The spectrum of the bright Seyfert I galaxy MCG-6-30-15 shows a broad Fe K-alpha emission line, generally interpreted to originate very close to the central black hole which must then have a high spin. The observed X-ray variability is driven by a powerlaw component, with little variability found in the iron line energy band. The disconnection of continuum and line variability may be a consequence of strong gravitational light bending. The X-ray spectrum of MCG-6-30-15 is however complex, strongly modified at soft X-ray energies by warm absorbers, which some workers have extended to build an absorption-dominated model of the whole source behaviour. The absorption model interprets the whole X-ray spectrum without a relativistic reflection component and attributes most variability to the warm absorbers. We re-examine the XMM-Newton, Chandra and Suzaku data taken in 2001, 2004 and 2006, respectively, and construct a model consisting of several warm absorbers confirmed by spectral analysis, together with a relativistically blurred reflection component that explains both the soft and hard excesses as well. The model works well on data from all epochs, demonstrating that the reflection model provides a consistent interpretation of the broadband spectrum of MCG-6-30-15.
The spacetime geometry around astrophysical black holes is well approximated by the Kerr metric, but deviations from standard predictions are possible in a number of scenarios beyond Einstein's gravity and in the presence of exotic matter. In this paper, we present the constraints on possible deviations from the Kerr solution using X-ray reflection spectroscopy from the analysis of real data. We use the relativistic X-ray reflection code RELXILL modified to a generic stationary, axisymmetric and asymptotically flat black hole metric. We analyze 350 ks long XMM-Newton observations of the AGN in…
MCG-5-23-16 was targeted in early 2015 with a half mega-seconds observing campaign using NuSTAR. Here we present the spectral analysis of these datasets along with an earlier observation and study the relativistic reflection and the primary coronal source. The data show strong reflection features in the form of both narrow and broad iron lines plus a Compton reflection hump. A cutoff energy is significantly detected in all exposures. The shape of the reflection spectrum does not change in the two years spanned by the observations, suggesting a stable geometry. A strong positive correlation is …
We present the results of a multi-epoch and multi-instrument study of the supermassive black hole at the center of the galaxy MCG-05-23-16 aiming at the determination of its spin. We have analyzed high quality X-ray data of MCG-05-23-16 from XMM-Newton, Suzaku, and NuSTAR obtained over a period of about 10~years. We have built a double-reflection spectral model that well describes the observed spectrum based on prior results suggesting that the iron K$α$ line includes both a broad component from the disk's reflection spectrum and a narrow component due to fluorescence and scattering off materi…
We present the spectral analysis with the Nuclear Spectroscopic Telescope Array (NuSTAR) of four isolated galaxies with active galactic nuclei selected from 2MIG catalogue: NGC 5347, ESO 438-009, MCG-02-09-040, and IGR J11366-6002. We also used the Swift/Burst Alert Telescope (BAT) data up to $\sim$ 150 keV for MCG 02-09-040, ESO 438-009, and IGR J11366-6002 as well as the Swift/XRT data in 0.3--10 keV energy band for NGC 5347, ESO 438-009, and IGR J11366-6002. All the sources appear to have the reflected spectrum component with different reflection fractions in addition to the primary power-l…
We present modelling of X-ray polarisation spectra emerging from the two competing scenarios that are proposed to explain the broad Fe Kα line in the Seyfert 1 galaxy MCG-6-30-15. The polarisation signature of complex absorption is studied for a partial covering scenario using a clumpy wind and compared to a reflection model based on the lamp-post geometry. The shape of the polarisation percentage and angle as a function of photon energy are found to be distinctly different between the reflection and the absorption case. Relativistic reflection produces significantly stronger polarisation in t…
We present a re-analysis of the XMM-Newton and NuSTAR observing campaign for the well-studied, X-ray-bright AGN MCG-06-30-15. In particular, we consider a disc model with finite thickness. By fitting the disc reflection spectra in the data, we obtain a black hole spin of 0.87--0.99 (90\% confidence range) after taking the thickness of the disc into consideration. Spectral models with a grid of mass accretion rate from 0 to $30\%\dot{M}_{\rm Edd}$ are calculated for MCG-06-30-15. This result is obtained by considering a free disc reflection fraction parameter $f_{\rm refl}$ and is consistent wi…
