The Soft X-Ray Properties of a Complete Sample of Optically Selected Quasars II. Final Results

Abstract

We present the final results of a ROSAT PSPC program to study the soft X-ray emission properties of a complete sample of low $z$ quasars. The main results are: 1. There is no evidence for significant soft excess emission or excess foreground absorption by cold gas in 22 of the 23 quasars. 2. The mean 0.2-2 keV continuum of quasars agrees remarkably well with an extrapolation of the mean 1050-350A continuum recently determined by Zheng et al. (1996), indicating that there is no steep soft component below 0.2 keV. 3. The occurrence of warm absorbers in quasars is rather rare, in sharp contrast to lower luminosity AGN. 4. The strongest correlation found is between the spectral slope, alpha_x, and the Hb FWHM. This remarkably strong correlation may result from a dependence of alpha_x on L/L_Edd, as seen in Galactic black hole candidates. 5. There appears to exist a distinct class of ``X-ray weak'' quasars. These may be quasars where the direct X-ray source is obscured, and only scattered X-rays are observed. 6. Thin accretion disk models cannot reproduce the observed optical to soft X-ray spectral shape. An as yet unknown physical mechanism maintains a strong correlation between the optical and soft X-ray emission. 7. The well known difference in alpha_x between radio-loud and radio-quiet quasars may be due only to their different Hb FWHM. 8. The agreement of the 21 cm and X-ray columns implies that He in the diffuse H II component of the Galactic ISM is ionized to He II or He III (shortened abstract).

19 pages of text only, uses aas2pp4.sty file, to appear in ApJ vol. 447, 3/1/97, complete postscript version of 34 pages including 5 tables and 8 figures available at http://physics.technion.ac.il/~laor/rosat/paper.ps

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• Hydrodynamic Models of Line-Driven Accretion Disk Winds III: Local Ionization Equilibrium
• Optically bright Active Galactic Nuclei in the ROSAT-Faint Source Catalogue
• Statistical analysis of AlIII 1860 and CIII] 1909 emission lines as virial black hole mass estimators in quasars
• Hubble Space Telescope [O III] Emission-Line Kinematics in Two Nearby QSO2s: A Case for X-ray Feedback
• Main trends of the quasar main sequence -- effect of viewing angle
• The BeppoSAX view of NLS1s
• Modeling the UBVRI time delays in Mrk 335
• PKS 1018-42: A Powerful Kinetically Dominated Quasar
• Multi-wavelength Campaign on the Super-Eddington NLS1 RX J0134.2-4258 -- I. Peculiar X-ray Spectra and Variability
• Understanding AGN-host connection in partially obscured active galactic nuclei. Part III: Properties of ROSAT-selected SDSS AGNs
• Classifying Radio Emitters from the Sloan Digital Sky Survey: Spectroscopy and Diagnostics
• Insights Into AGN and Host Galaxy Co-evolution From Hard X-ray Emission
• On the peculiar properties of the narrow-line quasar PG 1543+489
• Estimating the Jet Power of Mrk\,231 During the 2017-2018 Flare
• ASCA observations of deep ROSAT fields V. The X-ray spectrum of hard X-ray selected QSOs
• The Nature of the UV/X-Ray Absorber in PG 2302+029
• Connecting the X-ray/UV variability of Fairall 9 with NICER: A Possible Warm Corona
• A Direct Linkage Between AGN Outflows in The Narrow-line Regions and The X-ray Emission From The Accretion disks
• BeppoSAX observations of the Narrow-Line Seyfert 1 galaxy RX J1702.5+3247
• The Relation between X-ray and Ultraviolet Variability of Quasars
• Radiative non-isothermal Bondi accretion onto a massive black hole
• The obscured QSO 1SAX J1218.9+2958
• An X-ray Survey in SA 57 with XMM-Newton
• Optical and X-ray characteristics of a newly discovered narrow-line QSO : RX J1334.2+3759
• Theoretical Models of Multi-waveband QSO Luminosity Functions
• Unveiling the quasar main sequence: illuminating the complexity of active galactic nuclei and their evolution
• The Highly Self-Absorbed Blazar, PKS\,1351$-$018
• X-Ray Microlensing of Bright Quasars
• Soft X-ray properties of a high redshift sample of QSOs observed with ROSAT
• X-ray He-like ion diagnostics: New computations for photoionized plasma. II: Influence of different parameters
• Investigating the complex X-ray spectrum of a broad-line 2MASS red quasar: XMM-Newton observation of FTM 0830+3759
• The story of Seyfert galaxy RE J2248-511: from intriguingly ultrasoft to unremarkably average
• The Discovery of Soft X-ray Loud Broad Absorption Line Quasars
• Rest-frame optical continua of L ~ L*, z>3 quasars: probing the faint end of the high z quasar luminosity function
• IMPETUS: New Cloudy's radiative tables for accretion onto a galaxy black hole
• Influence of Comptonization region over the ambiance of accretion disc in Active Galactic Nucleus
• PKS 1622-253: A Weakly Accreting, Powerful Gamma Ray Source
• X-ray selected broad absorption line quasars in SDSS-V: BALs and non-BALs span the same range of X-ray properties
• Swift Observations of the highly X-ray variable Narrow Line Seyfert 1 galaxy RX J0148.3-2758
• Unveiling the X-ray/UV properties of disk winds in active galactic nuclei using broad and mini-broad absorption line quasars
• Constraining X-ray emission of magnetically arrested disk (MAD) by radio-loud AGNs with extreme ultraviolet (EUV) deficit
• A Systematic Study of the Short-Term X-ray Variability of Seyfert Galaxies I. Diversity of the X-ray Rms Spectra
• Stochastic Absorption of the Light of Background Sources due to Intergalactic Neutral Hydrogen I. Testing different line-number evolution models via the cosmic flux decrement
• The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C82
• Spectral Energy Distribution Variations of Nearby Seyfert Galaxies During AGN Watch Monitoring Programs
• RE J2248-511 - Not all variable, ultrasoft, X-ray AGN have narrow Balmer lines
• XMM-Newton Detection of the Rare FR II BAL Quasar FIRST J101614.3+520916
• Active Galaxies in the UV
• Near Infrared observations of Soft X-ray selected AGN
• SDSS J143030.22-001115.1: A misclassified narrow-line Seyfert 1 galaxy with flat X-ray spectrum
• Constraining black hole spin in PG 1535+547 amidst complex multi-layered absorption
• The FRII Broad Line Seyfert 1 Galaxy: PKSJ 1037-2705
• Seyfert Galaxies and BeppoSAX
• Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow
• The Energetics of the Central Engine in the Powerful Quasar, 3C298
• First Detection of 12CO (1--0) Emission from Two Narrow-Line Seyfert 1 Galaxies
• Spectral Energy Distributions of Active Galactic Nuclei from an Accretion Disk with Advective Coronal Flow
• Untangling the Complex Nature of AGN Variability with Fairall 9
• Spectral Energy Distribution Modeling of Broad Emission Line Quasars: From X-ray to Radio Wavelengths
• An exploratory study of the hard X-ray variability properties of PG quasars with RXTE
• SRG/eROSITA-SDSS view on the relation between X-ray and UV emission for quasars
• Probing the extremes of Seyfert activity: BeppoSAX observations of Narrow-Line Seyfert 1 galaxies