Primary orbit and the absorption lines of HDE 226868 (Cygnus X-1)

Journal Article · Thu Oct 01 00:00:00 EDT 1987 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/165641· OSTI ID:5554357

Ninkov, Z; Walker, G A.H.; Yang, S

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. 62 references.

• Research Organization: British Columbia Univ., Vancouver
• OSTI ID: 5554357
• Journal Information: Astrophys. J.; (United States), Vol. 321
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BINARY STARS
ABSORPTION SPECTRA
BLACK HOLES
COSMIC X-RAY SOURCES
HELIUM
MASS
ORBITS
ROTATION
COSMIC RAY SOURCES
ELEMENTS
FLUIDS
GASES
MOTION
NONMETALS
RARE GASES
SPECTRA
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources