arXiv subjects

C. Staelen

Publications and source records attributed to C. Staelen.

3 recordsLinked to original sources

arXiv2026

Self-consistent-field method for triaxial differentiated bodies in hydrostatic equilibrium

Recent observations and models of Haumea and Quaoar suggest that both bodies are triaxial, but their shapes are inconsistent with Jacobi ellipsoids. To determine whether these objects can be at hydrostatic equilibrium, we propose a new numerical code, BALEINES, to study the hydrostatic shape of triaxial differentiated bodies. The fluid mass is assumed to be made of several homogeneous layers, which allowed us to rewrite the gravitational potential as a sum of proper surface integrals. In contrast to the classical self-consistent field method, we did not solve for the mass density, but for the shape of the boundary of all layers, meaning that only one point per layer is needed in the radial direction. The solution is still searched for iteratively. The code was benchmarked against analytical and numerical solutions. As a quick application, we studied the position of the axisymmetric-triaxial bifurcation point of two-layer systems. We show that the deviation from the Meyer bifurcation point in the single-layer case is below $10~\%$ in realistic cases. Based on this result, we conclude that the shape of Quaoar, as obtained in a recent work using a thermophysical model of the surface, is not compatible with a hydrostatic figure of equilibrium.

astro-ph.EP↗

arXiv2026

Equilibrium figure of Haumea and possible detection by stellar occultation

The equilibrium figure of dwarf planet Haumea is studied to determine if the observed shape is compatible with a differentiated hydrostatic body. Three groups of interior models of Haumea are assumed, all with a rocky core and a volatile-rich outer shell that may contain some porosity. A third layer located between the core and the outer shell has a density suggesting partial differentiation or the presence of a large fraction of organic matter. Using the code BALEINES, which solves for the equilibrium figures of the boundaries between layers, we show that the hydrostatic models closest to the shape derived by stellar occultation approach a state of critical rotation, which translates into a pinched shape with large deviations from an ellipsoid (up to 110 km). The previous stellar occultation and light curves cannot distinguish between the ellipsoid and the pinched shape, but we predict this figure could be observable on the next stellar occultation of Haumea on May 4, 2026, if some chords are obtained in the northern or southern limbs of the shadow.

astro-ph.EP↗

arXiv2025

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

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 $0.1 M_\oplus < M < 10 M_\oplus$, 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.

astro-ph.EP↗