O. V. Kiyaeva

Pulkovo catalog of relative positions and motions of visual double and multiple stars from photographic observations with the 26-inch refractor in 1960–2007

The results of long-term, uniform, photographic observations of visual double and multiple stars obtained on the Pulkovo 26″ refractor are presented. Relative positions are calculated for 259 pairs of visual double stars in 194 systems, with the relative motions also computed for 127 pairs. Lower limits for the total masses of the systems for which elliptical orbits possible are also found for 48 pairs with reliable parallaxes from the Hipparcos catalog. The accuracies of the three measuring machines used in the reduction of the photographic plates are compared. Component separations measured with different machines can differ by as much as 0.2″, demonstrating the advantages of using uniform observations.

Photopolarimetric activity and circumstellar environment of the young binary system DF Tau

We present the results of multi-year photometric and polarimetric observations of the young binary system DF Tau in the UBVRI bands, as well as bispectrum speckle interferometric observations in the H and K bands obtained between 2001 and 2003. The photometric and polarimetric observations suggest that the linear polarization of DF Tau does not depend on its brightness, and the polarization variation has a stochastic character. This result confirms earlier suggestions about the dominant role of hot accretion spots in the photometric activity of this star. We argue that the hot spots are at high latitudes and/or the star rotation axis is inclined to the line-of-sight. The influence of circumstellar (CS) dust on the variability is probably small since the inclination of the primarys CS disk to the line-of-sight is large. Using the total mass of the binary system DF Tau from Hartigan & Kenyon (2003, ApJ, 583, 334), we calculated new orbital parameters of the system. The new value of the orbital period (P = 74.1 yr) disagrees with the photometric cycle of about 40 yr revealed by Lamzin et al. (2001b, A&A, 372, 922) from analysis of the historical light curve of this star. This suggests that this cycle is not caused by the orbital motions of the binary components, but probably reflects the cyclical variability of the global magnetic field on the main component.

Criteria for the Stability of Triple Systems and Their Application to Observations of Multiple Stars

Criteria for stability of triple systems are studied and compared with the results of numerical simulations obtained for model triple systems and observed multiple stars. The results for the stability analyses using two new criteria—those of Aarseth and of Valtonen et al.—agree with the simulation results in 98% of cases. Thus, these criteria can be used to analyze the stability of systems for which direct modeling of their dynamical evolution is difficult (for example, because not all orbital parameters for their subsystems are known). The last published version of the “Multiple-Star Catalog” of Tokovinin is analyzed to search for systems that may be unstable according to the two new criteria. More detailed studies are carried out for the HD 284419 (T Tau) system. The parameters of the apparent motion method is used to obtain new orbital solutions for this system. The regions of dynamical stability of the system as functions of the orbital parameters are estimated. It is not possible to determine a unique solution for the orbit with the available data; for periods shorter than 300 yr and longer than 5500 yr, the probability of decay of the system on time scales less than 107 yr is high. This conclusion is supported by the application of the stability criteria, as well as direct modeling of the system’s dynamical evolution.

Accurate relative positions and motions of poorly studied binary stars

We have studied the relative motions of the components of 25 visual binary and multiple stars for which only a modest number of observations of various types had accumulated due to their small relative component motions. A uniform series of photographic observations obtained over many years on the 26-inch refractor of the Pulkovo Observatory are used to calculate the parameters of the apparent relative positions and motions, which can be used for further kinematic and dynamical studies of these stars. A comparison of the relative and proper motions of the components indicates that they are physically bound. Optical components are identified in six systems—for the first time in the three systemsWDS00082+6217, ADS 830, and ADS 7361. The relative motions in ADS 861 and ADS 12925 suggest the presence of perturbing invisible companions, but this requires confirmation based on more accurate observations. The apparent motion parameters method yields a family of orbits with a minimum period of 26 000 yrs for the nearby wide visual binary Gliese 745, for which the parallax and relative radial velocity of the components are known.

Orbits of the Visual Binaries ADS 8814 and ADS 8065 from Observations along a Short Arc

The orbits of the visual binaries ADS 8814 and ADS 8065 are determined for the first time. The orbits were calculated using the parameters of the apparent motion, based on position observations along short arcs obtained on the 26-inch refrector of the Pulkovo Observatory, supplemented with radial-velocity observations for the stellar components in both pairs obtained on the 1-m telescope of the Simeiz Section of the Crimean Astrophysical Observatory. All previous visual and photographic observations of these stars after 1832 were also taken into account. The orbit of ADS 8814 was refined using the differential-correction method. The orbital periods of these two stars are about 800 and 6000 years, respectively. The mass estimates derived for the known parallaxes from the Hipparcos catalog correspond to the spectral types of these stars. The polar vectors of the obtained orbits in Galactic coordinates are also given.

