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1.
谭徽松 《中国天文和天体物理学报》1986,(2)
用美国McDonald天文台2.1米反射镜的折轴Reticon观测HeI 5875谱线,由标准星的观测轮廓与Gray的转致轮廓卷积后同被测星的观测轮廓进行拟合,测得了18颗双星的Vsini,并结合以前测得的20个双星系统的结果,同Slettebak老系统进行了比较,得到了它们的近似关系:在Vsini<100 kms~(-1)时,两者的值比较一致;当Vsini>100kms~(-1)时,本方法得出的值明显偏低。这一关系间接说明,我们的结果与Slettebak新系统的趋势是一致的。 相似文献
2.
本文对谭徽松等人提出的一种自转测量方法改进成完全数字化。即把自转标准星序列存入计算机内,对每个被测星,通过调整四个参量:强度标度K,自转速度Vsini,临边昏暗系数ε,沿波长方向的平移量S,得到被测星的自转速度。和原来方法比较,其主要优点是:(1)节省计算机、绘图仪的时间和人力;(2)对测量值和误差估计减少人差;(3)同时可测得视向速度,有可能得到临边昏暗系数和元素丰度。 相似文献
3.
基于彭秋和等1978年得到的无扰动有限厚盘引力势,根据两个引力势参数(h_(z1)= 0．001kpc,h_(z2)=0．325 kpc)和两个速度分布参数(σ_(v1)=115km/s,σ_(v2)=200 km/s)组合的4种情况,对4×10~5颗脉冲星做了三维蒙特卡洛模拟．4×10~5颗脉冲星按着10~8年间隔被分成20组,计算了每组“逃逸”脉冲星所占比例．对每组中“未逃逸”脉冲星,分别在0＜r＜25kpc和5＜r＜11kpc两个区域中对|z|分布做了统计,研究了“未逃逸”脉冲星在这两个区域中的分段标高和累积标高的演化特征．“未逃逸”脉冲星的分段标高在一定空间范围内的变化不规则,但累积标高的变化却比较平滑．在相对长的时间里(＞10~8年),银盘厚度对脉冲星累积标高演化有显著的复杂影响；在相对短的时间中(＜2×10~7年),这种效应很小,而且累积标高对时间的依赖关系是线性的．在长时间里,初始速度分布对累积标高也有显著影响．在引力势h_(z2)=0．325 kpc的条件下,在径向范围5＜r＜11kpc和时间t=9．22×10~6年以及σ_(v2)=200km/s的情况下,模拟的累积标高是0．596±0．005 kpc． 相似文献
4.
应用国家天文台兴隆观测基地2.16 m望远镜及其高色散光谱仪,对6颗弱发射线T Tauri型星(Weak-line T Tauri Stars,简称WTTS)进行了高色散光谱观测,计算了这些弱发射线T Tauri型星的锂元素丰度,讨论了这些弱发射线TTauri型星锂丰度和恒星自转周期、光变幅度的关系,研究发现:自转较快的弱发射线T Tauri型星锂丰度小于自转较慢的弱发射线T Tauri型星锂丰度;但是这些弱发射线TTauri型星,其锂丰度与恒星在V波段的光变幅度并没有明显的相关性. 相似文献
5.
CS30301–015和HE1045+0226是两颗C元素和s-过程元素均超丰的贫金属(CEMP-s)星.视向速度观测发现这两颗星可能为单星.采用叠加与分解的方法探究这两颗星化学元素的天体物理来源能够为更好地理解银河系早期化学演化提供线索.计算结果表明:这两颗星的轻元素和Fe族元素主要产生于大质量星的primary过程.对于CS 30301–015,中子俘获元素主要来自AGB (Asymptotic Giant Branch)星中的主要s-过程. Pb的显著超丰主要归因于主要s-过程的贡献(约占Pb观测丰度的99.8%).需要更多的视向速度观测来确定这两颗星的轨道特征.对于HE 1045+0226, 56Z (质子数)62的重中子俘获元素主要来源于主要s-过程; Eu主要来源于主要r-过程.而轻中子俘获元素Y和Zr主要来自快速自转大质量星的primary弱s-过程,这一核合成过程对HE 1045+0226的Y和Zr丰度的贡献分别约为69.8%和67.6%.这从观测的角度证明弱s-过程能够在贫金属环境下发生. 相似文献
6.
