NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole scale. Here, we report the results of a large XMM-Newton campaign in 2015 to study these short delays further. Analyzing high quality data that span time scales between hours and decades, we find that neutral and ionized absorption contribute significantly to the spectral shape. Accounting for their effects, we find no evidence for a relativistic reflection component, contrary to early work. Energy-dependent lags are significantly measured in the new data, but with an energy profile that does not resemble a broad iron line, in contrast to the old data. The complex lag-energy spectra, along with the lack of strong evidence for a relativistic spectral component, suggest that the energy-dependent lags are produced by absorption effects. The long term spectral variations provide new details on the variability of the narrow Fe K$α$ line . We find that its variations are correlated with, and delayed with respect to, the primary X-ray continuum. We measure a delay of $τ= 3.3^{+1.8}_{-0.7}$ days, implying an origin in the inner broad line region (BLR). The delay is half the H$β$ line delay, suggesting a geometry that differs slightly from the optical BLR.
In this work, we re-analyze the Fermi-LAT observation of NGC 1275 to search for axion-like particle (ALP) effects and constrain ALP parameters. Instead of fitting the observed spectrum with ALP models, we adopt an alternative method for the analysis of this source which calculates the irregularity of the spectrum. With the newly used method, we find no spectral oscillation for the NGC 1275 and rule out couplings $g_{aγ}>3\times10^{-12}\,{\rm GeV^{-1}}$ around ALP mass of $m_a\sim$ 1 neV at 95\% confidence level, which is more stringent than the previous results. We also show that the constrain…
The discovery of 3:2 quasi-periodic oscillations (QPOs) in the ultraluminous X-ray source NGC 1313 X-1 suggests it harbors an intermediate-mass black hole (IMBH). We test this numerically by modelling the 3:2 QPOs and the associated X-ray spectrum based on the epicyclic resonance model and a disk-corona model with large-scale magnetic fields generated by the Cosmic Battery mechanism. The combined QPO-frequency and spectral fitting indicates that the BH mass ranges from 2524M_sun to 6811M_sun confirming its IMBH nature, and the BH spin is probably higher than ~0.3.
Revisiting the observation-theory confrontation in high-frequency QPOs:a new QPO in NGC 5506, intermediate mass black holes, and the crucial role of accretion state
We study the 205.9 Hz pulsations of the accreting millisecond X-ray pulsar NGC 6440 X-2 across all outbursts observed with the Rossi X-ray Timing Explorer over a period of 800 days. We find the pulsations are highly sinusoidal with a fundamental amplitude of 5%-15% rms and a second harmonic that is only occasionally detected with amplitudes of <2% rms. By connecting the orbital phase across multiple outbursts, we obtain an accurate orbital ephemeris for this source and constrain its 57 min orbital period to sub-ms precision. We do not detect an orbital period derivative to an upper limit of $ …
The acceleration of LMXB 4U 1820-30 that derived from its orbital-period derivative $\dot P_{\rm b}$ was supposed to be the evidence for an Intermediate-mass Black Hole (IMBH) in the Galactic globular cluster (GC) NGC 6624. However, we find that the anomalous $\dot P_{\rm b}$ is mainly due to the gravitational wave emission, rather than the acceleration in cluster potential. Using the standard structure models of GCs, we simulate acceleration distributions for pulsars in the central region of the cluster. By fitting the acceleration of J1823-3021A with the simulated distribution profiles (maxi…
Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Liebniz Universität Hannover（马克斯·普朗克引力物理学研究所（爱因斯坦研究所），莱布尼茨汉诺威大学）；School of Physics, Indian Institute of Science Education and Research Thiruvananthapuram（印度科学教育与研究学院特里凡得琅物理学院）；Joint Astronomy Programme, Department of Physics, Indian Institute of Science（印度科学学院物理学院联合天文学项目）；Vrije Universiteit Brussel（布鲁塞尔自由大学）；Raman Research Institute（拉曼研究所）；The Institute of Mathematical Sciences（数学科学研究所）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；Department of Astronomy, Astrophysics, and Space Engineering, Indian Institute of Technology Indore（印度理工学院印多尔分校天文、天体物理与空间工程系）
We present results of new XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the few ULXs to show quasi-periodic oscillations (QPO). We detect QPOs in each of four new (~ 100 ks) pointings, expanding the range of frequencies observed from 10 - 40 mHz. We compare our results with the timing and spectral correlations seen in stellar-mass black hole systems, and find that the qualitative nature of the timing and spectral behavior of NGC 5408 X-1 is similar to systems in the steep power-law state exhibiting Type-C QPOs. However, in order for this analogy to quanti…
