The Spectrographic Orbit of the Companion to Rigel.

The orbit of the companion of Rigel has been determined from eighteen spectrograms with a dispersion of 10 A/mm. This orbit differs little from a circle. The period is 9.860 days; the ratio of the masses of the two components, m2/ml = 0.767; (ai + a2) sin i = 7.771 X 106 km; and the center of mass velocity, ~y = +19.1 km/sec. No satisfactory reconcifiation of the double-star observations with the spectrographic orbit seems possible at present. The difference between the systemic velocity of the companion and the velocity of Rigel itself cannot be precisely stated but probably does not exceed 4 km/sec