ASTEC—the Aarhus STellar Evolution Code

The Aarhus code is the result of a long development, starting in 1974, and still ongoing. A novel feature is the integration of the computation of adiabatic oscillations for specified models as part of the code. It offers substantial flexibility in terms of microphysics and has been carefully tested for the computation of solar models. However, considerable development is still required in the treatment of nuclear reactions, diffusion and convective mixing.     

OpenOrb: Open‐source asteroid orbit computation software including statistical ranging

Abstract— We are making an open‐source asteroid orbit computation software package called OpenOrb publicly available. OpenOrb is built on a well‐established Bayesian inversion theory, which means that it is to a large part complementary to orbit‐computation packages currently available. In particular, OpenOrb is the first package that contains tools for rigorously estimating the uncertainties resulting from the inverse problem of computing orbital elements using scarce astrometry. In addition to the well‐known least‐squares method, OpenOrb also contains both Monte‐Carlo (MC) and Markov‐Chain MC (MCMC; Oszkiewicz et al. [2009]) versions of the statistical ranging method. Ranging allows the user to obtain sampled, non‐Gaussian orbital‐element probability‐density functions and is therefore optimized for cases where the amount of astrometry is scarce or spans a relatively short time interval. Ranging‐based methods have successfully been applied to a variety of different problems such as rigorous ephemeris prediction, orbital element distribution studies for transneptunian objects, the computation of invariant collision probabilities between near‐Earth objects and the Earth, detection of linkages between astrometric asteroid observations within an apparition as well as between apparitions, and in the rigorous analysis of the impact of orbital arc length and/or astrometric uncertainty on the uncertainty of the resulting orbits. Tools for making ephemeris predictions and for classifying objects based on their orbits are also available in OpenOrb. As an example, we use OpenOrb in the search for candidate retrograde and/or high‐inclination objects similar to 2008 KV₄₂ in the known population of transneptunian objects that have an observational time span shorter than 30 days.     

GPS/LEO掩星技术中Abel积分变换的奇点问题

在GPS／LEO无线电掩星反演地球大气技术中，Abel积分是反演地球大气折射指数的最常用的方法，Abel积分存在积分奇点的问题，根据这一问题讨论了解决奇异积分的几种不同的积分方法，并提出了一种直接求Abel积分变换的解析解．通过数值积分模拟计算，对比了各种不同积分方法引入了的计算误差。     

Integration of the full two-body problem by using generalized inertia integrals

A new algorithm to integrate the full two-body problem based on generalized inertia integrals is given. The computation speed is comparable to the fastest algorithm available till now which is based on spherical harmonics.     

Sur la fonction (dn/dtn) ψ (r) = f(dr/dt,d2r/dt2,…,dnr/dtn)

The modern means of computation require mathematical relations in forms which take care of the data directly furnished to the computer by observational instruments. In this communication the general relation of the nth derivative of the function (R) is given.     

Cooling of a coronal flare loop through radiation and conduction

A simple method is proposed for a computation of the cooling of coronal flare loops by radiation and conduction, for various temperatures, densities, and lengths of the loops. The relative importance of conductive and radiative losses is briefly discussed.     

Coronal emission line polarization

A discussion of a program for the computation of coronal emission line polarization is presented. The starting point is a general formulation of the scattering function for magnetic dipole transitions between any two total angular momentum levels, J J, J ± 1. Illustration of the behavior of the scattering function for different transitions is given. The integration of the scattering function over the solar disk and along the line of sight accounting for arbitrary distribution of magnetic fields as well as an inhomogeneous temperature and density structure of the corona is considered next.Sample results are presented for the numerical computation of the angle of maximum polarization and the degree of maximum polarization to be expected from idealized magnetic field configurations such as radial and dipole. A computation is included for a realistic field configuration predicted to exist at the time of the 1966 eclipse. The magnetic field input to the scattering calculation is based upon the potential field extension of photospheric magnetic fields. It is the purpose of the sample calculations to demonstrate how the measurement of emission polarization measurements can be interpreted in terms of the direction of coronal magnetic fields. Factors which lend ambiguity to such interpreations are clearly illustrated from the examples. These include the Hanle-effect depolarization and the depolarization at the Van Vleck angle.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Characteristics of oceanic impact‐induced large water waves—Re‐evaluation of the tsunami hazard

Abstract— The potential hazard of a meteorite impact in the ocean is controversial with respect to the destructive power of generated large ocean waves (tsunamis). We used numerical modeling of hypervelocity impact to investigate the generation mechanism and the characteristics of the resulting waves up to a distance of 100–150 projectile radii. The wave signal is primarily controlled by the ratio between projectile diameter and water depth, and can be roughly classified into deep‐water and shallow‐water impacts. In the latter, the collapse of the crater rim results in a wave signal similar to solitary waves, which propagate and decay in agreement with shallow‐water wave theory. The much more likely scenario for an asteroid impact on Earth is a relatively small body (much smaller than the water depth) striking the deep sea. In this case, the collapse of the transient crater results in a significantly different and much more complex wave signal that is characterized by strong nonlinear behavior. We found that such waves decay much more rapidly than previously assumed and cannot be treated as long waves. For this reason, the shallow‐water theory is not applicable for the computation of wave propagation, and more complex models (full solution of the Boussinesq equations) are required.     

Recovery of the Long Lost Minor Planet (843) Nicolaia after 65 Years (Astronomisches Rechen-Institut Heidelberg – Mitteilungen Serie B)

The long lost minor planet (843) Nicolaia was recovered with the 1 m ESO Schmidt telescope after 65 years. This was due to the careful examination of the old 1916 plates and the wellbalanced computation of search ephemerides. An improved orbit based on 19 right ascensions and 20 declinations from the two apparitions 1916 and 1981 is given.     

