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Published online by Cambridge University Press: 14 August 2015
In developing models for the point X-ray sources the general aim has been to find a common explanation for all such objects. However, important observational differences have already become apparent among the systems having optical identifications. A close examination of the evidence shows that those with the most certain optical identifications, Scorpio X-1 and Cygnus X-2, have very few features in common and, in fact, the model proposed here for Cyg X-2 can probably be excluded for Sco X-1.