中国古历经朔数据的恢复及应用

中国元代的《授时历议》保存了44部古历的推朔参数及比验资料．借助古代朔望计算方法：1）恢复了诸历行用初年的天正经朔数值；2）修正了史载的错误数据．3）根据Meeus方法计算出经朔的理论值，并由此确定古历经朔的推步精度；4）尝试应用这些数据考察地球自转长期变化，得出日长变化为1．8ms／cy．     

《授时历》五星推步的精度研究

着重考察了《授时历》的步五星术,考校、复原了其推步方法.(1)推步了1299年木星历,并与已有研究进行比对,从而确认恢复方法的正确性.(2)得出《授时历》在1280～1650年间推步五星黄经的精度,木星、火星、土星、金星和水星的误差的绝对值平均分别为0.49°、1.91°、0.70°、2.82°和5.01°,木星、土星的精度较高.(3)指出将现代天文方法获取的《授时历》五星参数(周率、历率、度率、合应及历应)精确值代入《授时历》推步模型,木星、土星的推步精度并未提高,误差分别为1.83°和1.21°,而水星、金星和火星的误差却大幅加大,结果分别为30.04°、54.86°和10.82°.说明某些重要参数的修正并不能改善推步结果.     

《授时历》预报2012年日食

元代郭守敬等1280年编制的《授时历》是中国本土科学家研制的最后一部历法,具有极高的精度。采用其仍可预报2012年5月21日发生的日食,其预报北京地区的见食情况时食甚时刻误差4 min,食分误差为0.04。给出了《授时历》推步的1990～2050年北京的见食情况及精度,其中食甚时刻的标准偏差为103.04 min,食分的标准偏差则不低于0.33。通过考察1280～2050年间186个日食计算结果,可得出《授时历》自行用以来推步日食的误差,考虑到存在错报(不可见)和漏报因素的影响,其食甚时刻和食分的标准偏差分别不低于50.65 min和0.19;同时指出,随着行用时间的延长其推时误差也逐步放大。     

An Interpretation of the Non-Tidal Secular Variation in the Earth Rotation: the Interaction Between the Solar Wind and the Earth's Magnetosphere

The long period variation of the earth rotation is generally explained by the tidal friction. The tidal friction, however, is not the only source to influence the earth rotation in long term. In this paper, by means of the interaction between the solar wind and the magnetosphere of the earth, the additional magnetic pressure will exist in the magnetic tail due to the crowding and sparseness of the magnetic lines in the consideration of the earth rotation, which could be considered as a source of effecting the long term variation of the earth rotation. It is shown in this paper that this mechanism can produce angular deceleration of the Earth rotation in the magnitude of ω = −1.7 × 10-22 s-2. This result might be a prompt to search for other sources in the secular variation of the rate of the Earth rotation variation further in order to regulate the observed result with the theoretical one. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国古代太阳中天观测及二至点测算精度

研究了元代《授时历议))所保存的天象观测和推步资料，得出：(1)在AD1277—1280年问所作的98次太阳中天观测的时刻及地平高度的绝对值平均误差分别为2．64min和6．78′．(2)6部古历——《大衍历》、《宣明历》、《纪元历》、《统天历》、《重修大明历》和《授时历》推步BC522年前的3个冬至时刻的误差范围为0．97—3．51d；而AD435—1280年间的45个冬至时刻的绝对值平均误差则分别为9．35、10．42、5．54、2．97、5．68、3．36h．(3)古代确定的AD442—1280年间的16个二至时刻的绝对值平均误差为199．59min，其中元代的误差为27．89min．     

