Why are they wide? The surprises of evolved binaries.

About half of the stars are twins, bound to each other by their mutual gravitational force. The evolution of solar-type stars in such binary systems is surprisingly complex. It is fair to say that the component of a binary can influence the evolution in ways we don not understand yet... In this research project we want to focus on the evolution of binaries with well evolved components. Our inspiration comes from the results of our detailed observations which we perform, and are performing, at the 1.2m Flemish Mercator telescope. By using our telescope very regularly and for several years in a row, we discovered many evolved binaries, but they all turn around their companion stars in orbits which we did not expect to find ! The observed orbital characteristics should simply not exist for this type of stars according to current standard binary evolution theory. The goal of this project is to model the evolution of binaries such that the outcome and predictions match the observations. To do so, we will need to explore the effect of new binary interaction processes. When we understand the physical interactions better, we will make new models for the evolution of whole populations of binaries. When we succeed, the predictive power of our models will be much improved and we will use our new models to study a wide range of well observed, but poorly understood, types of binaries.

Keywords:Astrophysics, Stellar evolution in binaries, Observational Astrophysics

Disciplines:Astronomy and space sciences