http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-22T21:52:29Z http://hdl.handle.net/2307/273 <Title>A broad-line region origin for the iron Kα line in NGC 7213</Title> <Authors>Bianchi, Stefano; La Franca, Fabio; Matt, Giorgio; Guainazzi, Matteo; Jimenez Bailon, Elena; Longinotti, Anna Lia; Nicastro, Fabrizio; Pentericci, Laura</Authors> <Issue Date>2008-07</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society: Letters</Is part of> <Volume>389</Volume> <Pages>52-56</Pages> <Abstract>The X-ray spectrum of NGC 7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron Kα line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the broad-line region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra High-Energy Transmission Grating observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a full width at half-maximum (FWHM) = 2400+1100-600kms-1, in perfect agreement with the value measured for the broad component of the Hα, 2640+110-90kms-1. Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron Kα line is unambiguously produced in the BLR. We also confirmed the presence of two ionized iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionized gas. If this is the case, the blueshift of around 1000kms-1 of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.</Abstract> 2008-06-30T22:00:00Z http://hdl.handle.net/2307/391 <Title>The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]: no evidence of Eddington-limited sources</Title> <Authors>Lamastra, Alessandra; Bianchi, Stefano; Matt, Giorgio; Perola, Giuseppe Cesare; Barcons, X.; Carrera, F. J.</Authors> <Issue Date>2009-09</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>504</Volume> <Pages>73-79</Pages> <Abstract>Context. There have been recent claims that a significant fraction of type 2 AGN accrete close to or even above the Eddington limit. In type 2 AGN, the bolometric luminosity (L-b) is generally inferred from the [OIII] emission line luminosity (L-OIII). The key issue in estimating the bolometric luminosity in these AGN, is therefore to know the bolometric correction to be applied to L-OIII. A complication arises from the observed L-OIII being affected by extinction, most likely from dust within the narrow line region. The extinction-corrected [OIII] luminosity (L-OIII(c)) is a better estimator of the nuclear luminosity than L-OIII. However, only the bolometric correction to be applied to the uncorrected L-OIII has been evaluated so far. Aims. This paper is devoted to estimating the bolometric correction C-OIII = L-b/L-OIII(c) for deriving the Eddington ratios for the type 2 AGN in a sample of SDSS objects. Methods. We collected 61 sources from the literature with reliable estimates of both L-OIII(c) and X-ray luminosities (L-X). To estimate C-OIII, we combined the observed correlation between L-OIII(c) and L-Xwith the X-ray bolometric correction. Results. In contrast to previous studies, we found a linear correlation between L-OIII(c) and L-X. We estimated C-OIII using an earlier luminosity-dependent X-ray bolometric correction, and we found a mean value of C-OIII in the luminosity ranges log L-OIII = 38-40, 40-42, and 42-44 of 87, 142, and 454, respectively. We used it to calculate the Eddington ratio distribution of type 2 SDSS AGN at 0.3 < z < 0.4 and found that these sources are not accreting near their Eddington limit, contrary to previous claims.</Abstract> 2009-08-31T22:00:00Z http://hdl.handle.net/2307/393 <Title>A strong excess in the 20-100 kev emission of ngc 1365</Title> <Authors>Risaliti, G.; Braito, V.; Laparola, V.; Bianchi, Stefano; Elvis, M.; Fabbiano, G.; Maiolino, R.; Matt, Giorgio; Reeves, J.; Salvati, M.; Wang, J.</Authors> <Issue Date>2009-11</Issue Date> <Is part of>Astrophysical Journal Letters</Is part of> <Volume>705</Volume> <Pages>L1–L5</Pages> <Abstract>We present a new Suzaku observation of the obscured active galacticnucleus in NGC 1365, revealing an unexpected excess of X-rays above 20keV of at least a factor similar to 2 with respect to the extrapolationof the best-fitting 3-10 keV model. Additional Swift-BAT andIntegral-IBIS observations show that the 20-100 keV is concentratedwithin similar to 1.5 arcmin from the center of the galaxy, and is notsignificantly variable on timescales from days to years. A comparisonof this component with the 3-10 keV emission, which is characterized bya rapidly variable absorption, suggests a complex structure of thecircumnuclear medium, consisting of at least two distinct componentswith rather different physical properties, one of which covers >80% ofthe source with a column density N-H similar to 3-4x10(24) cm(-2). Analternative explanation is the presence of a double active nucleus inthe center of NGC 1365.