J/A+A/311/384ivo://CDS.VizieR/J/A+A/311/384doi:10.26093/cds/vizier.33110384CDSLamer G.Brunner H.Staubert R.1997-12-09T16:43:37Z1997-12-09T17:43:33ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frbl-lacertae-objectsx-ray-sourcesWe present soft X-ray spectra of 74 BL Lacertae objects observed with the PSPC detector on board of the ROSAT satellite. The sample contains all BL Lac objects detected during the pointed observation phase as a target or serendipitously. We have investigated the soft X-ray and broad band spectral properties and discuss the consequences for the X-ray emission processes. For the first time a clear dependence of the X-ray spectral steepness on the radio to X-ray spectral energy distribution is found: {alpha}_rx_ and {alpha}_x_ are correlated in the X-ray selected (XBL) subsample and anticorrelated in the radio selected (RBL) subsample. The objects with intermediate {alpha}_rx_ values thus do have the steepest soft X-ray spectra. Simulated PSPC spectra based on a set of simple two component multifrequency spectra are in good agreement with the measurements and suggest a broad range of synchrotron cutoff energies. We have calculated synchrotron self-Compton beaming factors for a subsample of radio bright objects and find a correlation of the beaming factors {delta}_IC_ with {alpha}_rx_ and {alpha}_x_. The most extreme RBL objects are very similar to flat spectrum radio quasars in all their broad band and X-ray properties.1996A&A...311..384Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/311/384CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/311/384https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/311/384http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/311/384https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/311/384https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/311/384http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/311/384GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapROSATX-raydefaultJ/A+A/311/384/table2List of PSPC observationsROR2? Second ROR numbermeta.idintDateCompleted datetime.epochcharExpExposition timestime.duration;obs.exposureintCountsNet countsphot.count;em.X-rayfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameObject namemeta.id;meta.maincharRORROSAT observation request (ROR) numbermeta.id;obsintn_ROR[-] '-' when two ROR numbersmeta.notechare_Counts? rms uncertainty on Countsstat.errorintJ/A+A/311/384/table3X-ray and broad band spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameObject namemeta.id;meta.maincharNH,galGalactic hydrogen column density1e+20cm**-2phys.columnDensityfloatn_NH,galNote on NH,gal (1)meta.notecharNH,fit? Fitted hydrogen column density1e+20cm**-2phys.columnDensityfloate_NH,fit? rms uncertainty on NH,fit1e+20cm**-2stat.errorfloatF1keVFlux at 1 keVuJyphot.flux;em.X-rayfloatalphaSpectral index between .1kev and 2.4keVspect.indexfloate_alpharms uncertainty on alphastat.errorfloatalpha_rx_X-ray spectral indexspect.indexfloatdelta_IC_? Inverse Compton beaming factorstat.fit.paramfloat