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Blueshifted absorption lines in the X-ray spectra of AGN show that ultra-fast outflows with typical velocities $v \sim 0.1c$ are a common feature of these luminous objects. Such powerful AGN winds offer an explanation of the observed M-$\sigma$ relation linking the mass of the supermassive black hole and the velocity dispersion in the galaxy's stellar bulge. An extended XMM-Newton study of the luminous Seyfert galaxy PG1211+143 recently revealed a variable multi-velocity wind. Here we report the detection of a short-lived, ultra-fast inflow during the same observation. Previous reports of inflows used single absorption lines with uncertain identifications, but this new result identifies an array of resonance absorption lines of highly ionised Fe, Ca, Ar, S and Si, sharing a common redshift when compared with a grid of realistic photoionization spectra. The redshifted absorption arises in a column of highly ionized matter close to the black hole, with a line-of-sight velocity, $v \sim 0.3c$, inconsistent with the standard picture of a plane circular accretion disc. This may represent the first direct evidence for chaotic accretion in AGN, where accretion discs are generally misaligned to the black hole spin. For sufficient inclinations, the Lense-Thirring effect can break the discs into discrete rings, which then precess, collide and shock, causing near free-fall of gas towards the black hole. The observed accretion rate for the reported infall is comparable to the hard X-ray luminosity in PG1211+143, suggesting that direct infall may be a significant contributor to inner disc accretion., Comment: 7 pages, 3 figures, accepted for publication in MNRAS

We investigate the X-ray time lags of a recent ~630ks XMM-Newton observation of PG 1211+143. We find well-correlated variations across the XMM-Newton EPIC bandpass, with the first detection of a hard lag in this source with a mean time delay of up to ~3ks at the lowest frequencies. We find that the energy-dependence of the low-frequency hard lag scales approximately linearly with log(E) when averaged over all orbits, consistent with the propagating fluctuations model. However, we find that the low-frequency lag behaviour becomes more complex on timescales longer than a single orbit, suggestive of additional modes of variability. We also detect a high-frequency soft lag at ~10^{-4}Hz with the magnitude of the delay peaking at, Accepted for publication in MNRAS; 10 pages, 7 figures, 1 table

Fifteen years of XMM-Newton observations have established that ultrafast highly ionized winds (UFOs) are common in radio-quiet active galactic nucleus (AGN). A simple theory of Eddington-limited accretion correctly predicts the typical velocity (∼0.1c) and high ionization of such winds, with observed flow energy capable of ejecting star-forming gas. An extended XMM-Newton observation of the archetypal UFO PG 1211+143 recently found a more complex flow pattern, suggesting that intensive XMM-Newton observations offer exciting potential for probing the inner accretion disk structure and super-massive black hole (SMBH) growth.

An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a complex high velocity outflow, with components distinguished in velocity, ionization and short-term variability. We report here the detection of previously unseen spectral structure in Fe K absorption, finding a second velocity component of the highly ionized wind, apparently co-moving with a low ionization flow detected in the soft X-ray spectrum. Comparison with the first observation in 2001 finds a similar outflow energy rate. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a more complex highly ionized, high velocity outflow. The detection of previously unresolved spectral structure in Fe K absorption finds a second outflow velocity component of the highly ionized wind, with an outflow velocity of v~0.066+/-0.003c, in addition to a still higher velocity outflow of v~0.129+/-0.002c consistent with that first seen in 2001. We note that chaotic accretion, consisting of many prograde and retrograde events, offers an intriguing explanation of the dual velocity wind. In that context the persisting outflow velocities could relate to physically distinct orientations of the inner accretion flow, with prograde accretion yielding a higher launch velocity than retrograde accretion in a ratio close to that observed., Comment: Accepted for publication in MNRAS: 7 pages, 6 figures, 2 tables

Ken Pounds reviews the history of X-ray astronomy in the UK, more than half a century of fruitful science and instrument development.

The analysis of a series of seven observations of the nearby ($z=0.0809$) QSO, PG 1211+143, taken with the Reflection Grating Spectrometer (RGS) on-board XMM-Newton in 2014, are presented. The high resolution soft X-ray spectrum, with a total exposure exceeding 600 ks, shows a series of blue-shifted absorption lines, from the He and H-like transitions of N, O and Ne, as well as from L-shell Fe. The strongest absorption lines are all systematically blue-shifted by $-0.06c$, originating in two absorption zones, from low and high ionization gas. Both zones are variable on timescales of days, with the variations in absorber opacity effectively explained by either column density changes or by the absorber ionization responding directly to the continuum flux. We find that the soft X-ray absorbers probably exist in a two-phase wind, at a radial distance of $10^{17}-10^{18}$ cm from the black hole, with the lower ionization gas as denser clumps embedded within a higher ionization outflow. The overall mass outflow rate of the soft X-ray wind may be as high as $2{\rm M}_{\odot}$ yr$^{-1}$, close to the Eddington rate for PG 1211+143 and similar to that previously deduced from the Fe K absorption., 20 pages, 10 figures, accepted for publication in the Astrophysical Journal

