Outputs (292)

What drives the variability in AGN? Explaining the UV-Xray disconnect through propagating fluctuations (2024)
Journal Article

Intensive broad-band reverberation mapping campaigns have shown that AGN variability is significantly more complex than expected from disc reverberation of the variable X-ray illumination. The UV/optical variability is highly correlated and lagged, w... Read More about What drives the variability in AGN? Explaining the UV-Xray disconnect through propagating fluctuations.

The Peculiar Bursting Nature of CP Pup (2024)
Journal Article

The classical nova CP Puppis has been observed to have particularly puzzling and peculiar properties. In particular, this classical nova displays occasional bursts in its long-term ASAS-SN light curve. Here, we report on five sectors of TESS data dis... Read More about The Peculiar Bursting Nature of CP Pup.

Disc corona radii and QPO frequencies in black hole binaries: testing Lense– Thirring precession origin (2024)
Journal Article

Stellar-mass black hole binary systems in the luminous X-ray states show a strong quasi-periodic oscillation (QPO) in their Comptonized emission. The frequency of this feature correlates with the ratio of a disc to Comptonized emission rather than wi... Read More about Disc corona radii and QPO frequencies in black hole binaries: testing Lense– Thirring precession origin.

Probing the face-on disc-corona system of the bare AGN Mrk 110 from UV to hard X-rays: A moderate changing-state AGN? (2024)
Journal Article

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

X-ray polarization properties of thermal-radiative disc winds in binary systems (2023)
Journal Article

New X-ray polarization results are challenging our understanding of the accretion flow geometry in black hole binary systems. Even spectra dominated by a standard disc can give unexpected results, such as the high-inclination black hole binary 4U 163... Read More about X-ray polarization properties of thermal-radiative disc winds in binary systems.

HYPerluminous quasars at the Epoch of ReionizatION (HYPERION): A new regime for the X-ray nuclear properties of the first quasars (2023)
Journal Article

The existence of luminous quasars (QSOs) at the epoch of reionization (EoR; i.e., z > 6) powered by well-grown supermassive black holes (SMBHs) with masses ≳109 M⊙ challenges models of early SMBH formation and growth. To shed light on the nature of t... Read More about HYPerluminous quasars at the Epoch of ReionizatION (HYPERION): A new regime for the X-ray nuclear properties of the first quasars.

Wavelength dependences of the optical/UV and X-ray luminosity correlations of quasars (2023)
Journal Article

The interband correlations between optical/ultraviolet (UV) and X-ray luminosities of active galactic nuclei (AGNs) are important for understanding the disc–coronal connection, as well as using AGN as standard candles for cosmology. It is convention... Read More about Wavelength dependences of the optical/UV and X-ray luminosity correlations of quasars.

Estimating black hole spin from AGN SED fitting: the impact of general-relativistic ray tracing (2023)
Journal Article

Accretion disc model fitting to optical/UV quasar spectra requires that the highest mass black holes have the highest spin, with implications on the hierarchical growth of supermassive black holes and their host galaxies over cosmic time. However, th... Read More about Estimating black hole spin from AGN SED fitting: the impact of general-relativistic ray tracing.

The origin of long soft lags and the nature of the hard-intermediate state in black hole binaries (2023)
Journal Article

Fast variability of the X-ray corona in black hole binaries can produce a soft lag by reverberation, where the reprocessed thermalized disc photons lag behind the illuminating hard X-rays. This lag is small, and systematically decreases with increasi... Read More about The origin of long soft lags and the nature of the hard-intermediate state in black hole binaries.

The SOUX AGN sample: optical/UV/X-ray SEDs and the nature of the disc (2023)
Journal Article

We use the SOUX sample of ∼700 active galactic nucleus (AGN) to form average optical-ultraviolet (UV)-X-rays spectral energy distributions (SEDs) on a two-dimensional (2D) grid of MBH and L2500. We compare these with the predictions of a new AGN SED... Read More about The SOUX AGN sample: optical/UV/X-ray SEDs and the nature of the disc.

A different view of wind in X-ray binaries: the accretion disc corona source 2S 0921-630 (2023)
Journal Article

Accretion disc coronae (ADC) sources are very high inclination neutron star or black hole binaries, where the outer accretion flow blocks a direct view of the central source. The weak observed X-ray emission is instead produced mainly by scattering o... Read More about A different view of wind in X-ray binaries: the accretion disc corona source 2S 0921-630.

Tracking the spectral properties of ESO 511-G030 across different epochs (2023)
Journal Article

The Type 1 active galactic nucleus (AGN) ESO 511-G030, a formerly bright and soft excess dominated source, was observed in 2019 in the context of a multi-wavelength monitoring campaign. In the new exposures, the source was found to be in a flux state... Read More about Tracking the spectral properties of ESO 511-G030 across different epochs.

Modelling continuum reverberation in active galactic nuclei: a spectral-timing analysis of the ultraviolet variability through X-ray reverberation in Fairall 9 (2023)
Journal Article

Continuum reverberation mapping of active galactic nuclei (AGNs) can provide new insight into the nature and geometry of the accretion flow. Some of the X-rays from the central corona irradiating the disc are absorbed, increasing the local disc tempe... Read More about Modelling continuum reverberation in active galactic nuclei: a spectral-timing analysis of the ultraviolet variability through X-ray reverberation in Fairall 9.

The SOUX AGN sample: SDSS–XMM-Newton optical, ultraviolet, and X-ray selected active galactic nuclei spanning a wide range of parameter space – sample definition (2023)
Journal Article

We assemble a sample of 696 type 1 active galactic nuclei (AGN) up to a redshift of z = 2.5, all of which have an SDSS spectrum containing at least one broad emission line (H α, H β, or Mg II) and an XMM-Newton X-ray spectrum containing at least 250... Read More about The SOUX AGN sample: SDSS–XMM-Newton optical, ultraviolet, and X-ray selected active galactic nuclei spanning a wide range of parameter space – sample definition.

The radio detection and accretion properties of the peculiar nuclear transient AT 2019avd (2023)
Journal Article

AT 2019avd is a nuclear transient detected from infrared to soft X-rays, though its nature is yet unclear. The source has shown two consecutive flaring episodes in the optical and the infrared bands, and its second flare was covered by X-ray monitori... Read More about The radio detection and accretion properties of the peculiar nuclear transient AT 2019avd.

MAXI J1820+070 X-ray spectral-timing reveals the nature of the accretion flow in black hole binaries (2023)
Journal Article

Black hole X-ray binaries display significant stochastic variability on short time-scales (0.01–100 s), with a complex pattern of lags in correlated variability seen in different energy bands. This behaviour is generally interpreted in a model where... Read More about MAXI J1820+070 X-ray spectral-timing reveals the nature of the accretion flow in black hole binaries.

The extreme super-eddington NLS1 RX J0134.2-4258 – II. A weak-line Seyfert linking to the weak-line quasar (2022)
Journal Article

QWIND3: UV line-driven accretion disc wind models for AGN feedback (2022)
Journal Article

The ultraviolet (UV) bright accretion disc in active galactic nuclei (AGNs) should give rise to line driving, producing a powerful wind that may play an important role in AGN feedback as well as in producing structures like the broad-line region. How... Read More about QWIND3: UV line-driven accretion disc wind models for AGN feedback.

What powers the wind from the black hole accretion disc in GRO J1655-40? (2022)
Journal Article

Black hole accretion discs can produce powerful outflowing plasma (disc winds), seen as blue-shifted absorption lines in stellar and supermassive systems. These winds in Quasars have an essential role in controlling galaxy formation across cosmic tim... Read More about What powers the wind from the black hole accretion disc in GRO J1655-40?.

Localized thermonuclear bursts from accreting magnetic white dwarfs (2022)
Journal Article

Nova explosions are caused by global thermonuclear runaways triggered in the surface layers of accreting white dwarfs1,2,3. It has been predicted4,5,6 that localized thermonuclear bursts on white dwarfs can also take place, similar to type-I X-ray bu... Read More about Localized thermonuclear bursts from accreting magnetic white dwarfs.

Multiwavelength campaign on the Super-Eddington NLS1 RX J0134.2-4258 – I. Peculiar X-ray spectra and variability (2022)
Journal Article

We have conducted a new long-term multiwavelength campaign on one of the most super-Eddington narrow-line Seyfert 1s (NLS1s) known, namely RX J0134.2-4258. In this first paper, we report deep simultaneous X-ray observations performed by XMM–Newton an... Read More about Multiwavelength campaign on the Super-Eddington NLS1 RX J0134.2-4258 – I. Peculiar X-ray spectra and variability.

