As part of the survey component of the Megamaser Cosmology Project , we have discovered a disk megamaser system in the galaxy CGCG 074-064 .
Using the GBT and the VLA , we have obtained spectral monitoring observations of this maser system at a monthly cadence over the course of two years .
We find that the systemic maser features display line-of-sight accelerations of \sim 4.4 km s ^ { -1 } yr ^ { -1 } that are nearly constant with velocity , while the high-velocity maser features show accelerations that are consistent with zero .
We have also used the HSA to make a high-sensitivity VLBI map of the maser system in CGCG 074-064 , which reveals that the masers reside in a thin , edge-on disk with a diameter of \sim 1.5 mas ( 0.6 pc ) .
Fitting a three-dimensional warped disk model to the data , we measure a black hole mass of 2.42 ^ { +0.22 } _ { -0.20 } \times 10 ^ { 7 } M _ { \odot } and a geometric distance to the system of 87.6 ^ { +7.9 } _ { -7.2 } Mpc .
Assuming a CMB-frame recession velocity of 7308 \pm 150 km s ^ { -1 } , we constrain the Hubble constant to H _ { 0 } = 81.0 ^ { +7.4 } _ { -6.9 } ( stat . ) \pm 1.4 ( sys . )
km s ^ { -1 } Mpc ^ { -1 } .