| Abstract: | Rapidly rotating massive stars are often found in binary systems, and many of them interact with their companions over the course of their lifetime through close binary interaction. In such a scenario, an initially more massive donor star has stripped of its outer envelope to leave as a hot, naked helium core star, while the former mass gainer star has spun up after acquiring the mass and angular momentum transferred from the donor star. In this seminar, I will present the multi-wavelength observational efforts to detect and characterize the stripped helium companion stars in Galactic Be binary systems. These works include searching for the stripped stars in Be binaries of HR 2142 and 60 Cygni using the far-ultraviolet (FUV) spectroscopic observations from the International Ultraviolet Explorer (IUE). Continuing searches using the IUE database have detected a dozen of these candidate systems with a designation of Be+sdO binaries. Based on the spectroscopic analysis made from FUV observations from the Hubble Space Telescope, we have estimated the radii and effective temperatures of the sdO companions. In order to fully characterize the fundamental properties of these Be+sdO binaries, we carried out ground-based, long-term observing campaigns to measure the radial velocities of these stellar systems to determine their orbital parameters. The discovered Galactic Be+sdO binaries may only represent a small fraction of their population. Follow-up spectroscopy and interferometry will provide a complete set of atmospheric, physical, and orbital properties of these binary systems, and this information will be essential to benchmark theoretical models to constrain the physical processes associated with their formation and to trace their evolutionary histories.
Link to the seminar's Zoom meeting |