Simultaneous X-ray and optical spectroscopy of the Seyfert galaxy Mrk 993

Corral, A.; Barcons, X.; Carrera, Francisco J.; Ceballos, M. T.; Mateos, S.

doi:10.1051/0004-6361:20041690

Cited by 23 publications

(22 citation statements)

References 32 publications

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“…19 we show the unfolded spectra of these sources obtained with their best fit model (in all the cases a single power law). Several authors have found AGN with weak or no broad emission lines in their optical spectrum and with unabsorbed X-ray spectra (see for example Pappa et al 2001;Panessa et al 2002;Barcons et al 2003;Mateos et al 2005;Carrera et al 2004;Corral et al 2005). One possible explanation for these results is that the signal to noise of the spectra of these sources is not high enough to detect signatures of X-ray absorption (see e.g.…”

Section: Unabsorbed Type-2 Agnmentioning

confidence: 99%

“…The optical and X-ray observations of these sources have not been obtained simultaneously, and the X-ray absorption in these sources might have changed with time. Corral et al (2005) studied the hypothesis of spectral variability using simultaneous X-ray and optical observations of the Seyfert galaxy Mkn993. They found the source to be X-ray unabsorbed but in a type 1.9 optical.…”

Section: Unabsorbed Type-2 Agnmentioning

confidence: 99%

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XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

Mateos

Barcons

Carrera

et al. 2005

A&A

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110

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This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to 0.2−12 keV fluxes of ∼5 × 10 −15 erg cm −2 s −1 (flux limit of ∼6 × 10 −16 erg cm −2 s −1 in the 0.5−2 and 2−10 keV bands). At the time of the analysis, we had optical spectroscopic identifications for 60% of the sources, 46 being optical type-1 AGN and 28 optical type-2 AGN. Using a single power law model our sources' average spectral slope hardens at faint 0.5−2 keV fluxes but not at faint 2−10 keV fluxes. We have been able to explain this effect in terms of an increase in X-ray absorption at faint fluxes. We did not find in our data any evidence for the existence of a population of faint intrinsically harder sources. The average spectral slope of our sources is ∼1.9, with an intrinsic dispersion of ∼0.28. We detected X-ray absorption (F-test significance ≥95%) in 37% of the sources, ∼10% in type-1 AGN (rest-frame N H ∼ 1.6 × 10 21 −1.2 × 10 22 cm −2 ) and ∼77% (rest-frame N H ∼ 1.5 × 10 21 −4 × 10 23 cm −2 ) in type-2 AGN. Using X-ray fluxes corrected for absorption, the fraction of absorbed objects and the absorbing column density distribution did not vary with X-ray flux. Our type-1 and type-2 AGN do not appear to have different continuum shapes, but the distribution of intrinsic (rest-frame) absorbing column densities is different among both classes. A significant fraction of our type-2 AGN (5 out of 28) were found to display no substantial absorption (N H < 10 21 cm −2 ). We discuss possible interpretations to this in terms of Compton-thick AGN and intrinsic Broad Line Region properties. An emission line compatible with Fe Kα was detected in 8 sources (1 type-1 AGN, 5 type-2 AGN and 2 unidentified) with rest frame equivalent widths 120−1000 eV. However weak broad components can be easily missed in other sources by the relatively noisy data. The AGN continuum or intrinsic absorption did not depend on X-ray luminosity and/or redshift. Soft excess emission was detected in 18 objects, but only in 9 (including 4 type-1 AGN and 4 type-2 AGN) could we fit this spectral component with a black body model. The measured 0.5−2 keV luminosities of the fitted black body were not significantly different in type-1 and type-2 AGN, although the temperatures of the black body were slightly higher in type-2 AGN ( kT = 0.26 ± 0.08) than in type-1 AGN ( kT = 0.09 ± 0.01). For 9 sources (including 1 type-1 AGN and 3 type-2 AGN) a scattering model provided a better fit of the soft excess emission. We found that the integrated contribution from our sources to the X-ray background in the 2−7 keV band is softer (Γ = 1.5−1.6) than the background itself, implying that fainter sources need to be more absorbed.

