  Terrestrial planets have been found orbiting Sun-like stars with extremely
short periods --- some as short as 4 hours. These "ultra-short-period planets"
or "hot Earths" are so strongly irradiated that any initial H/He atmosphere has
probably been lost to photoevaporation. As such, the sample of hot Earths may
give us a glimpse at the rocky cores that are often enshrouded by thick H/He
envelopes on wider-orbiting planets. However, the mass and radius measurements
of hot Earths have been derived from a hodgepodge of different modeling
approaches, and include several cases of contradictory results. Here, we
perform a homogeneous analysis of the complete sample of 11 known hot Earths
with an insolation exceeding 650 times that of the Earth. We combine all
available data for each planet, incorporate parallax information from {\it
Gaia} to improve the stellar and planetary parameters, and use Gaussian Process
regression to account for correlated noise in the radial-velocity data. The
homogeneous analysis leads to a smaller dispersion in the apparent composition
of hot Earths, although there does still appear to be some intrinsic
dispersion. Most of the planets are consistent with an Earth-like composition
(35\% iron and 65\% rock), but two planets (K2-141b and K2-229b) show evidence
for a higher iron fraction, and one planet (55\,Cnc\,e) has either a very low
iron fraction or an envelope of low-density volatiles. All of the planets are
less massive than 8\,$M_\oplus$, despite the selection bias towards more
massive planets, suggesting that 8\,$M_\oplus$ is the critical mass for runaway
accretion.
