Parameters of UX CVn

We have derived a complete set of parameters for the close binary system UX CVn made up of degenerate objects based on photometric and spectral observations. The total mass of the components is close to one solar mass, so that its further evolution cannot result in a type-I supernova. The spectrum of the binary indicates that the surface temperature of the hot subdwarf may have increased by 2000 K over 40 years. This heating rate is consistent with theoretical estimates for evolutionary tracks of low-luminosity hot subdwarfs. We also determined the abundances for ten elements in the atmosphere of the primary, which are consistent with the hypothesis that the binary is a member of Population II. There are signs of synthesized material ejected onto the surface of the star. © 2002 MAIK "Nauka/Interperiodica"

A long trail behind the planetary nebula HFG1 (PK 136+05) and its precataclysmic binary central star V664 Cas

A deep wide-field image in the light of the Halpha+[N II] emission lines, of the planetary nebula HFG1 which surrounds the precataclysmic binary system V664 Cas, has revealed a tail of emission at least 20' long, at a position angle of 316deg. Evidence is presented which suggests that this is an ~10^5 y old trail of shocked material, left behind V664 Cas as it ejects matter whilst ploughing through its local interstellar media at anywhere between 29 and 59 km/s depending on its distance from the Sun.Comment: 3 pages, 1 figure, accepted for publication in MNRA

Atmospheres and spectra of X-ray illuminated stars: A nongray model

We continue to study illuminated stellar atmospheres with radiative transfer. A method for computing X-ray irradiated blanketed model atmospheres is described. The heating function of such atmospheres has been found to be complicated and to have a minimum at the depth of continuum formation. We have established that the normalized heating function does not depend on the intensity of the incident radiation and atmospheric parameters. The heating of only deep layers is shown to decrease sharply with increasing angle of incidence of the irradiative flux. The effect of the soft and hard X-ray emission components on the formation of the heating function is explored. A sharp decrease in the heating of chromospheric layers when allowing for line blanketing has been ascertained. The gray model is shown to be valid, to a good approximation, for describing illuminated atmospheres. The cooling function is computed over the ranges Teff = 3000-200 000 K and log Pg from -2.0 to 8.0, and the possible existence of temperature instabilities in the chromospheres of irradiated atmospheres has been revealed

Atmospheres and spectra of X-ray illuminated stars: A gray model

A gray model is used to explore the effect of heating of stellar atmospheres by an external X-ray flux. This flux is shown to produce additional heating functions in the surface and inner layers. The opacity sources in the X-ray region are determined. A technique for calculating the reflection effect in the gray approximation is presented. The illuminated and normal atmospheres and their spectra are shown to differ considerably

The atmospheres and spectra of X-ray illuminated stars: Line formation

The formation of lines in X-ray illuminated atmospheres and in close binary systems with X-ray sources is studied. It is shown that there are three groups of lines: "cool" (absorption lines), "normal" (absorption lines with emission cores), and "hot" (emission lines). The effect of the parameters of the irradiative X-ray flux and the observing conditions on the formation of lines of different groups is analyzed. The method of gray approximation has been found to be applicable to the synthesis of the profiles of cool and normal lines. The method of constructing synthetic spectra for close binary systems has been developed, and the possibility of determining the parameters of the systems from an analysis of lines of different groups is shown

Effect Of Annealing On The Behavior Of Oxygen Dissolved In Germanium And Optical Properties Of Single Crystals

The annealing effect in the temperature range from 350 to 450 °С on the behavior of interstitial oxygen Оi dissolved in germanium and on optical properties of single crystals has been investigated by Fourier transformed infrared spectrometry. It was found that oxygen band maximum of 843 cm–1 shifted toward the 856 cm−1 with oxygen concentration increasing after annealing at the oxygen partial pressure ranged from 1 to 103 Pа. The annealing at lower  values led to the decrease of 843 cm–1 band intensity due to the formation of thermal donors (TD) on the basis of dissolved oxygen atoms Оi. It was established that TD formation and the decrease of unbound oxygen concentration affected optical properties of the crystals

Radial-velocity curves and theoretical spectral-line profiles of the components of low-mass close X-ray binary systems

We present the results of calculations of theoretical absorption-line profiles and radial-velocity curves for optical components in X-ray binary systems. Tidal distortion of the optical star and X-ray heating by incident radiation from the relativistic object are taken into account. An emission component forms whose intensity varies with orbital phase in the absorption-line profile in the presence of significant X-ray heating. As a result, the width of the line decreases rather than increases at quadrature. The line profiles and equivalent widths and the radial-velocity curves depend substantially on the parameters of the binary systems. This provides the possibility of directly determining component masses and orbital inclinations from high-resolution spectroscopic observations of X-ray binary systems. © 2005 Pleiades Publishing, Inc

Investigation of the new cataclysmic variable 1RXS J180834.7+101041

We present the results of our photometric and spectroscopic studies of the new eclipsing cataclysmic variable star 1RXS J180834.7+101041. Its spectrum exhibits double-peaked hydrogen and helium emission lines. The Doppler maps constructed from hydrogen lines show a nonuniform distribution of emission in the disk similar to that observed in IP Peg. This suggests that the object can be a cataclysmic variable with tidal density waves in the disk. We have determined the component masses (M_WD =0.8 \pm 0.22 M_sun and M_RD =0.14 \pm 0.02 M_sun) and the binary inclination (i =78 \pm 1.5 deg) based on well-known relations between parameters for cataclysmic variable stars. We have modeled the binary light curves and showed that the model of a disk with two spots is capable of explaining the main observed features of the light curves.Comment: 22 pages, 9 figures, 2 tables, published in Astronomy Letters, 2011, 37, 845-85

Analysis of reflection effects in HS 2333+3927

The results of photometric and spectroscopic observations of the pre-cataclysmic variable HS 2333+3927, which is a HW Vir binary system, are analyzed. The parameters of the sdB subdwarf companion (T eff = 37 500 ± 500 K, log g = 5.7 ± 0.05) and the chemical composition of its atmosphere are refined using a spectrum of the binary system obtained at minimum brightness. Reflection effects can fully explain the observed brightness variations of HS 2333+3927, changes in the HI and HeI line profiles, and distortions of the radial-velocity curve of the primary star. A new method for determining the component-mass ratios in HW Vir binaries, based on their radial-velocity curves and models of irradiated atmospheres, is proposed. The set of parameters obtained for the binary components corresponds to models of horizontal-branch sdB subdwarfs and main-sequence stars. © 2012 Pleiades Publishing, Ltd