  Radial velocity (RV) surveys have discovered hundreds of exoplanetary systems
but suffer from a fundamental degeneracy between planet mass $M_p$ and orbital
inclination $i$. In this paper we break this degeneracy by combining RVs with
complementary absolute astrometry taken from the Gaia EDR3 version of the
cross-calibrated Hipparcos-Gaia Catalog of Accelerations (HGCA). We use the
Markov Chain Monte Carlo orbit code $\tt orvara$ to simultaneously fit
literature RVs and absolute astrometry from the HGCA. We constrain the orbits,
masses, and inclinations of nine single and massive RV companions orbiting
nearby G and K stars. We confirm the planetary nature of six companions: HD
29021 b ($4.47_{-0.65}^{+0.67}\,M_{\rm Jup}$), HD 81040 b
($7.24_{-0.37}^{+1.0}\,M_{\rm Jup}$), HD 87883 b ($6.31_{-0.32}^{+0.31}\,M_{\rm
Jup}$), HD 98649 b ($9.7_{-1.9}^{+2.3}\,M_{\rm Jup}$), HD 106252 b
($10.00_{-0.73}^{+0.78}\,M_{\rm Jup}$), and HD 171238 b
($8.8_{-1.3}^{+3.6}\,M_{\rm Jup}$). We place one companion, HD 196067 b
($12.5_{-1.8}^{+2.5}\,M_{\rm Jup}$) on the planet-brown dwarf boundary, and two
companions in the low mass brown dwarf regime: HD 106515 Ab
($18.9_{-1.4}^{+1.5}\,M_{\rm Jup}$), and HD 221420 b
(${20.6}_{-1.6}^{+2.0}\,M_{\rm Jup}$). The brown dwarf HD 221420 b, with a
semi-major axis of ${9.99}_{-0.70}^{+0.74}$ AU, a period of
${27.7}_{-2.5}^{+3.0}$ years, and an eccentricity of $0.162_{-0.030}^{+0.035}$
represents a promising target for high-contrast imaging. The RV orbits of HD
87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet
because of insufficient RV data. We find two possible inclinations for each of
these orbits due to difficulty in separating prograde from retrograde orbits,
but we expect this will change decisively with future Gaia data releases.
