Type IIA dual of the six-dimensional CHL compactification

We propose a candidate for the dual (in the weak/strong coupling sense) of the six-dimensional heterotic string compactification constructed recently by Chaudhuri, Hockney and Lykken. It is a type IIA string theory compactified on an orbifold K3Z2, where the Z2 action involuution of K3 with fixed points, and also has an embedding in the U(1) gauge group associated with the Ramond-Ramond sector of the type IIA string theory. This introduces flux of the U(1) gauge field concentrated at the orbifold points. This construction provides and explicit example where the dual of a super-conformal field theory background of the heterotic string theory is not a standard super-conformal field theory background of the type IIA string theory.