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1.
经典造父变星的银河系运动学研究 总被引：2，自引：0，他引：2
利用视向速度资料和依巴谷星表的自行资料,研究了经典造父变星的银河系运动学问题。采用Ｏｇｏｒｏｄｎｉｋｏｖ－Ｍｉｌｎｅ三维运动学模型,获得银河系旋转速度Ｖ０＝２４０．５±１０．２ｋｍ／ｓ（取太阳至银心距离为８．５ｋｐｃ）。同时发现,在太阳附近沿银河系旋转方向存在一种收缩运动,其值（δＶθ／δθ）／Ｒ＝－２．６０±１．０７ｋｍ ｓ＾－１ｋｐｃ＾－１。本分析了产生这种收缩运动的原因。另外,得出太阳运动 相似文献
2.
朱紫 《中国天文和天体物理学报》1999,(3)
利用视向速度资料和依巴谷星表的自行资料,研究了经典造父变星的银河系运动学问题．采用Ｏｇｏｒｏｄｎｉｋｏｖ－Ｍｉlnｅ三维运动学模型,获得银河系旋转速度Ｖ０＝２４０．５±１０．２ｋｍ／ｓ（取太阳至银心距离为８．５ｋｐｃ）同时发现,在太阳附近沿银河系旋转方向存在一种收缩运动,其值((V(/(()／Ｒ＝－２．６０±１．０７ｋｍｓ－１kｐｃ－１．本文分析了产生这种收缩运动的原因．另外,得出太阳运动速度Ｓ＝１８．７±０．８６ｋｍ／ｓ向点＝５４．４°±２．９°＝＋２６．６°±２．６° 相似文献
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利用 2 0 2个太阳附近疏散星团的视向速度和自行观测资料 ,对太阳的运动和银河系的运动学参数进行了研究。其中 ,距离在 0 .5kpc到 2kpc之间的 12 8个疏散星团对平均太阳运动分量的解算结果是 (u0 ,v0 ,w0 ) =(- 13.8± 1.4 ,- 5 .0± 1.6 ,- 11.6± 2 .9)km/s ;Oort常数和银河系径向运动参数的解算结果分别为 (A ,B) =(16 .9± 1.1,- 11.6± 2 .6 )km·s- 1·kpc- 1及 (C ,D) =(2 .5± 1.1,- 2 .1± 0 .9)km·s- 1·kpc- 1。 相似文献
4.
直接测量恒星形成区的距离;从而确定银河系的旋臂结构以及银河系运动学的工作正在逐步展开.通过对恒星形成区脉泽的多历元VLBI观测,利用类星体和脉泽相位参考技术,精确地测定脉泽的位置、自行和视差.精确的距离能够确定旋臂的位置,从而建立银河系旋臂结构的新模型;运用绝对自行确定该处天体的三维运动,由此精确测定银河系的旋转曲线,... 相似文献
5.
根据最近发表的新编依巴谷星表数据,重新研究了经典造父变星周光关系零点问题.利用运动学模型对自行数据和视向速度分别拟合奥尔特常数及本地静止标准的旋转速度,得到太阳的银心距R0=8.0±0.8kpc.从太阳附近的旋转曲线,发现银河系盘的引力势具有弱椭圆分布的迹象.通过-个简单的非对称模型,得到太阳附近盘引力势的椭率e(R0)=0.067±0.036,其短轴指向φb=32°±15°. 相似文献
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一、研究银河系的意义银河系是太阳所属的星系,研究它可使我们了解太阳和地球在宇宙间所占的地位,也帮助我们了解太阳和地球的过去和将来.银河系结构和动力学的研究是解决恒星的起源和演化问题的一条重要途径,尤其是银河系的次系和星族的研究,包括各个次系的结构、空间分布和运动情况、以及成员的化学组成等,对于恒星起源演化的研究提供了重要的线索.银河系的结构和动力学的详尽研究是研究河外星系及其各种集团的基础. 相似文献
11.
A method for a kinematic analysis of stellar radial velocities using spherical harmonics is proposed. This approach does not depend on the specific kinematic model and allows both low-frequency and high-frequency kinematic radial velocity components to be analyzed. The possible systematic variations of distances with coordinates on the celestial sphere that, in turn, are modeled by a linear combination of spherical harmonics are taken into account. Theoretical relations showing how the coefficients of the decomposition of distances affect the coefficients of the decomposition of the radial velocities themselves have been derived. It is shown that the larger the mean distance to the sample of stars being analyzed, the greater the shift in the solar apex coordinates, while the shifts in the Oort parameter A are determined mainly by the ratio of the second zonal harmonic coefficient to the mean distance to the stars, i.e., by the degree of flattening of the spatial distribution of stars toward the Galactic plane. The distances to the stars for which radial velocity estimates are available in the CRVAD-2 catalog have been decomposed into spherical harmonics, and the existing variations of distances with coordinates are shown to exert no noticeable influence on both the solar motion components and the estimates of the Oort parameter A, because the stars from this catalog are comparatively close to the Sun (no farther than 500 pc). In addition, a kinematic component that has no explanation in terms of the three-dimensional Ogorodnikov-Milne model is shown to be detected in the stellar radial velocities, as in the case of stellar proper motions. 相似文献
12.