Time-resolved XRISM spectroscopy reveals the evolution and structure of the corona in MCG-6-30-15
The Ohio State University（俄亥俄州立大学）；Stanford University（斯坦福大学）；Harvard & Smithsonian（哈佛大学与史密森尼学会）；University of Maryland, College Park（马里兰大学帕克分校）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Cambridge University（剑桥大学）；Technion（以色列理工学院）；University of Maryland, Baltimore County (UMBC)（马里兰大学巴尔的摩县分校）
We have investigated spectral variation of the Seyfert 1 galaxy MCG-6-30-15 observed with Suzaku in January 2006 for three separate periods spreading over fourteen days. We found that the time-averaged continuum energy spectrum between 1 keV and 40 keV can be approximated with a spectral model composed of the direct power-law component, its reflection component, two warm absorbers with different ionization states, and neutral absorption. We have taken two approaches to study its spectral variation at various timescales: The first approach is to make intensity-sliced spectra and study correlati…
We present a spectral analysis of the 118 ks High Energy Transmission Gratings (HETG) observation of the X-ray bright Seyfert 1.5 galaxy MCG +8-11-11, in conjunction with 100 ks of archival Suzaku data, aimed at investigating the signatures of warm absorption and Compton reflection reported from previous Suzaku and XMM-Newton studies of the source. Contrary to previous results, we find that warm absorption is not required by the data. Instead, we report upper limits on absorption lines that are below previous (marginal) detections. Fe Ka line emission is clearly detected and is likely resolved…
Complexities in the X-ray spectrum of the nearby Seyfert 1.2 galaxy MCG-6-30-15 are commonly interpreted in terms of a broad iron line and the associated Compton reflection hump from the innermost relativistic regions of an accretion disk around a rapidly spinning black hole. However, an alternative model has recently been proposed in which these spectral features are caused entirely by complex (ionized and partial-covering) absorption. By considering the fluorescent emission that must accompany photoelectric absorption, we show that the absorption-dominated model over-predicts the 6.4keV iron…
We apply the light bending model of X-ray variability to Suzaku data of the Seyfert 1 galaxy MCG-6-30-15. We analyze the energy dependence of the root mean square (rms) variability, and discuss conditions necessary for the model to explain the characteristic decrease of the source variability around 5-8 keV. A model, where the X-ray source moves radially rather than vertically close to the disk surface, can indeed reproduce the reduced variability near the energy of the Fe Kalpha line, although the formal fit quality is poor. The model then predicts the energy spectra, which can be compared to…
Several X-ray observations have recently revealed the presence of reverberation time delays between spectral components in AGN. Most of the observed lags are between the power-law Comptonization component, seen directly, and the soft excess produced by reflection in the vicinity of the black hole. NGC 4151 was the first object to show these lags in the iron K band. Here, we report the discovery of reverberation lags in the Fe K band in two other sources: MCG-5-23-16 and NGC 7314. In both objects, the 6-7 keV band, where the Fe K line peaks, lags the bands at lower and higher energies with a ti…
MCG-5-23-16 is one of the first AGN where relativistic reverberation in the iron K line originating in the vicinity of the supermassive black hole was found, based on a short XMM-Newton observation. In this work, we present the results from long X-ray observations using Suzaku, XMM-Newton and NuSTAR designed to map the emission region using X-ray reverberation. A relativistic iron line is detected in the lag spectra on three different time-scales, allowing the emission from different regions around the black hole to be separated. Using NuSTAR coverage of energies above 10 keV reveals a lag bet…
We analyse 400 ks of XMM-Newton data on the active galactic nucleus NGC 1365 using principal component analysis (PCA) to identify model independent spectral components. We find two significant components and demonstrate that they are qualitatively different from those found in MCG?6-30-15 using the same method. As the variability in NGC 1365 is known to be due to changes in the parameters of a partial covering neutral absorber, this shows that the same mechanism cannot be the driver of variability in MCG-6-30-15. By examining intervals where the spectrum shows relatively low absorption we sepa…
