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排序方式: 共有310条查询结果,搜索用时 140 毫秒
191.
G.L. Huang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(8):1191-1194
Coronal magnetic field and nonthermal electrons are very important parameters for understanding of the global heliophysical processes. A flare on November 1, 2004 is selected for self-consistent calculations of coronal magnetic field parallel and perpendicular to the line-of-sight, and density of nonthermal electrons from Nobeyama observations. Both of the diagnosis methods and results are discussed in this paper. 相似文献
192.
An overview of the material developments currently being pursued by the European Space Agency (ESA) with respect to X-ray, γ-ray and neutron detection media is given. The benefits underlying the selection of specific materials are discussed. In the X-ray regime the basic microphysics behind degraded spectral performance caused by the polarization effect and Te inclusions, have been investigated. We have found that both effects degrade the spectra by producing a localised distortion of the electric field. The underlying cause for the distortion does however differ. For the γ-ray regime, a low-noise equivalent scintillator to LaBr3 has been developed in the form of CeBr3. Three inch crystals with a FWHM energy resolution of 4.4% at 662 keV have successfully been produced. For neutron detection, a boron compound based solid state neutron detector has been developed that is sensitive to neutrons, alpha particles and 60 keV X-rays. The measured detection efficiency in detection for thermal neutrons was found to be in the order of a few per cent. 相似文献
193.
L. Boirin M. Mndez M. Díaz Trigo A.N. Parmar J.S. Kaastra 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2759-2761
We report the XMM-Newton detection of narrow Fe xxv and Fe xxvi X-ray absorption lines at 7 keV in the persistent emission of the dipping low-mass X-ray binary (LMXB) 4U 1323−62. Such features have now been reported in a growing number of LMXBs seen almost edge-on, indicating that the highly-ionized plasma probably originates in an accretion disk atmosphere or wind. During dipping intervals of 4U 1323−62, the strength of the Fe xxv feature increases while that of the Fe xxvi feature decreases, consistent with the presence of less strongly ionized material in the line-of-sight. As observed previously, the changes in the X-ray spectrum during dips are inconsistent with a simple increase in absorption by cool material. However, we show that the changes in both the narrow absorption features and the continuum can be modeled self-consistently by variations in the properties of an ionized absorber. From persistent to deep dipping the photo-ionization parameter decreases while the equivalent hydrogen column density of the ionized absorber increases. No partial covering of any component of the spectrum, and hence no extended corona, are required. Since highly-ionized absorption features are seen from many other dip sources, this mechanism may also explain the overall changes in X-ray spectrum observed during dipping intervals from these systems. 相似文献
194.
Jean-Marie Hameury Jean-Pierre Lasota 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2857-2861
Outer radius variations play an important role in the disc structure and evolution. We consider theoretical and observational consequences of such variations in cataclysmic binaries and low-mass X-ray binaries. We find that the action of tidal torques must be important well inside the tidal radius. We also conclude that it is doubtful that the tidal–thermal instability is responsible for the superoutburst/superhump phenomena. 相似文献
195.
A. Dominic Fortes Ian G. Wood David P. Dobson Paul F. Fewster 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We describe the scientific case for and preliminary design of an instrument whose primary goal is to determine the chemistry (element abundance) and mineralogy (compound identity and abundance) of Titan’s surface using a combination of energy dispersive X-ray fluorescence spectroscopy (EDXRF) and X-ray diffraction (XRD). XRD is capable of identifying any crystalline substance present on Titan’s surface at relative abundances greater than ∼1 wt%, allowing unambiguous identification of, for example, structure I and II clathrates (even in the presence of ice), and various organic solids, which may include C2H2, C2H4, C4H2, HCN, CH3CN, HC3N, and C4N2). The XRF component of the instrument will obtain elemental abundances for 16 < Z < 60 with minimum detection limits better than 10 ppm (including detection of atmospheric noble gas isotopes), and may achieve detection limits of 0.01–1% for lighter elements down to Z = 6 (carbon). The instrument is well suited to integration with other analytical tools as part of a light-weight surface chemistry and mineralogy package. Although considerably less sensitive to elemental abundance than GC–MS (10−2 vs. 10−8) it is likely to be significantly lighter (<0.5 kg vs. 10 kg). 相似文献
196.
X射线脉冲星导航在行星际轨道上的应用 总被引:1,自引:0,他引:1
X射线脉冲星导航技术被认为是新一代导航技术,非常适合于行星际探测.深入分析了利用搜索空间方法求解飞行器真实位置和估计位置相位差的脉冲整周期模糊数,解决了相位导航方法存在的周期模糊数问题.利用轨道动力学模型估计飞行器的位置,并以真实位置和估计位置上的脉冲相位之差作为反馈进行偏差校正.仿真表明,X射线脉冲星导航方法在行星际轨道上是可行和高效的. 相似文献
197.
针对X射线脉冲星导航中,传统的扩展卡尔曼滤波(EKF)算法因为线性化需要从而忽略观测模型高阶项导致较大截断误差的问题,提出一种适用于脉冲星导航的改进线性观测方程。首先,详细分析了观测方程简化过程中会造成截断误差的周年视差效应及引力延迟效应的物理意义,介绍了2个高阶项的数学模型,并对2项进行了详细的数值分析。其次,利用泰勒展开等方式,将2个高阶项进行线性化处理,建立一种改进的线性观测方程。最后,利用地球卫星轨道数据,将2个线性观测方程分别应用到脉冲星导航的EKF解算中验证改进线性观测方程的有效性。结果表明,在考虑高阶项影响的条件下,改进的线性观测方程均能保证250 m和2 m/s以内的位置和速度估计误差而且对高阶项变化表现出一定的鲁棒性,但传统的简化线性观测方程却会导致发散。 相似文献
198.
199.
Richard E. Griffiths Takamitsu Miyaji Adam Knudson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2486-2491
The great sensitivities of the Chandra X-ray Observatory and XMM-Newton have allowed us to begin to explore the X-ray emission from galaxies at moderate to high redshift. By using the stacking method, we show that we can detect the ensemble emission from normal elliptical, spiral and irregular galaxies out to redshifts approaching unity. The average X-ray luminosity of these galaxy types can then be compared with the results of models of the evolution in the numbers of low-mass and high-mass X-ray binaries and can possibly be used to constrain models of star formation. 相似文献
200.
H. Inoue H. Kunieda 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2628-2631
Japanese future space programs for high energy astrophysics are presented. The Astro-E2 mission which is the recovery mission of the lost Astro-E has been approved and now scheduled to be put in orbit in early 2005. The design of the whole spacecraft remains the same as that of Astro-E, except for some improvements in the scientific instruments. In spite of the five years of delay, Astro-E2 is still powerful and timely X-ray mission, because of the high energy resolution spectroscopy (FWHM 6 eV in 0.3–10 keV) and high-sensitivity wide-band spectroscopy (0.3–600 keV). The NeXT (New X-ray Telescope) mission, which we propose to have around 2010, succeeds and extends the science which Astro-E2 will open. It will carry five or six sets of X-ray telescopes which utilize super-mirror technology to enable hard X-ray imaging up to 60–80 keV. In mid-2010s, we would participate in the European XEUS mission, which explores the early (z>5) “hot” universe. 相似文献