A Quantitative Method to Optimise Magnetic Field Line Fitting of Observed Coronal Loops

Many authors use magnetic-field models to extrapolate the field in the solar corona from magnetic data in the photosphere. The accuracy of such extrapolations is usually judged qualitatively by eye, where a less judgemental quantitative approach would be more desirable. In this paper, a robust method for obtaining the best fit between a theoretical magnetic field and intensity observations of coronal loops on the solar disk will be presented. The method will be applied to Yohkoh data using a linear force-free field as an illustration. Any other theoretical model for the magnetic field can be used, provided there is enough freedom in the model to optimize the fit.     

First Images of Impulsive Millimeter Emission and Spectral Analysis of the 1994 August 18 Solar Flare

We present here the first images of impulsive millimeter emission of a flare. The flare on 1994 August 18 was simultaneously observed at millimeter (86 GHz), microwave (1-18 GHz), and soft and hard X-ray wavelengths. Images of millimeter, soft and hard X-ray emission show the same compact ( 8) source. Both the impulsive and the gradual phases are studied in order to determine the emission mechanisms. During the impulsive phase, the radio spectrum was obtained by combining the millimeter with simultaneous microwave emission. Fitting the nonthermal radio spectra as gyrosynchrotron radiation from a homogeneous source model with constant magnetic field yields the physical properties of the flaring source, that is, total number of electrons, power-law index of the electron energy distribution, and the nonthermal source size. These results are compared to those obtained from the hard X-ray spectra. The energy distribution of the energetic electrons inferred from the hard X-ray and radio spectra is found to follow a double power-law with slope 6–8 below 50 keV and 3–4 above those energies. The temporal evolution of the electron energy spectrum and its implication for the acceleration mechanism are discussed. Comparison of millimeter and soft X-ray emissions during the gradual phase implies that the millimeter emission is free-free radiation from the same hot soft X-ray emitting plasma, and further suggests that the flare source contains multiple temperatures.     

Spectral Line and Continuum Radiation Propagation in a Clumpy Medium

We discuss the propagation of spectral line and continuum radiation in a clumpy medium and give general expressions for the observed absorption or emission from a cloud population. We show that the affect of the medium clumpiness can usually be characterised by a single number multiplying the mean column opacity. Our result provides a simpler proof and generalization of the result of Martin et al. (1984). The formalism provides a simple way to understand the effects of clumping on molecular line profiles and ratios; for example, how clumping effects the interpretation of ¹³CO(1–0) to ¹²CO(1–0) line ratios. It also can be used as a propagation operator in physical models of clumpy media where the incident radiation effects the spectral line emissivity. We are working to extend the formalism to the propagation of masers in a clumpy medium, but in this case, there are special difficulties because formal expectation values are not characteristic of observations because they are biased by rare events.     

变星及发射线星系的计算机自动搜索

本文发展了一套计算机自动证认、交叉比对的技术,应用于1989年9月至12月间北京天文台60/90cm施密特望远镜的CCD测光资料及GSC星表,由二个系统的V星等资料,在6个平方度内找到5颗变星;利用二个系统B颜色带宽的不同,进行发射线星系巡天,在3个平方度内找到15个致密核发射线星系.并讨论了本方法用于光变天体、包指数反常天体、位置移动天体、发射线天体巡天的可能性.     