地球自转变化的重力效应

极移对重力测量的影响在前人的研究和工作中已得到了充分的考虑并有不同形式的改正公式。但是由于地轴转动速率变化的重力效应的量级很小,且限于以前的测量精度以及资料处理方法, 因而常常被忽略。随着重力测量精度的提高以及资料处理方法的改进, 有必要重新讨论该项影响。本文从推导地球瞬时自转极运动对地面台站重力测量值影响的公式入手, 将地球自转角速率变化的重力效应和极移的重力效应分离开来, 并对它们的量级分别作了估计。本文着重讨论自转角速率变化对重力测量的影响。用 Ｉ Ｅ Ｒ Ｓ 的日长变化序列和极移序列分别具体地计算了１９８２ ～１９９６ 年期间对武汉的重力测量值的影响, 结果表明, 自转角速率变化对武汉地区重力值的影响最大可达０ ．２５ ｍｉｃｒｏｇａｌ（ｐｅａｋ －ｔｏ － ｐｅａｋ） , 这在高精度的绝对重力测量和相对重力测量中不应再被忽略     

由南北朝以前171个月掩星记录所得到的地球自转长期变化

应用“实际可见时间段”方法研究中国古代只有日期而无观测时刻的月掩星记录,文中讨论了这些记录的真实性及其含义,由南北朝以前的58个月掩行星和113个月掩恒星记录分别得到公元1,4,5,6世纪的地球自转参数△t和ω平均值为ω=-66.8秒/世纪~2。     

Apsidal Motion in Binaries: Rotation of the Components

A sample of 51 separated binary systems with measured apsidal periods and rotational velocities of the components is examined. The ranges of the angles of inclination of the equatorial planes of the components to the orbital plane are estimated for these systems. The observed apsidal velocities can be explained by assuming that the axes of rotation of the stars are nonorthogonal to the orbital plane in roughly 47% of the systems (24 of the 51) and the rotation of the components is not synchronized with the orbital motion in roughly 59% of the systems (30 of 51). Nonorthogonality and nonsynchrony are defined as deviations from 90° and a synchronized angular velocity, respectively, at levels of 1 or more.     

在后牛顿引力理论(PPN形式)中引力常数变化对地球自转产生的效应

介绍和论述了在后牛顿引力理论(PPN形式)中在优越参考系和非优越参考系中经过参数化后引力常数变化对地球自转产生的效应,其中特别重点介绍了年周期变化的效应。此外也将理论结果同观测结果相对比。     

密近双星自转的测量和研究（Ⅰ）观测和处理结果

用相同的仪器条件在美国ＫｉｔｔＰｅａｋ国立天文台观测了一批密近双星，并用两种方法得出其自转速度，最后给出了７５个双星系统的９９个子星的自转速度，其中５４个子星是首次进行自转测量。这批高精度的自转值为研究双星的同步性和检验各种同步机制提供了可靠的观测资料。     

Rotation of the solar core from BiSON and LOWL frequency observations

Determination of the rotation of the solar core requires very accurate data on splittings for the low-degree modes which penetrate to the core, as well as for modes of higher degree to suppress the contributions from the rest of the Sun to the splittings of the low-degree modes. Here we combine low-degree data based on 32 months of observations with the BiSON network and data from the LOWL instrument. The data are analysed with a technique that specifically aims at obtaining an inference of rotation that is localized to the core. Our analysis provides what we believe is the most stringent constraint to date on the rotation of the deep solar interior.     

双星系中两子星的自转对双星轨道变化的后牛顿效应

本文利用解摄动方程的平均值法求得在PPN框架中二体自转对轨道要素产生的后牛顿效应的长期变化影响．利用这一理论对CWCep和DRVul两颗双星中两子星的自转对轨道近星点和平近点角的长期摄动的后牛顿效应做了计算。结果表明：对于两个质量较大快速自转的子星,由此所产生的后牛顿效应的摄动量是不能忽视的。     

Effects of the Triaxiality on the Rotation of Celestial Bodies: Application to the Earth,Mars and Eros

