Free-Free Gaunt factors for atmospheres of accreting pulsars observable with X-ray space missions

Free-Free Gaunt factors for X-ray absorption by hot plasma in the presence of a strong magnetic field are reported. Modified formulae are used for application to the non-local thermodynamic equilibrium conditions found in accreting pulsar atmospheres. Given upcoming global X-ray polarimetric space missions, these can be used for the construction of an absorption matrix in discrete-ordinate polarised radiative transfer.