Photon emissivity of the electrosphere of bare strange stars
  We consider the spectrum, emissivity and flux of the electromagnetic radiation emitted by the thin electron layer (the electrosphere) at the surface of a bare strange star. In particular, we carefully consider the effect of the multiple and uncorrelated scattering on the radiation spectrum (the Landau-Pomeranchuk-Migdal effect), together with the effect of the strong electric field at the surface of the star. The presence of the electric field strongly influences the radiation spectrum emitted by the electrosphere. All the radiation properties of the electrons in the electrosphere essentially depend on the value of the electric potential at the quark star surface. The effect of the multiple scattering, which strongly suppresses radiation emission, is important only for the dense layer of the electrosphere situated near the star's surface and only for high values of the surface electric potential of the star. Hence a typical bremsstrahlung radiation spectrum, which could extend to very low frequencies, could be one of the main observational signatures even for low temperature quark stars. 
T. Harko, K. S. Cheng