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ROYAL ASTRONOMICAL SOCIETY
VOL. XIV No. 1 JANUARY-FEBRUARY, 1920.
Whole No. 99
Notes from the Meteorological Service
Temperature, Precipitation and Earthquake Records for November,
J. S. Plaskett
The Spectroscopic Orbits and Dimensions of the Eclipsing Variables
- H. W. Barker
R. G. Haliburton
K. M. Chadwick
Relations Remarquable entre les Eléments du Système Solaire
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THE SPECTROSCOPIC ORBITS AND DIMENSIONS OF THE ECLIPSING VARIABLES U OPHIUCHI,
RS VULPECULAE AND TW DRACONIS
BY J. S. PLASKETT
- In determining the orbital elements of a spectroscopic binary from a series of measurements of the radial velocity, we can usually obtain the period, the eccentricity of the relative orbit, the maximum orbital velocity, the velocity of the centre of mass of the system, and the longitude and time of periastron.
The inclination of the plane of the orbit to the plane tangent to the celestial sphere is indeterminable and consequently, though formulae are available giving the semi-axis major and the mass, these both appear as functions of the sine of the inclination and their actual values must remain unknown so long as the inclination is unknown. Further, in respect to the expression for the mass of the system, it appears as a function of the ratio of the masses of the two bodies and unless this is known, which is the case only in the comparatively few instances when the spectra of both components are present, neither the mass of each nor the total mass of the system, always appearing with the function of the inclination attached, can be determined.
It is only in two special cases that the inclination can be obtained, in visual binaries whose orbital elements have been determined and in eclipsing (Algol) variables of which the light curve is accurately known.