We present an X-ray time lag analysis, as a function of Fourier frequency, for MCG-6-30-15 and Mrk 766 using long term XMM-Newton light curves in the 0.5-1.5 keV and the 2-4 keV energy bands, together with some physical modelling of the corresponding time lag spectra. Both the time lag spectra of MCG-6-30-15 and Mrk 766 show negative values (i.e. soft band variations lag behind the corresponding hard band variations) at high frequencies, around 0.001 Hz, similar to those previously observed from 1H 0707-495. The remarkable morphological resemblance between the time lag spectra of MCG-6-30-15 a…
We analyse the spectral variability of MCG--06-30-15 with 600 ks of XMM-Newton data, including 300 ks of new data from the joint XMM-Newton and NuSTAR 2013 observational campaign. We use principal component analysis to find high resolution, model independent spectra of the different variable components of the spectrum. We find that over 99 per cent of the variability can be described by just three components, which are consistent with variations in the normalisation of the powerlaw continuum (~97 per cent), the photon index (~2 per cent), and the normalisation of a relativistically blurred ref…
MCG-6-30-15 is one of the most observed Narrow Line Seyfert 1 galaxies in the X-ray band. In this paper we examine the X-ray time lags in this source using a total of 600 ks in observations (440 ks exposure) taken with the XMM-Newton telescope (300 ks in 2001 and 300 ks in 2013). Both the old and new observations show the usual hard lag that increases with energy, however, the hard lag turns over to a soft lag at frequencies below ~1e-4 Hz. The highest frequencies (~1e-3 Hz) in this source show a clear soft lag, as previously presented for the first 300 ks observation, but no clear iron K lag …
The flux-flux plot (FFP) method can provide model-independent clues regarding the X-ray variability of active galactic nuclei. To use it properly, the bin size of the light curves should be as short as possible, provided the average counts in the light curve bins are larger than $\sim 200$. We apply the FFP method to the 2013, simultaneous XMM-Newton and NuSTAR observations of the Seyfert galaxy MCG$-$6-30-15, in the 0.3-40 keV range. The FFPs above $\sim 1.6$ keV are well-described by a straight line. This result rules out spectral slope variations and the hypothesis of absorption driven vari…
We propose a simple spectral model for the Seyfert 1 Galaxy MCG-6-30-15 that can explain most of the 1 - 40 keV spectral variation by change of the partial covering fraction, similar to the one proposed by Miller et al. (2008). Our spectral model is composed of three continuum components; (1) a direct power-law component, (2) a heavily absorbed power-law component by mildly ionized intervening matter, and (3) a cold disk reflection component far from the black hole with moderate solid-angle (Ω/2π \approx 0.3) accompanying a narrow fluorescent iron line. The first two components are affected by…
We present an analysis of the co-added and individual 0.7-40 keV spectra from seven Suzaku observations of the Sy 1.5 galaxy NGC 5548 taken over a period of eight weeks. We conclude that the source has a moderately ionized, three-zone warm absorber, a power-law continuum, and exhibits contributions from cold, distant reflection. Relativistic reflection signatures are not significantly detected in the co-added data, and we place an upper limit on the equivalent width of a relativistically broad Fe K line at EW \leq 26 eV at 90% confidence. Thus NGC 5548 can be labeled an "weak" type-1 AGN in te…
We present preliminary results on the hard X-ray emission properties of the Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed together with two SWIFT/XRT snapshot observations performed in August and October 2009, quasi-simultaneously to INTEGRAL pointed observations of MCG+8-11-11. No correlation is observed between the hard X-ray flux and the spectral slope, while the position of the high-energy cut-off is found to have varied during the INTEGRAL observations. This points to a change in the tempe…
Degeneracy in Accretion Disk Spectra from Naked Singularities and Kerr Black Holes: Application to the AGN MCG-06-30-15
PDPIAS, Charusat University（帕迪皮阿斯，查鲁萨特大学）；International Centre for Space and Cosmology, School of Arts and Sciences, Ahmedabad University（国际空间与宇宙学中心，艺术与科学学院，艾哈迈达巴德大学）；Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research（天文与天体物理系，塔塔基础研究所）；MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理与空间研究所，麻省理工学院）
The X-ray variations of hard state black hole X-ray binaries above 2 keV show 'hard lags', in that the variations at harder energies follow variations at softer energies, with a time-lag τdepending on frequency νapproximately as τ\propto ν^{-0.7}. Several models have so far been proposed to explain this time delay, including fluctuations propagating through an accretion flow, spectral variations during coronal flares, Comptonisation in the extended hot corona or a jet, or time-delays due to large-scale reflection from the accretion disc. In principle these models can be used to predict the sha…