Markarian 478是典型的窄线赛弗特I星系之一。本文展示了在 2 0 0 1年 1月利用远紫外光谱探测卫星 (FUSE)观测到的Markarian 478的远紫外光谱。我们的光谱覆盖了 91 5Å ;— 1 1 85Å的波长范围 ,分辨率约为 2 0km/s。我们在连续谱上探测到OⅥλλ1 0 3 2 ,1 0 3 8、NⅢλ989和CⅢλ977强发射线。在高电离双线OⅥ以及Lyβ的蓝端线翼上出现了成协吸收线 ,而在NⅢ和CⅢ发射线上没有出现内禀吸收线。这些吸收线被分解成 5个动力学成分 ,它们相对于系统红移zem=0 .0 774的静止坐标系速度覆盖了从 -2 3 0 0～ 3 70km/s的范围 相似文献
7.
Kepler卫星提供的长时序、高精度的光度观测和郭守敬望远镜(LAMOST)提供的大规模光谱观测为研究恒星表面转动周期与富锂巨星锂丰度关系提供了良好的数据.将LAMOST搜寻到的富锂巨星与Kepler观测交叉,获得了619颗共同源,研究了其中295颗有良好观测数据的富锂巨星的表面转动.在205颗有星震学参数的恒星中提取出14颗恒星的转动周期,其中氦核燃烧星(HeB) 11颗,红巨星支(RGB) 2颗, 1颗演化阶段未确定.本样本中的极富锂巨星(A(Li) 3.3 dex)皆为HeB;对于90颗没有星震学参数的样本因而没有依靠星震学手段确定演化阶段的恒星中,有22颗提取出了自转周期.前者的自转探测率为6.8%,显著高于之前工作中大样本巨星2.08%的探测率.同时,此研究首次从自转周期的角度确认了恒星转动与巨星锂增丰存在相关性,在增丰程度较弱时,自转周期分布比较弥散;强锂增丰的星倾向于快速转动.富锂巨星与极富锂巨星在转动速度随锂丰度的演化上展现了两个序列,在转动-锂丰度图上的A(Li)≈3.3 dex处产生第2个下降序列,或许暗示了两者在形成机制上的不同.极富锂巨星的样本中,随巨星锂增丰程度增强,恒星转速加快.这种相关性为由转动引起的额外混合作为富锂巨星形成的机制提供了支持. 相似文献
8.
吴光节 《中国天文和天体物理学报》1986,(3)
本文给出82—84年对20颗Be星的观测结果。对其发射线特征(定义了V/R、E/C、E/A_0)进行了描述。按发射线特征可将Be星简单地分为三类:单峰、双峰和在发射线中心有强的壳层吸收的星。但是,除了第三类可认为是Be壳层星外,前两类并不能简单地认为是轴向的和赤道向的Be星。单峰和双峰通常是可以相互转化的,这种转化说明Be星的外包层在变化,即HⅡ和HⅠ区的厚度在变化。并且,由观测表明,很可能同时伴随着有光球电子密度等参量的变化。本文还利用理论模型的计算结果,由氦线的半强度宽求得了恒星的自转速度v sin i,并将结果与其它文献给出的结果进行了比较和讨论。 相似文献
9.
1984年9月我们在McDonald天文台用2.1米望远镜折轴摄谱仪焦点Reticon观测了33个Rs CVn型双星的H_α区光谱。本文给出了观测结果及H_α视向速度与等值宽度(EW)的测定结果(表1)。我们首次探测到HD 8357,HD 175742和HR 7428双星的H_α发射,对此三个系统的H_α发射特征进行了重点描述。我们还发现HD 8357系统呈双谱,并测定了两颗子星的视向速度曲线,求出了两子星的质量比。λAnd,UX Ari,RT Lac,AR Lac,HK Lac和HD 185151这六个系统具有持续的或偶发的强H_α发射,对此也进行了简单的描述和分析。其余24个系统的H_α轮廓呈吸收线,但它们的等值宽度都明显地小于光谱光度型相近的标准星的,而且随时间变化。我们认为H_α发射是这类型双星的共同特性之一。 相似文献
10.
