Broad-Band Molecular Polarization in White Dwarfs

We present novel calculations of broad-band polarization due to the molecular Paschen–Back effect in a strong magnetic field. Based on that, we analyze new spectropolarimetric observations of the cool magnetic helium-rich white dwarf G 99−37 which shows strongly polarized molecular bands in its spectrum. Combining the polarimetric observations with our model calculations for the CH bands at 4300 A, we deduce a magnetic field of 8MG on this unique magnetic white dwarf.