CfA Colloquium: April 24, 2003

Speaker: Daniel Steeghs (CfA Clay Fellow)

Title: Mapping interacting binaries

Abstract: Interactions between stars that are gravitationally bound in double star systems significantly affect the makeup and evolution of stellar populations in galaxies. In many cases, binary stars orbit close enough for mass exchange to occur between the stellar components. Such accretion of mass in a binary is thought to power the most energetic objects in our galaxy. I discuss how tomographic imaging techniques, based on very similar methods routinely employed in the medical profession, allow us to study this interaction and exchange of mass in detail. Reconstructed tomograms reveal the complex dynamics of the flow of gas around white dwarfs, neutron stars and stellar black holes on scales that cannot be imaged directly. Through these tomograms, we are not only able to establish basic parameters such as the masses and composition of the binary components, but also witness dramatic changes in the gas flow in real-time. I illustrate several recent results based on the application of these techniques. These include the first stellar mass determinations of several crucial systems, a reconstructed movie illustrating the presence and evolution of tidally driven spiral structures around accreting white dwarfs, and the properties of recently discovered binaries whose orbital periods are as short as a few minutes.