Impact of rotation on synthetic mass-radius relationships of two-layer rocky planets and water worlds

Abstract

We have analyzed the effects of rotation on mass-radius relationships for single-layer and two-layer planets having a core and an envelope made of pure materials among iron, perovskite and water in solid phase. The numerical surveys use the DROP code updated with a modified polytropic equation-of-state (EOS) and investigate flattening parameters $f$ up to $0.2$. In the mass range $0.1M_{\oplus }<M<10M_{\oplus }$, we find that rotation systematically shifts the curves of composition towards larger radii and/or smaller masses. Relative to the spherical case, the equatorial radius $R_{eq}$ is increased by about $0.36f$ for single-layer planets, and by $0.30f$ to $0.55f$ for two-layer planets (depending on the core size fraction $q$ and planet mass $M$). Rotation is an additional source of confusion in deriving planetary structures, as the radius alterations are of the same order as i) current observational uncertainties for super-Earths, and ii) EOS variations. We have established a multivariate fit of the form $R_{eq}(M,f,q)$, which enables a fast characterization of the core size and rotational state of rocky planets and ocean worlds. We discuss how the observational data must be shifted in the diagrams to self-consistently account for an eventual planet spin, depending on the geometry of the transit (circular/oblate). A simple application to the recently characterized super-Earth candidate LHS1140b is discussed.

Accepted for publication in Astronomy and Astrophysics

References in corpus (25)

• Mass-Radius Relationships for Solid Exoplanets
• Detailed Models of super-Earths: How well can we infer bulk properties?
• Radius and Structure models for the First Super-Earth Planet
• Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres
• Tidal Locking of Habitable Exoplanets
• A generalized bayesian inference method for constraining the interiors of super Earths and sub-Neptunes
• Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars
• AQUA: A Collection of H${}_2$O Equations of State for Planetary Models
• Irradiated ocean planets bridge super-Earth and sub-Neptune populations
• Mass-radius relationships for irradiated ocean planets
• Planetary system LHS 1140 revisited with ESPRESSO and TESS
• Constraints on Super-Earths Interiors from Stellar Abundances
• From super-Earths to sub-Neptunes: Observational constraints and connections to theoretical models
• Constraining the Oblateness of Kepler Planets
• Super-Earths and Earth-like Exoplanets
• A Numerical Method for Generating Rapidly Rotating Bipolytropic Structures in Equilibrium
• On the Effects of Planetary Oblateness on Exoplanet Studies
• Spin of protoplanets generated by pebble accretion: Influences of protoplanet-induced gas flow
• Detecting Planetary Oblateness in the Era of JWST: A Case Study of Kepler-167e
• Constraining the oblateness of transiting planets with photometry and spectroscopy
• Toroidal figures of equilibrium from a 2nd-order accurate, accelerated SCF-method with subgrid approach
• An extremely low-density exoplanet spins slow
• The equilibrium of over-pressurised polytropes
• RUBIS: a simple tool for calculating the centrifugal deformation of stars and planets
• The influence of a static planetary atmosphere on spin transfer during pebble accretion

Cited by in corpus (1)

• A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations