The circumstellar structure of the Be shell star phi Persei II. Modeling

We model Fe II 5317 emission lines and phase resolved He I 6678 and 5876 em ission lines of the bright B2e&sdO shell binary phi Per to find the size an d shape of the excitation region inside the circumprimary disk. We find the Fe II 5317 emission to originate within 9 stellar radii in an axisymmetric disk around the primary. Orbital phase variations of He I 6678 are fit in terms of a disk sector with disk radius of 10 stellar radii and opening ang le of similar or equal to 120 degrees facing the secondary. This region can be alternatively described by an intersection of a sphere around the secon dary and the circumprimary disk with a penetration depth of about 7 R-*. Si milar fit values are found for He I 5876. The enigmatic orbital phase prece dence of shell occurrence in the He I emission features is discussed. We fa vor a model in which the inner He I shell is deformed because of differenti al rotation in combination with a finite recombination time.