The impact of accretion disk winds on the X-ray spectrum of AGN: Part 1 - XSCORT

(abridged) The accretion disk in AGN is expected to produce strong outflows, in particular a UV-line driven wind. Despite providing a good fit to the data, current spectral models of the X-ray spectrum of AGN observed through an accretion disk wind are ad-hoc in their treatment of the properties of the wind material. In order to address these limitations we adopt a numerical computation method that links a series of radiative transfer calculations, incorporating the effect of a global velocity field in a self-consistent manner (XSCORT). We present a series of example spectra from the XSCORT code that allow us to examine the shape of AGN X-ray spectra seen through a wind, for a range of velocity and density distributions, total column densities and initial ionization parameters. These detailed spectral models clearly show considerable complexity and structure that is strongly affected by all these factors. The presence of sharp features in the XSCORT spectra contrasts strongly with both the previous models and with the smooth nature of the observed X-ray spectra of AGN with soft X-ray excesses, demonstrating that accretion disk winds are unlikely to be the origin of this mysterious spectral feature. The most significant parameter affecting the presence of the sharp features in the models is the terminal velocity of the wind. Increasing the terminal velocity of the absorbing material to ~c, and hence dramatically increasing the velocity dispersion across the wind, could potentially remove these features resulting in a spectrum similar to the previous models. Such a fast moving outflow cannot be associated with a radiatively driven accretion disk wind, however the presence of a highly relativistic jet may provide an origin for such material.Comment: 14 pages, 9 figures (colour), Accepted for publication in MNRAS (13th Aug 2007). Several significant changes to the text from v

The Location and Kinematics of the Coronal-Line Emitting Regions in Active Galactic Nuclei

We use the photoionization code CLOUDY to determine both the location and the kinematics of the optical forbidden, high-ionization line (hereafter, FHIL) emitting gas in the narrow line Seyfert 1 galaxy Ark 564. The results of our models are compared with the observed properties of these emission lines to produce a physical model that is used to explain both the kinematics and the source of this gas. The main features of this model are that the FHIL emitting gas is launched from the putative dusty torus and is quickly accelerated to its terminal velocity of a few hundred km s-1. Iron-carrying grains are destroyed during this initial acceleration. This velocity is maintained by a balance between radiative forces and gravity in this super-Eddington source. Eventually the outflow is slowed at large radii by the gravitational forces of and interactions with the host galaxy. In this model, FHIL emission traces the transition between the active galactic nucleus (AGN) and bulge zones of influence

Probing the face-on disc-corona system of the bare AGN Mrk 110 from UV to hard X-rays: A moderate changing-state AGN?

Context. The X-ray broadband spectra of the bare active galactic nucleus (AGN) Mrk 110, obtained by simultaneous XMM-Newton and NuSTAR observations performed in November 2019 and April 2020, are characterised by the presence of a prominent and absorption-free smooth soft X-ray excess, moderately broad O VII and Fe Kα emission lines, and a lack of a strong Compton hump. The disc-corona system is almost viewed face-on as inferred from the O VII accretion disc lines. While relativistic reflection as the sole emission is ruled out, a simplified combination of soft and hard Comptonisation (using COMPTT) from a warm and a hot corona, plus mild relativistic disc reflection (occuring at a few 10 s Rg) reproduces the data very well.Aims. We aim to confirm the physical origin of the soft X-ray excess of Mrk 110 and to determine its disc-corona system properties from its energetics using two new sophisticated models: REXCOR and RELAGN, respectively.Methods. We applied these models to the 0.3–79 keV X-ray broadband spectra and to the spectral energy distribution (SED) from UV to hard X-rays, respectively.Results. At both epochs, the inferred high values of the warm-corona heating from the X-ray broadband spectral analysis using REXCOR confirm that the soft X-ray excess of Mrk 110 mainly originates from a warm corona rather than relativistic reflection. The intrinsic best-fit SED determined at both epochs using RELAGN show a high X-ray contribution relative to the UV and are very well reproduced by a warm and hot corona plus mild relativistic reflection. The outer radii of the hot and warm corona are located at a few 10 s and ∼100 Rg, respectively. Moreover, combining the inferred low Eddington ratio (approximatively a few percent) from this work, and previous multi-wavelength spectral and timing studies suggest that Mrk 110 could be classified as a moderate changing-state AGN.Conclusions. Our analysis confirms the existence of a warm corona as a significant contribution to the soft X-ray excess and UV emission in Mrk 110, adding to growing evidence that AGN accretion deviates from standard disc theory. This strengthens the importance of long-term multi-wavelength monitoring on both single targets and large AGN surveys to reveal the real nature of the disc-corona system in AGNs

