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Published online by Cambridge University Press: 04 August 2017
The currently known characteristics of the unique x-ray pulsar 1E2259+586 are briefly reviewed. The results from a recently completed analysis of the x-ray photon arrival times recorded by the Einstein Observatory are presented. The pulsar light curve has changed shape between two epochs separated by six months. The true pulse period is 6.978632 sec, double the previously reported value. In addition, there is evidence for orbital motion with a period close to 2300 sec. Some implications of this orbit are briefly discussed.