An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 in 2009 revealed an unusually rich absorption spectrum with outflow velocities, in both RGS and EPIC spectra, up to ~ 9000 km/s (Pounds and Vaughan 2011). Evidence was again seen for a fast ionised wind with velocity ~ 0.12c (Tombesi 2010, Pounds and Vaughan 2012). Detailed modelling with the XSTAR photoionisation code now confirms the general correlation of velocity and ionisation predicted by mass conservation in a Compton-cooled shocked wind (King 2010). We attribute the strong column density gradient in the model to the addition of strong two-body cooling in the later stages of the flow, causing the ionisation (and velocity) to fall more quickly, and confining the lower ionisation gas to a narrower region. The column density and recombination timescale of the highly ionised flow component, seen mainly in Fe K lines, determine the primary shell thickness which, when compared with the theoretical Compton cooling length, determines a shock radius of ~ 10^17 cm. Variable radiative recombination continua (RRC) provide a key to scaling the lower ionisation gas, with the RRC flux then allowing a consistency check on the overall flow geometry. We conclude that the 2009 observation of NGC 4051 gives strong support to the idea that a fast, highly ionised wind, launched from the vicinity of the supermassive black hole, will lose much of its mechanical energy after shocking against the ISM at a sufficiently small radius for strong Compton cooling. However, the total flow momentum will be conserved, retaining the potential for a powerful AGN wind to support momentum-driven feedback (King 2003; 2005). We speculate that the `warm absorber' components often seen in AGN spectra result from accumulation of shocked wind and ejected ISM.

An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a more complex high velocity wind, with components distinguished in velocity, ionization level, and column density. Here we report soft x-ray emission and absorption features from the ionized outflow, finding counterparts of both high velocity components, v ~ 0.129c and v ~ 0.066c, recently identified in the highly ionized Fe K absorption spectrum. The lower ionization of the co-moving soft x-ray absorbers imply a distribution of higher density clouds embedded in the main outflow, while much higher column densities for the same flow component in the hard x-ray spectra suggest differing sight lines to the continuum x-ray source., 8 pages, 5 figures, 4 tables; Accepted for publication in MNRAS

An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 in 2009 detected a photo-ionized outflow with a complex absorption line velocity structure and a broad correlation of velocity with ionization parameter, shown in Pounds et al (2011) to be consistent with a highly ionized, high velocity wind running into the interstellar medium or previous ejecta, losing much of its kinetic energy in the resultant strong shock. In the present paper we examine the Fe K spectral region in more detail and find support for two distinct velocity components in the highly ionized absorber, with values corresponding to the putative fast wind (~ 0.12c) and the post-shock flow (v ~ 5000-7000 km/s). The Fe K absorption line structure is seen to vary on a orbit-to-orbit timescale, apparently responding to both a short term increase in ionizing flux and - perhaps more generally - to changes in the soft X-ray (and simultaneous UV) luminosity. The latter result is particularly interesting in providing independent support for the existence of shocked gas being cooled primarily by Compton scattering of accretion disc photons. The Fe K emission is represented by a narrow fluorescent line from near-neutral matter, with a weak red wing modelled here by a relativistic diskline. The narrow line flux is quasi-constant throughout the 45-day 2009 campaign, but is resolved, with a velocity width consistent with scattering from a component of the post-shock flow. Evidence for a P Cygni profile is seen in several individual orbit spectra for resonance transitions in both Fe XXV and Fe XXVI.

An extended XMM-Newton observation of the Seyfert I galaxy NGC 4051 in 2009 revealed a complex absorption spectrum, with a wide range of outflow velocities and ionisation states.The main velocity and ionisation structure was interpreted in Paper I in terms of a decelerating, recombining flow resulting from the shocking of a still higher velocity wind colliding with the ISM or slower moving ejecta. The high sensitivity of the XMM-Newton observation also revealed a number of broad emission lines, all showing evidence of self-absorption near the line cores. The line profiles are found here to be consistent with emission from a limb-brightened shell of post-shock gas building up ahead of the contact discontinuity. While the broad emission lines remain quasi-constant as the continuum flux changes by an order of magnitude, recombination continua of several H- and He-like ions are found to vary in response to the continuum, providing an important key to scaling the ionised flow.

We present an analysis of the high frequency X-ray variability of NGC 4051 (M_BH ~ 1.7*10^6 M_sun) based on a series of XMM-Newton observations taken in 2009 with a total exposure of ~570 ks (EPIC pn). These data reveal the form of the power spectrum over frequencies from 10^-4 Hz, below the previously detected power spectral break, to > 10^-2 Hz, above the frequency of the innermost stable circular orbit (ISCO) around the black hole (nu_ISCO ~ 10^-3 - 10^-2 Hz, depending on the black hole spin parameter j). This is equivalent to probing frequencies >1 kHz in a stellar mass (M_BH ~ 10 Msun) black hole binary system. The power spectrum is a featureless power law over the region of the expected ISCO frequency, suggesting no strong enhancement or change in the variability at the fastest orbital period in the system. Despite the huge amplitude of the flux variations between the observations (peak-to-peak factor of >50) the power spectrum appears to be stationary in shape, and varies in amplitude at all observed frequencies following the previously established linear rms-flux relation. The rms-flux relation is offset in flux by a small and energy-dependent amount. The simplest interpretation of the offset is in terms of a very soft spectral component that is practically constant (compared to the primary source of variability). One possible origin for this emission is a circumnuclear shock energised by a radiatively driven outflow from the central regions, and emitting via inverse-Compton scattering of the central engine's optical-UV continuum (as inferred from a separate analysis of the energy spectrum). A comparison with the power spectrum of a long XMM-Newton observation taken in 2001 gives only weak evidence for non-stationarity in power spectral shape or amplitude. [Abridged]

