Thursday, June 12 - Plenary Session

Name:  A. F. Lanza

Affiliation:  INAF-Osservatorio Astrofisico di Catania, Italy

Title:  Star-Planet Interactions

Abstract:
Stars interact with their planets through gravitation, radiation, and magnetic fields. I shall focus on the interaction between late-type stars with an outer convection zone and close-in planets, i.e., with an orbital semimajor axis smaller than 0.15 AU. In particular, I shall review the roles of tides and magnetic fields considering some key observations and discussing theoretical scenarios for their interpretation with an emphasis on open questions. Tides in systems consisting of close-in planets and late-type stars occur in a regime far from synchronization and with extreme values of the mass ratios of the two bodies. This is challenging for current tidal theories based on the observations of binary systems consisting of stars with similar masses and synchronized rotation and orbital motion. Many close-in planets orbit inside the Alfven radii of their host stars leading to magnetic interactions remarkably different than in the case of Solar System where the planets are in the region where the solar wind is streaming in a super-alfvenic regime. The energy dissipated by magnetic reconnection events involving stellar and planetary fields can reach the star producing transient coronal and chromospheric emissions, but can also increase the evaporation rate of the planetís atmosphere and induce a remarkable time variability in it. Moreover, the stellar magnetized wind can be modified by a close-in planet, changing the angular momentum loss rate and the evolution of stellar rotation. Recent observations, both from the ground and with the space telescopes Kepler and CoRoT, open new interesting perspectives in these fields, in particular for the study of stellar rotation and the effects of tides and magnetic interactions on the evolution of stellar angular momentum. Moreover, the new opportunities opened by the recently selected ESA space mission PLATO will be briefly considered.