Two-integral distribution functions for axisymmetric systems

Some formulae are presented for finding two-integral distribution functions (DFs) which depend only on the two classical integrals of the energy and the magnitude of the angular momentum with respect to the axis of symmetry for stellar systems with known axisymmetric densities. They come from a combination of the ideas of Eddington and Fricke and they are also an extension of those shown by Jiang and Ossipkov for finding anisotropic DFs for spherical galaxies. The density of the system is required to be expressed as a sum of products of functions of the potential and of the radial coordinate. The solution corresponding to this type of density is in turn a sum of products of functions of the energy and of the magnitude of the angular momentum about the axis of symmetry. The product of the density and its radial velocity dispersion can be also expressed as a sum of products of functions of the potential and of the radial coordinate. It can be further known that the density multiplied by its rotational velocity dispersion is equal to a sum of products of functions of the potential and of the radial coordinate minus the product of the density and the square of its mean rotational velocity. These formulae can be applied to the Binney and the Lynden-Bell models. An infinity of the odd DFs for the Binney model can be also found under the assumption of the laws of the rotational velocity.     

天琴RR型变星的绝对星等与运动学参数

对天琴ＲＲ型变星绝对星等运动学参数的测定及其对确定距离、球状星团年龄估计的影响,并对它们和其他距离指示器求得的结果的比较作了评述。由于不同作者采用的方法和资料不同,结果的不确定性较大。例如由直接和间接测定方法决定的天琴ＲＲ型变星的绝对星等分成较暗和较亮两类,由天琴ＲＲ型变星和其他距离批示器决定大麦哲伦云（ＬＭＣ）的距离模数和球状星团年龄估计并不完全一致。这表明还有一些天体测量和天体物理问题需要深入     

Models of the internal structure of Venus

A survey is made of the physics of the interiors of Venus. The introduction explains the main concepts used in the construction of models of Venus and the history of the question; observational data are gathered and analyzed. The method of constructing the models of the planet is explained and earth-like models of Venus and parametrically simple PVM models are discussed. Within the compass of a physical nodel of Venus, the thermodynamics of the mantle and core is constructed and questions are discussed concerning the heat conduction, temperature distribution in the lithosphere and the thermal flux from the interior of Venus, the electrical conduction and mechanical quality, and large-scale steady stresses in the mantle of Venus. A rheological model of the crust and mantle is constructed. In conclusion, the question as to the distribution of radioactivity and convection in the interior of the planet is discussed.     

Photometric study of the major satellites of Uranus

In this paper, we analyze the results of ground-based and space-born photometric observations of the major satellites of Uranus—Miranda, Ariel, Umbriel, Titania, and Oberon. All sets of photometric observations of the satellites available in the literature were examined for uniformity and systematic differences and summarized to a unified set by wavelength ranging from 0.25 to 2.4 μm. This set covers the interval of phase angles from 0.034° to 35°. The compound phase curves of brightness of the satellites in the spectral bands at 0.25, 0.41, 0.48, 0.56, 0.75, 0.91, 1.4, and 1.8 μm, which include a pronounced opposition surge and linear part, were constructed. For each satellite, the geometric albedo was found in different spectral bands taking into account the brightness opposition effect, and its spectral dependence was studied. It has been shown that the reflectance of the satellites linearly depends on the wavelength at different phase angles, but has different spectral gradients. The parameters of the phase functions of brightness, including the amplitude and the angular width of the brightness opposition surge, the phase coefficient, and the phase angle at which the nonlinear increase in brightness starts, were determined and their dependences on wavelength and geometric albedo were analyzed. Our investigations show that, in their optical properties, the satellites Miranda and Ariel, Titania and Oberon, and Umbriel present three types of surfaces. The observed parameters of the brightness opposition effect for the Uranian satellites, some ice satellites of Jupiter and Saturn, and the E-and S-type asteroids are analyzed and compared within the framework of the coherent backscattering and mutual shadowing mechanisms.     

