HR Bootis is a neglected binary that is found to be a solar-type (G2V) extreme mass ratio binary (EMRB). It was discovered by Hanley & Shapley in 1940. Surprisingly, little has been published in the intervening years. In 1999 it was characterized by a 0.31587day orbital period. Since that time it has been observed by various observers who have determined ~20 timings of minimum light over the past ~15000 orbits. Our observations in 2012 represent the first precision curves in the BVR_c_I_c_Johnson-Cousins wavelength bands. The light curves have rather low amplitudes, averaging some 0.5 magnitudes, yet they exhibit total eclipses, which is typical of the rare group of solar-type EMRBs. An improved linear ephemeris was computed along with a quadratic ephemeris showing a decaying orbit, which indicates magnetic breaking may be occurring. The light curve solution reveals that HR Boo is a contact system with a somewhat low 21% Roche-lobe fill-out but a mass ratio of q=4.09 (0.2444), which defines it as an EMRB. Two spots, both hot, were allowed to iterate to fit the light curve asymmetries. Their radii are 32{deg} and 16{deg}. Both are high-latitude polar spots indicative of strong magnetic activity. The shallow contact yet nearly equal component temperatures makes it an unusual addition to this group.
Photoelectric light curves of BH Vir in the UBVRI bands observed by Arevalo et al. (1987IBVS.3117....1A, 1990ApJ...354..352Z) in 1986 were analyzed by using the latest version of the Wilson-Devinney program and to investigate the photometric parameters and spot activity. Satisfactory fits were obtained by assuming a hot spot only on the secondary star.
UBVR_C_I_C_ photometry of the W UMa eclipsing binary FI Bootis has been obtained and analyzed simultaneously with previously published photometry and radial velocities. The analysis of the light and radial velocity curves shows that the system is an A-type W UMa system consisting of stars with masses 0.82 and 0.31M_{sun}_.
We present the first estimates of the relative and absolute parameters of the eclipsing binary EQ Boo based on a light-curve analysis (P=5.43d, V=8.8m). This star is simultaneously Component A of the visual binary ADS 9422 (spectral types F7V + G0V; separation of the components 1.3"; magnitude difference 0.7m). The derived disagreement between the components' physical parameters and the assumption that they have the same age can be removed if there is a fourth, late-type star in the system. This is also able to explain the observed anomaly in the behavior of the O-C residuals at times of minima.
New photoelectric UBV and BVRI observations, secured during August-November of 2002 at two observatories distant in local time are analyzed together with two earlier photometric data sets and all available radial velocities to derive the most accurate ephemeris of the binary and to set limits on its basic physical elements. These observations were obtained as a support for a high-dispersion spectroscopic study, results of which will be published separately. It was found that radial velocities and photometric observations spanning 53 years can be reconciled with the linear ephemeris T_(prim.min.)_=HJD 2440182.25628(46) + 0.698095113(29)days x E, where the rms errors of the last digits are given in brackets. Masses of the stars are 1.02 and 0.97 solar masses and the binary separation is 4.170 solar radii. There is still a large uncertainty in the stellar radii. We also report the discovery of rapid light variations on a time scale of hours seen in the U band light curve and offer a few thoughts on the future investigation of this binary.
GSC 3208 1986 is an NSVS and TYCHO binary, first observed from 1999 to 2000. It is a W UMa binary with a period of 0.405days. The present observations were taken in 2012 September and are of high precision, averaging a standard deviation of better than 5mmag. The amplitude of the light curve is very nearly 0.5mag yet it undergoes total eclipses. Dominion Astrophysical Observatory spectra give an F3V type (T~6900K) for the system, the earliest of the extreme mass ratio W UMa binaries. The linear period determination of 0.4045672days was calculated with the two sets of epochs available. An early NSVS light curve reveals that the period has been smoothly decreasing over its past 12000 orbits. The binary may be undergoing sinusoidal oscillations due to the presence of a third body, possibly with a period of 23+/-3years. The high inclination of 85{deg} results in a long duration secondary total eclipse, lasting some 49.5minutes. Findings indicate that GSC 3208 1986 is an immaculate extreme mass ratio, q(m_2_/m_1_)=0.24, A-type W UMa binary.
We present multicolor light curves for the W UMa-type eclipsing binary TU Boo for two epochs separated by 22 years. An analysis of the O-C diagram indicates the earlier observations took place right in the middle of a major period change, thus allowing for a unique study on mass transfer and period changes in this W UMa-type system. We compute model fits to our light curves, along with the only other published set, using the Wilson-Devinney program, and find temporally correlated changes in the size of the secondary component with anomalies in the O-C diagram. We investigate the cause of these changes and find support for the existence of rapid, large-scale mass transfer between the components.
New photoelectric UBVRI observations of the eclipsing variable V1016 Ori have been obtained with the AZT-11 telescope at Crimean Astrophysical Observatory and with the Zeiss-600 telescope at Mount Maidanak Observatory. Light curves are constructed from the new observations and from published and archival data. The table contains all used data.
We perform a study of the structure, density, and distribution of ionized circumstellar gas in the strongly interacting binary SX Cas. We apply our new model codes for electron scattering in circumstellar matter to analyze a previously unpublished, extensive linear polarization data set for SX Cas, collected during four successive observing periods in 1981-84 at the Crimean Astrophysical Observatory. These data are complemented by our polarization observations carried out in 2000 and 2005 with the KVA-60 telescope at La Palma.
We present the light curves of chromospherically active binary systems, RT And and ER Vul, obtained during 1995-1998 in BV/UBVR filters at the Ankara University Observatory and the TUBITAK National Observatory. In addition, the spot distributions for these systems are investigated by using the Wilson-Devinney program. Outside of the eclipses, the light curve variations are attributed to large cool spots located on one of components of the systems. While three spots were located on the primary component in the case of RT And, the location of three spots were considered on the secondary star in the case of ER Vul. From the spot motions in longitudes between 1995 and 1998, it was inferred that the migration period of the distortion wave has at value of 6.6 years for RT And.
