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PG1535+547 is a bright NLS1 galaxy, whose high energy emission shows strong variability in shape and flux. ROSAT data classified it as soft X-ray weak QSO (objects whose X-ray-to-optical flux ratio is smaller than in typical QSO): their X-ray spectra are often characterized by highly ionized, complex absorbers and/or reflection from the disk, whose relative importance is currently debated. In both cases, the presence of such features implies that we are looking at matter located in the innermost regions of the AGN. In this paper we want to clarify the nature of the X-ray emission of PG1535+547, and constrain the physical properties of regions where the emission originates. We present new XMM observations, from which we obtained 2 spectra separated by about 1 week, that we compare with a previous XMM observation. The data support the complex and variable nature of the X-ray emission. The broad band flux increases by a factor ~2.3 in 3 years, and then decreases by a factor ~1.3 in about 1 week. In the new EPIC spectra strong absorption features at E<3keV and a complex spectral shape in the Fe line energy range are evident, coupled with a drop in the emission at higher energies. We describe all the states assuming either a warm absorber plus a relativistically blurred ionized reflection, or a two-phase warm absorber partially covering the source plus a scattered component. The variability is ascribed to the warm absorbers, that vary their physical properties on timescales of years and days. In the reflection scenario all the states require a high fraction of reflection. The strong variability in the X-ray band opposed to a more constant optical emission implies that PG1535+547 can not actually be classified as a soft X-ray weak AGN., Comment: 14 pages, 7 figures, A&A latex manuscript; accepted for publication in Astronomy & Astrophysics

Simbol-X is a French-Italian mission, with a participation of German laboratories, for X-ray astronomy in the wide 0.5-80 keV band. Taking advantage of emerging technology in mirror manufacturing and spacecraft formation flying, Simbol-X will push grazing incidence imaging up to ~80 keV, providing an improvement of roughly three orders of magnitude in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. This will open a new window in X-ray astronomy, allowing breakthrough studies on black hole physics and census and particle acceleration mechanisms. We describe briefly the main scientific goals of the Simbol-X mission, giving a few examples aimed at highlighting key issues of the Simbol-X design., Comment: Proc. of the workshop "Simbol-X: The hard X-ray universe in focus", Bologna 14-16 May, 2007

The detection of red/blue-shifted iron lines in the spectra of astronomical X-ray sources is of great importance, as it allows to trace the environment around compact objects, like black holes in AGNs. We report on extensive simulations to test the Simbol-X capability of detecting such spectral features, focusing on the low energy detector (0.5-30 keV)., Comment: 2 pages, 2 figures, to appear in proceedings of "Simbol-X: the hard X-ray Universe in focus", held in Bologna (Italy), May 14-16, 2007

Chandra and XMM-Newton X-ray observations are accumulating evidence for massive, high velocity outflows in Seyfert galaxies and quasars, most likely originating very close to the central supermassive black hole. These results are offering new potential to probe the launching regions of relativistic jets/outflows, and to quantify their feedback impact on the host galaxy and/or cluster of galaxies. The most important signature of these phenomena is the detection of blueshifted absorption lines of highly ionized iron at energies usually greater than ~7 keV. The lack of sensitivity of present day X-ray observatories at these energies gives rise to bias against the detection of more ``extreme'' outflows, with highest velocity and ionization, which would be blueshifted at energies >10 keV. Thus, simulations with Simbol-X were carried out to test its capability of detecting absorption lines/edges between 5-20 keV, in order to probe the dynamics (i.e. measurement of velocity variations) of the absorbing gas, as well as the highest (up to relativistic speeds) velocity and ionization components. We found that the unprecedented sensitivity of Simbol-X between 5-30 keV is a great opportunity to obtain important improvements in this research field., Comment: 5 pages, 6 figures, to appear in proceedings of "Simbol-X: the hard X-ray Universe in focus", held in Bologna (Italy), May 14-16, 2007

We present an observation of XMM-Newton that unambiguously reveals the ``Seyfert 2'' nature of the Broad Line Radio Galaxy 3C 445. For the first time the soft excess of this source has been resolved. It consists of unobscured scattered continuum flux and emission lines, likely produced in a warm photoionized gas near the pole of an obscuring torus. The presence of circumnuclear (likely stratified) matter is supported by the complex obscuration of the nuclear region. Seventy percent of the nuclear radiation (first component) is indeed obscured by a column density ~4*10^{23} cm^{-2}, and 30 % (second component) is filtered by ~7* 10^{22} cm^{-2}. The first component is nuclear radiation directly observed by transmission through the thicker regions. The second one is of more uncertain nature. If the observer has a deep view into the nucleus but near the edge of the torus, it could be light scattered by the inner wall of the torus and/or by photoionized gas within the Broad Line Region observed through the thinner rim of the circumnuclear matter., Comment: MNRAS Letters, in press

It has been suggested that X-ray observations of rapidly variable Seyfert galaxies may hold the key to probe the gas orbital motions in the innermost regions of accretion discs around black holes and, thus, trace flow patterns under the effect of the hole strong gravitational field. We explore this possibility analizing XMM-Newton observations of the seyfert 1 galaxy NGC 3783. A detiled time-resolved spectral analysis is performed down to the shortest possible time-scales (few ks) using "excess maps" and cross-correlating light curves in different energy bands. In addition to a constant core of the Fe K alpha line, we detected a variable and redshifted Fe K alpha emission feature between 5.3-6.1 keV. The line exhibits a modulation on a time-scale of 27 ks that is similar to and in phase with a modulation of the 0.3-10 keV source continuum. The time-scale of the correlated variability of the redshifted Fe line and continuum agrees with the local dynamical time-scale of the accretion disc at 10 r_g around a black hole of 10^7 M_sun. Given the shape of the redshfted line emission and the overall X-ray variability pattern, the line is likely to arise from the relativistic region near the black hole., Comment: 8 pages, 7 figures, to be published in Astronomy and Astrophysics

