The Minimum Gap-opening Planet Mass in an Irradiated Circumstellar Accretion Disk

TL;DR

This paper estimates the minimum mass a planet must have to open a gap in an irradiated accretion disk, considering various disk parameters, and discusses implications for planet migration and disk clearing.

Contribution

It provides a quantitative estimate of the minimum gap-opening planet mass as a function of disk and stellar parameters, extending previous models to irradiated disks.

Findings

A half Jupiter mass planet can open a gap in low accretion rate disks.

Minimum planet mass scales with accretion rate, viscosity, stellar mass, and luminosity.

Identifies key radii where gap opening affects planet migration and disk clearing.

Abstract

We consider the minimum mass planet, as a function of radius, that is capable of opening a gap in an $\alpha$-accretion disk. We estimate that a half Jupiter mass planet can open a gap in a disk with accretion rate $\dot M \la 10^{-8} M_\odot$/yr for viscosity parameter $\alpha =0.01$, and Solar mass and luminosity. The minimum mass is approximately proportional to $\dot M^{0.48} \alpha^{0.8} M_*^{0.42} L_*^{-0.08}$. This estimate can be used to rule out the presence of massive planets in gapless accretion disks. We identify two radii at which an inwardly migrating planet may become able to open a gap and so slow its migration; the radius at which the heating from viscous dissipation is similar to that from stellar radiation in a flared disk, and the radius at which the disk has optical depth order 1 in a self-shadowed disk. If a gap opening planet cuts off disk accretion allowing the formation of a central hole or clearing in the disk then we would estimate that the clearing radius would approximately be proportional to the stellar mass.