Preprint Logo P79 December
2002


To be published in:
The Astrophysical Journal

An X-ray investigation of the NGC346 field in the SMC (2) :
the field population

Y. Nazé1,*, J. M. Hartwell2, I. R. Stevens2, J. Manfroid1,**,***, S. Marchenko3, M. F. Corcoran4, A. F. J. Moffat5 and G. Skalkowski5


1 Institut d'Astrophysique et de Géophysique - Université de Liège, Allée du 6 Août, 17, Bât. B5c, B-4000 Liège, Belgium
2 School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
3 Department of Physics and Astronomy, Thompson Complex Central Wing, Western Kentucky University, Bowling Green, KY 42101-3576 (USA)
4 Universities Space Research Association, High Energy Astrophysics Science Archive Research Center, Goddard Space Flight Center, Greenbelt, MD 20771, USA
5 Département de physique, Université de Montreal, C.P. 6128, Succ. Centre-Ville, Montreal, QC, H3C 3J7, Canada

* Research Fellow FNRS, Belgium
** Research Director FNRS, Belgium
*** Visiting Astronomer, ESO


Abstract

     We present results from a Chandra observation of the NGC346 cluster, which is the ionizing source of N66, the most luminous HII region and the largest star formation region in the SMC. In the first part of this investigation, we have analysed the X-ray properties of the cluster itself and the remarkable star HD 5980. But the field contains additional objects of interest. In total, 75 X-ray point sources were detected in the Chandra observation: this is five times the number of sources detected by previous X-ray surveys. We investigate here their characteristics in detail. Due to high foreground absorption, the sources possess rather high hardness ratios. Their cumulative luminosity function appears generally steeper than that for the rest of the SMC at higher luminosities. Their absorption columns suggest that most of the sources belong to NGC 346. Using DSS data and new UBVRI imaging with the ESO 2.2m telescope, we also discovered possible counterparts for 32 of these X-ray sources and estimated a B spectral type for a large number of these counterparts. This tends to suggest that most of the X-ray sources in the field are in fact X-ray binaries. Finally, some objects show X-ray and/or optical variability, with a need for further monitoring.

Key Words
(galaxies:): Magellanic Clouds -- X-rays: individual (NGC346)

Files
Article: ngc346-2.pdf (1120593 bytes): HTTP FTP (ftp://vela.astro.ulg.ac.be/preprints/)


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