Astrophysical aspects of milli-charged dark matter in a   Higgs-Stueckelberg model
  An extension of the Standard Model is studied, in which two new vector bosons are introduced, a first boson $Z'$ coupled to the SM by the usual minimal coupling, producing an enlarged gauge sector in the SM. The second boson $A'$ field, in the dark sector of the model, remains massless and originates a dark photon $\gamma'$. A hybrid mixing scenario is considered based on a combined Higgs and Stueckelberg mechanisms. In a Compton-like process a photon scattered by a WIMP is converted into a dark photon. This process is studied, in an astrophysical application obtaining an estimate of the impact on stellar cooling of white dwarfs and neutron stars. 
A. L. dos Santos, D. Hadjimichef
hep-ph