Kuiper带天体的原始分布模拟   总被引：1，自引：0，他引：1  

左庆林  聂清香  杨远玲  房建军 《天文学报》2008,49(4)

用包括太阳、8颗大行星、冥王星和UB313以及无质量实验粒子在内的N体问题的天体动力学模型,取当前观测的天体轨道根数为初始条件,对具有确定轨道根数的551个Kuiper主带内的小天体进行了10亿年的轨道反演数值模拟.结果显示:当前观测的这些Kuiper 天体中的1/3以上在10亿年前就位于该区域,少部分位于海王星轨道之内,其他在5OAU之外;在4.5亿年前,整个Kuiper主带内的天体呈较好的正态分布,海王星3:2共振带内没有像今天这样的天体聚集现象.  相似文献   

The empirical mass-luminosity relation for low mass stars     

Fang Xia  Shulin Ren  Yanning Fu 《Astrophysics and Space Science》2008,314(1-3):51-58

This work is devoted to improving empirical mass-luminosity relations (MLR) and mass-metallicity-luminosity relation (MMLR) for low mass stars. For these stars, observational data in the mass-luminosity plane or the mass-metallicity-luminosity space subject to non-negligible errors in all coordinates with different dimensions. Thus a reasonable weight assigning scheme is needed for obtaining more reliable results. Such a scheme is developed, with which each data point can have its own due contribution. Previous studies have shown that there exists a plateau feature in the MLR. Taking into account the constraints from the observational luminosity function, we find by fitting the observational data using our weight assigning scheme that the plateau spans from 0.28M_⊙ to 0.50M_⊙. Three-piecewise continuous improved MLRs in K, J, H and V bands, respectively, are obtained. The visual MMLR is also improved based on our K band MLR and the available observational metallicity data.  相似文献   

A symmetry-induced model of elliptical galaxy patterns     

Jin He 《Astrophysics and Space Science》2008,313(4):373-387

Sérsic (Atlas de Galaxias Australes, Observatorio Astronómico, 1968) generalized the de Vaucouleurs law which follows the projected (observed) one dimensional radial profile of elliptical galaxies closely and Dehnen (Mon. Not. R. Astron. Soc. 265:250, 1993) proposed an analytical formula of the 3-dimensional light distributions whose projected line profile resembles the de Vaucouleurs law. This paper is involved to recover the Dehnen model and generalize the model to account for galaxy elliptical shapes by means of curvilinear coordinate systems and employing a symmetry principle. The symmetry principle maps an orthogonal coordinate system to a light distribution pattern. The coordinate system for elliptical galaxy patterns turns out to be the one which is formed by the complex-plane reciprocal transformation Z=1/W. The resulting spatial (3-dimensional) light distribution is spherically symmetric and has infinite gradient at its center, which is called spherical-nucleus solution and is used to model galaxy central area. We can make changes of the coordinate system by cutting out some column areas of its definition domain, the areas containing the galaxy center. The resulting spatial (3-dimensional) light distributions are axisymmetric or triaxial and have zero gradient at the center, which are called elliptical-shape solutions and are used to model global elliptical patterns. The two types of logarithmic light distributions are added together to model full elliptical galaxy patterns. The model is a generalization of the Dehnen model. One of the elliptical-shape solutions permits realistic numerical calculation and is fitted to all R-band elliptical images from Frei et al. (Astron. J. 111:174, 1996) galaxy sample. The fitting is satisfactory. This suggests that elliptical galaxy patterns can be represented in terms of a few basic parameters.  相似文献   

Dimensions and equilibrium structures of the primary component of the nonsynchronous binary systems     

《New Astronomy》2014

Rotating stars and stars in the synchronous binaries have been extensively studied in literature. However, there are only few studies that have investigated the problems of the nonsynchronous binaries. In the present paper, we have made an attempt to study the various dimensions and equilibrium structures of the primary component of the nonsynchronous binaries. We have used the first approximation theory of Limber (1963) along with the methodology as that proposed by Mohan and Saxena (1983) for the present study. The objective of this paper is to check the effect of nonsynchronism on the various dimensions and equilibrium structures of the primary components of the binary systems. The results of the present study shows that there is change in the dimensions and equilibrium structures of the primary component of the binary systems due to nonsynchronism, and this change is more appreciable when the difference between the angular velocities of rotation and revolution is large.  相似文献   

剖析自动站各层地温的垂直变化     

张雪梅  王道田  王一二  王森  贾桂兰 《气象研究与应用》2011,32(4):69-71

对9个代表性的气象台站2005～2009年自动站的5～320cm各层次地温值的垂直变化规律进行了剖析;从中阐述出了一些行之有效的既能及时、准确、判断其地温值异常与否,又能长期作为工具使用的方式方法;有利于提高其有关数据的准确度和更有使用价值的目的。  相似文献   

