Extended X-ray emission in the high-redshift quasar GB 1508+5714 at z= 4.3     

W. Yuan  A. C. Fabian  A. Celotti  P. G. Jonker 《Monthly notices of the Royal Astronomical Society》2003,346(1):L7-L10

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A hard X-ray constraint on the presence of an AGN in the ultraluminous infrared galaxy Arp 220     

K. Iwasawa  G. Matt  M. Guainazzi  A.C. Fabian 《Monthly notices of the Royal Astronomical Society》2001,326(3):894-900

We present X-ray results on the ultraluminous infrared galaxy Arp 220 obtained with BeppoSAX . X-ray emission up to 10 keV is detected. No significant signal is detected with the PDS detector in the higher energy band. The 2–10 keV emission has a flat spectrum (Γ∼1.7) , similar to M82, and a luminosity of ∼ 1×10⁴¹ erg s⁻¹ . A population of X-ray binaries may be a major source of this X-ray emission. The upper limit of an iron K line equivalent width at 6.4 keV is ≃600 eV. This observation imposes the tightest constraint so far on an active nucleus if present in Arp 220. We find that a column density of X-ray absorption must exceed 10²⁵ cm⁻² for an obscured active nucleus to be significant in the energetics, and the covering factor of the absorption should be almost unity. The underluminous soft X-ray starburst emission may need a good explanation, if the bolometric luminosity is primarily powered by a starburst.  相似文献   

A long hard look at MCG–6-30-15 with XMM–Newton– II. Detailed EPIC analysis and modelling     

S. Vaughan  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2004,348(4):1415-1438

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The effects of a Comptonizing corona on the appearance of the reflection components in accreting black hole spectra     

P.O. Petrucci  A. Merloni  A. Fabian  F. Haardt  E. Gallo 《Monthly notices of the Royal Astronomical Society》2001,328(2):501-510

We discuss the effects of a Comptonizing corona on the appearance of the reflection components, and in particular of the reflection hump, in the X-ray spectra of accreting black holes. Indeed, in the framework of a thermal corona model, we expect that some (or even all, depending on the coronal covering factor) of the reflection features should cross the hot plasma, and thus suffer Compton scattering, before being observed. We have studied in detail the dependence of these effects on the physical (i.e. temperature and optical depth) and geometrical (i.e. inclination angle) parameters of the corona, concentrating on the slab geometry. Owing to the smoothing and shifting towards high energies of the Comptonized reflection hump, the main effects on the emerging spectra appear above 100 keV. We have also investigated the importance of such effects on the interpretation of the results obtained with the standard fitting procedures. We found that fitting Comptonization models, taking into account Comptonized reflection, by the usual cut-off power law + unComptonized reflection model may lead to an underestimation of the reflection normalization and an overestimation of the high-energy cut-off. We discuss and illustrate the importance of these effects by analysing recent observational results, such as those of the galaxy NGC 4258. We also find that the Comptonizing corona can produce and/or emphasize correlations between the reflection feature characteristics (like the iron line equivalent width or the covering fraction) and the X-ray spectral index, similar to those recently reported in the literature. We also underline the importance of these effects when dealing with accurate spectral fitting of the X-ray background.  相似文献   

A comprehensive range of X-ray ionized-reflection models   总被引：1，自引：0，他引：1  

R. R. Ross  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2005,358(1):211-216

X-ray ionized reflection occurs when a surface is irradiated with X-rays so intense that its ionization state is determined by the ionization parameter  ξ∝ F / n   , where F is the incident flux and n the gas density. It occurs in accretion, on to compact objects including black holes in both active galaxies and stellar-mass binaries, and possibly in gamma-ray bursts. Computation of model reflection spectra is often time consuming. Here we present the results from a comprehensive grid of models computed with our code, which has now been extended to include what we consider to be all energetically important ionization states and transitions. This grid is being made available as an ionized-reflection model, reflion , for xspec .  相似文献   

The XMM–Newton view of the broad-line radio galaxy 3C 120     

D. R. Ballantyne  A. C. Fabian  K. Iwasawa 《Monthly notices of the Royal Astronomical Society》2004,354(3):839-850

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Jet–disc coupling through a common energy reservoir in the black hole XTE J1118+480     

Julien Malzac  rea Merloni  Andrew C. Fabian 《Monthly notices of the Royal Astronomical Society》2004,351(1):253-264

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An XMM–Newton observation of Ark 120: the X-ray spectrum of a 'bare' Seyfert 1 nucleus     

S. Vaughan  A. C. Fabian  D. R. Ballantyne  A. De Rosa  L. Piro  G. Matt 《Monthly notices of the Royal Astronomical Society》2004,351(1):193-205

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A softer look at MCG–6-30-15 with XMM–Newton     

A. K. Turner  A. C. Fabian  S. Vaughan  J. C. Lee 《Monthly notices of the Royal Astronomical Society》2003,346(3):833-840

We present the analysis and first results from the Reflection Grating Spectrometer (RGS) during the 320-ks XMM–Newton observation of the Seyfert 1 galaxy MCG–6-30-15. The spectrum is marked by a sharp drop in flux at 0.7 keV which has been interpreted by Branduardi-Raymont et al. using RGS spectra from an earlier and shorter observation as the blue wing of a strong relativistic O  viii emission line and by Lee et al. using a Chandra spectrum as due to a dusty warm absorber. We find that the drop is well explained by the Fe  i L_2,3 absorption edges and obtain reasonable fits over the 0.32–1.7 keV band using a multizone, dusty warm absorber model constructed using the photoionization code cloudy . Some residuals remain which could be due to emission from a relativistic disc, but at a much weaker level than from any simple model relying on relativistic emission lines alone. A model based on such emission lines can be made to fit if sufficient (warm) absorption is added, although the line strengths exceed those expected. In order to distinguish further whether the spectral shape is dominated by absorption or emission, we examined the difference spectrum between the highest and lowest flux states of the source. The EPIC pn data indicate that this is a power law in the 3–10 keV band which, if extrapolated to lower energies, reveals the absorption function acting on the intrinsic spectrum, provided that any emission lines do not scale exactly with the continuum. We find that this function matches our dusty warm absorber model well if the power law steepens below 2 keV. The soft X-ray spectrum is therefore dominated by absorption structures, with the equivalent width of any individual emission lines in the residuals being below approximately 30 eV.  相似文献   

Fields and filaments in the core of the Centaurus cluster     

G. B. Taylor  A. C. Fabian  G. Gentile  S. W. Allen  C. Crawford  J. S. Sanders 《Monthly notices of the Royal Astronomical Society》2007,382(1):67-72

We present high-resolution images of the Faraday rotation measure (RM) structure of the radio galaxy PKS 1246−410 at the centre of the Centaurus cluster. Comparison with Hα-line and soft X-ray emission reveals a correspondence between the line-emitting gas, the soft X-ray emitting gas, regions with an excess in the RM images and signs of depolarization. Magnetic field strengths of 25 μG, organized on scales of ∼1 kpc and intermixed with gas at a temperature of 5 × 10⁶ K with a density of ∼0.1 cm⁻³, can reproduce the observed RM excess, the depolarization and the observed X-ray surface brightness. This hot gas may be in pressure equilibrium with the optical line-emitting gas, but the magnetic field strength of 25 μG associated with the hot gas provides only 10 per cent of the thermal pressure and is therefore insufficient to account for the stability of the line-emitting filaments.  相似文献