From Warm Planets to Perpendicular Hot Planets

Abstract

High eccentricity tidal migration (HEM) is a promising channel for the origins of hot Jupiters and hot Neptunes. In the typical HEM scenario, a planet forms beyond the ice line, but alternatively a planet can disk migrate or form warm and undergo a short final stretch of HEM. At the warm origin point, general relavistic precession can reduce the amplitude of Kozai-Lidov oscillations driven by an outer companion. We show that warm planets that achieve HEM under these conditions -- and with common types of planetary and stellar companions -- tend to end up with near-polar spin-orbit alignments (psi = 50-130 degrees) instead of concentrated at 40 and 140 degrees. Thus short distance, GR-reduced HEM is a possible explanation for the observed population of perpendicular planets.