The star chromatic index of a multigraph G, denoted χs′​(G), is the
minimum number of colors needed to properly color the edges of G such that no
path or cycle of length four is bi-colored. A multigraph G is star
k-edge-colorable if χs′​(G)≤k. Dvo\v{r}\'ak, Mohar and \v{S}\'amal
[Star chromatic index, J Graph Theory 72 (2013), 313--326] proved that every
subcubic multigraph is star 7-edge-colorable, and conjectured that every
subcubic multigraph should be star 6-edge-colorable. Kerdjoudj, Kostochka and
Raspaud considered the list version of this problem for simple graphs and
proved that every subcubic graph with maximum average degree less than 7/3 is
star list-5-edge-colorable. It is known that a graph with maximum average
degree 14/5 is not necessarily star 5-edge-colorable. In this paper, we
prove that every subcubic multigraph with maximum average degree less than
12/5 is star 5-edge-colorable.Comment: to appear in Discrete Mathematics. arXiv admin note: text overlap
with arXiv:1701.0410