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Two-post-Newtonian approximation of the scalar-tensor theory with an intermediate-range force for general matter

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Science China(Physics,Mechanics & Astronomy) 2015年第3期58卷 8-15页

作者： DENG XueMei purple mountain observatory Chinese Academy of Sciences

Some future space missions measure distances of laser links and angles with unprecedented precision, allowing us to test theories of gravity up to the two-post-Newtonian （2PN） order. Besides, investigation of an intermediate-range force has been of considerable interests in gravitational experiments. Inspired by these ideas, within the framework of the scalar-tensor theory with an intermediate- range force, its 2PN approximation is obtained with Chandrasekhar＇s approach. It includes the 2PN metric and equations of motion for general matter without specific equation of state. The conserved quantities to the 2PN order are isolated with the aid of the energy-momentum complex. We also discuss the prospect of testing and distinguishing the intermediate-range force with the orbital motions of celestial bodies and spaeecrafts.

关键词： gravitation intermediate-range force post-Newtonian approximation

Dispersion Equation of Low-Frequency Waves Driven by Temperature Anisotropy

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Plasma Science and Technology 2012年第10期14卷 880-885页

作者：陈玲吴德金 purple mountain observatory Chinese Academy of Sciences

The plasma temperature （or the kinetic pressure） anisotropy is an intrinsic characteristic of a collisionless magnetized plasma. In this paper, based on the two-fluid model, a dispersion equation of low-frequency （ω〈〈ωci, ωci the ion gyrofrequency） waves, including the plasma temperature anisotropy effect, is presented. We investigate the properties of low-frequency waves when the parallel temperature exceeds the perpendicular temperature, and especially their dependence on the propagation angle, pressure anisotropy, and energy closures. The results show that both the instable Alfven and slow modes are purely growing. The growth rate of the Alfven wave is not affected by the propagation angle or energy closures, while that of the slow wave depends sensitively on the propagation angle and energy closures as well as pressure anisotropy. The fast wave is always stable. We also show how to elaborate the symbolic calculation of the dispersion equation performed using Mathematica Notebook.

关键词： dispersion equation low-frequency waves temperature anisotropy

Analysis of the applicability of collision probability algorithms for nonlinear relative motion

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Science China(Physics,Mechanics & Astronomy) 2013年第5期56卷 1041-1046页

作者： XU XiaoLi XIONG YongQing purple mountain observatory Chinese Academy of Sciences Key Laboratory of Space Object and Debris observatory Purple Mountain ObservatoryChinese Academy of Sciences

In the calculation of the collision probability between space objects, the assumption of linear relative motion is generally adopted to simplify the problem because most encounters are at high relative velocity. Nevertheless, the assumption is no longer valid for encounters at extremely low velocities, and a new algorithm is urgently needed for computing collision probability for space objects having nonlinear relative motion. In this particular case, the direction associated with relative velocity is reintroduced for integration. The different integral limits would lead to the variations of probability and integral time. Moreover, the application scope of this new algorithm is also presented. Since the nonlinear effect is only significant in some certain situations, the new algorithm needs to be considered only in such certain situations. More specifically, when space objects in circular orbits encounter with a tiny inclined angle (the extreme situation), the new algorithm can derive much more accurate collision probability than the linear method, that is to say, the linearity assumption involved in general collision probability formulation is not adequate anymore. In addition, the deviation of the probability derived by the linear method (linear collision probability) from that derived by the nonlinear method (nonlinear collision probability) also weakly depends on the relative distance and combined covariance, and essentially depends on their ratio.

关键词： space debris collision probability nonlinear relative motion integral limits

A method of autonomous orbit determination for satellite using star sensor

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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 268-281页

作者： MA Jianbo XU Jin CAO Zhibin purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

In this paper a method of autonomous orbit determination using star sensor is studied. By building relatively consummate dynamical models which simulate attitude motion of satellite and observation from satellite to background stars, the simulant computation of this method is executed, and it is shown that the method of autonomous orbit determination is feasible. Academic and calculation analyses have been done for the relation between the direction of star sensor with respect to satellite-body coordinate system and the accuracy of autonomous orbit determination.

关键词： autonomous orbit determination of satellite, star sensor, attitude of satellite.

The total column densities and fractional abundances of CH_3CN,CH_3OH,HCOOCH_3 and^(13)CS in W51 cores

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 158-167页

作者： PEI Chunchuan MA Hongjun ZENG Qin LI Bo purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

We present interferometric observations of the W51 region at 2.7 mm and 3.3 mm with the Berkeley-Illinois-Maryland Association Array. The lines of CH3CN (J = 6 – 5, K = 0,1,2,3,4), CH3OH (15-2 ?151 E), HCOOCH3-A (71,6 – 61,5), HCOOCH3 -E (71,6 – 61,5) and 13CS (2-1) as well as the 2.7 mm continuum toward W51 have been observed. The derived total beam-averaged column densities NT and fractional abundances of CH3CN, CH3OH, HCOOCH3 and 13CS in W51 cores have been obtained.

