The Imprint of the Protoplanetary Disk in the Accretion of Super-Earth Envelopes

Super-Earths are by far the most dominant type of exoplanet, yet their formation is still not well understood. In particular, planet formation models predict that many of them should have accreted enough gas to become gas giants. I will be discussing the role of the protoplanetary disk in the coolingand contraction of the protoplanetary envelope. In particular, the following two effects are considered: 1) the thermal state of the disk as set by the relative size of heating by accretion or irradiation, and whether its energy is transported by radiation or convection. 2) advection of entropy into the outer envelope by disk flows that penetrate the Hill sphere. We find that, at 0.1 AU, the envelope quickly becomes fully-radiative, nearly isothermal, and thus cannot cool down, stalling gas accretion. This effect is significantly more pronounced in convective disks, leading to envelope mass orders of magnitude lower. Entropy advection at 0.1 AU in either radiative or convective disks could therefore explain why super-Earths failed to undergo runaway accretion. References: Ali-Dib, Cumming, & Lin 2020 (MNRAS). arXiv:2003.01644