The ROSAT all-sky survey bright source catalogue

We present the ROSAT All-Sky Survey Bright Source Catalogue (RASS-BSC, revi sion 1RXS) derived from the all-sky survey performed during the first half year (1990/91) of the ROSAT mission. 18,811 sources are catalogued (i) down to a limiting ROSAT PSPC count-rate of 0.05 cts s(-1) in the 0.1-2.4 keV e nergy band, (ii) with a detection likelihood of at least 15 and (iii) at le ast 15 source counts. The 18,811 sources underwent both an automatic valida tion and an interactive visual verification process in which for 94% of the sources the results of the standard processing were confirmed. The remaini ng 6% have been analyzed using interactive methods and these sources have b een flagged. Flags are given for (i) nearby sources; (ii) sources with posi tional errors; (iii) extended sources; (iv) sources showing complex emissio n structures; and (v) sources which are missed by the standard analysis sof tware. Broad band (0.1-2.4 keV) images are available for sources flagged by (ii), (iii) and (iv). For each source the ROSAT name, position in equatori al coordinates, positional error, source count-rate and error, background c ount-rate, exposure time. two hardness-ratios and errors, extent and likeli hood of extent, likelihood of detection, and the source extraction radius a re provided. At a brightness limit of 0.1 cts s(-1) (8,547 sources) the cat alogue represents a sky coverage of 92%. The RASS-BSC, the table of possibl e identification candidates, and the broad band images are available in ele ctronic form (Voges et al. 1996a) via http://wave.xray.mpe.mpg.de/rosat/cat alogues/rassbsc.(1)