Issue |
A&A
Volume 403, Number 1, May III 2003
|
|
---|---|---|
Page(s) | 155 - 171 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20030257 | |
Published online | 29 April 2003 |
Tomography of a stellar X-ray corona: α Coronae Borealis*
1
Paul Scherrer Institut, Würenlingen & Villigen, CH-5232 Villigen PSI, Switzerland e-mail: guedel@astro.phys.ethz.ch; arzner@astro.phys.ethz.ch
2
Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027, USA e-mail: audard@astro.columbia.edu
3
SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands e-mail: r.mewe@sron.nl
Corresponding author: M. Güdel, guedel@astro.phys.ethz.ch
Received:
9
October
2002
Accepted:
12
February
2003
We interpret the X-ray light curve obtained by XMM-Newton during a total X-ray eclipse in the nearby binary star α Coronae Borealis. This system consists of a G5 V main-sequence star orbiting an X-ray dark A0 star. The secondary G star is
a young, active solar analog with an age of a few
100 Myr. As the primary A star eclipses active regions on
the X-ray bright companion, the light curve drops in consecutive steps
to zero; as individual active regions reappear during egress,
the flux rises in similar steps. The ingress and egress light curves
are combined to reconstruct the 2D distribution
of X-ray brightness on and around the G star. Three different methods are applied,
and variations due to statistical noise and uncertainties in the
binary system parameters are discussed. Although the solutions are
non-unique, all reconstructions reveal a similar distribution of
X-ray bright regions and large areas with little flux. We present
plausible estimates of (lower limits to) the electron densities in
the bright regions, obtaining characteristic values between
109– cm-3.
Key words: stars: activity / stars: coronae / stars: individual: α CrB / X-rays: stars
© ESO, 2003
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