Possible formation pathways for the low density Neptune-mass planet HAT-P-26b
Ali-Dib et al
We investigate possible pathways for the formation of the low density Neptune-mass planet HAT-P-26b. We use two formation different models based on pebbles and planetesimals accretion, and includes gas accretion, disk migration and simple photoevaporation. The models tracks the oxygen abundance and the properties of the forming planets, that we compare to HAT-P-26b. We find that pebbles accretion can explain this planet more naturally than planetesimals accretion that fails completely unless we artificially enhance the disk metallicity significantly. Pebble accretion models can reproduce HAT-P-26b with either a high initial core mass and low amount of core erosion, or the opposite, with both scenarios being equally plausible. Degeneracy between the formation time and location of the planet implies that more observables are needed to constraint its formation.