The Orbital Period of HDE226868/Cyg X-1

2); Astronomy; J. LaSala(1; Maine; M. Balucinska-Church(3); M.J. Church(3) ((1)Department of Astrophysics; P.A. Charles(1); Physics Department; Portland; R.A.D. Smith(1)

arxiv: astro-ph/9812101 · v1 · submitted 1998-12-04 · 🌌 astro-ph

The Orbital Period of HDE226868/Cyg X-1

J. LaSala(1 , 2) , P.A. Charles(1) , R.A.D. Smith(1) , M. Balucinska-Church(3) , M.J. Church(3) ((1)Department of Astrophysics , University of Oxford , U.K.; (2) University of Southern Maine

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Physics Department Portland Maine U.S.A.; (3)School of Physics Astronomy University of Birmingham U.K.)

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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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The Orbital Period of HDE226868/Cyg X-1

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