A multi-wavelength view of AB Doradus outer atmosphere . Simultaneous X-ray and optical spectroscopy at high cadence
Abstract
Aims: We study the chromosphere and corona of the ultra-fast rotator
Methods: From the X-ray observations we investigated the variations in coronal temperature, emission measure, densities, and abundance. We interpreted our data in terms of a loop model. From the optical data we characterised the flaring chromospheric material using numerous emission lines that appear in the course of the flares. A detailed analysis of the line shapes and line centres allowed us to infer physical characteristics of the flaring chromosphere and to coarsely localise the flare event on the star.
Results: We specifically used the optical high-cadence spectra to demonstrate that both turbulent and Stark broadening are present during the first ten minutes of the first flare. Also, in the first few minutes of this flare, we find short-lived (one to several minutes) emission subcomponents in the Hα and Ca ii K lines, which we interpret as flare-connected shocks owing to their high intrinsic velocities. Combining the space-based data with the results of our optical spectroscopy, we derive flare-filling factors. Finally, comparing X-ray, optical broadband, and line emission, we find a correlation for two of the three flaring events, while there is no clear correlation for one event. Also, we do not find any correlation of the radio data to any other observed data.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- December 2013
- DOI:
- 10.1051/0004-6361/201321419
- arXiv:
- arXiv:1309.4933
- Bibcode:
- 2013A&A...560A..69L
- Keywords:
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- stars: activity;
- stars: coronae;
- stars: late-type;
- stars: chromospheres;
- stars: individual: AB Doradus A;
- stars: magnetic field;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- doi:10.1051/0004-6361/201321419