Suzy Collin

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How relevant is the torus activity/geometry for the TeV gamma-rays emitted in the jet of M87 ? Abstract. Motivated by unification schemes of active galactic nuclei, we review evidence for the existence of a small-scale dust torus in M87, a Fanaroff-Riley Class I radio galaxy. Since there is no direct evidence of any thermal emission from its torus we(More)
The 2-10 keV continuum of AGN is well represented by a single power law, generally attributed to a hot comptonizing medium, such as a corona above the accretion disk. At smaller energies the continuum displays an excess with respect to the extrapolation of this power law, called the " soft X-ray excess ". Until now it was attributed, either to reflection of(More)
Picosecond and femtosecond spectroscopy allow the detailed study of carrier dynamics in nanostructured materials. In such experiments, a laser pulse normally excites several nanostructures at once. However, spectroscopic information may also be acquired using pulses from an electron beam in a modern electron microscope, exploiting a phenomenon called(More)
In the era of XMM-Newton and Chandra missions, it is crucial to use codes able to compute correctly the line spectrum of X-ray irradiated thick media (Thomson thickness of the order of unity), in order to build models for the structure and the emission of the central regions of Active Galactic Nuclei (AGN), or of X-ray binaries. In all photoionized codes(More)
We develop an exploratory model for the outer, grav-itationally unstable regions of accretion disks around massive black holes. We consider black holes of mass 10 6 to 10 10 M , and primeval or solar abundances. In a first step we study star formation and evolution in a purely gaseous marginally unstable disk, and we show that unstable fragments should(More)
Context. Scatter around the relationship between central black hole masses in active galactic nuclei (AGNs) obtained by reverberation-mapping methods and host-galaxy bulge velocity dispersion indicates that the masses are uncertain typically by a factor of about three. Aims. In this paper, we try to identify the sources and systematics of this uncertainty.(More)
With the advent of the present and future spatial X-ray missions, it becomes crucial to model correctly the line spectrum of X-ray emitting media such as the photoionized plasma observed in the central regions of Active Galactic Nuclei (AGN), or in X-ray binaries. We have built a photoionization code, Titan, solving the transfer of a thousand lines and of(More)
Using the new version of the photoionization code Titan designed for plane-parallel photoionized thick hot media, which is unprecedented from the point of view of line transfer, we have undertaken a systematic study of the influence of different parameters on the He-like and H-like emission of a medium pho-toionized by an X-ray source. We explain why in(More)
In a previous paper, Collin & Huré (2001), using a sample of Active Galactic Nuclei (AGN) where the mass has been determined by reverberation studies (the Kaspi et al. 2000 sample), have shown that if the optical luminosity is emitted by a steady accretion disc, it implies that about half of the objects of the sample are accreting close to the Eddington(More)
Nayakshin & Kazanas (2002) have considered the time-dependent illumination of an accretion disc in Active Galactic Nuclei, in the lamppost model, where it is assumed that an X-ray source illuminates the whole inner-disc region in a relatively steady way. We extend their study to the flare model, which postulates the release of a large X-ray flux above a(More)