Free access article

Issue A&A Volume 403, Number 1, May III 2003 Page(s) 155 - 171 Section Stellar atmospheres DOI 10.1051/0004-6361:20030257

A&A 403, 155-171 (2003)
DOI: 10.1051/0004-6361:20030257

Tomography of a stellar X-ray corona: Coronae Borealis

M. Güdel¹, K. Arzner¹, M. Audard² and R. Mewe<sup>3

1</sup>  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

(Received 9 October 2002 / Accepted 12 February 2003 )

Abstract
We interpret the X-ray light curve obtained by XMM-Newton during a total X-ray eclipse in the nearby binary star  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: CrB -- X-rays: stars

Offprint request: M. Güdel, guedel@astro.phys.ethz.ch

SIMBAD Objects

© ESO 2003

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link containsarticle metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means:

• if your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages,
• you can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library,
• you can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.