An extended XMM-Newton observation of the Seyfert 1 galaxy NGC 4051 has revealed a rich absorption line spectrum indicating the presence of a photoionized outflow with a wide range of velocities and ionization parameter. At low continuum fluxes an emission line spectrum is well defined with both narrow and broad components of several abundant metal ions. The absorption line velocity structure and a broad correlation of velocity and ionization parameter are consistent with an outflow scenario where a highly ionized, high velocity wind, perhaps launched during intermittent super-Eddington accretion, runs into the interstellar medium or previous ejecta, losing much of its kinetic energy in the resultant strong shock. We explore the possibility that a quasi-constant soft X-ray emission component may be evidence of this post-shock cooling. This revised view of AGN outflows is consistent with multiple minor Eddington accretion episodes creating a momentum-driven feedback linking black hole and host galaxy growth.

Chandra observations of the type 1.8, low-redshift (z = 0.115), red (J − KS ~ 2) quasar 2MASSJ 104943+583750 (2M1049+5837) indicated an unusually hard X-ray spectrum (HR ~ 0.6), suggesting obscuration of NH ~ 4 × 1022 cm−2 and a flat Γ ~ 0.4 power-law slope. A higher signal-to-noise ratio XMM-Newton observation reported here reveals a more complex spectrum, being extremely hard above ~2 keV, Γ ~ − 0.6, with a well-defined soft excess similar to the bright, nearby Seyfert 2 galaxy Mrk 3. Such extremely hard quasar spectra cannot be a dominant contributor to the cosmic X-ray background (CXRB; Γ ~ 1.4). Modeling of 2M1049+5837 shows the observed 2-10 keV spectrum to be the sum of a strongly absorbed "normal" Γ ~ 1.8 underlying quasar X-ray continuum, and a cold reflection component (R ~ 2). The strong attenuation of the intrinsic X-ray continuum by a sub-Compton-thick line-of-sight column, NH ~ 3.4 × 1023 cm−2, reveals a soft X-ray emission component whose spectrum indicates reprocessing/emission from, possibly extended, photoionized gas. The luminosity of the soft X-ray component is similar to Seyfert 2 galaxies, an order of magnitude less than comparable type 1 AGNs, suggesting partial obscuration of core-bright emission. The optical emission is complex, with distinct red and blue scattered light components believed to originate in two extended regions visible in HST imaging data. The unusual combination of properties: optical and X-ray obscuration of the nuclear emission, partially obscured broad but unobscured narrow emission lines, and partially obscured soft X-ray excess, implies an intermediate viewing angle, over or through the edge of an obscuring disk + wind or torus. 2M1049+5837 again demonstrates both the ambiguity of low signal-to-noise X-ray spectra/hardness ratios and the potential of 2MASS-selected red sources for exploring the complex obscuration and geometry of the nuclear regions in AGNs.

We use the full broad-band XMM-Newton EPIC data to examine the X-ray spectrum of the nearby Seyfert 2 galaxy NGC 1068, previously shown to be complex with the X-ray continuum being a sum of components reflected/scattered from cold (neutral) and warm (ionised) matter, together with associated emission line spectra. We quantify the neutral and ionised reflectors in terms of the luminosity of the hidden nucleus. Both are relatively weak, a result we interpret on the Unified Seyfert Model by a near side-on view to the putative torus, reducing the visibility of the illuminated inner surface of the torus (the cold reflector), and part of the ionised outflow. A high inclination in NGC 1068 also provides a natural explanation for the large (Compton-thick) absorbing column in the line-of-sight to the nucleus. The emission line fluxes are consistent with the strength of the neutral and ionised continuum components, supporting the robustness of the spectral model., 8 pages. 7 figures. Accepted for publication in MNRAS

We report on the analysis of a short XMM-Newton observation of the reddened Type 1 QSO 2MASS 234449+1221 first identified in the Two Micron All-Sky Survey. The underlying X-ray continuum is found to be typical of a broad-line active galaxy, with photon index Gamma ~ 1.9. Low energy absorption can be modelled by a column N_H ~ 10^22 cm^{-2} of moderately ionised gas or a smaller column of cold gas. Addition of a soft X-ray emission component significantly improves the fit in both cases. With the assumption that the soft X-ray flux represents emission from gas photoionised by the incident X-ray continuum, a comparison of the absorbed and emitted luminosities indicates a covering factor of ~ 8-17%. The unusual opportunity to simultaneously observe and quantify ionised absorption and emission in 2MASS 234449+1221 is due to the relatively large opacity (for a Type 1 AGN) of the absorbing gas, which depresses the normally strong continuum below ~ 1 keV. A comparison of the soft X-ray emission of 2MASS 234449+1221 with that of other Type 1 and Type 2 AGN suggests the existence of an inner turbulent extension to ionised outflows, not detected in current high resolution X-ray spectra.

