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161.
162.
新宇 《紫金山天文台台刊》2003,(2)
作为目前研究复杂恒星系统的有力工具 ,星族合成方法是建立在单星演化理论基础之上的 ,因此 ,必然有其不完善性存在 ,尤其当系统中的双星成分不容忽视时。作为演化星族合成方法的基本单元 ,简单恒星星族模型的构成即排除了双星贡献。本文中 ,我们以银河系疏散星团为简单恒星星族模板 ,构造出一系列简单恒星星族积分光谱。从中我们可以看到 :蓝离散星这类理论上主要来源于双星系统的恒星 ,对星团积分光谱的紫外及蓝端有很大影响 ,从而造成简单恒星星族积分光谱能量分布的改变。这种改变势必影响对星团年龄及其它一些物理参量的判定 ,并最终影响星族合成的结果。同时 ,若以 (B -V )色指数进行度量 ,蓝离散星对简单恒星星族积分颜色的影响可达到 30 %。工作中 ,我们选取了 2 6个年龄在1x10 1 0 ~ 6x10 1 0 年之间的疏散星团为样本进行统计研究。 相似文献
163.
G. Cimò 《中国天文和天体物理学报》2006,6(1):1-14
A very rapid polarization position angle swing of~180°(with a time scale of~6 hours)observed at 2cm in QSO 1150+812(z=1.25)was reported by Kochenov & Gabuzda.This very rare event is difficult to explain.We found a pos- sible interpretation in the framework of a source model consisting of three polarized components,in which two compact polarized components are nearly simultaneously occulted by an interstellar cloud,with consequent focusing-defocusing effects.A spe- cific plasma-lens model is proposed which can reasonably fit the polarized flux density curve with results derived for the two lensed components.Some physical parameters of the plasma-lens and the source components are estimated.The two compact po- larized components are estimated to have brightness temperatures of~6×10~(12)K. Thus a bulk relativistic motion with a Lorentz factor less than 10 is required to meet the inverse-Compton limit. 相似文献
164.
Hua-Wei Zhang Gang Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Astronomy School of Physics Peking University Beijing Chinese Academy of Sciences-Peking University Joint Beijing Astrophysical Center Beijing 《中国天文和天体物理学报》2003,3(5):453-457
High-resolution, high signal-to-noise ratio spectra have been obtained for 32 metal-poor stars. The equivalent widths of Li A6708 A were measured and the lithium abundances were derived. The average lithium abundance of 21 stars on the lithium plateau is 2.33±0.02 dex. The Lithium plateau exhibits a marginal trend along metallicity, dA(Li)/d[Fe/H] ?0.12±0.06, and no clear trend with the effective temperature. The trend indicates that the abundance of lithium plateau may not be primordial and that a part of the lithium was produced in Galactic Chemical Evolution (GCE). 相似文献
165.
Gang Zhao Yu-Qin Chen Jian-RongShi Yan-Chun Liang Jin-Liang Hou Li Chen Hua-Wei Zhang Ai-Gen Li National Astronomical Observatories Chinese Academy of Sciences Beijing Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai Department of Astronomy School of Physics Peking University Beijing Department of Physics Astronomy University of Missouri Columbia MO USA 《中国天文和天体物理学报》2006,6(3):265-280
A project of a spectroscopic survey of Galactic structure and evolution with a Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) is presented. The spectroscopic survey consists of two observational modes for various targets in our Galaxy. One is a major survey of the Milky Way aimed at a systematic study of the stellar abundance and Galactic chemical evolution through low resolution (R=1000-2000) spectroscopy. Another is a follow-up observation with medium resolution (R = 10000) spectrographs aimed at detailed studies of the selected stars with different chemical composition, kinematics and dynamics. 相似文献
166.
Hui-Quan Li Jian-Cheng Wang Li XueNational Astronomical Observatories Yunnan Observatory Chinese Academy of Sciences Kunming li_huqu@sohu.comUnited Laboratory for Optical Astronomy Chinese Academy of SciencesGraduate School of the Chinese Academy of Sciences 《中国天文和天体物理学报》2004,4(4):311-319
It has been commonly accepted that the bulk velocity of extragalactic jets varies in all directions. We examined the synchrotron radiation of a jet with velocity structure in the direction perpendicular to its axis and found that the spectral energy distribution (SED) is not strongly influenced by this circumstance, that there is only a small increase in the emission intensity and almost no shift in the peak frequency. For objects with smaller inclined angles θ0 between the jet axis and the line of our sight, such as Blazars, the effect is more important. When θ0 exceeds a critical value there is no longer any change in the SED. To compare the bulk speed with different velocity structure, an equivalent speed (β) is defined which would reproduce the same spectral profile. There possibly exists a stress fμ(y) between layers of the outflow when the velocity is not the same in the jet. 相似文献
167.
Zhong-Li Zhang Hai-Guang Xu National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Physics Shanghai Jiao Tong University Shanghai 《中国天文和天体物理学报》2004,4(3):221-230
With the Chandra pointing observation of about 50 ks, we have detected41 point sources in the X-ray relatively faint elliptical galaxy NGC 1407, most ofwhich appear to be low mass X-ray binaries. In luminosity flux units, these resolvedpoint sources contribute about 17.8% of the total emission of the galaxy in 0.3-10 keV. Of the remaining diffuse emission, about 53.4% (or 43.9% of total) may arisefrom unresolved point sources. We find six ultraluminous X-ray sources with lumi-nosities above 10~(39) erg s~(-1). This number is less than has been found in NGC 720,but more than in NGC 4697 and NGC 1553, so suggesting a possible correlationbetween the number of ULXs and the total X-ray luminosity of early-type galaxies.A central point-like source is detected whose luminosity (2.36±0.14×10~(39)erg s~(-1))is the highest among all resolved sources. However, because of its relatively lowhardness ratio, we speculate that it is not likely to be a low luminosity AGN. 相似文献
168.
169.
我们银河系的直径大约是1O~12万光年,对我们来说,这样的尺度已经大得很难想象了。与银河系比起来,星系团的大小简直就是超乎想象。星系团通常包含成百上千个星系,它们在引力的作用下聚集在一起,其尺寸足有几千万光年。这些星系团是正在碰撞的星系和暗物质之间复杂的相互作用形成的,暗物质不参与电磁相互作用,既不发光也不反射光,所以我们无法直接探测到它们的存在。探测极其遥远星系团的质量分布就更是难上加难了。 相似文献