Optical properties of spheroidal particles

A new exact solution of the diffraction problem for the homogeneous spheroid on the basis of the method of separation of variables is given. This solution is considerably more efficient than the one of Asano and Yamamoto from the computational point of view. The expressions for various characteristics of the scattered radiation are obtained. The radiation pressure on spheroidal particles is considered taking into account the radial and transversal components. The method of calculations and various tests, which were used to control the computer programs, are described. Numerical results for forward and arbitrary angles scattering by prolate and oblate spheroids with the refractive indices typical for ice and silicates are presented. The dependence of the results on the propagation direction and the polarization of the incident radiation, size of particle and its aspect ratio are examined. The asymptotics for the characteristics of the scattered radiation for the extremely prolate and extremely oblate spheroids are derived. The range of the validity of these approximations is studied. Astrophysical applications include: a) the calculations of the interstellar extinction, interstellar linear and circular polarization curves for the ensemble of partially oriented spheroidal grains, and b) the consideration of the profiles and polarization of the interstellar feature 2200 for the partially oriented graphite spheroids. Appendices contain the expressions for integrals of products of the angular spheroidal functions and the asymptotics for the oblate spheroidal functions.     

Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites

This paper is the entire report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites, including three annexes. Tables give the recemmended values for the directions of the north poles of rotation and the prime meridians of the planets and satellites. Reference surfaces for mapping these bodies are described. The annexes discuss the guiding principles, given in the body of the report, present explanatory notes, and provide a bibliography of the rotational elements and reference surfaces of the planets and satellites, definitions, and algebraic expressions of relevant parameters.     

High-sensitivity STEP-F spectrometer-telescope for high-energy particles of the CORONAS-PHOTON satellite experiment

The STEP-F satellite telescope for measuring electrons and protons of the Photon scientific equipment is described. Its design features are given. The device detects electrons, protons, and α-particles in the energy range 0.18–2.3, 7.4–55.2, and 298–160.0 MeV, respectively. Geometric factors vary in the range of 12.4–21.7 cm² sr, depending on the energy of the particles. In addition, there are three channels of mixed recording of particles of different types and channels of recording of the secondary electromagnetic radiation generated in the construction materials of the device and spacecraft. Methods and results of the computer simulation of the passage of the particle through detector materials are presented, along with configuration, calibration measurements, and tests (both standalone and integrated) within the complex of scientific instrumentation and spacecraft. Updated data on geometric factors of the device and energy ranges of the direct detection of charged high-energy particles and of channels of mixed recording of several types of particles are given. Special software is described for the rapid analysis of the processed data of the STEP-F telescope, and the visualization of time variations of particle fluxes with different time resolution in some periods of high solar activity and in its absence.     

Tectonics and Evolution of Novae and Coronae on Venus: Tectonophysical Modeling Based on Gravitational Models

This paper describes the results of tectonophysical modeling of the formation and evolution of novae and coronae—radial/concentric volcanotectonic structures typical of the surface of Venus. The formation of these structures is usually associated with the effect of the rising and subsequently relaxing mantle diapirs on the surface layers of the lithosphere. Two series of experiments with gravitational models reproduce the topographic changes and the evolution of structural patterns in the course of the formation of novae and coronae on Venus. For model materials, we chose (1) rubber (a Bingham liquid) to reproduce the behavior of the elastoviscous diapir material in one series of experiments and the lower part of the lithosphere in the other series and (2) flour to model tectonic structures in the upper, brittle part of the lithosphere. Regularities in the formation of the topographic and structural characteristics of novae and coronae have been demonstrated on models of different geometry. The process of formation of the dense radial fracturing in novae due to the mechanical elevation caused by the formation of a rising dome, which was suggested by many authors, is not corroborated by our models. In the course of modeling, we studied the influence of the relative dimensions of the diapir and the thickness of the overlying structures, or the relative depth of the neutral buoyancy surface of the diapir, on the topographic, morphological, and structural features of novae and coronae and on the possible paths of their evolution. Regularities are also revealed in the formation of tectonic structures in relation to the environment in which the diapir evolution occurs—in the brittle upper part of the lithosphere or in its lower, viscoplastic part.     

