresponding Roche lobe which indicates the possibility of mass loss or transfer having taken place. We find an average distance of d=7500$pm$450 pc using the BVR magnitudes and also the V-band extinction. Location in the Galaxy and the distance to the galactic plane with an amount of 1300 pc indicate that it probably belongs to the thick-disk population. Most of the observed and calculated parameters of the V1135,Her and its location on the color-magnitude and period-luminosity diagrams lead to a classification of an Anomalous Cepheid.
The eclipsing binary T-Cyg1-12664 was observed both spectroscopically and photometrically. Radial velocities of both components and ground-based VRI light curves were obtained. The Keplers R-data and radial velocities for the system were analysed sim
ultaneously. Masses and radii were obtained as 0.680$pm$0.021 M$_{odot}$ and 0.613$pm$0.007 R$_{odot}$for the primary and 0.341$pm$0.012M$_{odot}$ and 0.897$pm$0.012R$_{odot}$ for the secondary star. The distance to the system was estimated as 127$pm$14 pc. The observed wave-like distortion at out-of-eclipse is modeled with two separate spots on the more massive star, which is also confirmed by the Ca {sc ii} K and H emission lines in its spectra. Locations of the components in the mass-radius and mass-effective temperature planes were compared with the well-determined eclipsing binaries low-mass components as well as with the theoretical models. While the primary stars radius 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. 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 Msun and suddenly reaches to maximum deviation at a mass of 0.34 Msun. Then, the deviations begin to decrease up to the solar mass. The maximum deviation seen at a mass of about 0.34 Msun 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 is most probably arisen from this star which may be radiated mostly in the infrared bands.
