Accreting Double white dwarf binaries: Implications for LISA

Abstract

We explore the long-term evolution of mass-transferring white dwarf binaries undergoing both direct-impact and disk accretion and explore implications of such systems to gravitational wave astronomy. We cover a broad range of initial component masses and show that these systems, the majority of which lie within the LISA sensitivity range, exhibit prominent negative orbital frequency evolution (chirp) for a significant fraction of their lifetimes. Using a galactic population synthesis, we predict ~$2700$ double white dwarfs will be observable by LISA with negative chirps less than $-0.1\ yr^{-2}$. We also show that detections of mass-transferring double white dwarf systems by LISA may provide astronomers with unique ways of probing the physics governing close compact object binaries.