Polarimetry of Be stars at 1.25 and 2.2 microns

Observations of the linear polarization of eight Be stars at 1.25 and 2.2 μm are presented. An equatorial disk model is developed where the polarization due to electron scattering of stellar and disk radiation is treated discretely, allowing two scatters of the stellar radiation and one of the disk radiation. Neutral hydrogen opacity is taken into account, and the populations of the levels of hydrogen are allowed depart from local thermodynamic equilibrium (LTE) if the dilute and diffuse fields indicate such a departure to be necessary. The stars phiPer, zetaTau, γCas, and EW Lac all show a decrease in polarization longward of 1 μm. When combined with polarlmetry in the visible, model calculations indicate an increase in the density of the disk toward the star for these stars. The stars 48 Lib, epsilonCap, and omicronAqr all maintain a high polarization into the near-infrared, and each requires a different disk structure when modeled. The excess emission longward of 1 μm for all of the stars can be shown to arise completely from within the disk