Photometric observations and light curve analysis of ST Aquarii

The system of ST Aquarii has been observed inB andV filters at KOTTAMIA Observatory in Egypt. Two light curves have been obtained and new times of minima have been calculated.The light curves have been analysed using the theory of Fourier transform of light changes in frequencydomain, and new geometrical and physical elements have been obtained.     

The astrometric observations of planetary satellites, close approaches and occultations of stars by asteroids and mutual events in the systems of planetary satellites with the 26-in. refractor of Pulkovo observatory in 1995-2006

Astrometric and photometric observations of major planets, their satellites and asteroids have been made with the 26-in. refractor of the Pulkovo observatory during the period from 1995 to 2006. The CCD (ST6) and photographic observations were carried out. Accurate relative position of satellites of Jupiter and Saturn have been derived. The positions of Saturn have been calculated using the theoretically predicted coordinates of satellites relative to the planet without measurements of the photographic images of the planet. Also the observations of Hale-Bopp comet and Mercury transit have been made. The 26-in. refractor has been included into the international campaign PHEMU-2003: photometric CCD observations of mutual occultations and eclipses of Galilean satellites. The light curves of the events have been obtained and parameters of the events have been determined.     

THREE SYNTHETIC LUNAR GLASSES*

Glasses have been synthesized that have the approximate compositions of lunar rocks 61156, 68415, and 77135, respectively. The glasses have been analyzed by conventional analytical and electron microprobe techniques and have been found to be highly homogeneous. They have been used successfully as electron microprobe standards and for experimental studies of crystallization and solar-wind implantation. Small amounts of these materials can be provided to investigators who would find them useful.     

Effect of rotation on unsteady hydromagnetic Couette flow

The effects of rotation and magnetic field on the Couette flow of an electrically-conducting fluid between two parallel plates have been discussed when one of the plates has been set into impulsive motion. Under the assumption of negligible induced magnetic field and the applied field being fixed relative to the moving plate, the governing momentum equations have been solved exactly, and the expressions for velocity and skin friction have been presented. The variations of velocity and skin friction have been discussed for different parameter values. The decrease in velocity due to rotation and its increase due to magnetic field have been shown.     

射电脉冲星的逆康普顿散射（ICS）模型和偏振观测

近来我们在射电脉冲星的逆康普顿散射模型,致密星物理以及一些相关问题上做了下列几项工作：１） 对脉冲星物理中的一系列基本理论进行了较深入的研究,包括对裸奇异星比中子星更可能是射电脉冲星之起源的观点的论证。２） 进一步发展了射电脉冲星的逆康普顿散射（ＩＣＳ） 模型并完成了一系列相关工作。３） 进行了脉冲星的偏振分析和有关观测工作,并用其结果对银河系磁场和旋臂结构进行了分析。４） 研究了黑洞脉冲星双星系统的一些特性,为黑洞的搜寻工作作了初步准备。     

Three-colour photometry of the eclipsing binary EI Cephei

The photoelectric elements of the system EI Cephei have been determined inU, B, V colours. The absolute dimensions have been determined and some evolutionary aspects have been discussed. A modified period of 8^d.439334 has been obtained. The system is a detached one.     

Static massive configurations with constant local adiabatic exponents

In this work an exhaustive study of static massive configurations with a constant local adiabatic exponent (₁) has been made under various physical conditions at the centre. The static parameters of these structures have been calculated at the extreme causality condition. These structures have been used to model neutron stars and the various neutron star parameters have been calculated. The radial pulsation and rotation of these configurations have also been discussed.     

Orbit determination and analysis for Cosmos 58 at 15th-order resonance, to evaluate geopotential harmonics of order 15 and 30

The orbital parameters of Cosmos 58 have been determined at 65 epochs from some 4500 observations, between March 1982 and September 1983, using the RAE orbit refinement program, PROP. During this time, the satellite passed slowly through 15th-order resonance, and the orbital inclination and eccentricity have been analysed. Six lumped 15th-order geopotential harmonic coefficients have been evaluated, with an accuracy equivalent to between 0.8 and 2.0cm in geoid height. Six 30th-order coefficients have also been determined, with accuracies between 2 and 7 cm in geoid height. The coefficients have been compared with those from the GEM 10B and 10C models. There is good agreement for nine of the twelve coefficients.     

Colour indices of the Markarian galaxies

By use of the ANS ultraviolet fluxes, optical (UBV) and IRAS infrared fluxes, several colour indices for a few Markarian galaxies have been investigated. A comparison of these indices with those for normal NGC galaxies has been carried out. Similarities and differences in the indices for the two groups of galaxies have been discussed and possible causes have been indicated.     

太阳2cm射电爆发精细结构的形态分析

本文介绍了北京师范大学天文系,在2cm波段上观测到的太阳射电精细结构(FS).这些FS都是叠加在微波爆发上的.其中重点对1990年5月23日与AR6063活动区成协的一个47GB型微波大爆发上叠加的FS的形态特征进行了分析.计算了几个有关的参数,并对结果进行了简单的讨论.     

