Well-edge-dominated graphs containing triangles

Abstract

A set of edges $F$ in a graph $G$ is an edge dominating set if every edge in $G$ is either in $F$ or shares a vertex with an edge in $F$. $G$ is said to be well-edge-dominated if all of its minimal edge dominating sets have the same cardinality. Recently it was shown that any triangle-free well-edge-dominated graph is either bipartite or in the set $\{C_5, C_7, C_7^*\}$ where $C_7^*$ is obtained from $C_7$ by adding a chord between any pair of vertices distance three apart. In this paper, we completely characterize all well-edge-dominated graphs containing exactly one triangle, of which there are two infinite families. We also prove that there are only eight well-edge-dominated outerplanar graphs, most of which contain at most one triangle.