scholarly journals X-ray reverberation models of the disc wind in ultraluminous X-ray source NGC 5408 X−1

2021 ◽  
Vol 507 (4) ◽  
pp. 6094-6107
Author(s):  
W Luangtip ◽  
P Chainakun ◽  
S Loekkesee ◽  
C Deesamer ◽  
T Ngonsamrong ◽  
...  
Keyword(s):  
Time Lag ◽  
Accretion Disc ◽  
Mapping Technique ◽  
Photon Scattering ◽  
Spectral Variability ◽  
Clear Trend ◽  
Supercritical Regime ◽  
X Ray ◽  
Reverberation Mapping ◽  
Single Versus

ABSTRACT Majority of ultraluminous X-ray sources (ULXs) are believed to be super-Eddington objects, providing a nearby prototype for studying an accretion in supercritical regime. In this work, we present the study of time-lag spectra of the ULX NGC 5408 X−1 using a reverberation mapping technique. The time-lag data were binned using two different methods: time-averaged-based and luminosity-based spectral bins. These spectra were fitted using two proposed geometric models: single and multiple photon scattering models. While both models similarly assume that a fraction of hard photons emitted from inner accretion disc could be downscattered with the super-Eddington outflowing wind becoming lagged, soft photons, they are different by the number that the hard photons scattering with the wind, i.e. single versus multiple times. In case of an averaged spectrum, both models consistently constrained the mass of ULX in the range of  ∼80–500 M⊙. However, for the modelling results from the luminosity-based spectra, the confidence interval of the BH mass is significantly improved and is constrained to the range of  ∼75–90 M⊙. In addition, the models suggest that the wind geometry is extended in which the photons could downscatter with the wind at the distance of ∼104–10$^{6}\, r_{\rm g}$. The results also suggest the variability of the lag spectra as a function of ULX luminosity, but the clear trend of changing accretion disc geometry with the spectral variability is not observed.

scholarly journals Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469

2020 ◽  
Vol 494 (3) ◽  
pp. 4057-4068
Author(s):  
Mayukh Pahari ◽  
I M McHardy ◽  
Federico Vincentelli ◽  
Edward Cackett ◽  
Bradley M Peterson ◽  
...  
Keyword(s):  
Light Curve ◽  
Time Lag ◽  
Accretion Disc ◽  
Light Curves ◽  
X Rays ◽  
X Ray ◽  
Cross Correlation Analysis ◽  
Optical Continuum ◽  
Delay Prediction ◽  
Ngc 7469

ABSTRACT Using a month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220–1970 Å, we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469. Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Å by 3.49 ± 0.22 d, which is possibly caused by either propagating fluctuation or variable Comptonization. However, if variations slower than 5 d are removed from the X-ray light curve, the UV variations then lag behind the X-ray variations by 0.37 ± 0.14 d, consistent with reprocessing of the X-rays by a surrounding accretion disc. A very similar reverberation delay is observed between Swift/XRT X-ray and Swift/UVOT UVW2, U light curves. Continuum light curves extracted from the Swift/GRISM spectra show delays with respect to X-rays consistent with reverberation. Separating the UV continuum variations faster and slower than 5 d, the slow variations at 1825 Å lag those at 1315 Å by 0.29 ± 0.06 d, while the fast variations are coincident (0.04 ± 0.12 d). The UV/optical continuum reverberation lag from IUE, Swift, and other optical telescopes at different wavelengths are consistent with the relationship: τ ∝ λ4/3, predicted for the standard accretion disc theory while the best-fitting X-ray delay from RXTE and Swift/XRT shows a negative X-ray offset of ∼0.38 d from the standard disc delay prediction.

scholarly journals The unusual broad-band X-ray spectral variability of NGC 1313 X-1 seen with XMM–Newton, Chandra, and NuSTAR

2020 ◽  
Vol 494 (4) ◽  
pp. 6012-6029 ◽  
Author(s):  
D J Walton ◽  
C Pinto ◽  
M Nowak ◽  
M Bachetti ◽  
R Sathyaprakash ◽  
...  
Keyword(s):  
Black Hole ◽  
Broad Band ◽  
High Energy ◽  
Accretion Disc ◽  
Continuum Emission ◽  
Spectral Variability ◽  
Temperature Behaviour ◽  
Temperature Relation ◽  
X Ray ◽  
Constant Area

