A pair of planets around HD 202206 or a circumbinary planet?

TL;DR

Precise Doppler measurements reveal a complex two-planet system around HD 202206, featuring a possible brown dwarf and a Jupiter-like planet in resonance, offering insights into planetary formation and migration.

Contribution

Discovery and detailed analysis of a unique two-planet system with a potential brown dwarf and a Jupiter-like planet, highlighting formation scenarios.

Findings

Inner companion near brown-dwarf mass limit

Outer companion is a Jupiter-like planet

Planets are in a 5/1 mean motion resonance

Abstract

Long-term precise Doppler measurements with the CORALIE spectrograph reveal the presence of a second planet orbiting the solar-type star HD202206. The radial-velocity combined fit yields companion masses of m_2\sini = 17.4 M_Jup and 2.44 M_Jup, semi-major axes of a = 0.83 AU and 2.55 AU, and eccentricities of e = 0.43 and 0.27, respectively. A dynamical analysis of the system further shows a 5/1 mean motion resonance between the two planets. This system is of particular interest since the inner planet is within the brown-dwarf limits while the outer one is much less massive. Therefore, either the inner planet formed simultaneously in the protoplanetary disk as a superplanet, or the outer Jupiter-like planet formed in a circumbinary disk. We believe this singular planetary system will provide important constraints on planetary formation and migration scenarios.