Effect of Hall Current and Finite Larmor Radius Corrections on Thermal Instability of Radiative Plasma for Star Formation in Interstellar Medium (ISM)

The effects of finite ion Larmor radius (FLR) corrections, Hall current and radiative heat-loss function on the thermal instability of an infinite homogeneous, viscous plasma incorporating the effects of finite electrical resistivity, thermal conductivity and permeability for star formation in interstellar medium have been investigated. A general dispersion relation is derived using the normal mode analysis method with the help of relevant linearized perturbation equations of the problem. The wave propagation is discussed for longitudinal and transverse directions to the external magnetic field and the conditions of modified thermal instabilities and stabilities are discussed in different cases. We find that the thermal instability criterion gets modified into radiative instability criterion. The finite electrical resistivity removes the effect of magnetic field and the viscosity of the medium removes the effect of FLR from the condition of radiative instability. The Hall parameter affects only the longitudinal mode of propagation and it has no effect on the transverse mode of propagation. Numerical calculation shows stabilizing effect of viscosity, heat-loss function and FLR corrections, and destabilizing effect of finite resistivity and permeability on the thermal instability. The outcome of the problem discussed the formation of star in the interstellar medium.     

The international planetary patrol program: An assessment of the first three years

Day-to-day and hour-to-hour changes in the large-scale atmospheric and surface features of the planets can now be studied more effectively than previously possible. Since 1969 a network of observatories has obtained almost uninterrupted photographic coverage during all apparitions of Jupiter and Mars, plus some of Venus. Patrol films and catalogues are available to the scientific community. Recent or current analyses include the distribution and motion of clouds on Mars, the development and decay of Martian dust storms, the seasonal, diurnal and random fluctuations in contrast between adjacent light and dark regions on Mars, the detection of vertical shear in the Jovian atmosphere, the longitudinal oscillation of the Red Spot, the dependence of rotation period on xenographic latitude and on time, the eruption and spread of SEB disturbances, and the retrograde circulation of the Venus cloud deck.     

BeppoSAX–ROSAT PSPC observations of the Shapley supercluster: A3562

We present a combined analysis of the BeppoSAX and ROSAT PSPC observation of the cluster of galaxies A3562, a massive member of the core of the Shapley supercluster. With a complex and interacting structure composed from two groups of galaxies and A3558 to the west, the surface brightness of A3562 shows excess in the sectors to east and south when compared with an azimuthally averaged model of the emission. The emission tends to be flatter, and the distribution of the gas broader, along the merging axis and in opposition to the two groups. We present the first determination of the gradients of the gas temperature and metallicity for a cluster in the Shapley region at large distance from the cluster centre. From an analysis of the BeppoSAX data in annuli and sectors, we observe both the profiles to be flat within 8 arcmin (∼0.62 Mpc), with emission-weighted values of kT =5.1±0.2 keV and Z =0.39±0.05 Z_⊙. The value of the temperature is consistent with recent ASCA measurements and is significantly higher than previous estimates obtained from ROSAT and EXOSAT . We discuss the possible reasons for this disagreement. Between 8 and 20 arcmin, the plasma temperature declines to about 3.2 keV. When a polytropic profile is used to represent the gas temperature profile, the best-fitting polytropic index is 1.16±0.03. These results imply a total mass within the virial radius of between 40 and 80 per cent lower than the optical estimate, and a gas mass fraction of about 30 per cent.     

