Solar X-ray Monitor (XSM) on-board Chandrayaan-2 orbiter

The remote X-ray fluorescence spectroscopy is a powerful technique to investigate the elemental abundances in the atmosphere-less planetary bodies. The experiment involves measuring spectra of fluorescent X-rays from lunar surface using a low energy X-ray detector onboard an orbiting satellite. Since the flux of fluorescent X-ray lines critically depend on the flux and spectrum of the incident solar X-rays, it is essential to have simultaneous and accurate measurement of X-ray from both Moon and Sun. In the context of Moon, this technique has been employed since early days of space exploration to determine elemental composition of lunar surface. However, so far it has not been possible to exploit it to its full potential due to various reasons. Therefore it is planned to continue the remote X-ray fluorescence spectroscopy experiment on-board Chandrayaan-2 which includes both lunar X-ray observations and solar X-ray observations as two separate payloads. The lunar X-ray observations will be carried out by Chandra Large Area Soft x-ray Spectrometer (CLASS) experiment; whereas the solar X-ray observations will be carried out by a separate payload, Solar X-ray Monitor (XSM). Here we present the overall design of the XSM instrument, the present development status as well as preliminary results of the laboratory model testing. XSM instrument will have two packages namely – XSM sensor package and XSM electronics package. XSM will accurately measure spectrum of Solar X-rays in the energy range of 1–15 keV with energy resolution ∼200 eV @ 5.9 keV. This will be achieved by using state-of-the-art Silicon Drift Detector (SDD), which has a unique capability of maintaining high energy resolution at very high incident count rate expected from Solar X-rays. XSM onboard Chandrayaan-2 will be the first experiment to use such detector for Solar X-ray monitoring.     

脉冲星导航中最优脉冲星组合选取方法

分析了X射线脉冲星导航原理,发现脉冲星的位置和脉冲到达时间(Time of Arrival,TOA)的测量误差直接影响导航精度.为优选导航脉冲星组合,在误差协方差分析的基础上,提出了一种导航脉冲星组合优选方法.该方法分别定义了优选指标位置精度因子(Positioning Dilution of Precision,PDOP)和脉冲星优选指标(Pulsars Select Criteria,PSC),不仅考虑了脉冲星空间位置分布,还考虑了测量噪声差异对导航误差的影响.最后以25颗信号品质较好的脉冲星为例,仿真验证了所提方法的有效性.     

不同工件超光滑表面残余应力的测试研究

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。     

Variability and origin of permanent radio emission in RS CVn and Algol type binaries

The variability of the radio emission of RS CVn and Algol type binaries has been observed over 70 hours by Lefèvre et al. (1993). In this contribution simple model calculations are applied to discuss the relevant time scales. It is concluded that a significant fraction of the permanent radio emission of these systems is due to flare-like processes of energy release over a wide range of energies.     

HXMT satellite for space hard X-ray observation

In this paper, the Hard X-ray Modulation Telescope mission is introduced. Its primary objective is to perform the hard X-ray all sky survey of high resolution and high sensitivity. The expected angular resolution and position accuracy of the satellite are better than 10^′ and 2^′, respectively. The preliminary mission design is analyzed. And a new attitude subsystem scheme is presented to meet the high precision demand of attitude determination. A conclusion is drawn that the mission design is feasible. The possible launch of it will significantly advance the astrophysical study.     

Particle acceleration and kinematics in solar flares – A Synthesis of Recent Observations and Theoretical Concepts (Invited Review)

We review the physical processes of particle acceleration, injection, propagation, trapping, and energy loss in solar flare conditions. An understanding of these basic physical processes is inexorable to interpret the detailed timing and spectral evolution of the radiative signatures caused by nonthermal particles in hard X-rays, gamma-rays, and radio wavelengths. In contrast to other more theoretically oriented reviews on particle acceleration processes, we aim here to capitalize on the numerous observations from recent spacecraft missions, such as from the Compton Gamma Ray Observatory (CGRO), the Yohkoh Hard X-Ray Telescope (HXT) and Soft X-Ray Telescope (SXT), and the Transition Region and Coronal Explorer (TRACE). High-precision energy-dependent time delay measurements from CGRO and spatial imaging with Yohkoh and TRACE provide invaluable observational constraints on the topology of the acceleration region, the reconstruction of magnetic reconnection processes, the resulting electromagnetic fields, and the kinematics of energized (nonthermal) particles. This revised version was published online in June 2006 with corrections to the Cover Date.     

The massive star distribution in the Galaxy and the Magellanic Clouds

The numbers and distribution of Population I O-type stars and Wolf-Rayet stars are reviewed. The numbers of known WR stars in the Galaxy, the LMC and the SMC are 185, 114, and 9, respectively. Distances and galactic distributions determined by various authors are compared. The single star and binary distributions are discussed in the light of evolutionary studies.     

A magnetic explanation for the rapid burster

The observations of X-ray Type II bursts from the low-mass X-ray binary MXB 1730-335 can be explained by a particular form of magnetic gating in the presence of steady external accretion. The requirements are a strong magnetic field of the neutron star (7×10¹¹–2×10¹² gauss at the surface), rotational symmetry and alignment of the field axis with the axis of a steadily accreting disk to within 6°.     

X射线耀斑的强度指标

本文利用GOES-7卫星的1分钟记录资料研究了1991年3月和6月期间6个大X耀斑伴随的软X射线爆发特性和源强度的关系。结果指出：对X射线耀斑，其射线辐射流量上升快的在日冕中激起的激波速度也较快．数值模拟研究指出，这可能反映爆发能量释放速率是源强度的主要指标．     

中子及中子散射特征

中子以它特有的性质,使它成为继X射线和电子衍射之后的又一研究微观物质结构的有效方法。由于中子散射技术的发展,人们才得以在声子色散曲线和同位素效应的研究等方面有所收获。中子散射可以说是对X射线衍射和电子衍射的一个重要的和不可缺少的补充。中子散射技术利用中子不带电、穿透力极强、能直接鉴别核素、较之X射线对轻元素灵敏、具有磁矩和波粒二象性等特点,使之成为一种独特的,从原子和分子尺度上研究各种物质结构和微观世界运动规律的高新技术。