Variation of Emission Line Width in Mid- and High-Latitude Corona

Spectroscopic studies of the solar corona, using the high spatial and spectral resolution 25-cm coronagraph at the Norikura Solar Observatory for equatorial off-limb observations, indicated that the variation of radiance and line width with height is different for different temperature lines. The line width of the forbidden red emission line [Fe x] 6374 Å was found to increase with height, and that of the green emission line [Fe xiv] 5303 Å decreased with height. This had been interpreted in terms of the interaction between different temperature plasmas but needed to be confirmed. Further observations were made on several days during 2004, in two emission lines simultaneously covering the mid-latitude and polar regions to investigate the existence of the observed variation in other parts of the solar corona. In this study, we have analysed several raster scans that cover mid- and high-latitude regions of the off-limb corona in all four bright emission lines [Fe x] 6374 Å, [Fe xi] 7892 Å, [Fe xiii] 10747 Å, and [Fe xiv] 5303 Å. We find that the FWHM of the red line increases with height and that of the green line decreases with height, similar to the observations in the equatorial regions. The line widths are higher in the polar regions for all of the observed emission lines except the green line. Higher values of FWHM in polar regions may imply higher non-thermal velocities, which could be further linked to a non-thermal source powering the solar-wind acceleration, but the reason for the behaviour of the green emission line remains to be explored.     

类星体L_α森林吸收线密度与发射红移的相关性

本文对16个高红移类星体的L_α森林吸收线密度N(z_(abs))统计分析的结果,表明它明显地依赖于类星体自身的发射红移z_(em)。这不仅表现在z(em)越大的类星体其全部L_α吸收线的平均数密度N(z_(abs))也越大;更重要的是,对于相同的吸收红移值z_(abs),而言,N(z_(abs))在统计意义上明显地随着类星体z_(em)的增大而增大。另一方面,本文也在“吸收体源自类星体抛射”的框架下作了统计,结果仍表明z_(em)对L_α森林吸收线密度有显著影响,但抛射速度却对被抛射体的数目无显著影响。最后,对所得的结果以及可能影响N(z_(abs))的若干因素作了讨论。     

X-ray Line and Recombination Emission in the Afterglow of Grb

We calculate the time-dependent line and recombination spectrum of nonequilibrium plasma heated by the strong radiation as the test model of X-ray line emission of GRB afterglows. Our calculation shows that the non-equilibrium effect of plasma is complex and important to the time evolution of the spectrum. The origin of these lines puzzles us, but is essential to understand the nature of GRBs and their circumstellar matter.     

Spectral Evolution of Synchrotron and Inverse Compton Emission in BL Lac Objects

With XMM–Newton observations, the X-ray spectral variations and the derived physical implications for two very high energy gamma-ray BL Lac objects PKS 2155–304 and S5 0716+714 are presented.     

The Doppler Effect and Spectral Energy Distribution of Blazars

The relativistic beaming model is adopted to discuss quantitatively the observational differences between radio-selected BL Lac objects (RBLs) and X-ray-selected BL Lac objects (XBLs), and between BL Lac objects and flat spectrum radio quasars (FSRQs). The main results are the following:(1) In the Doppler corrected color-color(αro^in-αox^in) diagram,XBLs and FSRQs occupy separated regions, while RBLs bridge the gap between them. These properties suggest that similar intrinsic physical processes operate in all the objects under a range of intrinsic physical conditions. (2) Our results are consistent with the results of Sambruna, Maraschi and Urry (1996) from other methods. We show the αxox introduced by Sambruna to be a good index for describing the energy distribution because it represents the intrinsic energy distribution and includes the Doppler correction. (3)The Doppler effect of relativistic beaming is the main mechanism, and the physical differences(such as magnetic fields, electron energies) are also important complementary factors for understanding the relation between XBLs and RBLS.     

伽玛暴数据处理中的贝叶斯方法

贝叶斯推断是建立在贝叶斯定理上的一种参数估计方法。根据贝叶斯定理,当根据经验,对待估计的参量θ的分布密度p(θ)(称为“验前分布”)有所了解时,在给定观测数据D的情况下,可以计算出待估参数θ的“验后分布”-- p(θ|D)。p(θ|D)反映了观测结果对p(θ)的修正。所有贝叶斯统计推断都是以验后分布为基础的。贝叶斯估计法是数据分析中的有力工具,其在伽玛暴(GRBs)数据分析窗口展现了多方面的应用,例如分析光变结构,确定参数分布,检验是否存在某种谱线特征,比较和选取模型,等等。     

