Browsing by Author "Johnson, Wiley Neil, 1945-"

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    Low-energy gamma radiation from Cen. X-4
    (1972) Johnson, Wiley Neil, 1945-; Haymes, Robert C.
    In July of 1969 a new X-ray source was detected in the southern sky near the constellation Centaurus. This source, identified as Centaurus X-4, displayed a variable intensity in the energy range 3 to 12 keV which at its maximum was more than twice as great as that from Sco X-l, the brightest discrete extrasolar X-ray source in the sky. A balloon-borne gamma-ray detector was launched from Parana, Argentina, on November 26, 1969, in an effort to measure the high-energy spectrum from this transient X-ray source. Due to partial failure of the instrument midway through the flight, the full sensitivity of the actively collimated Nal(Tl) detector was not achieved. This complication, coupled with the apparent time variation of the source, allowed only upper limits to be placed on the high-energy flux from this object in the range 80 keV to 2 MeV. As a result of this flight, the first high-altitude balloon research from Argentina, comparisons of Cen X-4 with other nova-like X-ray sources may be made. In addition, useful information on the response of actively collimated scintillation detectors to gamma radiation under varied conditions may he determined. The atmospheric gamma-ray background over Argentina, as well as the facilities avail able in Parana, proved to be ideal for southern hemisphere balloon research. In 1970 and 1971 two more successful expeditions to Argentina were made which produced valuable new data on various southern hemisphere celestial X-ray objects.