Bibcode
Drake, J. J.; Chung, S. M.; Kashyap, V. L.; Garcia-Alvarez, D.
Bibliographical reference
The Astrophysical Journal, Volume 802, Issue 1, article id. 62, 11 pp. (2015).
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2015
Journal
Citations
4
Refereed citations
3
Description
A fine analysis of spectral line widths and Doppler shifts employing
Fourier transform and cross-correlation techniques has been applied to
Chandra HETG spectra obtained in 1999 October of the rapidly rotating
young star AB Doradus in order to investigate its coronal topology. The
observation lasted 52.3 ks, covering 1.2 rotation periods. The X-ray
light curve obtained from integrating the dispersed signal revealed a
moderate intensity flare midway through the exposure in which the count
rate increased sharply by about 50% and subsequently decayed over the
next 10 ks. We find no significant Doppler shifts in the spectra or
modulation of the light curve that could be attributed to rotation of
dominant coronal structures at this epoch. Individual spectral line
widths are statistically consistent with thermal broadening and formally
require no rotational broadening, while the 1σ limit to
rotational broadening corresponds to a compact corona restricted to
latitudes <57°. Fourier analysis suggests a small amount of
rotational broadening is present consistent with a corona restricted
largely to the poles, and excludes models with surface rotational
broadening or greater. These results present direct spectroscopic
evidence that the dominant coronal activity on rapidly rotating active
stars is associated with the dark polar spots commonly seen in
photospheric Doppler images and support models in which these spots are
of mixed magnetic polarity that forms closed loops.
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