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Issue A&A
Volume 400, Number 2, March III 2003
Page(s) 671 - 678
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20021899



A&A 400, 671-678 (2003)
DOI: 10.1051/0004-6361:20021899

Chandra-LETGS X-ray observation of $\alpha$ Centauri: A nearby (G2V + K1V) binary system

A. J. J. Raassen1, 2, J.-U. Ness3, R. Mewe1, R. L. J. van der Meer1, V. Burwitz4 and J. S. Kaastra1

1  SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2  Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
3  Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
4  Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany

(Received 7 October 2002 / Accepted 23 December 2002)

Abstract
A Chandra LETGS X-ray observation of $\alpha$ Centauri with an exposure time of 81.5 ks is presented with the two components (K1V and G2V) spectrally resolved for the first time. We use the emission lines from the individual spectra to determine plasma temperatures and find similar temperatures as for the Sun with higher temperatures for the K1V star than for the G2V star. Global fitting techniques are used in order to construct an emission measure distribution for each star and we find emission measure distributions consistent with what is found from the line ratios. A two-temperature model is used in order to derive abundances normalized to iron and relative to solar photosheric values. For both stars we find a FIP effect with a slight but not significant tendency of a stronger FIP effect for the K1V component.


Key words: stars: individual: $\alpha$ Centauri -- stars: coronae -- stars: late-type -- stars: activity -- X-rays: stars

Offprint request: A. J. J. Raassen, A.J.J.Raassen@sron.nl

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© ESO 2003


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