The supernova fragmentation model of solar system formation

We have further developed Brown's model of solar system formation. In this model, each fragment of an ejected supernova shell evolves into a separate solar system. Specifically, we have formulated the reverse-flow hypothesis that may be responsible for the inner, earthlike planets. We have written a computer program with which it is possible to calculate mass distributions within a solar nebula. We have found mass distributions similar to our solar system over a wide range of the model parameters.Los Alamos National Laboratory is operated by the University of California for the U.S. Dept. of Energy under contract W-7405-ENG-36.     

Consequences of tidal interaction between disks and orbiting protoplanets for the evolution of multi-planet systems with architecture resembling that of Kepler 444

We study orbital evolution of multi-planet systems with masses in the terrestrial planet regime induced through tidal interaction with a protoplanetary disk assuming that this is the dominant mechanism for producing orbital migration and circularization. We develop a simple analytic model for a system that maintains consecutive pairs in resonance while undergoing orbital circularization and migration. This model enables migration times for each planet to be estimated once planet masses, circularization times and the migration time for the innermost planet are specified. We applied it to a system with the current architecture of Kepler 444 adopting a simple protoplanetary disk model and planet masses that yield migration times inversely proportional to the planet mass, as expected if they result from torques due to tidal interaction with the protoplanetary disk. Furthermore the evolution time for the system as a whole is comparable to current protoplanetary disk lifetimes. In addition we have performed a number of numerical simulations with input data obtained from this model. These indicate that although the analytic model is inexact, relatively small corrections to the estimated migration rates yield systems for which period ratios vary by a minimal extent. Because of relatively large deviations from exact resonance in the observed system of up to 2 %, the migration times obtained in this way indicate only weak convergent migration such that a system for which the planets did not interact would contract by only \({\sim }1\,\%\) although undergoing significant inward migration as a whole. We have also performed additional simulations to investigate conditions under which the system could undergo significant convergent migration before reaching its final state. These indicate that migration times have to be significantly shorter and resonances between planet pairs significantly closer during such an evolutionary phase. Relative migration rates would then have to decrease allowing period ratios to increase to become more distant from resonances as the system approached its final state in the inner regions of the protoplanetary disk.     

大质量双星系统的非守恒演化

由于大质量双星系统有强大的星风物质损失,因而在研究其结构和演化时必须考虑星风物质损失,动量损失,物质交换以及由以上原因引起的轨道参量的变化,此外,天文观测又证实,一些大质量双星系统中存在星风冲击波,有Ｘ射线辐射以及有致密天体（白矮星,中子星）的存在,因此在研究大质量双星的演化时,又会遇到在星风冲击波理论及其对演化的影响,双星系统何时会演化成为公共外壳的系统,以及双星系统中如果发生超新星爆发,是否会     

IPS observations at stelab for the fruitful coming decade

We have been carrying out solar wind measurements using the interplanetary scintillation (IPS) method. Our IPS observation system is operated at a frequency of 327MHz and consists of four stations located at Toyokawa, Fuji, Sugadaira and Kiso. The present system, however, has insufficient sensitivity to measure enough IPS sources for observing the solar wind with adequate spatial and temporal resolution. Therefore we have been excuting the upgrade project since 1994 in order to observe a larger number of compact radio sources. The Fuji system has been improved successfully and has achieved sensitivity by a factor over five compared with the previous system. The upgrade project is now in progress for the Toyokawa and Sugadaira station.     

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.     

MHD instability due to non-homogeneity and non-uniformity of magnetic field in gravitating medium and its consequences in the central region of galaxies

The MHD wave instabilities due to non-uniform magnetic field and non-homogeneity of density have been studied. The reference (coordinate) system considered here is cylindrical type. The General Dispersion Relation (GDR) for the wave propagation in a gravitating but non-relativistic region has been derived. Similar to common knowledge, the said non-uniformities have been found to be responsible for the instability of the system. But interestingly many instability factors are produced due to presence of two types of non-uniformities simultaneously. This theory may add more clues for the event of instabilities, formation of hot plasma-bed in Galactic Central Region, and mass out-flow from there. Many conditions for instabilities could be obtained from GDR deduced here. However, a few conditions for critical wavelength of the MHD wave have been obtained in terms of system parameters (like gradient of magnetic field and rotation). This theory, in turn, may be helpful for the better understanding of the Explosion Theory of formation of outer structure of Galaxies like ours.     

