Measurements of the Position of X-Ray Sources with Copernicus

Open Access
Publisher Website
Google Scholar
Abstract
Positional observations of nine galactic X-ray sources made with the Copernicus satellite are presented. For five of these, improved positions are given with accuracies of about ±0.5 arcmin and a model spectrum is fitted to the data. It seems likely that two sources (3U 1728 – 16 and 1758 – 20) show variation in the low energy cut-off. The positions of four candidate stars proposed by Gursky were also examined. Our results exclude three of them as identifications while only a weak signal was received from the fourth and its identification is still unconfirmed. The number of chance associations of bright stars with X-ray positions is evidently greater than the 2.8 estimated by Gursky.