The Orbital and Physical Properties of Five Southern Be+sdO Binary Systems

Close binary interactions may play a critical role in the formation of rapidly rotating Be stars. Mass transfer can result mass gainer star spun up by accretion and angular momentum, while donor is stripped its envelope to form hot faint helium star. FUV spectroscopy has led detection about 20 such Be+sdO systems. Here we report on three-year program high quality designed determine orbital periods physical properties five These binaries are long period systems with $P =$ 95 237 days small semi-amplitude $K_1<11$ km s$^{-1}$. We combined velocities prior sdO measurements obtain ratios. A Doppler tomography algorithm shows presence He II $\lambda 4686$ line spectrum companion four targets. discuss observed variability show evidence phased-locked variations emission profiles HD 157832, suggesting possible disk spiral density wave due The companions 113120 137387 have larger than 1.4 $M_\odot$ indicating that they could be progenitors Type Ib Ic supernovae.