ABSTRACT We present results from the major coordinated X-ray observing programme on the ULX NGC 1313 X-1 performed in 2017, combining XMM–Newton, Chandra, and NuSTAR, focusing on the evolution of the broad-band (∼0.3–30.0 keV) continuum emission. Clear and unusual spectral variability is observed, but this is markedly suppressed above ∼10–15 keV, qualitatively similar to the ULX Holmberg IX X-1. We model the multi-epoch data with two-component accretion disc models designed to approximate super-Eddington accretion, allowing for both a black hole and a neutron star accretor. With regards to the hotter disc component, the data trace out two distinct tracks in the luminosity–temperature plane, with larger emitting radii and lower temperatures seen at higher observed fluxes. Despite this apparent anticorrelation, each of these tracks individually shows a positive luminosity–temperature relation. Both are broadly consistent with L ∝ T4, as expected for blackbody emission with a constant area, and also with L ∝ T2, as may be expected for an advection-dominated disc around a black hole. We consider a variety of possibilities for this unusual behaviour. Scenarios in which the innermost flow is suddenly blocked from view by outer regions of the super-Eddington disc/wind can explain the luminosity–temperature behaviour, but are difficult to reconcile with the lack of strong variability at higher energies, assuming this emission arises from the most compact regions. Instead, we may be seeing evidence for further radial stratification of the accretion flow than is included in the simple models considered, with a combination of winds and advection resulting in the suppressed high-energy variability.

scholarly journals The nature of the soft excess and spectral variability in the Seyfert 1 galaxy Zw 229.015

2019 ◽  
Vol 488 (4) ◽  
pp. 4831-4842 ◽  
Author(s):  
S Tripathi ◽  
S G H Waddell ◽  
L C Gallo ◽  
W F Welsh ◽  
C-Y Chiang
Keyword(s):  
Power Law ◽  
Temporal Variability ◽  
Accretion Disc ◽  
Spectral Variability ◽  
Systematic Analysis ◽  
X Ray ◽  
Soft State ◽  
Hard State ◽  
Partial Covering ◽  
Spectral States

ABSTRACT We have carried out a systematic analysis of the nearby (z = 0.0279) active galaxy Zw 229.015 using multi-epoch, multi-instrument, and deep pointed observations with XMM–Newton, Suzaku, Swift,and NuSTAR. Spectral and temporal variability are examined in detail on both the long (weeks-to-years) and short (hours) time-scales. A deep Suzaku observation of the source shows two distinct spectral states; a bright-soft state and a dim-hard state in which changes in the power-law component account for the differences. Partial covering, blurred reflection, and soft Comptonization models describe the X-ray spectra comparably well, but the smooth, rather featureless, spectrum may be favouring the soft Comptonization scenario. Moreover, independent of the spectral model, the observed spectral variability is ascribed to the changes in the power-law continuum only and do not require changes in the properties of the absorber or blurred reflector incorporated in the other scenarios. The multi-epoch observations between 2009 and 2018 can be described in similar fashion. This could be understood if the primary emission is originating at a large distance from a standard accretion disc or if the disc is optically thin and geometrically thick as recently proposed for Zw 229.015. Our investigation shows that Zw 229.015 behaves similar to sources like Akn 120 and Mrk 530 that exhibit a strong soft excess, but weak Compton hump and Fe Kα emission.

scholarly journals Returning radiation in strong gravity around black holes: reverberation from the accretion disc

2020 ◽  
Vol 498 (3) ◽  
pp. 3302-3319
Author(s):  
D R Wilkins ◽  
J A García ◽  
T Dauser ◽  
A C Fabian
Keyword(s):  
Black Holes ◽  
Strong Field ◽  
Time Lag ◽  
Accretion Disc ◽  
X Rays ◽  
X Ray ◽  
Gravitational Fields ◽  
Strong Gravity ◽  
General Relativistic ◽  
Strong Gravitational Fields