A 100-ks XMM–Newton observation of the nearby Seyfert 2 galaxy Mkn 3 offers a unique opportunity to explore the complexity of its X-ray spectrum. We find the ∼3–8 keV continuum to be dominated by reflection from cold matter, with fluorescent K-shell lines detected from Ni, Fe, Ca, Ar, S, Si and Mg. At higher energies an intrinsic power-law continuum, with canonical Seyfert 1 photon index, is seen through a near-Compton-thick cold absorber. A soft excess below ∼3 keV is found to be dominated by line emission from an outflow of ‘warm’ gas, photoionized and photoexcited by the intrinsically strong X-ray continuum. Measured blueshifts in the strong Fe Kα and O vii and O viii emission lines are discussed in terms of the properties of the putative molecular torus and ionized outflow.

An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 in September 2002, when the source was in an extreme low-flux state, found a very hard X-ray spectrum at 1-10 keV with a strong soft excess below ~1 keV. Comparison with an earlier XMM-Newton observation when 1H 0419-577 was `X-ray bright' indicated the dominant spectral variability was due to a steep power law or cool Comptonised thermal emission. Four further XMM-Newton observations, with 1H 0419-577 in intermediate flux states, now support that conclusion, while we also find the variable emission component in intermediate state difference spectra to be strongly modified by absorption in low ionisation matter. The variable `soft excess' then appears to be an artefact of absorption of the underlying continuum while the `core' soft emission can be attributed to recombination in an extended region of more highly ionised gas. We note the wider implications of finding substantial cold dense matter overlying (or embedded in) the X-ray continuum source in a luminous Seyfert 1 galaxy., Comment: 34 pages, 15 figures, submitted to ApJ

Following the discovery of X-ray absorption in a high velocity outflow from the bright quasar PG1211+143 we have searched for similar features in XNN-Newton archival data of a second (high accretion rate) quasar PG0844+349. Evidence is found for several faint absorption lines in both the EPIC and RGS spectra, whose most likely identification with resonance transitions in H-like Fe, S, and Ne implies an origin in highly ionised matter with an outflow velocity of order ∼0.2c. The line equivalent widths require a line-of-sight column density of NH∼4×1023 cm−2, at an ionisation parameter of logξ∼3.7. Assuming a radial outflow being driven by radiation pressure from the inner accretion disc, as suggested previously for PG1211+143, the flow in PG0844+349 is also likely to be optically thick, in this case within ∼25 Schwarzschild radii. We suggest that a high velocity, highly ionised outflow may be a significant component in the mass and energy budgets of AGN accreting at or above the Eddington rate.

We report on observations of the iron K line in the nearby Seyfert 1 galaxy, NGC 3783, obtained in a long, 2 orbit (240 ks) XMM-Newton observation. The line profile obtained exhibits two strong narrow peaks at 6.4 keV and at 7.0 keV, with measured line equivalent widths of 120 and 35 eV respectively. The 6.4 keV emission is the K-alpha line from near neutral Fe, whilst the 7.0 keV feature probably originates from a blend of the neutral Fe K-beta line and the H-like line of Fe at 6.97 keV. The relatively narrow velocity width of the K-alpha line (, 34 pages, including 11 figures. Accepted for publication in ApJ

Following the discovery of X-ray absorption in a high velocity outflow from the bright quasar PG1211+143 we have searched for similar features in XMM archival data of a second (high accretion rate) quasar PG0844+349. Evidence is found for absorption lines in both the EPIC and RGS spectra, whose identification with resonance transitions in H-like Fe, S, and Ne implies an origin in highly ionised matter with an outflow velocity of order ~0.2c. The line equivalent widths require a line-of-sight column density of N_H ~ 4 x 10^23 cm^-2, at an ionisation parameter of log(xi) ~ 3.7. Assuming a radial outflow being driven by radiation pressure from the inner accretion disc, as suggested previously for PG1211+143, the flow is again likely to be optically thick, in this case within ~ 25 Schwarzschild radii. We suggest that a high velocity, highly ionised outflow is likely to be a significant component in the mass and energy budgets of many AGN accreting at or above the Eddington rate., Comment: 7 pages, 4 figures, accepted by MNRAS

