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Description
1XMM is the first comprehensive catalogue of serendipitous X-ray sources from the European Space Agency's (ESA) XMM-Newton observatory launched in December 1999, and has been constructed by the XMM-Newton Survey Science Centre (SSC) on behalf of ESA. Most (>80%) of the entries have not previously been reported as X-ray sources. The catalogue contains source detections drawn from 585 XMM-Newton EPIC observations made between 2000 March 1 and 2002 May 5; all datasets were publicly available by 2003 January 31 but not all public observations are included in this catalogue. Net exposure times in these observations range from less than 1000 up to about 100000 seconds. The total area of the catalogue fields is about 90deg^2^, but taking account of the substantial overlaps between observations, the net sky area covered independently is about 50deg^2^. The observations sample, albeit sparsely, most of the sky, with the exception of a 'hole' centered in the Cygnus region, caused by spacecraft observing constraints. The catalogue source detection and parametrization technique is optimized for point-like sources, and has been performed across several photon-energy bands (see "EPIC energy bands" below) and using data from each of the three EPIC cameras PN, MOS-1, MOS-2; the prefixes PN_ M1_ M2_ are generally used to designate the columns of the catalogue related to the detections by the corresponding camera. The catalogue in its FITS version has ~ 400 columns; these include source-detection parameters (likelihood, position coordinates, counts, count rate, flux, hardness ratio, background estimates, errors etc), the results of cross-correlation with a large number of archival catalogues (SIMBAD, NED, USNO, GSC, APM, ROSAT etc), quality 'flags' resulting from visual screening, and 'meta-data' relating to the observation. For practical considerations the ascii version of the catalogue is made of 3 tables representing the sources, the observations and processing details, and the results of the cross-correlations; the names used as column names in the ASCII version are also reported within parentheses in the "Byte-by-Byte" descriptions below. Details about the construction of the catalogue can be found from the XMM-Newton Survey Science Centre (http://xmmssc-www.star.le.ac.uk/)
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