New Perspectives on the Exoplanet Radius Gap from a Mathematica Tool and Visualized Water Equation of State

Zeng, Li; Jacobsen, S. B.; Hyung, Eugenia; Levi, Amit; Nava, Chantanelle; Kirk, James; Piaulet, Caroline; Lacedelli, G.; Sasselov, Dimitar; Petaev, M. I.; Stewart, S. T.; Alam, Munazza K.; López‐Morales, Mercedes; Damasso, M.; Latham, David W.

doi:10.3847/1538-4357/ac3137

Cited by 27 publications

(25 citation statements)

References 117 publications

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“…We selected three different setups from that study, which produced planetary systems dominated by rocky planets, water-rich planets, and planets of mixed compositions (water rich and rocky). We assume that at the end of the gas-disk-phase planets have atmospheres corresponding to 0.1%, 0.3%, 1%, or 5% of their masses, as suggested by observations (e.g., Lopez & Fortney 2013;Zeng et al 2021), numerical simulations (e.g., Lambrechts & Lega 2017;Moldenhauer et al 2022), and analytical atmospheric accretion models (e.g., Ginzburg et al 2016).…”

Section: Discussionmentioning

confidence: 99%

The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains

Izidoro

Schlichting

Isella

et al. 2022

ApJL

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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.

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Section: Discussionmentioning

confidence: 99%

The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains

Izidoro

Schlichting

Isella

et al. 2022

ApJL

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“…The simulations indicate that to achieve the observed planetary parameters at ages of a few Gyrs, the most extreme of these planets had to be formed with atmospheric mass fractions comparable to those currently present, namely ∼ 1 − 2%, which is an order of magnitude smaller than predicted by the atmospheric accretion models used in this study. At the same time, the mass-radius relation of these planets resembles that of icy cores (Zeng et al 2021), which could suggest that their internal structure is different from that of a rocky core surrounded by a hydrogen-dominated envelope, thus providing an alternative explanation. Independently of the core composition (e.g.…”

Section: Discussionmentioning

confidence: 95%

The mass-radius relation of intermediate-mass planets outlined by hydrodynamic escape and thermal evolution

Kubyshkina

Fossati

2022

A&A

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Context. Exoplanets in the mass range between Earth and Saturn show a large radius, and thus density, spread for a given mass. Aims. We aim at understanding to which extent the observed radius spread is affected by the specific planetary parameters at formation and by planetary atmospheric evolution, respectively. Methods. We employ planetary evolution modeling to reproduce the mass-radius (MR) distribution of the 198 so far detected planets with mass and radius measured to the ≤45% and ≤15% level, respectively, and less massive than 108 M ⊕ . We simultaneously account for atmospheric escape, based on the results of hydrodynamic simulations, and thermal evolution, based on planetary structure evolution models. Since the high-energy stellar radiation affects atmospheric evolution, we account for the entire range of possible stellar rotation evolution histories. To set the planetary parameters at formation, we use analytical approximations based on formation models. Finally, we build a grid of synthetic planets with parameters reflecting those of the observed distribution.Results. The predicted radius spread reproduces well the observed MR distribution, except for two distinct groups of outliers (≈10% of the population). The first group consists of very close-in Saturn-mass planets with Jupiter-like radii for which our modeling underpredicts the radius likely because it lacks additional (internal) heating similar to that responsible for inflation in hot Jupiters. The second group consists of warm (∼400-800 K) sub-Neptunes, which should host massive primordial hydrogen-dominated atmospheres, but instead present high densities indicative of small gaseous envelopes (<1-2%). This suggests that their formation, internal structure, and evolution is different from that of atmospheric evolution through escape of hydrogen-dominated envelopes accreted onto rocky cores. On average the observed characteristics of low-mass planets (≤10-15 M ⊕ ) strongly depend on the impact of atmospheric escape, and thus of the evolution of the host star's activity level, while primordial parameters are less relevant. Instead, for more massive planets, the parameters at formation play the dominant role in shaping the final MR distribution. In general, the intrinsic spread in the evolution of the activity of the host stars can explain just about a quarter of the observed radius spread.

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“…These contours are approximately identical regardless of the core composition, rocky or icy. The theoretical details, codes, and motivations of these composition models are explained by Zeng et al (2021).…”

Section: Mass-radius Diagram and Internal Structurementioning

confidence: 99%

A warm super-Neptune around the G-dwarf star TOI-1710 revealed with TESS, SOPHIE, and HARPS-N

König

Damasso

Hébrard

et al. 2022

A&A

Self Cite

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We report the discovery and characterization of the transiting extrasolar planet TOI-1710 b. It was first identified as a promising candidate by the Transiting Exoplanet Survey Satellite (TESS). Its planetary nature was then established with SOPHIE and HARPS-N spectroscopic observations via the radial-velocity method. The stellar parameters for the host star are derived from the spectra and a joint Markov chain Monte-Carlo (MCMC) adjustment of the spectral energy distribution and evolutionary tracks of TOI-1710. A joint MCMC analysis of the TESS light curve and the radial-velocity evolution allows us to determine the planetary system properties. From our analysis, TOI-1710 b is found to be a massive warm super-Neptune (M p = 28.3 ± 4.7 M ⊕ and R p = 5.34 ± 0.11 R ⊕ ) orbiting a G5V dwarf star (T eff = 5665 ± 55K) on a nearly circular 24.3-day orbit (e = 0.16 ± 0.08). The orbital period of this planet is close to the estimated rotation period of its host star P rot = 22.5 ± 2.0 days and it has a low Keplerian semi-amplitude K = 6.4±1.0 m s −1 ; we thus performed additional analyses to show the robustness of the retrieved planetary parameters. With a low bulk density of 1.03 ± 0.23 g cm −3 and orbiting a bright host star (J = 8.3, V = 9.6), TOI-1710 b is one of the best targets in this mass-radius range (near the Neptunian desert) for atmospheric characterization via transmission spectroscopy, a key measurement in constraining planet formation and evolutionary models of sub-Jovian planets.

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New Perspectives on the Exoplanet Radius Gap from a Mathematica Tool and Visualized Water Equation of State

Cited by 27 publications

References 117 publications

The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains

The Exoplanet Radius Valley from Gas-driven Planet Migration and Breaking of Resonant Chains

The mass-radius relation of intermediate-mass planets outlined by hydrodynamic escape and thermal evolution

A warm super-Neptune around the G-dwarf star TOI-1710 revealed with TESS, SOPHIE, and HARPS-N

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