Joint Astrophysics Colloquium

Joint Astrophysics Seminar

Mapping accretion in ultra-compact white dwarf binaries

Danny Steeghs

Harvard/CFA

Tomographic imaging techniques allow us to resolve the dynamics of accretion in a wide range of close binaries. I will review the basics of the technique and present recent highlights including a reconstructed movie that replays the evolution of the accretion flow onto a white dwarf during an accretion disk outburst. I will then focus on the large population of double white dwarf binaries that populate our Galaxy. I discuss the possible outcomes of such systems as they evolve to shorter and shorter orbital periods. The accretion geometry during the mass transfer phase is crucial in determining the evolution of such objects. I present recent observations of the known accreting ultra-compact systems with orbital periods as short as 5 minutes. Such observations are crucial in determining the contribution of these binaries to the galactic populations of UV, X-ray and gravitational wave sources.