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The Orbital Period of HDE226868/Cyg X-1

J. LaSala·P. A. Charles·R. A. D. Smith·M. Balucinska-Church·M. J. Church
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Abstract

We present epoch 1996, high-quality radial velocity data for HDE 226868, the optical counterpart of Cygnus X-1. Combining our results with all published historical data, we have derived a new ephemeris for the system of HJD2450235.29 + n x 5.5998, which allows accurate orbital phase calculations to be made for any X-ray observations over the last 30 years. We find no evidence for any period change as has been suggested by Ninkov, Walker & Yang (1987). We discuss the shortcomings of previous work in establishing the period and orbital elements.

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J. LaSala, P. A. Charles, R. A. D. Smith, M. Balucinska-Church, M. J. Church. 1998-12-04. The Orbital Period of HDE226868/Cyg X-1. https://doi.org/10.1046/j.1365-8711.1998.02064.x

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