We present the results of the correlation between the nuclear 2-10 keV X-ray and radio (at 2cm, 6cm and 20cm) luminosities for a well defined sample of local Seyfert galaxies. We use a sample of low luminosity radio galaxies (LLRGs) for comparison. In both Seyfert and LLRGs samples, X-ray and radio luminosities are significantly correlated over 8 orders of magnitude, indicating that the X-ray and radio emission sources are strongly coupled. Moreover, both samples show a similar regression slope, L(X)$\propto$ L(R)^(0.97), but Seyfert galaxies are three orders of magnitude less luminous in the radio band than LLRGs. This suggests that either similar physical mechanisms are responsible for the observed emission or a combination of different mechanisms ends up producing a similar correlation slope. Indeed, the common belief for LLRG is that both the X-ray and radio emission are likely dominated by a relativistic jet component, while in Seyfert galaxies the X-ray emission probably arises from a disk-corona system and the radio emission is attributed to a jet/outflow component. We investigate the radio loudness issue in the two samples and find that the Seyfert galaxies and the LLRGs show a different distribution of the radio loudness parameters. No correlation is found between the luminosity and the radio loudness, however the latter is related to the black hole mass and anti-correlated with the Eddington ratio. The dichotomy in the radio loudness between Seyfert and LLRG observed down to low Eddington ratios, L(2-10)/L(Edd) $\sim$ 10^(-8), does not support the idea that the origin of the radio loudness is due to a switch in the accretion mode., Comment: 11 pages, 7 figures, accepted for publication on A&A including referee's comments

We investigate the relation between the X-ray nuclear emission, optical emission line, radio luminosity and black hole mass for a sample of nearby Seyfert galaxies. Strong linear correlations between the 2-10 keV and [OIII], radio luminosities have been found, showing the same slopes found in quasars and luminous Seyfert galaxies, thus implying independence from the level of nuclear activity displayed by the sources. 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, optical emission lines, radio luminosities and the black hole mass. These results suggest that low luminosity Seyfert galaxies are a scaled down version of luminous AGN and probably are powered by the same physical processes., Comment: 6 pages, 3 figures, contributed talk presented at the Workshop "The multicoloured landscape of compact objects and their explosive origin", Cefalu' (Sicily), 11-24 June 2006, to be published by AIP

The analysis of hard X-ray features in XMM-Newton data of the bright Sy 1 galaxy Mrk 335 is reported here. The presence of a broad, ionised iron K alpha emission line in the spectrum, first found by Gondoin et al.(2002), is confirmed. The broad line can be modeled successfully by relativistic accretion disc reflection models. Regardless of the underlying continuum we report, for the first time in this source, the detection of a narrow absorption feature at the rest frame energy of ~5.9 keV. If the feature is identified with a resonance absorption line of iron in a highly ionised medium, the redshift of the line corresponds to an inflow velocity of ~0.11-0.15 c. Preliminary results from a longer (100ks) exposure are also presented., Comment: Conference proceedings to appear in "The Central Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San Francisco: ASP)

We report results from the XMM-Newton observation of IRAS 13197-1627, a luminous IR galaxy with a Seyfert 1.8 nucleus. The hard X-ray spectrum is steep and is absorbed by Compton-thin neutral gas. We detect an Fe emission line at 6.4 keV, consistent with transmission through the absorber. The most striking result of our spectral analysis is the detection of a dominant X-ray reflection component and broad Fe line from the inner accretion disc. The reflection-dominated hard X-ray spectrum is confirmed by the strong Compton hump seen in a previous BeppoSAX observation and could be the sign that most of the primary X-rays are radiated from a compact corona (or e.g. base of the jet) within a few gravitational radii from the black hole. We also detect a relatively strong absorption line at 6.81 keV which, if interpreted as Fe xxv resonant absorption intrinsic to the source, implies an outflow with velocity of about 5000 km/s. In the soft energy band, the high-resolution RGS and the CCD-resolution data show the presence of both photo-ionized gas and thermal plasma emission, the latter being most likely associated with a recent starburst of 15-20 solar masses per year., Comment: accepted for publication in MNRAS

We present an analysis of all SAX observations of NGC 4151. This source was observed 5 times from 1996 to 2001 with durations ranging from a day to four days. The intrinsic continuum, is absorbed at low energies by a complex system: a cold patchy absorber plus a warm uniform screen photoionized by the central continuum. We find that this dual absorber is the main driver of the observed variability, up to a factor of eight, at 3 keV. In particular the covering fraction of the cold absorber changes on time scales of the order of a day, supporting its association with the Broad Line Region. The column density of the warm gas varies on a longer time scale (months to year). Some of the small amplitude spectral variability above 10 keV can be explained with an intrinsic variation (\Delta\Gamma~0.2).The flux below 1 keV remains constant confirming an extended origin. Its spectrum is reproduced by a combination of a thermal component and a power law with the same slope as the intrinsic continuum but with an intensity a few per cent. A Compton reflection component is significantly detected in 1996 (averaged value of \Omega/2\pi ~0.4), with intensity decreasing on time scale of year, and it desappears in 2000 and 2001. The long time scale of variations argues for an association with an optically thick torus at a distance of few light years. An iron line was detected in all spectra. Its energy is consistent with fluorescence by cold iron. We find that the line is variable. Its behaviour is reproduced by a variable component proportional to the level of the reflection flux plus a constant component. The flux of the latter is consistent with the extended line emission observed by Chandra. We conclude that the first component is likely arising from the torus and the second is produced in the extended Narrow Line Region., Comment: Accepted for publication in A&A

We present the analysis of X-ray spectral varability made on a sample of 7 Seyfert 1 bright galaxies, using XMM-Newton data. From the "XMM-Newton Science Archive" we selected those bright Seyfert 1 showing one or more prominent flares in their 2-10 keV light curves. For each of them we extracted spectra in 3 different time intervals: before, during and after the flare. We fitted them with a simple power law and then shifted a narrow emission and absorption line template across the 2.5-10 keV data, in order to investigate the presence of line-like features with a confidence level greater than 99%. Some highly significant features were detected in 3 out of 7 sources studied. In particular, the 3 sources, namely PG 1211+143, NGC 4051 and NGC 3783, showed the presence of a variable emission feature in the 4.5-5.8 keV band, characterized by an increase of its intensity after the flare peak. Because of the observed variability pattern, this feature seems to be ascribable to a reverbered redshifted relativistic component of the Fe K line., Comment: 4 pages, 9 figures, accepted for publication in Astronomische Nachrichten, proceedings of the ESAC Workshop "Variable and Broad Iron Lines around Black Holes"

