ALBERT

Description: We present results from a joint XMM–Newton / NuSTAR monitoring of the Seyfert 1 NGC 4593, consisting of 5 x 20 ks simultaneous observations spaced by 2 d, performed in 2015 January. The source is variable, both in flux and spectral shape, on time-scales down to a few ks and with a clear softer-when-brighter behaviour. In agreement with past observations, we find the presence of a warm absorber well described by a two-phase ionized outflow. The source exhibits a cold, narrow and constant Fe Kα line at 6.4 keV, and a broad component is also detected. The broad-band (0.3–79 keV) spectrum is well described by a primary power law with ~= 1.6–1.8 and an exponential cut-off varying from $90^{+ 40}_{- 20}$ to 〉700 keV, two distinct reflection components, and a variable soft excess correlated with the primary power law. This campaign shows that probing the variability of Seyfert 1 galaxies on different time-scales is of prime importance to investigate the high-energy emission of active galactic nuclei.

Description: Ongoing studies with XMM–Newton have shown that powerful accretion disc winds, as revealed through highly ionized Fe K-shell absorption at E  ≥ 6.7 keV, are present in a significant fraction of active galactic nuclei (AGNs) in the local Universe (Tombesi et al. 2010a ). In Gofford et al., we analysed a sample of 51 Suzaku -observed AGNs and independently detected Fe K absorption in ~40 per cent of the sample, and we measured the properties of the absorbing gas. In this work, we build upon these results to consider the properties of the associated wind. On average, the fast winds ( v w  〉 0.01 c ) are located 〈 r 〉 ~ 10 15–18  cm (typically ~10 2–4 r s ) from their black hole, their mass outflow rates are of the order of $\langle \skew{3}\dot{M}_{\rm w}\rangle \sim 0.01\hbox{--}1$  M  yr –1 or ${\sim }(0.01\hbox{--}1)\skew{3}\dot{M}_{\rm Edd}$ and kinetic power is constrained to 〈 L w 〉 ~ 10 43–45  erg s –1 , equivalent to ~(0.1–10 per cent) L Edd . We find a fundamental correlation between the source bolometric luminosity and the wind velocity, with $v_{\rm w} \propto L_{\rm bol}^{\alpha }$ and $\alpha =0.4^{+0.3}_{-0.2}$ (90 per cent confidence), which indicates that more luminous AGN tend to harbour faster Fe K winds. The mass outflow rate $\skew{3}\dot{M}_{\rm w}$ , kinetic power L w and momentum flux $\dot{p}_{\rm w}$ of the winds are also consequently correlated with L bol , such that more massive and more energetic winds are present in more luminous AGN. We investigate these properties in the framework of a continuum-driven wind, showing that the observed relationships are broadly consistent with a wind being accelerated by continuum-scattering. We find that, globally, a significant fraction (~85 per cent) of the sample can plausibly exceed the L w / L bol  ~ 0.5 per cent threshold thought necessary for feedback, while 45 per cent may also exceed the less conservative ~5 per cent of L bol threshold as well. This suggests that the winds may be energetically significant for AGN–host-galaxy feedback processes.

Description: We present simultaneous XMM–Newton and NuSTAR observations of the ‘bare’ Seyfert 1 galaxy, Ark 120, a system in which ionized absorption is absent. The NuSTAR hard-X-ray spectral coverage allows us to constrain different models for the excess soft-X-ray emission. Among phenomenological models, a cutoff power law best explains the soft-X-ray emission. This model likely corresponds to Comptonization of the accretion disc seed UV photons by a population of warm electrons: using Comptonization models, a temperature of ~0.3 keV and an optical depth of ~13 are found. If the UV-to-X-ray optxagnf model is applied, the UV fluxes from the XMM–Newton Optical Monitor suggest an intermediate black hole spin. Contrary to several other sources observed by NuSTAR , no high-energy cutoff is detected with a lower limit of 190 keV.

