Browsing by Author "Izidoro, André"

Now showing 1 - 3 of 3
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    Accretion and Uneven Depletion of the Main Asteroid Belt
    (IOP Publishing, 2024) Deienno, Rogerio; Nesvorný, David; Clement, Matthew S.; Bottke, William F.; Izidoro, André; Walsh, Kevin J.
    Accretion and Uneven Depletion of the Main Asteroid Belt, Rogerio Deienno, David Nesvorný, Matthew S. Clement, William F. Bottke, André Izidoro, Kevin J. Walsh
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    Resonant sub-Neptunes are puffier
    (edp Sciences, 2024) Leleu, Adrien; Delisle, Jean-Baptiste; Burn, Remo; Izidoro, André; Udry, Stéphane; Dumusque, Xavier; Lovis, Christophe; Millholland, Sarah; Parc, Léna; Bouchy, François; Bourrier, Vincent; Alibert, Yann; Faria, João; Mordasini, Christoph; Ségransan, Damien
    A systematic, population-level discrepancy exists between the densities of exoplanets whose masses have been measured with transit timing variations (TTVs) versus those measured with radial velocities (RVs). Since the TTV planets are predominantly nearly resonant, it is still unclear whether the discrepancy is attributed to detection biases or to astrophysical differences between the nearly resonant and non resonant planet populations. We defined a controlled, unbiased sample of 36 sub-Neptunes characterised by Kepler, TESS, HARPS, and ESPRESSO. We found that their density depends mostly on the resonant state of the system, with a low probability (of ) that the mass of (nearly) resonant planets is drawn from the same underlying population as the bulk of sub-Neptunes. Increasing the sample to 133 sub-Neptunes reveals finer details: the densities of resonant planets are similar and lower than non-resonant planets, and both the mean and spread in density increase for planets that are away from resonance. This trend is also present in RV-characterised planets alone. In addition, TTVs and RVs have consistent density distributions for a given distance to resonance. We also show that systems closer to resonances tend to be more co-planar than their spread-out counterparts. These observational trends are also found in synthetic populations, where planets that survived in their original resonant configuration retain a lower density; whereas less compact systems have undergone post-disc giant collisions that increased the planet’s density, while expanding their orbits. Our findings reinforce the claim that resonant systems are archetypes of planetary systems at their birth.
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    The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains
    (IOP Publishing, 2022) Izidoro, André; Schlichting, Hilke E.; Isella, Andrea; Dasgupta, Rajdeep; Zimmermann, Christian; Bitsch, Bertram
    The size frequency distribution of exoplanet radii between 1 and 4R ⊕ is bimodal with peaks at ∼1.4 R ⊕ and ∼2.4 R ⊕, and a valley at ∼1.8 R ⊕. This radius valley separates two classes of planets—usually referred to as “super-Earths” and “mini-Neptunes”—and its origin remains debated. One model proposes that super-Earths are the outcome of photoevaporation or core-powered mass loss stripping the primordial atmospheres of the mini-Neptunes. A contrasting model interprets the radius valley as a dichotomy in the bulk compositions, where super-Earths are rocky planets and mini-Neptunes are water-ice-rich worlds. In this work, we test whether the migration model is consistent with the radius valley and how it distinguishes these views. In the migration model, planets migrate toward the disk’s inner edge, forming a chain of planets locked in resonant configurations. After the gas disk dispersal, orbital instabilities “break the chains” and promote late collisions. This model broadly matches the period-ratio and planet-multiplicity distributions of Kepler planets and accounts for resonant chains such as TRAPPIST-1, Kepler-223, and TOI-178. Here, by combining the outcome of planet formation simulations with compositional mass–radius relationships and assuming the complete loss of primordial H-rich atmospheres in late giant impacts, we show that the migration model accounts for the exoplanet radius valley and the intrasystem uniformity (“peas in a pod”) of Kepler planets. Our results suggest that planets with sizes of ∼1.4 R ⊕ are mostly rocky, whereas those with sizes of ∼2.4 R ⊕ are mostly water-ice-rich worlds. Our results do not support an exclusively rocky composition for the cores of mini-Neptunes.