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[en] Recently there have been much interest in the development of pulsed x-ray sources for various applications such as in microlithography, microscopy and flash radiography. This paper reports the development of several models of laboratory pulsed x-ray sources at the University of Malaya including the UMFX flash x-ray tube, the UMVS vacuum spark and the ICTP-UM plasma focus. Results on the characterisation of these x-ray sources will be reported, followed by discussions on their possible applications in radiography, lithography and microscopy
[en] Ultra-luminous X-ray sources (ULX) are X-ray binaries with Lx >1039 erg s–1. The most spectacular examples of ULX occur in starburst galaxies and are now understood to be young, luminous high mass X-ray binaries. The conditions under which ULX form are poorly understood, but recent evidence suggests they may be more common in low metallicity systems. Here we investigate the hypothesis that ULX form preferentially in low metallicity galaxies by searching for ULX in a sample of extremely metal poor galaxies (XMPG) observed with the Chandra X-Ray Observatory. XMPG are defined as galaxies with log(O/H) + 12 < 7.65, or less than 5% solar. These are the most metal-deficient galaxies known, and a logical place to find ULX if they favor metal poor systems. We compare the number of ULX (corrected for background contamination) per unit of star formation (NULX(SFR)) in the XMPG sample with NULX(SFR) in a comparison sample of galaxies with higher metallicities taken from the Spitzer Infrared Galaxy Sample. We find that ULX occur preferentially in the metal poor sample with a formal statistical significance of 2.3σ. We do not see strong evidence for a trend in the formation of ULX in the high metallicity sample: above 12+log(O/H) ∼ 8.0 the efficiency of ULX production appears to be flat. The effect we see is strongest in the lowest metallicity bin. We discuss briefly the implications of these results for the formation of black holes in low metallicity gas.
[en] We discuss the extent of the hot interstellar phase (approximately 106K) in the direction of the cloud revealed by Strong and Lebrun (1981). The distance (80pc) of the cloud is estimated from measured variation of reddening versus distance in its direction. No X ray absorption by the cloud was observed. This indicates that the hot plasma has an extent less than 80pc, the cloud distance. The value 80pc well agrees with the radius of a SNR supposed to be associated with the hot plasma
[en] The first release of the Chandra Source Catalog (CSC) contains ∼95,000 X-ray sources in a total area of 0.75% of the entire sky, using data from ∼3900 separate ACIS observations of a multitude of different types of X-ray sources. In order to maximize the scientific benefit of such a large, heterogeneous data set, careful characterization of the statistical properties of the catalog, i.e., completeness, sensitivity, false source rate, and accuracy of source properties, is required. Characterization efforts of other large Chandra catalogs, such as the ChaMP Point Source Catalog or the 2 Mega-second Deep Field Surveys, while informative, cannot serve this purpose, since the CSC analysis procedures are significantly different and the range of allowable data is much less restrictive. We describe here the characterization process for the CSC. This process includes both a comparison of real CSC results with those of other, deeper Chandra catalogs of the same targets and extensive simulations of blank-sky and point-source populations.
[en] An x-ray calibration facility for use in the 0.2--25 keV region is described. The facility employs several types of specially modified sources and detectors to produce and detect both line and continuum radiation in this energy range. We describe an inexpensive commercial x-ray source which has been modified for efficient high intensity operation as well as production of x-rays up to 25 keV. We also describe a system that utilizes multilayer mirrors alone or in a double Bragg geometry to select an energy bandpass. This system is controlled by a microcomputer which translates and rotates the multilayers to provide an easily selectable monochromatic beam with good resolution over a broad energy range. A long focal length Kirkpatrick--Baez mirror pair has been coupled to a pivoting beam line in order to accurately characterize gratings for use in soft x-ray astronomy. The beam line is scanned through the various grating orders. All aspects of the facility incorporate high degree of flexibility so that a wide variety of calibrations can be easily performed. 12 refs., 5 figs
[en] Objectives were to conduct observations with the first satellite entirely devoted to x-ray astronomy and to analyze the results obtained. A catalog of x-ray sources was generated, and results of discoveries and further detailed observations of sources were presented in scientific journals and meetings. A list of how objectives were met, a brief description of the instrument, significant results, the x-ray catalog, and a complete bibliography of results are included