Abstract

Massive planets in close orbits around their host stars undergo tidal orbit decay at a rate that increases with planet mass and proximity to the host star. The upper left-hand corner of the hot-Jupiter mass-separation diagram is visibly depleted as a result. By modelling the underlying population it’s possible to calibrate the strength of the tidal interaction from the location of the boundary. The model has some curious features. The probability of seeing a planet today depends on how much its migration has sped up since birth, as well as the probability density for its birth location. Batches of planets formed recently at a given location haven’t yet been spread out by the accelerating flow, whereas older batches from further upstream have a more thinly-spread probability density. I’ll show how this explains some curious features of the hot-Jupiter population and their host stars.