从KARST到FAST---中国天眼的概念起源与决策过程

在大科学时代,大科学工程的建设日益复杂,设计者需综合考虑设备性能、技术储备、经费、风险、环境等因素才能进行合理决策.在国内外天文学发展的背景中,梳理了500 m口径球面射电望远镜(Five-hundredmeter Aperture Spherical radio Telescope, FAST)概念形成的过程以及FAST团队在其中所做的决策,包括大望远镜中国方案的设想、先导单元的提出、主动反射面技术的采用等,并对决策过程进行了分析探讨. FAST诞生于我国与国际天文学发展的互动与融合进程,实现了从跟进到占据先机的转变,可为在相关基础薄弱的领域建设大科学工程提供参考.     

Coronal type II bursts and interplanetary type II bursts: Distinct shock drivers

We study solar radio type II bursts combining with Wind/WAVES type II bursts and coronal mass ejections (CMEs). The aim of the present work is to investigate the effectiveness of shocks to cause type II bursts in the solar corona and the interplanetary space. We consider the following findings. The distribution of the cessation heights of type II emission is confined to a rather narrow range of height than the distribution of the heights of start frequencies. This is suggestive of the presence of a gradient for the Alfvén speed from the heliocentric height of ∼1.4 solar radii. The range of the kinetic energy of CMEs associated with coronal type II emission taken together with the suggested computation method and the Alfvén speed gradient, indicates the limit to the height up to which type II emission could be expected. This height is ∼2 solar radii from the center of the Sun. Further, the large time gap between the cessation time and heights of coronal type II emission and the commencement time and heights of most of the IP type II bursts do not account for the difference between the two heights and the average shock speed. Also, there is clear difference in the magnitude of the kinetic energies and the distinct characteristics of the CMEs associated with coronal and IP type II bursts. Hence, we suggest that in most instances the coronal type II bursts and IP type II bursts occur due to distinct shocks. We also address the question of the origin of type II bursts and discuss the possible explanation of observed results.     

Jovian satellite-satellite eclipses and occultations

Toward the end of 1973 and in the first part of 1974, when the planes of the orbits of the four large Galilean satellites cross the Sun and the Earth, satellite-satellite eclipses and occultations will occur. Calculations indicate that during this period 350 such events will occur, most of them potentially observable. From observation of a few of these events the ephemerides of the satellites can be improved, radii and limb darkening curves determined, and crude information about the degree and extent of albedo fluctuations deduced. If a concerted effort were made and a large fraction of these events carefully observed it would be possible to invert the light curves to obtain albedo maps of most of the surface area at a typical resolution of about 100km for JI and JII and somewhat poorer for JIII and JIV. In 1979—the next opportunity—there will be considerably fewer events, and only a relative few of them will be observable at night.     

Stars and substars nearest to the Sun: A study review

The structure of the solar neighborhood and its position in the galaxy, including the galactocentric distances, are analyzed. Catalogues are examined of near-sun stars and substars, which are compiled from ground and space based observations in the optical and infrared spectral regions. The problem of classifying celestial bodies in the galaxy by astrophysical and cosmogonic criteria is discussed. The problem of determining the main characteristics of the nearest stars and substars is analyzed. The statistical relationships are investigated between the main characteristics of stars and substars on the basis of their physical evolutionary models. The physical sense of these relationships is discussed. The calculated differential distribution functions of the astrophysical properties of stars and substars are examined.     

Application of KS-transformation in the problem of investigation of the motion of unusual minor planets and comets

A review is presented of the author's results on application of regularizing and stabilizing KS- transformation in the problem of investigation of the motion of unusual minor planets and comets. Two models of the motion of a minor body are considered, viz. the perturbed two body problem and the perturbed restricted three body problem. The variational equations in KS-variables and transformations for obtaining the matrix of partial derivatives of the instantaneous physical parameters of motion with respect to their initial values are presented. The peculiarities of the implementation of the algorithms developed as programs on a computer are described. The original results of the investigation of the efficiency of the developed algorithms and programs are discussed using as an example the motion of unusual minor planets Icarus and Geographos as well as comets Halley, Honda-Mrkos-Pajdusakova and Gehrels 3.     