We report on the analysis of a long XMM-Newton EPIC observation in 2001 May of the Narrow Line Seyfert 1 galaxy Mkn 766. The 3-11 keV spectrum exhibits a moderately steep power law continuum, with a broad emission line at ~6.7 keV, probably blended with a narrow line at ~6.4 keV, and a broad absorption trough above ~8.7 keV. We identify both broad spectral features with reprocessing in He-like Fe. An earlier XMM-Newton observation of Mkn 766 in 2000 May, when the source was a factor ~2 fainter, shows a similar broad emission line, but with a slightly flatter power law and absorption at a lower energy. In neither observation do we find a requirement for the previously reported broad 'red wing' to the line and hence of reflection from the innermost accretion disc. More detailed examination of the longer XMM-Newton observation reveals evidence for rapid spectral variability in the Fe K band, apparently linked with the occurrence of X-ray 'flares'. A reduction in the emission line strength and increased high energy absorption during the X-ray flaring suggests that these transient effects are due to highly ionised ejecta associated with the flares. Simple scaling from the flare avalanche model proposed for the luminous QSO PDS 456 (Reeves etal. 2002) confirms the feasibility of coherent flaring being the cause of the strong peaks seen in the X-ray light curve of \mkn., 9 pages, 11 figures, submitted to MNRAS

We report the spectral analysis of a long XMM-Newton observation of the well-studied, moderate luminosity Broad Line Seyfert 1 galaxy NGC 5548. The source was at an historically average brightness and we find the hard (3-10 keV) spectrum can be well fitted by a power law of photon index gamma ~ 1.75, together with reflection. The only feature in the hard X-ray spectrum is a narrow emission line near 6.4 keV, with an equivalent width of ~ 60 eV. The energy and strength of this line is consistent with fluorescence from `neutral' iron distant from the central continuum source. We find no evidence for a broad Fe K line, with an upper limit well below previous reports, suggesting the inner accretion disc is now absent or highly ionised. The addition of simultaneous BeppoSAX data allows the analysis to be extended to 200 keV, yielding important constraints on the total reflection. Extrapolation of the hard X-ray power law down to 0.3 keV shows a clear `soft excess' below ~ 0.7 keV. After due allowance for the effects of a complex warm absorber, measured with the XMM-Newton RGS, we find the soft excess is better described as a smooth upward curvature in the continuum flux below ~ 2 keV. The soft excess can be modelled either by Comptonised thermal emission or by enhanced reflection from the surface of a highly ionised disc., Comment: 9 pages, 11 figures, accepted by MNRAS; minor changes to text and figures

We report on a timing analysis of a new ~630ks XMM-Newton observation of the quasar, PG 1211+143. We find a well-defined X-ray power spectrum with a well-detected bend at ~7e-5 Hz, consistent with the established bend-timescale--black-hole-mass correlation for luminous, accreting black holes. We find the linear rms-flux relation commonly observed in accreting black hole systems and investigate the energy-dependence of the rms. The fractional rms is roughly constant with energy on short timescales (< 1 day; within observations) whereas there is enhanced soft band variability on long timescales (between observations typically spaced by a few days). Additionally, we also report on the optical--UV variability using the OM on-board XMM-Newton and a ~2-month-long overlapping monitoring programme with Swift. We find that, although there is little UV variability within observations (, Accepted for publication in MNRAS (14 pages, 13 figures, 4 tables)

Active Galactic Nuclei (AGN) represent the growth phases of the supermassive black holes in the center of almost every galaxy. Powerful, highly ionized winds, with velocities $\sim 0.1- 0.2c$ are a common feature in X--ray spectra of luminous AGN, offering a plausible physical origin for the well known connections between the hole and properties of its host. Observability constraints suggest that the winds must be episodic, and detectable only for a few percent of their lifetimes. The most powerful wind feedback, establishing the $M -\sigma$ relation, is probably not directly observable at all. The $M - \sigma$ relation signals a global change in the nature of AGN feedback. At black hole masses below $M-\sigma$ feedback is confined to the immediate vicinity of the hole. At the $M-\sigma$ mass it becomes much more energetic and widespread, and can drive away much of the bulge gas as a fast molecular outflow., Comment: To appear in Annual Reviews of Astronomy and Astrophysics, Vol 53. 44 pages, 10 figures

The bright, soft X-ray spectrum Seyfert 1 galaxies Ark 564 and Ton S180 were monitored for 35 days and 12 days with ASCA and RXTE (and EUVE for Ton S180). The short time scale (hours-days) variability patterns were very similar across energy bands, with no evidence of lags between any of the energy bands studied. The fractional variability amplitude was almost independent of energy band. It is difficult to simultaneously explain soft Seyferts stronger variability, softer spectra, and weaker energy-dependence of the variability relative to hard Seyferts. The soft and hard band light curves diverged on the longest time scales probed, consistent with the fluctuation power density spectra that showed relatively greater power on long time scales in the softest bands. The simplest explanation is that a relatively hard, rapidly-variable component dominates the total X-ray spectrum and a slowly-variable soft excess is present in the lowest energy channels of ASCA. Although it would be natural to identify the latter with an accretion disk and the former with a corona surrounding it, a standard thin disk could not get hot enough to radiate significantly in the ASCA band, and the observed variability time scales are much too short. The hard component may have a more complex shape than a pure power-law. The most rapid factor of 2 flares and dips occurred within ~1000 sec in Ark 564 and a bit more slowly in Ton S180. The speed of the luminosity changes rules out viscous or thermal processes and limits the size of the individual emission regions to