A method for determining the velocity field parameters free from the distortions due to the systematic variations of stellar parallaxes over the celestial sphere is proposed. The method is based on the approximation of parallaxes as a function of coordinates on the sphere using spherical harmonics and can be applied in those cases where the solar motion cannot be eliminated from the stellar proper motions. Numerical experiments have shown that our method is able to obtain accurate coordinates of the solar apex and to calculate the kinematic parameters of the Ogorodnikov-Milne model to within three coefficients of the decomposition of parallaxes into first-order spherical harmonics. Examples of applying the method to the stellar proper motions of the Hipparcos catalogue, which admits checking the results using trigonometric parallaxes, are provided. Such a check has been found to yield a positive result only for nearby stars at heliocentric distances that do not exceed 400 pc and for which the parallaxes were determined with a relative error of at least 30%. An interesting feature of this method is the possibility to construct the shape of the figure which is formed by the deviations of the parallaxes from the sphere corresponding to the average parallaxes of the stars under consideration. It should be specially emphasized that all of this is done in the complete absence of information about the stellar parallaxes. The “solar terms” of the stellar proper motions that are formed by the products of the parallaxes by the solar motion components relative to the centroid of stars are the main source of information about the parallaxes here. 相似文献
13.
A fine structure related to the kinematic peculiarities of three components of the Scorpius-Centaurus association (LCC, UCL, and US) has been revealed in the UV-velocity distribution of Gould Belt stars. We have been able to identify the most likely members of these groups by applying the method of analyzing the two-dimensional probability density function of stellar UV velocities that we developed. A kinematic analysis of the identified structural components has shown that, in general, the center-of-mass motion of the LCC, UCL, and US groups follows the motion characteristic of the Gould Belt, notably its expansion. The entire Scorpius-Centaurus complex is shown to possess a proper expansion with an angular velocity parameter of 46 ± 8 km s?1 kpc?1 for the kinematic center with l 0 = ?40° and R 0 = 110 pc found. Based on this velocity, we have estimated the characteristic expansion time of the complex to be 21 ± 4 Myr. The proper rotation velocity of the Scorpius-Centaurus complex is lower in magnitude, is determined less reliably, and depends markedly on the data quality. 相似文献
14.
On the basis of the possibility of sight-line velocity observations by a special equatorial solar spectrograph, a research programme for detection of photospheric large-scale velocities has been initiated. The first series of observations in the FeI 6302 Å absorption line has been limited to the central meridian.The combined limb effect assumed to incorporate an unresolved stationary photospheric motion, has been evaluated. The observed asymmetry of the obtained curve is mainly explained by dB
0/dt.The remaining sight-line velocities along the central meridian, taken as random, gave an r.m.s. value of 32 m s–1. In a few cases a certain kinematic situation in some areas along the central meridian lasted for 2 to 4 consecutive days. It is assumed that such velocity features belong to the kinematic picture of a large-scale photospheric motion which, as a whole, has not yet been clearly seen. 相似文献
15.
Two kinematic models of line-tied reconnection are considered which describe the motion of a magnetic neutral line (NL) during the main phase of a two-ribbon solar flare and during the recovery phase of a magnetospheric substorm in the geomagnetic tail. The models are kinematic in that they use only the magnetic induction equation, which suffices to determine the position and velocity of the NL as functions of time if the rate of reconnection is prescribed. The solar flare model shows that the observed large decrease in the rate at which “post”-flare loops rise upward from the photosphere during the main phase does not require a corresponding decrease in the rate of reconnection. Instead it is found that a constant rate of reconnection can account for the motion of the loops for almost the entire period during which they are observed. By contrast, application of the same procedures to the recovery phase of the magnetospheric substorm in the tail predicts a slightly increasing speed of NL motion if the rate of reconnection is constant. Furthermore, it is found that the motion of the NL relative to the ambient medium may account for much of the observed asymmetry in the magnetic field in the plasma sheet during recovery. Due to this motion, the plasma sheet thickness may be up to 4 times smaller and the normal magnetic field component up to 2 times weaker in the region tailward of the NL than in the corresponding region earthward of the NL. 相似文献
16.