Measurements of the high-energy cut-off in the coronal continuum of active galactic nuclei have long been elusive for all but a small number of the brightest examples. We present a direct measurement of the cut-off energy in the nuclear continuum of the nearby Seyfert 1.9 galaxy MCG -05-23-016 with unprecedented precision. The high sensitivity of NuSTAR up to 79 keV allows us to clearly disentangle the spectral curvature of the primary continuum from that of its reflection component. Using a simple phenomenological model for the hard X-ray spectrum, we constrain the cut-off energy to $116_{-5}…
We have carried out an extensive X-ray spectral study of the bare Seyfert-1 galaxy MCG--02--58--22 to ascertain the nature of the X-ray reprocessing media, using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016) . The most significant results of our investigation are: 1. The primary X-ray emission from the corona is constant in these observations, both in terms of the power law slope ($Γ=1.80$) and luminosity ($L_{2-10 \rm keV}= 2.55\times 10^{44} $ erg/s). 2. The soft excess flux decreased by a factor of two in 2016, the Compton hump weakened/vani…
We present an X-ray spectral and timing model to investigate the broad and variable iron line seen in the high flux state of Mrk 335. The model consists of a variable X-ray source positioned along the rotation axis of the black hole that illuminates the accretion disc producing a back-scattered, ionized reflection spectrum. We compute time lags including full dilution effects and perform simultaneous fitting of the 2-10 keV spectrum and the frequency-dependent time lags of 2.5-4 vs. 4-6.5 keV bands. The best-fitting parameters are consistent with a black hole mass of approximately 1.3 x 10^7 M…
We present XMM-Newton observations of three AGN taken as part of a hunt to find very heavily obscured Compton-thick AGN. For obscuring columns greater than 10^25 cm^-2, AGN are only visible at energies below 10 keV via reflected/scattered radiation, characterized by a flat power-law. We therefore selected three objects (ESO 417-G006, IRAS 05218-1212, and MCG -01-05-047) from the Swift BAT hard X-ray survey catalog with Swift X-ray Telescope XRT 0.5-10 keV spectra with flat power-law indices as candidate Compton-thick sources for follow-up observations with the more sensitive instruments on XMM…
In a previous paper, we presented an extension of our reflection model RELXILL_NK to include the finite thickness of the accretion disk following the prescription in Taylor & Reynolds (2018). In this paper, we apply our model to fit the 2013 simultaneous observations by NuSTAR and XMM-Newton of the supermassive black hole in MCG-06-30-15 and the 2019 NuSTAR observation of the Galactic black hole in EXO 1846-031. The high-quality data of these spectra had previously led to precise black hole spin measurements and very stringent constraints on possible deviations from the Kerr metric. We find th…
We extract all the XMM-Newton EPIC pn burst mode spectra of GX 339-4, together with simultaneous/contemporaneous RXTE data. These include three disc dominated and two soft intermediate spectra, and the combination of broad bandpass/moderate spectral resolution gives some of the best data on these bright soft states in black hole binaries. The disc dominated spectra span a factor three in luminosity, and all show that the disc emission is broader than the simplest multicolour disc model. This is consistent with the expected relativistic smearing and changing colour temperature correction produc…
We present simple XSPEC models for fitting excess variance spectra of AGN. Using a simple Monte-Carlo approach, we simulate a range of spectra corresponding to physical parameters varying, then calculate the resulting variance spectra. Starting from a variable power-law, we build up a set of models corresponding to the different physical processes that can affect the final excess variance spectrum. We show that the complex excess variance spectrum of IRAS 13224-3809 can be well described by such an intrinsic variability model, where the power-law variability is damped by relativistic reflectio…
AGN exhibit complex hard X-ray spectra. Our current understanding is that the emission is dominated by inverse Compton processes which take place in the corona above the accretion disk, and that absorption and reflection in a distant absorber play a major role. These processes can be directly observed through the shape of the continuum, the Compton reflection hump around 30 keV, and the iron fluorescence line at 6.4 keV. We demonstrate the capabilities of Simbol-X to constrain complex models for cases like MCG-05-23-016, NGC 4151, NGC 2110, and NGC 4051 in short (10 ksec) observations. We comp…
