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

We model Fe II 5317 emission lines and phase resolved He I 6678 and 5876 emission lines of the bright B2e&sdO shell binary phi Per to find the size and 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 angle of similar or equal to 120 degrees facing the secondary. This region can be alternatively described by an intersection of a sphere around the secondary and the circumprimary disk with a penetration depth of about 7 R-*. Similar fit values are found for He I 5876. The enigmatic orbital phase precedence of shell occurrence in the He I emission features is discussed. We favor a model in which the inner He I shell is deformed because of differential rotation in combination with a finite recombination time.