From Reticon spectra of ~1 A resolution taken between 1980 and 1984, the radial velocity curve of HDE 226868 is found to be characteristic of a single-line spectroscopic binary with K = 75.0 +/- 1.0 km s^-1 and e=0.0. Combining historical velocities from the literature with our own data and applying a period-folding analysis, a period of 5.59964 +/- 0.00001 days is found. These values agree well with those published by Gies and Bolton in 1982, v sin i is estimated tob e 94.3 +/- 5 km s^-1 from CFHT Reticon spectra taken at 0.1 A resolution. Assuming that the rotation of the primary is synchronized to the orbital revolution of the secondary gives a primary to secondary mass between 1.5 and 2.3. An absolute magnitude of -6.5 +/- 0.2 is derived from the equivalent width of Hy (1.5 +/- 0.1 A) and the 1985 calibration of Walker and Millward which is consistent with the spectral classification of 09.7 Iab. Assuming 20 M_ as a reasonable estimate for the mass of the primary implies a mass of 10 +/- 1 M_ for the secondary. The equivalent width of Hy and HB are 20% larger at zero phase (X-ray minimum) of the 294 day X-ray period. A variation in the outflow rate from the primary could produce variations in both the Balmer-line equivalent widths and the X-ray flux (Refer to PDF file for exact formulas).
Department, Program, or Center
Chester F. Carlson Center for Imaging Science (COS)
Astrophysical Journal 321N1 (1987) 425-437
RIT – Main Campus