A radius valley across stellar types

JULIA VENTURINI; MARÍA PAULA RONCO; OCTAVIO MIGUEL GUILERA; JONAS HALDEMANN; CHRISTOPH MORDASINI; MARCELO MIGUEL MILLER BERTOLAMI

Ringberg, Munich, Alemania

Congreso; Density Matters; 2024

The radius valley separating super-Earths from mini-Neptunes is a fundamental benchmark for theories of planet formation andevolution. Observations show that the location of the radius valley decreases with decreasing stellar mass and with increasing orbitalperiod. Here, we build from our previous pebble-based formation model, which, combined with photoevaporation after disc dispersal,unveiled the radius valley as a separator between rocky- and water-worlds. In this study, we expand our models for a range of stellarmasses spanning from 0.1 to 1.5 M. We find that the location of the radius valley is well described by a power-law in stellar massas Rvalley = 1:8197M0:14(+0:02=􀀀0:01)? , which is in excellent agreement with observations. We also find very good agreement with thedependence of the radius valley on orbital period, both for FGK- and M-dwarfs. Additionally, we note that the radius valley getsfilled towards low stellar masses, particularly at 0.1-0.4 M, yielding a rather flat slope in Rvalley 􀀀 Porb. This is the result of orbitalmigration occurring at lower planet mass for less massive stars, which allows for low-mass water-worlds to reach the inner regionsof the system, blurring the separation in mass (and size) between rocky- and water-worlds. Furthermore, we find that for planetaryequilibrium temperatures above 400 K, the water in the volatile layer exists fully in the form of steam, pung the planet radiusup compared to condensed-water worlds. This produces an increase in planet radii of 30% at 1 M and of 15% at 5 Mcompared to condensed-water-worlds. As with Sun-like stars, we find that pebble accretion leaves its imprint on the overall exoplanetpopulation as a depletion of planets with intermediate compositions (i.e, water mass fractions of 0 􀀀 20%), carving an planetdepleteddiagonal band in the mass-radius diagrams. This band is better visualised when plotting the planet mean density in terms ofEarth-like composition. This change of coordinates makes the valley emerge for all stellar masses.