Oral Abstract

Invited talk (I0.1) Onno Pols (Radboud Universiteit Nijmegen)

The mysterious evolution of AGB binaries

A wide variety of low- to intermediate-mass binary systems show evidence of having undergone interaction during the asymptotic giant branch (AGB) phase of evolution. These include post-AGB stars in binaries, as well as unevolved stars showing pollution by AGB nucleosynthesis from a companion, such as barium stars and carbon-enhanced metal-poor (CEMP-s) stars. What all these and several other classes of binaries have in common are intermediate-size orbits (periods of order 1-10 years) and substantial eccentricities - both contrary to expectations from binary evolution theory. The long-standing problem of their mysterious orbits has defied explanation for several decades, and yet these systems are very common. They also challenge our understanding of binary evolution channels that lead to much more compact white-dwarf binaries, such as those producing gravitational-wave sources and thermonuclear supernovae.

In this talk I will highlight efforts to shed light on the evolution of these former AGB binaries, by means of detailed stellar modelling, hydrodynamical simulations, and binary population synthesis.