Description: We present a broad-band spectral analysis of the joint XMM–Newton and Nuclear Spectroscopic Telescope Array observational campaign of the narrow-line Seyfert 1 SWIFT J2127.4+5654, consisting of 300 ks performed during three XMM–Newton orbits. We detect a relativistic broadened iron Kα line originating from the innermost regions of the accretion disc surrounding the central black hole, from which we infer an intermediate spin of $a = 0.58^{+0.11}_{-0.17}$ . The intrinsic spectrum is steep ( = 2.08 ± 0.01) as commonly found in narrow-line Seyfert 1 galaxies, while the cutoff energy ( $E_{\rm c}=108^{+11}_{-10}$ keV) falls within the range observed in broad-line Seyfert 1 galaxies. We measure a low-frequency lag that increases steadily with energy, while at high frequencies, there is a clear lag following the shape of the broad Fe K emission line. Interestingly, the observed Fe K lag in SWIFT J2127.4+5654 is not as broad as in other sources that have maximally spinning black holes. The lag amplitude suggests a continuum-to-reprocessor distance of about 10–20 r g . These timing results independently support an intermediate black hole spin and a compact corona.

Description: The study of winds in active galactic nuclei (AGNs) is of utmost importance as they may provide the long sought-after link between the central black hole and the host galaxy, establishing the AGN feedback. Recently, Laha et al. reported the X-ray analysis of a sample of 26 Seyferts observed with XMM–Newton , which are part of the so-called warm absorbers in X-rays (WAX) sample. They claim the non-detection of Fe K absorbers indicative of ultrafast outflows in four observations previously analysed by Tombesi et al. They mainly impute the Tombesi et al. detections to an improper modelling of the underlying continuum in the E = 4–10 keV band. We therefore re-address here the robustness of these detections and we find that the main reason for the claimed non-detections is likely due to their use of single events only spectra, which reduces the total counts by 40 per cent. Performing a re-analysis of the data in the whole E = 0.3–10 keV energy band using their models and spectra including also double events, we find that the blueshifted Fe K absorption lines are indeed detected at 〉99 per cent. This work demonstrates the robustness of these detections in XMM–Newton even including complex model components such as reflection, relativistic lines and warm absorbers.

Description: We carried out a systematic analysis of time lags between X-ray energy bands in a large sample (32 sources) of unabsorbed, radio quiet active galactic nuclei (AGN), observed by XMM – Newton . The analysis of X-ray lags (up to the highest/shortest frequencies/time-scales), is performed in the Fourier-frequency domain, between energy bands where the soft excess (soft band) and the primary power law (hard band) dominate the emission. We report a total of 15 out of 32 sources displaying a high-frequency soft lag in their light curves. All 15 are at a significance level exceeding 97 per cent and 11 are at a level exceeding 99 per cent. Of these soft lags, seven have not been previously reported in the literature, thus this work significantly increases the number of known sources with a soft/negative lag. The characteristic time-scales of the soft/negative lag are relatively short (with typical frequencies and amplitudes of  ~ 0.07–4  x 10 –3  Hz and  ~ 10–600 s, respectively), and show a highly significant (4) correlation with the black hole mass. The measured correlations indicate that soft lags are systematically shifted to lower frequencies and higher absolute amplitudes as the mass of the source increases. To first approximation, all the sources in the sample are consistent with having similar mass-scaled lag properties. These results strongly suggest the existence of a mass-scaling law for the soft/negative lag, that holds for AGN spanning a large range of masses (about 2.5 orders of magnitude), thus supporting the idea that soft lags originate in the innermost regions of AGN and are powerful tools for testing their physics and geometry.

Description: Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order of ~0.1 c in a limited sample of six broad-line radio galaxies. They are observed as blueshifted Fe  xxv–xxvi K-shell absorption lines, similarly to the ultrafast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the search for such Fe K absorption lines to a larger sample of 26 radio-loud active galactic nuclei (AGN) observed with XMM–Newton and Suzaku . The sample is drawn from the Swift Burst Alert Telescope 58-month catalogue and blazars are excluded. X-ray bright Fanaroff–Riley Class II radio galaxies constitute the majority of the sources. Combining the results of this analysis with those in the literature we find that UFOs are detected in 〉27 per cent of the sources. However, correcting for the number of spectra with insufficient signal-to-noise ratio, we can estimate that the incidence of UFOs is this sample of radio-loud AGN is likely in the range f ~= (50 ± 20) per cent. A photoionization modelling of the absorption lines with xstar allows us to estimate the distribution of their main parameters. The observed outflow velocities are broadly distributed between v out 1000 km s –1 and v out ~= 0.4 c , with mean and median values of v out ~= 0.133 c and v out ~= 0.117 c , respectively. The material is highly ionized, with an average ionization parameter of log ~= 4.5 erg s –1  cm, and the column densities are larger than N H  〉 10 22  cm –2 . Overall, these characteristics are consistent with the presence of complex accretion disc winds in a significant fraction of radio-loud AGN and demonstrate that the presence of relativistic jets does not preclude the existence of winds, in accordance with several theoretical models.

