Astronomy Colloquium

The evolution of stellar binaries with periods less than about one hour can be driven by the loss of orbital energy due to emission of gravitational waves.  Such binaries are typically the result of two episodes of common envelope evolution and can reach orbital periods of a few minutes, at which point mass transfer is initiated.  Mass transfer can be stable or unstable, and lead to a number of possible outcomes including Type Ia supernovae, R Cor Bor stars, or AM CVn systems. 

Over the last year and a half, the Zwicky Transient Facility (ZTF) has begun to detect numerous ultra-compact binary systems including five eclipsing double degenerate white dwarf binaries.  Only two eclipsing systems were previously known.  We have measured gravitational wave decay of the orbit in three double white dwarf systems.  Most of the ZTF ultra-compact binaries will be detectable by the future Laser Interferometer Space Antenna (LISA).  This talk will discuss the recent ZTF discoveries, and speculate about additional discoveries by ZTF and LSST, as well as describe the implications for space-based gravitational wave observations.