Formation of circumbinary planets in a dead zone

TL;DR

This paper explores how layered circumbinary disks with dead zones influence planet formation, suggesting that planets are more likely to form near the snow line within dead zones, especially around close binaries.

Contribution

It introduces the concept that dead zones in circumbinary disks significantly affect planet formation, highlighting a potential planet trap near the snow line in close binary systems.

Findings

Dead zones extend up to 10-20 au in close binaries.

Surface density peaks near the snow line within dead zones.

Planet formation is more favorable near the snow line in close binaries.

Abstract

Circumbinary planets have been observed at orbital radii where binary perturbations may have significant effects on the gas disk structure, on planetesimal velocity dispersion, and on the coupling between turbulence and planetesimals. Here, we note that the impact of all of these effects on planet formation is qualitatively altered if the circumbinary disk structure is layered, with a non-turbulent midplane layer (dead zone) and strongly turbulent surface layers. For close binaries, we find that the dead zone typically extends from a radius close to the inner disk edge up to a radius of around 10-20 au from the centre of mass of the binary. The peak in the surface density occurs within the dead zone, far from the inner disk edge, close to the snow line, and may act as a trap for aerodynamically coupled solids. We suggest that circumbinary planet formation may be easier near this preferential location than for disks around single stars. However, dead zones around wide binaries are less likely and hence planet formation may be more difficult there.