Landt, H.H.LandtPadovani, P.P.PadovaniPerlman, E. S.E. S.PerlmanGiommi, PaoloPaoloGiommi2020-09-172020-09-172001-11-01https://hdl.handle.net/20.500.13025/110VizieR On-line Data Catalog J/MNRAS/323/757. Originally published in 2001MNRAS.323..757LWe have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray data base with several publicly available radio catalogues, restricting our candidate list to serendipitous X-ray sources with a flat radio spectrum ({alpha}<SUB>r</SUB><=0.70, where S<SUB>{nu}</SUB>~{nu}<SUP>-{alpha}</SUP>). his makes up the Deep X-ray Radio Blazar Survey (DXRBS). Here we present new identifications and spectra for 106 sources, including 86 radio-loud quasars, 11 BL Lacertae objects, and nine narrow-line radio galaxies. Together with our previously published objects and already-known sources, our sample now contains 298 identified objects 234 radio-loud quasars [181 flat-spectrum quasars FSRQ ({alpha}<SUB>r</SUB><=0.50) and 53 steep-spectrum quasars SSRQ], 36 BL Lacs and 28 narrow-line radio galaxies. Redshift information is available for 96 per cent of these. Thus our selection technique is ~90 per cent efficient at finding radio-loud quasars and BL Lacs. Reaching 5-GHz radio fluxes ~50mJy and 0.1-2.0keV X-ray fluxes a few W10-14erg/cm<SUP>2</SUP>/s, DXRBS is the faintest and largest flat-spectrum radio sample with nearly complete (~85 per cent) identification. (3 data files).QSOsBL Lac objectsSurveysX-ray sourcesRadio sources Comment table4.dat 127x93 Positional information; table5.dat 127x107 Object properties; notes.dat 122x80 Individual noteshttp://adsabs.harvard.edu/abs/2001yCat..73230757L2001yCat..73230757L