High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.
X-ray spectroscopy is an important tool for understanding the extreme photoionization processes that drive the behaviour of non-thermal equilibrium plasmas in compact astrophysical objects such as black holes 1-4. Even so, the distance of these objects from the Earth and the inability to control or accurately ascertain the conditions that govern their behaviour makes it difficult to interpret the origin of the features in astronomical X-ray measurements. Here, we describe an experiment that uses the implosion 5 driven by a 3 TW, 4 kJ laser system 6 to produce a 0.5 keV blackbody radiator that mimics the conditions that exist in the neighbourhood of a black hole. The X-ray spectra emitted from photoionized silicon plasmas resemble those observed from the binary stars Cygnus X-3 (refs 7, 8) and Vela X-1 (refs 9-11) with the Chandra X-ray satellite. As well as demonstrating the ability to create extreme radiation fields in a laboratory plasma, our theoretical interpretation of these laboratory spectra contrasts starkly with the generally accepted explanation for the origin of similar features in astronomical observations. Our experimental approach offers a powerful means to test and validate the computer codes used in X-ray astronomy. X-ray spectroscopy with an X-ray satellite is the main observational method to give information about compact objects, especially black holes. Black holes are indirectly studied by observing the X-ray continuum from a heated accretion disc and the X-ray fluorescence from the ambient gas of the stellar wind and the surface of a companion star in their binary systems. To derive physical properties from the observations, X-ray astronomers rely on non-local-thermodynamical-equilibrium (LTE) atomic physics in a cold ambient gas subject to an extreme radiation field, for which the mean radiation temperature is of the order of 1 keV. Theoretical models have been developed on the basis of the observed spectra 1-4 and complex computer codes were developed to analyse the observed X-ray spectra 12-16. The underlying assumption of these models is that the spectrum originates from a photoionized plasma. In other words, the intense radiation from the compact object photoionizes the gas, and generates a relatively low-electron-temperature highly ionized non-LTE plasma. However, laboratory experiments on non-LTE photoionized plasmas
The diagnostic capability of Fe xiii line features seen in the 170-210 Å waveband of the EUV Imaging Spectrometer (EIS) on Hinode is investigated, with emphasis on density diagnostics applied to solar active regions. Four diagnostic line pairs are found to yield consistent densities ranging from 10 8.5 to 10 9.5 cm −3 across an active region using a new theoretical model of the ion. In separate EIS observations of a small flare, the widely used line pair, Fe xiii λ203.8/λ202.0, is found to reach the high density limit predicted by a new theoretical model of the iron ion.
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