2000年度上海天文台卫星激光测距观测报告     

杨福民  张忠萍  陈婉珍  陈菊平  徐永平  李鑫 《中国科学院上海天文台年刊》2002,(1)

介绍了 2 0 0 0年度上海天文台卫星激光测距观测和系统的改进情况  相似文献   

The formation of ultracompact dwarf galaxies     

MichaelFellhauer  PavelKroupa 《Monthly notices of the Royal Astronomical Society》2002,330(3):642-650

Recent spectroscopic observations of galaxies in the Fornax Cluster reveal nearly unresolved 'star-like' objects with redshifts appropriate to the Fornax Cluster. These objects have intrinsic sizes of ≈100 pc and absolute B -band magnitudes in the range  −14< M _B<−11.5 mag  and lower limits for the central surface brightness   μ _B≳23 mag arcsec⁻²  , and so appear to constitute a new population of ultracompact dwarf galaxies (UCDs). Such compact dwarfs were predicted to form from the amalgamation of stellar superclusters (by Kroupa) , which are rich aggregates of young massive star clusters (YMCs) that can form in collisions between gas-rich galaxies. Here we present the evolution of superclusters in a tidal field. The YMCs merge on a few supercluster crossing times. Superclusters that are initially as concentrated and massive as knot S in the interacting Antennae galaxies evolve to merger objects that are long-lived and show properties comparable to the newly discovered UCDs. Less massive superclusters resembling knot 430 in the Antennae may evolve to ω Cen-type systems. Low-concentration superclusters are disrupted by the tidal field, dispersing their surviving star clusters while the remaining merger objects rapidly evolve into the   μ _B− M _B  region populated by low-mass Milky Way dSph satellites.  相似文献   

Modelling the chromosphere and transition region of ε Eri (K2 V)     

S. A. Sim  C. Jordan 《Monthly notices of the Royal Astronomical Society》2005,361(3):1102-1120

Measurements of ultraviolet line fluxes from Space Telescope Imaging Spectrograph and Far-Ultraviolet Spectroscopic Explorer spectra of the K2-dwarf ε Eri are reported. These are used to develop new emission measure distributions and semi-empirical atmospheric models for the chromosphere and lower transition region of the star. These models are the most detailed constructed to date for a main-sequence star other than the Sun. New ionization balance calculations, which account for the effect of finite density on dielectronic recombination rates, are presented for carbon, nitrogen, oxygen and silicon. The results of these calculations are significantly different from the standard Arnaud & Rothenflug ion balance, particularly for alkali-like ions. The new atmospheric models are used to place constraints on possible first ionization potential (FIP)-related abundance variations in the lower atmosphere and to discuss limitations of single-component models for the interpretation of certain optically thick line fluxes.  相似文献   

致密对称源OQ208自行的研究     

王保田  张海燕 《天文研究与技术》2007,4(2):121-125

利用美国甚长基线阵,在5GHz和8GHz波段观测致密对称源(CSO)OQ208,由获得的总流量图均显示OQ208是由2个主要的射电结构组成。5GHz波段在该源西南(SW)部分和东北(NE)部分都探测到2个子源。8GHz波段在该源(SW)部分探测到2个子源,而在(NE)部分探测到3个子源。在5GHz波段,根据子源A和D自1993年到2001年间的5个时段VLBI观测成图结果,拟合出它们的分离速度为0.037±0.006mas/a(年)。在8GHz波段,根据1994年到2002年间的9个时段观测数据,获得子源A和C的分离速度为0.046±0.009mas/a。  相似文献   

Herbig-Haro objects—tracers of the formation of low-mass stars and sub-stellar objects     

Bringfried Stecklum  Helmut Meusinger  Dirk Froebrich 《Astrophysics and Space Science》2007,311(1-3):63-67

Herbig-Haro objects (HHOs) are caused by outflows from young objects. Since the outflow relies on mass accretion from a circumstellar disk, it indicates ongoing growth. Recent results of infrared observations yielded evidence for disks around brown dwarfs. This suggests that at least a certain fraction of brown dwarfs forms like stars. Thus, young sub-stellar objects might cause HHOs as well. We present selected results of a general survey for HHOs based on DSS-II plates and CCD images taken with the Tautenburg Schmidt telescope. Numerous young objects could be identified due to their association with newly detected HHOs. In some cases the luminosity is consistent with very low-mass stars or close to sub-stellar values. This holds for L1415-IRS and a few infrared sources embedded in other dark clouds (e.g., GF9, BHR111). The question on the minimum mass for outflow activity is addressed.  相似文献   

