The optical spectrum of HDE 226868 = Cygnus X-1. I - Radial velocities and orbital elements

Abstract

view Abstract Citations (99) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The optical spectrum of HDE 226868 = CYG X-1. I. Radial velocities and orbital elements. Gies, D. R. ; Bolton, C. T. Abstract We have measured radial velocities for HDE 226868 from 78 high-dispersion spectrograms obtained between 1971 and 1981. The orbital elements derived from these data are essentially identical to those previously reported, except that we find the eccentricity is not statistically significant. The latter conclusion is independent of whether we consider our data as a whole or break it up into blocks obtained over a short period of time. Thus we cannot confirm the short-period apsidal motion that has been suggested by variations in the shape of the ellipsoidal light curve. The velocity curve derived from the hydrogen line radial velocities is distorted by the blending of emission with the absorption lines, but we find no evidence that the velocity curves derived from other lines are affected by either distortions of the primary or circumstellar material. We find no evidence for periods other than the orbital period, and we derive a 3 σ upper limit on changes in the orbital period, Pdot/P < 3 × 10-5 yr-1. Publication: The Astrophysical Journal Pub Date: September 1982 DOI: 10.1086/160250 Bibcode: 1982ApJ...260..240G Keywords: Binary Stars; Stellar Spectra; X Ray Astronomy; Orbital Elements; Radial Velocity; Spectrograms; Tables (Data); Astronomy full text sources ADS | data products SIMBAD (1) Related Materials (2) Part 2: 1986ApJ...304..371G Part 3: 1986ApJ...304..389G