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Zeeman Doppler Imaging of Stars with the AAT

Published online by Cambridge University Press:  25 April 2016

Brad Carter ,
Steve Brown ,
Jean-François Donati ,
David Rees  and
Meir Semel
Brad Carter
Affiliation:
Centre for Astronomy and Atmospheric Research, Faculty of Sciences, University of Southern Queensland, Toowoomba, Qld 4350, Australiacarterb@usq.edu.au
Steve Brown
Affiliation:
School of Information Science and Technology, Flinders University, GPO Box 2100, Adelaide, SA 5001, Australia
Jean-François Donati
Affiliation:
Laboratoire d’Astrophysique, Observatoire Midi-Pyrénées, 14 Avenue Edouard Belin, F-31400 Toulouse, France
David Rees
Affiliation:
CSIRO Division of Radiophysics, PO Box 76, Epping, NSW 2121, Australia
Meir Semel
Affiliation:
DASOP, Observatoire de Paris, Section de Meudon, F-92195, Meudon Principal Cédex, France
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Abstract

Zeeman Doppler Imaging (ZDI) is a recent technique for measuring magnetic fields on rapidly rotating, active stars. ZDI employs spectropolarimetry taken at different rotational phases to derive information on the magnetic field distribution over the stellar surface. The Zeeman effect is used to identify the presence of a magnetic field, and variations in Doppler wavelength shifts across the rapidly rotating star allow fields to be resolved on different parts of the visible disk. Analysis of the spectra can be used to produce both thermal and surface magnetic images. ZDI requires very high S/N spectra to be acquired within a time interval short compared to the stellar rotation period. As a result, a large-aperture telescope is needed. Since an initial successful test in 1989, the 3·9 m Anglo-Australian Telescope has been used to obtain ZDI spectra of active stars of different evolutionary stages. The observations have concentrated on the K subgiant in the RSCVn system HR 1099 to monitor changes on this bright and active star. With the advent in 1991 of ZDI spectropolarimetry with the AAT échelle spectrograph, it has become possible to co-add the polarisation signature from the many magnetically sensitive lines recorded simultaneously. As a result, stellar magnetic field detections of unprecedented quality have been obtained. The aims of this paper are to briefly outline the principles of ZDI, describe the instrumental setup at the AAT and present some preliminary results from recent observations.

Keywords

stars: activitystars: magnetic fieldsstars individual (HR 1099)techniques: spectroscopic
Type
Galactic and Stellar
Information
Publications of the Astronomical Society of Australia , Volume 13 , Issue 2 , May 1996 , pp. 150 - 155
Copyright
Copyright © Astronomical Society of Australia 1996

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References

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