Fast Apsidal Rotation and Physical Parameters of V1103 Cas

Astronomy Reports - We present the first high accuracy UBV RI(RI)c light curves of poor investigated eclipsing star V1103 Cas = GSC 3682 736 ( $$P{{ = 6.18}^{d}}$$ , $$V = {{11.16}^{m}}$$ , $$e =...     

The Physical Parameters of V680 Mon—Eclipsing Star with the Highest Known Eccentricity

Astronomy Reports - We present the first high accuracy UBVRI(RI)c CCD light curves of the poorly investigated eclipsing system V680 Mon = GSC 7428 218 (P = 8.54d, V = 10.02m). They were used to...     

Color variations of the blazar 3C 454.3 in 2004–2006

We present an analysis of multicolor (U BV RI JH K) observations of the blazar 3C 454.3 made in 2004–2006. We used the light curves compiled at the Turin Observatory from coordinated observations in the framework of the WEBT program. We consider color variations in two time intervals, when an unprecedented strong outburst occurred (2004–2005), and when the object was in a post-eruptive state and a low-amplitude brightness increase was observed (2006). The spectral energy distribution (SED) of the variable component remained the same within each of these intervals, but differed between them. In both cases, this SED followed a power law after correction for extinction, suggesting the variable component has a synchrotron nature. We conclude that the variations in the optical and IR were due to the same variable source. The object’s unusual color behavior (the brighter, the redder) was due to an increasing contribution from a variable component that was redder than the constant component (big blue bump).     

A Search for long-period brightness variations of the T Tauri stars T Tau,DI Cep,and SU Aur

We have searched for protostellar or protoplanetary structures in the vicinity of young T Tauri stars using a technique that is able to distinguish long-period components of the observed light curves. We perform a statistical spectral analysis of the one-year mean light curves of three selected stars (T Tau, DI Cep, and SU Aur) and plot synthetic light curves for the most reliable period of each star. In a first approximation, the results show a good coincidence between our synthetic light curves and the original light curves, supporting the hypothesis that protostellar or protoplanetary structures are present in the studied systems. An analysis of the 0.36–20 µm spectral energy distributions of the program stars also leads to the conclusion that infrared anomalies for young stars are most likely due to thermal radiation from not-yet-formed companions in the vicinity of the star.     

Analysis of photometric light curves solution for massive contact OB binary stars. LY Aurigae,BH Centauri,SV Centauri

We searched for signs of the presence of circumstellar gaseous matter in photometric data for massive contact early-type binaries by analyzing residual curves (the dependence of the difference between the observed and theoretical brightness variations on the orbital-period phase) for three such stars. The residual curves make it possible to estimate the influence of gas in the common envelope on the observed light curves for different phase intervals and to qualitatively describe the character of the distortion of the light from the system’s components. Changes of the residual curves from filter to filter indicate varying conditions in the circumstellar matter. Changes of the residual curves from one observation epoch to another indicate varying conditions in the circumstellar matter. We compared the residual curves obtained for different photometric bands and epochs via a correlation analysis. The distortion of light from the components of LY Aurigae in the ultraviolet differs from that in the visual. The distortion of light from the components of SV Centauri is appreciable, but not selective, and does not vary in time, while the distortion of light from BH Centauri possesses a strong selective component. A comparison of the radii computed for the components of BH Centauri and SV Centauri shows that the gas distribution near these binaries varies in time.     

Analysis of photometric light curves for massive contact binary OB stars. V701 Scorpii

To study the influence of circumstellar gaseous matter on the observed photometric characteristics of early-type, massive contact binaries, we investigated residual curves (difference between the observed and calculated brightnesses as functions of the orbital phase) for the star V701 Scorpii. The residual curves can be used to estimate the influence of gaseous matter in the common envelope on the observed light curves for different phase intervals, and to qualitatively describe the associated distortion of light from the system’s components. Changes of the residual curves from filter to filter indicate the wavelength dependence of the distortion of the light from the components in the circumstellar matter. Differences between the residual curves for different observing epochs testify to time variations in the conditions in the circumstellar matter. We compared the residual curves obtained for different photometric bands and observing epochs using correlation analyses. The distortion of the light from the components of V701 Scorpii in the UV differs from that in the visual and changes in time. This conclusion is supported by the calculated values of the overflow of the first critical Roche lobe by the components.     

Close Binary Stars. VIII: Close Binary Star Systems in the Late Stages of Evolution

Astronomy Reports - The paper analyzes observations of close binary systems (CBSs), their radial velocity curves, and light curves. Various methods are described for fitting the light curve of...     

