The circumstellar structure of the Be shell star phi Per - I. Data analysis

We present new phase resolved observations of emission lines of the Be bina ry phi, Per. Analyzing the orbital phase variations in the He I emission features we fin d strong arguments that the feature as a whole originates in the outer part s of the disk around the primary star. in addition to the He I 6678 and 587 6 lines, the emission features with orbital phase variations were detected in three more Iie I lines. The observations are in agreement with the scena rio of Poeckert and others. in which the outer parts of an axisymmetric dis k are illuminated by the radiation of the secondary. The observations after 1996 are consistent with a growing global density inhomogeneity in the cir cumprimary disk as it occurs in disks of single Be stars. The combination o f the illumination effect and the increasing density inhomogeneity make phi Per an ideal laboratory to study density perturbations of circumstellar di sks of Be stars in more detail.