Exploring the origins and diversity of planetary systems: insights from young giant planets

Exploring the origins and diversity of planetary systems: insights from young giant planets

Studying planetary systems in their infancy is essential to understand of the origin of gas giant exoplanets found to closely orbit their host stars. Tied with the study of young stars is the challenge of stellar activity, arising from their fast rotation and strong magnetic fields. This cocktail yields a wealth of phenomena able to mask signatures from orbiting planets, greatly hampering our capacity to detect them.

In this Ph. D. project, we first assessed our chances to detect non-transiting gas giants in close orbit around young and very active stars, using legacy data from a non-stabilised spectrograph. We performed an injection and recovery study using Doppler Imaging and Gaussian Processes as stellar activity mitigation strategies. We were able to recover planets down to 4 times below the stellar noise and conclude that both a robust statistical framework and high quality datasets are crucial. We then precisely measured, despite the stellar activity, the spin–orbit alignment for the youngest Jupiter-sized planet known to transit, the 17 Myr old HIP 67522 b, and showed that its origin pathway is unlikely to be the commonly invoked high eccentricity migration. Finally, we conducted a 2-year radial velocity follow up yielding the discovery of TOI- 4562 b, identified in Transiting Exoplanet Survey Satellite data. TOI-4562 b is a highly eccentric (e = 0.77±0.03), 225 day period, 300±190 Myr old Jupiter analogue. We strongly suspect the presence of a companion that could be at the origin of TOI-4562 b eccentricity. We hope to reveal the 3D architecture of this system with on-going observing campaigns.

This work paves the way for further characterisation of young short-orbit gas giants, key to constrain models explaining their formation and evolution.

A Heitzmann, et al., Planets around young active solar-type stars: assessing detection capabilities from a non-stabilized spectrograph, Monthly Notices of the Royal Astronomical Society, Volume 505, Issue 4, August 2021, Pages 4989–5011, https://doi.org/10.1093/mnras/stab1586 (This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.)

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