33个RS CVn型双星的H_α观测和研究(Ⅰ)

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。     

御夫座εH_α附近的连续观测

用美国麦克唐纳2.7米望远镜折轴分光仪的Reticon对H_α附近光谱区进行连续18次(3月9日)和6次(3月10日)观测,用计算机绘图和处理,得到了金属线的视向速度,H_α线的轮廓、视向速度、等值宽度的短时标变化.各金属线的视向速度变化很快,但每条线又有不同的变化基点,可以说是“半规则变化”.H_α在紫端有强的发射线,其对应视向速度为-60km/s左右;靠吸收线中心的两侧,各有一条较弱的发射线,对应的视向速度分别为 12km/s和 57km/s,其吸收线中心对应的视向速度为 20km/s左右;H_α的视向速度变化较小.H_α的轮廓变化主要是在两个较强发射的紫翼.对这些结果进行了简要的讨论.     

御夫座ε星由全食到第四次接触前的Hα变化

在御夫ε由全食到第四次接触前,用美国McDonald天文台2.7米和2.1米望远镜折轴分光仪的Reticon,对Hα进行了四段时间八夜共56次观测,得到了Hα的轮廓、等值宽度、视向速度的变化。在食甚前105天(1983年3月9—10日),在吸收线蓝侧有强的发射,吸收线的等值宽度为1800m,中心附近有两个小的发射,吸收中心的视向速度高于轨道速度。在食甚后约两个月(1983年8月30—31日),吸收线等值宽度增至3620m,两侧没有发射,而呈明显的宽达每侧7左右的线翼,中心结构复杂(有三个发射),视向速度低于轨道速度约30kms~(-1)。刚第三次接触时(1984年1月16日),红端出现强的发射,吸收中心继续紫移,但没有小的发射,吸收线的等值宽度猛减到1440m。第三至第四接触中间(1984年3月16—19日),红端强发射反而减弱,吸收中心向红端恢复,其等值宽度仍在减少,蓝端呈弱的发射。 比较本文的观测与Wright等人在1955—1957年食期间的Hα观测,可以肯定Hα的轮廓变化总体来说是可以重复的,说明这一变化是主、次星相互作用的结果,并认为,主星FI_(ap)外有一个半径大约450R_⊙的盘(或环),以V sin i=70kms~(-1)旋转,它是Hα发射的主要源,“次星”中心是一颗高速(V sin i≥70kms~(-1))旋转的B型星,外围被半透明的大气所包围,并用这一模型对Hα的变化做了定性     

三颗Be星的分光研究

自1978年12月至1979年5月间,我们用60/90厘米施米特卡氏反射光栅摄谱仪对φPer、ξTau、κDra进行了照相光谱观测。获得了电子浓度、自转速度、V/R变化等,并将ξTau同超巨星βOri进行了比较。 资料分析可得:在我们的观测期内,φPer存在着明显的气壳活动;ξTau处在相对宁静阶段,气壳缓慢膨胀;而κDra与“经典”的Be星相似。     

飞马座AG星的分光光度

1962年紫金山天文台用60cm 反光镜及附属有缝摄谱仪进行了飞马座 AG 星的分光光度观测,色散度于 H_γ处为153(?)/mm. 得到了下列一些参数:色温度,发射线的等值宽度和相对强度,电子温度. 把这些参数同近十年来别人的结果作了比较,得到了下面一些结论:①近十年来,色温度总的说来在逐渐下降;②同时,高电离电位的发射线强度相对于低电离电位的发射线是在逐渐增强;③一些禁线的强度也在增强;④特别是,我们注意到在氢巴尔末发射线等值宽度的变化和色温度的变化之间存在着一定的联系:当氢巴尔末发射线等值宽度增加时,色温度下降,而等值宽度减小时,色温度上升.     