Dynamics and Control for a Small Telescope

Our main goal is to determine the dynamic equations of a certain complex system, as is the case of the mechanical system for a small aperture telescope. Causes of this complexity are: the lack of documents about the operation of the elements belonging to the system, and the variation of dynamics with respect to the time and the position of the telescope. To check that we have obtained a valid set of dynamic equations, we will design a computer control system that will implement a self-guide system for the telescope. This revised version was published online in July 2006 with corrections to the Cover Date.     

Precision sidereal tracking system for a telescope

For the opportunities of CCD observations to be pursued, we have produced a precision system for telescope sidereal tracking. Using the software and hardware complex, one can control the system both autonomously and via a personal computer.     

Coriolis forces in numerical integration of satellite orbits,and absolute reference system

The reference system defined by Veis and currently used for computing satellite orbits is not sufficiently accurate for some scientific applications, considering the new accuracy of laser data. We have therefore defined another orbital reference system with associated apparent forces. The reference system chosen is the mean celestial system 1970.0. The motion of a satellite is numerically integrated in the instantaneous celestial system (sideral system), taking into account all the complementary forces due to precession and nutation. The complete set of formulas is given here and has been introduced in a differential orbital improvement program.     

乌鲁木齐天文站脉冲星观测研究新进展

乌鲁木齐天文站自 1 999年研制完成 1 .5GHz频段室温双偏振消色散接收系统。 2 0 0 2年又完成 1 .5GHz频段致冷式双偏振消色散接收系统。我们成功地完成了第一个国际合作协议的任务。为在我国建立高灵敏度的观测脉冲星设备和取得优秀的脉冲星观测结果作出了贡献。为了进一步发展乌站脉冲星观测 ,第二个合作协议包括利用致冷式系统进行脉冲星大样本的监测和建立低频段的基带技术的消色散系统。     

Capturing near earth objects

Recently,Near Earth Objects(NEOs) have been attracting great attention,and thousands of NEOs have been found to date.This paper examines the NEOs' orbital dynamics using the framework of an accurate solar system model and a Sun-Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits.It is possible for such an NEO to be temporarily captured by Earth;its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity.From the point of view of the Sun-Earth-NEO restricted three-body system,it is possible for an NEO whose Jacobian constant is slightly lower than C1 but higher than C3 to be temporarily captured by Earth.When such an NEO approaches Earth,it is possible to change its orbital energy to nearly the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth.Some such NEOs were found;the best example only required a 410 m s-1 increase in velocity.     

Stability of Binary Asteroids

The stability and final outcome of a strongly interacting binary asteroid system is considered. We discuss the implications of the system transferring energy and angular momentum between rotational and translational motion while conserving the total system energy and angular momentum. Using these results we can develop a set of sufficient conditions for stability against escape and impact. These allow us to delineate several classes of final outcomes for a binary asteroid system, each of which may have implications for asteroid observations. The effects of energy dissipation on an asteroid binary system are also considered and are shown to be able to change the stability of the system against escape and impact. An example computation for the near-Earth asteroid binary 1996 FG3 is given along with a series of numerical explorations of an evolving binary system consisting of an ellipsoid and a sphere of equal mass.     

Capturing near earth objects

Recendy,Near Earth Objects (NEOs) have been attracting great attention,and thousands of NEOs have been found to date.This paper examines the NEOs'orbital dynamics using the framework of an accurate solar system model and a SunEarth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits.It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity.From the point of view of the Sun-Earth-NEO restricted three-body system,it is possible for an NEO whose Jacobian constant is slightly lower than C1 but higher than C3 to be temporarily captured by Earth.When such an NEO approaches Earth,it is possible to change its orbital energy to nearly the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth.Some such NEOs were found; the best example only required a 410 m s-1 increase in velocity.     

