Activity in close in planet hosts: establishing a homogeneous database

Our recent work has focussed on extremely close-in exoplanets which are losing mass as a result of their proximity to their host star. These systems are particularly interesting because they offer the potential to determine the close-in planets' chemical composition by the technique of transmission spectroscopy (e.g. Fossati et al 2010; Haswell et al 2012). This information provides key constraints to models of planet formation and evolution, and helps place our own Solar System in context. Our Hubble Space Telescope observations revealed that mass loss from the extreme hot Jupiter, WASP-12b, feeds a diffuse gas shroud around the planetary system, completely absorbing the starlight at the centres of the MgII h&k lines. We subsequently found a similar signature for WASP-12 in the optical CaII H&K absorption lines, and showed that WASP-12 and several other close-in hot Jupiter exoplanets have anomalously low fluxes in the cores of their CaII H&K lines (Fossati et al 2013).
These findings inspired us to begin a carefully targeted search for close-in mass-losing planets around nearby bright stars. We identified several dozen target stars among thousands of bright stars through detailed consideration of anomalies apparent in their spectral lines (Haswell et al 2015; Staab 2016). We have recently completed the first stage of our radial velocity observations, and find that most of our targets appear to be genuine planet hosts. Extrapolating from this, we will have identified several previously unknown mass-losing planets orbiting nearby, bright stars by the beginning of the proposed PhD project (Barnes et al, Haswell et al, Staab et al 2016 papers in prep.). These will be key planets for the new field of comparative planetology, allowing planet atmospheric and/or surface composition (i.e. the planetary material feeding the mass loss) to be determined as a function of stellar properties and planetary parameters such as orbital distance, eccentricity, mass and radius.