A binary merger origin for inflated hot Jupiter planets

TL;DR

This paper proposes that inflated hot Jupiters originate from the merger of two low-mass stars, linking their properties to stellar merger remnants and suggesting a distinct formation channel from traditional models.

Contribution

It introduces a novel formation scenario for inflated hot Jupiters via stellar mergers and correlates their inflation with merger-related properties and dynamics.

Findings

Inflated hot Jupiters' properties align with stellar merger progenitors.

Correlation between planet inflation and tidal spiral-in times.

Higher occurrence of inflated planets around blue stragglers.

Abstract

We hypothesize that hot Jupiters with inflated sizes represent a separate planet formation channel,the merging of two low-mass stars. We show that the abundance and properties of W UMa stars and low mass detached binaries are consistent with their being possible progenitors. The degree of inflation of the transiting hot Jupiters correlates with their expected spiral-in life time by tidal dissipation, and this could indicate youth if the stellar dissipation parameter Q'* is sufficiently low. Several Jupiter-mass planets can form in the massive compact disk formed in a merger event. Gravitational scattering between them can explain the high incidence of excentric, inclined, and retrograde orbits. If the population of inflated planets is indeed formed by a merger process, their frequency should be much higher around blue stragglers than around T Tauri stars.