We present the results of J-, H-, and K-band spectroscopy on three SU UMa-type dwarf novae with orbital periods of 1.33 – 1.37 hr. We performed the SED fitting for the obtained spectra by assuming a power-law distribution for the accretion disk and using template spectra of late-type dwarfs for secondary star. ASAS 002511+1217.2 and EQ J183926+260409 are WZ Sge-type or WX Cet-type dwarf novae. We found strong water absorption features in their spectra, which are characteristic in late M- or L-type dwarfs. The SED fitting suggests that their secondary contributions to the overall SED are less than one third. We identified the secondary stars as M9 and L1 type dwarfs, which are rather less massive but still normal stars. The spectrum of SDSS J013701−091235 is dominated by the secondary component. Spectral features of this object are similar to those of an early M-type dwarf in spite of its short orbital period. The spectrum of SDSS 0137 strongly suggests that the evolutionary path of this object is different from that of ordinary CVs, and this object is a candidate of EI Psc-like systems.

The contact eclipsing binary system XX Leonis (p = 0.97 days, Sp A9) has been analysed using the PHOEBE programme, based on the Wilson–Devinney code. The BVRI light curves were obtained during spring 2006 using the 20-cm telescope and ST-7 CCD detector. The effective temperature of the primary component determined from the photometric analysis is T = (7342 ± 14) K, the inclination of the orbit is i = (84.83 ± 0.29)° and the photometric mass ratio q = (0.40 ± 0.01). The third-body hypothesis was also suggested; based on a period analysis using 57 minimum times this gave a period for the third body of p3 = (59.66 ± 0.05) yr, an amplitude of A = (0.036 ± 0.028) day and zero eccentricity, which yields as a minimum mass M3,min = (0.91 ± 0.01) M⊙.

The multiple stellar system SZ Cam is solved using the method of spectral disentrangling. Hα line profiles of three components are obtained and spectroscopic orbit elements are redetermined.

Using the 35 speckle measurements performed with PISCO in Merate between 2004 and 2006, and some complementary new astrometric measures, we present a new orbit for the visual binary ADS 8630 = γ Vir. This new series of measurements was essential for constraining the 169 year-period orbit since it covers an arc of 130° in the apparent orbit and includes the periastron passage of 2005.

We analyzed a new photometry of this well-known Algol-like eclipsing binary together with old photoelectric measurements with the aim of better understanding of its orbital period changes and short-time light variations modulating the mean light curve. The analysis has been done by the new method based on the combination of the principal component analysis and robust regression. New spectroscopic observations and radial-velocity curve are also presented.

We report on previously unpublished diffraction-limited NIR observations of the young binary star T Tauri South. Orbital elements have been estimated by a least–squares fit to the relative positions. Although the parameters are not well constrained by the observations, we can derive a minimum system mass of about 3 M⊙.

With the most recent astrometric measurements by Duchêne et al. (2006), hyperbolic (unbound) orbits can be excluded with high confidence. We conclude that T Tauri Sb is not in the process of being ejected from the system.

The U.S. Naval Observatory has produced its second CDROM of double star catalogs. This successor to the 2001.0 CDROM includes the latest versions (June 30 2006) of four major double star catalogs maintained at the USNO:

• • Washington Double Star Catalog (WDS),

• • Second Photometric Magnitude Difference Catalog,

• • Fourth Catalog of Interferometric Measurements of Binary Stars, and

• • Sixth Catalog of Orbits of Visual Binary Stars.

Each of these catalogs had seen significant changes during the past six years; for example, the WDS has grown by over 150,000 measures and the number of systems in the Interferometric Catalog has nearly doubled. Other improvements include precise coordinates for the vast majority of systems, as well as new observing lists for tens of thousands of “neglected” doubles.

Also included on this CDROM is a Catalog of Linear Elements for several hundred optical pairs. These elements should prove useful for improving the components' proper motions, as well as providing scale calibration out to several tens of arcseconds.

As was done with its predecessor, the new CDROM is automatically distributed free of charge to members of the double star community and to astronomy libraries. Others may receive a complementary copy upon request.

We investigate the development of Kelvin-Helmholtz instabilities in magnetized jets by means of high-resolution spatial simulations. Our main finding is the existence of a stabilizing mechanism driven by the initial disruption of the jet. This mechanism gives rise to a local amplification of the magnetic field, which in turn leads to an enhanced stability of the jet configuration.

Programs for modeling binary star observables compute emergent intensity for given composition as it varies with local effective temperature, local gravity, and direction. With arrival of huge data sets from Gaia and other surveys, the benefits of fast, compact, and accurate computation of atmospheric radiation is likely to remain critical for the foreseeable future. Experience has shown that accurate radiative modeling is important for good parameter estimation. Here we augment the radiative treatment by Van Hamme & Wilson (2003) with a procedure by which individuals can generate the needed Legendre coefficients for arbitrary photometric bands. Resulting files can be inserted directly into the Wilson-Devinney (W-D) program without sacrificing portability or program unity, and should easily be adaptable to other binary star programs. We expect the new bandpass options to become part of the public W-D program. Limb-darkening tables will be placed at http://www.fiu.edu/~vanhamme/limdark.htm.

Tests are carried out on retrieving Doppler maps from distorted stars in close binaries to estimate how Doppler imaging may be aliased by ellipticity. Maps obtained for the distorted shape are compared with the results of the simple spherical approximation, using real data of the RS CVn-type close binary star ζ Andromedae.

