Radiative accelerations in stars: The effect of Zeeman splitting

Autor(en)

Georges Alecian, Martin Stift

Abstrakt

The influence of Zeeman splitting on radiative accelerations of chemical elements in stellar atmospheres permeated by magnetic fields with strengths of up to a few Tesla has for the first time been investigated in detail taking into account magneto-optical effects and line blending. The work is based on the newly developed object-oriented and parallel code CARAT (which is presented in some detail), on extensive atomic data taken from the VALD database and on a 12000 K, log g = 4.0 Kurucz atmosphere with solar abundances. The calculations show that magnetically induced spectral line desaturation can lead to unexpectedly large amplifications of accelerations - relative to the zero-field case - in a number of atomic species. These amplifications are found to be strongly dependent both on field strength and on field orientation, reaching a pronounced maximum near the inclination of 60° between field vector and vertical with values sometimes in excess of 1.5 dex. Horizontal accelerations, a consequence of polarised radiative transfer, turn out to remain fairly small and will probably not have any important effect on the diffusion velocity vector. This first study on a large scale of how radiative accelerations are affected by Zeeman splitting is completed by a discussion of the importance of complete atomic line lists, in particular line lists with correct LandeŽ factors; it must also be accepted that magneto-optical effects can by no means be neglected. Finally, it appears that the "canonical" picture of abundance inhomogeneities may have to be revised: instead of being tied to regions with predominantly vertical or horizontal magnetic fields, abundance patches could show up as contours about the curves tracing the field vector inclination of ˜60°.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Université de recherche Paris Sciences et Lettres

Journal

Astronomy & Astrophysics

Band

387

Seiten

271-284

Anzahl der Seiten

14

ISSN

0004-6361

Publikationsdatum

2002

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/aad19a32-4bb2-453d-b97a-23e97da03577