Astronomy and Astrophysics, volume 454, 1047-1063 (2006/8-2)
An XMM-Newton view of the young open cluster NGC 6231. I. The catalogue.
SANA H., GOSSET E., RAUW G., SUNG H. and VREUX J.-M.
Abstract (from CDS):
This paper is the first of a series dedicated to the X-ray properties of the young open cluster NGC6231. Our data set relies on an XMM-Newton campaign of a nominal duration of 180ks and reveals that NGC6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources are detected in the present field of view, centered on the cluster core. The limiting sensitivity of our survey is approximately 6x10–15erg/cm2/s but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogues, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 3" at maximum. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin2 and a core radius close to 3.1-arcmin. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC6231. Finally, beside a few bright but soft objects - corresponding to the early-type stars of the cluster - most of the sources are relatively faint (∼5x10–15erg/cm2/s) with an energy distribution peaked around 1.0-2.0keV.
open clusters and associations: individual: NGC 6231 - X-rays: individual: NGC 6231 - X-rays: stars - stars: early-type - catalogues
VizieR on-line data:
<Available at CDS (J/A+A/454/1047): table3.dat table6.dat>