Now that gamma-ray bursts (GRBs) have been determined to lie at cosmological distances, their isotropic burst energies are estimated to be as high as 1054 erg (ref. 2), making them the most energetic phenomena in the Universe. The nature of the progenitors responsible for the bursts remains, however, elusive. The favoured models range from the merger of two neutron stars in a binary system to the collapse of a massive star. Spectroscopic studies of the afterglow emission could reveal details of the environment of the burst, by indicating the elements present, the speed of the outflow and an estimate of the temperature. Here we report an X-ray spectrum of the afterglow of GRB011211, which shows emission lines of magnesium, silicon, sulphur, argon, calcium and possibly nickel, arising in metal-enriched material with an outflow velocity of the order of one-tenth the speed of light. These observations strongly favour models where a supernova explosion from a massive stellar progenitor precedes the burst event and is responsible for the outflowing matter.

Beginning in 1999 January, the bright, strongly variable Narrow-Line Seyfert 1 (NLS1) galaxy Akn 564 has been observed by RXTE once every ~4.3 days. It was also monitored every ~3.2 hr throughout 2000 July. These evenly-sampled observations have allowed the first quantitative comparison of long and short time-scale X-ray variability in an NLS1 and the derivation of an X-ray Power Density Spectrum (PDS). The variability amplitude in the short time-scale light curve is very similar to that in the long time-scale light curve, in marked contrast to the stronger variability on longer time-scales which is characteristic of "normal" broad-line Seyfert 1s (BLS1s). Furthermore, the Akn 564 PDS power law cuts off at a frequency of 8.7x10^-7 Hz corresponding to a timescale of ~13 d, significantly shorter than that seen in the PDS of NGC 3516, a BLS1 of comparable luminosity. This result is consistent with NLS1s showing faster (as opposed to larger amplitude) variations than BLS1s, providing further evidence that NLS1s harbour lower mass black holes than BLS1s of similar luminosity, accreting at a correspondingly higher relative rate., Accepted for publication in ApJ

We present XMM-Newton observations of the high redshift z=3.104, radio-loud quasar PKS 0537-286. The EPIC CCD cameras provide the highest signal-to-noise spectrum of a high-z quasar to date. The EPIC observations show that PKS 0537-286 is extremely X-ray luminous (Lx=2x10^47 erg/s), with an unusually hard X-ray spectrum (Gamma=1.27+/-0.02). The flat power-law emission extends over the whole observed energy range; there is no evidence of intrinsic absorption, which has been claimed in PKS 0537-286 and other high z quasars. However, there is evidence for weak Compton reflection. A redshifted iron K line, observed at 1.5 keV - corresponding to 6.15 keV in the quasar rest frame - is detected at 95% confidence. If confirmed, this is the most distant iron K line known. The line equivalent width is small (33eV), consistent with the `X-ray Baldwin effect' observed in other luminous quasars. The reflected continuum is also weak (R=0.25). We find the overall spectral energy distribution of PKS 0537-286 is dominated by the X-ray emission, which, together with the flat power-law and weak reflection features, suggests that the X-radiation from PKS 0537-286 is dominated by inverse Compton emission associated with a face-on relativistic jet., Comment: 6 pages, accepted for publication in Astronomy and Astrophysics Letters

We present XMM-Newton observations of the bright quasar PKS0558-504. The 0.2-10 keV spectrum is dominated by a large, variable soft X-ray excess. The fastest flux variations imply accretion onto a Kerr black hole. The XMM-Newton data suggest the presence of a `big blue bump' in PKS0558-504 extending from the optical band to ~3 keV. The soft X-ray spectrum shows no evidence for significant absorption or emission-line features. The most likely explanation for the hot big blue bump is Comptonization by the multi-temperature corona of a thermal accretion disc running at a high accretion rate., Accepted for publication in A&A special issue on first results from XMM

July 20th 1969 was a day - or night - that almost everyone over the age of 40 remembers. At least that is the message from a straw poll of colleagues in my Department at Leicester, which revealed a fascinating variety of responses to the question, `where were you when man first set foot on the Moon?', and ranged from sitting in the JCR at a Cambridge college, to washing dishes in a New York drugstore, and at home with mum and dad. Jonathan Allday's new book Apollo in Perspective reflects the author's recognition that the Apollo programme, the largest, most complex and costly civil project of the 20th century, invites a different response from the generations of over- and under-40s. Awareness of that different generational perception of the early days of the Space Programme is one I can share, from my daily interaction with our space science undergradute students in Leicester. Apollo in Perspective is an enjoyable and informative read, written with humour and authority. Major use has clearly been made of official NASA material, some of which is now available on the Web. The description of the Apollo programme is detailed and technical at a level which should be comfortable for A-level science students. The basic physics of propulsion, inertial guidance and orbital dynamics are well explained, as well as the challenging human and political aspects of the Apollo programme. Specialist sections deal with the giant Saturn V launcher and the pre-Apollo Mercury and Gemini programmes. After a stage-by-stage review of Apollo, the final third of the book goes on to describe the Space Shuttle programme, manned stations from Skylab to Mir, and brings the reader up to date (or at least to mid-1999) with a description of the evolving International Space Station. Finally, taking the longer view, that space travel may determine the ultimate destiny of mankind, the book concludes with chapters on exploration of Mars and some imaginative speculation on how future humans might make the ultimate `journey to the stars'. All in all, this is a book I would recommend to both pre- and post-Apollo generations interested in space exploration. Appendices giving details of all the Apollo missions, stages in the development of the Saturn V rocket, relevant maths and further reading (including useful websites) add to the overall value.

