2000—2050年中国可见的水星凌日事件

本文根据DE2 0 0历表 ,计算了 2 0 0 0— 2 0 5 0年间发生的水星凌日的地心天象 ,并进一步计算了中国各直辖市、省会、自治区首府等三十四个城市的见凌情况     

若干恒星形成区的^12CO（J=1—0）与^13CO（J=1—0）观测

首次利用紫金山天文台青海观测站13.7m毫米波射电望远镜对若干分子云与恒星形成区的~(12)CO(J=1—0)和~(13)CO(J=1—0)分子辐射进行了观测,得到了各自中心位置的谱线轮廓。作为一个实例本文将介绍如何通过对分子云~(12)CO(J=1—0)和~(13)CO(J=1—0)谱线的综合分析与计算得到云中的物理参数。     

利用Lageos 1 SLR资料解算1990-2001年的地球定向参数

利用 12年的Lageos 1卫星激光测距资料 (1990 - 2 0 0 1)解算得到了地球定向参数 (EOP) ,将该序列的结果与同期的EOP(IERS)C0 4进行比较 ,其外符精度为 :极移XP— 0 .4 0mas,YP— 0 .4 2mas ,日长变化Dr— 0 .0 35ms。     

上海—埃弗尔斯堡(西德)甚长基线干涉(VLBI)实验的综合结果

1981年11月上海和埃弗尔斯堡(Effelsberg)之间完成了中—西德之间的首次VLBI实验。所有被观测的射电源都获得干涉条纹。本文发表初步分析得出的综合结果:(1)测定了上海—埃弗尔斯堡基线向量,内部符合达2—3米;(2)测定了射电源1739+52和1928+73的位置,精度0″.05—0″.08,均未经电离层延迟误差的改正;(3)测定了14颗河外射电源的相关流量和可见度,并发现射电源1928+73具有双源结构,间距为8.9毫角秒。     

利用Lageos1SLR资料解算1990—2001年的地球定向参数

利用12年的Lageos1卫星激光测距资料(1990—2001)解算得到了地球定向参数(EOP)，将该序列的结果与同期的EOP(IERS)CO4进行比较，其外符精度为：极移Xp—0．40mas，Yp—0．42mas，日长变化Dr—0．035ms。     

CIRA 1972在160—2000公里高度范围的大气密度的一种分析模型

本文导出了与CIRA 1972内符合精度较高的一种分析模型. 模型包含:周日变化(F_1、F_2),标高随高度的变化(μ),半年变化(其小因子合并到ρ_0、H、μ中处理)、氦的季节-纬度变化(S_5~0、S_5~T),以及周日变化、氦的季节-纬度变化和地磁活动随高度的变化(H_1、S_5~x、K). 模型的内符合精度,在160—250公里约为5％;在250—400公里约12％;在400—2000公里约25％.适用于人造卫星大气阻力摄动的分析型公式.     

太阳射电分米波U型暴分析

本文介绍了由捷克Ondˇrejov天文台观测到的 1 992年 8月 2 2日 1 2 :36 :2 6— 1 2 :36 :32UT发生的U型暴 ,U型暴的频率范围为 1 .0— 2 .8GHz,在国际上尚属首例 .从分析得到以下几点结论 :(1 )上下臂的频漂率分别为 1 .2 5和 0 .2 2 5GHz/s,其电子束流的速度分别为 0 .38c和 0 .2 6c ,它是由等离子体二次谐波发射造成的 .(2 )上升臂的爆发衰减时间常数大于下降臂的 .(3)频谱极大频率随时间变化呈现出从高频到低频再到高频的变化 .(4)上升臂的频宽大于下降臂的约一倍左右 ,这与上升臂频漂远大于下降臂的有关 .(5 )从频宽得到上、下臂的速度弥散分别为 (Δvv) a=0 .42和 (Δvv) d=0 .47.     