</Abstract> 2009-10-31T23:00:00Z http://hdl.handle.net/2307/525 <Title>A relativistically smeared spectrum in the neutron star X-ray binary 4U1705-44: looking at the inner accretion disc with X-ray spectroscopy</Title> <Authors>Di Salvo, T.; D'Ai, A.; Iaria, R.; Burderi, L.; Dovciak, M.; Karas, V.; Matt, Giorgio; Papitto, A.; Piraino, S.; Riggio, A.; Robba, N. R.; Santangelo, A.</Authors> <Issue Date>2009-10</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society</Is part of> <Volume>398</Volume> <Pages>2022-2027</Pages> <Abstract>Iron emission lines at 6.4-6.97 keV, identified with fluorescent Kalpha transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in the innermost part of the accretion disc around a compact object. In this paper, we present a recent XMM-Newton observation of the X-ray burster 4U 1705-44, where we clearly detect a relativistically smeared iron line at about 6.7 keV, testifying with high statistical significance that the line profile is distorted by high-velocity motion in the accretion disc. As expected from disc reflection models, we also find a significant absorption edgeat about 8.3 keV; this feature appears to be smeared, and is compatible with being produced in the same region where the iron line is produced. From the line profile, we derive the physical parameters of the inner accretion disc with large precision. The line is identified with the Kalpha transition of highly ionized iron, Fe xxv, the inner disc radiusis R-in = 14 +/- 2 R-g (where R-g is the Gravitational radius, GM/c2), the emissivity dependence from the disc radius is r-2.27 +/- 0.08, theinclination angle with respect to the line of sight is i = 39 degrees+/- 1 degrees. Finally, the XMM-Newton spectrum shows evidences of other low-energy emission lines, which again appear broad and their profiles are compatible with being produced in the same region where the iron line is produced.</Abstract> 2009-09-30T22:00:00Z http://hdl.handle.net/2307/295 <Title>Variable partial covering and a relativistic iron line in NGC 1365</Title> <Authors>Risaliti, Guido; Miniutti, Giovanni; Elvis, Martin; Fabbiano, Giuseppina; Salvati, Marco; Baldi, Alessandro; Braito, Valentina; Bianchi, Stefano; Matt, Giorgio; Reeves, James; Soria, Roberto; Zezas, Andreas</Authors> <Issue Date>2009-05-01</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>696</Volume> <Pages>160-171</Pages> <Abstract>We present a complete analysis of the hard X-ray (2-10 keV) properties of the Seyfert galaxy NGC 1365, based on a 60 ks XMM-Newton observation performed in 2004 January. The two main results are as follows. (1) We detect an obscuring cloud with N-H similar to 3.5 x 10(23) cm(-2) crossing the line of sight in similar to 25 ks. This implies a dimension of the X-ray source not larger than a few 1013 cm and a distance of the obscuring cloud of the order of 1016 cm. Adopting the black hole mass M-BH estimated from the M-BH-velocity dispersion relation, the source size is D-S < 20R(G) and the distance and density of the obscuring clouds are R similar to 3000-10,000R(G) and n similar to 10(10) cm(-3), i.e., typical values for broad-line region clouds.(2) An iron emission line with a relativistic profile is detected with high statistical significance. A time-integrated fit of the line+continuum reflection components suggests a high iron abundance(approximately three times solar) and an origin of these components in the inner part (within similar to 10R(G)) of the accretion disk, in agreement with the small source size inferred from the analysis of the absorption variability.</Abstract> 2009-04-30T22:00:00Z http://hdl.handle.net/2307/296 <Title>Suzaku observations of the Circinus galaxy</Title> <Authors>Yang, Yuxuan; Wilson, Andrew S.; Matt, Giorgio; Terashima, Yuichi; Greenhill, Lincoln J.