Mira变星拱星包层速度流场的二流模型 总被引：1，自引：0，他引：1
俞志尧 《中国天文和天体物理学报》1986,(4)
我们研究了Mira变星拱星包层速度流场的二流模型。根据拱星包层中尘埃颗粒及气体的连续性方程和动量方程,并假定气体的膨胀过程为多方膨胀过程,通过计算,我们分别得到尘埃颗粒及气体的速度流场、以及尘埃颗粒和气体之间的牵连速度。与观测事实比较后表明,我们得到的尘埃颗粒及气体的速度流场都与观测事实相一致。用我们得到的气体的速度流场估算了Mira变星的质量损失率为1.19×10~(-6)M_⊙/年,这也与已知的观测事实相符。 相似文献
11.
L. S. Marochnik 《Astrophysics and Space Science》1983,89(1):61-75
The solar system's position in the Galaxy is an exclusive one, since the Sun is close to the corotation circle, which is the place where the angular velocity of the galactic differential rotation is equal to that of density waves displaying as spiral arms. Each galaxy contains only one corotation circle; therefore, it is an exceptional place. In the Galaxy, the deviation of the Sun from the corotation is very small — it is equal to ΔR/R ⊙≈0.03, where ΔR=R c ?R ⊙,R c is the corotation distance from the galactic center andR ⊙ is the Sun's distance from the galactic center. The special conditions of the Sun's position in the Galaxy explain the origin of the fundamental cosmogony timescalesT 1≈4.6×109 yr,T 2?108 yr,T 3?106 yr detected by the radioactive decay of various nuclides. The timescaleT 1 (the solar system's ‘lifetime’) is the protosolar cloud lifetime in a space between the galactic spiral arms. The timescaleT 2 is the presolar cloud lifetime in a spiral arm.T 3 is a timescale of hydrodynamical processes of a cloud-wave interaction. The possibility of the natural explanation of the cosmogony timescales by the unified process (on condition that the Sun is near the state of corotation) can become an argument in favour of the fact that the nearness to the corotation is necessary for the formation of systems similar to the Solar system. If the special position of the Sun is not incidental, then the corotation circles of our Galaxy, as well as those of other galaxies, are just regions where situations similar to ours are likely to be found. 相似文献
12.
Yoshio Kubo 《Celestial Mechanics and Dynamical Astronomy》1982,26(1):97-112
Perturbations in the motion of the Moon are computed for the effect by the oblateness of the Earth and for the indirect effect of planets. Based on Delaunay's analytical solution of the main problem, the computations are performed by a method of Fourier series operation. The effect of the oblateness of the Earth is obtained to the second order, partly adopting an analytical evaluation. Both in longitude and latitude are found a few terms whose coefficient differs from the current lunar ephemeris based on Brown's theory by about 0.01. While, concerning the indirect effect of planets, several periodic terms in the current ephemeris seem to have errors reaching 0.05.As for the secular variations of
and due to the figure of the Earth and the indirect effect of planets, the newly-computed values agree within 1/cy with Brown's results reduced to the same values of the parameters. Further, the accelerations in the mean longitude,
and caused by the secular changes in the eccentricity of the Earth's orbite and in the obliquity of the ecliptic are obtained. The comparison with Brown shows an agreement within 0.3/cy2 for the former cause and 0.02/cy2 for the latter. An error is found in the argument of the principal term for the perturbations due to the ecliptic motion in the current ephemeris.Proceedings of the Conference on Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets. Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980. 相似文献
13.
E. L. Ruskol 《Earth, Moon, and Planets》1973,6(1-2):190-201
It is suggested that the overall early melting of the lunar surface is not necessary for the explanation of facts and that
the structure of highlands is more complicated than a solidified anorthositic ‘plot’. The early heating of the interior of
the Moon up to 1000K is really needed for the subsequent thermal history with the maximum melting 3.5 × 109 yr ago, to give the observed ages for mare basalts. This may be considered as an indication that the Moon during the accumulation
retained a portion of its gravitational energy converted into heat, which may occur only at rapid processes. A rapid (t < 103 yr) accretion of the Moon from the circumterrestrial swarm of small particles would give necessary temperature, but it is
not compatible with the characteristic time 108 yr of the replenishment of this swarm which is the same as the time-scale of the accumulation of the Earth. It is shown that
there were conditions in the circumterrestial swarm for the formation at a first stage of a few large protomoons. Their number
and position is evaluated from the simple formal laws of the growth of satellites in the vicinity of a planet. Such ‘systems’
of protomoons are compared with the observed multiple systems, and the conclusion is reached that there could have been not
more than 2–3 large protomoons with the Earth. The tidal evolution of protomoon orbits was short not only for the present
value of the tidal phase-lag but also for a considerably smaller value.
