Hot Super Earths: Disrupted young jupiters?

Recent Kepler observations revealed an abundance of ‘hot’ Earth-size to Neptune-size planets in the inner 0.02–0.2 au from their parent stars. We propose that at least some of these smaller planets are the remnants of massive giant planets that migrated inwards quicker than they could contract. We show that such disruptions occur if the young giant planet embryo is initially extended. The characteristic planet–star separation at which such ‘hot disruptions’ occur is R≈ 0.03–0.2 au. The disruption is most likely at high accretion rates, Graphic yr−1, when the migration is rapid and the embryo is unable to contract quickly enough. At late times, when the accretion rate drops to Graphic yr−1, the embryos migrate sufficiently slow to be not disrupted. These ‘late arrivals’ may explain the well-known population of hot jupiters, although they could also be accounted for by the more compact giant planets in the framework of the core accretion scenario for planet formation.