Current, accumulating evidence for (mildly) relativistic blue- and red-shifted absorption lines in AGNs is reviewed. XMM-Newton and Chandra sensitive X-ray observations are starting to probe not only the kinematics (velocity) but also the dynamics (accelerations) of highly ionized gas flowing in-and-out from, likely, a few gravitational radii from the black hole. It is thus emphasized that X-ray absorption-line spectroscopy provides new potential to map the accretion flows near black holes, to probe the launching regions of relativistic jets/outflows, and to quantify the cosmological feedback of AGNs. Prospects to tackle these issues with future high energy missions are briefly addressed., Comment: 8 pages and 9 figures, to appear in Astronomical Notes (Astron. Nachr.), issue number 2006/10

We report the XMM-Newton detection of a moderately bright X-ray source superimposed on the outer arms of the inactive spiral galaxy MCG-03-34-63 (z=0.0213). It is clearly offset from the nucleus (by about 19'') but well within the D25 ellipse of the galaxy, just along its bar axis. The field has also been observed with the HST enabling us to compute a lower limit of > 94 on the X-ray to optical flux ratio which, together with the X-ray spectrum of the source, argues against a background AGN. On the other hand, the detection of excess X-ray absorption and the lack of a bright optical counterpart argue against foreground contamination. Short-timescale variability is observed, ruling out the hypothesis of a particularly powerful supernova. If it is associated with the apparent host galaxy, the source is the most powerful ULX detected so far with a peak luminosity of 1.35x10^41 erg/s in the 0.5-7 keV band. If confirmed by future multi-wavelength observations, the inferred bolometric luminosity (about 3x10^41 erg/s) requires a rather extreme beaming factor (larger than 115) to accommodate accretion onto a stellar-mass black hole of 20 solar masses and the source could represent instead one of the best intermediate-mass black hole candidate so far. If beaming is excluded, the Eddington limit implies a mass of >2300 solar masses for the accreting compact object., Comment: MNRAS Letters in press; minor correction at the end of Section2

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, Filippenko & Sargent 1997), 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]\lambda5007, H_{alpha} 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., Comment: 17 pages, 10 figures, accepted by Astronomy and Astrophysics

We study the X-ray spectral variability of the Narrow Line Seyfert 1 galaxy NGC 4051 as observed during two XMM-Newton observations. The data show evidence for a neutral and constant reflection component and for constant emission from photoionized gas, which are included in all spectral models. The nuclear emission can be modelled both in terms of a ``standard model'' (pivoting power law plus a black body component for the soft excess) and of a two--component one (power law plus ionized reflection from the accretion disc). The standard model results indicate that the soft excess does not follow the standard black body law. Moreover, although the spectral slope is correlated with flux, which is consistent with spectral pivoting, the hardest photon indexes are so flat as to require rather unusual scenarios. These problems can be solved in terms of the two-component model in which the soft excess is not thermal, but due to the ionized reflection component. The variability of the reflection component from the inner disc closely follows the predictions of the light bending model, suggesting that most of the primary nuclear emission is produced in the very innermost regions, only a few gravitational radii from the central black hole. (abridged), Comment: accepted for publication in MNRAS

In the recent literature on AGNs it has been often reported that spectra of Seyfert 1 Galaxies show resonant absorption lines of Fe K which are redshifted from the rest frame position. Such lines are often found with marginal significance but, if real, could potentially open up new avenues to study the circumnuclear gas in the black hole environment. It is also extremely important to take them into account in X-ray spectral analysis because of the influence they have in the correct estimation of spectral parameters, Fe K alpha line in primis. An XMM-Newton observation of Mrk 335 is reported here as a case study: a narrow feature has been detected at 5.9 keV, i.e. with a redshift corresponding to a velocity of v ~ 0.15c. Preliminary results on the statistical significance of narrow absorption and emission lines in a sample of PG QSOs observed by XMM-Newton are also included., Comment: 6 pages, 4 figures. To appear in the proceedings of "The X-Ray Universe 2005" conference, 2005 Sept 26-30, El Escorial, Madrid, Spain

Results obtained from an X-ray spectral survey of nearby Seyfert galaxies using XMM--Newton are reported. The sample was optically selected, well defined, complete in B mag, and distance limited: it consists of the nearest (D<22 Mpc) 27 Seyfert galaxies (9 of type 1, 18 of type 2) taken from the Ho et al. (1997) sample. This is one of the largest atlases of hard X-ray spectra of low-L active galaxies ever assembled. All nuclear sources except two Sey 2s are detected between 2-10 keV, half for the first time ever, and average spectra are obtained for all of them. Nuclear luminosities reach values down to 10**38 erg/s. The shape of the distribution of X-ray parameters is affected by the presence of Compton-thick objects (> 30% among type 2s). The latter have been identified either directly from their intense FeK line and flat X-ray spectra, or indirectly with flux diagnostic diagrams which use isotropic indicators. After taking into account these highly absorbed sources, we find that (i) the intrinsic X-ray spectral properties (i.e., spectral shapes and luminosities above 2 keV) are consistent between type 1 and type 2 Sey, as expected from ``unified models'', (ii) Sey galaxies as a whole are distributed fairly continuously over the entire range of Nh, between 10**20 and 10**25 cm**-2, and (iii) while Sey 1s tend to have lower Nh and Sey 2s tend to have the highest, we find 30% and 10% exceptions, respectively. Overall the sample well represents the average intrinsic X-ray spectral properties of nearby AGN, including a proper estimate of the distribution of their absorbing columns. Finally, we conclude that, with the exception of a few cases, the present study agrees with predictions of unified models of Sey galaxies, and extends their validity down to very low luminosities., Comment: 23 pages, 4 tables, 4 figures, 2 Appendices with 27 source spectra and notes, to be published in the Astronomy & Astrophysics Journal

