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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 63433 b, K2-101 b, and Kepler-1643 b). In total, 28.3% ± 6.2% of the 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 (>4σ), 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 multiplanet TTVs, to measure the masses and eccentricities of these planets.
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This content will become publicly available on November 24, 2026
Ever Elusive Exospheres: One Probable Detection and Two Nondetections of H α Transits in Young Systems
Abstract Gaps in the exoplanet population, such as the Neptunian Desert, point to the importance of mass loss in sculpting the radii of close-in exoplanets. Young planets (<500 Myr) offer the opportunity to detect such mass loss while it is still strong, and to test models of the underlying physical processes. We search for evidence of an Hαtransit in high-resolution spectra of three young planets, HD 63433 b (400 Myr), DS Tuc A b (45 Myr), and HIP 67522 b (17 Myr) using HARPS-N, Magellan-PFS, and CHIRON, respectively. We validate our method by testing it on several photospheric lines less impacted by stellar variability. We find no evidence of a transit signal for HD 63433 b and DS Tuc A b (3σlimits of 0.9% and 0.3%, respectively). For HIP 67522 b, we detect significant excess absorption (3.44% ± 0.28%) aligned with the transit time, narrow compared to the stellar line, and blueshifted from the stellar rest frame. In combination, these suggest the signal is from the planet. However, stellar variation in the Hαline over the course of the observations is comparable in size to the transit signature and the duration is shorter than the photometric transit, so this detection requires confirmation. Our findings, and other recent results in the literature, suggest that planets younger than 50 Myr are more favorable for the detection of atmospheric escape with Hαobservations, though older populations might still show escape in other diagnostics.
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- Award ID(s):
- 2143763
- PAR ID:
- 10671752
- Publisher / Repository:
- Astronomical Journal
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 170
- Issue:
- 6
- ISSN:
- 0004-6256
- Page Range / eLocation ID:
- 348
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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