</Authors> <Issue Date>2009-01-20</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>691</Volume> <Pages>131-139</Pages> <Abstract>We report Suzaku observations of the active, Compton-thick Circinus galaxy. Observations were obtained with both the X-ray imaging spectrometer (XIS) and the hard X-ray detector (HXD). Below 10 keV, the nuclear spectrum is dominated by radiation reflected from cold dense gas of high column density, while above 13 keV the radiation is directly transmitted nuclear emission seen through a column density of similar or equal to 4 x 10(24) cm(-2). In the 0.2-10 keV band, the XIS spectrum is contaminated at 5% level by the brightest off-nuclear source in Circinus, but drops to 1% in the 5-10 keV band and is negligible at higher energies. We find no significant evidence for variability in the hard (> 12 keV) emission. Circinus is marginally detected with the HXD/GSO in the 50-100 keV band at 2.5 sigma level. We model the 3-70 keV band XIS+PIN spectra with four components: the Compton transmitted nuclear emission, the reflected nuclear emission, a soft power law (representing a combination of scattered nuclear emission, extended emission, and contamination by sources in the galaxy below a few keV), and emission lines. The hard nuclear power law is found to have a photon index Gamma(h) similar or equal to 1.6, very similar to the soft power law. The high-energy cutoff is E-C similar or equal to 49 keV. These results agree with those from BeppoSAX. An extrapolation of this model up to the GSO band shows good agreement with the GSO spectrum and supports our detection of Circinus up to similar or equal to 100 keV.</Abstract> 2009-01-19T23:00:00Z http://hdl.handle.net/2307/305 <Title>The XMM-Newton long look of NGC 1365: uncovering of the obscured X-raysource</Title> <Authors>Risaliti, Guido; Salvati, Marco; Elvis, Martin; Fabbiano, Giuseppina; Baldi, Alessandro; Bianchi, Stefano; Braito, Valentina; Guainazzi, Matteo; Matt, Giorgio; Miniutti, Giovanni; Reeves, James; Soria, Roberto; Zezas, Andreas</Authors> <Issue Date>2009</Issue Date> <Is part of>Monthly notices of the royal astronomical society</Is part of> <Volume>393</Volume> <Pages>L1</Pages> <Abstract>We present an analysis of the extreme obscuration variability observedduring an XMM-Newton 5-d continuous monitoring of the active galacticnuclei (AGN) in NGC 1365. The source was in a reflection-dominatedstate in the first similar to 1.5 d, then a strong increase in the 7-10keV emission was observed in similar to 10 h, followed by a symmetricdecrease. The spectral analysis of the different states clearly showsthat this variation is due to an uncovering of the X-ray source. Fromthis observation, we estimate a size of the X-ray source D-S < 10(13)cm, a distance of the obscuring clouds R similar to 10(16) cm and adensity n similar to 10(11) cm(-3). These values suggest that the X-rayabsorption/reflection originates from the broad-line region clouds.This is also supported by the resolved width of the iron narrow K alphaemission line, consistent with the width of the broad H beta line.</Abstract> 2008-12-31T23:00:00Z http://hdl.handle.net/2307/362 <Title>Unabsorbed Seyfert 2 galaxies: the case of 'naked' AGN</Title> <Authors>Panessa, F.; Carrera, F. J.; Bianchi, Stefano; Corral, A.; Gastaldello, F.; Barcons, X.; Bassani, L.; Matt, Giorgio; Monaco, L.</Authors> <Issue Date>2009-08-10</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society</Is part of> <Volume>398</Volume> <Pages>1951-1960</Pages> <Abstract>Hawkins reported on a class of 'naked' active galactic nuclei (AGN)characterized by strong amplitude optical brightness variability and the complete absence of broad emission lines in the optical spectrum. The variability suggests that the nucleus is seen directly, however the absence of broad lines contradicts the simple formulation of Unified Models for AGN. We present the results of quasi-simultaneous spectroscopic observations with XMM-Newton and New Technology Telescope(NTT) (La Silla) of two 'naked' AGN. We confirm the 'naked' nature of Q2131-427 for which no broad emission line components have been detected in the optical spectrum and its X-ray spectrum shows no signs of intrinsic absorption. The optical and X-ray mismatch in this source cannot be ascribed to a high nuclear dust-to-gas ratio and a Compton-thick nature is ruled out on the basis of the high F-X/F-[OIII] ratio. The broad-line region (BLR) may be completely absent in this source, possibly as a consequence of its low Eddington ratio. On the other hand, the optical spectrum of Q2130-431 shows H alpha and H beta broad emission line components, revealing the presence of a BLR. A mild X-ray absorption is expected in intermediate type 1.8 Seyfert galaxies like Q2130-431, however we put a very low upper limit on the column density (<2 x 10(20) cm(-2)), also the low Balmer decrement suggests that the BLR itself does not suffer from reddening. We propose that in this object the BLR is intrinsically weak, making a case of 'true' intermediate Seyfert galaxy. We also report on the X-ray detection of the Abell 3783 galaxy cluster in the XMM-Newton field of view of the Q2131-427 observation.