Evidence for both red- and blue-shifted absorption lines due to ionized Fe in the X-ray spectrum of the Seyfert 1 galaxy Mrk 509 are reported. These features appear to be transient on time-scales as short as ~20 ks, and have been observed with two different satellites, BeppoSAX and XMM-Newton. The red- and blue-shifted lines are found at E~5.5 keV and ~8.1-8.3 keV (rest-frame), respectively. The first is seen in one out of six BeppoSAX observations, the latter is seen by both satellites. Under the assumption that the absorption is due to either H- or He-like Iron, the implied velocities for the absorbing matter are v~0.15-0.2 c, in both outward and inward directions. An alternative explanation in terms of gravitational red-shift for the ~5.5 keV line cannot be ruled out with the current data. We argue, however, that the temporal patterns and sporadic nature of the lines are more easily reconciled with models which predict important radial motions close to the central black hole, such as the ``aborted jet'' model, the ``thundercloud'' model, or magneto-hydrodynamical models of jets and accretion-disks., Comment: 9 pages, 3 tables, 10 figures, accepted for publication in A&A

We present a 30 ks XMM-Newton observation of the z = 2.35 Type II radio quiet quasar RX J1343.4+0001. These data provide the first good quality X-ray spectrum for this object. We measured a continuum slope Gamma = 1.85+/-0.10 with only an upper limit on the column density of the absorbing material of Nh(z) <~ 10^22 cm^-2 as well as an Fe Kalpha emission line at the 3 sigma confidence level. We do not find therefore a highly absorbed object nor a truly flat spectrum as suggested on the basis of previous less sensitive ROSAT and ASCA measurements. The Nh(z) upper limit is fully consistent with the optical extinction 3

One of the least biased complete Seyfert sample available to date has been considered to perform an X-ray survey using the capabilities of XMM-Newton and Chandra satellites. The X-ray nuclear luminosities obtained have been used to perform a multi-wavelength analysis as a powerfull tool in the identification of heavily obscured objects. The new X-ray data, together with highest quality nuclear fluxes available from the radio to the optical band, allow us to obtain nuclear Spectral Energy Distributions (SEDs) for type 1 and type 2 objects in our sample. The results obtained from the analysis of the SED have been discussed in the framework of Unified Models., Comment: 8 pages, 8 figures. Proceedings of the VI Italian Conference on Active Galactic Nuclei. See http://www.arcetri.astro.it/~agn6/proceedings/

The first systematic study of the serendipitous X-ray source density around 10 high z (0.242sigma per field, and >5sigma overall) only on scale of 8'X8' and peculiar to cluster fields. The blank field fluctuations, i.e. the most sensitive measurements to date of the X-ray cosmic variance on this scale, indicate (1 sigma) variations within ~15-25% around the average value. The first marginal evidence that these overdensities increase with cluster redshift is also presented. We speculate that the most likely explanation is that the sources in excess are AGNs tracing filaments connected to the clusters. If the association of the overdensities with large-scale structures and their positive relation with cluster redshift is confirmed, these studies could represent a new, direct, way of mapping the cosmic web and its cosmological parameters at high z., Comment: 5 pages, 5 figures. Proceeding of the 6th Italian meeting on AGNs. Volterra, May 2004, http://www.arcetri.astro.it/~agn6

The first systematic study of the serendipitous X-ray source density around 10 high z (0.242 sigma per field, and >5 sigma overall) only on scales 8'X8' and peculiar to cluster fields. The blank field fluctuations, i.e. the most sensitive measurements to date of the X-ray cosmic variance on this scale, indicate variations within ~15-25% around the average value. The first marginal evidence that these overdensities increase with cluster redshift is also presented. We speculate that the most likely explanation for what has been observed is that the x-ray sources are AGNs which trace filaments connected to the clusters. Nevertheless other possible explanations such as an ``X-ray Butcher-Oemler'' effect are not ruled out by present results. If the association of the overdensities with large-scale structures and their positive relation with cluster redshift is confirmed, these studies could represent a new, direct, way of mapping the cosmic web and its parameters at high z., Comment: 8 pages, 6 figures. Accepted by A&A on 09/08/2004, Final version

An enigmatic, small class of IR and X-ray luminous sources, named ``Composite'' starburst/Seyfert galaxies, has been defined from IRAS and RASS data. The objects have optical spectra dominated by the features of HII galaxies (plus, in some cases, weak Seyfert signatures) but X-ray luminosities higher than expected from starbursts and more typical of Seyfert nuclei. The true nature of this class of objects is still unknown. We present Chandra data of four of these galaxies that were obtained to investigate the nature of the X-ray source. The X-ray spectrum, the lack of any significant extended component, and the observed variability indicate that the AGN is the dominant component in the X-ray domain., Comment: 4 pages; 3 figure; proceedings of XLVIII Congresso della Societa' Astronomica Italiana, Milano, Italy 19-23 april 2004, to be published on MemSAIt; Eds. A. Wolter; G. Israel; F. Bacciotti

We report the discovery of a Compton-thick AGN and of intense star-formation activity in the nucleus and disk, respectively, of the nearly edge-on superwind galaxy NGC 4666. Spatially unresolved emission is detected by BeppoSAX only at energies <10 keV, whereas spatially resolved emission from the whole disk is detected by XMM-Newton. A prominent (EW ~ 1-2 keV) emission line at ~6.4 keV is detected by both instruments. From the XMM-Newton data alone the line is spectrally localized at E ~ 6.42 +/- 0.03 keV, and seems to be spatially concentrated in the nuclear region of NGC 4666. This, together with the presence of a flat (Gamma ~ 1.3) continuum in the nuclear region, suggests the existence of a strongly absorbed (i.e., Compton-thick) AGN, whose intrinsic 2-10 keV luminosity is estimated to be L_{2-10} > 2 x 10^{41} erg/s. At energies <1 keV the integrated (BeppoSAX) spectrum is dominated by a ~0.25 keV thermal gas component distributed throughout the disk (resolved by XMM-Newton). At energies ~2-10 keV, the integrated spectrum is dominated by a steep (G > 2) power-law (PL) component. The latter emission is likely due to unresolved sources with luminosity L ~ 10^{38} - 10^{39} erg/s that are most likely accreting binaries (with BH masses <8 M_sun). Such binaries, which are known to dominate the X-ray point-source luminosity in nearby star-forming galaxies, have Gamma ~ 2 PL spectra in the relevant energy range. A Gamma ~ 1.8 PL contribution from Compton scattering of (the radio-emitting) relativistic electrons by the ambient FIR photons may add a truly diffuse component to the 2-10 keV emission., Comment: A&A, in press (10 pages, 14 figures.) Full gzipped psfile obtainable from http://www.bo.iasf.cnr.it/~malaguti/r_stuff.html

