全日面磁场观测资料的初步处理     

刘扬  宋国锋  王敬山  汪景琇 《中国天文和天体物理学报》1994,(2)

用口径为１０ｃｍ的全日面磁场望远镜，我们获得了光球的全日面视向磁场观测资料。与３５ｃｍ磁场望远镜的观测结果比对，发现日面上各活动区磁场的形态以及强度都吻合较好，说明全日面磁场望远镜得到的观测资料是可信的。  相似文献   

银河系厚盘的本地空间密度   总被引：1，自引：0，他引：1  

容建湘 《天文学报》1996,37(3):272-277

本文利用北银极天区的现代恒星计数资料，采用标准的银河系模型，通过恒星统计积分方程对参数值组合模型的亮度函数进行计数分析，证明了银河系厚盘恒星成份存在的必要性，并进一步得出太阳附近厚盘成份的空间密度的最佳期望值为薄盘密度的０．０４１．  相似文献   

基于ERSM涡轮盘径向变形的非线性动态概率分析     

王桂华  费成巍  白广忱 《贵州气象》2013,(4):529-536

为了准确设计高压涡轮盘和叶尖间隙,从概率的角度进行了涡轮盘径向变形的分析。介绍了高精度高效率的非线性动态概率分析的极值响应面方法(Extremum Response Surface Method, ERSM),并建立了其数学模型。考虑材料属性和边界条件的非线性,以及热载荷和离心载荷的动态性,基于ERSM对涡轮盘径向变形进行了非线性动态概率分析,得到了输入输出参数的分布特征和影响涡轮盘径向动态变形的主要因素。最后,通过方法比较,验证了ERSM在保证计算精度的前提下能大大提高计算速度,节约计算时间,改善计算效率。为进行更有效的涡轮盘设计和优化,改善叶尖间隙设计和控制的合理性提供了有效依据。   相似文献   

Submm observations of herbig ae/be systems     

Vincent Mannings 《Astrophysics and Space Science》1995,224(1-2):185-188

Studies of circumstellar dust and gas in pre-main-sequence systems are in part motivated by a desire to probe possible sites of future or on-going planet formation and, should accretion onto young stars be taking place, to determine whether the observed remnants of embryonic envelopes might yet contribute significantly to the final masses of stars as they evolve towards the main sequence. New 0.35- to 1.3-mm flux measurements have been made for 13 intermediate-mass pre-MS systems in order to estimate total dust+gas masses and to investigate the spatial distribution of circumstellar material. At least two sources may be dominated by compact circumstellar disks; emission from extended envelopes appears to be important for the majority of sources. HD 163296 is an unusual object and warrants further examination.  相似文献   

A Two—Temperature Supernova Fallback Disk Model for Anomalous X—ray Pulsars     

Ye Lu  K. S. Cheng National Astronomical Observatories  Chinese Academy of Sciences  Beijing Department of Physics  University of Hong Kong  Hong Kong  China 《中国天文和天体物理学报》2002,2(2):161-168

We present a case study of the relevance of the radially pulsational instability of a two-temperature accretion disk around a neutron star to anomalous X-ray pulsars (AXPs). Our estimates are based on the approximation that such a neutron star disk with mass in the range of 10^-6-10^-5M⊙ is formed by supernova fallback. We derive several peculiar properties of the accretion disk instability: a narrow interval of X-ray pulse periods; lower X-ray luminosities; a period derivative and an evolution time scale. All these results are in good agreement with the observations of the AXPs.  相似文献   

On The Origin of The High-Perihelion Scattered Disk: The Role of The Kozai Mechanism And Mean Motion Resonances     

Rodney S. Gomes  Tabaré Gallardo  Julio A. Fernández  Adrián Brunini 《Celestial Mechanics and Dynamical Astronomy》2005,91(1-2):109-129