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Section: Unabsorbed Type-2 Agnmentioning

confidence: 99%

Section: Unabsorbed Type-2 Agnmentioning

confidence: 99%

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

Mateos

Barcons

Carrera

et al. 2005

A&A

Self Cite

110

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“…Type 1 AGN with significant absorption have been found (Cappi et al 2006, hereafter C06, Mateos et al 2005, Fiore et al 2001a as well as type 2 AGN without X-ray absorption (Caccianiga et al 2004;Corral et al 2005;Barcons et al 2003;Panessa & Bassani 2002;Pappa et al 2001). In particular, it is not clear whether at very low luminosities the Appendix is only available in electronic form at http://www.edpsciences.org predictions of UM are still valid (Panessa & Bassani 2002;.…”

Section: Introductionmentioning

confidence: 99%

On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

Panessa

Bassani

Cappi

et al. 2006

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We investigate the relation between X-ray nuclear emission, optical emission line luminosities and black hole masses for a sample of 47 Seyfert galaxies. The sample, which has been selected from the Palomar optical spectroscopic survey of nearby galaxies (Ho et al. 1997a, ApJS, 112, 315), covers a wide range of nuclear powers, from L 2−10 keV ∼ 10 43 erg/s down to very low luminosities (L 2−10 keV ∼ 10 38 erg/s). Best available data from Chandra, XMM-Newton and, in a few cases, ASCA observations have been considered. Thanks to the good spatial resolution available from these observations and a proper modeling of the various spectral components, it has been possible to obtain accurate nuclear X-ray luminosities not contaminated by off-nuclear sources and/or diffuse emission. X-ray luminosities have then been corrected taking into account the likely candidate Compton thick sources, which are a high fraction (>30%) among type 2 Seyferts in our sample. The main result of this study is that we confirm strong linear correlations between 2-10 keV, [OIII]λ5007, H α luminosities which show the same slope as quasars and luminous Seyfert galaxies, independent of the level of nuclear activity displayed. Moreover, despite the wide range of Eddington ratios (L/L Edd ) tested here (six orders of magnitude, from 0.1 down to ∼10 −7 ), no correlation is found between the X-ray or optical emission line luminosities and the black hole mass. Our results suggest that Seyfert nuclei in our sample are consistent with being a scaled-down version of more luminous AGN.

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“…Spectral analyses have shown that the optical type vs. X-ray properties for most AGN generally agree with the predictions from AGN unification models. However, in recent years, the number of cases where the predictions from AGN unification models do not match the observations has increased substantially, as significant absorption has been detected in ∼10% type-1 AGN (Cappi et al 2006;Mateos et al 2005b;Akylas et al 2004) while type-2 AGN have been detected without any signatures of X-ray absorption (Panessa et al 2009;Bianchi et al 2008;Corral et al 2005;Panessa & Bassani 2002).…”

Section: Introductionmentioning

confidence: 99%

The XMM-NewtonWide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

Mateos¹,

Carrera

Page

et al. 2010

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Aims. We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2−10 keV (rest-frame) luminosities from ∼10 42 −10 45 erg s −1 and are detected up to redshift ∼4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods. We fitted the observed 0.2−12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results. We constrained the mean spectral index of the broad band X-ray continuum to Γ = 1.96 ± 0.02 with intrinsic dispersion σ Γ = 0.27 +0.01 −0.02 . The continuum becomes harder at faint fluxes and at higher redshifts and hard (2−10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in > ∼ 3% of our objects, with rest-frame column densities ∼a few ×10 22 cm −2 . The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is ∼36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT ∼ 100 eV and σ kT ∼ 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.

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Simultaneous X-ray and optical spectroscopy of the Seyfert galaxy Mrk 993

Cited by 23 publications

References 32 publications

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN

On the X-ray, optical emission line and black hole mass properties of local Seyfert galaxies

The XMM-NewtonWide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

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