Ark 564 (z=0.0247) is an X-ray-bright NLS1. By using advanced X-ray timing techniques, an excess of delayed emission in the hard X-ray band (4-7.5 keV) following about 1000 seconds after flaring light in the soft X-ray band (0.4-1 keV) was recently d
etected. We report on the X-ray spectral analysis of eight XMM-Newton and one Suzaku observation of Ark 564. High-resolution spectroscopy was performed with the RGS in the soft X-ray band, while broad-band spectroscopy was performed with the EPIC-pn and XIS/PIN instruments. We analysed time-averaged, flux-selected, and time-resolved spectra. Despite the strong variability in flux during our observational campaign, the broad-band spectral shape of Ark 564 does not vary dramatically and can be reproduced either by a superposition of a power law and a blackbody emission or by a Comptonized power-law emission model. High-resolution spectroscopy revealed ionised gas along the line of sight at the systemic redshift of the source, with a low column density and a range of ionisation states. Broad-band spectroscopy revealed a very steep intrinsic continuum and a rather weak emission feature in the iron K band; modelling this feature with a reflection component requires highly ionised gas. A reflection-dominated or an absorption-dominated model are similarly able to well reproduce the time-averaged data from a statistical point of view, in both cases requiring contrived geometries and/or unlikely physical parameters. Finally, through time-resolved analysis we spectroscopically identified the delayed emission as a spectral hardening above ~4 keV; the most likely interpretation for this component is a reprocessing of the flaring light by gas located at 10-100 r_g from the central supermassive black hole that is so hot that it can Compton-upscatter the flaring intrinsic continuum emission.
We present a detailed, photoionization modeling analysis of XMM-Newton/Reflection Grating Spectrometer observations of the Seyfert 2 galaxy NGC 1068. The spectrum, previously analyzed by Kinkhabwala et al. (2002), reveals a myriad of soft-Xray emissi
on lines, including those from H- and He-like carbon, nitrogen, oxygen, and neon, and M- and L-shell iron. As noted in the earlier analysis, based on the narrowness of the radiative recombination continua, the electron temperatures in the emission-line gas are consistent with photoionization, rather than collisional ionization. The strengths of the carbon and nitrogen emission lines, relative to those of oxygen, suggest unusual elemental abundances, which we attribute to star-formation history of the host galaxy. Overall, the emission-lines are blue-shifted with respect to systemic, with radial velocities ~ 160 km/s, similar to that of [O III] 5007, and thus consistent with the kinematics and orientation of the optical emission-line gas and, hence, likely part of an AGN-driven outflow. We were able to achieve an acceptable fit to most of the strong emission-lines with a two-component photoionization model, generated with Cloudy. The two components have ionization parameters and column densities of logU = -0.05 and 1.22, and logN(H) = 20.85 and 21.2, and covering factors of 0.35 and 0.84, respectively. The total mass of the X-ray gas is roughly of an order of magnitude greater than the mass of ionized gas determined from optical and near-IR spectroscopy, which indicates that it may be the dominant component of the narrow line region. Furthermore, we suggest that the medium which produces the scattered/polarized optical emission in NGC~1068 possesses similar physical characteristics to those of the more highly-ionized of the X-ray model components.
X-ray spectra of AGN often contain signatures indicative of absorption in multiple layers of gas whose ionization-state and covering fraction may vary with time. It has been unclear to date how much of the observed X-ray spectral and timing behavior
in AGN can be attributed to variations in absorption, versus variations in the strengths of emission or reflection components. Diagnostics of the inner regions of AGN cannot be reliably performed until the origin of observed effects is understood. We investigate the role of the X-ray absorbers in the Seyfert 1 galaxy NGC 3516. Time-averaged and flux-selected spectroscopy is used to examine the behavior of NGC 3516 observed in Chandra HETG and XMM data from Oct 2006. New H-like and He-like emission and absorption features discovered in the Fe K regime reveal a previously unknown zone of circumnuclear gas in NGC 3516 with log xi ~ 4.3 and column density 1E23 cm^-2. A lower-ionization layer with log xi ~2 and of similar column density is confirmed from previous observations, this layer has a covering fraction around 50%, and changes in covering provide a simple explanation of a deep dip in the light curve that we interpret as an eclipse of the continuum due to passage of a cloud across the sight line within half a day. These inner zones of absorbing gas are detected to have outflow velocities in the range 1000-2000 km/s, this, and constraints on radial location are consistent with an origin as part of a disk wind in NGC 3516.
CONTEXT: The variable X-ray spectra of AGN systematically show steep power-law high states and hard-spectrum low states. The hard low state has previously been found to be a component with only weak variability. The origin of this component and the r
elative importance of effects such as absorption and relativistic blurring are currently not clear. AIMS: In a follow-up of previous principal components analysis, we aim to determine the relative importance of scattering and absorption effects on the time-varying X-ray spectrum of the narrow-line Seyfert 1 galaxy Mrk~766. METHODS: Time-resolved spectroscopy, slicing XMM and Suzaku data down to 25 ks elements, is used to investigate whether absorption or scattering components dominate the spectral variations in Mrk 766.Time-resolved spectroscopy confirms that spectral variability in Mrk 766 can be explained by either of two interpretations of principal components analysis. Detailed investigation confirm rapid changes in the relative strengths of scattered and direct emission or rapid changes in absorber covering fraction provide good explanations of most of the spectral variability. However, a strong correlation between the 6.97 keV absorption line and the primary continuum together with rapid opacity changes show that variations in a complex and multi-layered absorber, most likely a disk wind, are the dominant source of spectral variability in Mrk 766
