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THE ULTRAVIOLET SPECTRUM OF THE MAGNETIC DEGENERATE STAR GD229
RICHARD F. GREEN and JAMES LIEBERT
Publications of the Astronomical Society of the Pacific
Vol. 93, No. 551 (February 1981), pp. 105-109
Published by: Astronomical Society of the Pacific
Stable URL: http://www.jstor.org/stable/40677839
Page Count: 5
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Ultraviolet spectrophotometry from IUE of the magnetic degenerate star GD229 is presented. The ultraviolet energy distribution when combined with optical data requires a best fit blackbody temperature of 16,000 K, significantly lower than previous estimates. A broad absorption trough in the 2000 Å-3000 Å region may be produced by opacity in the fundamental cyclotron frequency for surface magnetic fields ranging from 3.6 to 5.4 x 10ɸ gauss. This interpretation is consistent with estimates from the rotation of the position angle of linear polarization below 4000 Å. The absence of a strong La₊ σ⁺ component argues that the primary atmospheric constituent is not hydrogen. Strong absorptions at 2800 Å and 1700 Å and other weaker features similar in character to those observed at optical wavelengths are probably attributable to unidentified Zeeman components of neutral helium, with Mg ıı, Ca ıı, C ıı and other metal line opacities to be considered. A superposition of many strong Zeeman features in the 2000 Å-3000 Å interval at a surface field strength > 10ɸ gauss is an alternative to the cyclotron interpretation.
Publications of the Astronomical Society of the Pacific © 1981 The University of Chicago Press