# HD 202206 : A Circumbinary Brown Dwarf System

## TL;DR

This study uses Hubble astrometry and radial velocity data to characterize the HD 202206 system, revealing a nearly face-on binary with a brown dwarf companion in a stable, coplanar 5:1 resonance.

## Contribution

The paper provides the first combined astrometric and radial velocity analysis of HD 202206, confirming the system's architecture and resonance stability.

## Key findings

- Mass of HD 202206 B is approximately 0.089 solar masses.
- The brown dwarf HD 202206 c has a mass around 17.9 Jupiter masses.
- The system exhibits a 5:1 mean motion resonance and coplanarity.

## Abstract

With Hubble Space Telescope Fine Guidance Sensor astrometry and previously published radial velocity measures we explore the exoplanetary system HD 202206. Our modeling results in a parallax, $\pi_{abs} = 21.96\pm0.12$ milliseconds of arc, a mass for HD 202206 B of M$_B = 0.089^{ +0.007}_{-0.006}$ Msun, and a mass for HD 202206 c of M$_c = 17.9 ^{ +2.9}_{-1.8}$ MJup. HD 202206 is a nearly face-on G+M binary orbited by a brown dwarf. The system architecture we determine supports past assertions that stability requires a 5:1 mean motion resonance (we find a period ratio, $P_c/P_B = 4.92\pm0.04$) and coplanarity (we find a mutual inclination, Phi = 6 \arcdeg \pm 2 \arcdeg).