A. I. Khaliullina

Orbital-period variations in the eclipsing binary Y Cam

We have studied the time behavior of the orbital period and the primary’s pulsation period for the eclipsing binary system Y Cam, whose secondary fills its Roche lobe and whose primary is a δ Scuti star. The times of minima available for this eclipsing binary cover 120 years. δ Scuti pulsations of the primary have been observed over the last 50 years, with the period of these pulsational brightness variations remaining virtually unchanged during the entire observed time interval. The large-amplitude cyclic variations of the orbital period of Y Cam cannot be explained solely by the presence of a third body in the system. It is possible to explain the period variations of Y Cam with magnetic oscillations or a superposition of a stationary matter flow from the lower-mass to the higher-mass component together with magnetic oscillations, similar to the case of AB Cas. A good agreement with observations is provided by a model assuming a stationary matter flow from the secondary filling its Roche lobe to the primary, at the rate of 2.85 × 10−7M⊙/year, superposed with irregular period jumps that can be explained by instabilities in the matter flow. We have detected cyclic variations of the orbital period of Y Cam with an amplitude of 0.011d, which can be understood if the binary moves in a long-period orbit (with a period of 38.6 years) around a third body with mass M3 s> 0.30M⊙. These cyclic period variations of the eclipsing binary agree with the observed small period variations of the δ Scuti pulsations.

A third body as the origin of the orbital-period variations in the eclipsing binaries TW cas and BE Vul

The orbital-period variations in the Algol-type eclipsing binaries TW Cas and BE Vul are analyzed. Cyclic variations of the period have been found, rather than a gradual decrease in the period, as was believed earlier. The cyclic variations of the period of the BE Vul system are superposed on a secular increase in the period that can be explained with a uniform flow of matter from the lower-mass to the higher-mass component, with the total angular momentum being conserved. The mass-transfer rate is about 0.84 ⋗ 10−7M⊙/year. No secular period change is observed for TW Cas. The cyclic variatons in the orbital periods of TW Cas and BE Vul can be explained if the eclipsing binaries move along long-period orbits with high eccentricities (e = 0.74 and 0.6, respectively). In the TW Cas system, the eclipsing binary moves around a third body with a mass M3 > 0.64 M⊙with a period of 203 years; the eclipsing binary in BE Vul moves around a third body with a massM3 > 0.6M⊙with a period of 156 year.

The eclipsing binary HS hercules: Photometric elements and the evolutionary stages of its components

We used a photoelectric photometer designed by V.M. Lyutyi and the Zeiss-600 telescope of the Sternberg Astronomical Institute’s Crimean Observatory to acquire precise UBV brightness measurements (σobsV ∼ 0.007m) for the eclipsing binary system HS Her in 1984–1991. These measurements continue the homogeneous series of observations of this star commenced in 1969 by D.Ya. Martynov using the same equipment. Our detailed analysis of this homogeneous 22-year series of photoelectric observations has yielded a self-consistent set of physical and geometric parameters of the binary, and enabled us to establish the evolutionary stages of its components. The systems’s primary, M1 = 5 M⊙, is at the beginning of its main-sequence evolution, whereas its secondary, M2 = 1.6 M⊙, has not yet reached the main sequence. The binary’s age is estimated to be t = (17 ± 3) × 106 years.

Apsidal motion and the third-body problem in the binary HS Her

Our analysis of a 22-year uniform series of photoelectric U BV measurements of HS Her, started in 1969–1983 by D.Ya. Martynov and completed by us in 1984–1991, enabled us to determine new times of minima and revise some times of minima published earlier. Combined with other published data, this information can be used to improve the system’s apsidal elements: Uobs = (89.7 ± 5.1) years and log-k2obs = −2.33(4), testifying to a somewhat stronger concentration of matter towards the center than is predicted by current models for main-sequence stars (log -k2th = −2.21). This provides additional evidence that the system’s secondary is at the pre-main-sequence stage of evolution, as we suggested earlier based on our analysis of the system’s photometric elements. We confirm the presence of a third body in the system in a long-period eccentric orbit, as was first suggested in 2002 by Wolf et al. However, in contrast to the results of that paper, we demonstrate that the currently available observational data are insufficient to reliably determine this orbit’s parameters. We estimate the mass of the third body to be M3 = (1.0−2.0)M⊙ for M1 = 5M⊙ and M2 = 1.6 M⊙.

Apsidal Motion and Physical Parameters of the Eclipsing Binary System AR Cas

AbstractUsing the four-channel automatic photoelectric photometer of the Sternberg Astronomical Institute’s Tien Shan Mountain Observatory, we have acquired accurate (σobs≈0.004m) W BV R brightness measurements for the eclipsing binary AR Cas during selected phases before eclipse ingress and after egress, as well as at the center of minima. A joint analysis of these measurements with other published data has enabled us to derive for the first time a self-consistent set of physical and geometrical parameters for the star and the evolutionary age of its components, t=(60±3)×106 years. We have found the period of the apsidal motion (Uobs=1100±160 years,

The probable quadruple systems FK Aql and FZ Del

\dot \omega _{obs} = 0^\circ .327 \pm 0^\circ .049

Precision W BV R photoelectric photometry of the eclipsing system RR Lyncis

years−1) and the apsidal parameter of the primary, logk2,1obs=−2.41±0.08, with the apsidal parameter being in good agreement with current models of stellar evolution. There is an ultraviolet excess in the primary’s radiation, Δ(U−B)=−0.12m and Δ(B−V)=−0.06m, possibly due to a metal deficiency in the star’s atmosphere.

Orbital period variations of the eclipsing binaries TU Cnc, VZ Leo, and OS Ori

AbstractBased on 70 years of published photoelectric observations, we have detected quasi-periodic cophased oscillations of the times of the primary and secondary minima of RR Lyn, one of the brightest and nearest eclipsing binaries in the northern sky (