Showing papers by "David N. Burrows published in 1991"
TL;DR: In this paper, two different methods, classical and Bayesian, for determining confidence intervals involving Poisson-distributed data are compared and reasons for preferring the Bayesian over the classical method are given.
Abstract: Two different methods, classical and Bayesian, for determining confidence intervals involving Poisson-distributed data are compared. Particular consideration is given to cases where the number of counts observed is small and is comparable to the mean number of background counts. Reasons for preferring the Bayesian over the classical method are given. Tables of confidence limits calculated by the Bayesian method are provided for quick reference.
499 citations
TL;DR: In this article, the authors used the Roentgen Astronomy Satellite (ROSAT) to detect shadowing of the X-ray background in the ¼ keV band (presumed to be of galactic origin) by the unusual interstellar cloud in Draco.
Abstract: THE astronomical soft X-ray background has both extragalactic and, at lower energies, galactic components. Using the Roentgen Astronomy Satellite (ROSAT), we have detected shadowing of the X-ray background in the ¼ keV band (presumed to be of galactic origin) by the unusual interstellar cloud in Draco. The Draco cloud is at high galactic latitude and, at several hundred parsecs distance from the Sun, is well away from the galactic plane. It reduces the ¼ keV emission by 63% relative to the adjacent sky, implying that a substantial contribution to the X-ray background in this direction comes from hot gas beyond the cloud. This is the first direct evidence for a million-degree galactic halo of gas, but the significance of this observation for understanding the global diffuse X-ray background is unclear, as it contradicts earlier studies1–3 which failed to find shadowing by galactic gas. More observations of this sort, covering objects distributed throughout the galaxy, are needed to explore the morphology of the hot and cold gas in the nearby interstellar medium.
121 citations
TL;DR: In this paper, the application of CCDs to X-ray imaging and spectroscopy for astronomy is described and the requirements which differ markedly from those of traditional optical applications are highlighted.
Abstract: The application of CCDs to X-ray imaging and spectroscopy for astronomy is described. The requirements which differ markedly from those of traditional optical applications are highlighted. Results of recent research programs to optimize CCD X-ray response are presented. It is shown that very high quantum efficiencies and Fano noise limited energy resolutions can be obtained. A number of issues related to the practical implementation of future instruments are reviewed.
47 citations