Zeeman-Doppler imaging

In astrophysics, Zeeman-Doppler imaging is a tomographic technique dedicated to the cartography of stellar magnetic fields.

This method makes use of the ability of magnetic fields to polarize the light emitted (or absorbed) in spectral lines formed in the stellar atmosphere (the Zeeman effect). The periodic modulation of Zeeman signatures during the stellar rotation is employed to make an iterative reconstruction of the vectorial magnetic field at stellar surface.

This techniques is based on the principle of maximum entropy image reconstruction; it yields the simplest magnetic field geometry (as a spherical harmonics expansion) among the various solutions compatible with the data [ [http://adsabs.harvard.edu/abs/2006MNRAS.370..629D Donati et al, 2006, MNRAS 370, 629, "The surprising magnetic topology of τ Sco: fossil remnant or dynamo output?"] ] .

This technique is the first to enable the reconstruction of the vectorial magnetic geometry of stars similar to the Sun. It is now offering the opportunity to undertake systematic studies of stellar magnetism and is also yielding information on the geometry of large arches that magnetic fields are able to develop above stellar surfaces. To collect the observations related to Zeeman-Doppler Imaging, astronomers use stellar spectropolarimeters like ESPaDOnS [ [http://www.ast.obs-mip.fr/espadons ESPaDOnS] ] at CFHT on Mauna Kea (Hawaii), as well as NARVAL [ [http://www.ast.obs-mip.fr/projets/narval NARVAL] ] at Bernard Lyot Telescope (Pic du Midi de Bigorre, France).

References

External links

* [http://www.ast.obs-mip.fr/article639.html Zeeman-Doppler Imaging]
* [http://www.ast.obs-mip.fr/article.php3?id_article=457 Stellar tomography: when medical imaging helps astronomy]
* [http://www.ast.obs-mip.fr/article.php3?id_article=458 Recent examples of using Zeeman-Doppler Imaging]