中国科学院机构知识库网格系统: 检索

浏览/检索结果: 共5条，第1-5条

帮助

条数/页：排序方式：
	An underlying clock in the extreme flip-flop state transitions of the black hole transient Swift J1658.2-4242 期刊论文 OAI收割 Astronomy and Astrophysics, 2020, 卷号: 641, 页码: A101 作者: HXMT \| 收藏 \| 浏览/下载：59/0 \| 提交时间：2022/02/08 accretion accretion disks black hole physics X-rays: binaries time Astrophysics - High Energy Astrophysical Phenomena Abstract: Aims: Flip-flops are top-hat-like X-ray flux variations, which have been observed in some transient accreting black hole binary systems, and feature simultaneous changes in the spectral hardness and the power density spectrum (PDS). They occur at a crucial time in the evolution of these systems, when the accretion disc emission starts to dominate over coronal emission. Flip-flops remain a poorly understood phenomenon, so we aim to thoroughly investigate them in a system featuring several such transitions. Methods: Within the multitude of observations of Swift J1658.2-4242 during its outburst in early 2018, we detected 15 flip-flops, enabling a detailed analysis of their individual properties and the differences between them. We present observations by XMM-Newton, NuSTAR, Astrosat, Swift, Insight-HXMT, INTEGRAL, and ATCA. We analysed their light curves, searched for periodicities, computed their PDSs, and fitted their X-ray spectra, to investigate the source behaviour during flip-flop transitions and how the interval featuring flip-flops differs from the rest of the outburst. Results: The flip-flops of Swift J1658.2-4242 are of an extreme variety, exhibiting flux differences of up to 77% within 100 s, which is much larger than what has been seen previously. We observed radical changes in the PDS simultaneous with the sharp flux variations, featuring transitions between the quasi-periodic oscillation types C and A, which have never been observed before. Changes in the PDS are delayed, but more rapid than changes in the light curve. Flip-flops occur in two intervals within the outburst, separated by about two weeks in which these phenomena were not seen. Transitions between the two flip-flop states occurred at random integer multiples of a fundamental period of 2.761 ks in the first interval and 2.61 ks in the second. Spectral analysis reveals the high and low flux flip-flop states to be very similar, but distinct from intervals lacking flip-flops. A change of the inner temperature of the accretion disc is responsible for most of the flux difference in the flip-flops. We also highlight the importance of correcting for the influence of the dust scattering halo on the X-ray spectra.
	Spectral Uncertainty of Terrestrial Objects and the Applicability of Spectral Angle Mapper Algorithm 期刊论文 OAI收割 SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 卷号: 35, 期号: 10, 页码: 5443-5452 作者: Cen Yi; Zhang Gen-zhong; Zhang Li-fu; Lu Xu-hui; Zhang Fei-zhou 收藏 \| 浏览/下载：26/0 \| 提交时间：2016/04/20 Spectral angle Uncertainty Spectral differences Hyperspectral
	Simulation and experiment of the static FTIR based on micro multi-step mirrors (EI CONFERENCE) 会议论文 OAI收割 International Symposium on Photoelectronic Detection and Imaging 2011: Sensor and Micromachined Optical Device Technologies, May 24, 2011 - May 26, 2011, Beijing, China 作者: Liang Z.-Z.; Zhang J.; Zhang J.; Zhang J.; Zhu W.-B. 收藏 \| 浏览/下载：30/0 \| 提交时间：2013/03/25 In recent years Fourier transform spectrometer (FTS) with small size and low mass is required in many applications with growing need for real-time and small platform spectral detection. In this paper a micro Fourier transform infrared spectrometer (FTIR) based on spatial modulation mode was designed. This spectrometer has the advantages of high stability and simplified configuration. It also promises optical path differences (OPD) with high precision as MOEMS technology is used in manufacturing the key components. The simulation and the experiments with regard to this FTIR configuration have been done. Firstly the diffraction effect of the micro multi-step mirrors (MMSMs) is studied. We discuss the influence to the reversed spectrum by different mirror widths and different diffraction distances. Secondly we simulate and analyze the influence of the source solid angle to the spectral resolution. Thirdly we set up the theoretical model of the collimation error which is mainly from the defocus of the optical system and analyze the result caused by the collimation error. Fourthly a new discrete Fourier transform arithmetic using least-squares cosines progression (LSCP) is proposed which can reconstruct the spectrum with nonuniform sampled signals. Finally the MMSMs are fabricated used the MOEMS technology and the structural parameters are tested. 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
	An index of vegetation water content invasion by Landsat 5, in semi-arid area: The Tarim River Basin 会议论文 OAI收割 2009 International Conference on Environmental Science and Information Application Technology, ESIAT, Wuhan, China, 2009 Chang; Cun1; Chen; Xi2; Bao; Anming2; Ma; Zhongguo1; Wang; Jinlin1 收藏 \| 浏览/下载：21/0 \| 提交时间：2011/08/23 Arid regions - Environmental engineering - Sensitivity analysis - Solvent extraction - Water analysis - Water content - Watersheds - Arid area - Equivalent water thickness - EWT - Global sensitivity analysis - Infrared indices - LANDSAT TM - Landsat-5 - NDII - NIR regions - Normalized differences - Operational methods - PROSPECT model - Regression equation - Semiarid area - Spectral indices - Tarim River basin - Vegetation water content - Water cycle
	Recent progress in computing weighting tables for calculating CIE tristimulus values 会议论文 OAI收割 20th Congress of the International-Commission-for-Optics, Changchun, China, August 21-26, 2005 作者: Li ZJ(李长军); Luo, MR; Wang G(王葛) 收藏 \| 浏览/下载：34/0 \| 提交时间：2012/06/06 tristimulus values spectral reflectance function weighting tables colour differences