Searching for TTVs and Analyzing the Effects of Star Spots in Young Transiting Systems

The discovery of young (<800 Myr) transiting planets has provided a new avenue to explore planetary formation and evolution. Mass measurements for these planets are invaluable, but radial velocity surveys of young systems are often overwhelmed by stellar activity. Transit timing variations (TTVs) offer an alternative route to measure masses, yet they carry the risk of bias due to star spots deforming the transit profile. Here we search for, and assess the impact of spots on TTVs in a sample of 39 young systems hosting 53 transiting planets using data from Kepler, K2, and TESS. Through a spot-injection analysis, we find that simulated spots have a weak-to-negligible effect on the retrieved transit mid-times, and cannot explain the higher TTV fraction seen in young systems. We show that spot-crossing anomalies are sufficiently fit out by a Gaussian Process with a simple harmonic oscillator (SHO) kernel as an asymmetry in the data. Further, we find no correlation between spot coverage and TTV amplitude, and that systems with detected TTVs in our sample are less active than their counterparts. We identify new candidate TTVs for four planets (DS Tuc Ab, HD 63433b, K2-101b, and Kepler-1643b). While the candidate TTV signals detected here are sparsely sampled, our work provides a clear priority list for follow-up to measure the masses and eccentricities of these young planets.