The Soft X-Ray Properties of a Large Optical QSO Sample: ROSAT Observations of the Large Bright Quasar Survey

Green, Paul; Schartel, N.; Anderson, Scott F.; Hewett, Paul C.; Foltz, C. B.; Brinkmann, W.; Fink, H. H.; Truemper, J.; Margon, B.

doi:10.1086/176118

Cited by 131 publications

(152 citation statements)

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“…They further suggested that the X-ray (warm) absorption may arise in the intervening gas. Note that the column density of the screening gas ( N H M 10" -10'' cm-2) is at least an order of magnitude smaller than that required of the inner edge of the wind in the models of , and thus is consistent with the fact that several BAL quasars have normal optical to X-ray flux ratios (e.g., Green et al 1995). challenge, but will lead to a better understanding of each effect and its role in establishing the structure and dynamics of AGN.…”

supporting

confidence: 64%

Mass Loss from the Nuclei of Active Galaxies

Crenshaw

Kraemer

George

2003

Annu. Rev. Astron. Astrophys.

495

527

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Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The "intrinsic" UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show https://ntrs.nasa.gov/search.jsp?R=20030093727 2018-05-11T13:03:18+00:00ZCrenshaw. Kraemer. George variable ionic column densities] which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight . Detailed studies of the intrinsic absorbers.with the assistance of monitoring observations and photoionization models. provide constraints on their kinematics] physical conditions. and locations relative to the central continuum source.which range from the inner nucleus (-0.01 pc) to the galactic disk or halo (-10 kpc) . Dynamical models that make use of thermal winds. radiation pressure. and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints . CONTENTS

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supporting

confidence: 64%

Mass Loss from the Nuclei of Active Galaxies

Crenshaw

Kraemer

George

2003

Annu. Rev. Astron. Astrophys.

495

527

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“…BALQSOs are invariably X-ray weak or silent (Green et al 1995;Green & Mathur 1996;Gallagher et al 1999), suggesting the presence of very large absorbing columns, N H ≥ 10 23 cm −2 , 2-3 orders of magnitudes larger than those inferred from UV absorption line studies. This discrepancy led to the conclusion that the bulk of the absorbing gas is highly ionised and thus mostly transparent in the ultraviolet while still providing large X-ray opacities.…”

Section: Introductionmentioning

confidence: 90%

Long observations of the BALQSO LBQS 2212-1759 with XMM-Newton

Clavel¹,

Schartel

Tomás

2006

A&A

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Very long (172 ks effective exposure time) observations of the BALQSO LBQS 2212-1759 with XMM-Newton yield a stringent upper-limit on its 0.2-10 keV (rest-frame 0.64-32.2 keV) flux, F 0.64−32.2 ≤ 6 × 10 −17 erg cm −2 s −1 , while simultaneous UV and optical observations reveal a rather blue spectrum extending to 650 Å in the source rest frame. These results are used to set a tight upper-limit on its optical to X-ray spectral index α ox ≤ −2.56. Given the HI-BAL nature of LBQS 212-1759, its X-ray weakness is most likely due to intrinsic absorption. If this is the case, and assuming that the intrinsic α ox of LBQS 2212-1759 is −1.63 -a value appropriate for a radio-quiet quasar of this luminosity -one can set a lower limit on the X-ray absorbing column N H ≥ 3.4 × 10 25 cm −2 . Such a large column has a Thomson optical depth to electron scattering τ Th ≥ 23, sufficient to extinguish the optical and UV emission. The contradiction becomes even more acute if the gas is neutral since the opacity in the Lyman continuum becomes extremely large, τ Ly ≥ 2 × 10 8 , conflicting with the source detection below 912 Å. This apparent contradiction probably means that our lines-of-sight to the X-ray and to the UV emitting regions are different, such that the gas completely covers the compact X-ray source but only partially the more extended source of ultraviolet photons. An extended ( 1 ) X-ray source is detected ∼2 to the south-east of the QSO. Given its thermal spectrum and temperature (1.5 ≤ T ≤ 3.0 keV), it is probably a foreground (0.29 ≤ z ≤ 0.46) cluster of galaxies.

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“…In the traditional model, BAL outflows are equatorial disk winds that are ubiquitous in QSOs, and significant X-ray absorption is required to shield the outflow from overionization that would prohibit radiative acceleration (e.g., Murray et al 1995). Indeed, BAL QSOs (i.e., QSOs with BALs evident in their UV spectra) are relatively X-ray weak compared to non-BAL QSOs (e.g., Green et al 1995;Brandt et al 2000), apparently due to strong X-ray absorption (e.g., Green et al 2001;Gallagher et al 2001Gallagher et al , 2002, and references therein). Significant correlations have also been found between the degree of X-ray weakness and acceleration-dependent BAL properties such as outflow velocity and equivalent width, as might be expected for radiatively accelerated BAL outflows (e.g., Gallagher et al 2006;Gibson et al 2009).…”

Section: Introductionmentioning

confidence: 99%

X-Ray Insights Into the Physics of Mini-Bal Quasar Outflows

Gibson

Brandt

Gallagher

et al. 2009

ApJ

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We examine the ultraviolet and X-ray properties of 256 radio-quiet Sloan Digital Sky Survey quasars (QSOs) observed in X-rays with Chandra and/or XMM-Newton in order to study the relationship between QSOs with broad C iv absorption lines (BALs; width > 2000 km s −1 ) and those with C iv mini-BALs (here defined to have widths of 1000-2000 km s −1 ). Our sample includes 42 BAL and 48 mini-BAL QSOs. The relative X-ray brightness and hard spectral slopes of the mini-BAL population are, on average, intermediate between those of BAL and non-BAL QSOs, as might be expected if narrower and broader absorption line outflows are physically related. However, a significant population of mini-BALs has outflow velocities higher than would be expected for BAL QSOs of the same relative X-ray brightness. Consistently strong X-ray absorption is apparently not required to accelerate at least some mini-BALs to high outflow velocities. Assuming the mini-BAL features are correctly attributed to intrinsic C iv absorption, we suggest that their observed properties may be explained if mini-BALs are "seeds" that can be accelerated to form BALs when sufficient X-ray shielding is present. We also examine several QSOs with broad C iv absorption that have been recently reported to be unusually X-ray bright. Such cases are frequently mini-BAL QSOs, which, as a population, are generally brighter in X-rays than BAL QSOs. Pointed XMM-Newton observations also suggest that these sources (or unresolved neighbors) may have been previously observed in a high-flux state.

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The Soft X-Ray Properties of a Large Optical QSO Sample: ROSAT Observations of the Large Bright Quasar Survey

Cited by 131 publications

References 0 publications

Mass Loss from the Nuclei of Active Galaxies

Mass Loss from the Nuclei of Active Galaxies

Long observations of the BALQSO LBQS 2212-1759 with XMM-Newton

X-Ray Insights Into the Physics of Mini-Bal Quasar Outflows

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