ABSTRA C T We present simultaneous ASCA and RXTE observations of Ark 564, the brightest known ‘narrow-line’ Seyfert 1 in the 2‐10 keV band. The measured X-ray spectrum is dominated by a steepOG < 2:7U power-law continuum extending to at least 20 keV, with imprinted Fe K-line and edge features and an additional ‘soft excess’ below ,1:5 keV. The energy of the iron K-edge indicates the presence of highly ionized material, which we identify in terms of reflection from a strongly irradiated accretion disc. The high reflectivity of this putative disc, together with its strong intrinsic O viii Lya and O viii recombination emission, can also explain much of the observed soft excess flux. Furthermore, the same spectral model also provides a reasonable match to the very steep 0.1‐2 keV spectrum deduced from ROSAT data. The source is much more rapidly variable than ‘normal’ Seyfert 1s of comparable luminosity, increasing by a factor of ,50 per cent in 1.6 h, with no measurable lag between the 0.5‐2 keV and 3‐12 keV bands, consistent with much of the soft excess flux arising from reprocessing of the primary power-law component in the inner region of the accretion disc. We note, finally, that if the unusually steep power-law component is a result of Compton cooling of a disc corona by an intense soft photon flux, then the implication is that the bulk of these soft photons lie in the unobserved extreme ultraviolet.

We consider how the radiation pressure of an accreting supermassive black hole (SMBH) affects the interstellar medium around it. Much of the gas originally surrounding the hole is swept into a shell with a characteristic radius somewhat larger than the black hole's radius of influence (∼1-100 pc). The shell has a mass directly comparable to the (M-σ) mass that the hole will eventually reach, and may have a complex topology. We suggest that outflows from the central SMBHs are halted by collisions with the shell, and that this is the origin of the warm absorber components frequently seen in active galactic nucleus (AGN) spectra. The shell may absorb and reradiate some of the black hole accretion luminosity at long wavelengths, implying both that the bolometric luminosities of some known AGN may have been underestimated, and that some accreting SMBH may have escaped detection entirely.

Although General Relativity had provided the physical basis of black holes, evidence for their existence had to await the Space Era when X-ray observations first directed the attention of astronomers to the unusual binary stars Cygnus X-1 and A0620-00. Subsequently, a number of faint Ariel 5 and Uhuru sources, mainly at high Galactic latitude, were found to lie close to bright Seyfert galaxies,suggesting the nuclear activity in AGN might also be driven by accretion in the strong gravity of a black hole. Detection of rapid X-ray variability with EXOSAT later confirmed that the accreting object in AGN was almost certainly a supermassive black hole., 15 pages, 11 figures. To be published in Space Science Reviews and as hard cover in the Space Science Series of ISSI: The Physics of Accretion onto Black Holes (Springer Publisher)

Highly ionised winds with velocities ~ 0.1-0.2c were first detected in X-ray spectra of non-BAL AGN a decade ago. Subsequent observations and archival searches have shown such winds to be a common feature of luminous AGN, increasing the belief that powerful ionised winds have a wider importance in galaxy feedback models. Paradoxically, for the best-quantified high velocity outflow (the luminous Seyfert PG1211+143) the wind appears too powerful to be compatible with the observed stellar bulge and black hole masses, suggesting the energy coupling of wind to bulge gas must be inefficient. A recent XMM-Newton observation of the narrow line Seyfert NGC 4051 offers an explanation of this apparent paradox, finding evidence for the fast ionised wind to lose most of its kinetic energy after shocking against the ISM. Importantly, the wind momentum is maintained through such a shock, supporting the view that a momentum-driven flow provides the critical link between black hole and stellar bulge masses implied by the observed M-sigma relationship., Comment: 14 pages, 7 figures To be published in Space Science Reviews and as hard cover in the Space Science Series of ISSI: The Physics of Accretion onto Black Holes (Springer Publisher)

An XMM-Newton observation of the luminous Seyfert galaxy PG1211+143 in 2001 revealed the first clear evidence for a highly ionised high speed wind (in a non-BAL AGN), with a velocity of v~0.09c based on the identification of blue-shifted absorption lines in both EPIC and RGS spectra. A subsequent analysis of EPIC spectra, including additional absorption lines, led to an upward revision of the wind speed to ~0.14c, while broad band modelling indicated the need for a second, partial covering absorber to account for continuum curvature and spectral variability. We show here, in a new analysis of the XMM-Newton RGS data, that this additional absorber is detected in the soft X-ray spectra, with the higher spectral resolution providing a much improved velocity constraint, with v~0.07c. Similar variability of the 0.07c and 0.14c outflow components suggest they are physically linked, and we speculate that occurs by the fast (primary) wind impacting on small clumps of higher density, slow moving matter close to the disc. We show that strong, velocity broadened soft X-ray emission features, located at the redshift of PG1211+143, indicate the extended scale of the ionised outflow., Comment: 7 pages, 4 figures, submitted to MNRAS

