1997A&A...328..551K

An analysis of a rich series of spectroscopic and photometric observations of the Be star 4 Her led to the following conclusions: (o) 4 Her is another example of a long-term Be variable with a type of correlation between the brightness and emission strength, similar to 88 Her (V744 Her) and BU Tau (Pleione). It is argued that the formation of a new Be envelope of 4 Her starts with the creation of a slightly cooler pseudophotosphere at the equatorial regions of the star (seen under some intermediate inclination angle) which only gradually grows into an optically thin extended envelope. (o) Radial-velocity measurements of the centre of the Hα emission and of the photospheric lines confirm the binary nature of the star. The first reliable orbital elements are presented. The 46-d orbit is nearly circular and has a semiamplitude of 5-8km/s. An LTE model atmosphere analysis of the photospheric spectrum of the primary leads to T_eff=12500K, logg=4.0, and v.sin(i)=300km/s. No direct evidence of the low-mass secondary was found and the possibility that the secondary fills its Roche lobe can be safely excluded. (o) The central quasi-emission bumps (CQEB) visible as "doubling" of some shell lines appear during the phase of the formation of a new shell. They are strongest during the light minimum and become fainter as the Hα emission strengthens. (o) An unusual blue-shifted absorption component of the Hα line, never reported before, re-appears strictly periodically in the V peak of the Hα emission at a limited range of velocities and orbital phases. (o) It is argued that the observational facts about 4 Her are probably best reconciled by a model which assumes that the secondary is a hot and rotationally unstable object which looses mass towards the primary via a gas stream. However, some important findings remain unexplained.