Astrophysical black hole systems are the ideal laboratories for testing Einstein's theory of gravity in the strong field regime. We have recently developed a framework which uses the reflection spectrum of black hole systems to perform precision tests of general relativity by testing the Kerr black hole hypothesis. In this paper, we analyze XMM-Newton and NuSTAR observations of the supermassive black hole in the Seyfert 1 galaxy MCG-06-30-15 with our disk reflection model. We consider the Johannsen metric with the deformation parameters $α_{13}$ and $α_{22}$, which quantify deviations from the…
Relativistic reflection features in the X-ray spectra of black hole binaries and AGNs originate from illumination of the inner part of the accretion disk by a hot corona. In the presence of high quality data and with the correct astrophysical model, X-ray reflection spectroscopy can be quite a powerful tool to probe the strong gravity region, study the morphology of the accreting matter, measure black hole spins, and even test Einstein's theory of general relativity in the strong field regime. There are a few relativistic reflection models available today and developed by different groups. All…
Accreting stellar mass black holes (BHs) routinely exhibit Type-C quasi-periodic oscillations (QPOs). These are often interpreted as Lense-Thirring precession of the inner accretion flow, a relativistic effect whereby the spin of the BH distorts the surrounding space-time, inducing nodal precession. The best evidence for the precession model is the recent discovery, using a long joint XMM-Newton and NuSTAR observation of H 1743-322, that the centroid energy of the iron fluorescence line changes systematically with QPO phase. This was interpreted as the inner flow illuminating different azimuth…
In a previous paper, one of us calculated iron K$α$ line profiles emitted from possible accretion disks around traversable wormholes as a first step to use X-ray reflection spectroscopy to search for astrophysical wormholes in active galactic nuclei. In the present paper, we extend that work and construct an XSPEC model for the whole relativistic reflection spectrum. We apply our model to XMM-Newton and NuSTAR observations of the supermassive object in MCG-6-30-15 and we check whether these observations prefer the hypothesis that the central body is a Kerr black hole or a traversable wormhole.…
The extreme NLS1 galaxy IRAS 13224-3809 shows significant variability, frequency depended time lags, and strong Fe K line and Fe L features in the long 2011 XMM-Newton observation. In this work we study the spectral properties of IRAS 13224-3809 in detail, and carry out a series of analyses to probe the nature of the source, focusing in particular on the spectral variability exhibited. The RGS spectrum shows no obvious signatures of absorption by partially ionised material (warm absorbers). We fit the 0.3-10.0 keV spectra with a model that includes relativistic reflection from the inner accret…
The recent detection of X-ray reverberation lags, especially in the Fe Kα line region, around Active Galactic Nuclei (AGN) has opened up the possibility of studying the time-resolved response (reflection) of hard X-rays from the accretion disk around supermassive black holes. Here, we use general relativistic transfer functions for reflection of X-rays from a point source located at some height above the black hole to study the time lags expected as a function of frequency and energy in the Fe Kα line region. We explore the models and the dependence of the lags on key parameters such as the he…
We examine a 200 ks XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 493. The active galaxy was half as bright as in a previous 2003 snapshot observation and the current lower flux enables a study of the putative reflection component in detail. We determine the characteristics of the 2015 X-ray continuum by first analyzing the short-term variability using model-independent techniques. We then continue with a time-resolve analysis including spectral fitting and modelling the fractional variability. We determine that the variability arises from changes in the amount of primary flux…
We present results from spectral fitting of the very high state of GX~339-4 with NuSTAR and Swift. We use relativistic reflection modelling to measure the spin of the black hole and inclination of the inner disk, and find a spin of $a=0.95^{+0.02}_{-0.08}$ and inclination of $30$°$\pm1$ (statistical errors). These values agree well with previous results from reflection modelling. With the exceptional sensitivity of NuSTAR at the high-energy side of the disk spectrum, we are able to constrain multiple physical parameters simultaneously using continuum fitting. By using the constraints from refl…