ABSTRACT We study reflected X-ray emission that returns to the accretion disc in the strong gravitational fields around black holes using General Relativistic ray-tracing and radiative transfer calculations. Reflected X-rays that are produced when the inner regions of the disc are illuminated by the corona are subject to strong gravitational light bending, causing up to 47 per cent of the reflected emission to be returned to the disc around a rapidly spinning black hole, depending upon the scale height of the corona. The iron Kα line is enhanced relative to the continuum by 25 per cent, and the Compton hump by up to a factor of 3. Additional light traveltime between primary and secondary reflections increases the reverberation time lag measured in the iron K band by 49 per cent, while the soft X-ray lag is increased by 25 per cent and the Compton hump response time is increased by 60 per cent. Measured samples of X-ray reverberation lags are shown to be consistent with X-rays returning to the accretion disc in strong gravity. Understanding the effects of returning radiation is important in interpreting reverberation observations to probe black holes. Reflected X-rays returning to the disc can be uniquely identified by blueshifted returning iron K line photons that are Compton scattered from the inner disc, producing excess, delayed emission in the 3.5–4.5 keV energy range that will be detectable with forthcoming X-ray observatories, representing a unique test of General Relativity in the strong field limit.

scholarly journals Dust reverberation mapping of type 2 AGN NGC 2110 realized with X-ray and 3–5 μm IR monitoring

2020 ◽  
Vol 495 (3) ◽  
pp. 2921-2929
Author(s):  
Hirofumi Noda ◽  
Taiki Kawamuro ◽  
Mitsuru Kokubo ◽  
Takeo Minezaki
Keyword(s):  
Time Lag ◽  
Galactic Nuclei ◽  
Light Curves ◽  
Time Lags ◽  
X Ray ◽  
Reverberation Mapping ◽  
Promising Tool ◽  
Best Fitting

ABSTRACT The dust reverberation mapping is one of powerful methods to investigate the structure of the dusty tori in active galactic nuclei (AGNs), and it has been performed on more than a hundred type 1 AGNs. However, no clear results have been reported on type 2 AGNs because their strong optical/UV extinction completely hides their accretion disc emission. Here, we focus on an X-ray-bright type 2 AGN, NGC 2110, and utilize 2–20 keV X-ray variation monitored by MAXI to trace disc emission, instead of optical/UV variation. Comparing it with light curves in the WISE infrared (IR) W1 band ($\lambda =3.4~\mu$m) and W2 band ($\lambda =4.6~\mu$m) with cross-correlation analyses, we found candidates of the dust reverberation time lag at ∼60, ∼130, and ∼1250 d between the X-ray flux variation and those of the IR bands. By examining the best-fitting X-ray and IR light curves with the derived time lags, we found that the time lag of ∼130 d is most favoured. With this time lag, the relation between the time lag and luminosity of NGC 2110 is consistent with those in type 1 AGNs, suggesting that the dust reverberation in NGC 2110 mainly originates in hot dust in the torus innermost region, the same as in type 1 AGNs. As demonstrated by the present study, X-ray and IR simultaneous monitoring can be a promising tool to perform the dust reverberation mapping on type 2 AGNs.

scholarly journals Intensive disc-reverberation mapping of Fairall 9: first year of Swift and LCO monitoring

2020 ◽  
Vol 498 (4) ◽  
pp. 5399-5416
Author(s):  
J V Hernández Santisteban ◽  
R Edelson ◽  
K Horne ◽  
J M Gelbord ◽  
A J Barth ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Accretion Disc ◽  
Spectral Energy ◽  
First Year ◽  
X Rays ◽  
X Ray ◽  
Reverberation Mapping ◽  
Line Region ◽  
Continuum Contribution

ABSTRACT We present results of time-series analysis of the first year of the Fairall 9 intensive disc-reverberation campaign. We used Swift and the Las Cumbres Observatory global telescope network to continuously monitor Fairall 9 from X-rays to near-infrared at a daily to subdaily cadence. The cross-correlation function between bands provides evidence for a lag spectrum consistent with the τ ∝ λ4/3 scaling expected for an optically thick, geometrically thin blackbody accretion disc. Decomposing the flux into constant and variable components, the variable component’s spectral energy distribution is slightly steeper than the standard accretion disc prediction. We find evidence at the Balmer edge in both the lag and flux spectra for an additional bound-free continuum contribution that may arise from reprocessing in the broad-line region. The inferred driving light curve suggests two distinct components, a rapidly variable (<4 d) component arising from X-ray reprocessing, and a more slowly varying (>100 d) component with an opposite lag to the reverberation signal.

