Abstract

Active regions on stellar surfaces induce signals in radial velocity (RV) time series that limit our ability to detect planetary signals. In order to detect planetary-induced RV signals, we need to perform informed modelling of the stellar activity. The use of spectroscopic activity indicators is useful to understand the behaviour of stellar signals in RV data. However, the stellar activity manifests with different behaviour and shapes in different spectroscopic time series. Therefore, the use of activity indicators to inform the modelling of the stellar signal in the RV data has to be taken carefully. In this talk, I discuss how a multidimensional Gaussian Processes framework can be used to constrain the stellar signal in multiple spectroscopic time series. This approach takes into account the different shapes in which stellar activity appears in the spectroscopic time series. I will show some practical examples of how this approach has been used to detect planet signals tens of times smaller than the stellar signal for young active stars.