Searching for Transit Timing Variations in young transiting systems

TL;DR

The paper tackles measuring masses of young transiting planets by leveraging transit timing variations (TTVs) in place of radial-velocity masses hindered by stellar activity. Using Kepler, K2, and TESS data, it searches 39 young systems with 53 planets, recovering 11 known TTVs and identifying four new candidate TTVs. The TTV fraction among these young planets is $28.3 \pm 6.2\%$, significantly higher than the Kepler-old-system rate of $7.3 \pm 0.6\%$, with the difference remaining (> $4\sigma$) after accounting for data coverage. Spots have weak to negligible impact, and ongoing monitoring is required to validate planetary origins and enable mass and eccentricity inference for multi-planet TTVs, guiding follow-up observations.

Abstract

The discovery of young (<800 Myr) transiting planets has provided a new avenue to explore how planets form and evolve over their lifetimes. Mass measurements for these planets would be 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 that are less impacted by signals from the host star. Here we search for candidate TTVs in a sample of 39 young systems hosting 53 transiting planets using data from Kepler, K2, and TESS. We recover previously reported TTVs for 11 planets, including those in V1298 Tau, TOI-2076, Kepler-51, and TOI-1227, and identify new candidate TTVs for four planets (DS Tuc Ab, HD 63433b, K2-101b, and Kepler-1643b). In total, 28.3 +/- 6.2% of young planets in our sample show evidence of TTVs, which is higher than the rate from Kepler on mostly older systems (7.3 +/- 0.6%). Accounting for differences in data coverage and quality between Kepler and TESS only increases this difference (> 4$σ$), although differences in methodology make a totally fair comparison challenging. We show that spots have a weak-to-negligible impact on our results, and similarly cannot explain the higher TTV fraction. Longer-term monitoring will be required to validate these TTVs as planetary in nature and confirm the high TTV rate. While the candidate TTV signals detected here are sparsely sampled, our work provides a clear priority list for additional ground-based observations, and for multi-planet TTVs, attempt to measure the masses and eccentricities of these planets.