</Abstract> 2009-08-09T22:00:00Z http://hdl.handle.net/2307/384 <Title>CAIXA: a catalogue of AGN in the XMM-Newton archive II. Multiwavelength correlations</Title> <Authors>Bianchi, Stefano; Bonilla, N. Fonseca; Guainazzi, Matteo; Matt, Giorgio; Ponti, Gabriele</Authors> <Issue Date>2009</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>501</Volume> <Pages>915-924</Pages> <Abstract>Aims. The availability of large amounts of multiwavelength data allows us to perform an extensive statistical analysis to look for correlations between different parameters of AGN. The physical implications of these correlations, when considered within the framework of current AGN models, can be enlightening in the resolution of the problems and the open issues which still characterise this class of sources. Methods. We presented CAIXA, a Catalogue of AGN in the XMM-Newton Archive, in a companion paper. It consists of radio-quiet X-ray unobscured sources, which cover a range in X-ray luminosities between L2-10keV = 2.0 x 10(41) and 3.9 x 10(46) erg s(-1), and in redshift from z = 0.002 to z = 4.520. Here, a systematic search for correlations between the X-ray spectral properties and the multiwavelength data was performed for the sources in CAIXA. All the significant (>99.9%confidence level) correlations are discussed along with their physical implications for current models of AGN. Results. Two main correlations are discussed in this paper: a) a very strong anti-correlation between the FWHM of the H beta optical line and the ratio between the soft and the hard X-ray luminosity. Although similar anti-correlations between optical line width and X-ray spectral steepness have already been discussed in the literature, we consider the formulation we present in this paper as more fundamental, as it links model-independent quantities. Coupled with a strong anti-correlation between the V to hard X-ray flux ratio and the H betaFHWM, it supports scenarios for the origin of the soft excess in AGN, which require strong suppression of the hard X-ray emission; b) a strong (and expected) correlation between the X-ray luminosity and the black hole mass. Its slope, flatter than 1, is consistent with Eddington ratio-dependent bolometric corrections. Moreover, we critically review through various statistical tests the role that distance biases play in the strong radio to X-ray luminosity correlation found in CAIXA and elsewhere; we conclude that only complete, unbiased samples should be used to draw observational constraints on the origin of radio emission in radio-quiet AGN.</Abstract> 2008-12-31T23:00:00Z http://hdl.handle.net/2307/325 <Title>How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582</Title> <Authors>Bianchi, Stefano; Piconcelli, Enrico; Chiaberge, Marco; Jimenez Bailon, Elena; Matt, Giorgio; Fiore, Fabrizio</Authors> <Issue Date>2009-04</Issue Date> <Is part of>Astrophysical Journal</Is part of> <Volume>695</Volume> <Pages>781-787</Pages> <Abstract>We present the results of a Suzaku monitoring campaign of the Seyfert 2galaxy, NGC 7582. The source is characterized by very rapid (ontimescales even lower than a day) changes of the column density of aninner absorber, together with the presence of constant componentsarising as reprocessing from a Compton-thick material. The best-fittingscenario implies important modifications to the zeroth-order view ofUnified Models. While the existence of a pc-scale torus is needed inorder to produce a constant Compton reflection component and an ironKa-emission line, in this Seyfert 2 galaxy this is not viewed along theline of sight. On the other hand, the absorption of the primarycontinuum is due to another material, much closer to the black hole,roughly at the distance of the broad-line region, which can produce theobserved rapid spectral variability. On top of that, the constantpresence of a 10(22) cm(-2) column density can be ascribed to thepresence of a dust lane, extended on a galactic scale, as previouslyconfirmed by Chandra. There is now mounting evidence that complexity inthe obscuration of active galactic nuclei (AGNs) may be the rule ratherthan the exception. We therefore propose to modify the UnificationModel, adding to the torus the presence of two furtherabsorbers/emitters. Their combination along the line of sight canreproduce all the observed phenomenology.