1995A&A...304..235B

A detailed analysis of a very rich collection of spectroscopic and photometric observations of the bright Be star φ Per is presented. Earlier reports that φ Per is a double-lined spectroscopic binary consisting of two emission-line objects are confirmed. An orbital solution based on the emission-wing radial velocities for both stars has led to a determination of the orbital elements which defines the correct orbital phases. All data since the beginning of this century can be reconciled with a constant orbital period of 126.6731d±0.0071d. The new orbital solution gives lower masses than those found by earlier investigators, namely M₁sin³i=16.35M_☉ and M₂sin³i=1.69M_☉. These masses are in agreement with the recently derived spectral classes B0.5IVe and sdO6: for the primary and secondary, respectively. Long-term light variations are positively correlated with the emission strength, and in the U-B vs. B-V diagram the object has changed its apparent photometric type from a B supergiant toward an MS object. Dereddening of the mean seasonal UBV magnitudes from recent years (when spectra show the weakest recorded Balmer emission) leads to a photometric spectral type a bit earlier than B1V. An important and exciting finding is that the emission lines of both stars have been weakening simultaneously in recent years, which seems to indicate some kind of interaction between the binary components. The presence of rapid light variability is confirmed, but its more detailed analysis is postponed for another study. Low-amplitude orbital light variations with rather complicated light and color curves are found after the removal of long-term and rapid changes. The principal maxima and minima of the orbital light curves can be traced in both old and new photometry and can probably be attributed to specific circumstellar structures whose signatures are also seen spectroscopically. Finally, systematic secular changes in the shape and amplitude of the orbital radial-velocity curve of the Balmer shell lines are found, based on 1024 radial velocities spanning nearly a century.