2000—2049年行星天象（一）

本文给出 2 0 0 0 - 2 0 4 9年行星天象的一部分 ,包括水星、金星的东、西大距 ,留及上、下合日 ;金星最亮和最接近地球 ;外行星冲日、最接近地球、合日、留 ;地球和外行星过远近日点计1 5个表     

分子外流区W75—N的^13CO（J=1—0）观测

使用日本国名古屋大学4m射电望远镜于1994年12月22日对分子外流区W75—N的~(13)CO(J=1-0)跃迁(110GHz)进行了观测。得到了该区域的7×7个观测点(grid 为2角分)的积分强度MAP图,通过对所观测到的双峰谱线进行研究,得到了该区域~(13)CO源的两个成份。     

1935.0—1941.0年緯度变化的周期項

由1935.0—1941.0年的五个纬度台站:水泽、基塔布、卡尔洛福特、盖切尔斯堡和乌基阿的纬度观测资料,得到1)星表的系统误差将在纬度变化中引入虚假成分和影响纬度变化中的周年和半年周期成分;2)用新的星表系统重新推算纬度变化,求得张德勒周期平均为414日,振幅为0″.074;周年周期平均为362日,振幅为0″.140;3)在分析纬度观测结果时受到对各台站不一样的地方性因素的影响。     

视超光速候选源0208-512和2243-123

本文叙述南天区５ＧＨｚＶＬＢＩ普查的第二轮观测中所发现的视超光速候选源,０２０８－５１２和２２４３－１２３,这些结果尚待进一步的观测加以证实．     

Mars atmospheric water vapor abundance: 1991-1999, emphasis 1998-1999

Our ground-based measurements of martian atmospheric water vapor, made throughout Ls=34° to 249°, 24 September 1998 to 23 November 1999, during Mars year 24 (MY 24), show changes in Mars' humidity on hourly, daily, and seasonal timescales. We made concomitant measurement of nearby CO₂ bands, and when possible, results were corrected for aerosol extinction using aerosol optical depths derived from our own CO₂ analysis. Where there is spatial and temporal overlap, similar results are obtained for water vapor abundances and aerosol opacities as those observed from the Thermal Emission Spectrometer on Mars Global Surveyor. In addition some further discussion of our published earlier water vapor measurements (1991-1995) is included. Six results from this data set are: (1) the measured aerosol opacity in Mars atmosphere was variable but not greater than τ=1, with almost no clear atmosphere being observed, (2) measurements made with the slit crossing many hours of local time on Mars' Earth-facing disk show a diurnal pattern with highest abundances at mid-day and low abundance in very early morning and late afternoon for some but not all measurements, (3) water vapor abundance is patchy on hourly and daily time scales but follows the usual seasonal trends seen by instrumentation on the Mars Atmospheric Water Detector on the Viking Orbiters and by the Thermal Emission Spectrometer on Mars Global Surveyor, (4) there is a slight longitudinal correlation with the ground-ice observed by the Gamma Ray Spectrometer on Mars Odyssey, (5) there is evidence of the Low Southern Latitude Summer Minimum in our water vapor measurements but our data set for southern summer is limited, and (6) MY 24 appears to be wetter than MY 22 and MY 23.     

Variability in the southern blazars PKS 1921-293 and PKS 2155-152

We report results of 1435 MHz rapid variability observations of the southern extragalactic sources PKS 1921-293 and PKS 2155-152. Both objects displayed variability in their flux densities on timescales of the order of one and two weeks, respectively. A brief discussion on the origin of this variability is presented, with a comparison of different models that could account for the observations.Fellow of CONICET.     

CCD polarimetry of the solar corona at the 1997-03-09 solar eclipse

We give the treated results of our CCD polarimetric data of the solar corona obtained during the 1997-03-09 total eclipse, including the profiles of absolute brightness and degree of polarization along 12 directions (including the two equatorial and two polar directions) in the middle corona (1.6−3.2 R_⊙)     

Three-Dimensional Magnetic Reconnection in Astrophysical Plasmas - Kinetic Approach

Reconnection is the most efficient way to release the energy accumulated in the tense astrophysical magnetoplasmas. As such it is a basic paradigm of energy conversion in the universe. Astrophysical reconnection is supposed to heat plasmas to high temperatures, it drives fast flows, winds and jets, it accelerates particles and leads to structure formation. Reconnection can take place only after a local breakdown of the plasma ideality, enabling a change of the magnetic connection between plasma elements. After Giovanelli first suggested magnetoplasma discharges in 1946, reconnection has usually been identified with vanishing magnetic field regions. However, for the last ten years a discussion has been going on about the structure of 3 D reconnection, e.g., whether in 3 D it is possible also without magnetic nulls or not. We first shortly review the relevant magnetostatic and kinematic fluid theory results to argue than that a kinetic approach is necessary to reveal the generic three-dimensional structure and dynamics of reconnection in collisionless astrophysical plasmas. We present results about the 3 D structure of kinetic reconnection in initially antiparallel magnetic fields. They were obtained by selfconsistently considering ion and electron inertia as well as dissipative wave-particle resonances. In this approach reconnection is a natural consequence of the instability of thin current sheets. We present the results of a nonlocal linear dispersion theory and describe the nonlinear evolution of the instability using numerical particle code simulations. The decay of thin current sheets directly leads to a configurational instability and three-dimensional dynamic reconnection. We report the resulting generic magnetic field structure. It contains pairs of magnetic nulls, connected by separating magnetic flux surfaces through which the plasma flows and along which reconnection induces large parallel electric fields. Our results are illustrated by virtual reality views and movies, both stored on the attached CD-ROM and also being available from the Internet. This revised version was published online in July 2006 with corrections to the Cover Date.     

