OSO-8 X-ray polarimeter and Bragg crystal spectrometer observations

Polarimetric observations of Cygnus X-1 and Cygnus X-2 at 2.6 keV were performed with the focusing mosaic graphite crystal X-ray polarimeter on the OSO-8 satellite. The polarisation of Cygnus X-2 is consistent with accretion disc models, no polarisation was detected in Cygnus X-1. Polarisation measurements of the Crab Nebula at 2.6 and 5.2 keV confirm that the X-ray emission occurs by the synchrotron process. The spectrum of the transient X-ray sources Ariel 0620-00 between 1.55 and 6.70 A was observed by the Bragg mosaic graphite crystal spectrometer. No spectral lines were observed, the continuum can be fitted with a thermal bremsstrahlung spectrum at a temperature of 15x106 K. (R.S.)