Fig. 5
From: Orbital evolution of a circumbinary planet in a gaseous disk
Long-term evolution of the semi-major axis of a planet embedded at \(r_{\mathrm {cav}}\) for the \(e_{\mathrm {bin}}=0.05, \mu =0.2\) system. Planet orbit expands by accumulation of gravitational instability. Gas-drag avoids strong scattering and, with high \(f_{\mathrm {disk}}\), helps to keep the planet orbit close to the instability boundary