Revisiting the exoplanet radius valley with host stars from SWEET-Cat

Abstract

The radius valley,a deficit of planets near 2 ${\mathrm{R}}_{\oplus }$, was observed among exoplanets of radius $\lesssim$ 5 ${\mathrm{R}}_{\oplus }$ with periods $<$ 100 days by NASA's $Kepler$ mission. It separates super-Earths (rocky, $\lesssim 1.9$ ${\mathrm{R}}_{\oplus }$) from sub-Neptunes (volatile-rich, $\gtrsim 2$ ${\mathrm{R}}_{\oplus }$) and may arise from formation conditions or atmospheric loss. Disentangling these mechanisms has led to numerous studies of population-level trends, although the resulting interpretations remain sensitive to sample selection and the robustness of host-star parameters. We re-examine its existence, depth, and dependence on period, flux, stellar mass, and age. Using SWEET-Cat and MAISTEP tool, we derived stellar parameters for 1,221 main-sequence stars (1,405 planets), with effective temperatures 4400--7500 K and radii 0.62--2.75 ${\mathrm{R}}_{\odot }$, achieving 2\% precision in radius and mass. Planetary radii were recomputed from radius ratios, yielding 5\% median uncertainty. The valley is partially filled near 2 ${\mathrm{R}}_{\oplus }$ and depends on period, flux, and stellar mass, with slopes $-0.12_{-0.01}^{+0.02}$, $0.10_{-0.03}^{+0.02}$, and $0.19_{-0.07}^{+0.09}$. Sub-Neptunes show a stronger stellar mass-dependent trend than super-Earths ($0.17_{-0.04}^{+0.04}$ vs $0.11_{-0.05}^{+0.05}$). With stellar age, the super-Earth/sub-Neptune ratio rises from $0.51_{-0.08}^{+0.11}$ ($<3$ Gyr) to $0.64_{-0.11}^{+0.11}$ ($\gtrsim 3$ Gyr), and the valley becomes shallower and shifts to larger radii. A 4D fit shows consistent slopes with 2D analyses and a weaker age trend ($0.07_{-0.04}^{+0.03}$). These results suggest prolonged atmospheric loss, which is consistent with a core-powered mass loss scenario and emphasize the need for improved determinations, a goal expected to be achieved by future missions like PLATO.

References in corpus (38)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• ESPRESSO@VLT -- On-sky performance and first results
• A Steeper than Linear Disk Mass-Stellar Mass Scaling Relation
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters
• The Extreme Ultraviolet and X-Ray Sun in Time: High-Energy Evolutionary Tracks of a Solar-Like Star
• An ancient extrasolar system with five sub-Earth-size planets
• Atmospheric Mass Loss During Planet Formation: The Importance of Planetesimal Impacts
• The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
• Evolution of the radius valley around low mass stars from $Kepler$ and $K2$
• Estimating distances from parallaxes. III. Distances of two million stars in the Gaia DR1 catalogue
• The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• Photoevaporation vs. core-powered mass-loss: model comparison with the 3D radius gap
• SWEET-Cat 2.0: The Cat just got SWEETer; Higher quality spectra and precise parallaxes from GAIA eDR3
• EUV irradiation of exoplanet atmospheres occurs on Gyr timescales
• DREAM I. Orbital architecture orrery
• A deep radius valley revealed by Kepler short cadence observations
• A fading radius valley towards M-dwarfs, a persistent density valley across stellar types
• Two Views of the Radius Gap and the Role of Light Curve Fitting
• Evolution of the Exoplanet Size Distribution: Forming Large Super-Earths Over Billions of Years
• Most super-Earths formed by dry pebble accretion are less massive than 5 Earth masses
• Current Population Statistics Do Not Favor Photoevaporation over Core-Powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap
• Mapping the exo-Neptunian landscape. A ridge between the desert and savanna
• TESS Asteroseismology of the known red-giant host stars HD 212771 and HD 203949
• SPInS, a pipeline for massive stellar parameter inference: A public Python tool to age-date, weigh, size up stars, and more
• Planets Across Space and Time (PAST). III. Morphology of the Planetary Radius Valley as a Function of Stellar Age and Metallicity in the Galactic Context Revealed by the LAMOST-Gaia-Kepler Sample
• Atomic diffusion and turbulent mixing in solar-like stars: Impact on the fundamental properties of FG-type stars
• The Influence of Age on the Relative Frequency of Super-Earths and Sub-Neptunes
• Unified simulations of planetary formation and atmospheric evolution: Effects of pebble accretion, giant impacts, and stellar irradiations on super-Earth formation
• SWEET-Cat: A view on the planetary mass-radius relation
• The Gaia spectroscopic catalogue of exoplanets and host stars
• MAISTEP -- a new grid-based machine learning tool for inferring stellar parameters I. Ages of giant-planet host stars