We investigate the possibility of a mass transfer enhancement during outburst in dwarf novae. We present here the first two-dimensional hydrodynamic simulations of the surface flows in the secondary, driven by the strong inhomogenous heating of the atmosphere during an outburst. We also discuss the possibility that the direct heating of the L1 point by the disc rim contributes to the mass transfer enhancement.

We present a study of the properties of circumstellar dust in symbiotic Miras during sufficiently long time intervals of minimal obscuration. The published JHKL magnitudes of o Ceti, RX Pup, KM Vel, V366 Car, V835 Cen, RR Tel and R Aqr have been collected. In order to investigate their long-term variations, we removed the Mira pulsations to correct their light curves. Assuming spherical temperature distribution of the dust in the close neighbourhood of the Mira, the DUSTY code was used to solve the radiative transfer in order to determine the dust temperature and its properties in each particular case.

The preliminary results of this systematic study of dust envelopes in symbiotic stars with Miras as cool components provide information on nature of dust in these objects.

The V and R light curves for 30 RR Lyrae stars in M15 were used to calculate their physical parameters. The Blazhko effect, previously reported in V12, was not detected. The determined values of the iron content and distance of the cluster are: [Fe/H] = −1.98 ± 0.24 and d = 8.67 ± 0.41 kpc, respectively. The mean values of the physical parameters determined for the RR Lyrae stars place the cluster precisely into the sequences Oosterhoff type – metallicity and metallicity – effective temperature, valid for globular clusters.

The relative positions of Hipparcos visual double star components are currently known with a precision around fifty mas. Modern CCD astrometric observations of these objects achieve an accuracy of their angular separation between ten and twenty mas per observation. New CCD measurements have been obtained at Kryonerion Observatory in the north hemisphere. They provide current relative positions of visual double stars which are at least twice as accurate as the ones provided by Hipparcos. The new measurements will permit us to extract the physical pairs from the sample, and the double stars, which have components of common origin. Final statistics of these systems will improve our understanding of stellar formation and evolution rates of wide binaries in the solar neighborhood.

Detached eclipsing binaries are very useful objects for calibrating theoretical stellar models and checking their predictions. Detached eclipsing binaries in open clusters are particularly important because of the additional constraints on their age and chemical composition from their membership of the cluster. I compile a list containing absolute parameters of well-studied eclipsing binaries in open clusters, and present new observational data on the B-type systems V1481 Cyg and V2263 Cyg which are members of the young open cluster NGC 7128.

We are developing two new systems of a high-speed CCD camera, and an automated monitor telescope. This camera using a frame transfer-type CCD that enables us to take images each 27.3 msec at the highest speed. We wish to investigate accretion and eruption phenomena around compact stars by optical light. The system we have developed for automated monitoring of X-ray binaries and cataclysmic variables consists of a 30-cm reflector, a CCD camera, and a computer. It is a cheap system, but can monitor more than 150 systems each night. It will reveal long-term light curves of programmed stars of those transient systems, and catch sudden outbursts/decays. We will be able to start follow-up observations to clarify the mechanism of these activities as early as possible. We here report the current status of these projects, the target physics, and the future development.

We have begun a programme to obtain high-precision photometry of bright detached eclipsing binary (dEB) stars with the Wide-field InfraRed Explorer (WIRE) satellite (Bruntt & Buzasi 2006). Due to the small aperture of WIRE, only stars brighter than V = 6 can be observed. We are collecting data for about a dozen dEB targets and here we present preliminary results for three of them. We have chosen dEBs with primary components of B and early A type. One of our aims is to combine the information from the light curve analyses of the eclipses with asteroseismic information from analysis of the pulsation of the primary component.

In this work we have studied CM Draconis, one of the least massive eclipsing binaries known. Its components are very similar, with masses and radii of about 0.23 M⊙ and 0.25 R⊙. We have analysed light curves in the R and I bands to calculate the fundamental properties of this system with accuracies better than 1%. With these results we plan to carry out a thorough test of the models, which have been found to predict smaller radii and larger effective temperatures than observed for these low-mass stars. This will also be especially interesting in the case of CM Dra since the mechanism driving magnetic activity is thought to be different from that of more massive stars. In addition, the extended time-span of the observations has led to the detection of apsidal motion. This provides a further check on models through the determination of the internal structure of the stars.

The total masses of binaries are calculated on the basis of their orbital elements from the Sixth Catalog of Orbits of Visual Binary Stars. They are then compared with the values resulted from the mass-luminosity relation for the Main Sequence where as the input data are used: trigonometric parallax, total apparent magnitude of the pair (source Hipparcos Catalogue) and magnitude difference (source Hipparcos Catalogue and Photometric Magnitude Difference Catalog). It seems that for the pairs indicated as having qualitative orbital elements the agreement between the total-mass values obtained in these two ways is satisfactory.

The relation of the surface brightness, a parameter related to the apparent magnitude and the angular diameter of a star, with a colour index is used to determine various stellar parameters. Eclipsing spectroscopic binaries can even be used as a distance indicator. In this work, we use a number of low-mass eclipsing binaries, whose parameters have been accurately determined, to refine the Barnes-Evans–like relation FV − (Ic − K) introduced by Amado et al. (1999), a relation more suitable for the low temperature of these cool stars.