Abstract
ON October 25, 1968, we searched for X-rays from M–87 using a balloon-borne detector. The detector consisted of two xenon proportional counter arrays with a combined sensitive area of 2,000 cm2. The electronic systems of the two arrays were identical, and they operated completely independently. A five channel pulse height analyser in each system covered the energy range from 15 keV to 65 keV. Pulse shape discrimination circuits were used successfully to suppress the background radiation1. The collimation for both systems was 13° FWHM. The azimuth of the detector was stabilized by a servo-compensated torque motor, using the Earth's magnetic field as a reference. An on-board control device changed the azimuth and zenith angles according to a programme set before launch. Crossed magnetometers and a Sun sensor measured the azimuth, and a shaft encoder measured the zenith angle. The energy channel settings and stability of the instrument were checked twice each hour during the flight by exposing the detector to a 241Am radioactive source. The counting rate, housekeeping and orientation data were all photographically recorded on board.
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McCLINTOCK, J., LEWIN, W., SULLIVAN, R. et al. High Energy X-ray Study of M–87. Nature 223, 162–163 (1969). https://doi.org/10.1038/223162b0
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DOI: https://doi.org/10.1038/223162b0
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