We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster (z=0.46). Three different methods of analysis, namely a chip by chip logN-logS, a two dimentional Kolmogorov-Smirnov (KS) test, and the angular correlation function (ACF) show a strong overdensity of sources in the North-East of the field, that may indicate a filament of the large scale structure of the Universe toward 3C 295., Comment: Proceeding of the workshop "Outskirts of Galaxy Clusters: intense life in the suburbs" Turin, March 12-16, 2004; 3 pages, 6 .ps figures

Based on recent work on spectral decomposition of the emission of star-forming galaxies, we assess whether the integrated 2-10 keV emission from high-mass X-ray binaries (HMXBs), L_{2-10}^{HMXB}, can be used as a reliable estimator of ongoing star formation rate (SFR). Using a sample of 46 local (z < 0.1) star forming galaxies, and spectral modeling of ASCA, BeppoSAX, and XMM-Newton data, we demonstrate the existence of a linear SFR-L_{2-10}^{HMXB} relation which holds over ~5 decades in X-ray luminosity and SFR. The total 2-10 keV luminosity is not a precise SFR indicator because at low SFR (i.e., in normal and moderately-starbursting galaxies) it is substantially affected by the emission of low-mass X-ray binaries, which do not trace the current SFR due to their long evolution lifetimes, while at very high SFR (i.e., for very luminous FIR-selected galaxies) it is frequently affected by the presence of strongly obscured AGNs. The availability of purely SB-powered galaxies - whose 2-10 keV emission is mainly due to HMXBs - allows us to properly calibrate the SFR-L_{2-10}^{HMXB} relation. The SFR-L_{2-10}^{HMXB} relation holds also for distant (z ~ 1) galaxies in the Hubble Deep Field North sample, for which we lack spectral information, but whose SFR can be estimated from deep radio data. If confirmed by more detailed observations, it may be possible to use the deduced relation to identify distant galaxies that are X-ray overluminous for their (independently estimated) SFR, and are therefore likely to hide strongly absorbed AGNs., Comment: Astronomy & Astrophysics, in press (15 pages, 7 figures, 4 tables)

We discuss XMM-Newton and BeppoSAX observations of MKN 231, the lowest-redshift Broad Absorption Line (BAL) QSO known so far and one of the best-studied Ultra Luminous Infrared Galaxies. By combining the XMM-Newton spectral resolution and the high-energy bandpass of BeppoSAX we have been able to study in more detail than previously possible its 0.2--50 keV spectral properties. The BeppoSAX PDS data unveiled, for the first time, a highly absorbed ($N_H\sim 2\times 10^{24}$cm$^{-2}$) power-law component. We find that: a) below 10 keV we are seeing only reprocessed radiation through reflection and/or scattering; b) the intrinsic 2-10 keV luminosity of MKN 231 is $1^{+1.0}_{-0.5} \times 10^{44}$ ergs s$^{-1}$, i.e. more than an order of magnitude greater than previous measurements; c) the starburst activity significantly contributes to the soft ($E<2$ keV) X-ray emission., Comment: 11 pages,3 figures, Latex manuscript, Accepted for publication in Astronomy and Astrophysics

Timing analysis of a ~95 ks long XMM-Newton observation of the Seyfert 1 galaxy MCG-6-30-15 is presented. Model-independent tools have been used with the intent of resolving the different components that produce the observed flux and spectral variations down to timescales as short as ~300 s. We find that the fractional variability is possibly due to a variable power law component in the hard band, and a slower thermal component at softer energies, but the data do not rule out effects due to the warm absorber. The most relevant result of this work is the first detection of a significant enhancement of the fractional variability in the ~4.7-5.8 keV energy band compared to the underlying continuum. This represents one of the strongest, model-independent, pieces of evidence to date for the presence of redshifted relativistic matter accreting into the black hole. During the brightest flare of the observation, a soft-to-hard time lag of ~600 s is measured. A very significant increase of the iron line intensity is observed ~3000 s after this flare. In the framework of a disk-corona model and assuming the soft-to-hard time lag is due to Comptonization, these findings make it possible to estimate the electron density and the dimensions of the flare region and the disk-flare distance., Comment: Accepted for publication in A&A

We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster ($z=0.46$). The logN-logS of this field is in good agreement with that computed for the Chandra Deep Field South in this work and in previous ones. Nevertheless, the logN-logS computed separately for the four ACIS-I chips reveals that there is a significant excess of sources to the North-North East and a void to the South of the central cluster. Such an asymmetric distribution is confirmed by the two-dimensional Kolmogorov-Smirnov test, which excludes ($P \sim 3%$) a uniform distribution. In addition, a strong spatial correlation emerges from the study of the angular correlation function of the field: the angular correlation function is above that expected for X-ray sources on a few arcmin scales. In synthesis, the present analysis may indicate a filament of the large scale structure of the Universe toward 3C 295. This kind of studies may open-up a new way to map (with high efficiency) high-density peaks of large scale structures at high-z., Comment: 4 pages, 6 ps figures, to appear in the proceedings of the "The Restless High Energy Universe" Workshop, Amsterdam, May 5-8, 2003

