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Astron. Astrophys. 334, 540-544 (1998)


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The large-scale distribution of X-ray active stars *

P. Guillout 1, 2, M.F. Sterzik 1, J.H.M.M Schmitt 1, 3, C. Motch 2, D. Egret 2, W. Voges 1 and R. Neuhäuser 1

1 Max-Planck-Institut für Extraterrestrische Physik, D-85740 Garching, Germany
2 Observatoire Astronomique, CNRS UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, France
3 Universität Hamburg, Hamburger Sternwarte, D-21029 Hamburg, Germany

Received 28 October 1997 / Accepted 23 February 1998

Abstract

We analyse the large-scale sky distribution of 8593 X-ray emitting stars from the cross-correlation of the ROSAT All-Sky Survey sources with the Tycho catalog. We detect a density gradient from the galactic plane to the galactic pole which is attributed to the scale height of the young late type star population of the galactic disc. The data also show a low galactic latitude enhanced feature with respect to mean plane density. We fit the observed X-ray stellar surface density with a model consisting of a constant background component plus an exponential disc and derive for the best fit an inclination [FORMULA] and an ascending node [FORMULA] with respect to the galactic plane. We discuss the Gould belt as a possible explanation to account for the observed enhancement.

Key words: X-ray: stars – Galaxy: stellar content – stars: late-type

* Based on observations made with the ESA Hipparcos astrometry satellite

Send offprint requests to: P. Guillout

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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