High‐Energy Break and Reflection Features in the Seyfert Galaxy MCG +8‐11‐11

Grandi, P.; Haardt, Francesco; Ghisellini, G.; Grove, Eric; Maraschi, L.; Urry, C. Megan

doi:10.1086/305557

Cited by 13 publications

(21 citation statements)

References 37 publications

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“…lower limit found with the Suzaku data only, is also in agreement with that measured by BeppoSAX (170 +300 −80 keV: Perola et al 2000) and only marginally inconsistent with OSSE (270 +90 −70 keV: Grandi et al 1998).…”

Section: The Broad-band Fitsupporting

confidence: 89%

“…In the past 15 years, MCG+8-11-11 has been observed in the X-rays by ASCA (simultaneously with OSSE, Grandi et al 1998), BeppoSAX (Perola et al 2000), and XMM-Newton (Matt et al 2006). Despite significant flux variability (a factor 3 between ASCA and the present Suzaku observation), there is no clear evidence of variations of the spectral shape of the source.…”

Section: Comparison With Previous Observationsmentioning

confidence: 57%

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The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11

Bianchi

Angelis

Matt

et al. 2010

A&A

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Aims. Evidence is mounting that the main ingredients of the unification models of active galactic nuclei may behave differently from expectations, and be intimately related to fundamental physical parameters. The availability of high signal-to-noise broad-band X-ray spectra provides us with the opportunity to study in detail all the contributions from the materials invoked in these models, and infer their general properties, including whether their presence or absence is related to other quantities. Methods. We present a long (100 ks) Suzaku observation of one of the X-ray brightest AGN, MCG+8-11-11. These data are complemented with the 54-month Swift BAT spectrum, allowing us to perform a broad-band fit to the 0.6-150 keV range. Results. The fits performed in the 0.6-10 keV band provide results consistent with those of a a previous XMM-Newton observation, i.e. a lack of a soft excess, warm absorption along the line of sight, a large Compton reflection component (R 1), and an absence of a relativistic component of the neutral iron Kα emission line. However, when the PIN and Swift BAT data are included, the reflection amount drops significantly (R 0.2−0.3), and a relativistic iron line is required, the latter being confirmed by a phenomenological analysis in a restricted energy band (3-10 keV). When a self-consistent model is applied to the whole broad-band data, the observed reflection component appears to be entirely associated with the relativistic component of the iron Kα line. Conclusions. The implied scenario, though strongly model-dependent, requires that all the reprocessing spectral components from Compton-thick material be associated with the accretion disc, and no evidence of a classical pc-scale torus is found. The narrow core of the neutral iron Kα line is therefore produced in Compton-thin material, such as the BLR, similarly to what is found in another Seyfert galaxy, NGC 7213, but with the notable difference that MCG+8-11-11 presents spectral signatures from an accretion disc. The very low accretion rate of NGC 7213 could explain the lack of relativistic signatures in its spectrum, but the absence of the torus in both sources is more difficult to explain, since their luminosities are comparable, and their accretion rates are completely different.

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Section: The Broad-band Fitsupporting

confidence: 89%

Section: Comparison With Previous Observationsmentioning

confidence: 57%

The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11

Bianchi

Angelis

Matt

et al. 2010

A&A

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“…The ASCA (Grandi et al 1998) and BeppoSAX (Perola et al 2000) data were well-fitted by a fairly standard model composed of a powerlaw, a warm absorber, a Compton reflection component, and an Fe Kα line. −0.06 × 10 22 cm −2 ) with the temperature of the material fixed at 10 6 K, and an absorption edge at 0.74 keV corresponding to He-like oxygen.…”