On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium

We present a comparison between the 2001 XMM-Newton and 2005 Suzaku observations of the quasar, PG1211+143 at z=0.0809. Variability is observed in the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which is significantly weaker in 2005 than during the 2001 XMM-Newton observation. From a recombination timescale of <4 years, this implies an absorber density n>0.004 particles/cm3, while the absorber column is 5e22<N_H <1 1e24 particles/cm2. Thus the sizescale of the absorber is too compact (pc scale) and the surface brightness of the dense gas too high (by 9-10 orders of magnitude) to arise from local hot gas, such as the local bubble, group or Warm/Hot Intergalactic Medium (WHIM), as suggested by McKernan et al. (2004, 2005). Instead the iron K-shell absorption must be associated with an AGN outflow with mildly relativistic velocities. Finally we show that the the association of the absorption in PG1211+143 with local hot gas is simply a coincidence, the comparison between the recession and iron K absorber outflow velocities in other AGN does not reveal a one to one kinematic correlation.Comment: accepted for publication in MNRAS LETTERS. 5 pages, 4 figure

Quantifying the fast outflow in the luminous Seyfert galaxy PG1211+143

We report two new XMM-Newton observations of PG1211+143 in December 2007, again finding evidence of the fast outflow of highly ionised gas first detected in 2001. Stacking the new spectra with those from two earlier XMM-Newton observations reveals strong and broad emission lines of FeXXV and OVIII, indicating the fast outflow to be persistent and to have a large covering factor. This finding confirms a high mass rate for the ionised ouflow in PG1211+143 and provides the first direct measurement of a wide angle, sub-relativistic outflow from an AGN transporting mechanical energy with the potential to disrupt the growth of the host galaxy. We suggest PG1211+143 may be typical of an AGN in a rapid super-Eddington growth phase.Comment: Accepted for publication in MNRAS. Extended version with new figures and table

Intensive HST, RXTE and ASCA Monitoring of NGC 3516: Evidence Against Thermal Reprocessing

During 1998 April 13-16, NGC 3516 was monitored almost continuously with HST for 10.3 hr in the UV and 2.8 d in the optical, and simultaneous RXTE and ASCA monitoring covered the same period. The X-rays were strongly variable with the soft (0.5-2 keV) showing stronger variations (~65% peak-to-peak) than the hard (2-10 keV; ~50% peak-to-peak). The optical continuum showed much smaller but highly significant variations: a slow ~2.5% rise followed by a faster ~3.5% decline. The short UV observation did not show significant variability. The soft and hard X-ray light curves were strongly correlated with no significant lag. Likewise, the optical continuum bands (3590 and 5510 A) were also strongly correlated with no measurable lag above limits of <0.15 d. However no significant correlation or simple relationship could be found for the optical and X-ray light curves. These results appear difficult to reconcile with previous reports of correlations between X-ray and optical variations and of measurable lags within the optical band for some other Seyfert 1s. These results also present serious problems for "reprocessing" models in which the X-ray source heats a stratified accretion disk which then reemits in the optical/ultraviolet: the synchronous variations within the optical would suggest that the emitting region is <0.3 lt-d across, while the lack of correlation between X-ray and optical variations would indicate, in the context of this model, that any reprocessing region must be >1 lt-d in size. It may be possible to resolve this conflict by invoking anisotropic emission or special geometry, but the most natural explanation appears to be that the bulk of the optical luminosity is generated by some other mechanism than reprocessing.Comment: 23 pages including 6 figures, accepted for publication in Ap

Ionized Absorbers in AGN: the Role of Collisional Ionization and Time-Evolving Photoionization

In this paper we explore collisional ionization and time-evolving photoionization in the, X-ray discovered, ionized absorbers in Seyfert galaxies. These absorbers show temporal changes inconsistent with simple equilibrium models. We develop a simple code to follow the temporal evolution of non-equilibrium photoionized gas. As a result several effects appear that are easily observable; and which, in fact, may explain otherwise paradoxical behavior. Specifically we find that: 1) In many important astrophysical conditions pure collisional and photoionization equilibria can be distinguished with moderate spectral resolution observations, due to a strong absorption structure between 1 and 3 keV. 2) In time-evolving non-equilibrium photoionization models the response of the ionization state of the gas to sudden changes of the ionizing continuum is smoothed and delayed at low gas densities, even when the luminosity increases. 3) If the changes of the ionizing luminosity are not instantaneous, and the electron density is low enough (the limit depends on the average ionization state of the gas), the ionization state of the gas can continue to increase while the source luminosity decreases, so a maximum in the ionization state of a given element may occur during a minimum of the ionizing intensity (the opposite of the prediction of equilibrium models). 4) Different ions of different elements reach their equilibrium configuration on different time-scales. These properties are similar to those seen in several ionized absorbers in AGN, properties which had hitherto been puzzling. We applied these models to a high S/N ROSAT PSPC observation of the Seyfert 1 galaxy NGC 4051.Comment: 36 pages, 10 figures, accepted for publication on Apj, in pres