Proposed geometry for soft state of NS-LMXBs; the disk extends very close to the NS surface, and then a BL forms with ΔR ≪ R_ns. The BB photons from the NS photosphere are located at the base of the BL, which extends up to some latitude θ^max computed from the orbital plane, and has a given temperature kT_e and radial optical depth 2τ₀. Only photons in the northern hemisphere (θ <  π/2) reach the observer. The total signal is obtained by integrating the contribution from each elementary area dΣ′ shown by the blue box over the BL surface.