Origins of the UV/X-ray relation in Arakelian 120 (2022)
Journal Article

We explore the accretion geometry in Arakelian 120 using intensive UV and X-ray monitoring from Swift. The hard X-rays (1–10 keV) show large amplitude, fast (few-day) variability, so we expect reverberation from the disc to produce UV variability fro... Read More about Origins of the UV/X-ray relation in Arakelian 120.

A multi-wavelength view of distinct accretion regimes in the pulsating ultraluminous X-ray source NGC 1313 X-2 (2022)
Journal Article

NGC 1313 X-2 is one of the few known pulsating ultraluminous X-ray sources (PULXs), and so is thought to contain a neutron star that accretes at highly super-Eddington rates. However, the physics of this accretion remains to be determined. Here, we r... Read More about A multi-wavelength view of distinct accretion regimes in the pulsating ultraluminous X-ray source NGC 1313 X-2.

A full spectral-timing model to map the accretion flow in black hole binaries: the low/hard state of MAXI J1820+070 (2022)
Journal Article

The nature and geometry of the accretion flow in the low/hard state of black hole binaries is currently controversial. While most properties are generally explained in the truncated disc/hot inner flow model, the detection of a broad residual around... Read More about A full spectral-timing model to map the accretion flow in black hole binaries: the low/hard state of MAXI J1820+070.

The Voyage of Metals in the Universe from Cosmological to Planetary Scales: the need for a Very High-Resolution, High Throughput Soft X-ray Spectrometer (2021)
Journal Article

Metals form an essential part of the Universe at all scales. Without metals we would not exist, and the Universe would look completely different. Metals are primarily produced via nuclear processes in stars, and spread out through winds or explosions... Read More about The Voyage of Metals in the Universe from Cosmological to Planetary Scales: the need for a Very High-Resolution, High Throughput Soft X-ray Spectrometer.

Space Telescope and Optical Reverberation Mapping Project. IX. Velocity–Delay Maps for Broad Emission Lines in NGC 5548 (2021)
Journal Article

In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM campaign by recovering velocity–delay maps for the prominent broad emission lines (Lyα, C iv, He ii, and Hβ) in the spectrum of NGC 5548. These are the most... Read More about Space Telescope and Optical Reverberation Mapping Project. IX. Velocity–Delay Maps for Broad Emission Lines in NGC 5548.

Estimating the size of X-ray lamppost coronae in active galactic nuclei (2020)
Journal Article

Aims. We report estimates of the X-ray coronal size of active galactic nuclei in the lamppost geometry. In this commonly adopted scenario, the corona is assumed for simplicity to be a point-like X-ray source located on the axis of the accretion disc.... Read More about Estimating the size of X-ray lamppost coronae in active galactic nuclei.

Re-observing the NLS1 galaxy RE J1034+396 – II. New insights on the soft X-ray excess, QPO, and the analogy with GRS 1915+105 (2020)
Journal Article

The active galactic nucleus (AGN) RE J1034+396 displays the most significant X-ray quasi-periodic oscillation (QPO) detected so far. We perform a detailed spectral-timing analysis of our recent simultaneous XMM–Newton, NuSTAR, and Swift observations.... Read More about Re-observing the NLS1 galaxy RE J1034+396 – II. New insights on the soft X-ray excess, QPO, and the analogy with GRS 1915+105.

Space Telescope and Optical Reverberation Mapping Project. XII. Broad-line Region Modeling of NGC 5548 (2020)
Journal Article

We present geometric and dynamical modeling of the broad line region (BLR) for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The data set includes photometric and spectroscopic monitoring in the optical and ultravio... Read More about Space Telescope and Optical Reverberation Mapping Project. XII. Broad-line Region Modeling of NGC 5548.

Geometry of the X-ray source 1H 0707–495 (2020)
Journal Article

Aims. We investigate the constraints on the size and location of the X-ray source in 1H 0707–495 determined from the shape of the relativistically smeared reflection from the accretion disc. Methods. We developed a new code to model an extended X-ray... Read More about Geometry of the X-ray source 1H 0707–495.

Looking for the underlying cause of black hole X-ray variability in GRMHD simulations (2020)
Journal Article

Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like a lognormal distribution of... Read More about Looking for the underlying cause of black hole X-ray variability in GRMHD simulations.

Reobserving the NLS1 galaxy RE J1034+396 – I. The long-term, recurrent X-ray QPO with a high significance (2020)
Journal Article

RE J1034+396 is a narrow-line Seyfert 1 galaxy (NLS1) in which the first significant X-ray quasi-periodic oscillation (QPO) in an active galactic nucleus (AGN) was observed in 2007. We report the detection of this QPO in a recent XMM–Newton observati... Read More about Reobserving the NLS1 galaxy RE J1034+396 – I. The long-term, recurrent X-ray QPO with a high significance.

Thermally-Driven Disc Winds as a Mechanism for X-ray Irradiation Heating in Black Hole X-ray Binaries: The Case Study of GX339−4 (2020)
Journal Article

X-ray irradiation heating of accretion discs in black hole X-ray binaries (BHXBs) plays a key role in regulating their outburst cycles. However, despite decades of theoretical and observational efforts, the physical mechanism(s) responsible for irrad... Read More about Thermally-Driven Disc Winds as a Mechanism for X-ray Irradiation Heating in Black Hole X-ray Binaries: The Case Study of GX339−4.

State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations (2020)
Journal Article

The great power offered by photoionization models of Active Galactic Nuclei (AGN) emission line regions has long been mitigated by the fact that very little is known about the spectral energy distribution (SED) between the Lyman limit, where interven... Read More about State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations.

Qwind code release. A non-hydrodynamical approach to modelling line-driven winds in active galactic nuclei (2020)
Journal Article

UV line driven winds may be an important part of the AGN feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the approach pioneered by Risaliti & Elvis, calculating... Read More about Qwind code release. A non-hydrodynamical approach to modelling line-driven winds in active galactic nuclei.

Line-driven disc wind in near-Eddington active galactic nuclei: decrease of mass accretion rate due to powerful outflow (2020)
Journal Article

Based on recent X-ray observations, ultra-fast outflows from supermassive black holes are expected to have enough energy to dramatically affect their host galaxy but their launch and acceleration mechanisms are not well understood. We perform two-dim... Read More about Line-driven disc wind in near-Eddington active galactic nuclei: decrease of mass accretion rate due to powerful outflow.

The thermal-radiative wind in low-mass X-ray binary H1743−322 – II. Iron line predictions from Monte Carlo radiation transfer (2020)
Journal Article

We show the best current simulations of the absorption and emission features predicted from thermal-radiative winds produced from X-ray illumination of the outer accretion disc in binary systems. We use the density and velocity structure derived from... Read More about The thermal-radiative wind in low-mass X-ray binary H1743−322 – II. Iron line predictions from Monte Carlo radiation transfer.

The impact of thermal winds on the outburst lightcurves of black hole X-ray binaries (2019)
Journal Article

Context. The observed signatures of winds from X-ray binaries are broadly consistent with thermal winds, which are driven by X-ray irradiation of the outer accretion disc. Thermal winds produce mass outflow rates that can exceed the accretion rate in... Read More about The impact of thermal winds on the outburst lightcurves of black hole X-ray binaries.

Discarding the disc in a changing-state AGN: the UV/X-ray relation in NGC 4151 (2019)
Journal Article

Recent monitoring campaigns designed to map the accretion regime in AGN show major discrepancies with models where the optical/ultraviolet (UV) is produced by X-ray-illuminated, optically thick disc material within a few hundred gravitational radii.... Read More about Discarding the disc in a changing-state AGN: the UV/X-ray relation in NGC 4151.

Application of the Thermal Wind Model to Absorption Features in the Black Hole X-ray Binary H 1743$-$322 (2019)
Journal Article

High inclination black hole X-ray binaries exhibit blueshifted ionized absorption lines from disk winds, whose launching mechanism is still in debate. The lines are predominantly observed in the high/soft state and disappear in the low/hard state, an... Read More about Application of the Thermal Wind Model to Absorption Features in the Black Hole X-ray Binary H 1743$-$322.

The thermal-radiative wind in low mass X-ray binary H~1743-322; Radiation hydrodynamic simulations (2019)
Journal Article

Blueshifted absorption lines are seen in high inclination black hole binary systems in their disc dominated states, showing these power an equatorial disc wind. While some contribution from magnetic winds remain a possibility, thermal and thermal-rad... Read More about The thermal-radiative wind in low mass X-ray binary H~1743-322; Radiation hydrodynamic simulations.