Analytical solutions for saturated P Cygni type profiles

Analytical formulae for single P Cygni type saturated resonance line profiles in stellar winds have been derived. The limbdarkening and presence of underlying intrinsic atmospheric profile have been ignored. The Sobolev approximation for radiative transfer has been used and the general velocity law has been specified by widely used β parameter. The analytical formulae for the saturated resonance line profiles can be found for cases when 2β is an integer. The formulae for 2β = 1,2, 3 and 4 have been found by us. Also the formulae for calculating the line profiles in the cases of external and internal sharp truncation (cutoff) of the scattering shell have been given. Some characteristic line profiles have been presented. It has been shown that the turbulence-generated isotropic dominant backscattering of radiation in stellar winds generates wide dark plateaux in the blue wings of spectral lines, and the slopes of plateaux are shaped by turbulence. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamics of double open clusters in the galactic field

Data from catalogs of multiple open star clusters (OSCs) have been used to compile a list of double and triple OSCs. Seven pairs of young OSCs with similar ages of their components have been selected from them. The dynamical evolution of the selected pairs of clusters in the Galactic gravitational field has been simulated numerically. The individual cluster masses have been estimated and the time dependences of the separations between the clusters have been constructed. The separations between the clusters are shown to exceed the tidal cluster radii. Various hypotheses of the origin of double OSCs are discussed: chance formations of pairs, formation within the same star complex, etc.     

黑子活动区流场精细结构

本文通过太阳活动区光球和色球速度场和磁场观测资料,讨论了黑子活动区附近流场的精细结构,论述了太阳大气中物质的流动呈纤维结构,以及速度场纤维与磁场,色球纤维和网络结构之间的关系。     

Some Bianchi type-II cosmological models in Brans–Dicke theory

In this work, the Bianchi type-II anisotropic cosmological models have been investigated in the context of Brans–Dicke (BD) theory in the presence as well as absence of a magnetic field. The energy conditions of the models have been examined. The physical and kinematical behaviors of the models have also been discussed.     

Spectrophotometric study of the cepheids DT Cyg and SZ Tau

The effective temperatures of the cepheids DT Cyg and SZ Tau have been determined from a comparison of their spectral scans with appropriate stellar model atmospheres. Using these temperatures and an independent Wesselink radius determination, the luminosities of the stars have been determined. The pulsation masses and the evolutionary masses of the stars have been discussed.     

The existence and stability of the equilibrium points of a triaxial rigid body moving around another triaxial rigid body

The motion of two mutually attracting triaxial rigid bodies has been considered. Thirty six particular solutions corresponding to the libration points and analogous to the points Spoke, Arrow and Float (Duboshin, 1959) have been found. The stability of these libration points has been discussed in two categories of cases. In the first category, different shapes of the bodies have been taken and in the second category, the mass and the linear dimensions of one of the bodies have been taken small in comparison to the other.     

N-body simulations of tidal encounters between stellar systems

N-Body simulations have been performed to study the tidal effects of a primary stellar system on a secondary stellar system of density close to the Roche density. Two hyperbolic, one parabolic and one elliptic encounters have been simulated. The changes in energy, angular momentum, mass distribution, and shape of the secondary system have been determined in each case. The inner region containing about 40 per cent of the mass was found to be practically unchanged and the mass exterior to the tidal radius was found to escape. The intermediate region showed tidal distension. The thickness of this region decreased as we went from hyperbolic encounters to the elliptic encounter keeping the distance of closest approach constant. The numerical results for the fractional change in energy have been compared with the predictions of the available analytic formulae and the usefulness and limitations of the formulae have been discussed.     

Thermodynamic study of non-linear electrodynamics in loop quantum cosmology

In this work, we have discussed the Maxwell’s electrodynamics in non-linear forms in FRW universe. The energy density and pressure for non-linear electrodynamics have been written in the electro-magnetic universe. The Einstein’s field equations for flat FRW model in loop quantum cosmology have been considered if the universe is filled with the matter and electro-magnetic field. We separately assumed the magnetic universe and electric universe. The interaction between matter and magnetic field have been considered in one section and for some particular form of interaction term, we have found the solutions of magnetic field and the energy density of matter. We have also considered the interaction between the matter and electric field and another form of interaction term has been chosen to solve the field equations. The validity of generalized second law of thermodynamics has been investigated on apparent and event horizons using Gibb’s law and the first law of thermodynamics for magnetic and electric universe separately.     

Symplectic Mappings of Co-orbital Motion in the Restricted Problem of Three Bodies

The dynamics of co-orbital motion in the restricted three-body problem are investigated by symplectic mappings. Analytical and semi-numerical mappings have been developed and studied in detail. The mappings have been tested by numerical integration of the equations of motion. These mappings have been proved to be useful for a quick determination of the phase space structure reflecting the main characteristics of the dynamics of the co-orbital problem.     

Intensity variation of cosmic rays near the heliospheric current sheet

Cosmic ray intensity variations near the heliospheric current sheet—both above and below it—have been studied during 1964–1976. Superposed epoch analysis of the cosmic ray neutron monitor data with respect to sector boundaries (i.e., heliospheric current sheet crossings) has been performed. In this analysis we have used the data from neutron monitors well distributed in latitude over the Earth's surface. First, this study has been made during the two solar activity minimum periods 1964–1965 and 1975–1976, using the data from Thule (cut-off rigidity 0 GV), Deep River (cut-off rigidity 1.02 GV), Rome (cut-off rigidity 6.32 GV) and Huancayo (cut-off rigidity 13.45 GV) neutron monitors. We have also analyzed the data from Deep River, Rome and Huancayo neutron monitors, for whom we have the data for full period (1964–1976), by dividing the periods according to the changes in solar activity, interplanetary magnetic field polarity and coronal holes. All these studies have shown a negative gradient with respect to heliomagnetic latitude (current sheet). These results have been discussed in the light of theoretical and observational evidences. Suggestions have been given to overcome the discrepancy between the observational and theoretical results. Further, possible explanations for these observational results have been suggested.