In this paper we discuss the influence of the triaxiality of a celestialbody on its free rotation, i.e. in absence of any external gravitationalperturbation. We compare the results obtained through two different analytical formalisms, one established from Andoyer variables by usingHamiltonian theory, the other one from Euler's variables by usingLagrangian equations. We also give a very accurate formulation of thepolar motion (polhody) in the case of a small amplitude of this motion.Then, we carry out a numerical integration of the problem, with aRunge–Kutta–Felberg algorithm, and for the two kinds of methods above, that we apply to three different celestial bodies considered as rigid : the Earth, Mars, and Eros. The reason of this choice is that each of this body corresponds to a more or less triaxial shape.In the case of the Earth and Mars we show the good agreement betweenanalytical and numerical determinations of the polar motion, and theamplitude of the effect related to the triaxial shape of the body, whichis far from being negligible, with some influence on the polhody of theorder of 10 cm for the Earth, and 1 m for Mars. In the case of Eros, weuse recent output data given by the NEAR probe, to determine in detailthe nature of its free rotational motion, characterized by the presence ofimportant oscillations for the Euler angles due to the particularly largetriaxial shape of the asteroid.     

Secular Effects on Orbits of Binary Stars Induced by Temporal Variation of Gravitational Constant (Case for Elliptical Orbit)

In this paper we investigate the influence of a varying gravitation constant on the orbits of celestial bodies. Regarding the eccentric anomaly as an independent variable, we find the solutions to the perturbed equations of motion. In the first order solutions, we find the secular and periodic variations in semi-major axis. For the other orbital elements only periodic variations exhibit. However in the second order solutions, the longitude of periastron and the mean longitude have secular terms. Applying the calculations to six selected binaries, we give the numerical estimations of the variations of orbits. These results are then carefully compared and discussed.     

引力常数随时间变化对双星轨道演变的长期效应(椭圆轨道情形)

给出了以偏近点角为自变量的变引力常数的摄动方程组的解.解包括轨道半长轴的长期和周期变化项,其他轨道根数在一阶解中无长期项,只有周期项.近星点经度和平经度在二阶解中显示长期项变化.给出了由于引力常数变化对双星轨道演变情况的数值估计,对结果做了讨论并给出结论.     

Size and Physical Properties of the Comet Hale–Bopp (C/1995 O1) Nucleus

This article uses fractal and correlation analysis of solar radio emission for determining the solar coronal rotation. It is clear from this analysis that radio emissions are modulated by the solar rotation. This revised version was published online in July 2006 with corrections to the Cover Date.     

The periodic variations of the core drift rate: global and zonal motions (Mitteilung des Zentralinstituts für Physik der Erde,Nr. 1746)

Toroidal zonal motions at the top of the Earth's core were computed from the observed secular variation and investigated with regard to their time dependence. Previously derived results for a pure westward drifting core could be re-examined. Additionally, the well-known 66.7 years period was found to be an oscillation of the zonal velocity field of third degree. With respect to periodic constituents, the total magnetic core-mantle coupling torque according to the zonal motions is comparable with that derived for a pure westward drifting core. Some differences in period lengthes and amplitudes do not remove previously stated differences between the spectra of the magnetic and mechanical torques on principle.     

The rotational and physical properties of the Centaur (32532) 2001 PT13

We present observations of the Centaur (32532) 2001 PT₁₃ taken between September 2000 and December 2000. A multi-wavelength lightcurve was assembled from V-, R- and J-band photometry measurements. Analysis of the lightcurve indicates that there are two peaks of slightly different brightness, a rotation period of 0.34741±0.00005 day, and a maximum photometric range of 0.18 mag. We obtained VRJHK colors (V-R=0.50±0.01, V-J=1.69±0.02, V-H=2.19±0.04, and V-K=2.30±0.04) that are consistent with the grey KBO/Centaur population. The V-R color shows no variation as a function of rotational phase; however, we cannot exclude the possibility that rotational variations are present in the R-J color. Assuming a 4% albedo, we estimate that 2001 PT₁₃ has an effective diameter of 90 km and a minimum axial ratio a/b of 1.18. We find no evidence of a coma and place an upper limit of 15 g s⁻¹ on the dust production rate.