Modelling the spectral energy distribution of super-Eddington quasars (2019)
Journal Article

We develop a broadband spectral model, AGNSLIM, to describe super-Eddington black hole accretion disc spectra. This is based on the slim disc emissivity, where radial advection keeps the surface luminosity at the local Eddington limit, resulting in L... Read More about Modelling the spectral energy distribution of super-Eddington quasars.

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413 (2019)
Journal Article

We present a multi-frequency study of PKS J1222+0413 (4C +04.42), currently the highest redshift γ-ray emitting narrow-line Seyfert 1 (γ-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished datasets: X-ray da... Read More about The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413.

CLOUDY view of the warm corona (2019)
Journal Article

Bright active galaxies show a range of properties, but many of these properties are correlated, which has led to the concept of the quasar main sequence. We test whether our current understanding of the quasar structure allows the pattern observed in... Read More about CLOUDY view of the warm corona.

Reverberation Reveals the Truncated Disc in the Hard State of GX 339-4 (2019)
Journal Article

The nature and geometry of the hard state in black hole binaries is controversial. The broadband continuum spectrum and fast variability properties can be explained in a model where the inner disc evaporates into a geometrically thick, hot flow. Howe... Read More about Reverberation Reveals the Truncated Disc in the Hard State of GX 339-4.

A deep X-ray view of the bare AGN Ark 120. V. Spin determination from disc-Comptonisation efficiency method (2019)
Journal Article

Context. The spin of supermassive black holes (SMBH) in active galactic nuclei (AGN) can be determined from spectral signature(s) of relativistic reflection such as the X-ray iron Kα line profile, but this can be rather uncertain when the line of sig... Read More about A deep X-ray view of the bare AGN Ark 120. V. Spin determination from disc-Comptonisation efficiency method.

Rapid Black Hole Growth at the Dawn of the Universe: Super-Eddington Quasar at z=6.6 (2019)
Journal Article

We present the analysis of a new near-infrared (NIR) spectrum of a recently discovered z = 6.621 quasar PSO J006 + 39 in an attempt to explore the early growth of supermassive black holes (SMBHs). This NIR (rest-frame ultraviolet, UV) spectrum shows... Read More about Rapid Black Hole Growth at the Dawn of the Universe: Super-Eddington Quasar at z=6.6.

The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey (2019)
Journal Article

Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled ~200–350 times in 0.3–10 keV X-ray and six UV/optical bands. Uniform reduction and cross-correlation analysis of these data sets yields three main results:... Read More about The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey.

Thermally driven wind as the origin of warm absorbers in AGN (2019)
Journal Article

Warm absorbers are present in many Active Galactic Nuclei (AGN), seen as mildly ionised gas outflowing with velocities of a few hundred to a few thousand kilometres per second. These slow velocities imply a large launch radius, pointing to the broad... Read More about Thermally driven wind as the origin of warm absorbers in AGN.

Evolution of thermally driven disk wind in the black hole binary 4U 1630-47 observed with Suzaku and Nustar (2018)
Journal Article

We performed simultaneous observations with Suzaku and NuSTAR of the Galactic black hole binary 4U 1630−47 in the high/soft state (HSS) during the 2015 outburst. To compare our results with those observed in the HSS at lower luminosities, we re-analy... Read More about Evolution of thermally driven disk wind in the black hole binary 4U 1630-47 observed with Suzaku and Nustar.

X-ray reverberation lags of the Fe–K line due to AGN disc winds (2018)
Journal Article

Short X-ray reverberation lags are seen across a broad Fe–K energy band in more than 20 active galactic nuclei (AGNs). This broad iron line feature in the lag spectrum is most significant in super-Eddington sources such as Ark 564 (L/LEdd ∼ 1) and 1H... Read More about X-ray reverberation lags of the Fe–K line due to AGN disc winds.

Evolution of X-ray irradiation during the 1999–2000 outburst of the black hole binary XTE J1859 + 226 (2018)
Journal Article

X-ray irradiation in X-ray binaries is thought to control the behaviour at the outer disc, which is observable mainly at optical wavelengths. It is generally parametrized phenomenologically, but it can also be predicted from theoretical models of irr... Read More about Evolution of X-ray irradiation during the 1999–2000 outburst of the black hole binary XTE J1859 + 226.

A physical model for the spectral-timing properties of accreting black holes (2018)
Journal Article

We develop new techniques to deconvolve the radial structure of the X-ray emission region in the bright low/hard state of the black hole Cygnus X-1 using both spectral and timing data in the 3–35 keV range. The spectrum at these energies is dominated... Read More about A physical model for the spectral-timing properties of accreting black holes.

X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor (2018)
Journal Article

We report the results of intensive X-ray, UV, and optical monitoring of the Seyfert 1 galaxy NGC 4593 with Swift. There is no intrinsic flux-related spectral change in any variable component with small apparent variations being due to contamination b... Read More about X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor.

Explaining changing-look AGN with state transition triggered by rapid mass accretion rate drop (2018)
Journal Article

We model the broadband (optical/UV and X-ray) continuum spectrum of the “changing-look” active galactic nucleus (AGN) Mrk 1018 as it fades from Seyfert 1 to 1.9 in ∼8 years. The brightest spectrum, with Eddington ratio L/LEdd ∼ 0.08, has a typical ty... Read More about Explaining changing-look AGN with state transition triggered by rapid mass accretion rate drop.

A physical model of the broadband continuum of AGN and its implications for the UV/X relation and optical variability (2018)
Journal Article

We develop a new spectral model for the broad-band spectral energy distribution (SED) of active galactic nuclei (AGN). This includes an outer standard disc, an inner warm Comptonizing region to produce the soft X-ray excess and a hot corona. We tie t... Read More about A physical model of the broadband continuum of AGN and its implications for the UV/X relation and optical variability.

Breaking the spectral degeneracies in black hole binaries with fast timing data: the hard state of Cygnus X-1 (2018)
Journal Article

The spectra of black hole binaries in the low/hard state are complex, with evidence for multiple different Comptonization regions contributing to the hard X-rays in addition to a cool disc component. We show this explicitly for some of the best RXTE... Read More about Breaking the spectral degeneracies in black hole binaries with fast timing data: the hard state of Cygnus X-1.

X-ray short-time lags in the Fe-K energy band produced by scattering clouds in active galactic nuclei (2018)
Journal Article

X-rays illuminating the accretion disc in active galactic nuclei give rise to an iron K line and its associated reflection spectrum which are lagged behind the continuum variability by the light-travel time from the source to the disc. The measured l... Read More about X-ray short-time lags in the Fe-K energy band produced by scattering clouds in active galactic nuclei.

Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi* (2018)
Journal Article

The Hitomi Soft X-ray Spectrometer spectrum of the Perseus cluster, with ∼5 eV resolution in the 2–9 keV band, offers an unprecedented benchmark of the atomic modeling and database for hot collisional plasmas. It reveals both successes and challenges... Read More about Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi*.

Hitomi (ASTRO-H) X-ray Astronomy Satellite (2018)
Journal Article

The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E  > ... Read More about Hitomi (ASTRO-H) X-ray Astronomy Satellite.

Monte-Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries (2018)
Journal Article

Blue–shifted absorption lines from highly ionised iron are seen in some high inclination X-ray binary systems, indicating the presence of an equatorial disc wind. This launch mechanism is under debate, but thermal driving should be ubiquitous. X-ray... Read More about Monte-Carlo simulations of the detailed iron absorption line profiles from thermal winds in X-ray binaries.

Search for gravitational redshifted absorption lines in LMXB Serpens X-1 (2017)
Journal Article

The equation of state for ultradense matter can be tested from observations of the ratio of mass to radius of neutron stars. This could be measured precisely from the redshift of a narrow line produced on the surface. X-rays bursts have been intensiv... Read More about Search for gravitational redshifted absorption lines in LMXB Serpens X-1.

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342 (2017)
Journal Article

The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of γ-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum radio... Read More about The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342.

In search of a new era of UK X-ray astronomy (2017)
Journal Article

X-ray astronomy is our gateway to the hot universe. More than half of the baryons in the cosmos are too hot to be visible at shorter wavelengths. Studying the extreme environments of black hole and neutron star vicinities also requires X-ray data. Wi... Read More about In search of a new era of UK X-ray astronomy.

Evidence for higher black hole spin in radio-loud quasars (2017)
Journal Article

One of the major unsolved questions concerning the understanding of the active galactic nucleus population is the origin of the dichotomy between radio-quiet and radio-loud quasars. The most promising explanation is provided by the spin paradigm, whi... Read More about Evidence for higher black hole spin in radio-loud quasars.

