The properties of the absorbing and line emitting material in IGR J16318-4848

We have performed a detailed analysis of the XMM-Newton observation of IGR J16318-4848, to study the properties of the matter responsible for the obscuration and for the emission of Fe and Ni lines. Even if the line of sight material has a column density of about 2x10^24 cm^-2, from the Fe Kalpha line EW and Compton Shoulder we argue that the matter should have an average column density of a few x10^23 cm^-2, along with a covering factor of about 0.1-0.2. The iron Kalpha line varies on time scales as short as 1000 s, implying a size of the emitting region smaller than about 3x10^13 cm. The flux of the line roughly follows the variations of the continuum, but not exactly, suggesting a variation of the geometrical properties of the emitting region on similar time scales.Comment: accepted for publication in MNRAS, pink page

Cosmological Evolution of the Central Engine in High-Luminosity, High-Accretion Rate AGN

In this paper I discuss the status of observational studies aiming at probing the cosmological evolution of the central engine in high-luminosity, high-accretion rate Active Galactic Nuclei (AGN). X-ray spectroscopic surveys, supported by extensive multi-wavelength coverage, indicate a remarkable invariance of the accretion disk plus corona system, and of their coupling up to redshifts z≈6. Furthermore, hard X-ray (E >10 keV) surveys show that nearby Seyfert Galaxies share the same central engine notwithstanding their optical classication. These results suggest that the high-luminosity, high accretion rate quasar phase of AGN evolution is homogeneous over cosmological times

AGN spectral states from simultaneous UV and X-ray observations by XMM-Newton

The supermassive black holes in active galactic nuclei (AGN) and stellar-mass black holes in X-ray binaries (XRBs) are believed to work in a similar way. While XRBs evolve rapidly and several sources have undergone a few complete cycles from quiescence to an outburst and back, most AGN remain in the same state over periods of decades, due to their longer characteristic timescale proportional to their size. However, the study of the AGN spectral states is still possible with a large sample of sources. Multi-wavelength observations are needed for this purpose since the AGN thermal disc emission dominates in the ultraviolet energy range, while the up-scattered hot-corona emission is detected in X-rays. We compared simultaneous UV and X-ray measurements of AGN obtained by the XMM-Newton satellite. The non-thermal flux was constrained from the 2-12 keV X-ray luminosity, while the thermal disc component was estimated from the UV flux at 2900A. The hardness (ratio between the X-ray and UV plus X-ray luminosity) and the total luminosity were used to construct the AGN state diagrams. For sources with reliable mass measurements, the Eddington ratio was used instead of the total luminosity. The state diagrams show that the radio-loud sources have on average higher hardness, due to the lack of the thermal disc emission in the UV band, and have flatter intrinsic X-ray spectra. In contrast, the sources with high luminosity and low hardness are radio-quiet AGN. The hardness-Eddington ratio diagram reveals that the average radio-loudness is stronger for low-accreting sources, while it decreases when the accretion rate is close to the Eddington limit. Our results indicate that the general properties of AGN accretion states are similar to those of X-ray binaries. This suggests that the AGN radio dichotomy of radio-loud and radio-quiet sources can be explained by the evolution of the accretion states.Comment: 13 pages, 12 figures, accepted in A&

XMM-NEWTON SCIENTIFIC HIGHLIGHTS: X-RAY SPECTROSCOPIC POPULATION STUDIES OF AGN

In this paper I review the contribution that the XMM-Newton ESA X-ray mission has given to our understanding of Active Galactic Nuclei, together with other operational, and complementary, X-ray facilities. I will focus on answering three basic questions: a) to which extent do AGN share the same engine?; b) to which extent are AGN “relativistic machines”?; c) to which extent do AGN affect their immediate environment

Spectral Variability and iron line emission in the ASCA Observations of the Seyfert 1 Galaxy NGC4051

We present the results of an extensive analysis of the ``ASCA'' AO2 observation of the Seyfert 1 galaxy NGC4051. The target exhibits broadband [0.5--10 keV] variability by a factor $\sim 8$ on time scales $\sim 10^4 s$, with a typical doubling time $\sim 500 s$. The spectrum is characterized by a strong emission excess over the extrapolated power law at energies $E \le 1 keV$. Absorption edges due to ionized oxygen species OVII and OVIII are detected together with an emission-like feature at $E \sim 0.93 keV$. The OVII edge undergoes significant variability on a timescale as low as $\sim 10^4 s$, whilst no contemporary variability of the OVIII feature is detected. Typical variability time scales place constraints on the location and the density of the absorbing matter. In the self-consistent hypothesis of a high energy ($E \ge 2.3 keV$) power law reflected by an infinite plane-parallel cold slab, a photon index change ($\Delta \Gamma = 0.4$) has also been observed; a natural explanation can be found in the framework of non-thermal Comptonization models. The iron line is redshifted (centroid energy $E \sim 6.1 keV$) and broad ($\sigma > 0.2 keV$); multicomponent structure is suggestive of emission from a relativistic accretion disk; however if the disk is not ionized a contribution by a molecular torus or an iron overabundance by a factor $\sim 1.5$ are required.Comment: 17 pages, latex, 12 figures. To be published in Publication of Astronomical Society of Japa