We perform both timing and spectral analyses using the archival X-ray data taken with Swift, XMM-Newton, NICER, and NuSTAR from 2016 to 2020 to study an ultra-luminous pulsar, NGC 7793 P13, that showed a long period of super-Eddington accretion. We use the Rayleigh test to investigate the pulsation at different epochs, and confirm the variation of the pulse profile with the finite Gaussian mixture modelling and two-sample Kuiper test. Taking into account the periodic variation of the spin periods caused by the orbital Doppler effect, we further determine an orbital period of ~65 d and show tha…
We present the Robert C. Byrd Green Bank Telescope discovery of the highly eccentric binary millisecond pulsar PSR J1835$-$3259A in the Fermi Large Area Telescope-detected globular cluster NGC 6652. Timing over one orbit yields the pulse period 3.89 ms, orbital period 9.25 d, eccentricity $\sim 0.95$, and an unusually high companion mass of $0.74\,M_{\odot}$ assuming a $1.4\,M_{\odot}$ pulsar. We caution that the lack of data near periastron prevents a precise measurement of the eccentricity, and that further timing is necessary to constrain this and the other orbital parameters. From tidal co…
A Candidate Open Cluster Pulsar: Timing Analysis of PSR J1922+3745 in NGC 6791
Beijing Normal University（北京师范大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Guizhou University（贵州大学）；Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences（中国科学院射电天文与技术重点实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Swinburne University of Technology（斯威本科技大学）；OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery（ARC引力波发现卓越中心）
We present the timing and spectral analysis of the Compton Thick Seyfert 2 active galactic nuclei NGC 1068 observed using {\it NuSTAR} and {\it XMM-Newton}. In this work for the first time we calculated the coronal temperature ($\rm{kT_{e}}$) of the source and checked for its variation between the epochs if any. The data analysed in this work comprised of (a) eight epochs of observations with {\it NuSTAR} carried out during the period December 2012 to November 2017, and, (b) six epochs of observations with {\it XMM-Newton} carried out during July 2000 to February 2015. From timing analysis of …
We report the discovery of three new pulsars in the Globular Cluster (GC) NGC6517, namely NGC 6517 E, F, and G, made with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The spin periods of NGC 6517 E, F, and G are 7.60~ms, 24.89~ms, and 51.59~ms, respectively. Their dispersion measures are 183.29, 183.713, and 185.3~pc~cm$^{-3}$, respectively, all slightly larger than those of the previously known pulsars in this cluster. The spin period derivatives are at the level of 1$\times$10$^{-18}$~s~s$^{-1}$, which suggests these are recycled pulsars. In addition to the discovery of …
We present a reanalysis of the cumulative ACIS S Chandra data set pointed at the double AGNs of the NGC 6240 merging galaxy, focusing on the hard energy bands containing the hard spectral continuum (5.5-5.9 keV), the redshifted Fe I K alpha line (6.0-6.4 keV), and the redshifted Fe XXV line (6.4-6.7 keV). We have used to the full the Chandra telescope angular resolution, and we have modeled the Chandra PSF by comparing pre-flight calibration model to the data for the two bright AGNs. With two complementary approaches: (1) studying the residuals after PSF subtraction, and (2) producing reconstr…
We present a detailed timing and spectral study of an extremely variable narrow-line Seyfert~1 galaxy NGC 4748 using observations in the year 2017 and 2014 performed with AstroSat and XMM-Newton, respectively. Both observations show extremely variable soft and hard X-ray emission that are correlated with each other. In the 2014 data set, the source retains its general behaviour of "softer when brighter" while the 2017 observation exhibits a "harder when brighter" nature. Such changing behaviour is rare in AGNs and is usually observed in the black hole binary systems. The "harder when brighter"…
Discovery and Timing of the First Millisecond Pulsar in NGC 6316
University of Virginia（弗吉尼亚大学）；National Radio Astronomy Observatory（国家射电天文台）；George Mason University（乔治梅森大学）；Australia Telescope National Facility, CSIRO（CSIRO澳大利亚望远镜国家设施）；Western Sydney University（西悉尼大学）
We have used the Robert C. Byrd Green Bank Telescope to time nine previously known pulsars without published timing solutions in the globular clusters M62, NGC 6544, and NGC 6624. We have full timing solutions that measure the spin, astrometric, and (where applicable) binary parameters for six of these pulsars. The remaining three pulsars (reported here for the first time) were not detected enough to establish solutions. We also report our timing solutions for five pulsars with previously published solutions, and find good agreement with past authors, except for PSR J1701-3006B in M62. Gas in …
