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arXiv · 2303.12616

The orbital and physical properties of five southern Be+sdO binary systems

Luqian Wang·Douglas R. Gies·Geraldine J. Peters·Zhanwen Han
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Abstract

Close binary interactions may play a critical role in the formation of the rapidly rotating Be stars. Mass transfer can result in a mass gainer star spun up by the accretion of mass and angular momentum, while the mass donor is stripped of its envelope to form a hot and faint helium star. FUV spectroscopy has led to the detection of about 20 such binary Be+sdO systems. Here we report on a three-year program of high quality spectroscopy designed to determine the orbital periods and physical properties of five Be binary systems. These binaries are long orbital period systems with $P =$ 95 to 237 days and with small semi-amplitude $K_1<11$ km s$^{-1}$. We combined the Be star velocities with prior sdO measurements to obtain mass ratios. A Doppler tomography algorithm shows the presence of the He II $λ4686$ line in the faint spectrum of the hot companion in four of the targets. We discuss the observed line variability and show evidence of phased-locked variations in the emission profiles of HD 157832, suggesting a possible disk spiral density wave due to the presence of the companion star. The stripped companions in HD 113120 and HD 137387 may have a mass larger than the 1.4 $M_\odot$ indicating that they could be progenitors of Type Ib and Ic supernovae.

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Luqian Wang, Douglas R. Gies, Geraldine J. Peters, Zhanwen Han. 2023-03-22. The orbital and physical properties of five southern Be+sdO binary systems. https://doi.org/10.3847/1538-3881%2Facc6ca

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