Explaining Neptune's Eccentricity

Early migration damped Neptune’s eccentricity. Here, we assume that the damped value was much smaller than the value observed today, and show that the closest flyby of $\sim 0.1{\mathrm{M}}_{\odot }$ star over $\sim 4.5 $\mathrm{G}\mathrm{y}\mathrm{r}$$inthefield,atadistanceof$\sim 10^3 $\mathrm{A}\mathrm{U}$$ would explain the value of Neptune’s eccentricity observed today.