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WR140 configurations
The WC7 and O5 stars in WR140 move in very eccentric orbits with a period of 2900 days. WR140 (HD 193793) was long known to vary in radial velocity [1], but demonstration that it was a spectroscopic binary occurred [2] only when the periodicity of its dust formation was determined. Since then, consistent orbits have been derived from both optical and ultraviolet spectra. A consequence of the high eccentricity is that the separation of the stars varies by a factor of about 12 around the orbit. The densities of the stellar winds involved in the collision vary by more than a factor of 100, causing the intensity of the interaction processes, including radio and X-ray emission, to vary round the orbit and, when the interaction is greatest at periastron, dust formation. The X-ray and radio emission we observe is also affected by variable extinction along the sight-line through the stellar winds. We observe maximum radio emission at phases (~ 0.8) when the sightline crosses the edge of the wind-interaction region to the lower density O star wind. The configurations of the system near periastron are given in more detail here.
paths of stars and cw
key to image
Radial velocity orbital elements of WR 140
P (d) (2900)* 2893 (2900)* 2899.0 ± 1.3
e 0.84 ± 0.04 0.85 ± 0.01 0.87 ± 0.05 0.881 ± 0.007
omega 32° ± 8° (abs) 40.8° ± 3.1° 31° ± 9° 46°.7 ± 1°.6
To(JD) 2446160 ± 29 2449036 ± 4 2448956 ± 117 2446147.4 ± 3.7
To (Y) 1985.26 1993.13 1992.92 1985.22
Ko 28 ± 3 km/s 33.8 ± 1.5 km/s 25 ± 15 km/s 30.5 ± 1.9 km/s
Kw 79 ± 50 km/s 91.3 ± 4.8 km/s -- 82.0 ± 2.3 km/s
data optical, 1922-85 optical, 1980-93 UV, 1985-95 1922-2002 + UV
ref [2] [3] [4] [5]

* The 2900-d period in these solutions was adopted from the infrared light curves

Fully defined orbit in three dimensions

From high-resolution imaging of the radio emission between phases 0.74 and 0.97, Dougherty et al. [6] demonstrated that the WR 140 system rotates clockwise on the sky, and derived an orbital inclination, i = 122± 5°. The binary itself was resolved by Monnier et al. [7], who measured the stellar separation and position angle at phase 0.297. Using this and the inclination, Dougherty et al. determined the longitude of ascending node (Ω = 353±3°), completing the definition of the orbit.
References:
 
 
 
 
 
rev: 24 January 2008
Peredur Williams
[1] J.K. McDonald Pub. DAO VII, 311, 1947
[2] P.M. Williams et al. MNRAS 243, 662, 1990
[3] K. Annuk in IAU Symposium No. 163, p. 231, 1994
[4] D.Y.A. Setia Gunawan et al. A&A 376, 460, 2001
[5] S.V Marchenko et al. ApJ 596, 1295,2003.
[6] S.M. Dougherty et al. ApJ 623, 447, 2005.
[7] J.D. Monnier et al. ApJ 602, 57L, 2004.