THE ORBIT OF PHI-CYGNI MEASURED WITH LONG-BASE-LINE OPTICAL INTERFEROMETRY - COMPONENT MASSES AND ABSOLUTE MAGNITUDES

We present the orbit of the double-lined spectroscopic binary phi Cygni, the distance to the system, and the masses and absolute magnitudes of its components. The apparent orbit is based on our observations with the Mark III Optical Interferometer, the distance (80.8+/-1.8 pc) and component masses (2.54 +/-0.09 M. and 2.44+/-0.08 M., in agreement with the previous determination by McAlister [AJ, 101, 2207 (1982)]) are based on the Mark III data combined with a reinterpretation of the spectroscopic data of Rach & Herbig [ApJ, 133, 143 (1961)], and the absolute V magnitudes (0.77m+/-0.1m and 1.07m+/-0.1m) are derived from the distance, the cataloged integrated magnitude, and the magnitude difference from spectroscopic data. From a comparison of M(V) and (B-V) with the isochrones of Maeder & Meynet [A&AS 89, 451 (1991)], both components have undergone He ignition.