On the origin of dynamically isolated hot Earths

Abstract

A distinct population of planetary systems that contain dynamically isolated, Earth-size planets with orbital periods $P_{\mathrm{orb}}\sim 1$day was recently identified in an analysis of data from the Kepler planet candidate catalog. We argue that these objects could represent the remnant rocky cores of giant planets that arrived at the stellar vicinity on high-eccentricity orbits and were rapidly stripped of their gaseous envelopes after crossing their respective Roche limits (RLs) $a_{\mathrm{R},\mathrm{p}}$. In this picture, objects with $P_{\mathrm{orb}}\gtrsim 1$day are mostly "early" cores that originated in planets with an initial periastron distance $a_{\mathrm{per},0}\le a_{\mathrm{R},\mathrm{p}}$; they had high initial eccentricities but their orbits underwent fast tidal circularization after the cores were exposed. Objects with $P_{\mathrm{orb}}\lesssim 1$day are, by contrast, mostly "late" cores that originated in planets with $a_{\mathrm{per},0}>a_{\mathrm{R},\mathrm{p}}$; these planets underwent orbital circularization to a radius $>a_{\mathrm{per},0}$ but eventually reached $a_{\mathrm{R},\mathrm{p}}$ through tidal orbital decay. This picture naturally accounts for the spatial distribution of hot Earths and for the similarity of their inferred occurrence rate to that of hot Jupiters, and it fits well with the interpretation of the so-called sub-Jovian desert in the orbital-period--planetary-mass plane in terms of high-eccentricity planet migration to the vicinity of the RL.

ApJL, in press

References in corpus (11)

• Mass-Radius Relationships for Solid Exoplanets
• A Study of the Shortest-Period Planets Found With Kepler
• Minimum Core Masses for Giant Planet Formation With Realistic Equations of State and Opacities
• Understanding Jupiter's Interior
• Why is there a Dearth of Close-In Planets around Fast-Rotating stars?
• From Hot Jupiters to Super-Earths via Roche Lobe Overflow
• The Solar Twin Planet Search. V. Close-in, low-mass planet candidates and evidence of planet accretion in the solar twin HIP 68468
• A population of planetary systems characterized by short-period, Earth-sized planets
• Planets on the Edge
• Instability of mass transfer in a planet-star system
• A test of the high-eccentricity migration scenario for close-in planets

Cited by in corpus (4)

• Formation of Ultra-Short-Period Planets by Obliquity-Driven Tidal Runaway
• Mass determinations of the three mini-Neptunes transiting TOI-125
• A test of the high-eccentricity migration scenario for close-in planets
• Radius and mass distribution of ultra-short period planets