Abstract

In 2016 observers and theoreticians working on the diverse fields relevant to understand run-away and hyper-velocity stars gathered for the first time for a very successful workshop held in Bamberg, Germany. The meeting served to emphasize how high-precision astrometry will enable us to trace the place of origin of these stars and put constraints on the various proposed acceleration scenarios, but also to make use of these extreme stars as probes for addressing diverse astrophysical questions: Run-away stars are produced by dynamical interaction in various environments. Several processes have been suggested for their origin, which include ejection from star clusters and the Galactic Centre, in binary supernova explosions, and from satellite galaxies. Galactic center ejections are linked to the nature and environment of the central massive black hole; the trajectories of these stars - which travel from the very center to the outer halo - are potentially unique probes of the Galaxy-s dark matter distribution. The fastest run-away stars known, the hypervelocity stars, travel so fast that they are unbound from the Galaxy. The list of known run-aways includes early type main sequence stars in the Galactic halo as well as neutron stars. The second data release of the Gaia mission in April 2018 provided us with high-precision astrometry and already led to a wealth of new publications and discoveries. Gaia is about to transform this field of research. Three years after the first Stars on the Run meeting it is therefore time to assemble again observers and theoreticians working on the diverse fields relevant to understand run-away and hyper-velocity stars. This workshop attempts to cover the following topics: Surveys for run-away and hyper-velocity stars Kinematics and chemical composition of run-away and hyper-velocity stars Dynamics of stellar clusters and the Galactic centre Gravitational potential of the Milky Way Core-collapse and thermonuclear supernova ejection Satellite Galaxy and extragalactic origin Bow shocks from run-away stars