We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster ($z=0.46$). Three different methods of analysis, namely a chip by chip logN-logS, a two dimentional Kolmogorov-Smirnov (KS) test, and the angular correlation function (ACF) show a strong overdensity of sources in the North-East of the field, that may indicate a filament of the large scale structure of the Universe toward 3C 295., Comment: 2 pages, 4 postscript figures; to appear in the proceedings of the "Multiwavelength Cosmology" workshop, Mykonos, Greece, 2003, June 17-21

We report on the spectral properties of a sample of 90 hard X-ray selected serendipitous sources detected in 12 XMM observations with 1~1.55 over the whole sample. We also find that the mean slope of the QSOs in our sample turns out to remain nearly constant (~1.8-1.9) between 0~10^(22) cm^(-2)) is ~30%, with little evolution in the range 2

We present BeppoSAX and XMM-Newton observations of MKN 231. These observations and in particular the BeppoSAX PDS data allowed us to unveil, for the first time, the highly absorbed (N$_H\sim 2\times10^{24}$ cm$^{-2}$) AGN component. We find that: a) the AGN powering MKN231 has an intrinsic 2-10 keV luminosity of $1^{+1}_{-0.5}\times 10^{44}$ erg/s; b) the strong starburst activity contributes significantly in the 0.1-10 keV energy range. We propose that the starburst activity strongly contributes to the far infrared luminosity of MKN 231; this is also suggested by the multiwavelength properties of MKN 231., Comment: 4 pages, 2 fugures, Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Eds

The observation of the Narrow-Line Seyfert 1 galaxy IRAS13349+2438 performed by XMM-Newton European Photon Imaging Camera between 0.3-10 keV, is presented here. The broadband spectrum of the source is dominated at low energies (E < 2 keV) by a strong excess of emission and by complex emission/absorption features between 5.5-8.0 keV. The soft X-ray spectrum is consistent with ionized absorption found by the Reflection Grating Spectrometer (Sako et al. (2001)). We focus on the 2-10 keV spectrum which shows clear evidence for a broad, complex FeK alpha line, previously unseen by ASCA, and for an Fe K-shell edge detected at ~7.3-7.4 keV (rest-frame). The presence of this edge could be explained by either partial covering or ionized/relativistic reflection models, with the latter being preferred and with a resulting power law slope of Gamma \~2.2. The line profile is complex, with a broad bump between ~ 5.5-6.5 keV and a narrow emission line at ~ 7 keV, separated by a sharp drop at ~ 6.8 keV. This profile is compatible with two possible scenarios: i) a broad, ionized and gravitationally redshifted Laor diskline plus a narrow and ionized emission line; ii) a broad, ionized and single Schwarzschild (double-peaked) diskline with a superimposed narrow absorption line., Comment: 10 pages, 6 figures, 2 tables, accepted for publication in Astronomy & Astrophysics

XMM-Newton observations of 10 ULIRGs are reported. The aim is to investigate in hard X-rays a complete ULIRG sample selected from the bright IRAS 60$\mu$m catalogue. All sources are detected in X-rays, 5 of which for the first time. These observations confirm that ULIRGs are intrinsically faint X-rays sources, their observed X-ray luminosities being typically L(2-10 keV)<1E42-43 erg/s, whereas their bolometric luminosities are L>1E45 erg/s. In all sources we find evidence for thermal emission from hot plasma with kT~0.7keV, dominating the X-ray spectra below 1keV, and likely associated with a nuclear or circumnuclear starburst. This thermal emission appears uncorrelated with the FIR luminosity, suggesting that,in addition to the ongoing rate of star formation, other parameters may also affect it. The soft X-ray emission appears to be extended on a scale of ~30kpc for Mkn231 and IRAS19254-7245, possible evidence of galactic superwinds. In these 2 sources, in IRAS20551-4250 and IRAS23128-5919 we find evidence for the presence of hidden AGNs, while a minor AGN contribution may be suspected also in IRAS20100-4156. In particular, we have detected a strong Fe line at 6.4keV in the spectrum of IRAS19254-7245 and a weaker one in Mkn231, suggestive of deeply buried AGNs. For the other sources, the X-ray luminosities and spectral shapes are consistent with hot thermal plasma and X-ray binary emissions of mainly starburst origin. We find that the 2-10keV luminosities in these sources, most likely due to high-mass X-ray binaries, are correlated with L_FIR: both luminosities are good indicators of the current global SFR in the galaxy. The composite nature of ULIRGs is then confirmed, with hints for a predominance of the starburst over the AGN phenomenon in these objects., Comment: Accepted for publication on MNRAS; 16 pages, 7 figures

An unbiased estimate of the average intrinsic X-ray properties and column density distribution of Seyfert galaxies in the local Universe is crucial to validate unified models of active galactic nuclei (AGNs) and to synthesis models for the X-ray background. We present here preliminary results obtained from an on-going XMM-Newton study (~250 ks awarded in the EPIC GT) on a well-defined, statistically complete, and significant sample of nearby Seyfert galaxies., Comment: 4 pages, 3 figures, to appear in "Carnegie Observatories Astrophysics Series, Vol. 1: Coevolution of Black Holes and Galaxies," ed. L. C. Ho (Pasadena: Carnegie Observatories, http://www.ociw.edu/ociw/symposia/series/symposium1/proceedings.html)'

The nature of the ultraluminous X-ray sources (ULX) is still to be understood. Several hypotheses have been suggested to explain the high X-ray luminosity: stellar mass black holes with emission collimated by relativistic effects or anisotropies in the accretion disk, intermediate mass black holes, young supernovae remnants, background active galactic nuclei. To discriminate among the above hypotheses, the search for relativistic effects can be a valuable "pathfinder". Here we propose a list of ULX candidates suitable to show relativistic beaming, Comment: 5 pages, no figure. For the Proceedings of the 15th SIGRAV Conference on General Relativity and Gravitation. Corrected for a misspelled reference

