Cosmic x-ray surveys.

Chapters 1 to 3 are devoted solely to review of the X-ray sky, the environmental limitations on an experiment, and the techniques of X-ray detection. These are necessary for the design of proportional counters for a series of rocket surveys of the X-ray sky. Particular attention is given to the reduction of background noise, and significant improvements in the performance of laboratory tested detectors is achieved and discussed in Chapter 4. Chapter 4. also describes a wide range of calibration techniques developed and used on the rocket payloads. Because of the desirability of recording design detail, it is included in Chapters 1-4, contained in Volume 1. The first volume is used freely as a source of reference in Volume 2, the analysis section of the thesis. Results from three early rocket flights were available for analysis. Preliminary results, published at the time of these flights are included in Chapter 5. These are (i) the discovery of an intense X-ray source in Centaurus on 4. April 1967 (flight i) (2) a measure of the decrease in intensity and steepening of X-ray spectrum of the source, Cen XR-2, by 20 April 1967 (flight II) and complete disappearance by I December 1967 (flight III). (The variability made Cen XR-2 unique among X-ray sources at the time.) (3) a possible source in Cetus, significant in view of its large separation from the galactic disc (flight ii, III). In Chapter 6, flight II data has been reanalysed in detail and in the light of more recent evidence. Two significant findings are (i) An accurate and unambiguous location of Cen XR-2 in galactic longitude. The new position excludes a number of objects (hard X-ray, optical, radio), whose properties have been employed in constructing models for the source. (2) An established variability of X-ray sources in the Cygnus and nearby regions. The properties of the variation in Cen XR-2 and a similar newly discovered variable allow some restrictions to be placed on source models. With future low noise surveys in mind, the possibility of galactic structure in the diffuse X-ray background is investigated in Chapter 7. Remarkable similarities in the spectra of low frequency radio, X-ray and extraterrestrial electron spectra are displayed, and can be interpreted in terms of galactic phenomena with some reservations.. The radio data are used to predict possible X-ray anisotropies. Finally, in Chapter 8 attention is given to the possibility of ground based surveys of X-ray stars. Extensive new information on the electron production rates in the ionospheric fl-region are compiled and it is shown that the reported detection of a cosmic X-ray effect has implications on the chemistry of the ionosphere.