Photometric Observation and Study of the Transiting Exoplanetary System HAT-P-8     

TAN Hong-bo  WANG Xiao-bin  GU Sheng-hong  Andrew Collier Cameron 《Chinese Astronomy and Astrophysics》2014

Three transit events of HAT-P-8 were observed by using the 1 m telescope of Yunnan Observatory and the 2.4 m telescope of Lijiang Astronomical Station in 2009 and 2012, respectively. The observational data are reduced with the coarse de-correlation and SysRem algorithms in order to improve the signal to noise ratio of the transit signals. The MCMC (Markov Chain Monte Carlo) technique is applied to analyzing the three transit light curves simultaneously, then the new parameters of the HAT-P-8 system are derived. The new value of the radius of HAT-P-8b is smaller than that given by Latham et al., while it is consistent with the value derived recently by Mancini et al. By linear ?tting on the 23 high-precision mid-transit times, the orbital period of HAT-P-8b is re?ned as P =3.0763461±0.0000021 d, and from the (O − C) analysis no obvious TTV (Transit Timing Variation) signal has been detected.  相似文献   

Dynamics and gravitational waveforms in spinning compact eccentric binaries     

《New Astronomy》2014

The effects of eccentricity on the Hamiltonian dynamics of post-Newtonian spinning compact binaries and gravitational radiation from eccentric orbits are discussed. The simulation results of scans for chaos show that the eccentricity has a great effect on the dynamics without considering dissipation due to gravitational radiation. Moreover, both the dynamics behavior and the orbital eccentricity jointly modulate the gravitational waveforms, and the spin–spin coupling effect play an important role during the gravitational radiation of inspiral and coalescence. Moreover, the imprint of characteristic of the original system can be deduced from the time-domain and frequency-domain waveforms.  相似文献   

Multi-band observations of gamma ray bursts     

S. G. Bhargavi 《Journal of Astrophysics and Astronomy》2002,23(1-2):123-127

This talk focuses on the various aspects we learnt from multiband observations of GRBs both, before and during the afterglow era. A statistical analysis to estimate the probable redshifts of host galaxies using the luminosity function of GRBs compatible with both the afterglow redshift data as well as the overall population of GRBs is discussed. We then address the question whether the observed fields of GRBs with precise localizations from third Inter-Planetary Network (IPN³) contain suitable candidates for their host galaxies.  相似文献   

Intracluster medium through three years of WMAP     

Niayesh Afshordi   《New Astronomy Reviews》2006,50(11-12):905

Wilkinson microwave anisotropy probe (WMAP) has provided us with the highest resolution all-sky maps of the cosmic microwave background (CMB). As a result of thermal Sunyaev–Zel’dovich effect, clusters of galaxies are imprinted as tiny, poorly resolved dips on top of primary CMB anisotropies in these maps. Here, I describe different efforts to extract the physics of intracluster medium (ICM) from the sea of primary CMB, through combining WMAP with low-redshift galaxy or X-ray cluster surveys. This finally culminates at a mean (universal) ICM pressure profile, which is for the first time directly constrained from WMAP 3 year maps, and leads to interesting constraints on the ICM baryonic budget.  相似文献   

GPS近实时共视观测资料处理算法研究   总被引：2，自引：0，他引：2  

杨旭海  胡永辉  李志刚  李孝辉  郑兴武 《天文学报》2003,44(2):204-214

GPS共视资料的高精度快速处理可实现近实时共视时间传递，常见的平滑方法不能满足近实时共视的要求。分析GPS共视资料特点，设计一种卡尔曼滤波算法，对共视资料进行近实时处理，以便削弱观测噪声，估计异地钟差，对相距2000多公里的中国科学院国家授时中心(NTSC)与日本通信综合研究所(CRL)，和相距1000多公里的CRL与韩国计量科学研究院(KRIS)的共视观测资料处理结果表明：卡尔曼滤波算法所得钟差与根据BIPMT公报所得钟差的均方根误差分别优于2．9ns和2．6ns，为进一步提高比对精度，最后对近实时共视应用于多站点间相互比对的情况，提出在卡尔曼滤波算法基础上使用间接观测平差处理技术，根据共视网络中站点间距离设置观测权值，通过解矛盾方程组得到两站钟差，以NTSC、CRL和KRIS3站比对为例，以BIPMT公报得到的钟差为标准，对间接观测平差处理前后的数据比较表明，近实时比对精度可进一步提高。  相似文献