Signatures of star-planet interactions across the electromagnetic spectrum

<p>Close-in exoplanets can interact with their host stars magnetically, producing a variety of observable signatures at different wavelengths. For these interactions to occur, the planet must orbit inside the Alfv&#233;n surface of the stellar wind plasma, the region where magnetic forces dominate. As it is not generally possible to measure the plasma properties of the stellar winds of low-mass stars, the location of the Alfv&#233;n surface cannot be determined from observations. However, by coupling both observationally-derived magnetic field maps of the stellar surface and constraints on the stellar wind mass-loss rate with sophisticated magnetohydrodynamic models, we can obtain a 3D picture of the stellar wind plasma. This allows us to determine both the size and shape of the Alfv&#233;n surface, which in turn can be used to assess the feasibility of magnetic star-planet interactions occurring. In this talk, I will discuss how this approach allows us to predict and interpret hints of star-planet interactions from radio to X-ray wavelengths. I will illustrate how obtaining near-simultaneous observations at these wavelengths is our best bet for benchmarking these magnetohydrodynamic models.</p>