Epitaxial Ni nanoparticles on CaF2(001), (110) and (111) surfaces studied by three-dimensional RHEED, GIXD and GISAXS reciprocal-space mapping techniques

2017 ◽  
Vol 50 (3) ◽  
pp. 830-839 ◽  
Author(s):  
S. M. Suturin ◽  
V. V. Fedorov ◽  
A. M. Korovin ◽  
N. S. Sokolov ◽  
A. V. Nashchekin ◽  
...  
Keyword(s):  
Lattice Structure ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
High Energy ◽  
Reciprocal Space ◽  
Mapping Technique ◽  
Face Centered Cubic ◽  
X Ray ◽  
Cubic Lattice ◽  
Face Centered

The development of growth techniques aimed at the fabrication of nanoscale heterostructures with layers of ferroic 3dmetals on semiconductor substrates is very important for their potential usage in magnetic media recording applications. A structural study is presented of single-crystal nickel island ensembles grown epitaxially on top of CaF2/Si insulator-on-semiconductor heteroepitaxial substrates with (111), (110) and (001) fluorite surface orientations. The CaF2buffer layer in the studied multilayer system prevents the formation of nickel silicide, guides the nucleation of nickel islands and serves as an insulating layer in a potential tunneling spin injection device. The present study, employing both direct-space and reciprocal-space techniques, is a continuation of earlier research on ferromagnetic 3dtransition metals grown epitaxially on non-magnetic and magnetically ordered fluorides. It is demonstrated that arrays of stand-alone faceted nickel islands with a face-centered cubic lattice can be grown controllably on CaF2surfaces of (111), (110) and (001) orientations. The proposed two-stage nickel growth technique employs deposition of a thin seeding layer at low temperature followed by formation of the islands at high temperature. The application of an advanced three-dimensional mapping technique exploiting reflection high-energy electron diffraction (RHEED) has proved that the nickel islands tend to inherit the lattice orientation of the underlying fluorite layer, though they exhibit a certain amount of {111} twinning. As shown by scanning electron microscopy, grazing-incidence X-ray diffraction (GIXD) and grazing-incidence small-angle X-ray scattering (GISAXS), the islands are of similar shape, being faceted with {111} and {100} planes. The results obtained are compared with those from earlier studies of Co/CaF2epitaxial nanoparticles, with special attention paid to the peculiarities related to the differences in lattice structure of the deposited metals: the dual-phase hexagonal close-packed/face-centered cubic lattice structure of cobalt as opposed to the single-phase face-centered cubic lattice structure of nickel.

scholarly journals The nature of X-ray spectral variability in SWIFT J2127.4+5654

2018 ◽  
Vol 480 (3) ◽  
pp. 3412-3423
Author(s):  
E S Kammoun ◽  
I E Papadakis
Keyword(s):  
Spectral Variability ◽  
X Ray

scholarly journals A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

2017 ◽  
Vol 362 (7) ◽  
Author(s):  
Songpeng Pei ◽  
Guoqiang Ding ◽  
Zhibing Li ◽  
Yajuan Lei ◽  
Rai Yuen ◽  
...  
Keyword(s):  
Black Hole ◽  
Cross Correlation ◽  
Time Lag ◽  
X Ray ◽  
The Cross

scholarly journals Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

2017 ◽  
Vol 846 (1) ◽  
pp. 55 ◽  
Author(s):  
S. Mathur ◽  
A. Gupta ◽  
K. Page ◽  
R. W. Pogge ◽  
Y. Krongold ◽  
...  
Keyword(s):  
Space Telescope ◽  
X Ray ◽  
Reverberation Mapping ◽  
Ngc 5548
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