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Avoided crossings between non-radial modes in low mass RGB stars

Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： Jun-Jun Guo1,2,3,Yan Li1,2 and Xiang-Jun Lai1,2 1 national astronomical observatories/Yunnan Observatory,chinese academy of sciences, Kunming 650011,china 2 key laboratory for the Structure and Evolution of Celestial Objects,chinese academy of sciences,Kunming 650011,china 3 Graduate University of chinese academy of sciences,beijing 100049,china national astronomical observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese academy of sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2 and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2 and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2 and 3 in frequency and periodéchelle diagrams and find modes of l=2 and 3 fit the two relations better;they are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2 and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2 and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2 and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

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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 210008,china 2 national astronomical observatories,chinese academy of sciences,beijing 100012,china Purple Mountain Observatory Chinese Academy of Sciences Nanjing China national astronomical observatories Chinese Academy of Sciences Beijing China

The solar flare(1N/C5.3) occurred in NOAA 8742 on October 27,1999,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 04:27:42 UT,peaked at 04:28:42 UT and ended at 04:29:18 *** 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

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Calibration of Vector Magnetogram with the Nonlinear Least-squares Fitting Technique

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chinese Journal of Astronomy and Astrophysics 2004年第4期4卷 365-376页

作者： Jiang-TaoSu Hong-QiZhang nationalastronomicalobservatories ChineseAcademyofSciencesBeijing100012

To acquire Stokes profiles from observations of a simple sunspot with the Video Vector Magnetograph at Huairou solar Observing Station (HSOS), we scanned the FeI λ5324.19 A line over the wavelength interval from 150mA redward of the line center to 150mA blueward, in steps of 10mA. With the technique of analytic inversion of Stokes profiles via nonlinear least-squares, we present the calibration coefficients for the HSOS vector magnetic magnetogram. We obtained the theoretical calibration error with linear expressions derived from the Unno-Becker equation under weak-field approximation.

关键词： Sun: activity - Sun: magnetic fields - sunspots

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Metallicity calibration for solar type stars based on red spectra

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Research in Astronomy and Astrophysics 2011年第5期11卷 563-576页

作者： Jing-KunZhao GangZhao Yu-QinChen A-LiLuo keylaboratoryofOpticalAstronomy NationalAstronomicalObservatoriesChineseAcademyofSciencesBeijing100012China

Based on a high resolution and high signal-to-noise ratio （S/N） spectral analysis of 90 solar-type stars, we have established several new metaUicity calibrations in the Tefr range [5600, 6500] K based on red spectra with the wavelength range of 560-880 nm. The new metallicity calibrations are applied to determine the metallicity of solar analogs selected from Sloan Digital Sky Survey （SDSS） spectra. There is a good consistent result with the adopted value presented in SDSS-DR7 and a small scatter of 0.26 dex for stars with S/N 〉 50 being obtained. This study provides a new reliable way to derive the metallicity for solar-like stars with low resolution spectra. In particular, our calibrations are useful for finding metal-rich stars, which are missing in the SEGUE Stellar Parameter Pipeline.

关键词： techniques: radial velocities - stars: temperatures - stars: abundances

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Time-variation of the near 5-month period of sunspot numbers

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chinese Science Bulletin 2002年第23期47卷 1969-1973页

作者： HAN Yanben1 & HAN Yonggang1,21. national astronomical observatories, chinese academy of sciences, beijing 100012, china 2. Department of Applied Mathematics, beijing Polytechnic University, beijing 100022, china national astronomical observatories Chinese Academy of Sciences Beijing China Department of Applied Mathematics Beijing Polytechnic University Beijing China

The variation of the near 5-month period of sunspot numbers is discussed on the basis of the wavelet transform of the daily sunspot number series in the 14th-22nd solar cycles. The result shows that the period exists in every cycle and its energy density (amplitude) is comparatively large in the peak section of the cycle. In the distinct cycle, the length and intensity of the period is different, which means that the period varies with time. The near 25-day period is also analyzed and it is found to be time-variable and even not very stable in the peak section of the cycle. The variations of the two periods show that the near 5-month period should not be simply regarded as the multiples of the near 25-day period.

关键词： solar activity sunspot time-variation wavelet.

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Anisotropic Beam Model for the Spectral Observations of Radio Burst Fine Structures on 1998 April 15

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chinese Journal of Astronomy and Astrophysics 2001年第5期1卷 475-482页

作者： V.G. LedenevE-mail:yyh@*** , Yi-Hua Yan, and Qi-Jun Fu (national astronomical observatories, chinese academy of sciences, beijing 100012) (Institute of solar-Terrestrial Physics, Siberian Division of Russian academy of sciences 664033, Irkutsk, P. 0 Institute of solar-Terrestrial Physics Siberian Division of Russian Academy of Sciences 664033 Irkutsk P. O. Box 4026 Russia

A fine structure consisting of three almost equidistant frequency bands was observed in the high frequency part of a solar burst on 1998 April 15 by the spectrometer of beijing astronomical Observatory in the range 2.6-3.8 GHz. A model for this event based on beam-anisotropic instability in the solar corona is presented. Longitudinal plasma waves are excited at cyclotron resonance and then transformed into radio emission at their second harmonic. The model is in accordance with the observations if we suppose a magnetic field strength in the region of emission generation of about 200 G.