Implications of the Sample Rate on Large Space Telescopes

The frequency at which a large space telescope's (e.g. JWST's) detector chips are read, or the sample rate, is tightly coupled to many hardware and operational aspects of the telescope's instrument and data handling elements. In this paper we discuss many of the drivers and important implications of the sample rate: the data rate to the ground; onboard computer storage, bandwidth, and speed; the number of A→D chips, and therefore the overall size and power requirements of the analog electronics; cryocabling requirements; and detector noise and power. We discuss and parametrize these and other elements related to sample rate. Finally, we discuss the implications of sample rate in the context of achieving the most important science goals under the constraint of limited cost. This revised version was published online in July 2006 with corrections to the Cover Date.     

First Results from SOHO

SOHO, the Solar and Heliospheric Observatory, is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona, and the solar wind. Three helioseismology instruments are providing unique data for the study of the structure and dynamics of the solar interior, from the very deep core to the outermost layers of the convection zone. A set of five complementary remote sensing instruments, consisting of EUV, UV and visible light imagers, spectrographs and coronagraphs, give us our first comprehensive view of the outer solar atmosphere and corona, leading to a better understanding of the enigmatic coronal heating and solar wind acceleration processes. Finally, three experiments complement the remote sensing observations by making in- situ measurements of the composition and energy of the solar wind and charged energetic particles, and another instrument maps the neutral hydrogen in the heliosphere and its dynamic change by the solar wind. This paper reports some of the first results from the SOHO mission. This revised version was published online in July 2006 with corrections to the Cover Date.     

Scientific Analysis within SEPServer – New Perspectives in Solar Energetic Particle Research: The Case Study of the 13 July 2005 Event

Solar energetic particle (SEP) events are a key ingredient of solar?Cterrestrial physics both for fundamental research and space weather applications. Multi-satellite observations are an important and incompletely exploited tool for studying the acceleration and the coronal and interplanetary propagation of the particles. While STEREO uses for this diagnostic two identical sets of instrumentation, there are many earlier observations carried out with different spacecraft. It is the aim of the SEPServer project to make these data and analysis tools available to a broad user community. The consortium will carry out data-driven analysis and simulation-based data analysis capable of deconvolving the effects of interplanetary transport and solar injection from SEP observations, and will compare the results with the electromagnetic signatures. The tools and results will be provided on the web server of the project in order to facilitate further analysis by the research community. This paper describes the data products and analysis strategies with one specific event, the case study of 13 July 2005. The release time of protons and electrons are derived using data-driven and simulation-based analyses, and compared with hard X-ray and radio signatures. The interconnection of the experimental and the simulation-based results are discussed in detail.     

Ringlet–satellite interactions

We study the interaction of a satellite and a nearby ringlet on eccentric and inclined orbits. Secular torques originate from mean motion resonances and the secular interaction potential which represents the m  = 1 global modes of the ring. The torques act on the relative eccentricity and inclination. The resonances damp the relative eccentricity. The inclination instability owing to the resonances is turned off by a finite differential eccentricity of the order of 0.27 for nearly coplanar systems. The secular potential torque damps the eccentricity and inclination and does not affect the relative semi-major axis; also, it suppresses the inclination instability that persists at small differential eccentricities. The damping of the relative eccentricity and inclination forces an initially circular and planar small mass ringlet to reach the eccentricity and inclination of the satellite. When the planet is oblate, the interaction of the satellite damps the proper precession of a small mass ringlet so that it precesses at the satellite's rate independently of their relative distance. The oblateness of the primary modifies the long-term eccentricity and inclination magnitudes and introduces a constant shift in the apsidal and nodal lines of the ringlet with respect to those of the satellite. These results are applied to Saturn's F-ring, which orbits between the moons Prometheus and Pandora.