We study the transfer process from the scattered disk (SD) to the high-perihelion scattered disk (HPSD) (defined as the population with perihelion distances q > 40 AU and semimajor axes a>50 AU) by means of two different models. One model (Model 1) assumes that SD objects (SDOs) were formed closer to the Sun and driven outwards by resonant coupling with the accreting Neptune during the stage of outward migration (Gomes 2003b, Earth, Moon, Planets 92, 29–42.). The other model (Model 2) considers the observed population of SDOs plus clones that try to compensate for observational discovery bias (Fernández et al. 2004, Icarus , in press). We find that the Kozai mechanism (coupling between the argument of perihelion, eccentricity, and inclination), associated with a mean motion resonance (MMR), is the main responsible for raising both the perihelion distance and the inclination of SDOs. The highest perihelion distance for a body of our samples was found to be q = 69.2 AU. This shows that bodies can be temporarily detached from the planetary region by dynamical interactions with the planets. This phenomenon is temporary since the same coupling of Kozai with a MMR will at some point bring the bodies back to states of lower-q values. However, the dynamical time scale in high-q states may be very long, up to several Gyr. For Model 1, about 10% of the bodies driven away by Neptune get trapped into the HPSD when the resonant coupling Kozai-MMR is disrupted by Neptune’s migration. Therefore, Model 1 also supplies a fossil HPSD, whose bodies remain in non-resonant orbits and thus stable for the age of the solar system, in addition to the HPSD formed by temporary captures of SDOs after the giant planets reached their current orbits. We find that about 12 – 15% of the surviving bodies of our samples are incorporated into the HPSD after about 4 – 5 Gyr, and that a large fraction of the captures occur for up to the 1:8 MMR (a ⋍ 120 AU), although we record captures up to the 1:24 MMR (a ≃ 260 AU). Because of the Kozai mechanism, HPSD objects have on average inclinations about 25°–50°, which are higher than those of the classical Edgeworth–Kuiper (EK) belt or the SD. Our results suggest that Sedna belongs to a dynamically distinct population from the HPSD, possibly being a member of the inner core of the Oort cloud. As regards to 2000 CR₁₀₅ , it is marginally within the region occupied by HPSD objects in the parametric planes (q,a) and (a,i), so it is not ruled out that it might be a member of the HPSD, though it might as well belong to the inner core.  相似文献   

A numerical solution of the dynamical instability of a thin accretion torus     

Liu Ren-jie  Wang De-yu 《Chinese Astronomy and Astrophysics》1995,19(4):507-512

We consider the non-axisymmetric, dynamical instability of a thin accretion torus with a non-zero shift of corotation radius. By numerical method we evaluated the wave number dependence of the linear rate of growth of instability and the co-rotation shift. The rate of growth is only slightly affected by the non-zero co-rotation shift, while the dispersion relation in the case of a shift is the same as that of the linear KdV equation. This shows that the “planet-like” solution found in numerical simulations of thin tori is very probably analogous to the soliton solution of the KdV equation.  相似文献   

Nodal and periastron precession of inclined orbits in the field of a rotating black hole     

N. R. Sibgatullin 《Astronomy Letters》2001,27(12):799-808

The inclination of low-eccentricity orbits is shown to significantly affect orbital parameters, in particular, the Keplerian, nodal precession, and periastron rotation frequencies, which are interpreted in terms of observable quantities. For the nodal precession and periastron rotation frequencies of low-eccentricity orbits in a Kerr field, we derive a Taylor expansion in terms of the Kerr parameter at arbitrary orbital inclinations to the black-hole spin axis and at arbitrary radial coordinates. The particle radius, energy, and angular momentum in the marginally stable circular orbits are calculated as functions of the Kerr parameter j and parameter s in the form of Taylor expansions in terms of j to within O[j ⁶]. By analyzing our numerical results, we give compact approximation formulas for the nodal precession frequency of the marginally stable circular orbits at various s in the entire range of the Kerr parameter.  相似文献   

黑洞吸积盘内边缘半径的演化     

汪定雄  杨兰田  何沙 《中国天文和天体物理学报》1995,(2)

本文用广义相对论讨论了黑洞吸积盘内边缘半径ｒ（ｍｓ）的演化规律。结果表明，吸积盘的中心黑洞在由Ｓｃｈｗａｒｚｓｃｈｉｌｄ型向极端Ｋｅｒｒ型演化的过程中，黑洞的角动量变化对ｒ（ｍｓ）的影响始终比黑洞的质量变化对ｒ（ｍｓ）的影响大。在此过程中ｒ（ｍｓ）始终是连续、单调减小的。本文得出ｒ（ｍｓ）对时间变化率的取值范围，并对其物理意义作了讨论。  相似文献   

Galactic kinematics and structure defined by open clusters     

Zi Zhu 《中国天文和天体物理学报》2009,9(12)

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