Photographic observations of visual double stars at Pulkovo: Digitization, measurement, and calibration

We present the results of determining the relative positions of 359 pairs of stars. More than 6000 photographic plates were obtained in 1960–2007 at the 26-inch refractor of the Pulkovo Observatory. The plates have been digitized with a Canon EOS 5D Mark II digital camera and a long-focus Jupiter 21M lens; the scalewas 21 μm/pixel. Themeasurements have been calibrated using a template digitized with the Belgian high-precision ROB Digitizer. The results have been thoroughly investigated for systematic errors. We have studied the scale of the 26-inch refractor and revealed its temperature and time dependences. The application of a new digitization, measurement, and calibration technique has allowed the accuracy to be increased compared to the past measurements. The single-exposure measurement accuracy is within the range from 2 to 70 mas, on average, 28 mas in both coordinates. The errors of the yearly mean positions are, on average, 8.7 mas in the angular separation and 0.05◦. in the position angle.

The multiple system ADS 9626: A quadruple star or an encounter of two binaries?

The parameters of the quadruple system ADS 9626 (µ Boo) are analyzed. The system consists of two double stars: the Aa pair with an angular separation of ρ = 0.08″ and the BC pair with an angular separation of ρ = 2.2″, separated by ρ = 107″ and having the same parallaxes and proper motions. Position observations with the Pulkovo 26″ refractor have yielded from direct astrometric measurements the difference in the apparent magnitudes and the component-mass ratio for the BC subsystem: Δm = 0.59 ± 0.06, M(B)/M(C) = 1.18 ± 0.02. Spectroscopy with the Russian-Turkish 1.5-m telescope has yielded the radial velocities and physical parameters of the Aa, B, and C components. Speckle-interferometric observations with the 6-m telescope of the Special Astrophysical Observatory have provided the first measurements of the magnitude difference in the close Aa subsystem: Δm = 0.46 ± 0.03 (λ = 5500 Å) and Δm = 0.41 ± 0.03 (λ = 8000 Å). The new observations are consistent with the known orbits, which were used to find the radial velocities for the centers of mass of the inner subsystems. Themotion of the outer pair, Aa-BC, is studied using the apparent motion parameters (AMP) method. It is not possible to derive an elliptical orbit for this pair; the elements of a hyperbolic orbit have been estimated. The difference of the heavy-element abundances for the Aa and BC subsystems of 0.5 dex confirms that these pairs have a different origin. This suggests that we are observing here a close encounter of two binary stars.

Physical parameters and dynamical properties of the multiple system ι UMa (ADS 7114)

We analyze the physical parameters, orbital elements, and dynamic stability of the multiple system ι UMa (HD 76644 = ADS 7114). We have used the positions from the WDS catalog and our own observations on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the 1.5-m Russian-Turkish Telescope (Antalya, Turkey). We have obtained more precise orbital parameters of the subsystems, and spectral types, absolute magnitudes, and masses of the components. The primary has Sp = F0 V–IV, M = 1.7 ± 0.1M⊙, Teff = 7260 ± 70 K, and log g = 4.30 ± 0.07. The companion in the close Aa subsystem is most likely a white dwarf with a mass of approximately 1.0 ± 0.3M⊙. The spectral types and masses of the components in the BC subsystem are M3V, M4V and 0.35 ± 0.05M⊙, 0.30 ± 0.05M⊙, respectively. The total mass is 3.4 ± 0.4M⊙. The Aa subsystem probably has an orbital period of 4470d = 12.2y and an eccentricity of approximately 0.6. The outer subsystem seems to have a period of approximately 2084 yrs and an eccentricity of approximately 0.9. We have carried out simulations using the stability criteria and shown that for all possible variations in the component parameters, the multiple system is unstable on a time scale of less than 106 years with a probability exceeding 0.98. Possible reasons for this instability are discussed.

New orbits of wide visual double stars

Based on photographic and CCD observations with the Pulkovo 26-inch refractor, radial velocity measurements with the 1.5-m RTT-150 telescope (TUBITAK National Observatory, Turkey), and highly accurate observations published in the WDS catalog, we have obtained the orbits of ten wide visual double stars by the apparent motion parameter method. The orientation of the orbits in the Galactic coordinate system has been determined. For the outer pair of the multiple star HIP 12780 we have calculated a family of orbits with a minimum period P = 4634 yr. Two equivalent solutions with the same period have been obtained for the stars HIP 50 (P = 949 yr) and HIP 66195 (P = 3237 yr). We have unambiguously determined the orbits of six stars: HIP 12777 (P = 3327 yr), HIP 15058 (P = 420 yr), HIP 33287 (P = 1090 yr), HIP 48429 (P = 1066 yr), HIP 69751 (P = 957 yr), and HIP 73846 (P = 1348 yr). The orbit of HIP 55068 is orientated perpendicularly to the plane of the sky, P >1000 yr. The star HIP 48429 is suspected to have an invisible companion.

Dynamical investigations of the multiple stars

Abstract Two multiple stars - the quadruple star - Bootis (ADS 9173) and the triple star T Taury were investigated. The visual double star - Bootiswas studied on the basis of the Pulkovo 26-inch refractor observations 1982-2013. An invisible satellite of the component A was discovered due to long-term uniform series of observations. Its orbital period is 20 ± 2 years. The known invisible satellite of the component B with near 5 years period was confirmed due to high precision CCD observations. The astrometric orbits of the both components were calculated. The orbits of inner and outer pairs of the pre-main sequence binary T Taury were calculated on the basis of high precision observations by the VLT and on the Keck II Telescope. This weakly hierarchical triple system is stable with probability more than 70%.