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The coronal structure of AB Dor determined from contemporaneous Doppler imaging and X-ray spectroscopy

By G. A. J. Hussain, M. Jardine, J. -f. Donati, N. S. Brickhouse, N. J. Dunstone, K. Wood, A. K. Dupree, A. Collier Cameron and F. Favata

Abstract

We obtain contemporaneous observations of the surface and corona of AB Dor, a young single cool star, using ground-based circularly polarised spectra from the Anglo-Australian Telescope and X-ray lightcurves and spectra from the Chandra satellite. The ground-based data are used to construct surface magnetic field maps, which are extrapolated to produce detailed models of the quiescent corona. The X-ray data serve as a new test for the validity of these coronal models. We find that AB Dor’s X-ray corona must be concentrated close to its surface, with a height, H ∼ 0.3–0.4R∗; this height is determined by the high coronal density and complex multi-polar magnetic field from the surface maps. There is also significant correlation between the positions of surface and coronal active longitudes as determined from the surface spot and magnetic field maps and the X-ray lightcurve. At this epoch (2002 December) AB Dor appears to possess one very large active longitude region, covering almost half the star; displaying enhanced activity in the form of large dark spots, strong magnetic fields and chromospheric emission. This is unusua

Year: 2007
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