What powers the most relativistic jets? – II. Flat-spectrum radio quasars (2017)
Journal Article

Flat Spectrum Radio Quasars (FSRQs) are the most powerful relativistic jets seen from supermassive black holes (BHs) accreting via a radiatively efficient thin disc. Their high energy emission is well modelled by highly relativistic electrons in the... Read More about What powers the most relativistic jets? – II. Flat-spectrum radio quasars.

Thermal winds in stellar mass black hole and neutron star binary systems (2017)
Journal Article

Black hole binaries show equatorial disc winds at high luminosities, which apparently disappear during the spectral transition to the low/hard state. This is also where the radio jet appears, motivating speculation that both wind and jet are driven b... Read More about Thermal winds in stellar mass black hole and neutron star binary systems.

Modelling the energy dependence of black hole binary flows (2017)
Journal Article

We build a full spectral-timing model for the low/hard state of black hole binaries assuming that the spectrum of the X-ray hot flow can be produced by two Comptonization zones. Slow fluctuations generated at the largest radii/softest spectral region... Read More about Modelling the energy dependence of black hole binary flows.

Determining the torus covering factors for a sample of type 1 AGN in the local Universe (2017)
Journal Article

In the unified scheme of active galactic nuclei, a dusty torus absorbs and then reprocesses a fraction of the intrinsic luminosity which is emitted at longer wavelengths. Thus, subject to radiative transfer corrections, the fraction of the sky covere... Read More about Determining the torus covering factors for a sample of type 1 AGN in the local Universe.

Super-Eddington QSO RX J0439.6-5311 – II. Multiwavelength constraints on the global structure of the accretion flow (2017)
Journal Article

We present a detailed multiwavelength study of an unobscured, highly super-Eddington Type-1 QSO RX J0439.6-5311. We combine the latest XMM–Newton observation with all archival data from infrared to hard X-rays. The optical spectrum is very similar to... Read More about Super-Eddington QSO RX J0439.6-5311 – II. Multiwavelength constraints on the global structure of the accretion flow.

Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing (2017)
Journal Article

Swift monitoring of NGC 4151 with an ~6 hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3–50 keV) and six in the ultraviolet (UV)/optical (1900–5500 Å). The three hardest X-ray... Read More about Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing.

The origin of the UV/optical lags in NGC 5548 (2017)
Journal Article

The new multiwavelength monitoring campaign on NGC 5548 shows clearly that the variability of the ultraviolet (UV)/optical light curves lags by progressively longer times at longer wavelengths, as expected from reprocessing off an optically thick dis... Read More about The origin of the UV/optical lags in NGC 5548.

Super-Eddington QSO RX J0439.6−5311 – I. Origin of the soft X-ray excess and structure of the inner accretion flow (2017)
Journal Article

We report the results from a recent 133 ks XMM–Newton observation of a highly super-Eddington narrow-line Type-1 quasi-stellar object RX J0439.6−5311. This source has one of the steepest active galactic nuclei hard X-ray slopes, in addition to a prom... Read More about Super-Eddington QSO RX J0439.6−5311 – I. Origin of the soft X-ray excess and structure of the inner accretion flow.

Revisiting the extremely fast disc wind in a gravitationally lensed quasar APM 08279+5255 (2017)
Journal Article

The gravitationally lensed quasar APM 08279+5255 has the fastest claimed wind from any active galactic nucleus, with velocities of 0.6–0.7c, requiring magnetic acceleration as special relativistic effects limit all radiatively driven winds to v < 0.3... Read More about Revisiting the extremely fast disc wind in a gravitationally lensed quasar APM 08279+5255.

Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster (2017)
Journal Article

High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E=3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Pe... Read More about Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster.

Black hole spin of Cygnus X-1 determined from the softest state ever observed (2017)
Journal Article

We show the softest ever spectrum from Cyg X-1, detected in 2013 with Suzaku. This has the weakest high-energy Compton tail ever seen from this object, so should give the cleanest view of the underlying disk spectrum, and hence the best determination... Read More about Black hole spin of Cygnus X-1 determined from the softest state ever observed.

Crossing the Eddington Limit: Examining Disk Spectra at High Accretion Rates (2017)
Journal Article

The faintest ultraluminous X-ray sources (ULXs), those with 0.3-10 keV luminosities 1 < L_X/10^39 < 3 erg s^-1, tend to have X-ray spectra that are disk-like but broader than expected for thin accretion disks. These `broadened disk' spectra are thoug... Read More about Crossing the Eddington Limit: Examining Disk Spectra at High Accretion Rates.

Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy (2016)
Journal Article

We continue our study of the spectral energy distributions (SEDs) of 11 active galactic nuclei (AGN) at 1.5 < z < 2.2, with optical–near-infrared (NIR) spectra, X-ray data and mid-IR photometry. In a previous paper, we presented the observations and... Read More about Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy.

On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342 (2016)
Journal Article

Narrow-line Seyfert 1 galaxies have been identified by the Fermi Gamma-Ray Space Telescope as a rare class of γ-ray emitting active galactic nuclei. The lowest redshift candidate among them is the source 1H 0323+342. Here we present quasi-simultaneou... Read More about On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342.

Testing the completeness of the SDSS colour selection for ultramassive, slowly spinning black holes (2016)
Journal Article

We investigate the sensitivity of the colour-based quasar selection algorithm of the Sloan Digital Sky Survey (SDSS) to several key physical parameters of supermassive black holes (SMBHs), focusing on BH spin (a*) at the high BH-mass regime (MBH ≥ 10... Read More about Testing the completeness of the SDSS colour selection for ultramassive, slowly spinning black holes.

The quiescent intracluster medium in the core of the Perseus cluster (2016)
Journal Article

A disc wind interpretation of the strong Fe K$\alpha$ features in 1H 0707-495 (2016)
Journal Article

1H 0707−495 is the most convincing example of a supermassive black hole with an X-ray spectrum being dominated by extremely smeared, relativistic reflection, with the additional requirement of strongly supersolar iron abundance. However, here we show... Read More about A disc wind interpretation of the strong Fe K$\alpha$ features in 1H 0707-495.

An optically thick disk wind in GRO J1655-40? (2016)
Journal Article

We revisited the unusual wind in GRO J1655−40, detected with Chandra in 2005 April, using long-term Rossi X-ray Timing Explorer X-ray data and simultaneous optical/near-infrared photometric data. This wind is the most convincing case for magnetic dri... Read More about An optically thick disk wind in GRO J1655-40?.

The X-ray spectral evolution of the ultraluminous X-ray source Holmberg IX X-1 (2016)
Journal Article

We present a new analysis of X-ray spectra of the archetypal ultraluminous X-ray source (ULX) Holmberg IX X-1 obtained by the Swift, XMM–Newton and NuSTAR observatories. This ULX is a persistent source, with a typical luminosity of ∼1040 erg s−1, tha... Read More about The X-ray spectral evolution of the ultraluminous X-ray source Holmberg IX X-1.

A quasi-periodic modulation of the iron line centroid energy in the black hole binary H1743-322 (2016)
Journal Article

Accreting stellar-mass black holes often show a ‘Type-C’ quasi-periodic oscillation (QPO) in their X-ray flux and an iron emission line in their X-ray spectrum. The iron line is generated through continuum photons reflecting off the accretion disc, a... Read More about A quasi-periodic modulation of the iron line centroid energy in the black hole binary H1743-322.

The mass and spin of the extreme Narrow Line Seyfert 1 Galaxy 1H 0707-495 and its implications for the trigger for relativistic jets (2016)
Journal Article

Relativistic reflection models of the X-ray spectrum of the ‘complex’ Narrow Line Seyfert 1 (NLS1) 1H 0707−495 require a high-spin, moderate-inclination, low-mass black hole. With these parameters fixed, the observed optical/UV emission directly dete... Read More about The mass and spin of the extreme Narrow Line Seyfert 1 Galaxy 1H 0707-495 and its implications for the trigger for relativistic jets.

Minimum X-ray source size of the on-axis corona in AGN. (2016)
Journal Article

Tracking the energetics of the non-thermal disc–corona–jet in the very high state GX 339 − 4 (2016)
Journal Article

The dramatic hard–soft spectral transition in black hole binaries is important as it is associated with the collapse of the jet and with the strongest low-frequency quasi-periodic oscillations (QPOs). These transition spectra (intermediate and very h... Read More about Tracking the energetics of the non-thermal disc–corona–jet in the very high state GX 339 − 4.

Revealing the nature of the QPO and its harmonic in GX 339-4 using frequency-resolved spectroscopy (2016)
Journal Article

We use frequency-resolved spectroscopy to examine the energy spectra of the prominent low-frequency quasi-periodic oscillation (QPO) and its harmonic in GX 339-4. We track the evolution of these spectra as the source makes a transition from a bright... Read More about Revealing the nature of the QPO and its harmonic in GX 339-4 using frequency-resolved spectroscopy.

