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tokens: the acceleration of the star induced by the companion. We augment the internal RV uncertainties listed in Table 2 with a “jitter” term that is added in quadrature to accommodate the expected level of noise introduced from stellar variability. HD 169889 A has a visual color of B − V = 0.75 and median activity index of S HK = 0.18. We assume a B − V uncertainty of 0.01 mags. Using empirical relations from Isaacson Fischer ( 2010 ), we estimate a jitter value of σ = 2.2 ± 0.1 m s −1 . Table 2 Relative Stellar RV Measurements for HD 169889 Note. A horizontal line denotes the division between data sets when the HIRES detector was upgraded (2004 August) requiring a relative RV offset for analysis. Table 3 Summary of High-contrast Imaging Observations Showing the Number of Coadds ( n coadds ), Frames ( N fr ), Exposure Time per Frame (Δ t exp ), and Change in Parallactic Angle Δ π (°) Table 4 Summary of Astrometry Measurements Note. Position angle (PA) measurements are referenced with respect to the equator of the observing epoch. Table 5 Photometric Results and Companion Properties A straight line is fit using Markov Chain Monte Carlo (MCMC) methods to find a best-fitting RV slope of m s −1 yr −1 . Combined with the direct imaging projected separation, we use the relation from Liu et al. ( 2002 ) to derive a lower limit to the companion mass of m min = 0.369 ± 0.010 M ⊙ (Table 5 ). Clearly, HD 169889 B cannot be a brown dwarf but is instead a compact object provided the acceleration is attributable to this object. A more careful treatment would consider the slight curvature noticeable by eye in the RV time series as well as astrometry (Figure 1 ). However, only a small fraction of the companion orbit has been traced in either data set. Further, the astrometry measurements were obtained with two different instruments using three different filters. The systematics that result from combining these observations can be noticed in the zoomed-in portion of Figure 5 at the ≈1 σ level (10 mas). The WD companion appears to be moving to the north, i.e., closer to HD 169889 A, but further AO imaging is required to confirm. Figure 5. Proper motion and parallactic motion analysis taking into account the path that an infinitely distant background object would traverse is compared to the separation of HD 169889 B over time. Angular offsets are measured relative to the optical primary star. The inset shows a zoomed-in view of individual astrometric measurements. The companion shares the same space motion demonstrating that they are gravitationally associated. 5. WD Properties Empirical relations between WD masses and their progenitors have been established based on the study of open clusters, globular clusters, and common proper motion pairs (Weidemann 2000 ; Williams et al. 2009 ). Using the dynamical mass lower limit from RVs and imaging, we attempt to place a lower limit on the companion progenitor mass ( M i ) by inverting the empirical relationship from