In the following paper we argue that each wind-driving star in relative motion with respect to the ambient interstellar medium experiences a force exerted on its central wind-generating body. The exact magnitude of this force depends on the actual geometry of the counterflow configuration of stellar and interstellar winds for a particular kinematic situation which is especially sensitive to whether the interstellar flow is subsonic or supersonic. It will, however, be demonstrated here that this force is of an accelerating nature, i.e., it operates like a rocket-motor, as long as the peculiar motion of the wind-driving star with respect to the ambient interstellar medium remains subsonic.Here we use a specific analytical model to describe theoretically the specific counterflow configuration for the case of the solar system in a subsonic peculiar motion with respect to the local interstellar medium assuming irrotational and incompressible flows. We can work out a quantitative number for the accelerating force governing the Sun's motion at present. The net reaction force exerted on the solar body is then mediated by the asymmetric boundary conditions to which the distant solar wind field has to adapt.Next we study the indirect action of such a force on orbiting Keplerian objects like planets, planetesimals and comets. Since this force only influences the central solar body, but not the planets themselves, the problem is different from the treatment of a constant perturbation force perturbing the Keplerian orbits. We present a perturbation analysis treating the action of a corresponding position-dependent perturbation force resulting in secular changes of the orbital elements of Keplerian objects. It is found that changes are accumulating more rapidly in time the closer to the sun the orbiting bodies are. Main axis and perihelion distances are systematically increasing. Especially pronounced are changes in the perihelion position angle of the objects. For solar wind mass losses larger than the Sun's present value by a factor of 1000 (T-Tauri phase of the Sun,) the migration periods calculated for the planet Mercury are of the same order of magnitude as that for corresponding general relativistic migration. 相似文献
17.
Michael E. Hough 《Celestial Mechanics and Dynamical Astronomy》1995,62(3):263-287
A new integration theory is formulated for dynamical systems with two degrees of freedom, in the gravitational field of a rotating system. Four integrals of motion may be determined from complete solutions of a system of three first-order, partial differential equations in three independent variables. The solutions of this system define two integral surfaces with space-time coordinates. These surfaces represent two independent solutions of a second-order kinematic system to which the original fourth-order system has been reduced. An integral curve may be represented as the locus of intersection points of the integral surfaces. The new theory is the theoretical basis for a method of analytic continuation of periodic orbits of the circular restricted problem. 相似文献
18.
Jun LinHarvard-Smithsonian Center for Astrophysics Garden Street Cambridge MA USA 《中国天文和天体物理学报》2002,2(6)
Based on previous work, we investigate the propagation of CMEs in a more realistic plasma environment than the isothermal atmosphere, and find that it is a slightly faster reconnection for flux ropes to break free. The average Alfven Mach number MA for the inflow into the reconnection site has to be at least 0.013 in order to give a plausible eruption (compared to MA = 0.005 for the isothermal atmosphere). Taking MA = 0.1, we find that the energy output and the electric field induced inside the current sheet match the temporal behavior inferred from the energetic, long duration, CME-associated X-ray events. The results indicate that catastrophic loss of equilibrium in the coronal magnetic field provides the most promising mechanism for major solar eruptions, and that the more energetic the eruption is, the earlier the associated flare peaks. The variation of the output power with the background field strength revealed by our calculations implies the poor correlation between slow CMEs and solar flares. Th 相似文献
19.
Kinematics of local magnetic features (LMFs) have been investigated by analyzing a 22-year series of synoptic maps of the
radial magnetic field of the Sun (the term ‘local’ refers hereinafter to magnetic features with an effective size of the order
of an arc min). We applied the cross-correlation technique to analyse separately each of the harmonics obtained by using a
one-dimensional Fourier transform of the magnetic field in longitude. Such an approach allowed us to trace the motion of the
LMFs for a time interval as long as 12 Carrington rotations. The analysis also has shown that the effective size of the magnetic
tracers grows significantly with increasing age, which indicates that the local-scale magnetic features undergo diffusion-like
expansion and weakening, in agreement with Leighton's model of magnetic field evolution.
The LMFs emerging at latitudes between 10° and 55° reveal a poleward directed motion with a maximum velocity of about 14 m
s-1 near the latitude of 37°. The profile of the meridional velocity agrees approximately with that derived by Komm, Howard,
and Harvey (1993) for small-scale, short-lived magnetic features.
We have found that the LMFs rotate differentially at latitudes of up to 55°, and do not exhibit the ‘quasi-rigid’ rotation
that is assumed to be characteristic of long-lived magnetic features. This disagrees with the results obtained by Stenflo
(1989) and by Latushko (1994), who applied direct cross-correlation analysis of the synoptic maps. Such a discrepancy may
be treated as being a consequence of inhomogeneity of the large-scale solar magnetic field that consists of several components
with different kinematic characteristics. 相似文献
20.
Using the H-alpha solar filtergrams taken at Kandilli Observatory, we have studied the motion of a twisted surge, from the kinematic point of view. We applied the Palu (1972) method to two knots of the twisted surge occurred at 10 November, 1967. The results are discussed. 相似文献