Limits on pair production and multizone Comptonization: the broad-band X/γ-ray spectrum of XTE J1550–564 revisited (2016)
Journal Article

At high luminosities black hole binaries show spectra with a strong disc component accompanied by an equally strong tail where at least some of the electrons are non-thermal. We reanalyse the simultaneous ASCA–RXTE–OSSE data from the 1998 outburst of... Read More about Limits on pair production and multizone Comptonization: the broad-band X/γ-ray spectrum of XTE J1550–564 revisited.

A variable ULX and possible IMBH candidate in M51a (2016)
Journal Article

Ultraluminous X-ray source (ULX)-7, in the northern spiral arm of M51, demonstrates unusual behaviour for an ULX, with a hard X-ray spectrum but very high short-term variability. This suggests that it is not in a typical ultraluminous state. We analy... Read More about A variable ULX and possible IMBH candidate in M51a.

Strong constraints on a super-Eddington accretion flow: XMM–Newton observations of an intermediate-mass black hole (2015)
Journal Article

RX J1140.1+0307 is a Narrow Line Seyfert 1 (NLS1) with one of the lowest black hole masses known in an AGN (M ≤ 106 M⊙). We show results from two new XMM–Newton observations, exhibiting soft 2–10 keV spectra, a strong excess at lower energies, and fa... Read More about Strong constraints on a super-Eddington accretion flow: XMM–Newton observations of an intermediate-mass black hole.

X-ray polarimetry with the Polarization Spectroscopic Telescope Array (PolSTAR) (2015)
Journal Article

This paper describes the Polarization Spectroscopic Telescope Array (PolSTAR), a mission proposed to NASA’s 2014 Small Explorer (SMEX) announcement of opportunity. PolSTAR measures the linear polarization of 3–50 keV (requirement; goal: 2.5–70 keV) X... Read More about X-ray polarimetry with the Polarization Spectroscopic Telescope Array (PolSTAR).

The Accreting Black Hole Swift J1753.5-0127 from Radio to Hard X-Ray (2015)
Journal Article

We report on multiwavelength measurements of the accreting black hole Swift J1753.5–0127 in the hard state at low luminosity (L ~ 2.7 × 1036 erg s−1 assuming a distance of d = 3 kpc) in 2014 April. The radio emission is optically thick synchrotron, p... Read More about The Accreting Black Hole Swift J1753.5-0127 from Radio to Hard X-Ray.

Reaching the peak of the quasar spectral energy distribution - I. Observations and models (2015)
Journal Article

We perform a spectral analysis of a sample of 11 medium redshift (1.5 ≲ z ≲ 2.2) quasars. Our sample all have optical spectra from the SDSS, infrared spectra from GNIRS and TripleSpec, and X-ray spectra from XMM–Newton. We first analyse the Balmer br... Read More about Reaching the peak of the quasar spectral energy distribution - I. Observations and models.

Complex narrow-line Seyfert 1s: high spin or high inclination? (2015)
Journal Article

Complex narrow-line Seyfert 1s (NLS1s), such as 1H 0707−495, differ from simple NLS1s like PG 1244+026 by showing stronger broad spectral features at Fe K and larger amplitude flux variability. These are correlated: the strongest Fe K features are se... Read More about Complex narrow-line Seyfert 1s: high spin or high inclination?.

Erratum: “Suzaku Observation of the Black Hole Binary 4U 1630-47 in the Very High State” (2014, ApJ, 790, 20) (2014)
Journal Article

The origin of ultrafast outflows in AGN: Monte Carlo simulations of the wind in PDS 456 (2014)
Journal Article

Ultrafast outflows (UFOs) are seen in many AGN, giving a possible mode for AGN feedback on to the host galaxy. However, the mechanism(s) for the launch and acceleration of these outflows are currently unknown, with UV line driving apparently strongly... Read More about The origin of ultrafast outflows in AGN: Monte Carlo simulations of the wind in PDS 456.

Irradiated, colour-temperature-corrected accretion discs in ultraluminous X-ray sources (2014)
Journal Article

Although attempts have been made to constrain the stellar types of optical counterparts to ultraluminous X-ray sources (ULXs), the detection of optical variability instead suggests that they may be dominated by reprocessed emission from X-rays which... Read More about Irradiated, colour-temperature-corrected accretion discs in ultraluminous X-ray sources.

SUZAKU Observation of the Black Hole Binary 4U 1630-47 in the Very High State (2014)
Journal Article

We report the results from an X-ray and near-infrared observation of the Galactic black hole binary 4U 1630-47 in the very high state (VHS), performed with Suzaku and the Infrared Survey Facility around the peak of the 2012 September-October outburst... Read More about SUZAKU Observation of the Black Hole Binary 4U 1630-47 in the Very High State.

Spectral and Timing Properties of the Black Hole X-Ray Binary H1743-322 in the Low/Hard State Studied with Suzaku (2014)
Journal Article

We report on the results from Suzaku observations of the Galactic black hole X-ray binary H1743–322 in the low/hard state during its outburst in 2012 October. We appropriately take into account the effects of dust scattering to accurately analyze the... Read More about Spectral and Timing Properties of the Black Hole X-Ray Binary H1743-322 in the Low/Hard State Studied with Suzaku.

A physical model for the X-ray time lags of narrow-line Seyfert type 1 active galactic nuclei (2014)
Journal Article

We study the origin of the soft X-ray excess seen in the ‘simple’ narrow-line Seyfert 1 galaxy PG1244+026 using all available spectral-timing information. This object shows the now ubiquitous switch between soft leading the hard band on long time-sca... Read More about A physical model for the X-ray time lags of narrow-line Seyfert type 1 active galactic nuclei.

A compact, metal-rich, kpc-scale outflow in FBQS J0209-0438: detailed diagnostics from HST/COS extreme UV observations (2014)
Journal Article

We present HST/COS observations of highly ionized absorption lines associated with a radio-loud quasar (QSO) at z = 1.1319. The absorption system has multiple velocity components, with an overall width of ≈600 km s−1, tracing gas that is largely outf... Read More about A compact, metal-rich, kpc-scale outflow in FBQS J0209-0438: detailed diagnostics from HST/COS extreme UV observations.

X-ray time delays in the narrow line Seyfert 1 galaxy PG 1244+026 (2014)
Journal Article

We analyse the X-ray time-lags in the narrow line Seyfert 1 (NLS1) galaxy PG 1244+026 (MBH ∼ 107 M⊙, L/LEdd ∼ 1). The time delay between the soft (0.3–0.7 keV) and harder (1.2–4.0 keV) variations shows the well-established switch from hard lags at lo... Read More about X-ray time delays in the narrow line Seyfert 1 galaxy PG 1244+026.

The Accretion Disk and Ionized Absorber of the 9.7 hr Dipping Black Hole Binary MAXI J1305-704 (2013)
Journal Article

An imperfect double: probing the physical origin of the low-frequency quasi-periodic oscillation and its harmonic in black hole binaries (2013)
Journal Article

We extract the spectra of the strong low-frequency quasi-periodic oscillation (QPO) and its harmonic during the rising phase of an outburst in the black hole binary XTE J1550-564. We compare these frequency-resolved spectra to the time-averaged spect... Read More about An imperfect double: probing the physical origin of the low-frequency quasi-periodic oscillation and its harmonic in black hole binaries.

The story of Seyfert galaxy RE J2248-511: from intriguingly ultrasoft to unremarkably average (2013)
Journal Article

RE J2248−511 is one of only 14 non-blazar active galactic nuclei (AGN) detected in the far-ultraviolet (FUV) by the ROSAT Wide Field Camera implying a large ultrasoft X-ray flux. This soft X-ray excess is strongly variable on year time-scales, a comm... Read More about The story of Seyfert galaxy RE J2248-511: from intriguingly ultrasoft to unremarkably average.

What powers the most relativistic jets? – I. BL Lacs (2013)
Journal Article

The dramatic relativistic jets pointing directly at us in BL Lacertae (BL Lac) objects can be well modelled by bulk motion beaming of synchrotron self-Compton emission powered by a low Eddington fraction accretion flow. Nearly 500 of these active gal... Read More about What powers the most relativistic jets? – I. BL Lacs.

The soft component and the iron line as signatures of the disc inner radius in Galactic black hole binaries (2013)
Journal Article

The inner radius of the accretion disc around a black hole in the low/hard state can be measured in one of two ways. First, via the extent of broadening of the iron emission line, and secondly, from the luminosity and temperature of the weak soft com... Read More about The soft component and the iron line as signatures of the disc inner radius in Galactic black hole binaries.