Eclipsing System PS UMa: Evolutionary Status and Physical Parameters of the Components

We present the first high accuracy UBVRI(RI)c CCD light curves of the newly discovered eclipsing system PS UMa = GSC 4375 1733 ($$P = 9_{·}^{d}27$$, $$V = 12_{·}^{m}42$$). The photometric solutions are found, the physical parameters of the components are derived. The eccentricity of the orbit was found to be negligible e = 0.074, which made it difficult to measure the rate of the apsidal rotation. High accuracy of our observations allowed us to find the reliable parameters of the system. Components (Sp = F7 + G1) have advanced significantly in their evolution, the age of the system is 2.4 billion years. The mass and the radius of G1 component is larger and it is ahead of the F7 component in its evolution. The model of the system best suits the theory in the absence of the overshooting in the core. Obtained from our observations photometrical parallax π = 0$$_{.}^{\prime\prime }$$00102(2) coincides with GAIA DR2 value $$\pi =0_{·}^{\prime\prime }00106(3)$$ within their errors. The new EW type variable with period $$ \approx {\kern 1pt} 0_{·}^{d}40$$ was found in the field of PS UMa.     

南极碳质球粒陨石中两个富尖晶石球粒状难熔包体的岩石学和矿物化学特征

富尖晶石球粒状CAI(富Ca-Al难熔包体)是球粒陨石中一种特殊类型的CAI,在南极格罗夫山碳质球粒陨石GRV020025和GRV021579中共发现两个富尖晶石球粒状CAI———GRV020025-3RI8和GRV021579-3RI5。GRV020025-3RI8具有占统治地位的尖晶石,在球粒的最外边存在严重蚀变的不规则边,钙钛矿主要分布在靠近边的位置。与GRV020025-3RI8比较,GRV021579-3RI5的尖晶石中的钙钛矿消失,深绿辉石出现,薄薄的蚀变层位于尖晶石核和富钙辉石边之间。两个富尖晶石球粒状CAI的尖晶石均具有低含量FeO和ZnO的特征,而且GRV021579-3RI5具有较GRV020025-3RI8更高的TiO2含量。岩石学和矿物化学特征表明,GRV020025-3RI8和GRV021579-3RI5都经历过熔融结晶过程,它们的蚀变均发生在非氧化的含水或无水的环境中。     

Interpretation of light curves of IP Peg in a model with shockless interaction between the gas stream and disk

We have analyzed light curves of the eclipsing cataclysmic variable IP Peg. A model with a shockless interaction between the gaseous stream and disk (i.e., an elliptical disk with a “hot line”) can describe the main characteristic features of the light curve of the interacting close binary better than a classical model with a “hot spot” at the outer boundary of a circular accretion disk. In particular, the hot-line model can reproduce the luminosity increase observed at phases ?～0.1–0.2 and ?～0.5–0.6, which is not possible in the standard hot-spot model. The advantages of the hot-line model are particularly striking for the IR light curves of IP Peg: the discrepancy χ² between the theoretical and observed light curves is 49 for the model with a shockless interaction between the gaseous stream and disk, and 2681 for the standard hot-spot model.     

Relationship between summer monsoon rainfall and cyclogenesis over Bay of Bengal during post-monsoon (October–December) season

In this study, an attempt has been made to examine the relationship between summer monsoon rainfall (June–September) and the total number of depressions, cyclones and severe cyclones (TNDC) over Bay of Bengal during the post-monsoon (October–December) season. The seasonal rainfall of the subdivisions (located in south India) (referred as rainfall index – RI), is positively and significantly correlated (r=0.59; significant at >99% level) with the TNDC during the period, 1984–2013. By using the first differences (current season minus previous season), the correlations are enhanced and a remarkably high correlation of 0.87 is observed between TNDC and RI for the recent period, 1993–2013. The average seasonal genesis potential parameter (GPP) showed a very high correlation of 0.84 with the TNDC. A very high correlation of 0.83 is observed between GPP and RI for the period, 1993–2013. The relative vorticity and mid-tropospheric relative humidity are found to be the dominant terms in GPP. The GPP was 3.5 times higher in above (below) normal RI in which TNDC was 4 (2). It is inferred that RI is playing a key role in TNDC by modulating the environmental conditions (low level vorticity and relative humidity) over Bay of Bengal during post-monsoon season which could be seen from the very high correlation of 0.87 (which explains 76% variability in TNDC). For the first time, we show that RI is a precursor for the TNDC over Bay of Bengal during post-monsoon season. Strong westerlies after the SW monsoon season transport moisture over the subdivisions towards Bay of Bengal due to cyclonic circulation. This circulation favours upward motion and hence transport moisture vertically to mid-troposphere which causes convective instability and this in turn favour more number of TNDC, under above-normal RI year.     

An index for describing the core-stone shape in weathered columnar joints

The shape of core-stones remained in the weathering basalt column is an index to classify its weathered degree. In this paper, a roundness index (RI) like the box dimension using in fractal theory, was employed to quantitatively measure the shape of core-stone in various weathering grades. The rounded core-stone that is weathered seriously has a smaller RI value. According to the value of RI, the five classes shown in the Russell–Taylor–Pettijohn chart for visually classifying grain shape is available to approximately determine the weathered grades of core-stones remained in the basalt column in Taiwan. A slump test is preliminarily tested to show the difference in repose angle of a stability slope assembled by the grains in a similar shape. The collection of angular core-stones those are less weathered (with a higher RI value) indeed reveals a greater repose angle.     

