Possible location of an additional fourth planet in the GJ 163 system. The stability of an Earth-size planet (K = 0.2 m/s) is analyzed, for various semi-major axis versus eccentricity (top), or mean anomaly (bottom). All the angles of the putative planet are set to 0° (except the mean anomaly in the bottom panel), and in the bottom panel, its eccentricity to 0. The stable zones where additional planets can be found are the dark blue regions.