一个土墩日珥的D3线光谱分析Ⅰ-D3线特征及其计算

198 4年 5月 5日太阳东边缘土墩日珥的Hα单色像和D3线被观测到了。D3发射线由两部分组成 :主成分和致宽成分。本文利用双层模型方法对该土墩日珥的 1 7条D3发射线成功地进行了计算 ,给出了D3线的计算结果。计算结果表明 :日珥的D3发射线主要由热的多普勒致宽和微观湍流致宽所致 ,其它致宽机制的作用可以忽略     

几何薄光学厚吸积盘谱线轮廓及成像研究

假设位于黑洞赤道面上做圆形轨道运动的吸积盘是几何薄、光学厚的.利用光子追踪法计算在Kerr度规下的光子运动轨迹,通过数值计算研究薄吸积盘的相对论谱线轮廓及成像.在大角度观测时,吸积盘下表面的光子对谱线轮廓及成像的影响是显著的.     

Emission Line Profiles and Images of Geometrically Thin and Optically Thick Accretion Disks

Under the assumption that the accretion disk around a Kerr (spinning) black hole is geometrically thin and optically thick, the trajectories of photons in Kerr metric are calculated by using the photon tracing method. And by numerical calculations, we have made a study on the relativistic iron line profiles and images of thin accretion disks. The result shows that viewing at large inclination angles, because of the contribution of the photons from the lower surface of the accretion disk, the line profile becomes double-peaked and the flux image is also significantly modified.     

Relation between the Spatial Distribution and Spectral Index of Superthermal Electron Distribution in Solar cm-Radio Sources

A series of solar cm-radio bursts are analyzed by a new inverse method estimating spatial changes of the superthermal electron distribution in solar cm-radio burst sources. It is found that the measure of the spatial change of superthermal electrons in the radio source ν _n is always greater than that for the magnetic field ν _B and it is linearly dependent on the spectral index of the electrons δ as ν _n ≈0.5δ. This relation is explained in the simplified flare-loop model integrating the analytical solutions of the Fokker – Planck equation. The mean value of ν _B is found to be 0.36±0.04, which is very close to the value of ν _B =0.38±0.02 derived from the dependence of the magnetic field strength on the height in the active region measured by RATAN-600.     

Spectral Synthesis via Mean Field approach to Independent Component Analysis

We apply a new statistical analysis technique, the Mean Field approach to Independent Component Analysis(MF-ICA) in a Bayseian framework, to galaxy spectral analysis. This algorithm can compress a stellar spectral library into a few Independent Components(ICs), and the galaxy spectrum can be reconstructed by these ICs. Compared to other algorithms which decompose a galaxy spectrum into a combination of several simple stellar populations, the MF-ICA approach offers a large improvement in efficiency. To check the reliability of this spectral analysis method, three different methods are used:(1) parameter recovery for simulated galaxies,(2) comparison with parameters estimated by other methods, and(3) consistency test of parameters derived with galaxies from the Sloan Digital Sky Survey. We find that our MF-ICA method can not only fit the observed galaxy spectra efficiently, but can also accurately recover the physical parameters of galaxies. We also apply our spectral analysis method to the DEEP2 spectroscopic data, and find it can provide excellent fitting results for low signal-to-noise spectra.     

一个土墩日珥的D3线光谱分析Ⅱ-活动边缘和土墩日珥的物理特性

根据 1 984年 5月 5日土墩日珥D3线的拟合结果 ,本文分析了该土墩日珥的物理特性。结果发现 ,形成活动边缘的物质呈间歇性抛射 ,抛射物质的密度、温度在观测前期有显著变化 ,湍流速度异常之大 ,达 30km/s。土墩日珥的物理特性较一般 ,其D3线可用微观湍流 3～ 8km/s和低温 50 0 0～ 80 0 0K解释。