EDP Sciences
Free access
Volume 412, Number 3, December IV 2003
Page(s) 849 - 855
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20034057

A&A 412, 849-855 (2003)
DOI: 10.1051/0004-6361:20034057

A spatially resolved limb flare on Algol B observed with XMM-Newton

J. H. M. M. Schmitt, J.-U. Ness and G. Franco

Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
(Received 8 July 2003 / Accepted 21 August 2003)

We report XMM-Newton observations of the eclipsing binary Algol A (B8V) and B (K2III). The XMM-Newton data cover the phase interval 0.35-0.58, i.e., specifically the time of optical secondary minimum, when the X-ray dark B-type star occults a major fraction of the X-ray bright K-type star. During the eclipse a flare was observed with complete light curve coverage. The decay part of the flare can be well described with an exponential decay law allowing a rectification of the light curve and a reconstruction of the flaring plasma region. The flare occurred near the limb of Algol B at a height of about 0.1  $R_{\star}$ with plasma densities of a few times 10 11 cm -3 consistent with spectroscopic density estimates. No eclipse of the quiescent X-ray emission is observed leading us to the conclusion that the overall coronal filling factor of Algol B is small.

Key words: stars: activity -- stars: coronae -- stars: late type -- X-rays: stars

Offprint request: J. H. M. M. Schmitt, jschmitt@hs.uni-hambourg.de

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