Evidence for a Cool Disk and Inhomogeneous Coronae from Wide-Band Temporal Spectroscopy of Cygnus X-1 with Suzaku (2013)
Journal Article

Jets and the accretion flow in low-luminosity black holes (2013)
Journal Article

The X-ray spectra of black hole binaries (BHB) in the low/hard state (LHS) first harden as the flux decreases, then soften. This change in behaviour has been variously attributed to either the X-rays switching from being produced in the flow to being... Read More about Jets and the accretion flow in low-luminosity black holes.

A new way to measure supermassive black hole spin in accretion disc-dominated Active Galaxies (2013)
Journal Article

We show that disc continuum fitting can be used to constrain black hole spin in a subclass of narrow-line Seyfert 1 (NLS1) active galactic nuclei as their low mass and high mass accretion rate means that the disc peaks at energies just below the soft... Read More about A new way to measure supermassive black hole spin in accretion disc-dominated Active Galaxies.

The effect of advection at luminosities close to Eddington: The ULX in M 31 (2013)
Journal Article

Highly Ionized Fe-K Absorption Line from Cygnus X-1 in the High/Soft State Observed with Suzaku (2013)
Journal Article

We present observations of a transient He-like Fe Kα absorption line in Suzaku observations of the black hole binary Cygnus X-1 on 2011 October 5 near superior conjunction during the high/soft state, which enable us to map the full evolution from the... Read More about Highly Ionized Fe-K Absorption Line from Cygnus X-1 in the High/Soft State Observed with Suzaku.

Fast variability as a probe of the smallest regions around accreting black holes (2013)
Journal Article

We extract the spectra of the fastest variability (above 10 Hz) from the black hole XTE J1550−564 during a transition from hard to soft state on the rise to outburst. We confirm previous results that the rapid variability contains no significant disc... Read More about Fast variability as a probe of the smallest regions around accreting black holes.

Bright radio emission from an ultraluminous stellar-mass microquasar in M 31 (2013)
Journal Article

A subset of ultraluminous X-ray sources (those with luminosities of less than 1040 erg s−1; ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ~5–20 , probably by means of an accretion disk2, 3. The X-ray and ra... Read More about Bright radio emission from an ultraluminous stellar-mass microquasar in M 31.

The effect of frame dragging on the iron Kα line in X-ray binaries (2012)
Journal Article

The clear characteristic time-scale picked out by the low-frequency quasi-periodic oscillations (QPOs) seen in many black hole and neutron star binaries has the potential to provide a very powerful diagnostic of the inner regions of the accretion flo... Read More about The effect of frame dragging on the iron Kα line in X-ray binaries.

The Large Observatory for X-ray Timing (LOFT) (2012)
Journal Article

A combined optical and X-ray study of unobscured type 1 active galactic nuclei - III. Broad-band SED properties (2012)
Journal Article

In this third paper in a series of three, we present a detailed study of the broad-band spectral energy distribution (SED) of active galactic nuclei (AGNs) based on a nearby unobscured type 1 AGN sample. We perform a systematic cross-correlation stud... Read More about A combined optical and X-ray study of unobscured type 1 active galactic nuclei - III. Broad-band SED properties.

The Truncated Disk from Suzaku Data of GX 339-4 in the Extreme Very High State (2012)
Journal Article

A combined optical and X-ray study of unobscured type 1 active galactic nuclei - II. Relation between X-ray emission and optical spectra (2012)
Journal Article

In this second paper in a series of three, we study the properties of the various emission features and underlying continuum in the optical spectra of type 1 active galactic nuclei (AGNs) by using the unobscured hard X-ray emission as a diagnostic. W... Read More about A combined optical and X-ray study of unobscured type 1 active galactic nuclei - II. Relation between X-ray emission and optical spectra.

The missing link: a low mass X-ray binary in M31 seen as an ultraluminous X-ray source (2012)
Journal Article

A new, transient ultraluminous X-ray source (ULX) was recently discovered by Chandra in M31 with a luminosity at ∼5 × 1039 erg s−1. Here we analyse a series of five subsequent XMM–Newton observations. These show a steady decline in X-ray luminosity o... Read More about The missing link: a low mass X-ray binary in M31 seen as an ultraluminous X-ray source.

Intrinsic disc emission and the soft X-ray excess in active galactic nuclei (2012)
Journal Article

Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in... Read More about Intrinsic disc emission and the soft X-ray excess in active galactic nuclei.

A combined optical and X-ray study of unobscured type 1 active galactic nuclei - I. Optical spectra and spectral energy distribution modelling (2012)
Journal Article

We present modelling and interpretation of the continuum and emission lines for a sample of 51 unobscured type 1 active galactic nuclei (AGNs). All of these AGNs have high-quality spectra from both XMM–Newton and the Sloan Digital Sky Survey. We exte... Read More about A combined optical and X-ray study of unobscured type 1 active galactic nuclei - I. Optical spectra and spectral energy distribution modelling.

Spatial variability of initial $^230$Th/ $^232$Th in modern Porites from the inshore region of the Great Barrier Reef (2012)
Journal Article

The evolution of active galactic nuclei across cosmic time : what is downsizing? (2012)
Journal Article

We use a coupled model of the formation and evolution of galaxies and black holes (BHs) to study the evolution of active galactic nuclei (AGNs) in a cold dark matter universe. The model is embedded in the galaxy formation code GALFORM and predicts th... Read More about The evolution of active galactic nuclei across cosmic time : what is downsizing?.

Modelling variability in black hole binaries: linking simulations to observations (2012)
Journal Article

Black hole accretion flows show rapid X-ray variability. The power spectral density (PSD) of this is typically fit by a phenomenological model of multiple Lorentzians for both the broad-band noise and quasi-periodic oscillations (QPOs). Our previous... Read More about Modelling variability in black hole binaries: linking simulations to observations.

Observational Constraints on Strong Gravity (2011)
Journal Article

Spectral and Timing Studies of Cyg X-1 in the Low/Hard State with Suzaku (2011)
Journal Article

Evidence for a change in the X-ray radiation mechanism in the hard state of Galactic black holes (2011)
Journal Article

Searching for the trigger of the active galactic nucleus quasi-periodic oscillation: 8 years of RE J1034+396 (2011)
Journal Article

Modelling the high-mass accretion rate spectra of GX 339-4: black hole spin from reflection? (2011)
Journal Article

A physical model for the continuum variability and quasi-periodic oscillation in accreting black holes (2011)
Journal Article

A strong and broad Fe line in the XMM-Newton spectrum of the new X-ray transient and black hole candidate XTE J1652-453 (2011)
Journal Article

The Effect of Coronal Radiation on a Residual Inner Disk in the Low/Hard Spectral State of Black Hole X-ray Binary Systems (2011)
Journal Article

Thermal conduction between a cool accretion disk and a hot inner corona can result in either evaporation of the disk or condensation of the hot corona. At low mass accretion rates, evaporation dominates and can completely remove the inner disk. At hi... Read More about The Effect of Coronal Radiation on a Residual Inner Disk in the Low/Hard Spectral State of Black Hole X-ray Binary Systems.

A re-analysis of the iron line in the XMM-Newton data from the low/hard state in GX339-4 (2010)
Journal Article

Limits on spin determination from disc spectral fitting in GX 339-4 (2010)
Journal Article

Suzaku wide-band observations of black-hole binaries and AGNs: continuum and Fe-K lines (2010)
Journal Article

A physical interpretation of the variability power spectral components in accreting neutron stars (2010)
Journal Article

We propose a physical framework for interpreting the characteristic frequencies seen in the broad-band power spectra from black hole and neutron star binaries. We use the truncated disc/hot inner flow geometry, and assume that the hot flow is generic... Read More about A physical interpretation of the variability power spectral components in accreting neutron stars.

Quasi-periodic oscillations under wavelet microscope: the application of Matching Pursuit algorithm (2010)
Journal Article

Testing Accretion Disk Structure with Suzaku Data of LMC X-3 (2010)
Journal Article

Suzaku Observation of GRS 1915+105: Evolution of Accretion Disk Structure during Limit-cycle Oscillation (2010)
Journal Article

An additional soft X-ray component in the dim low/hard state of black hole binaries (2010)
Journal Article

X-ray spectral variability in the ultraluminous X-ray source Holmberg IX X-1 (2010)
Journal Article

We use XMM–Newton and Swift data to study a spectral variability in the ultraluminous X-ray source (ULX), Holmberg IX X−1. The source luminosity varies by a factor of 3–4, giving rise to corresponding spectral changes which are significant, but subtl... Read More about X-ray spectral variability in the ultraluminous X-ray source Holmberg IX X-1.

