The companion to the G0V star HR7672 directly imaged by has moved measurably along its orbit since the discovery epoch , making it possible to determine its dynamical properties .
Originally targeted with adaptive optics because it showed a long-term radial velocity acceleration ( trend ) , we have monitored this star with precise Doppler measurements and have now established a 24 year time baseline .
The radial velocity variations show significant curvature ( change in the acceleration ) including an inflection point .
We have also obtained a recent image of HR7672B with NIRC2 at Keck .
The astrometry also shows curvature .
In this paper , we use jointly-fitted Doppler and astrometric models to calculate the three-dimensional orbit and dynamical mass of the companion .
The mass of the host star is determined using a direct radius measurement from CHARA interferometry in combination with high resolution spectroscopic modeling .
We find that HR7672B has a highly eccentric , e = 0.50 ^ { +0.01 } _ { -0.01 } , near edge-on , i = 97.3 ^ { +0.4 } _ { -0.5 } deg , orbit with semimajor axis , a = 18.3 ^ { +0.4 } _ { -0.5 } AU .
The mass of the companion is m = 68.7 ^ { +2.4 } _ { -3.1 } M _ { J } at the 68.2 % confidence level .
HR7672B thus resides near the substellar boundary , just below the hydrogen-fusing limit .
These measurements of the companion mass are independent of its brightness and spectrum and establish HR7672B as a rare and precious “ benchmark ” brown dwarf with a well-determined mass , age , and metallicity essential for testing theoretical evolutionary models and synthetic spectral models .
It is presently the only directly imaged L , T , Y-dwarf known to produce an RV trend around a solar-type star .