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Near-Infrared Imaging Observations of the Orion A-W Star Forming Region

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Chinese Journal of Astronomy and Astrophysics 2002年第3期2卷 260-265页

作者： Jun-Jie Wangnational astronomical {2., Chinese academy of sciences, beijing 100012Chinese academy of sciences-Peking University Joint beijing Astrophysics Center, beijing100871 national astronomical {2. Chinese Academy of Sciences Beijing 100012 Chinese Academy of Sciences-Peking University Joint Beijing Astrophysics Center Beijing 100871

We carried out near-infrared imaging observations of the Ori A-W region using the Italian 1.5 m TIRGO infrared telescope at Gornergrat. A group of infrared objects is visible on the K band image, including an IRAS source (IRS 1). From its IRAS flux density the IRAS luminosity is derived to be 45L⊙, which shows that IRS 1 is a low-mass protostar. By superimposing the position of the VLA H2. maser on the K image, we can identify the less evolved object IRS 1 as the excitation source of the H2. maser, within a projected distance of 470AU. This would be evidence that the maser effect is associated with the youngest phase of stellar evolution. The first probable HH object candidate in the Ori A-W region is discovered from the H2.(1)1-0 observation. Comparing the position of the H2. maser with the direction of the molecular hydrogen emission in the region, we suggest that the observed H2. maser could be tracing the circumstellar disk of IRS 1.

关键词： Stars: formation - ISM: jets and outflows

How to estimate the effect of an intense meteor shower on human space activities

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Science china(Physics,Mechanics & Astronomy) 2009年第8期52卷 1161-1168页

作者： WU GuangJie national astronomical {2./Yunnan Observatory,Chinese academy of sciences,Kunming 650011,china national astronomical {2./Yunnan Observatory Chinese Academy of Sciences Kunming China

In the present age,the potential threat to space projects coming from some intense meteor storms has been ***,the increasing activities of mankind in space for scientific,commercial and military purposes have led to an increase in safety-related problems about the satellites,space stations and *** new techniques for observing meteors and meteor showers have been ***,how to estimate even predict the effect of an intense meteor shower should be further *** initial definition about a meteor storm based on visual observations with a Zenithal Hourly Rate of over one thousand seems insufficient,since it only means a storm or burst of meteors in *** 2.06 the author suggested a synthetical index of the potential threats about intense activities of meteors;however,it is too complex to determine several *** this paper,the author suggests a Special True Number Flux Density(STNFD).Set a certain energy-limit,or a certain electric-charge-limit,and then calculate the number flux *** the comparison between two of the 10 strong meteor showers in recent years it is found that the important factor affecting the space flight security is not only the number of meteoroids,but also their velocities,their average energy and the population index *** show that Giacobinids,even June Bootids,should be one of the most hazardous meteor showers.

关键词： meteors meteorites and tektites spacecraft/atmosphere interactions observation and data reduction techniques

Drifting bands of solar radio spikes

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Chinese Science Bulletin 2008年第4期53卷 638-640页

作者： XU FuYing1,2. WU HongAo1,2.1 Purple Mountain Observatory,Chinese academy of sciences,Nanjing 2.0008,{2. 2.national astronomical observatories,Chinese academy of sciences,beijing 100012.china Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China astronomical observatories Chinese Academy of Sciences Beijing 100012 China

The solar flare(1N/C5.3) occurred in NOAA 8742.on October 2.,1999,and the accompanied complex radio burst was observed by the spectrometer with both high temporal(5 ms) and frequency(10 MHz) resolutions at Purple Mountain Observatory(PMO).It started at 04:2.:42.UT,peaked at 04:2.:42.UT and ended at 04:2.:18 *** most significant feature of the event might be the sequential spikes in both time and frequency to form three slow drift bands over the frequency range of ～5 to ≥7.5 GHz with almost the same drift rate about 2.7 GHz/*** relative bandwidth for the individual spikes varied from 1.6% to 4.9%,typically 3.3%.Based on electron cyclotron maser action driven by loss-cone anisotropy,the rare phenomena of slow drift band consisting of spikes were interpreted by spike source moving back and forth along the magnetic ***,the estimations of the narrow bandwidths of spike given by electron cyclotron maser theory coincided well with the observations.