We present the results obtained with BeppoSAX observations of the three Composite Seyfert/star-forming galaxies: IRAS 20051-1117, IRAS 04392-0123 and IRAS 01072+4954. These sources belong to an enigmatic class of X-ray sources detected in the ROSAT All-Sky Survey (Moran et al. 1996) which is composed of 6 low redshift galaxies. Their optical spectra are dominated by the features of HII galaxies while their X-ray luminosities (< 10^{42} ergs/s) are typical of Seyfert galaxies. IRAS 20051-1117 shows a 2-10 keV spectrum well described by a power-law with photon index = 1.9 and low intrinsic absorption. This result, the ratio Flux(2-10 keV)/Flux([OIII]) and the significant X-ray variability detected, clearly rule out a Compton thick nature of this source. IRAS 04392-0123 and IRAS 01072+4954, instead, have a BeppoSAX flux a factor of ~ 50-80 smaller than in the previous ROSAT observations, resulting in poor statistics, that prevents detailed modeling., Comment: 4 pages, 2 figures. To appear in "Carnegie Observatories Astrophysics Series, Vol. 1: Coevolution of Black Holes and Galaxies," ed. L. C. Ho (Pasadena: Carnegie Observatories, http://www.ociw.edu/ociw/symposia/series/symposium1/proceedings.html)

We present the XMM-Newton observation of the merging system IRAS 19254-7245, also known as The Superantennae, whose southern nucleus is classified as a Seyfert 2 galaxy. The XMM-Newton data have allowed us to perform a detailed X-ray imaging and spectral analysis of this system. We clearly detect, for the first time in this system, a strong EW ~ 1.4 keV Fe emission line at 6.49+/-0.1 keV (rest-frame). The X-ray spectrum requires a soft thermal component (kT~0.9 keV; L(0.5-2) ~ 4E41 cgs), likely associated with the starburst, and a hard power-law continuum above 2 keV (observed L(2-10) ~ 4E42 cgs). We confirm the flatness of this latter component, already noted in previous ASCA data. This flatness, together with the detection of the strong Fe-Kalpha line and other broad band indicators, suggest the presence of a Compton-thick AGN with intrinsic luminosity > 1E44 cgs. We show that a Compton-thick model can perfectly reproduce the X-ray spectral properties of this object., Comment: 6 pages, 4 figures, Latex manuscript, Accepted for publication in Astronomy and Astrophysics

Using a long (=150 ksec), broad-band (0.1--40 keV) BeppoSAX observation of the merging starburst system Arp 299 (=IC 694 + NGC 3690) we found the first unambiguous evidence of the presence of a deeply buried (N_H = 2.5E24 cm-2) AGN having an intrinsic luminosity of L(0.5-100 keV) = 1.9E43 cgs. The X-ray spectral properties of this AGN are discussed in detail as well as the thermal component detected at soft X-ray energies which, most likely, is associated with the starburst., Comment: 4 pages, 2 figures, Latex manuscript, Accepted for publication in Astrophysical Journal - Letters Edition

We briefly report on an on-going spectroscopic study of hard X-ray sources selected serendipitously in 12 XMM-Newton fields. Results for the analysis of the 41 sources from the first seven EPIC observations have been discussed in a previous paper (Piconcelli et al. 2002, Paper I) where we found an absolute fraction of X-ray absorbed sources (~30%) lower than expected (~50%) by the predictions of popular CXB synthesis models at F(2-10)~5x10**(-14) erg cm**-2 s**-1. We present here the preliminary results concerning the whole sample including five new deeper XMM-Newton measurements increasing the sample to 90 sources. Even if still on-going, the present study appears to confirm and extend down to F(2-10)~10**(-14) erg cm**-2 s**-1 the above mismatch between observational data and theoretical expectations regarding the fraction of absorbed sources. Furthermore the sample average spectral index of 1.5-1.6 is steeper than the CXB slope indicating that the majority of obscured sources making the bulk of the CXB resides at even lower hard X-ray fluxes., Comment: Proceedings for the "X-ray Surveys: in the light of new observatories" Workshop (to be published in Astron. Nachrichten; includes anabs.cls style file). One page and two figures

We report the identification of the optical and radio counterparts of the ultraluminous X-ray (ULX) source XMMU J124825.9+083020 (NGC4698-ULX1). The optical spectrum taken with the VLT yields a redshift of z=0.43, which implies that the ULX is not associated with the nearby galaxy NGC4698. The spectral energy distribution calculated from the available data indicates that the source is likely to be a BL Lac object. The possible synchrotron peak at X-ray energies suggests that this source may be a gamma-ray emitter., Comment: 6 pages, 5 figures. Accepted for publication by Astronomy and Astrophysics

Little is presently known about the nature of ultraluminous X-ray sources (ULX). Different hypotheses have been proposed to explain their properties: intermediate-mass BHs, Kerr BHs, young SNR, or background AGN. Some of the current problems and open questions in this research field are here reviewed., Comment: 4 pages, no figures. Presented at AGN05: Inflows, Outflows and Reprocessing around black holes, Como (Italy), 11-14 June 2002. To appear in the Proceedings

The XMM-Newton data presented here are the first X-ray observation of the Seyfert 2 galaxy NGC4138. Although the galaxy has been pointed by ROSAT-HRI, it was not detected, with a flux upper limit of about 1.1x10^-13 erg cm^-2 s^-1 in the 0.2-2.4 keV energy band. XMM-Newton performed the observation on 26 November 2001. The source is detected for the first time in X-rays with F[0.2-2.4]=1.0x10^-13 erg cm^-2 s^-1, in agreement with the upper limit of ROSAT. The source spectrum is typical of Seyfert 2 galaxies. We find heavy obscuration (N_H about 8x10^22 cm^-2) and a flat photon index (1.6). The source intrinsic luminosity is about 5x10^41 erg/s in the 0.5-10 keV energy band., Comment: 4 pages, 3 figures. Presented at AGN05: Inflows, Outflows and Reprocessing around black holes, Como (Italy), 11-14 June 2002. To appear in the Proceedings. If you have problems in download, please check also this http://www.bo.iasf.cnr.it/~foschini/pub/0209098.ps.gz