若干Be星的自转

通过光谱观测获得53颗Be星的自转速度Vsir.i,在Hutchings的方法基础上估算出V和i。我们分析了自转对发射线宽度的影响,利用发射线峰间间隔求取气壳与光球的半径比和稀化因子。文中着重讨论了快自转而且存在恒星风的自转模型同Be现象之间的关系。     

六个色球活动双星的H_a观测和研究

１９９０年８月至１９９１年８月期间，利用云南天文台１ｍ望远镜折轴摄谱仪附加厚片ＣＣＤ探测器进行了观测，得到二十余颗色球活动双星的大色散、高分辨率，高信噪比的光谱，本文发表其中ηＡｎｄ、３Ｃａｍ、４ＵＭｉ、ｖ２Ｓｇｒ、Ｓｇｒ、ＨＲ７３３３六个双星系统的Ｈａ附近区域光谱观测和研究结果。这六个系统在ＣＡＢＳ表中有关Ｈａ线的资料还是空白。我们给出了它们高分辨率的Ｈａ线轮廓图，计算了它们的等值宽度、半宽、Ｈａ线心的视向速度以及３条金属线视向速度．由观测结果表明，ηＡｎｄ双星的Ｈａ线在不同位相变化不大，没有观测到它的色球活动．３Ｃａｍ由于受色球活动的影响，在０．１５４位相时Ｈａ轮廓发生了突变，其等值宽度明显小于其它位相的等值宽度．４ＵＭｉ的Ｈａ线也是吸收线，但由于受色球活动的影响，致使Ｈａ线心部分受到发射的填充．Ｓｇｒ和ｖ２Ｓｇｒ的光谱Ｈａ线都属于吸收线，没有发现色球活动的影响，很可能不是色球活动星．ＨＲ７３３３是个色球活动比较剧烈的双星，Ｈａ吸收线受到了色球活动引起的发射填充，而且填充量较大．     

受星风或膨胀气壳包围的双星物质损失率测定

对观测到的受星风或膨胀气壳包围的双星系统的PCyg谱线理论分析可精确测定其星风物质损失率．我们在计算这类星的理论谱线时，考虑了氢氦混合气体的多能级跃迁、轨道运动引起的密度非径向分布等因素，对轨道形状做了简化，所得结果是令人满意的．     

类星体SDSS J2220+0109中特殊吸收线系统的发现与研究

斯隆数字巡天光谱数据中发现,类星体SDSS J2220+0109光谱中同时出现如下极为罕见的吸收线:氢巴尔末线Hα和Hβ,亚稳态He I* λλ3889、3189tt,CaⅡH、K,以及来自FeⅡ*能级的波数分别为7 955 cm~(-1)、13 474 cm~(-1)和13 673 cm~(-1)的众多吸收线.上述吸收线具有相似的速度结构,线宽达1 500 km·s~(-1),相对于发射线表现出蓝移.研究结果表明,这些吸收线很可能来自部分电离区,密度n_E≈10~6cm~(-3),柱密度N_(H I)≈10~(21) cm~(-2),Lyα共振散射对氢原子的激发起重要作用.SDSS J2220+0109斯隆r星等为16.56 mag,是探索活动星系核中特殊吸收线起源的理想实验室.将来的紫外光谱观测可以更加准确决定吸收气体的密度、柱密度、电离参数等物理性质;光学光谱监测有助于限定吸收线的产生机制.此外还发现,SDSS J2220+0109中的FeⅡ发射线显著区别于典型的窄线赛弗特Ⅰ型星系ⅠZw 1,很可能来自低密度气体,进一步研究有助于理解类星体中FeⅡ发射线的起源.     

相接双星SW Lac的视向速度观测及其活动性的研究

本文发表了WUMa型相接双星SW Lac的1984年视向速度观测,它给出的新的分光质比q_(sp)=m_2/m_1=1.255±0.011。通过光变曲线观测和视向速度曲线观测的联合分析,得出改进了的双星绝对参量:M_1=0.78M_⊙,M_2=0.96M_⊙,R=0.91R_⊙和R_2=1.00R_⊙,在此基础上,对SW Lac双星的周期变化,可能的质量交流和损失,以及黑子活动等作了详细分析讨论。     

On the origin of the solar system and the exceptional position of the Sun in the Galaxy

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.     

Perturbations by the oblateness of the Earth and by the planets in the motion of the Moon

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.     

On the model of the accumulation of the moon compatible with the data on the composition and the age of lunar rocks

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.     

On the theory of the oblateness of the Sun

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     

Accounting for the viscosity of the fluid core in the problem of the physical libration of the moon

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.     

On some problems concerning the calculation of the form of the magnetopause and the electric field on the magnetopause in the framework of the continuum medium model

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.