The coalescence of protomoons into a single Moon had to occur before the formation of the observed relief on the Moon. If
we accept the age 3.9 × 109 yr for the excavation of the Imbrium basin and ascribe the latter to the impact of an Earth satellite, this collision had
to be roughly at 30R, whereR is the radius of the Earth, because the Moon at that time had to be somewhere at this distance. Therefore, the protomoons
had to be orbiting inside 20–25R, and their coalescence had to occur more than 4.0x109 yr ago. The energy release at coalescence is equivalent to several hundred degrees and even 1000 K. The process is very rapid
(of the order of one hour). Therefore, the model is valid for the initial conditions of the Moon. 相似文献
14.
In this paper we first emphasize why it is important to know the successive zonal harmonics of the Sun's figure with high
accuracy: mainly fundamental astrometry, helioseismology, planetary motions and relativistic effects. Then we briefly comment
why the Sun appears oblate, going back to primitive definitions in order to underline some discrepancies in theories and to
emphasize again the relevant hypotheses. We propose a new theoretical approach entirely based on an expansion in terms of
Legendre's functions, including the differential rotation of the Sun at the surface. This permits linking the two first spherical
harmonic coefficients (J
2 and J
4) with the geometric parameters that can be measured on the Sun (equatorial and polar radii). We emphasize the difficulties
in inferring gravitational oblateness from visual measurements of the geometric oblateness, and more generally a dynamical
flattening. Results are given for different observed rotational laws. It is shown that the surface oblateness is surely upper
bounded by 11 milliarcsecond. As a consequence of the observed surface and sub-surface differential rotation laws, we deduce
a measure of the two first gravitational harmonics, the quadrupole and the octopole moment of the Sun: J
2=−(6.13±2.52)×10−7 if all observed data are taken into account, and respectively, J
2=−(6.84±3.75)×10−7 if only sunspot data are considered, and J
2=−(3.49±1.86)×10−7 in the case of helioseismic data alone. The value deduced from all available data for the octopole is: J
4=(2.8±2.1)×10−12. These values are compared to some others found in the literature.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005238718479 相似文献
15.
B. P. Kondratyev 《Solar System Research》2013,47(1):1-10
A two-component theoretical model of the physical libration of the Moon in longitude is constructed with account taken of the viscosity of the core. In the new version, a hydrodynamic problem of motion of a fluid filling a solid rotating shell is solved. It is found that surfaces of equal angular velocity are spherical, and a velocity field of the fluid core of the Moon is described by elementary functions. A distribution of the internal pressure in the core is found. An angular momentum exchange between the fluid core and solid mantle is described by a third-order differential equation with a right-hand side. The roots of a characteristic equation are studied and the stability of rotation is proved. A libration angle as a function of time is found using the derived solution of the differential equation. Limiting cases of infinitely large and infinitely small viscosity are considered and an effect of lag of a libration phase from a phase of action of an external moment of forces is ascertained. This makes it possible to estimate the viscosity and sizes of the lunar fluid core from data of observations. 相似文献
16.
M. V. Samokhin 《Astrophysics and Space Science》1979,62(1):159-183
In order to understand the reason of the existence of the electric field in the magnetosphere, and for the theoretical evaluation of its value, it is necessary to find the solution of the problem of determination of the magnetosphere boundary form in the frameworks of the continuum medium model which takes into account part of the magnetospheric plasma movement in supporting the magnetospheric boundary equilibrium. A number of problems for finding the distribution of the pressure, the density, the magnetic field and the electric field on the particular tangential discontinuity is considered in the case when the form of discontinuity is set (the direct problem) and a number of problems for finding the form of the discontinuity and the distribution of the above-mentioned physical quantities on the discontinuity is considered when the law of the change of the external pressure along the boundary is set (for example, with the help of the approximate Newton equation). The problem which is considered here, which deals with the calculation of the boundary form and with the calculation of the distribution of the corresponding physical quantities on the discontinuity of the 1st kind for the compressible fluid with the magnetic field with field lines which are perpendicular to the plane of the flow in question, concerns the last sort of problems. The comparison of the results of the calculation with the data in the equatorial cross-section of the magnetosphere demonstrates that the calculated form of the boundary, the value of the velocity of the return flow and the value of the electric field on the magnetopause, agree satisfactorily with the observational data. 相似文献
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