One parameter family of indecomposable optimal entanglement witnesses arising from generalized Choi maps

In the recent paper [Chru'{s}ci'{n}ski and Wudarski, arXiv:1105.4821], it was conjectured that the entanglement witnesses arising from some generalized Choi maps are optimal. We show that this conjecture is true. Furthermore, we show that they provide a one parameter family of indecomposable optimal entanglement witnesses.