November 1987 • 1987ApJ...322L..35W
Abstract • BG CMi is the only intermediate polar known to be magnetic. New observations reported here reveal that its wavelength dependence of circular polarization increases rapidly into the infrared, from VI= -0.25%±0.06% in the optical red to VJ= -1.74%±0.26% (1.25 μm). This dramatic rise, which may even continue to a level of -4% at H (1.5 μm), is the first conclusive identification of cyclotron emission in an intermediate polar, and confirms that the long-held basic model of a magnetic accreting white dwarf is correct. The field in the cyclotron emission region of BG CMi is likely in the range ≡5 - 10 MG.
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