关键词： Sun: radio radiation Sun: activity - Sun: corona

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solar release time of solar energetic particles and associated acceleration source in corona

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chinese Science Bulletin 2008年第2期53卷 161-168页

作者： LE GuiMing1,2,3,4, TANG YuHua1 & HAN YanBen4 1 Department of Astronomy, Nanjing University, Nanjing 210093, china 2 key laboratory of Radiometric Calibration and Validation for Environmental Satellites, china Meteorological Administration, beijing 100081, china 3 national Center for Space Weather, china Meteorological Administration, beijing 100081, china 4 national astronomical observatories, chinese academy of sciences, beijing 100012, china Department of Astronomy Nanjing University Nanjing China key laboratory of Radiometric Calibration and Validation for Environmental Satellites China Meteorological Administration Beijing China national Center for Space Weather China Meteorological Administration Beijing China national astronomical observatories Chinese Academy of Sciences Beijing China

solar energetic particles (SEPs) are accelerated in corona at an early phase of solar energetic particle events (SEPE). The acceleration mechanism of SEPs in corona can only be inferred from an analysis of multi-band observational data, as the observation of SEPs is usually made around 1AU. In this context, people have investigated spectrums, charge state, solar release time (SRT), and multi-band data of SEPEs, in an attempt to judge the acceleration mechanism of SEPs. The SRT computation of SEPs is an important and commonly used approach to study the acceleration mechanism of SEPs in corona. This paper reviews some important findings concerning the SRT computation of SEPs, and analyzes different merits of each approach for such calculation, based on a range of SEPE case studies. This paper also analyzes and discusses both possible and actual acceleration mechanisms of a number of SEPEs, by calculating the SRT of the SEPEs. Finally, the paper summarizes the possible problems in studying an acceleration mechanism of SEPEs inferred from the SRT of SEP.

关键词：阳光释放时间加速度电晕太阳耀斑

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A statistical study of the relation between soft X-ray excess and accretion disk

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Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 102-105页

作者： LIU JieYing1,2,3 & QIAO ErLin1,2 1 national astronomical observatories/Yunnan Observatory,chinese academy of Science,Kunming 650011,china 2 key laboratory for the Structure and Evolution of Celestial Objects,chinese academy of sciences,Kunming 650011,china 3 Graduate University of chinese academy of sciences,beijing 100049,china 1. national astronomical observatories/Yunnan Observatory Chinese Academy of Science Kunming 650011 China 2. key laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China 3. Graduate University of chinese academy of sciences Beijing 100049 China

To study the origin of the soft X-ray excess,we compile a sample of 94 unobscured,radio-quiet QSOs and Seyfert galaxies with available data from GALEX and *** find that 50 sources show strong soft X-ray excess and the other 44 show weak/no soft X-ray *** analyses of the data indicate that the difference in soft X-rays is mainly but not only resulting from different accretion rates(in units of Eddington rate).The statistical study of the sources with soft X-ray excess shows that the strength of soft X-ray excess weakly and positively correlates with the Eddington ratio and increases with the increase of the strength of UV radiations relative to the *** that the UV emissions are from the thin disk,the correlations imply that the origin of soft X-ray excess is associated with the thin disk,either by means of Comptonization of the disk photons or in some other ways.

关键词： accretion:accretion disks ultraviolet:galaxies X-rays:galaxies

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Birthrates and delay times of Type Ia supernovae

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 586-590页

作者： WANG Bo1,2,3, LIU ZhengWei1,2,3, HAN YunKun1,2,3, LEI ZhenXin1,2,3, LUO YangPing1,2,3 & HAN ZhanWen1,2 1national astronomical observatories/Yunnan Observatory, chinese academy of sciences, Kunming 650011, china 2key laboratory for the Structure and Evolution of Celestial Objects, chinese academy of sciences, Kunming 650011, china 3Graduate University of chinese academy of sciences, beijing 100049, china 1. national astronomical observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China2. Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China3. Graduate University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (SD) model accounts for only about 1/2-2/3 of the observations. If a single starburst is assumed, the distribution of the delay times of SNe Ia from the SD model is a weak bimodality, where the WD + He channel contributes to the SNe Ia with delay times shorter than 100 Myr, and the WD + MS and WD + RG channels to those with age longer than 1 Gyr.

关键词： binaries: close stars: evolution supernovae: general white dwarfs

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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 observatories, chinese academy of sciences, beijing 100012, china 2 Applied Science and Technology College, Guilin University of Electronic Technology, Guilin 541004, china 1. national astronomical observatories Chinese Academy of Sciences Beijing 100012 China 2. Applied Science and Technology College Guilin University of Electronic Technology Guilin 541004 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 20-m positioning precision by using three satellites with a supported height from an altimeter.

关键词： satellite navigation receiver narrow correlation tracking loop

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