High energy emission has been discovered serendipitously by the BeppoSAX/PDS telescope in the ~1.3 degree field of view around the Piccinotti source H0917-074. A re-pointing of BeppoSAX/NFI has allowed the association of this emission with the Seyfert 2 galaxy MCG-1-24-12 which lies within the original HEAO1/A2 error box of H0917-074. This is the first PDS serendipitous discovery of a Seyfert 2 galaxy and the first detection of MCG-1-24-12 in the X-ray domain. The measured 2-10 keV flux of MCG-1-24-12 is ~1 x 10^(-11) erg cm^(-2) s^(-1) compatible with the Piccinotti HEAO-1/A2 observation. This is a factor of ~6 greater than that observed from EXO0917.3-0722, originally suggested as the counterpart of the Piccinotti source. The 2-10 keV spectrum of MCG-1-24-12 shows the presence of Fe K_alpha emission together with an absorption feature at ~8.7 keV. At high energies, the Seyfert 2 still dominates and the observed 20-100 keV flux is ~4 x 10^(-11)erg cm^(-2) s^(-1)., Comment: 5 pages, 5 figures. to be published in A&A

We present a spectroscopic study of 41 hard X-ray sources detected serendipitously with high significance (> 5 sigma in the 2-10 keV band) in seven EPIC performance/verification phase observations. The large collecting area of EPIC allows us to explore the spectral properties of these faint hard X-ray sources with 2< F_{2-10} < 80 x 10^{-14} erg cm^{-2}s^{-1} even though the length of the exposures are modest (~ 20 ks). Optical identifications are available for 21 sources of our sample. Using a simple power law plus Galactic absorption model we find an average value of the photon index Gamma ~ 1.6-1.7, broadly consistent with recent measurements made at similar fluxes with ASCA and with Chandra stacked spectral analyses. We find that 31 out of 41 sources are well fitted by this simple model and only eight sources require absorption in excess of the Galactic value. Interestingly enough, one third of these absorbed sources are broad line objects, though with moderate column densities. Two sources in the sample are X-ray bright optically quiet galaxies and show flat X-ray spectra. Comparing our observational results with those expected from standard synthesis models of the cosmic X-ray background (CXB) we find a fraction of unabsorbed to absorbed sources larger than predicted by theoretical models at our completeness limit of F_{2-10} ~ 5 x 10^{-14} erg cm^{-2}s^{-1}. The results presented here illustrate well how wide-angle surveys performed with EPIC on board XMM-Newton allow population studies of interesting and unusual sources to be made as well as enabling constraints to be placed on some input parameters for synthesis models of the CXB., Comment: 16 pages, 11 figures. To be published in A&A

An XMM-Newton study of ultraluminous X-ray sources (ULX) has been performed in a sample of 10 nearby Seyfert galaxies. Eighteen ULX have been found with positional uncertainty of about 4". The large collecting area of XMM-Newton makes the statistics sufficient to perform spectral fitting with simple models in 8 cases. The main results of the present minisurvey strengthen the theory that the ULX could be accreting black holes in hard or soft state. In some cases, the contribution of the ULX to the overall X-ray flux appears to be dominant with respect to that of the active nucleus. In addition, 6 ULX present probable counterparts at other wavelengths (optical/infrared, radio). A multiwavelength observing strategy is required to better assess the nature of these sources., Comment: 10 pages, 11 figures. Accepted for publication by Astronomy and Astrophysics. If you want figures at full resolution, please send an email to Foschini

A sample of nine bright Seyfert 1 and NELG type galaxies, observed with BeppoSAX, is analyzed to assess on a truly broad band basis (0.1-200 keV) the issue of the spectral contributions of Compton reflection and iron line fluorescence from circumnuclear gas. The empirical description adopted for the direct continuum is the commonly used power law with an exponential cut-off. The most direct test of the theoretical predictions, namely that the equivalent width of the line, Walpha, and the strength R of the reflection relative to the direct continuum are closely related to each other, gives a substantially positive result, that is their mean ratio is very close to expectation, and only a modest spread in the iron abundance seems implied. The existence of a steep correlation between R and the slope Gamma of the power law is not confirmed. A weak evidence is found that the existence of a very shallow trend to increase on average with Gamma cannot be altogether excluded in both R and Walpha, but needs to be tested with a larger sample. The energy Ef in the exponential cut-off spans a range from about 80 to more than 300 keV. A possible correlation is found, with Ef increasing on average with Gamma: if ignored, for instance by keeping Ef at a fixed value in a sample study, it could be cause of artificial steepening in a correlation between R and Gamma., Comment: accepted for publication in A&A

We present preliminary results of XMM-Newton observations of 5 Ultra-luminous Infrared Galaxies (ULIRGs), part of a mini-survey program dedicated to 10 ULIRGs selected from the bright IRAS sample. For 3 of them (IRAS 20551-4250, IRAS 19254-7245 and Mkn 231) we find strong evidence for the presence of a hidden AGN, while for two others (IRAS 20110-4156 IRAS 22491-1808) the S/N ratio of the data does not allow us to be conclusive. In particular, we have detected a strong Fe-K line in the X-ray spectra of IRAS19254-7245, with an equivalent width (~2 keV) suggestive that most of the energy source in this object is due to a deeply buried AGN., Comment: 4 pages, 3 figures, Latex manuscript, Proc. Symnposium ``New Visions of the X-ray Universe in the XMM-Newton and Chandra Era", 26-30 November 2001, ESTEC, The Netherlands

We present preliminary results from a study with XMM-Newton of the galactic serendipitous sources in a sample of 28 nearby Seyfert galaxies (with D < 22 Mpc). We concentrate here on a subset of four galaxies, namely: NGC3185, NGC3486, NGC3941, and NGC4565. In these galaxies we found six ultraluminous X-ray source (ULX). The large collecting area of XMM-Newton makes the statistics sufficient to perform spectral fitting with simple models. We shortly discuss the results obtained so far., Comment: 4 pages, 6 figures. Proceedings Symposium "New Visions of the Universe in the XMM-Newton and Chandra era" (ESA SP-488, Ed. F. Jansen). To be published