The wavelength dependence of the circular and linear polarization of the magnetic white dwarf Grw + has been obtained with A resolution in the range 0.3-1.1 . There is no strong evidence for variability of either circular or linear polarization. The wavelength dependence of circular polarization is interpreted as being due to magnetic circular dichroism in a helium atmosphere. The mean longitudinal field strength estimated from both the circular polarization longward of 4000 A, which is due to He - opacity, and from the strong ultraviolet polarization feature, caused by the bound-free opacity of He , is 4-5 x 10 gauss. The linear polarization is probably due to a transverse field, estimated at 5 >c 10 to 106 gauss, again on the basis of He- opacity. New observations of the absorption feature at 5855 A are presented, and this is identified with the quadratically shifted component of the 5876 line of He originating in a lower field region of 1.5 x 10 gauss. Subject headings: magnetic stars - polarization - stars, individual - white dwarf stars
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Landstreet et al. (1975) studied this question.