On the relation between Hot-Jupiters and the Roche Limit
  Many of the known extrasolar planets are ``hot Jupiters,'' giant planets with orbital periods of just a few days. We use the observed distribution of hot Jupiters to constrain the location of the ``inner edge'' and planet migration theory. If we assume the location of the inner edge is proportional to the Roche limit, then we find that this edge is located near twice the Roche limit, as expected if the planets were circularized from a highly eccentric orbit. If confirmed, this result would place significant limits on migration via slow inspiral. However, if we relax our assumption for the slope of the inner edge, then the current sample of hot Jupiters is not sufficient to provide a precise constraint on both the location and power law index of the inner edge. 
Eric B. Ford & Frederic A. Rasio