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81.
给出了1992-1995年Be/X射线双星LSI+61°303每年的光谱观测结果,分析了光谱发射线轮廓及其变化,观测显示Hβ发射线轮廓具有典型的气壳吸收,表明观测视线与Be星赤道平面平行,同时发现Hα发射线参数发等值宽度和双峰强度之比也具有类似射电流量的周期性变化,但其变化与射电玫光学光度的变化不同,因此认为此变化可能与中子星周期的吸积盘及其轨道交食有关。 相似文献
82.
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84.
通过对玻璃、陶瓷、金属3个试件进行超精密加工,使试件表面粗糙度达到纳米级,采用非破坏性的X射线衍射sin2ψ法测量原理对不同试件的残余应力进行了测试研究。结果表明:在本试验条件下,3个试件都只存在残余压应力,并且陶瓷的残余压应力最大,金属残余压应力最小。 相似文献
85.
惠雪梅%王晓洁%尤丽虹%王益%全小平 《宇航材料工艺》2006,36(Z1):48-51
通过地面环境模拟实验,分析了高模碳纤维/环氧树脂改性氰酸酯复合材料(M40J/CE/EP)的表面元素,研究了高真空加热环境下复合材料的真空出气性能和出气气体成分.结果表明,M40J/CE/EP复合材料的表面主要由C、O、N元素构成;经高真空加热后,复合材料的出气气体成分以小分子挥发物和碳氢化合物电离碎片为主,有可能在空间低温条件下冷凝在航天器的敏感器件表面而造成污染;通过真空出气性能实验测得,M40J/CE/EP复合材料的总质量损失(TML)的平均值为0.27%,收集到的可凝挥发物(CVCM)为0,完全达到出气筛选合格的指标要求. 相似文献
86.
G. Trottet 《Space Science Reviews》1994,68(1-4):149-158
Non-thermal hard X-ray, gamma-ray and radio emission are the most direct signatures of the presence of energetic particles in the solar atmosphere. This paper lays emphasis on hard X-ray and radio imaging data, obtained during and outside flares, which reveal the sites where particles interact with the ambient medium. These observations, which provide more or less direct information on the topology and dynamics of the magnetic structures in which particles are accelerated and propagate, are discussed in the framework of the statistical flare scenario. 相似文献
87.
G. Setti G. Zamorani 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
We review the present knowledge on the cosmological evolution of quasars, by discussing some of the recent results obtained from studies of optically selected objects. Despite the fast development of prism survey tecniques, the color selection still appears to be the best tecnique for constructing the complete samples which are necessary for statistical studies. It is shown, however, that even the best available complete samples of quasars selected on the basis of ultraviolet excess (z < 2.2) are not sufficient to univocally determine the “correct” evolutionary model. Moreover, some preliminary results suggest that the evolution law derived from quasars with mB<20 and z<2.2 can not be extrapolated to fainter magnitudes and higher redshifts. On the basis of what is known today about the optical and X-ray properties of quasars, we then discuss some of teh possible results, relevant to cosmology, which can be achieved with future coordinated optical and X-ray observations of quasars. 相似文献
88.
F.E. Bauer C. Vignali D.M. Alexander W.N. Brandt G.P. Garmire A.E. Hornschemeier P.S. Broos L.K. Townsley D.P. Schneider 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2555-2560
We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 active galactic nuclei (AGN) detected in the 2 Ms Chandra Deep Field-North Survey with >200 background-subtracted 0.5–8.0 keV counts [F0.5–8.0 keV = (1.4−200) × 10−15 erg cm−2 s−1]. Our preliminary spectral analyses yield median spectral parameters of Γ = 1.61 and intrinsic NH = 6.2 × 1021 cm−2 (z = 1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived JVH distribution and, to a lesser extent, the X-ray luminosity distribution. We also find that among the 136 AGN, 10 (≈7%) show significant Fe K emission-line features with equivalent widths in the range 0.1–1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Γ < 1.0 and large Fe K equivalent width). Finally, we find that 81 (≈60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (≈80–90%) when better photon statistics are available. 相似文献
89.
William V. Boynton Ann L. Sprague Sean C. Solomon Richard D. Starr Larry G. Evans William C. Feldman Jacob I. Trombka Edgar A. Rhodes 《Space Science Reviews》2007,131(1-4):85-104
The instrument suite on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is well suited
to address several of Mercury’s outstanding geochemical problems. A combination of data from the Gamma-Ray and Neutron Spectrometer
(GRNS) and X-Ray Spectrometer (XRS) instruments will yield the surface abundances of both volatile (K) and refractory (Al,
Ca, and Th) elements, which will test the three competing hypotheses for the origin of Mercury’s high bulk metal fraction:
aerodynamic drag in the early solar nebula, preferential vaporization of silicates, or giant impact. These same elements,
with the addition of Mg, Si, and Fe, will put significant constraints on geochemical processes that have formed the crust
and produced any later volcanism. The Neutron Spectrometer sensor on the GRNS instrument will yield estimates of the amount
of H in surface materials and may ascertain if the permanently shadowed polar craters have a significant excess of H due to
water ice. A comparison of the FeO content of olivine and pyroxene determined by the Mercury Atmospheric and Surface Composition
Spectrometer (MASCS) instrument with the total Fe determined through both GRNS and XRS will permit an estimate of the amount
of Fe present in other forms, including metal and sulfides. 相似文献
90.
质子事件的爆发与太阳软X射线辐射有着很强的相关性,利用GOES卫星的1~8 (A)波段和0.5~4 (A)波段的软X射线数据,选取一些特征参量验证该相关性并应用到质子事件短期预报中.在当前质子事件传输物理机制不完全明确的情况下,在现有的预报质子事件有无的模型基础上,利用BP神经网络,根据软X射线通量水平等预测事件质子峰值通量水平,再对训练后的网络进行检验,检验预测所得结果与实际探测值误差小于一个量级,具备一定实用意义. 相似文献