The spectrum of the VV Cephei star KQ Puppis (Boss 1985). III. A possible model.

Abstract

Following a previous study by Altamore et al. of the ultraviolet spectrum of KQ Pup, and the spectral Atlas of this star by Altamore et al., the authors analyze coudé and CAT CES optical spectra of the object observed during 1969-1984, and compare with IUE data obtained in 1979. The ultraviolet to infrared energy distribution appears bimodal with the hot component dominating below about 3600 Å and the M star above 4000 Å. The authors have fitted the dereddened energy distribution with a combination of a 30000K black body and of a M-supergiant spectrum (α Ori), and derived for KQ Pup a distance at 1400±200 pc. At this distance the hot component results a slightly underluminous B0 V star with a radius of 4.35 R_sun. The mass ratio of the components of the binary system seems to be close to unity. The authors propose for KQ Pup a binary model with a highly mass losing cool supergiant primary and an unevolved early-type secondary. The optical and UV emission lines are formed in the regions of the cool star wind which are ionized by the hot star radiation. A shock is probably produced near the hot star by the interaction of the cool star wind with the hot star wind. Instabilities probably occur near the shock which produce cool clouds from the M-star wind which may penetrate the hot star wind and be accreted.