Open AccessThe orbital period of HDE 226868/Cyg X‐1
Author(s) -
LaSala J.,
Charles P. A.,
Smith R. A. D.,
BałucińskaChurch M.,
Church M. J.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.02064.x
Subject(s) - physics , ephemeris , orbital period , epoch (astronomy) , astrophysics , orbital elements , period (music) , astronomy , radial velocity , stars , satellite , acoustics
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 HJD 245 0235.29 + n × 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 such as that suggested by Ninkov, Walker &38; Yang. We discuss the shortcomings of previous work in establishing the period and orbital elements.