Resolving the Nature of RV Tauri Variable Systems Using Unprecedented Observations From the Kepler and XMM-Newton Space Telescopes

RV Tauri variables are identified as a subclass of post-Asymptotic Giant Branch in binary systems surrounded by a circumbinary disk. Their signature light curves display alternating deep and shallow minima due to pulsations. The RVb-type RV Tauri variables exhibit an additional modulation in mean brightness that is on the order of ~470-2800 days. Though binarity has been shown to play a key role in the dynamics and evolution of these old systems, the interconnection between the various physical processes remains poorly understood. In this dissertation talk I summarize what we have learned from the multiwavelength observational analysis of two archetypal RVb systems, DF Cyg and U Mon. We find evidence for disk obscuration, binary interaction, and disk evolution. Using the high-precision light curve observations from Kepler we show how the decrease in flux from the RVb maximum to RVb minimum, as well as the reduction of the short-term pulsation amplitude, could be caused by the circumbinary disk periodically obscuring DF Cyg. We also introduce observations from XMM-Newton, SMA, DASCH, and AAVSO, spanning the largest coverage of the electromagnetic spectrum (X-ray to millimeter) and longest temporal baseline of U Mon, which also becomes the first RV Tauri system detected in X-rays. The origin of the X-ray emission from U Mon is unclear, but suggests that binary and/or circumbinary disk interactions may play a role. This has opened new possibilities for considering X-rays in forthcoming studies to place further constraints and a deeper understanding of magnetism and accretion of these evolved binary systems.