再论铀的中和还原成矿作用

反应指数是水文地球化学条件的实测值与水地化作用的临界值之间的相对值。中和还原沉淀作用的充分必要条件是与其有关的所有水文地球化学条件的反应指数都应符合反应指数法则。热力学计算和实验证明配位体浓度,如CO_3~(2-),F~-等,是阻碍铀还原沉淀的主要因素。降低CO_3~(2-)配位体浓度的主要作用是中和作用导致的CO_3~(2-)形式转化为CO_2逸出和CaCO_3沉淀。对相山矿田的铀成矿作用的水地球化学条件计算结果表明,中和作用是促使铀还原沉淀的促发钮,中和作用能导致与铀还原沉淀反应,有关的所有反应,有关的所有反应指数符合反应指数法则的要求。     

On the reconstruction of the surface structure of the spotted stars

We have developed and tested a light-curve inversion technique for photometric mapping of spotted stars. The surface of a spotted star is partitioned into small area elements, over which a search is carried out for the intensity distribution providing the best agreement between the observed and model light curves within a specified uncertainty. We have tested mapping techniques based on the use of both a single light curve and several light curves obtained in different photometric bands. Surface reconstruction artifacts due to the ill-posed nature of the problem have been identified.     

A search for periodicity in the light curves of selected blazars

We present an analysis of multifrequency light curves of the sources 2223-052 (3C 446), 2230+114 (CTA 102), and 2251+158 (3C 454.3), which had shown evidence of quasiperiodic activity. The analysis made use of data from the University of Michigan Radio Astronomy Observatory (USA) at 4.8, 8, and 14.5 GHz, as well as the Metsahovi Radio Astronomy Observatory (Finland) at 22 and 37 GHz. Application of two different methods (the discrete autocorrelation function and the method of Jurkevich) both revealed evidence for periodicity in the flux variations of these sources at essentially all frequencies. The periods derived for at least two of the sources—2223-052 and 2251+158—are in good agreement with the time interval between the appearance of successive VLBI components. The derived periods for 2251+158 (P = 12.4 yr and 2223-052 (P = 5.8 yr) coincide with the periods found earlier by other authors based on optical light curves.     

Interpretation of orbital light curves of U Geminorum

We interpret optical and IR orbital light curves of the dwarf nova U Gem in its quiescent state in the framework of “hot line” and “hot spot” models. The hot-line model provides an adequate fit to the light curves, while the hot-spot model is not fully consistent with the observations. The minimum χ² residuals for the hot-spot and hot-line models are 2203 and 168, respectively.     

Optical and photometric studies of Earth orbiting small space objects

Variations of light curves for space objects are investigated. Optical observations and photometric measurements for small space debris on highly elliptical orbits (HEO) and geostationary orbits (GEO) are used to determine their orbital parameters. Light curves of small space debris with various area-to-mass ratios and orbital characteristics are discussed. Tracking of some objects shows very rapid brightness variations related to perturbations of the orbital parameters. Changes in brightness and equatorial coordinates of the studied objects are found in observational data. Our results allow improving the accuracy of space debris orbital elements.     

Light curve analysis for eclipsing systems with exoplanets. The systems Kepler-5b,Kepler-6b,and Kepler-7b

High-accuracy light curves for the binaries with exoplanets Kepler-5b, Kepler-6b, and Kepler-7b have been analyzed. The radii of the stars and the planets and the orbital inclinations of the binaries are derived. Reliable estimates of the linear and quadratic limb-darkening coefficients and their confidence intervals (uncertainties) are presented.     

Nuclear activity of the Seyfert galaxy NGC 7469 in 1990–2006: Observations from the Mt. Maidanak Observatory

We present the results of UBV RI observations of the nucleus of the Seyfert 1 galaxy NGC 7469 performed in 1990–2006 at the Mt. Maidanak Observatory of the Ulug Beg Astronomical Institute in Uzbekistan. Light curves for various apertures are plotted for all the filters. Our analysis of these light curves indicates the presence of short-time-scale (from several days to several weeks) and long-term (∼8–9 years) variability of the nucleus. The character of the brightness variations in all the optical filters is the same, with the relative amplitude of the variations decreasing from U to V, but being higher in R than in V. A comparison with earlier observations (prior to 1990) indicates an increase of the time scale for the long-term variability, from three to six years to eight to nine years, providing evidence for changing emission conditions in the accretion disk. We present the results of a statistical analysis of the light curves and an analysis of the color characteristics during different activity periods. Color-index measurements using various apertures demonstrate that the color becomes bluer towards the galaxy nucleus.     

Accretion disk of the cataclysmic variable IY UMa in quiescence and its active state

We present the results of a study of the eclipsing binary IY UMa (type SU UMa) during its superoutburst of 2004 and in quiescence.We have refined the orbital period of the system. Light curves are presented for various states of activity.We estimate the parameters of IYUMa during the superoutburst and in quiescence for hot-line and spiral-wave models. The spiral-wave model, which takes into account the presence of vertical perturbations in outer parts of the disk, is able to reproduce the light-curve shapes and phases of dips in the out-of-eclipse parts of the binary’s light curves during the outburst both qualitatively and quantitatively.