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Astron. Astrophys. 358, 1151-1156 (2000)


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The physical foundations of stellar magnetic field diagnosis from polarimetric observations of hydrogen lines

G. Mathys 1, C. Stehlé 2, S. Brillant 1 and T. Lanz 3,4

1 European Southern Observatory, Casilla 19001, Santiago 19, Chile
2 DASGAL, UMR8633, Observatoire de Paris, 5 place J. Janssen, 92195 France (Chantal.Stehle@obspm.fr)
3 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
4 NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USA

Received 5 January 2000 / Accepted 28 March 2000

Abstract

We have completed a new study of the formation of hydrogen lines in dense magnetized plasmas. We have developed a global formalism including the effects of the magnetic field and of the motional electric field. The latter, resulting from the motion of the radiating hydrogen atom in the magnetic field, modifies the structure of the matrices appearing in the equation of transfer of the Stokes vector and introduces a coupling between microscopic ("intrinsic") and macroscopic (Doppler) contributions to the line profiles. We have used this new treatment of line formation to revisit the interpretation of photopolarimetric (Stokes I and V) observations of Balmer lines in terms of mean longitudinal magnetic field.

Key words: line: formation – polarization – radiative transfer – stars: atmospheres – stars: magnetic fields

Send offprint requests to: C. Stehlé

© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000

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