Pure Spinor b-ghost in a Super-Maxwell Background

In the pure spinor formalism for the superstring, the b-ghost is a composite operator satisfying {Q,b}=T where Q is the pure spinor BRST operator and T is the holomorphic stress tensor. The b-ghost is holomorphic in a flat target-space background, but it is not holomorphic in a generic curved target-space background and instead satisfies $barpartial b$ = [Q, Omega] for some Omega. In this paper, Omega is explicitly constructed for the case of an open superstring in a super-Maxwell background.