Loran-C系统的技术改造与发展方向

简要介绍了近两年来美国和北欧Loran-C系统的研究和技术改造,以及未来数年内的发展方向政策,美国制订了的改造计划,对Loran-C系统及设备进行结构性调整和更新改造,同时对采用新技术后的Loran-C系统的性能和长期需求作出测试与评估,北欧Loran-C系统的研究重心是如何将陆基和空基系统有效地结合起来,Loran-C系统的作为和潜在应用还有于进一步的研究和探索。     

Modelling the binary progenitor of Supernova 1993J

We have developed a detailed stellar evolution code capable of following the simultaneous evolution of both stars in a binary system, together with their orbital properties. To demonstrate the capabilities of the code, we investigate potential progenitors for the Type IIb Supernova 1993J, which is believed to have been an interacting binary system prior to its primary exploding. We use our detailed binary stellar evolution code to model this system to determine the possible range of primary and secondary masses that could have produced the observed characteristics of this system, with particular reference to the secondary. Using the luminosities and temperatures for both stars (as determined by Maund et al.) and the remaining mass of the hydrogen envelope of the primary at the time of explosion, we find that if mass transfer is 100 per cent efficient, the observations can be reproduced by a system consisting of a  15 M_⊙  primary and a  14 M_⊙  secondary in an orbit with an initial period of 2100 days. With a mass transfer efficiency of 50 per cent, a more massive system consisting of a  17 M_⊙  primary and a  16 M_⊙  secondary in an initial orbit of 2360 days is needed. We also investigate some of the uncertainties in the evolution, including the effects of tidal interaction, convective overshooting and thermohaline mixing.     

中丹水平子午环DCMT光栏的自动控制

本文指出了子午环光栏自动控制系统研制的必要性，并简要介绍了控制原理．结果表明，该控制部分设计合理大大简便了操作．     

The relaxation time of a one-dimensional self-gravitating system

A computer experiment on a one-dimensional self-gravitating system is described. We attempt to observe the dynamic time required for this system to thermalize by comparing the position and velocity densities with those predicted by the microcanonical ensemble. Hohl and Broaddus (1967) have previously reported an estimate of the thermalization time which is inferred from studies of the kinetic energy covariance. We ran the system for the time which they report and find that the system has not thermalized. Furthermore, there is no evidence that the system is even proceeding towards equilibrium in the time-scale considered here. Significant changes in the distribution do occur in a short time, after which the system remains in a stationary state which is not characteristic of equilibrium.     

气球天文观测计算机测控系统设计

球栽STD总线数据采集与控制系统是为气球X射线天文观测研制的新一代计算机控制系统。它采用了多项新技术与新方法,是一个模块化的多CPU多任务并行处理系统。本文详细描述了它的结构和各种工作组态,并给出了地面实测结果。     

Nonlinear stage of instability due to local Joule-overheating in the solar active regions

The numerical solution by a computer of the system of magnetohydrodynamics equations in the one-dimensional approximation serves as the basis for studying the non-linear stage of the instability due to local Joule-overheating of zones with large values of magnetic field gradients in the active regions of the Sun. We have demonstrated the formation of a system of current layers responsible for efficient transformation of magnetic energy into Joule heat and kinetic energy of the macroscopic motion. The specific features of quasi-stationary skinning of magnetic field with gravitation have been noted.     

Stability of the system of stars,gas and magnetic fields

Linear stability of a system of stars, gas and magnetic fields under the existence of a relative motion between the stars and the gas is investigated by the use of the magnetohydrodynamic and the polytropic equations for the gas and the collisionless Boltzmann equation for the stars together with the Poisson equation. The star system is supposed to have the anisotropic Schwarzschild distribution. The critical wavenumber is calculated and it is found that the system becomes universally unstable under some conditions.