The X-ray binary analogy to the first AGN quasi-periodic oscillation (2010)
Journal Article

The ultraluminous state (2009)
Journal Article

We revisit the question of the nature of ultraluminous X-ray sources (ULXs) through a detailed investigation of their spectral shape, using the highest quality X-ray data available in the XMM–Newton public archives (≳10 000 counts in their EPIC spect... Read More about The ultraluminous state.

Low-frequency quasi-periodic oscillations spectra and Lense-Thirring precession. (2009)
Journal Article

RE J1034+396: the origin of the soft X-ray excess and quasi-periodic oscillation (2009)
Journal Article

The Impact of Accretion Disk Winds on the X-Ray Spectra of Active Galactic Nuclei. II. Xscort + Hydrodynamic Simulations (2009)
Journal Article

Reprocessing of X-rays in the outer accretion disc of the black hole binary XTE J1817-330 (2009)
Journal Article

A periodicity of ~1 hour in X-ray emission from the active galaxy RE J1034+396 (2008)
Journal Article

X-ray irradiation in XTE J1817-330 and the inner radius of the truncated disc in the hard state (2008)
Journal Article

Angular Momentum Transport in Accretion Disks and Its Implications for Spin Estimates in Black Hole Binaries (2008)
Journal Article

Suzaku Results on Cygnus X-1 in the Low/Hard State (2008)
Journal Article

A Deep 0.3-10 keV Spectrum of the H$_2$O Maser Galaxy IC 2560 (2008)
Journal Article

Funnel wall jets and the nature of the soft X-ray excess (2008)
Journal Article

On why the iron K-shell absorption in AGN is not a signature of the local warm/hot intergalactic medium (2008)
Journal Article

High-energy X-ray spectra of Seyferts and Unification schemes for active galactic nuclei (2008)
Journal Article

Suzaku Wide-Band X-Ray Spectroscopy of the Seyfert2 AGN in NGC 4945 (2008)
Journal Article

Modelling the behaviour of accretion flows in x-ray binaries (2007)
Journal Article

We review how the recent increase in X-ray and radio data from black hole and neutron star binaries can be merged together with theoretical advances to give a coherent picture of the physics of the accretion flow in strong gravity. Both long term X-r... Read More about Modelling the behaviour of accretion flows in x-ray binaries.

Analysing the atolls: X-ray spectral transitions of accreting neutron stars. (2007)
Journal Article

We systematically analyse all the available X-ray spectra of disc accreting neutron stars (atolls and millisecond pulsars) from the RXTE data base. We show that while all these have similar spectral evolution as a function of mass accretion rate, the... Read More about Analysing the atolls: X-ray spectral transitions of accreting neutron stars..

Can the soft excess in AGN originate from disc reflection? (2007)
Journal Article

Suzaku Observation of Two Ultraluminous X-Ray Sources in NGC 1313 (2007)
Journal Article

What is the origin of the soft excess in active galactic nuclei? (2007)
Journal Article

We investigate the nature of the soft excess below 1 keV observed in active galactic nuclei. We use the XMM–Newton data of the low-redshift, optically bright quasar, PG 1211+143, and we compare it with the narrow-line Seyfert 1 galaxy, 1H 0707−495, w... Read More about What is the origin of the soft excess in active galactic nuclei?.

Suzaku Discovery of Iron Absorption Lines in Outburst Spectra of the X-Ray Transient 4U 1630-472 (2007)
Journal Article

The iron K feature in narrow line Seyfert 1 galaxies: evidence for a P Cygni profile? (2007)
Journal Article

Black hole spin in GRS 1915+105. (2006)
Journal Article

Microquasars are galactic black hole binary systems with radio jets which can sometimes be spatially resolved to show superluminal motion. The first and best known of this class of objects is GRS 1915+105, the brightest accreting source in our Galaxy... Read More about Black hole spin in GRS 1915+105..

Disc-corona energetics in the very high state of Galactic black holes (2006)
Journal Article

Failed disc winds: a physical origin for the soft X-ray excess? (2006)
Journal Article

Energy-dependent variability and the origin of the soft X-ray excess in active galactic nuclei (2006)
Journal Article

Testing Accretion Disk Theory in Black Hole X-Ray Binaries (2006)
Journal Article

Truncated disc versus extremely broad iron line in XTE J1650-500 (2006)
Journal Article

There is growing evidence from both spectral and timing properties that there is a truncated inner accretion disc in low mass accretion rate Galactic black hole systems. The detection of extremely smeared relativistic iron lines in some of these syst... Read More about Truncated disc versus extremely broad iron line in XTE J1650-500.

Extreme gravitational lensing near rotating black holes (2005)
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Observing braneworld black holes (2004)
Journal Article

Iron line profiles in strong gravity (2004)
Journal Article

Spectral Transitions in X-Ray Binaries (2004)
Journal Article

Modelling the Broad-Band Power Density Spectra of AGN to Include Relativistic Effects in Highly Inclined Systems (2004)
Journal Article

Accurate Modelling of Relativistic Iron Lines from Accretion Discs (2004)
Journal Article

GRS 1915+105: the brightest Galactic black hole (2004)
Journal Article

Understanding of X-Ray Spectra of Black Hole Binaries and Its Application to ULXs (2004)
Journal Article

XMM-Newton observations of 3C 273 (2004)
Journal Article

The very high state accretion disc structure from the Galactic black hole transient XTE J1550 - 564 (2004)
Journal Article

The 1998 outburst of the bright Galactic black hole binary system XTE J1550 - 564 was used to constrain the accretion disc structure in the strongly Comptonized very high state spectra. These data show that the disc emission is not easily compatible... Read More about The very high state accretion disc structure from the Galactic black hole transient XTE J1550 - 564.

Is the soft excess in active galactic nuclei real? (2004)
Journal Article

We systematically analyse all publicly available XMM–Newton spectra of radio-quiet PG quasars. The soft X-ray excess in these objects is well modelled by an additional, cool, Compton scattering region. However, the remarkably constant temperature der... Read More about Is the soft excess in active galactic nuclei real?.

Black hole accretion discs: reality confronts theory (2004)
Journal Article

Disc spectra from highly luminous black hole binaries are observed to be rather simple, despite theoretical predictions to the contrary. We collate the disc-dominated spectra from multiple observations of 10 separate sources and show that they are co... Read More about Black hole accretion discs: reality confronts theory.

Xmm-Newton Monitoring of 3C273 (2003)
Journal Article

On the accretion geometry of Cyg X-1 in the low/hard state (2003)
Journal Article

The X-ray/γ-ray spectrum of XTE J1550-564 in the very high state (2003)
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Simultaneous Chandra and Rossi X-Ray Timing Explorer Observations of the Nearby Bright Seyfert 2 Galaxy NGC 4945 (2003)
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The Power Density Spectrum of the Seyfert 2 Galaxy NGC 4945: The Relationship between X-ray Variability and Black Hole Mass (2003)
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Observing the effects of the event horizon in black holes (2003)
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The key difference between neutron stars and black holes is the presence/absence of a solid surface. Recent attempts to detect this difference have concentrated on the quiescent luminosity, but here these sources are faint and difficult to observe. I... Read More about Observing the effects of the event horizon in black holes.

The X-ray spectrum of the atoll source 4U 1608-52 (2002)
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Another interpretation of the power-law-type spectrum of an ultraluminous compact X-ray source in IC 342 (2002)
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Chandra Grating Observations of Seyfert galaxy IC 4329a (2002)
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Accretion flows in X-ray binaries (2002)
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Phase-resolved X-ray spectroscopy of the millisecond pulsar SAX J1808.4-3658 (2002)
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The X-ray spectrum of Cyg X-2 (2002)
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A comment on the colour-colour diagrams of low-mass X-ray binaries (2002)
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Disc-accreting neutron stars come in two distinct varieties, atolls and Z sources, named after their differently shaped tracks on a colour–colour diagram as the source luminosity changes. Here we present analysis of three transient atoll sources show... Read More about A comment on the colour-colour diagrams of low-mass X-ray binaries.

The origin of [FeII] emission in NGC 4151 (2002)
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The centre of NGC 4151 has been observed in the J band with the SMIRFS integral field unit (IFU) on the UK Infrared Telescope. A map of [Fe ii] emission is derived, and compared with the distributions of the optical narrow-line region and radio jet.... Read More about The origin of [FeII] emission in NGC 4151.