Description: The existence of ionized X-ray absorbing layers of gas along the line of sight to the nuclei of Seyfert galaxies is a well established observational fact. This material is systematically outflowing and shows a large range in parameters. However, its actual nature and dynamics are still not clear. In order to gain insights into these important issues we performed a literature search for papers reporting the parameters of the soft X-ray warm absorbers (WAs) in 35 type 1 Seyferts and compared their properties to those of the ultra-fast outflows (UFOs) detected in the same sample. The fraction of sources with WAs is 〉60 per cent, consistent with previous studies. The fraction of sources with UFOs is 〉34 per cent, 〉67 per cent of which also show WAs. The large dynamic range obtained when considering all the absorbers together, spanning several orders of magnitude in ionization, column, velocity and distance allows us, for the first time, to investigate general relations among them. In particular, we find significant correlations indicating that the closer the absorber is to the central black hole, the higher the ionization, column, outflow velocity and consequently the mechanical power. In all the cases, the absorbers continuously populate the whole parameter space, with the WAs and the UFOs lying always at the two ends of the distribution. These evidence strongly suggest that these absorbers, often considered of different types, could actually represent parts of a single large-scale stratified outflow observed at different locations from the black hole. The UFOs are likely launched from the inner accretion disc and the WAs at larger distances, such as the outer disc and/or torus. We argue that the observed parameters and correlations are, to date, consistent with both radiation pressure through Compton scattering and magnetohydrodynamic processes contributing to the outflow acceleration, the latter playing a major role. Most of the absorbers, especially the UFOs, show a sufficiently high mechanical power (at least ~0.5 per cent of the bolometric luminosity) to provide a significant contribution to active galactic nuclei (AGN) feedback and thus to the evolution of the host galaxy. In this regard, we find possible evidence for the interaction of the AGN wind with the surrounding environment on large scales.

Description: We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for Fe  xxv Heα and/or Fe  xxvi Lyα absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E 6.7 keV in 20/51 sources at the P MC ≥ 95 per cent level, which corresponds to ~40 per cent of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to Fe  xxv Heα and Fe  xxvi Lyα at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the Fe K absorption components are log ( N H /cm –2 ) 23 and log (/erg cm s –1 ) 4.5, respectively. Measured outflow velocities span a continuous range from 〈1500 km s –1 up to ~100 000 km s –1 , with mean and median values of ~0.1 c and ~0.056 c, respectively. The results of this work are consistent with those recently obtained using XMM–Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe.

Description: We present the analysis of the X-ray variability and spectral timing properties of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the most variable ULXs known so far. The variability properties are used as a diagnostic of the accretion state of the source and to derive estimates of the black hole (BH) mass. The observed high level of fast X-ray variability (fractional root-mean-square variability – rms – amplitude of ~30 per cent in the hard energy band), the hardening of the fractional rms spectrum and the properties of the quasi-periodic oscillation (QPO), all resemble those of a source in a hard-intermediate accretion state. We confirm the previous detection of a soft lag in the X-ray light curves of the source during 2006 and 2008 observations and find that the soft lag is still present in the more recent 2010/2011 observations. Using the entire available XMM–Newton data set (public as of 2012 February), we observe that the soft lag (of few seconds amplitude) is detected over a relatively large range of frequencies ( ~ 5–90 mHz), which always includes the QPO frequencies. The soft lag displays energy-dependence, with the (absolute) amplitude increasing as a function of energy separation. We find close analogies with soft lags associated with type-C QPOs in BH binary systems (although an association to other types of QPOs cannot be completely excluded), as well as with reverberation lags observed in AGN. In both cases an intermediate-mass BH solution appears the most plausible.