Disk Truncation and Planet Formation in gamma Cephei

Abstract

The $\gamma$ Cephei system is one of the most closely bound binary planet hosts known to date. The companion ($\gamma$ Cep B) to the planet-hosting star ($\gamma$ Cep A) should have truncated any protoplanetary disk around $\gamma$ Cep A, possibly limiting planet formation in the disk. We explore this problem by calculating the truncation radii of protoplanetary disk models around $\gamma$ Cep A to determine whether or not there is sufficient material remaining in the disk to form a planet. We vary the accretion rate and viscosity parameter of the disk models to cover a range of reasonable possibilities for the disks properties and determine that for accretion rates of $\ge 10^{-7}$ M$_{\sun}$/yr and low viscosity parameter, sufficient material in gas and solids exist for planet formation via core accretion to be possible. Disk instability is less favored, as this can only occur in the most massive disk model with an extremely high accretion rate.

4 pages, 4 color figures. To appear in ApJL

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