Spectroscopic and photometric analysis of the WN7 eclipsing binary CQ Cephei

Abstract

Spectroscopic observations made at Kitt Peak in September 1978 are used in analyzing the orbit of the WN7 eclipsing binary CQ Cep. The Wolf-Rayet emission lines and their biolet-displaced absorption edges reveal a circular orbit with a velocity amplitude (semiamplitude) of 310 km/s (N IV 4058-A emission) in the photometric 1.64d period. The violet-displaced hydrogen Balmer absorption lines are found to vary in phase with the W-R emission, indicating that they originate in the W-R atmosphere rather than in the unseen companion star. The He II 4686-A emission exhibits a heavily distorted velocity curve. The violet-displaced absorption component of the He I 3889-A line reveals a nearly constant velocity of approximately 1150 km/s, indicating its origin in a common binary system envelope.