Stellar model atmospheres with magnetic line blanketing

III. The role of magnetic field inclination

¹ Physics and Astronomy Department, University of Western Ontario, London, ON N6A 3K7, Canada e-mail: skhan@astro.uwo.ca
² Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria

Received: 31 January 2006
Accepted: 29 March 2006

Abstract

Context.We introduced the technique of model atmosphere calculation with polarized radiative transfer and magnetic line blanketing. However, the calculation of model atmospheres with realistic magnetic field configurations (field strength and angle defined relative to the atmosphere plane) has not been previously attempted.

Aims.In the last paper of this series we study the effects of the magnetic field, varying its strength and orientation, on the model atmosphere structure, the energy distribution, photometric colors and the hydrogen Balmer line profiles. We compare with the previous results for an isotropic case in order to understand whether there is a clear relation between the value of the magnetic field angle and model changes, and to study how important the additional orientational information is. Also, we examine the probable explanation of the visual flux depressions of the magnetic chemically peculiar stars in the context of this work.

Methods.We calculated one more grid of the model atmospheres of magnetic A and B stars for different effective temperatures ( K, 11 000 K, 15 000 K), magnetic field strengths (, 5, 10, 40 kG) and various angles of the magnetic field (–) with respect to the atmosphere plane. We used the LLModels code which implements a direct method for line opacity calculation, anomalous Zeeman splitting of spectral lines, and polarized radiation transfer.

Results.We have not found significant changes in model atmosphere structure, photometric and spectroscopic observables or profiles of hydrogen Balmer lines as we vary the magnetic field inclination angle Ω. The strength of the magnetic field plays the main role in magnetic line blanketing. We show that the magnetic field has a clear relation to the visual flux depressions of the magnetic CP stars.

Conclusions.We can use the approach introduced in the previous paper of this series, which neglects anisotropy effects, to calculate model atmospheres with magnetic line blanketing. This technique seems to be reliable, at least for homogeneous atmospheres with scaled solar abundances.