This project aims to improve the methods used to extract and model stellar Radial Velocity (RV) observations to enable the detection of exoplanets, including those that could potentially support life, around nearby stars. The main challenge in the field is the intrinsic variability of the host stars, which causes complex apparent RV variations that are considerably larger than the planetary signals of interest. As it is difficult to model these stellar nuisance signals from first principles, we use data-driven models based on Gaussian Processes (GPs) developed by the PI and her team. Over the course of the project we will test and refine these models on archival data for a wide range of stars, use them to find and characterise new planets (in particular young planets orbiting active stars, and comparatively small and cool planets), and take part in the preparation and early operations phase of the Terra Hunting Experiment (THE).
In this report, we summarise the work done during the first 30 months (2.5 years) of the 5-year grant period. During that time, we have focused mainly on methodological developments, improving upon the state of the art methods previously developed in the PI's group to disentangle between stellar and planetary signals in the time domain, by also modelling them in the wavelength domain, and starting to couple the two. We have also successfully applied these methods to observations of young, planet hosting stars, allowing us to measure, for the first time, the masses of several young transiting hot Netpunes and super-Earths, which are key laboratories of planet formation and evolution. In the background, we are also preparing for the THE survey, contributing to the consortium-wide effort to select targets and optimize the observing strategy.
Over the remainder of the grant, we will focus increasingly on analysing new and archival observations of Sun-like stars, pushing the detection limits towards Earth analogues, and exploring the "warm super-Earth" or "Super-Venus" regime which is very much unchartered so far. In parallel, we will continue to deepen our understanding of the physical processes that give rise to the "nuisance" activity signals, probing inhomogeneous, 3-D stellar atmopsheres in increasing details using a suite of spectroscopic diagnostics tailored on the Solar case (for which simultaneous resolved observations can be compared directly with the disk-integrated spectra).