</Abstract> 2009-03-31T22:00:00Z http://hdl.handle.net/2307/285 <Title>CAIXA: a catalogue of AGN in the XMM-Newton archive I. Spectral analysis</Title> <Authors>Bianchi, Stefano; Guainazzi, Matteo; Matt, Giorgio; Bonilla, N. Fonseca; Ponti, Gabriele</Authors> <Issue Date>2009-02</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>495</Volume> <Pages>421-430</Pages> <Abstract>Aims. We present CAIXA, a Catalogue of AGN In the XMM-Newton Archive.It consists of all the radio-quiet X-ray unobscured (N-H < 2 x 10(22)cm(-2)) active galactic nuclei (AGN) observed by XMM-Newton in targetedobservations, whose data are public as of March 2007. With its 156sources, this is the largest catalogue of high signal-to-noise X-rayspectra of AGN.Methods. All the EPIC pn spectra of the sources in CAIXA were extractedhomogeneously, and a baseline model was applied in order to derivetheir basic X-ray properties. These data are complemented bymultiwavelength data found in the literature: black hole masses, fullwidth half maximum (FWHM) of H beta, radio and optical fluxes.Results. Here we describe our homogeneous spectral analysis of theX-ray data in CAIXA and present all the results on the parametersadopted in our best-fit models.</Abstract> 2009-01-31T23:00:00Z http://hdl.handle.net/2307/286 <Title>Suzaku observation of the Phoenix galaxy</Title> <Authors>Matt, Giorgio; Bianchi, Stefano; Awaki, Hisamitsu; Comastri, Andrea; Guainazzi, Matteo; Iwasawa, Kazushi; Jimenez-Bailon, Elena; Nicastro, Fabrizio</Authors> <Issue Date>2009-03</Issue Date> <Is part of>Astronomy & Astrophysics</Is part of> <Volume>496</Volume> <Pages>653-658</Pages> <Abstract>Context. In recent years, several Seyfert 2 galaxies have beendiscovered that change state when observed in X-rays a few years apart,switching from Compton-thin to reflection-dominated or viceversa.Aims. We observed a member of this class of "Changing-look" sources,the Phoenix galaxy, with Suzaku, with the aim of better understandingthe nature of the variations.Methods. The Suzaku spectrum was analyzed, and the results comparedwith previous ASCA and XMM-Newton observations.Results. The source was caught in a Compton-thin state, as inXMM-Newton, but differently from ASCA. Comparing the Suzaku andXMM-Newton observations, a variation in the column density of theabsorber on a time scale of years is discovered. A similar change, buton much shorter time scales (i.e. ks) may also explain the count-ratevariations during the Suzaku observations. A soft excess is alsopresent, likely due to continuum and line emission from photoionizedcircumnuclear matter.</Abstract> 2009-02-28T23:00:00Z http://hdl.handle.net/2307/287 <Title>Disk reflection signatures in the spectrum of the bright z-source gx340+0</Title> <Authors>D'Ai, Antonino; Iaria, Rosario; Di Salvo, Tiziana; Matt, Giorgio; Robba, Natale</Authors> <Issue Date>2009-02</Issue Date> <Is part of>Astrophysical Journal Letters</Is part of> <Volume>693</Volume> <Pages>L1-L5</Pages> <Abstract>We present the preliminary results of a 50 ks long XMM-Newtonobservation of the bright Z-source GX 340+0. In this Letter, we focuson the study of a broad asymmetric emission line in the Fe K alphaenergy band, whose shape is clearly resolved and compatible with arelativistically smeared profile arising from reflection on a hotaccretion disk extending close to the central accreting neutron star.By combining temporal and spectral analysis, we are able to follow theevolution of the source along its horizontal branch. However, despite asignificant change in the continuum emission and luminosity, the lineprofile does not show any strong correlated variation. This broad lineis produced by recombination of highly ionized iron ( Fe xxv) at aninferred inner radius close to 13R(g), while the fit requires a highvalue for the outer disk radius. The inclination of the source isextremely well constrained at 35 degrees, while the emissivity index is-2.50.</Abstract> 2009-01-31T23:00:00Z