The Spectroscopic Orbit of φ Cygni, a System with Two Late-Type Giants

Improved orbital elements for φ Cygni have been determined from 47 new high-dispersion spectroscopic observations. The period and eccentricity are 434.14 days and 0.559, respectively. Minimum masses plus the inclination of the visual orbit result in masses of 2.16 and 2.06 M_sun for the two giants. The small magnitude difference of 0.25 mag and a mass ratio of 1.044 indicate that both giants are most likely in the helium-burning phase of their evolution.