We analyze the broad-band X-ray spectrum (0.3-50 keV) of the luminous Seyfert 1 / quasar PG 1211+143 - the archetypal source for high-velocity X-ray outflows - using near-simultaneous XMM-Newton and NuSTAR observations. We compare pure relativistic reflection models with a model including the strong imprint of photoionized emission and absorption from a high-velocity wind (Pounds16a,16b), finding a spectral fit that extrapolates well over the higher photon energies covered by NuSTAR. Inclusion of the high S/N XMM-Newton spectrum provides much tighter constraints on the model parameters, with a much harder photon index / lower reflection fraction compared to that from the NuSTAR data alone. We show that pure relativistic reflection models are not able to account for the spectral complexity of PG 1211+143 and that wind absorption models are strongly required to match the data in both the soft X-ray and Fe K spectral regions. In confirming the significance of previously reported ionized absorption features, the new analysis provides a further demonstration of the power of combining the high throughput and resolution of long-look XMM-Newton observations with the unprecedented spectral coverage of NuSTAR., Comment: Accepted for publication in ApJ; 9 pages, 6 figures, 2 tables

XMM–Newton is a space science mission developed and operated by the European Space Agency. We acknowledge the excellent work of ESA staff in Madrid in planning and conducting the XMM–Newton observations. The UK Science and Technology Facilities Council funded the post-doctoral research assistantship of AL.

Zwicky 159.034, one of the Seyfert galaxies identified with EUV sources detected during the ROSAT Wide Field Camera (WFC) all-sky survey, has unusual properties. The ROSAT Position Sensitive Proportional Counter (PSPC) 0.1--2.5 keV X-ray spectrum, obtained simultaneously with the WFC survey, appears extremely steep. Subsequent deeper pointed observations with ROSAT revealed that its 0.1--2.5 keV count rate had decreased by an extremely large amount (a factor of about 70). This is comparable to the variability amplitude seen in another ultrasoft Seyfert, E1615+061. There appears to be about 10 times as much flux in the soft component as in any expected hard tail suggesting that, in the absence of partial covering of the hard flux, the soft flux cannot arise via reprocessing of the hard tail. Its peculiar optical spectrum has permitted lines with widths about 1200--1500 km s^{-1}, and forbidden lines are weak or absent. Its optical spectrum shows evidence for variability, and might be used to study the role reprocessed X-rays play in the formation of optical lines.

We have carried out a soft X-ray survey of the sky using the ROSAT Position Sensitive Proportional Counter (PSPC) in a region of very low Galactic column density (NH = 6–9 × 1019 cm–2). The data consist of a deep > 70 ks pointing (the Deep Survey) and six pointings at lower sensitivity (13–20 ks; the Medium Survey). We detect a total of 141 sources over the 0.9 deg2 of sky area used. The faintest source detected has a flux of 3.2 × 10–15 erg cm–2 s–1 (0.5–2.0 keV). We present the source number-flux distribution, and we compare it with the distributions constructed from other ROSAT observations and from surveys carried out with X-ray instruments operating at higher energies. We estimate the contribution of the resolved sources to the soft X-ray background by direct comparison of their integrated spectrum with that of the diffuse background: 44 per cent of the extragalactic X-ray background between 0.5 and 2.0 keV is resolved directly into discrete sources whose average spectrum is steeper than that of the background. Integration of our number-flux relation to infinite flux produces a background resolved fraction of 44±565 per cent (0.5–2.0 keV). Limits on the slope of the log N–log S curve at very faint fluxes are set by the measured value of the X-ray background., KOM, ACF and RGM acknowledge the support of the Royal Society.

Absorption and reprocessing of X-ray photons in the nuclei of active galaxies have recently been found to alter significantly the appearance of the emergent spectrum. The limited bandwidth and resolution of most contemporary X-ray spectral data often leave open differing interpretations of the nature and magnitude of these effects and, consequently, the precise form of the underlying continuum spectrum. A unique opportunity to examine, over some two decades in energy, the X-ray spectra of five bright Seyfert galaxies, based on simultaneous observations with the Ginga and ROSAT satellites, has now provided data to clarify the form of this reprocessing

The history and the present status of X-ray observations of AGN are outlined with reference to Seyfert Is, Seyfert IIs, and quasars. Fe K emission lines, other distortions at E greater tha 6 keV, excess emission below 2 keV, absorption, and ionized material are discussed. The continuum flux variability and line variability in Seyfert Is and the continuum variability in Seyfert IIs are examined. Models and theories of the continuum are reviewed, and the total energy budget of AGN and their similarity to Galactic black holes are also discussed.