Abstract

Poster - Splinter ExoPlanets

Overcoming Stellar Activity in the Characterization of young Exoplanets

Benjamin Wechselberger
Ludwig-Maximilians-Universität München

Characterisation of young exoplanets (<1 Gyr) is essential to test and improve current planet formation and evolution models. These systems offer new constraints to models which are tuned to the known, mostly mature, exoplanet population. We present one of the youngest transiting exoplanets, with an age of 6 Myrs, orbiting a K-dwarf. The host star exhibits strong activity resulting in high pho- tometric variability, with the large scale variability being 35 times stronger than the transit depth and RV scatter (RMS ≈ 200 m/s) that far exceeds the expected Keplerian signal (∼ 10 m/s for a 30 M⊕ planet). This requires specialised methods to isolate and model the planetary signature. We use the Notch Detrending package (Rizzuto et al. 2017), following an ap- proach from Barber et al. (2024), to detect the transit with a period of P = 18.71 d and a depth of 2 ppt in the TESS light curves. For the analysis of the RV spec- tra (HARPS, ESPRESSO, NIRPS), a Gaussian Process (GP) informed by stellar activity indicators was needed to find the Keplerian signal. Identifying appropriate stellar activity indicators and avoiding overfitting with the GP remains challenging. We were able to retrieve a sensible upper mass limit for the planet. This can already help to constrain models on e.g. thermal contraction scenarios over the first Myrs of the planet lifetime and limits on the timescales of planet formation.