Recent results for AGN observed by the Rossi X-ray timing explorer (2001)
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On the complex disc-corona interactions in the soft spectral states of soft X-ray transients (2001)
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Galactic black hole binary systems (2001)
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Testing models of X-ray reflection from irradiated discs (2001)
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Observational Signatures of X-Ray-irradiated Accretion Disks (2001)
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Structure of the circumnuclear region of Seyfert 2 galaxies-clues from RXTE observations of NGC 4945 (2001)
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Mapping the inner accretion disc of the Galactic black hole J1550-564 through its rise to outburst (2001)
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We study the spectral properties of the first 14 observations of the rise to outburst phase of the X-ray transient J1550–564. Using both the PCA and HEXTE instruments, we find that the 3–200 keV spectra pass smoothly from a standard low/hard state to... Read More about Mapping the inner accretion disc of the Galactic black hole J1550-564 through its rise to outburst.

Probing the inner region of Cygnus X-1 in the low/hard state through its x-ray broadband spectrum (2001)
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We present the broadband X-ray spectrum of Cyg X-1 in the low/hard state as observed by the instruments on board BeppoSAX. The spectrum spans from 0.1 to 200 keV, allowing the total accretion luminosity to be observed rather than extrapolated, corres... Read More about Probing the inner region of Cygnus X-1 in the low/hard state through its x-ray broadband spectrum.

Hard X-Ray Emission from Low-Mass X-Ray Binaries (2000)
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The Relativistic Iron Line Profile in the Seyfert 1 Galaxy IC 4329A (2000)
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Structure of the Circumnuclear Region of Seyfert 2 Galaxies Revealed by Rossi X-Ray Timing Explorer Hard X-Ray Observations of NGC 4945 (2000)
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BeppoSAX observation of the black hole condidate Cyg X-1 (2000)
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Chandra Observations of Highly Obscured Seyfert 2 Galaxy NGC 4945 (2000)
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The 1989 May outburst of the soft X-ray transient GS 2023+338 (V404 Cyg) (1999)
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X-ray spectral evolution of GS 2023+338 (V404 Cyg) during decline after outburst (1999)
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Relativistic Smearing Detected in the Spectrum of CYG X-1 in Hard State Observed by BeppoSAX (1999)
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The X-ray spectrum of the polar BY Cam (1999)
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Relativistic smearing of the reflection spectrum in Galactic Black Hole Candidates (1999)
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Relativistic distortions in the X-ray spectrum of CYG X-1 (1999)
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Multiple-Object and Integral Field Near-Infrared Spectroscopy Using Fibers (1999)
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Black holes in AGN: recent results on IC 4329a and NGC 4945 (1999)
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Women in astronomy (1999)
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Observation of Centaurus A by the Rossi X-Ray Timing Explorer (1999)
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The discovery of non-linear X-ray variability in NGC 4051 (1999)
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On the Geometry of Accretion Flow in Soft X-Ray Transients. (1999)
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BeppoSAX observations of AM Her type stars. (1999)
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First BeppoSAX-NFI observations obtained in the framework of a program aiming to detect simultaneously the soft and hard X-ray emissions and the long term behaviour of AM Her type stars are presented. BL Hyi, the prototipe AM Her and the peculiar V13... Read More about BeppoSAX observations of AM Her type stars..

Evolution of the Accretion Flow in Nova MUSCAE 1991 (1998)
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BeppoSAX observations of the long period polar system V1309Ori (1998)
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The broad-band X-ray spectrum of MRK 3 (1998)
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The X-ray emission of the polar BL Hydri (1998)
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Black holes (1998)
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RXTE Observations of the Bright Seyfert Galaxy IC 4329a (1998)
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A deep X-ray low state of AM Herculis (1998)
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Constraints on the Structure of the Circumnuclear Region of the Seyfert 2 Galaxy NGC 4945 Inferred from Hard X-ray Observations with the RXTE (1998)
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Complex absorption and reflection of a multitemperature cyclotron-bremsstrahlung X-ray cooling shock in BY Cam (1998)
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Simultaneous X-ray and gamma-ray observations of CYG X-1 in the hard state by GINGA and OSSE (1997)
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Relativistically Smeared X-Ray Reprocessed Components in the GINGA Spectra of GS 2023+338 (1997)
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The X-ray spectrum of the dwarf nova SS CYG in quiescence and outburst (1997)
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Kinematics of the Broad Emission Line Region in NGC 5548 (1996)
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The X-ray spectra of Seyfert 2s observed by GINGA (1996)
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NGC 4945: The Brightest Seyfert 2 Galaxy at 100 keV (1996)
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Unified theories of active galactic nuclei: a hard X-ray sample of Seyfert 2 galaxies (1996)
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The soft X-ray spectrum of NGC 4151 (1996)
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Multicolour Imaging Polarimetry of the Galaxy NGC2146 (1995)
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Reverberation mapping by regularized linear inversion (1995)
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The GINGA hard X-ray spectrum of AM Herculis (1995)
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The soft X-ray spectrum of NGC 4151 revisited (1995)
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Optical properties of the new polar RXJ1940.2-1025 (1995)
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RE 1034+39: a high-state Seyfert galaxy? (1995)
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Imaging polarimetry of the Seyfert galaxy IC 4329A (1995)
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The average X-ray/gamma-ray spectra of Seyfert galaxies from GINGA and OSSE and the origin of the cosmic X-ray background (1995)
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Low-energy X-ray spectral variability of NGC 4051 (1995)
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The EF ERI GINGA data and physical models for the X-ray spectra of AM Herculis systems (1995)
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Joint ROSAT-Compton GRO observations of the X-ray bright Seyfert galaxy IC 4329A (1995)
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The complex variable soft X-ray spectrum of NGC 5548 (1995)
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Spectral study of GX 339-4 in the low-intensity state observed with GINGA (1994)
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Nonthermal pair models reflection and X-ray spectral variability of active galaxies (1994)
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The Kinematics of Broad Line Clouds in NGC 5548 (1994)
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Physical Processes in the X-Ray / Gamma-Ray Source of IC4329A (1994)
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Low state properties of the low-mass X-ray binary X1608-522 observed with GINGA (1993)
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Resolving the iron K line in Cygnus X-2 - an observation with BBXRT (1993)
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Stellar Accretion in Active Galactic Nuclei (1993)
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Unified theories of active galactic nuclei - The hard X-ray spectrum of NGC 1068 (1993)
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Solving the Mystery of the X-Ray Periodicity in the Seyfert Galaxy NGC6814 (1993)
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X-ray light curves of active galactic nuclei are phase incoherent (1993)
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X-ray spectra and time variability of active galactic nuclei (1993)
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Spectral Study of GX339-4 in the Low Intensity State Observed with GINGA (1993)
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The high-energy spectrum of Cygnus X-1 revisited (1993)
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The Iron K Line as a Probe of Beamed X-Ray Emission in Active Galactic Nuclei (1993)
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The broad-band X-ray spectral variability of MRK 841 (1993)
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RX J1940.2-1025 (1993)
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BBXRT and GINGA observations of AGN (1993)
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Evidence for an ionized reprocessor in NGC 6814 (1992)
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X-ray spectrum of BL Lac object PKS2155-304 (1992)
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The X-ray variability of NGC 6814 - Power spectrum (1992)
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Observational Tests of the Nonthermal e+/- Pair/Reflection Model for AGNs (1992)
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Broad Band X-Ray Telescope observations of NGC 4151 - Iron line diagnostics (1992)
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Erratum: ``High-energy neutrinos from active galactic nuclei'' [Phys. Rev. Lett. 66, 2697 (1991)] (1992)
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An ionized accretion disk in Cygnus X-1 (1992)
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High-energy neutrinos from active galactic nuclei (1991)
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A disc-reflected component in the spectra of X-ray bursters (1991)
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Anisotropic inverse Compton emission (1991)
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The X- and gamma-ray continuum of active galactic nuclei (1990)
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Pair loading in compact sources (1990)
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Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei (1990)
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Simultaneous multifrequency observations of the Seyfert 1 galaxy NGC 4051 - Constant optical-infrared emission observed during large-amplitude X-ray variability (1990)
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Simultaneous Multifrequency Observations of the Seyfert 1 Galaxy 4051 (1989)
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Frequency-dependent variability in synchrotron self-Compton models (1989)
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The behavior of compact non-thermal sources with pair production (1989)
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Pair plasmas and the variability of AGN (1988)
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The enhancement of infrared emission in interacting galaxies (1988)
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Photon-starved, pair-loaded compact sources and the X-ray background (1988)
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X-ray observations of IRAS selected Seyfert galaxies and obscuration of the broad-line region (1988)
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X-ray Observations of IRAS-Selected Galaxies and Obscuration of the Broad-Line Region (1987)
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