Broad band energy distribution of ROSAT detected quasars II: Radio-quiet objects

Simple item page
dc.creatorYuan, W.
dc.creatorBrinkmann, W.
dc.creatorSiebert, J.
dc.creatorVoges, W.
dc.date1998-05-04
dc.date.accessioned2026-07-07T10:48:02Z
dc.date.available2026-07-07T10:48:02Z
dc.descriptionA database of radio-quiet quasars detected with ROSAT is presented containing 846 quasars seen in the All-Sky Survey and/or in pointed PSPC observations. About 70% of the objects have been detected in X-rays for the first time. We present the soft X-ray fluxes and spectra, if available. Using an optically selected subsample compiled from this database, we study the broad band properties of radio-quiet quasars with high statistical significance. We confirm that radio-quiet quasars have in general steeper soft X-ray spectra than radio-loud. The spectral differences persist to high redshifts. A spectral flattening with increasing redshift is confirmed up to redshift around 2, beyond which the spectral slopes seem to be independent of redshift. The spectral slopes of the ROSAT radio-quiet quasars at z>2.5 are consistent with those found for nearby quasars in the medium energy band (2-10keV), implying that the X-ray spectral evolution is not important. We show that there is, in a statistical sense, little or no excess absorption for most of the radio-quiet objects at z>2. The existence of a correlation between the X-ray luminosity and the luminosity at 2500A is confirmed. Individual objects show a large scatter from this correlation. The X-ray loudness alpha_ox appears to be independent of z, but the analyses indicate a slight increase of alpha_ox with optical luminosity. However, this behavior is likely not caused by physical properties inherent to the quasars but is the result of the intrinsic dispersion. Finally, we find a small fraction of objects which appear to be relatively `X-ray quiet' compared to the bulk of the other quasars.
dc.descriptionA&A Latex v.3, 16 pages, 12 PS-figures, The table is available at the CDS database
dc.identifierhttps://arxiv.org/abs/astro-ph/9805015
dc.identifierhttp://arxiv.org/abs/astro-ph/9805015
dc.identifierAstron.Astrophys.330:108,1998
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/183742
dc.subjectAstrophysics
dc.titleBroad band energy distribution of ROSAT detected quasars II: Radio-quiet objects
dc.typetext

Files

Collections

arXiv