  The close proximity of short period hot-Jupiters to their parent star means
they are subject to extreme tidal forces. This has a profound effect on their
structure and, as a result, density measurements that assume that the planet is
spherical can be incorrect. We have simulated the tidally distorted surface for
34 known short period hot-Jupiters, assuming surfaces of constant gravitational
equipotential for the planet, and the resulting densities have been calculated
based only on observed parameters of the exoplanet systems. Comparing these
results to the density values assuming the planets are spherical shows that
there is an appreciable change in the measured density for planets with very
short periods (typically less than two days). For one of the shortest-period
systems, WASP-19b, we determine a decrease in bulk density of 12% from the
spherical case and, for the majority of systems in this study, this value is in
the range of 1-5%. On the other-hand, we also find cases where the distortion
is negligible (relative to the measurement errors on the planetary parameters)
even in the cases of some very short period systems, depending on the mass
ratio and planetary radius. For high-density gas-planets requiring apparently
anomalously large core masses, density corrections due to tidal deformation
could become important for the shortest-period systems.
