Measurements of stellar magnetic fields using synthetic spectrum fitting^*

Atomic Astrophysics, Lund Observatory, Box 43, 221 00 Lund, Sweden

Corresponding author: K. Nielsen, krister.nielsen@astro.lu.se

Received: 26 June 2002
Accepted: 30 August 2002

Abstract

A sample of Ap and Bp stars have been investigated with respect to their surface magnetic field using synthetic spectrum fitting. The advantage of this technique is the simplicity in determining the surface field strength and the possibility to apply it to objects whose spectrum does not display resolved Zeeman components. We show the usefulness of the method by demonstrations on stellar spectra with resolved Zeeman components, where the results have been compared with values based on measurements of the Zeeman splitting for the magnetically sensitive λ6149 line. The objects HD 192678 and HD 165474 have been observed over their rotational period to investigate magnetic field variations. The analysis is then extended to objects where no resolved structure is observed. The rapidly rotating stars HD 22316 and HD 10783 are used as examples where this method is useful to achieve a value of the surface field. The relative intensification of the 6147, 6149 lines is investigated in an attempt to understand its relation to the surface magnetic field strength for the stars HD 22316 and HD 10783.