Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-09T06:40:02.042Z Has data issue: false hasContentIssue false
  • English
  • Français

Continuum Polarization in Magnetic White Dwarfs∗

Published online by Cambridge University Press:  14 August 2015

F. K. Lamb  and
P. G. Sutherland
F. K. Lamb
Affiliation:
Dept. of Physics, University of Illinois, Urbana, Ill. 61801, U.S.A.
P. G. Sutherland
Affiliation:
Dept. of Physics, Columbia University, New York, N.Y. 10027, U.S.A.

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We discuss some of the effects which magnetic fields in the range 104–108 G have on the continuum emission of white dwarfs. In order to show how atomic processes are related to the transport of radiation in an anisotropic medium we introduce the radiative transfer equation for polarized light. Using this transfer equation as a guide we develop a greatly simplified model of a white dwarf atmosphere: anisotropic absorption of unpolarized light passing through a cold, optically-thin layer. Two possible sources of continuum polarization in white dwarfs with strong magnetic fields are explored, namely bound-free transitions and cyclotron absorption. Within the hydrogenic approximation we develop a further approximation which is valid for bound-free transitions when B is in the range 104–107 G. Using this approximation it is possible to obtain simple expressions for the net circular and linear polarization in terms of the zero-field opacity. In the case of cyclotron absorption, the cross section is large and strongly peaked at the cyclotron frequency, which falls in the infrared or optical for B ⩾ 108 G. This process can lead to net circular and linear polarization of comparable magnitude. For stars with non-uniform magnetic fields, the cyclotron absorption effects are spread over considerable wavelength ranges, with possibly quite complicated wavelength-dependent polarization.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 53: Physics of Dense Matter , 1974 , pp. 265 - 285
Copyright
Copyright © Reidel 1974 

References

Angel, J. R. P.: 1972, Astrophys. J. Letters 171, L17.Google Scholar
Angel, J. R. P. and Landstreet, J. D.: 1970a, Astrophys. J. Letters 160, L147.Google Scholar
Angel, J. R. P. and Landstreet, J. D.: 1970b, Astrophys. J. Letters 162, L61.Google Scholar
Angel, J. R. P. and Landstreet, J. D.: 1971a, Astrophys. J. Letters 164, L15.Google Scholar
Angel, J. R. P. and Landstreet, J. D.: 1971b, Astrophys. J. Letters 165, L71.Google Scholar
Angel, J. R. P. and Landstreet, J. D.: 1972, Astrophys. J. Letters, 178, L21.Google Scholar
Angel, J. R. P., Illing, R. M. E., and Landstreet, J. D.: 1972a, Astrophys. J. Letters 175, L85.Google Scholar
Angel, J. R. P., Landstreet, J. D., and Oke, J. B.: 1972b, Astrophys. J. Letters 171, L11.CrossRefGoogle Scholar
Chandrasekhar, S.: 1960, Radiative Transfer, Dover, New York, p. 24ff.Google Scholar
Chanmugam, G., O'Connell, R. F., and Rajagopal, A. K.: 1972, Astrophys. J. 175, 157.CrossRefGoogle Scholar
Chow, T. L.: 1969, Astrophys. Letters 3, 85.Google Scholar
Frank-Kamenetskii, D. A.: 1962, Physical Processes in Stellar Interiors (translated from the Russian and published for the National Science Foundation by the Israel Program for Scientific Translations), p. 144.Google Scholar
Gehrels, T.: 1971 (unpublished).Google Scholar
Ginzburg, V. L., Zheleznyakov, V. V., and Zaitsev, V. V.: 1969, Astrophys. Space Sci. 4, 464.Google Scholar
Greenstein, J. L.: 1970, Astrophys. J. Letters 162, L55.Google Scholar
Greenstein, J. L., Gunn, J. E., and Kristian, J.: 1971, Astrophys. J. Letters 169, L63.CrossRefGoogle Scholar
Greenstein, J. L. and Matthews, M. S.: 1957, Astrophys. J. 126, 14.Google Scholar
Kemp, J. C.: 1970a, Astrophys. J. Letters 162, L69.Google Scholar
Kemp, J. C.: 1970b, Astrophys. J. 162, 169.Google Scholar
Kemp, J. C. and Swedlund, J. B.: 1970, Astrophys. J. Letters 162, L67.Google Scholar
Kemp, J. C., Swedlund, J. B., Landstreet, J. D., and Angel, J. R. P.: 1970, Astrophys. J. Letters 161, L77.Google Scholar
Kemp, J. C., Swedlund, J. B., and Wolstencroft, R. D.: 1971, Astrophys. J. Letters 164, L17.Google Scholar
Lamb, F. K. and ter Haar, D.: 1970, Oxford University, Department of Theoretical Physics, Reference No. 38/70.Google Scholar
Lamb, F. K. and Sutherland, P. G.: 1971, paper presented at the Conference on Line Formation in the Presence of Magnetic Fields, 30 August–2 September 1971, High Altitude Observatory, Boulder, Colorado.Google Scholar
Landstreet, J. D. and Angel, J. R. P.: 1971, Astrophys. J. Letters 165, L67.Google Scholar
Ostriker, J. P. and Hartwick, F. D. A.: 1968, Astrophys. J. 153, 797.CrossRefGoogle Scholar
Preston, G. W.: 1970, Astrophys. J. Letters 160, L143.Google Scholar
Shipman, H. L.: 1971, Astrophys. J. 167, 165.Google Scholar
Trimble, V.: 1971, Nature 231, 124.Google Scholar