We present evidence for three spin-down glitches (or `anti-glitches') in the ultraluminous accreting X-ray pulsar NGC 300 ULX-1 in timing observations made with the Neutron Star Interior Composition Explorer (NICER). Our timing analysis reveals three sudden spin-down events of magnitudes $Δν= -23, -30,$ and $-43 \,μ$Hz (fractional amplitudes $Δν/ν= -4.4, -5.5,$ and $-7.7 \times 10^{-4}$). We determined fully phase-coherent timing solutions through the first two glitches, giving us high confidence in their detection, while the third candidate glitch is somewhat less secure. These are larger in …
We present results from a study of the non-nuclear discrete sources in a sample of three nearby spiral galaxies (NGC 4395, NGC 4736, and NGC 4258) based on XMM-Newton archival data supplemented with Chandra data for spectral and timing analyses. A total of 75 X-ray sources has been detected within the D25 regions of the target galaxies. The large collecting area of XMM-Newton makes the statistics sufficient to obtain spectral fitting for 16 (about 20%) of these sources. Compiling the extensive archival exposures available, we were able to obtain the detailed spectral shapes of diverse classes …
Using the MeerKAT radio telescope, a series of observations have been conducted to time the known pulsars and search for new pulsars in the globular cluster NGC 6440. As a result, two pulsars have been discovered, NGC 6440G and NGC 6440H, one of which is isolated and the other a non-eclipsing (at frequencies above 962 MHz) "Black Widow", with a very low mass companion (M$_{\rm c}$ > 0.006 M$_{\odot}$). It joins the other binary pulsars discovered so far in this cluster which all have low companion masses (M$_{\rm c}$ < 0.30 M$_{\odot}$). We present the results of long-term timing solutions obt…
Revisiting the 2021 Outburst of the BHC MAXI J1803-298 Using NICER, NuSTAR, and Insight-HXMT Data
South-Western Institute for Astronomy Research, Yunnan University（西南天体物理研究所，云南大学）；Indian Center for Space Physics（印度空间物理中心）；Institute of Astronomy, National Tsing Hua University（国立清华大学天文研究所）
Context. Obscuration events caused by outflowing clumps or streams of high column density, low ionisation gas, heavily absorbing the X-ray continuum, have been witnessed in a number of Seyfert galaxies. Aims. We report on the X-ray spectral-timing analysis of the December 2016 obscuration event in NGC 3783, aimed at probing variability of the X-ray obscurer on the shortest possible timescales. The main goals of this study are to obtain independent constraints on the density, and ultimately on the distance of the obscuring gas, as well as to characterise the impact of variable obscuration on th…
We investigated, using spectral-timing analysis, the characterization of highly ionized outflows in Seyfert galaxies, the so-called warm absorbers. Here, we present our results on the extensive ~ 600 ks of XMM-Newton archival observations of the bright and highly variable Seyfert 1 galaxy NGC 4051, whose spectrum has revealed a complex multicomponent wind. Making use of both RGS and EPIC-pn data, we performed a detailed analysis through a time-dependent photoionization code in combination with spectral and Fourier spectral-timing techniques. The source light curves and the warm absorber parame…
We present the results obtained from the analysis of high mass X-ray binary pulsar 4U 1909+07 using NuSTAR and Astrosat observations in 2015 and 2017 July, respectively. X-ray pulsations at $\approx$604 s are clearly detected in our study. Based on the long term spin-frequency evolution, the source is found to spun up in the last 17 years. We observed a strongly energy-dependent pulse profile that evolved from a complex broad structure in soft X-rays into a profile with a narrow emission peak followed by a plateau in energy ranges above 20 keV. This behaviour ensured a positive correlation bet…
The Stack Search Tests on FAST Data: Discovery of Six Faint Isolated Millisecond Pulsars in NGC 6517 and NGC 7078 (M15)
Beijing Normal University（北京师范大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Guizhou University（贵州大学）；University of Chinese Academy of Sciences（中国科学院大学）
We discuss preliminary results from a joint XMM-Newton and NuSTAR monitoring program on the active galactic nucleus NGC 4593, consisting of 5x20 ks observations, spaced by two days, performed in January 2015. The source is found to be variable, both in flux and spectral shape, on time scales as short as a few ks. The spectrum clearly softens when the source brightens. A simple timing analysis suggests the presence of a variable soft excess that correlates with the primary continuum.
