A Spectrographic Study of the Triple System in 59 D Serpentis.

Abstract

In the visual double star 59 d Serpentis the primary component (5.4 mag.) is a triple system giving a composite spectru?n of GO and A2. The secondary component (7.8 mag.) is AO. Spectrograms of the triple system were taken at Yerkes Observatory in 1928-1929, at Ann Arbor in 1938-1942, and at Mount Wilson in 1941-1942. Velocities from these plates, combined with thirteen scattered observations in 1903-1909, yielded for the G-type star a period of 386.0 days. The following elements were derived: = 277°, K = 28 km/sec, -y = -23 km/sec, T = 221 days, and e = 0.47. For the orbit of the center of mass of the A-type binary system the above elements were adopted, except for w = 97° and K = 19 km/sec. A least-squares solution of the orbit of the A-type stars was made after the period of 1.8505205 days had been determined graphically from a composite plot of velocities in 1938-1942. The respective values of K were 90 and 100 km/sec, e was assumed to be zero, and was also assumed to be zero, after the correction obtained in the solution was absorbed by revision of K in the center-of-mass orbit. On six plates an interstellar calcium line was measured between the components of the K line.. From a knowledge of m sin3 i, the ratio of the masses for the members of the triple system, and a dynamical parallax, approximate values were obtained for the masses and inclinations. The probable inclinations of the orbits preclude an eclipse of any components. The radii of the stars were also ap- proximated. Four low-dispersion spectrograms were taken of the faint visual companion. Velocities derived from these plates, relative to that of the center of mass of the triple system, suggest that this star might be a binary. A negligible change in the separation of 4" has been observed during the past century