关键词：太阳耀斑微波爆裂太阳活动天文学

Comparisons of Infrared Colors and Emission-line Intensities between Two types of Seyfert 2.Galaxies

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Chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 408-418页

作者： Lin-Peng Cheng, Yong-Heng Zhao and Jian-Yan Weinational astronomical {2., Chinese academy of sciences, beijing 100012 national astronomical {2. CAS NAOC Beijing China

We study the relation between the infrared colors, [OIII] emission lines, gaseous absorbing column density (NH),and the detectability of the polarized (hidden) broad-line region (HBLR) in a large sample of 75 Seyfert 2.galaxies (Sy2.). From the indicators of star-formation activity, f60/f100 and LFIR/LB, we find some evidence that the Sy2. without HBLR show higher star-formation activities than those with HBLR, in agreement with previous prediction. Also, we confirm that the HBLR Sy2. tend to have a larger luminosity ratio of the core to the host galaxy, suggesting that the HBLR Sy2. display more powerful AGN activity. However, the level of obscuration found in previous papers is nearly indistinguishable between the two types of Sy2.. The results support the statement that the non-HBLR Sy2., with a weaker core component and a stronger star-formation activity component, are intrinsically different from the HBLR Sy2., which are Sy1 systems with a hidden powerful AGN core and a low star-formation activity. The indications are that the non-HBLR Sy2. might be at an earlier evolutionary phase than the HBLR Sy2..

关键词： galaxies: active - galaxies: Seyfert - polarization - star formation

k-Nearest Neighbors for automated classification of celestial objects

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Science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 916-922页

作者： LI LiLi1,2.3, ZHANG YanXia1 & ZHAO YongHeng1 1 national astronomical {2., Chinese academy of sciences, beijing 100012, china 2.Department of Physics, Hebei Normal University, Shijiazhuang 050016, china 3 Weishanlu Middle School, Tianjin 3002.2. china national astronomical {2. Chinese Academy of Sciences Beijing China Department of Physics Hebei Normal University Shijiazhuang China Weishanlu Middle School Tianjin China

The nearest neighbors (NNs) classifiers, especially the k-Nearest Neighbors (kNNs) algorithm, are among the simplest and yet most efficient classification rules and widely used in practice. It is a nonparametric method of pattern recognition. In this paper, k-Nearest Neighbors, one of the most commonly used machine learning methods, work in automatic classification of multi-wavelength astronomical objects. Through the experiment, we conclude that the running speed of the kNN classier is rather fast and the classification accuracy is up to 97.73%. As a result, it is efficient and applicable to discriminate active objects from stars and normal galaxies with this method. The classifiers trained by the kNN method can be used to solve the automated classification problem faced by astronomy and the virtual observatory (VO).

关键词： k-Nearest Neighbors data analysis classification astronomical catalogues

Wavelet analysis of sunspot relative numbers

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Chinese Science Bulletin 2002年第7期47卷 609-612页

作者： HAN Yanben & HAN Yonggangnational astronomical {2., Chinese academy of sciences, beijing 100012, china Department of Applied Mathematics, beijing Polytechnic University, beijing 10002., china national astronomical {2. Chinese Academy of Sciences Beijing China Department of Applied Mathematics Beijing Polytechnic University Beijing China

The time series of the monthly smoothed sun-spot numbers in 1749-2.00 is analyzed with the wavelet. The result shows that besides the known time-variation of the period about 11 years, other main periods of the sunspot numbers, such as the periods of about 100 years and so on, vary with time. We suggest that the time-variation of the main periods is the manifestation of the complex variation of sunspot numbers. It is significant to make a thorough study of the character and mechanism of the time-variation of the periods for proving prediction of sunspot numbers, especially for understanding the variation process of sunspot numbers.