We present a detailed timing and spectral analysis of the Be X-ray binary SWJ2000.6+3210 discovered by the BAT Galactic plane survey. Two Suzaku observations of the source made at six months interval, reveal pulsations at ~ 890s for both observations with a much weaker pulse fraction in the second one. Pulsations are clearly seen in the energy band of 0.3-10 keV of XIS for both observations and at high energies up to 40 keV for the second observation. The broad band X-ray spectrum is consistent with a powerlaw and high energy cutoff model along with a hot blackbody component. No change in spec…
(abridged) In this work we present the results of one year of upgraded Giant Metrewave Radio Telescope timing measurements of PSR~J0514$-$4002A, a 4.99-ms pulsar in a 18.8-day, eccentric ($e \, =\, 0.89$) orbit with a massive companion located in the globular cluster NGC~1851. Combining these data with earlier Green Bank Telescope data, we greatly improve the precision of the rate of advance of periastron, $\dotω \, = \, 0.0129592(16)\, °\, \rm yr^{-1}$ which, assuming the validity of general relativity, results in a much refined measurement of the total mass of the binary, $M_{\rm tot} \, = \…
We report the detection of a rapid occultation event in the nearby Seyfert galaxy NGC 6814, simultaneously captured in a transient light curve and spectral variability. The intensity and hardness ratio curves capture distinct ingress and egress periods that are symmetric in duration. Independent of the selected continuum model, the changes can be simply described by varying the fraction of the central engine that is covered by transiting obscuring gas. Together, the spectral and timing analyses self-consistently reveal the properties of the obscuring gas, its location to be in the broad line r…
From One to Two: A Second Binary Millisecond Pulsar in the Globular Cluster M92 (NGC 6341)
College of Physics, Guizhou University（贵州大学物理学院）；Guizhou Radio Astronomical Observatory, Guizhou University（贵州大学贵州射电天文观测站）；International Centre of Supernovae, Yunnan Key Laboratory（国际超新星中心云南重点实验室）；Institute for Frontier in Astronomy and Astrophysics & Faculty of Arts and Sciences, Beijing Normal University（北京师范大学前沿交叉科学研究院与文理学院）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；State Key Laboratory of Radio Astronomy and Technology, Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台射电天文与技术国家重点实验室）；Guizhou Vocational College of Foodstuff Engineering（贵州食品工程职业学院）
Pulsar timing arrays (PTAs) are placing increasingly stringent constraints on the strain amplitude of continuous gravitational waves emitted by supermassive black hole binaries on subparsec scales. In this paper, we incorporate independent information about the dynamical masses $M_{bh}$ of supermassive black holes in specific galaxies at known distances and use this additional information to further constrain whether or not those galaxies could host a detectable supermassive black hole binary. We estimate the strain amplitudes from individual binaries as a function of binary mass ratio for two…
The notion of source states characterizing the X-ray emission from black hole binaries has revealed to be a very useful tool to disentangle the complex spectral and aperiodic phenomenology displayed by those classes of accreting objects. We seek to use the same tools for Ultra-Luminous X-ray (ULX) sources. We analyzed the data from the longest observations obtained from the ULX source in NGC 5408 (NGC 5408 X-1) taken by XMM-Newton. We performed a study of the timing and spectral properties of the source. In accordance with previous studies on similar sources, the intrinsic energy spectra of th…
We report the first detection of a Fe K$_α$ line and soft X-ray lag in the ultraluminous X-ray source (ULX) NGC 7456 ULX-1. The XMM-Newton spectra show the presence of the 6.4 keV Fe line at 2.6$σ$ confidence and an upper limit on the FWHM of 32900 km s$^{-1}$. Assuming that the line arises by reflection from a Keplerian disk, it must originate beyond $85 r_{\rm g}$ from the compact object. As a result of Fourier timing analysis we found that the soft X-ray photons lag behind the hard X-ray photons with a $\sim$1300 s delay. The covariance spectra indicate that the hard spectral component is r…