The First Photometric Analyses Of Four New Discovered Ew-Type Eclipsing Binaries: GSC 1848-1264, GSC 0804-0118, GSC 0619-0232 And GSC 2936-0478

Photometric solutions of four new discovered W UMa-type binaries were carried out for the first time by using the 2003 version of the W-D program. It is discovered that all of the four systems are over-contact binaries. Two binaries, GSC 0804-0118 and GSC 2936-0478, are of A-subtype, while two other binaries, GSC 1848-1264 and GSC 0619-0232, are of W-subtype. From our solutions, the fundamental orbital and physical parameters were determined. For GSC 0619-0232 and GSC 2936-0478, the asymmetries of the light curves (i.e., the O'Connell effect) were explained by the presence of dark spots on the more massive components. Our photometric results reveal that GSC 0619-0232 is an important and interesting system. It is a W-type over-contact binary with a low mass ratio of q = 0.100 and a high over-contact degree of f = 93.4%, which suggests that GSC 0619-0232 may be evolved into a single rapid-rotating star.     

Electron-heated flare models - alive and well

The idea that deka-keV electrons, accelerated during the primary energy release, are responsible for the bulk of the impulsive phase energy transport in solar flare atmospheres has been around for quite some time now. With the advent of (i) detailed numerical calculations of the hydrodynamic response of the atmosphere to the energy input from such electrons, and (ii) the observations made during the last solar maximum of the spatial, spectral, and temporal behavior of flare-associated emissions in a variety of wavelength ranges, we have now reached a point where quantitative tests of the thick-target electron-heated model (Brown, 1973) are possible. Here I describe some recent results of such quantitative tests.     

Multi-Wavelength Variability in PKS 2155-304

We study multi-wavelength variability in BL Lacertae object PKS 2155-304 in the frame of the time dependent one-zone synchrotron self-Compton (SSC) model, where stochastic particle acceleration is taken into account. In this model, a homogeneously and isotropically spherical structure is assumed, the Fokker–Planck type equation which describes the evolution of the particles energy is numerically solved, and the synchrotron and self-Compton components from the spherical blob are calculated. Our results can reproduce observed spectra energy distribution (SED) and give definite predictions for the flux and spectral variability of PKS 2155-304. We find that particle injection rate, magnetic field and Doppler factor in the acceleration zone are important parameters for explaining its flaring behaviour.     

Electron-heated flare models - alive and well

The idea that deka-keV electrons, accelerated during the primary energy release, are responsible for the bulk of the impulsive phase energy transport in solar flare atmospheres has been around for quite some time now. With the advent of (i) detailed numerical calculations of the hydrodynamic response of the atmosphere to the energy input from such electrons, and (ii) the observations made during the last solar maximum of the spatial, spectral, and temporal behavior of flare-associated emissions in a variety of wavelength ranges, we have now reached a point where quantitative tests of the thick-target electron-heated model (Brown, 1973) are possible. Here I describe some recent results of such quantitative tests.

     

Variation of the broad X-ray iron line in MCG–6-30-15 during a flare

We report results on the broad iron emission line of the Seyfert galaxy MCG–6-30-15, obtained from the second long ASCA observation in 1997. The time-averaged profile of the broad line is very similar to that seen with ASCA in 1994, so confirming the detailed model fit then obtained. A bright flare is seen in the light curve, during which the continuum was soft. At that time the emission line peaks around 5 keV and most of its emission is shifted below 6 keV with no component detected at 6.4 keV  (  This can be interpreted as the result of an extraordinarily large gravitational redshift owing to a dominant flare occurring very close to the black hole at a radius of  ≲5  .