Stellar magnetic fields for star-planet interactions: HD 219134 and 55 Cnc

A promising avenue for investigating star-planet interactions (SPI) is the impact of stellar winds on exoplanets. Stellar winds cannot usually be directly observed, but realistic predictions can be made. These predictions rely on observations to constrain the large-scale stellar magnetic field geometry, which sculpts the wind. An additional rare but interesting mode of SPI is a more direct magnetic interaction, possible for planets orbiting inside the Alfven radius of the star. Here we present observations of two stars with close in exoplanets, 55 Cnc and HD 219134. We derive magnetic maps using Zeeman Doppler Imaging and wind models using MHD simulations. For HD 219134 b, the strong stellar wind impacting the planet may produce observable effects through sputtering of material from the planet's surface. For 55 Cnc e, the planet appears to orbit inside the Alfven surface of the wind, allowing for magnetic SPI, such as reconnection generating bright points on the star.

(Slides from a presentation in the Manifestations of Star-Planet Interactions splinter session)