Continued Investigations into the Magnetic Activity of alpha Centauri A
Abstract
A long standing problem and a central topic of ``solar-stellar'' connection studies is that of relating the Sun's magnetic behavior to other stars. Our Sun is used as a fundamental calibration and reference point for stellar theory. This requires that the Sun's expressions of activity (distribution of magnetically active regions, frequency of starspots, coronal densities, emergence of magnetic flux, etc.) are fundamentally ``normal'' for a star of its age and evolutionary history. Direct comparison with true solar analogs is critical for understanding both the magnetic nature of the Sun as well as magnetic phenomena in other stars. An important component of this field is the investigation of magnetic activity cycles that occur within these solar proxies, and the associated changes in high energy coronal, transition region, and chromospheric emissions.
$\alpha$ Centauri A is an ideal solar analog, with a convenient proximity to the Earth ({\it d} = 1.347 pc), similar physical properties ({\it M}/{\it M}$_{\odot}$ = 1.09, {\it R}/{\it R}$_{\odot}$ = 1.22; {\it T}/{\it T}$_{\odot}$ = 1.009, and depth of convection zone), and an age just slightly older than that of the Sun ($\tau$ $\approx$ 5-6 Gyr). Presented are the current results of our ongoing investigation of the coronal (X-ray; {\it ROSAT, Chandra, XMM}), transition region (FUV-UV; {\it FUSE, BEFS, IUE}), and chromospheric (FUV-NUV; {\it FUSE, IUE}) emissions of this solar-type star. We examine the magnetic activity of $\alpha$ Cen A over both long ($\sim$20 yr) and short ($\sim$30 day) timescales, and discuss evidence for both a solar-like $\sim$10 yr magnetic activity cycle and a possible rotational modulation of $\sim$20 days. We gratefully acknowledge support by NASA Grant NNX06AC45G and the Villanova University Research for Undergraduates Award Program.- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AAS...21110423C