Investigating the Origins of Hot Neptunes from Radial Velocity Data

Abstract

Abstract Hot Neptunes are extrasolar planets that are similar in size to Neptune in our solar system but are much closer to their host stars, completing an orbit in 10 days or less. The origin of hot Neptunes is not fully understood. A potential large third body at a distance can lead to the migration of long-period planets to become much closer to the host star, and such a dynamical process helps explain the origin of hot Jupiters. We investigate whether hot Neptunes could share a similar origin by analyzing radial velocity data from multiple sources for a sample of 34 hot Neptune systems. Hot Neptune systems appear to have similar values of linear trend to hot Jupiter systems. We perform a maximum likelihood analysis to constrain the mass and distance distribution of the putative third body. The overall fraction of hot Neptune systems with third bodies is consistent with unity, higher than 71% at the 2σ level. On average, the mass and distance distribution of the third bodies for hot Neptune systems is consistent with that for hot Jupiter systems. Our results suggest that hot-Neptune systems share the same origin mechanism as hot Jupiters, e.g., through the gravitational effect of third bodies.