Section: Mcg+8-11-11mentioning

confidence: 98%

X-ray spectral properties of Seyfert galaxies and the unification scheme

Singh

Shastri

Risaliti

2011

A&A

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Context. The unification scheme of Seyfert galaxies predicts that the observed differences between types 1 and 2 Seyfert galaxies are solely due to the differing orientations of the toroidal-shaped obscuring material around AGN. The observed X-ray spectra of Seyfert type 2s compared to type 1s are expected to be affected by higher absorbing column density owing to the edge-on view of the obscuring torus. Aims. We study the 0.5-10 keV X-ray spectral properties of Seyfert type 1s and type 2s with the aim of testing the predictions of Seyfert unification scheme in the X-ray regime. Methods. We use an optically selected Seyfert sample in which type 1s and type 2s have matched distributions in parameters that are independent of the orientation of AGN and the host galaxy. Results. The 0.5-10 keV XMM-Newton pn X-ray spectra of Seyfert galaxies are in general best fitted with a model that consists of (i) an absorbed powerlaw; (ii) a narrow Gaussian fitted to the Fe Kα emission line; and (iii) an often seen soft-excess component characterized by either a thermal plasma model with temperature kT ∼ 0.1-1.0 keV or a steep powerlaw or both. The 2.0-10 keV hard X-ray continuum emission in several Seyfert type 2s is dominated by reflection and suggests the Compton-thick obscuration. Results of the statistical comparison between the distributions of (i) the observed X-ray luminosities in the soft (0.5-2.0 keV) and hard (2.0-10.0 keV) bands; (ii) the X-ray absorbing column densities; (iii) the equivalent widths of Fe Kα line; and (iv) the flux ratios of hard X-ray to [OIII] λ5007 Å, for the two Seyfert subtypes are consistent with the obscuration and orientation-based unification scheme.

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“…Some of the past studies of MCG +8−11−11 reported the presence of a strong reflection component R = 1−2.5 [5,8,12,13]. Yet, a good statistical constrain was only obtained with XMMNewton data but limited at energies below 10 keV [5] or combined with low effective exposure ISGRI data ( [13], corresponding to the first point in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…As simultaneously the veto system of the telescope registered a strong gamma-ray flux, Perotti et al have suggested that the 112 keV line could be due to double-Compton scattering of a 511 keV line source incident on an external cloud. Later CGRO/OSSE observations did not detect the line with an upper limit flux of 0.9 × 10 −4 ph cm −2 s −1 [8] implying that the line, if present, is variable. In the ISGRI data presented here, we do not detect any line at 112 keV.…”

Section: The 112 Kev Linementioning

confidence: 94%

Compton processes in the bright AGN MCG +8-11-11

Soldi¹,

Beckmann²,

Gehrels³

et al. 2011

Proceedings of 8th INTEGRAL Workshop “The Restless Gamma-Ray Universe” — PoS(INTEGRAL 2010)

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We present preliminary results on the hard X-ray emission properties of the Seyfert 1.5 galaxy MCG +8−11−11, as observed by INTEGRAL and SWIFT. All the INTEGRAL IBIS/ISGRI data available up to October 2009 have been analysed together with two SWIFT/XRT snapshot observations performed in August and October 2009, quasi-simultaneously to INTEGRAL pointed observations of MCG +8−11−11. No correlation is observed between the hard Xray flux and the spectral slope, while the position of the high-energy cut-off is found to have varied during the INTEGRAL observations. This points to a change in the temperature of the Comptonising medium from a minimum value of kT e = 30 − 50 keV to values larger than 100-150 keV. There is no significant detection of Compton reflection, with a 3σ upper limit of R < 0.2, and no line has been detected at 112 keV, as previously claimed from HEAT observations (F 112 keV < 2.4 × 10 −4 ph cm −2 s −1 ). The variability behaviour of MCG +8−11−11 is found to be similar to that shown by IC 4329A, with different temperatures of the electron plasma for similar flux levels of the source, while other bright Seyfert galaxies present different variability patterns at hard X-rays, with spectral changes correlated to flux variations (e.g. NGC 4151).

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High‐Energy Break and Reflection Features in the Seyfert Galaxy MCG +8‐11‐11

Cited by 13 publications

References 37 publications

The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11

The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11

X-ray spectral properties of Seyfert galaxies and the unification scheme

Compton processes in the bright AGN MCG +8-11-11

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