Motivated by the newly discovery of a spin period 1.83\,ms pulsar J1835$-$3259B in the globular cluster (GC) NGC~6652, we analyze the gamma-ray data obtained with the Large Area Telescope (LAT) onboard {\it Fermi Gamma-ray Space Telescope (Fermi)} for the GC and detect the pulsations of this millisecond pulsar (MSP) at a 5.4$σ$ confidence level (the weighted H-test value is $\sim 41$). From timing analysis of the data, a pulse profile that is similar to the radio one is established. We thus consider that we have detected the \gr\ emission of the MSP, and discuss the implications. Based on our …
We present the variability analysis of a 100 ks XMM-Newton observation of the Seyfert 1.5 active galaxy NGC 3227. The observation found NGC 3227 in a period where its hard power-law component displayed remarkably little long-term variability. This lucky event allows us to observe clearly a soft spectral component undergoing a large-amplitude but slow flux variation. Using combined spectral and timing analysis we isolate two independent variable continuum components and characterize their behavior as a function of timescale. Rapid and coherent variations throughout the 0.2-10 keV band reveal a …
We present the results of X-ray spectral-timing analysis of a 90ks XMM-Newton observation of the nearby, broad line, early-type AGN NGC5273. The X-ray spectrum revealed the clear presence of a reflection component at high energies, with a clear signature of a narrow iron line at 6.4 keV, consistent with distant reflection. Applying a relativistic reflection model, we found only marginal evidence for a broader relativistic line component. However, cross-spectral analysis revealed that, between 4 and 6 $\times 10^{-4}$ Hz, the 5-8 keV band lagged the 2-3 keV band, implying reflection of the iron…
We present the broadband X-ray power spectral density function (PSD) of the X-ray-luminous Seyfert 1.2 NGC 7469, measured from Rossi X-ray Timing Explorer monitoring data and two XMM-Newton observations. We find significant evidence for a turnover in the 2-10 keV PSD at a temporal frequency of 2.0(+3.0,-0.8)e-6 Hz or 1.0(+3.0,-0.6)e-6 Hz, depending on the exact form of the break (sharply-broken or slowly-bending power-law, respectively). The ``surrogate'' Monte Carlo method of Press et al. (1992) was used to map out the probability distributions of PSD model parameters and obtain reliable unce…
We present a timing analysis of multiple XMM-Newton and NuSTAR observations of the ultra-luminous pulsar NGC 7793 P13 spread over its 65d variability period. We use the measured pulse periods to determine the orbital ephemeris, confirm a long orbital period with P_orb = 63.9 (+0.5,-0.6) d, and find an eccentricity of e <= 0.15. The orbital signature is imprinted on top of a secular spin-up, which seems to get faster as the source becomes brighter. We also analyse data from dense monitoring of the source with Swift and find an optical photometric period of 63.9 +/- 0.5 d and an X-ray flux perio…
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 report the discovery with XMM-Newton of correlated spectral and timing behavior in the ultraluminous X-ray source (ULX) NGC 5408 X-1. An ~100 ksec pointing with XMM/Newton obtained in January, 2008 reveals a strong 10 mHz QPO in the > 1 keV flux, as well as flat-topped, band limited noise breaking to a power law. The energy spectrum is again dominated by two components, a 0.16 keV thermal disk and a power-law with an index of ~2.5. These new measurements, combined with results from our previous January 2006 pointing in which we first detected QPOs, show for the first time in a ULX a pattern…
