Eccentricity-orbital period diagram for planets with R_p = 1–3 R_⊕. Ross 176 b, HD 40307 b, and Wolf 503 b are overplotted in red, blue, and orange, respectively, following the same criteria as in Fig. 5. The precision of the eccentricities and the orbital periods of the planets is better than 70 and 10%, respectively. The vertical green line shows the period of 5 days, which is the upper limit for smaller planets to tend to maintain low eccentricities. On other hand, the vertical pink line shows the period of planets with non-neligible eccentricities (Correia et al. 2020).