Single X-ray Source Research Articles

A new stereoscopic X-ray imaging technique using a single X-ray source: theoretical analysis

A binocular stereoscopic X-ray imaging technique is presented which can be used for both visual inspection by human observers and also for the extraction of three-dimensional coordinate information. The concept of implementing a stereoscopic X-ray imaging system to solve the problem of image interpretation is not new in itself. However, what is innovative in this research is the stereoscopic imaging technique developed. This is based on a rigorous design theory specifically developed for a single X-ray source and a pair of linear X-ray detector arrays.

Hard X-ray imaging evidence of nonthermal and thermal burst components

We analyze hard X-ray imaging observations of three flares, showing widely different characteristics, in order to try and discriminate the relative efficiency of heating and acceleration in the primary energy release. Using a simplified approach, we compute the hard X-ray distribution and energy deposition due to accelerated electrons, with beam and ambient plasma parameters appropriate for each of the observed events. The results are convolved with the Hard X-Ray Imaging Spectrometer (HXIS) instrumental response and compared with observations. We find that: (a) Many observations are compatible with thick target processes, and with the possibility that flares may have high (>20%) acceleration efficiency. (b) Single hard X-ray sources should be very common in the data available at present (HXIS and HINOTORI), as it is the case, as well as a transition from chromospheric footpoints to single source structures. The latter cannot then be directly interpreted as thermal sources. (c) In the particular case of a limb flare, associated with a rather weak high energy burst, we show that the spatial and spectral behavior of the hard X-ray emission is incompatible with pure nonthermal processes. We thus propose that the observed emission was principally due to the strong heating intrinsic to a reconnection process within the region of interaction between two magnetic structures which are seen in the soft X-ray data. (d) We also study the heating effect of a beam, due to Coulomb losses, during its passage through the flare loops. In some cases, rather large and localized temperature increases can be expected to appear within short timescales (≈ 1 s), leading to a combination of nonthermal plus thermal output in the hard X-ray spectrum, which renders virtually impossible the determination of the underlying beam parameters. We finally discuss the extent to which our conclusions are valid, considering the instrumental limitations as well as the simple physical treatment that we apply.

X-ray observations of the Antennae /NGC 4038/39/

view Abstract Citations (29) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-ray observations of the Antennae (NGC 4038/4039) Fabbiano, G. ; Trinchieri, G. Abstract The merging galaxies NGC 4038/39 were observed with the imaging proportional counter onboard the Einstein Observatory on two separate occasions, 12 months apart. The X-ray map seems to follow the optical contour of the two 'heads', although a softer X-ray component with a different spatial distribution might be present. The harder component is interpreted as being due to the integrated emission of single X-ray sources (like SNRs and X-ray binaries) in the two interacting galaxies. A harder point-like source might also be present in the contact region. The softer component could be thermal emission of gas heated by the interaction between NGC 4038 and NGC 4039. Moreover, a significant difference was observed between the two exposures. An additional X-ray source is present in the first image, but not in the second. If this source is associated with the Antennae, it could be either a very bright X-ray transient or a recent, optically undetected supernova. Publication: The Astrophysical Journal Pub Date: March 1983 DOI: 10.1086/183968 Bibcode: 1983ApJ...266L...5F Keywords: Galactic Radiation; Interacting Galaxies; X Ray Sources; Heao 2; Spatial Distribution; X Ray Binaries; Astronomy full text sources ADS | data products NED (4) SIMBAD (3)

Fast Image Reconstruction Based on a Radon Inversion Formula Appropriate for Rapidly Collected Data

An arrangement of a single x-ray source and a circular array (centered at the source) of detectors allows rapid collection of a number of x-ray projections of a cross section of an object. A class of appropriately fast algorithms for reconstructing the internal structure of the cross section from such data is rigorously derived starting from the classical Radon inversion formula. A new Radon inversion formula for divergent beams is given as a singlular integral. It is shown that this singular integral can be regularized a number of ways, each one of which leads to an efficient numerical evaluation. The structure, and hence the speed, of the resulting algorithms is similar to the so-called “convolution reconstruction techniques” which have been previously derived for data slowly collected along parallel rays and have been found both fast and accurate. It is demonstrated that, provided the same number of x-ray photons is used, the method of this paper gives as accurate reconstructions for diverging x-rays a...

Reconstruction of objects from diverging x rays

Rotation of a system consisting of a single x-ray source and a linear detector array allows rapid collection of x-ray projection data from which transaxial cross sections can be reconstructed. In this paper, we present an algorithm which makes possible rapid computerized reconstruction from such data. We describe some experiments aimed at investigating the optimal choice of some of the parameters associated with the algorithm. We report on reconstructions using our algorithm of the intact thorax of a dog and also of cross sections of the human female breast from x-ray data obtained by a computerized mammography machine.

Theory of Optimum Drilled Scintillation Collimators for X-Ray Astronomy

In order to study unambiguously the X-ray spectra from single celestial X-ray sources located amid several closely spaced sources, some form of angular collimation must be used on an X-ray telescope flown at balloon altitudes or higher. A popular design featuring high background rejection consists of closely spaced holes drilled through a block of scintillator material. The present paper explores several general cross-sectional geometries for these holes, presenting features in mathematical and graphical form such as transmission efficiency; angular resolution; residual detector area after collimation; and optimum spacing between detector and collimator. The influence of the hole shape on collimator "leakage" and on signal to background ratio is discussed. Collimator geometries to fulfill specific needs are deduced from the curves. A symmetric "hourglass" hole shape is shown to provide most nearly an optimum compromise of desirable features.