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A ROSAT PSPC catalogue of X-ray sources in the LMC region
We analyzed more than 200 ROSAT PSPC observations in a 10 by 10 degreefield centered on the Large Magellanic Cloud (LMC) and performed between1990 and 1994 to derive a catalogue of X-ray sources. The list contains758 sources with their X-ray properties. From cross-correlations of thePSPC catalogue with the SIMBAD data base and literature searches we givelikely identifications for 144 X-ray sources based on positionalcoincidence, but taking into account X-ray properties like hardnessratios and source extent. 46 known sources are associated with supernovaremnants (SNRs) and candidates in the LMC, most of them already detectedby previous X-ray missions. Including the new candidates from\cite[Haberl & Pietsch (1999)]{HP99} based on variability studies ofthe sources in our PSPC catalogue, the number of X-ray binaries in theLMC increased to 17 and that of the supersoft sources (SSSs) to 9. Theremaining ~ 50% of the identified sources comprise mainly foregroundstars (up to 57) and background extragalactic objects (up to 15). Theoften distinguished X-ray properties of the different source types wereused for a first classification of new, unknown X-ray sources. Eight newPSPC sources are classified as SNRs from their hardness ratios and onepromising new SNR candidate with extended X-ray emission is foundfurther north than all known SNRs. Three soft X-ray sources havehardness ratios compatible to those of the known SSSs. A selection onhardness ratios and X-ray to optical flux ratio further suggests 27foreground stars and 3 AGN.
| Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
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