$\delta$-invariants of log Fano planes

We compute the $\delta$-invariant for pairs $({\mathbb{P}}^2,\lambda C_d)$, where $C_d$ is a plane curve of degree $d\le 4$. These computations provide new examples of $K$-stable and $K$-semistable log Fano pairs, and contribute to the study of $K$-stability of log Fano varieties via the Abban-Zhuang method, which reduces higher-dimensional problems to the surface case.