LAUSR

The aim of the present work is twofold: first, we present general remarks about a recent procedure to compute the deflection angle taking into account finite distance corrections based on the Gauss-Bonnet theorem. Second, we apply this powerful technique to compute corrections to the deflection angle produced by astrophysical configurations in the weak gravitational regime when a plasma medium is taken into account. For applications, we apply this machinery to introduce new general formulas for the bending angle of light rays in plasma environments in different astrophysical scenarios, generalizing previously discovered results. In particular, for the case of a homogeneous plasma we study these corrections for the case of light rays propagating near astrophysical objects described in the weak gravitational regime by a Parametrized-Post-Newtonian (PPN) metric which takes into account the mass of the objects and a possible quadrupole moment. Even when our work concentrates in finite distances corrections to the deflection angle, we also obtain as particular cases of our expressions new formulas which are valid for the more common assumption of infinite distance between receiver, lens, and source. We also consider the presence of an inhomogeneous plasma media introducing as particular cases of our general formulas explicit expressions for particular charge number density profiles.