We report our findings on a new quasi-periodic oscillation (QPO) and a long period from the ultraluminous X-ray source (ULX) X-2 in nearby galaxy NGC 4736 based on the Chandra and XMM-Newton archival data. To examine the timing properties, power density spectra of the source have been obtained using Fast Fourier Transform. Also the spectral parameters of the source have been calculated by obtaining and fitting the energy spectra. Power density spectrum of this source reveals a QPO peak at $0.73_{-0.14}^{+0.16}$ mHz with an fractional rms variability of 16% using the Chandra data (in the year 2…
We report the discovery of a ~6-week quasi-periodic oscillation (QPO) in archival NGC 4945 data observed by the Rossi X-ray Timing Explorer (RXTE) satellite. QPOs are an important observable in accretion disks and have been studied extensively in both neutron star (NS) and black hole (BH) X-ray binaries (XRB). QPOs should be present in Active Galactic Nuclei (AGN) if galactic black holes and supermassive black holes (SMBH) are governed by a common set of physical processes. The search for QPOs in AGN has proven difficult because the timescales would be much longer, due to their higher mass. RX…
Recent X-ray observations have enabled the study of reverberation delays in AGN for the first time. All the detections so far are in sources with a strong soft excess, and the measured delay is between the hard (1-3 keV) direct continuum and the soft excess (0.5-1 keV), interpreted as the reflection continuum smeared by relativistic effects. There is however an inherent ambiguity in identifying and studying the details of the lines in the soft excess. Here we report the first detection of reverberation in the iron K band in any AGN. Using XMM-Newton observations of NGC 4151, we find delays of …
We present the results obtained from a detailed X-ray timing and spectral analysis of Seyfert 2 galaxy NGC 6300 by using observations with the {\it Suzaku}, {\it Chandra} and {\it NuSTAR} observatories between 2007 and 2016. We calculate variance, rms fractional variability of the source in different energy bands and find variabilities in various energy bands. Spectral properties of the source are studied by using various phenomenological and physical models. The properties of the Compton clouds, reflection, Fe K$α$ line emission and soft X-ray excess are studied in detail. Several physical pa…
We present the results obtained from timing and spectral studies of the highly obscured low luminosity active galactic nucleus NGC~4941 using data obtained from the {\it Nuclear Spectroscopic Telescope Array} and the {\it Neil Gehrels Swift} Observatories. We find similar variability in $3-10$~keV and $10-60$~keV energy ranges with fractional rms variability of $\sim$14\%. We investigate broad-band spectral properties of the source in 3-150 keV range, using data from {\it NuSTAR} and {\it Swift}/BAT, with phenomenological slab model and physically motivated {\tt mytorus} model. From the spectr…
The M101 galaxy contains the best-known example of an ultraluminous supersoft source (ULS), dominated by a thermal component at kT ~ 0.1 keV. The origin of the thermal component and the relation between ULSs and standard (broad-band spectrum) ultraluminous X-ray sources (ULXs) are still controversial. We re-examined the X-ray spectral and timing properties of the M101 ULS using archival Chandra and XMM-Newton observations. We show that the X-ray time-variability and spectral properties are inconsistent with standard disk emission. The characteristic radius R_{bb} of the thermal emitter varies …
The main idea of our research is to estimate the physical coalescence time of the double supermassive black hole (SMBH) system in the centre of NGC 6240 based on the X-ray observations from the Chandra space observatory. The spectra of the Northern and Southern nuclei were fitted by spectral models from Sherpa and both presented the narrow component of the Fe K$α$ emission line. It enabled us to apply the spectral model to these lines and to find relative offset $\approx0.02$ keV. The enclosed dynamical mass of the central region of NGC 6240 with radius 1 kpc was estimated $\approx 2.04\times …