关键词： sunspot numbers prediction wavelet time-variation.

The Variability of Hardness Ratio 1 observed by ROSAT:Narrow-Line Seyfert 1 Galaxies versus Broad-Line Seyfert 1 Galaxies

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Chinese Journal of Astronomy and Astrophysics 2002年第3期2卷 207-215页

作者： Lin-Peng Cheng , Jian-Yan Wei and Yong-Heng Zhaonational astronomical {2., Chinese academy of sciences, beijing 100012 national astronomical {2. Chinese Academy of Sciences Beijing 100012

We examined the correlation between the ROSAT Hardness Ratio 1 and Count Rates eight Narrow-line Seyfert 1 Galaxies (NLSls) and 14 Broad-line Seyfertl Galaxies (BLSls). We found that six of the NLSls show a positive HR1-CTs correlation, and seven of the BLSls, a negative correlation. The other two NLSls and seven BLSls do not show any clear HR1-CTs correlation. Thus, the spectral behavior is statistically different for the NLSls and BLSls. The different behaviors can possibly be interpreted in terms of a stable 'soft excess' that is strong in NLSls and weak in BLSls, plus a power law component, common to both, which softens with increasing flux.

关键词： galaxies: Seyfert - galaxies: active - X-ray: galaxies

Analysis on the positioning precision of CAPS

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Science china(Physics,Mechanics & Astronomy) 2009年第3期52卷 328-332页

作者： JI YuanFa1,2.& SUN XiYan1,2.1 national astronomical {2., Chinese academy of sciences, beijing 100012, china 2.Applied Science and Technology College, Guilin University of Electronic Technology, Guilin 541004, china national astronomical {2. Chinese Academy of Sciences Beijing China Applied Science and Technology College Guilin University of Electronic Technology Guilin China

As a newly developed satellite positioning system, the Chinese Area Positioning System (CAPS) is a typical direct sequence spread spectrum ranging system like GPS. The positioning precision of such navigation signals depends on many factors, including the pseudo-code rate, the signal to noise ratio, the processing methods for tracking loops and so on. This paper describes the CAPS link budget, the solution approach for CAPS positioning, focusing on the autocorrelation function feature of C/A code signals. The CAPS signal measurement precision is studied by the software approach together with theoretical analysis of the range resolution. Because the conventional Delay Lock Loop (DLL) is vul- nerable to the impact of noise, a narrow correlator and multiple correlators as well as the corresponding discrimination methods of phases are proposed, which improves the robustness of DLL and the code-phase resolution of the measurement. The results show that the improvement of the DLL structure and the discrimination method are the most important way to improve the ranging resolution. Theoretical analysis and experimental results show that a CAPS receiver could reach a 2.-m positioning precision by using three satellites with a supported height from an altimeter.

关键词： satellite navigation receiver narrow correlation tracking loop

The Influence of Panel Gaps on the System NoiseTemperature of the FAST

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Chinese Journal of Astronomy and Astrophysics 2001年第2期1卷 190-194页

作者： Yan Su and Guo-Ding Li (1 beijing astronomical Observatory, {2. astronomical observatories, Chinese academy of sciences, beijing 100012 2.The Laboratory of Microwave and Digital Communication Technology, Tsinghua University, beijing 100084) beijing astronomical Observatory National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 The Laboratory of Microwave and Digital Communication Technology Tsinghua University Beijing 100084

A Five-hundred-meter Aperture Spherical Telescope (FAST), the largest single dish in the world, is proposed to be built in one of the karst depressions in Guizhou province. The main spherical reflector is to consist of about two thousand small panels, which can be adjusted to fit a paraboloid in real time. There are many slit-like gaps across the aperture due to manufacturing errors thermal effects and deviations between a sphere and a paraboloid. The influence of the energy leakage of the narrow gaps on the system noise temperature of the FAST reflector is discussed in this paper.

关键词： telescopes - methods: analytical - energy leakage