On the theory of astronomical maser. II. Polarization of maser radiation

In this paper we investigate the polarization property of the radiation amplified by astronomical masers in the presence of a strong magnetic field. Our model explicitly takes into account the broadband nature of the radiation field and the interaction of the radiation with the maser transition J=1--0. The amplification of different realisations of the background continuum radition by the maser is directly simulated and the Stokes parameters of the radiation field are then obtained by averaging over the ensemble of emerging maser radiation. For isotropic pumping and partially saturated masers we find that the maser radiation is linearly polarized in two representative cases where the magnetic field {\bf B} makes an angle $θ$=30$^0$ and $θ$=90$^0$ to the maser axis. The linear polarization for maser radiation obtained in our simulations for both cases are in agreement with the results of the standard model. Furthermore, no instability during amplification is seen in our simulations. Therefore, we conclude that there is no problem with the previous numerical investigations of maser polarization in the unsaturated and partially saturated regime.