The Primary Orbit and Absorption Lines of HDE 226868 (Cygnus X-1) (original) (raw)
NASA/ADS
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Abstract
From Reticon spectra of about 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 + or - 1.0 km/s and e = 0.0. Combining historical velocities from the literature with present data and applying a period-folding analysis, a period of 5.59964 + or - 0.00001 days is found. These values agree well with those published by Gies and Bolton (1982). The value of v sin i is estimated to be 94.3 + or - 5 km/s 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 ratio between 1.5 and 2.3. An absolute magnitude of -6.5 + or - 0.2 is derived from the equivalent width of H-gamma (1.5 + or - 0.1 A) and the calibration of Walker and Millward (1985), which is consistent with the spectral classification of O9.7 Iab. Assuming 20 solar masses as a reasonable estimate for the mass of the primary implies a mass of 10 + or - 1 solar masses for the secondary.
Publication:
The Astrophysical Journal
Pub Date:
October 1987
DOI:
Bibcode:
Keywords:
- Absorption Spectra;
- Cygnus Constellation;
- Stellar Orbits;
- X Ray Binaries;
- Black Holes (Astronomy);
- Helium;
- O Stars;
- Stellar Spectra;
- Astrophysics;
- STARS: INDIVIDUAL HENRY DRAPER NUMBER: HDE 226868;
- STARS: INDIVIDUAL CONSTELLATION NAME: CYGNUS X-1;
- X-RAYS: BINARIES