A Keplerian disk around Orion Source I, a ~15 Msun YSO
  We report ALMA long-baseline observations of Orion Source I (SrcI) with
resolution 0.03-0.06" (12-24 AU) at 1.3 and 3.2 mm. We detect both continuum
and spectral line emission from SrcI's disk. We also detect a central weakly
resolved source that we interpret as a hot spot in the inner disk, which may
indicate the presence of a binary system. The high angular resolution and
sensitivity of these observations allow us to measure the outer envelope of the
rotation curve of the H$_2$O $5_{5,0}-6_{4,3}$ line, which gives a mass
$M_I\approx15\pm2$ Msun. We detected several other lines that more closely
trace the disk, but were unable to identify their parent species. Using
centroid-of-channel methods on these other lines, we infer a similar mass.
These measurements solidify SrcI as a genuine high-mass protostar system and
support the theory that SrcI and the Becklin Neugebauer Object were ejected
from the dynamical decay of a multiple star system $\sim$500 years ago, an
event that also launched the explosive molecular outflow in Orion.