关键词： massive star formation, interstellar molecular lines, column density, fractional abundance.

The structure of molecular cloud W51 and dense cores——CO(J=1-0)and HCO^+(J=1-0)spectral line mapping

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 168-177页

作者： MA Hongjun PEI Chunchuan ZENG Qin purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

We present a large scale map of about 15′×15′of CO(J=1-0) toward W51 giant molecular cloud (GMC), which covers the most active star-forming region of W51 GMC, and an interferometry HCO+(J=1-0) map of a high spatial resolution (i.e. 8″.7× 6″.1) with a field of view (2′×2′) centered at W51IRS1. A structure model of W51GMC is obtained according to the results of the observations and analyses. The observations demonstrate that some small molecular cores generated by the collision between the W51GMC and the 60—73 km·s-1 foreground cloud are collapsing toward their own centers. In addition, 16 new molecular cores are discovered from the HCO+(J=1-0) map.

关键词： molecular core, continuum source, star formation.

How to co-add images? I. A new iterative method for image reconstruction of dithered observations

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Research in Astronomy and Astrophysics 2017年第10期17卷 1-14页

作者： Lei Wang Guo-Liang Li purple mountain observatory Chinese Academy of Sciences

By employing the previous Voronoi approach and replacing its nearest neighbor approx- imation with Drizzle in iterative signal extraction, we develop a fast iterative Drizzle algorithm, namedfiDrizzle, to reconstruct the underlying band-limited image from undersampled dithered frames. Compared with the existing iDrizzle, the new algorithm improves rate of convergence and accelerates the computational speed. Moreover, under the same conditions （e.g. the same number of dithers and iterations）, fiDrizzle can make a better quality reconstruction than iDrizzle, due to the newly discov- ered High Sampling caused Decelerating Convergence （HSDC） effect in the iterative signal extraction *** demonstrates its powerful ability to perform image deconvolution from undersampled dithers.

关键词： techniques: image processing -- methods: observational -- stars: imaging -- planets andsatellites: detection -- gravitational lensing

Near-Infrared Observations of the Massive Star Forming Region IRAS 23151+5912

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Chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 284-298页

作者： Xue-Peng Chen Yong-Qiang Yao purple mountain observatory Chinese Academy of Sciences, Nanjing 210008 purple mountain observatory Chinese Academy of Sciences Nanjing 210008

Near-infrared images and K-band spectroscopy of the massive star-formingregion IRAS 23151+5912 are presented. The JHK′ images reveal an embedded infrared clusterassociated with infrared nebula, and the H_2 (2.12 μm) narrowband image provides for the first timeevidence of outflow activity associated with the cluster. That the cluster is young can be shown bythe high percentage of infrared excess sources and the outflow activity. We suggest an age of thecluster of ～ 10~6 yr. Eight young stars are found in the bright nebular core around IRAS23151+5912. By the color-magnitude diagrams of the cluster, we found five high-mass YSOs and fourintermediate-mass YSOs in the cluster. Eight H_2 emission features are discovered in the region witha scattered and non-axisymmetric distribution, indicating the existence of multiple outflows drivenby the cluster. Diffuse H_2 emission detected to the north and to the west of the cluster mayresult from UV leakage of the cluster. Brγ, H_2, and CIV emission lines are found in the K-bandspectrum of the brightest source, NIRS 19, indicating the presence of envelope, stellar wind, andshock in the circumstellar environment. We have estimated an O7-O9 spectral type for the centralmassive YSO (20 ～ 30 solar mass), with an age of less than 1 x 10~6 yr.

关键词： infrared radiation stars: formation ISM: individual: IRAS 23151 + 5912 ISM: jets and outflows

Near-infrared polarization study of L1641S

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Science China(Physics,Mechanics & Astronomy) 2005年第1期48卷 68-77页

作者： CHEN Xuepeng YAO Yongqiang purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

H-band polarimetric images and Ks-band images of star formation region L1641S are presented. Two reflection nebulae, Re50N and Re50, are in the north and south of the region, respectively. The polarization maps of two nebulae exhibit high degrees of polarization and centrosymmetric patterns, indicating the single scattering and small dust grains in the nebulae. There are two infrared sources, IRS1 and IRS2, in the nebula Re50N. IRS1 is the illuminating source of the nebulae and the driving source of CO outflow; IRS2 is suggested to provide considerable light at optical wavelengths. The high polarization in Re50N can be interpreted as surface scattering from the outflow at an inclination of 30 degrees. Based on the polarization arc structure, we further identified the bipolar structure of the nebula Re50N. The FU Orionis phenomenon in L1641S is discussed at the end of this paper.

关键词： near-infrared polarization, star formation, infrared nebula, molecular outflow.