X-ray reflection signatures are observed around multiple classes of accreting compact objects. Modelling these features yield important constraints on the physics of accretion disks, motivating the development of X-ray reflection models appropriate for a variety of systems and illumination conditions. Here, constant density ionized X-ray reflection models are presented for a disk irradiated with a very hard power-law X-ray spectrum (Γ< 1) and a variable high-energy cutoff. These models are then applied to the Suzaku data of the accreting X-ray pulsar LMC X-4, where very good fits are obtained …
We present a broad band spectral analysis of the black hole binary GX~339-4 with NuSTAR and Swift using high density reflection model. The observations were taken when the source was in low flux hard states (LF) during the outbursts in 2013 and 2015, and in a very high flux soft state (HF) in 2015. The high density reflection model can explain its LF spectra with no requirement for an additional low temperature thermal component. This model enables us to constrain the density in the disc surface of GX~339-4 in different flux states. The disc density in the LF state is $\log(n_{\rm e}/$ cm$^{-3…
We present the first results obtained by the application of the KYNREFREV-reverberation model, which is ready for its use in XSPEC. This model computes the time dependent reflection spectra of the disc as a response to a flash of primary power-law radiation from a point source corona located on the axis of the black hole accretion disc (lamp-post geometry). Full relativistic effects are taken into account. The ionisation of the disc is set for each radius according to the amount of the incident primary flux and the density of the accretion disc. We tested the model by fitting model predictions…
We present a new release of the RELTRANS model to fit the complex cross-spectrum of accreting black holes as a function of energy. The model accounts for continuum lags and reverberation lags self-consistently in order to consider the widest possible range of X-ray variability timescales. We introduce a more self-consistent treatment of the reverberation lags, accounting for how the time variations of the illuminating flux change the ionisation level of the accretion disc. This process varies the shape of the reflection spectrum in time causing an additional source of lags besides the light cr…
A comprehensive wideband spectral analysis of the brightest black hole X-ray binary 4U $1543-47$ during its 2021 outburst is carried out for the first time using NICER, NuSTAR, and AstroSat observations by phenomenological and reflection modelling. The source attains a super-Eddington peak luminosity and remains in the soft state, with a small fraction ($< 3\%$) of the inverse-Comptonized photons. The spectral modelling reveals a steep photon index ($Γ\sim 2-2.6$) and relatively high inner disk temperature ($T_{in}\sim 0.9-1.27$ keV). The line-of-sight column density varies between ($0.45-0.54…
X-ray reflection spectroscopy is a powerful technique for probing the nature of gravity around black holes in the so-called strong field regime. One of the most popular of such probes is to look at theory-agnostic deviations away from the Kerr solution, which is the only astrophysically relevant black hole solution within classical general relativity, in order to verify whether astrophysical black holes are described by the Kerr metric. We have recently extended our X-ray reflection spectroscopy framework to a class of very general axisymmetric non-Kerr black holes proposed by Konoplya, Rezzol…
In the centre of our galaxy lies a super-massive black hole, identified with the radio source Sagittarius A*. This black hole has an estimated mass of around 4 million solar masses. Although Sagittarius A* is quite dim in terms of total radiated energy, having a luminosity that is a factor of $10^{10}$ lower than its Eddington luminosity, there is now compelling evidence that this source was far brighter in the past. Evidence derived from the detection of reflected X-ray emission from the giant molecular clouds in the galactic centre region. However, the interpretation of the reflected emissio…
We discuss the application of simple relativistically-blurred X-ray reflection models to the determination of the spin and the inner radius of the disc in accreting black holes. Observationally, the nature of the corona is uncertain a priori, but a robust determination of the inner disk radius can be made when the disc emissivity index is tightly constrained. When the inner disc is well illuminated, the black hole spin can also be determined. Using reflection modelling derived from ray tracing, we show that robust determination of disc truncation requires that the location of the coronal sourc…
I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black holes in X-ray binaries to the supermassive black holes in active galactic nuclei. After describing the basic assumptions of this approach, I lay out the detailed methodology focusing on "best practices" that have been found necessary to obtain robust results. Reflecting my own biases, this review is slanted towards a discussion of supermassive black hole (SM…
