X-ray Observations of Supernova Remnants by Copernicus

Abstract

The observations reported below were obtained using two focussing X-ray systems carried on board OAO-C (Copernicus). Each system comprises a grazing incidence paraboloidal reflector to focus soft X-radiation onto a miniature proportional counter detector. The circular field of view of each telescope is approximately 10′ in diameter, but may be reduced by the use of smaller apertures mounted on a remotely controlled wheel in front of the detectors. After including the efficiencies in the reflecting optics and in the detector response, the geometrical aperture of 12 cm² is reduced to an effective aperture of approximately 1 cm² for each telescope. One system responds to photons in the energy range 0.7–1.5 keV, the other to 1.5–4.2 keV photons. A third non reflecting system (not subsequently referred to) is collimated to 2 deg by 5 deg FWHM and responds to 4–12 keV photons. The X-ray telescopes are aligned to the spacecraft axis to an accuracy of about l′, and spacecraft drift errors are smaller than this over periods of several hours. Thus exposures of 20000 cm² s are possible on accurately selected regions of sky. The equipment was built at Mullard Space Science Laboratory.