On minimal rational elliptic surfaces

We construct $13$ projective $\mathbb{Q}$-factorial Fano toric varieties and show that for any minimal rational elliptic surface $X$ there is one such toric variety $Z_X$ and a divisor class $\delta_X\in {\rm Cl}(Z_X)$ such that the number of $(-1)$-curves of $X$ equals the dimension of the Riemann-Roch space of $\delta_X$. As an application we give the number of $(-1)$-curves of any such elliptic fibration of Halphen index $2$.