We present results from a deep Suzaku observation of the black hole in LMC X-1, supplemented by coincident monitoring with RXTE. We identify broad relativistic reflection features in a soft disc-dominated spectrum. A strong and variable power-law component of emission is present which we use to demonstrate that enhanced Comptonisation strengthens disc reflection. We constrain the spin parameter of the black hole by modelling LMC X-1's broad reflection features. For our primary and most comprehensive spectral model, we obtain a high value for the spin: a* = 0.97(+0.01,-0.13) (68 per cent confid…
We methodically model the broad-band Suzaku spectra of a small sample of six 'bare' Seyfert galaxies: Ark 120, Fairall 9, MCG-02-14-009, Mrk 335, NGC 7469 and SWIFT J2127.4+5654. The analysis of bare Seyferts allows a consistent and physical modelling of AGN due to a weak amount of any intrinsic warm absorption, removing the degeneracy between the spectral curvature due to warm absorption and the red-wing of the Fe K region. Through effective modelling of the broad-band spectrum and investigating the presence of narrow neutral or ionized emission lines and reflection from distant material, we …
Accretion models predict that fluorescence lines broadened by relativistic effects should arise from reflection of X-ray emission onto the inner region of the accretion disc surrounding the central black hole of active galactic nuclei (AGN). The theory behind the origin of relativistic lines is well established, and observational evidence from a moderate number of sources seems to support the existence of these lines. The aim of this work is to establish the fraction of AGN with relativistic Fe Kalpha lines, and study possible correlations with source physical properties. An XMM-Newton collect…
We present the broadband (0.3-40.0 keV) X-ray analysis of a unique intermediate polar Paloma using simultaneous data from XMM-Newton and NuSTAR observatories. The X-ray power spectra show strong modulations over orbital period compared to spin period. The orbit folded lightcurves show single broad hump like structure with strong dips for soft to medium X-rays (0.3-10.0 keV). The energy dependent dips at $ϕ\sim 0.16$ and $0.5$ arise due to complex intrinsic absorber, strong enough to have effect well around 15 keV. The absorber could potentially be contributed from accretion curtain/ accretion …
Characteristic signatures that X-ray reverberation from an extended corona can manifest in the observed PSD of AGN are investigated. The presence of two X-ray blobs illuminating an accretion disc can cause the interference between two reprocessing-echo components and produce distinct physical features in the PSD. The oscillatory structures (e.g., dips and humps) are seen but, contrarily to the lamp-post case, the strongest dip is not always the one at the lowest frequency. Instead, we find the frequency where the strongest dip is seen associates to the lower-source height while the lowest freq…
Detecting and modelling the reprocessed hard X-ray emission component in the accretion flow, so-called reflection spectrum is a main tool to estimate black hole spins in a wide range of astrophysical black holes regardless of their mass or distance. In this work, we studied the X-ray spectra of the Seyfert I galaxy III Zw 2 using multi-epoch XMM-Newton, NuSTAR and Suzaku observations. The X-ray spectra exhibit a soft-excess below 1 keV and a prominent excess at the location of the broad Fe Kα line at 6.4 keV. To account for these spectral features, we have fitted the spectra with multiple mode…
"Changing look" Active Galactic Nuclei (AGN) are a subset of Seyfert galaxies characterized by rapid transitions between Compton-thin and Compton-thick regimes. In their Compton-thin state, the central engine is less obscured, hence spectroscopy or timing observations can probe their innermost structures. However, it is not clear if the observed emission features and the Compton hump are associated with relativistic reflection onto the accretion disc, or complex absorption by distant, absorbing gas clouds passing by the observer's line-of-sight. Here, we investigate these two scenarios under t…
Since the discovery of the first broad iron-K line in 1995 from the Seyfert Galaxy MCG--6-30-15, broad iron-K lines have been found in several other Seyfert galaxies, from accreting stellar mass black holes and even from accreting neutron stars. The iron-K line is prominent in the reflection spectrum created by the hard X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron-L line emission should be detectable when the iron abundance is high. Here we report the first disc…