Critical Approach to Methods of Glacier Reconstruction in High Asia and Discussion of the Probability of a Qinghai-Xizang （Tibetan） Inland Ice     

Matthias Kuhle 《山地科学学报》2007,4(2):91-124

This overview discusses old and new results as to the controversy on the past glacier extension in High Asia, which has been debated for 35 years now. This paper makes an attempt to come closer to a solution. H.v. Wissmann's interpretation (1959) of a small-scale glaciation contrasts with M. Kuhle's reconstruction (1974) of a large-scale glaciation with a 2.4 million km2 extended Qinghai-Xizang (Tibetan) inland glaciation and a Himalaya-Karakorum icestream network. Both opinions find support but also contradiction in the International and Chinese literature (Academia Sinica). The solution of this question is of supraregional importance because of the subtropical position of the concerned areas. In case of large albedo-intensive ice surfaces, a global cooling would be the energetical consequence and, furthermore, a breakdown of the summer monsoon. The current and interglacial heat-low above the very effective heating panel of the Qinghai-Xizang (Tibetan) Plateau exceeding 4000 m, which gives rise to this monsoon circulation, would be replaced by the cold-high of an inland ice. In addition, the plate-tectonically created Pleistocene history of the uplift of High Asia — should the occasion arise up to beyond the snowline (ELA) —would attain a paleoclimatically great, perhaps global importance. In case of a heavy superimposed ice load, the question would come up as to the glacio-isostatic interruption of this primary uplift. The production of the loesses sedimentated in NE-China and their very probable glacial genesis as well as an eustatic lowering of the sea-level by 5 to 7 m in the maximum case of glaciation are immediately tied up with the question of glaciation we want to discuss. Not the least, the problems of biotopes of the sanctuary-centres of flora and fauna, i.e., interglacial re-settlement, are also dependent on it. On the basis of this Quaternary- geomorphological-glaciological connection, future contributions are requested on the past glaciation, the current and glacial permafrost table and periglacial development, the history of uplift, and the development of Ice Age lakes and loess, but also on the development of vegetation and fauna in High Asia.  相似文献   

南极洛多姆冰帽BJ钻孔粒雪层的热学性质及其温度分布          下载免费PDF全文

任贾文  秦大河  黄茂桓 《极地研究》1989,1(3):18-26

根据详细的密度资料,对洛多姆冰帽BJ钻孔粒雪层的热学性质进行了讨论。应用非均匀介质热传导方程描述活动层温度分布。通过两种简化的层状结构和竖向运动模型给出了解析解。计算和实测温度差异的分析表明边界条件的选取非常重要。  相似文献   

21cm波段太阳爆发中的精细结构     

龚元芳  吕松泉  尚琼珍  胡汉明  施硕彪  李琼英 《中国天文和天体物理学报》1989,(1)

本文简要介绍了云南天文台新建立的21cm波段快速(不中断采样)记录系统,及使用该系统观测到的快速尖峰事件。系统得到的太阳分米波段爆发中不同时间尺度的精细结构与Stu-rroch等提出的太阳耀斑中能量释放的模式相一致。  相似文献   

Long-period variations of sea-level in Australasia     

J. I. Pariwono  J. A. T. Bye  G. W. Lennon 《Geophysical Journal International》1986,87(1):43-54

Summary. The ability of the Australian sea-level monitoring network is assessed in the investigation of long-period sea-level signals. Through the character of coastal long waves, seasonal variations in level and inter-annual level anomalies, the importance of the south coast of the Continent is identified as a coherent indicator of large-scale marine and atmospheric teleconnections. The source of the sea-level signal is investigated by the tracing of progressive features, by the numerical modelling of wind stress over the Southern Ocean, by the modelling of the effect of monsoonal rains over the Indian Ocean and the mass transport through the Indonesian Strait. These features are related to the ENSO cycle which for the first time is linked, inter alia , with Southern Ocean mechanisms.  相似文献   

无力场模型黑子上空的纵向磁场梯度     

林元章  邬飞 《中国天文和天体物理学报》1987,(4)

本文按常α无力场模型计算了1980年10月23日Boulder 2744活动区前导黑子的纵向磁场随高度的变化,并与用CIV 1548谱线观测得到的色球一日冕过渡区的磁场资料相结合,求得CIV 1548发射区的有效高度。这些结果与文献[4]中对同一黑子用势场模型推求的结果有很大差别。从而表明,势场和无力场在某些方面导致的结果是极不相同的。鉴于观测已表明活动区上空存在电流的事实,在活动区磁场的模拟中,特别是在强扭曲活动区磁场的计算中,应当避免采用势场,而尽可能采用无力场模型。  相似文献