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Spectrographic measurements of the magnetic white dwarf GC 356 are presented, and, two weak emission line Zeeman triplets at H-alpha and H-beta are analyzed. The measurements were carried out using a high signal-to-noise ratio double spectrograph and CCD detectors attached to the Hale 5 meter refector telescope. Multichannel spectrophotometry of GD 356 indicated a temperature of about 7500 K. The H-alpha absorption triplet in G99-47 was studied, in order to correct emission measurements in GD 356. After scaling the absorption lines in G99 47 to fit the field in GD 356, the corrected H-alpha emission increased by 50 percent. The final H-alpha profile is represented by random fields of 11.0 megagauss with a spread of 1.1 megagauss. On the basis of the emission line analysis, some possible reasons for the absence of polarization in GD are discussed, including: (1) that GD 356 has an interacting companion; (2) that active convection in GD 356 interacts with the magnetic field to produce magnetoionic heating; and (3) that there is an ongoing accretion of interstellar matter in GD 356. It is suggested that GD 356 may be detectable with the IUE ultraviolet observatory.
Greenstein et al. (Fri,) studied this question.