The ROSAT international X-ray/Optical survey (RIXOS): Source catalogue

We describe the ROSAT International X-ray/Optical Survey (RIXOS), a medium- sensitivity survey and optical identification of X-ray sources discovered i n ROSAT high Galactic latitude fields (\ b \> 28 degrees) and observed with the Position Sensitive Proportional Counter (PSPC) detector. The survey ma de use of the central 17 arcmin of each ROSAT field. A flux limit of 3x10(- 14) erg cm(-2) s(-1) (0.5-2 keV) was adopted for the survey, and a minimum exposure time of 8000 s was required for qualifying ROSAT observations. X-r ay sources in the survey are therefore substantially above the detection th reshold of each field used, and many contain enough counts to allow the X-r ay spectral slope to be estimated. Spectroscopic observations of potential counterparts were obtained of all s ources down to the survey limit in 64 fields, totalling a sky area of 15.77 deg(2). Positive optical identifications are made for 94 per cent of the 2 96 sources thus examined. A further 18 fields (4.44 deg(2)), containing 105 sources above the 3x10(-14) erg cm(-2) s(-1) survey limit, are completely optically identified to a higher flux of 8x10(-14) erg cm(-2) s(-1) (0.5-2 keV). Optical spectroscopic data are supplemented by deep CCD imaging of ma ny sources to reveal the morphology of the optical counterparts, and object s too faint to register on Sky Survey plates. The faintest optical counterp arts have R similar to 22. This paper describes the survey method, and presents a catalogue of the RIX OS sources and their optical identifications. Finding charts based on Sky S urvey data are given for each source, supplemented by CCD imaging where nec essary.