Joint computation of aerodynamic and radiation forces acting on spacecraft

A methodology is presented for the joint computation of aerodynamic and radiation forces acting on orbital spacecraft. Special attention is given to the computation of the radiation component. The reliability of the results is confirmed by comparing them with those obtained by other methods and flight measurements. Results are presented of a study of the combined impact induced by solar radiation and the upper atmosphere on the small spacecraft MKAFKI (Zond-PP).     

Concerning the compatibility of an Archimedes'' spiral interplanetary magnetic field with the presence of interstellar neutral hydrogen in the solar cavity

A self-consistent computation of the interplanetary magnetic field is presented which takes into account the effects of interstellar particles newly ionised on entering the solar cavity. The resulting field differs infinitesimally from the Parker spiral for all reasonable parameters and is in agreement with recent observations on board Pioneer 10.     

Computation of the elements of eclipsing binaries from a part of their light curves

All methods existing today for computation of the elements of eclipsing binaries require photometric observations to cover the complete revolution of binaries, outside as well as within the eclipses. The maximum light and the depth of the eclipses are to be determined prior to any analysis, and the light curves are to be expressed in terms of the total light at quadratures. A method has been introduced in the present paper to enable us to obtain the elements of eclipsing binaries by an analysis of, not the whole, but a part of their eclipse light curves. In the new method no empirical knowledge of the maximum light or depth of eclipes is needed, and no normalization is necessary. The method can be used in any models (ellipsoidal, Roche, etc.). However, the larger the phase coverage of the light changes considered for the computation of the elements, the better the determinacy (or smaller the errors) is obtained.     

Asteroid orbital ranging using Markov‐Chain Monte Carlo

Abstract— We present a novel Markov‐Chain Monte‐Carlo orbital ranging method (MCMC) for poorly observed single‐apparition asteroids with two or more observations. We examine the Bayesian a posteriori probability density of the orbital elements using methods that map a volume of orbits in the orbital‐element phase space. In particular, we use the MCMC method to sample the phase space in an unbiased way. We study the speed of convergence and also the efficiency of the new method for the initial orbit computation problem. We present the results of the MCMC ranging method applied to three objects from different dynamical groups. We conclude that the method is applicable to initial orbit computation for near‐Earth, main‐belt, and transneptunian objects.     

Computation of the lowest eigenvalue arising from the problem of stellar stability by the method of Schwartz iteration

The Schwartz iteration procedure is used to compute the lowest eigenvalue from the equation for radial oscillations of stars. It was found that the convergence of the iteration had an oscillating convergence. This made it unsuitable for the computation of the higher eigenvalues. A series of associated Laguerre functions is suggested as a method of obtaining better results.Formerly at the University of Manchester, England     

A method of computing the gravitational field of an axially symmetric flat galaxy

A method has been developed for computing the gravitational force field of an axially symmetric flat galaxy from its surface mass density. The method is simple to program, fast, and accurate. An inversion formula is derived that allows computation of surface density from rotation curves by use of any method that converts density to force. The method is compared with a method of Clutton-Brock that utilizes Hankel transforms of Laguerre functions.     

Numerical investigation of the orbit of Interball‐1

We investigated the motion of the Earth's artificial satellite Interball‐1 by using a method suitable for the computation of large eccentricity orbits. Though the measured and the computed orbital elements differ from each other within the measured error bound, we found a slight tendency for secular decreasing in the semi‐major axis, caused probably by electromagnetic drag. We analysed the dominant role of the Moon in the variations of the orbital eccentricity, leading to zero perigee height and the end of the lifetime of the satellite. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Computation of convective model atmospheres of cool white dwarfs

It is shown that, in constructing model atmospheres of cool white dwarfs with strong convection, the computation of the radiative flux can be omitted in a number of iterations. This does not increase the number of iterations needed to obtain convergent model and, consequently, saves computation time.     

Direct Calculation Methods of Hansen Coefficients and Their Derivatives

Seven direct calculation methods of Hansen coefficients and their derivatives are reviewed. The computational efficiencies of these methods are compared, and their computational stabilities are analyzed. We show that the recursion relations of Hansen coefficients can be used to determine the stabilities of calculation results. Finally, it is pointed out that Wnuk's method (double precision computation) and McClain's methods (quadruple precision computation) are stable, which can be used to calculate orbit perturbations. Because of small orbital eccentricities of most satellites, the perturbation calculations without singularities are required, and McClain's first method (quadruple precision computation) is recommended.     

Carbon deflagration supernova,an alternative to carbon detonation

As an alternative to the carbon detonation, we present a carbondeflagration supernova model by a full hydrodynamic computation. A deflagration wave, which propagates through the core due to convective heat transport, does not grow into detonation. Though it results in a complete disruption of the star, the difficulty of overproduction of iron peak elements can be avoided if the deflagration is relatively slow.     

Hansen系数及其导数的直接计算方法

回顾总结了7种Hansen系数及其导数的直接计算方法,比较分析了这些方法的计算效率和计算稳定性.研究表明:Hansen系数的递推关系可以用来判别计算结果的稳定性.最后指出, Wnuk方法(双精度计算)和McClain方法(4精度计算)是稳定的,可以用来计算人造卫星轨道摄动.由于大多数人造卫星采用小偏心率轨道,需要计算无奇点摄动,推荐使用McClain方法1 (4精度计算).