The large-scale distribution of X-ray active stars

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 i = 27.5(deg) +/- 1(deg) and an ascending node l_Ω = 282(deg) +/- 3(deg) with respect to the galactic plane. We discuss the Gould belt as a possible explanation to account for the observed enhancement. Based on observations made with the ESA Hipparcos astrometry satellite