HD 202206: A Circumbinary Brown Dwarf System

Using 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, {π }_{abs}=21.96+/- 0.12 milliseconds of arc, a mass for HD 202206 B of {{ M }}_B={0.089}_-0.006^+0.007 {{ M }}_⊙ , and a mass for HD 202206 c of {{ M }}_c={17.9}_-1.8^+2.9 {{ M }}_{Jup}. HD 202206 is a nearly face-on G + M binary orbited by a brown dwarf. The system architecture that 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+/- 0.04) and coplanarity (we find a mutual inclination, {{Φ }}=6^\circ +/- 2^\circ ).

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.