Resumen es: El Next Generation Transit Survey (NGTS) es un nuevo sondeo d e exoplanetas transitantes de campo amplio que tiene como objetivo descubrir exoplanetas de...

BV R light curves and radial velocities for the double-lined eclipsing binary V1135 Her were obtained. Our analyses of the multi-color 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, �

We present the multi-color, five-year light curves and the radial velocities of the near-contact binary system KR Cyg. We derived the masses of the components as 2.88 ± 0.20 Mand 1.26 ± 0.07 Mand the radii as 2.59 ± 0.06 Rand 1.80 ± 0.04 R� . We also searched for the empirical determination of albedo and effective temperature of the cooler, less massive star of KRCyg, and of two similar near contact binaries AKCMi, and DOCas. The residuals between the observed and computed fluxes are attributed to the effect of mutual illumination which heats the surface layers of the illuminated star and does vary not only its bolometric albedo but also its limb-darkening coefficient and gravity-brightening exponent. The effective albedos are generally smaller than that expected from an envelope of convective star. These results are preliminary and speculative.

We present spectroscopic observations of the double-lined Algol type eclipsing binary V1898Cyg. Analyses of the BV light curves and RVs led to determination of the fundamental stellar parameters of the V1898Cyg’s components. The absolute parameters for the stars are derived as: M1 = 6.054 ± 0.037 M⊙, M2 = 1.162 ± 0.011 M⊙, R1 = 3.526 ± 0.009 R⊙, R2 = 2.640 ± 0.010 R⊙, Teff1 = 18000 ± 600 K, and Teff2 = 6200±200 K. The residuals between the observed and computed times of mid-eclipses were analysed and a rate of the period change u P/P = 6.68 ×10 −7 yr −1 was obtained; a mass transfer rate of 1.88×10 −7 M⊙ in a year is estimated. We have calculated the distance to the system V1898Cyg as 501 ± 5 pc using the infrared JHK magnitudes and bolometric corrections for the primary star. The components of the system’s proper motions present some indications about membership to the North America nebula.

The fundamental parameters of reddening, metallicity, age, and distance are presented for the poorly studied open clusters Be 89, Ru 135, and Be 10, derived from their CCD UBVRI photometry. The interstellar reddenings, E(B–V ), were measured in the two-color diagram, and the photometric metallicities, [Fe/H], from the ultraviolet excesses of the F-type stars. By fitting isochrones to the observed sequences of the clusters in five different color-magnitude diagrams, the weighted averages of distance moduli and heliocentric distances [(V0–MV ), d(kpc)] are (11.m 90 ± 0.m 06, 2.4 ± 0.06) for Be 89, (9.m 58 ± 0.m 07, 0.81 ± 0.03) for Ru 135, and (11.m 16 ± 0.m 06, 1.7 ± 0.05) for Be 10, and the weighted averages of the ages [log(A),A(Gyr)] are (9.58 ± 0.06, 3.8 ± 0.6) for Be 89, (9.58 ± 0.06, 3.8 ± 0.7) for Ru 135, and (9.06 ± 0.05, 1.08 ± 0.08) for Be 10.

Se han realizado observaciones espectroscopicas de la binaria eclipsante de baja masa NSV 11868841, y se han derivado las velocidades radiales de ambas componentes. Las masas y radios dererminados son M1 = 0.870 ± 0.074 M⊙, M2 = 0.607 ± 0.053 M⊙, R1 = 0.983 ± 0.030 R⊙, R2 = 0.901 ± 0.026 R⊙. Los radios de ambas componentes son, respectivamente, 10% y 57% mayores que los que corresponden a estrellas de la secuencia principal de edad cero y de las mismas masas. Esta discrepancia puede deberse a que ambas estrellas tienen una gran cobertura por manchas. Hemos reunido parametros absolutos para 21 binarias eclipsantes de doble linea y de baja masa, para comparar sus posiciones en los diagramas masa-radio y masa-temperatura efectiva. Los valores altos de los radios y las bajas temperaturas efectivas encontradas no son debidos a diferencias en metalicidad o en longitud de mezcla. Las discrepancias encontradas para estrellas de baja masa pueden deberse a campos magneticos que inhiben el transporte convectivo, lo cual propicia una gran cobertura de la superficie estelar por manchas magneticas