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

ABSTRACT We present the results regarding the analysis of the fast X-ray/infrared (IR) variability of the black hole transient MAXI J1535−571. The data studied in this work consist of two strictly simultaneous observations performed with XMM–Newton (X-rays: 0.7–10 keV), VLT/HAWK-I (Ks band, 2.2 μm) and VLT/VISIR (M and PAH2_2 bands, 4.85 and 11.88 μm, respectively). The cross-correlation function between the X-ray and near-IR light curves shows a strong asymmetric anticorrelation dip at positive lags. We detect a near-IR QPO (2.5σ) at 2.07 ± 0.09 Hz simultaneously with an X-ray QPO at approximately the same frequency (f0 = 2.25 ± 0.05). From the cross-spectral analysis, a lag consistent with zero was measured between the two oscillations. We also measure a significant correlation between the average near-IR and mid-IR fluxes during the second night, but find no correlation on short time-scales. We discuss these results in terms of the two main scenarios for fast IR variability (hot inflow and jet powered by internal shocks). In both cases, our preliminary modelling suggests the presence of a misalignment between the disc and jet.

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Energy and time-lag spectra of galactic black-hole X-ray sources in the low/hard state

Astronomy and Astrophysics ◽

10.1051/0004-6361:20030449 ◽

2003 ◽

Vol 403 (1) ◽

pp. L15-L18 ◽

Cited By ~ 33

Author(s):

P. Reig ◽

N. D. Kylafis ◽

D. Giannios

Keyword(s):

Black Hole ◽

Time Lag ◽

X Ray ◽

Galactic Black Hole ◽

Hard State

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The photon-index–time-lag correlation in black hole X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stx2683 ◽

2017 ◽

Vol 473 (4) ◽

pp. 4644-4652 ◽

Cited By ~ 7

Author(s):

Pablo Reig ◽

Nikolaos D. Kylafis ◽

Iossif E. Papadakis ◽

María Teresa Costado

Keyword(s):

Black Hole ◽

Time Lag ◽

X Ray ◽

Photon Index ◽

X Ray Binaries ◽

Time Lag Correlation

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Multiwavelength cross-correlation analysis of the simulated cosmic web

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1032 ◽

2020 ◽

Vol 494 (4) ◽

pp. 5603-5618 ◽

Cited By ~ 1

Author(s):

C Gheller ◽

F Vazza

Keyword(s):

Faraday Rotation ◽

Cross Correlation ◽

Future Generation ◽

Matter Distribution ◽

X Ray ◽

Galaxy Distribution ◽

Cross Correlation Analysis ◽

The Galaxy ◽

The Cross ◽

Diffuse Matter

ABSTRACT We used magnetohydrodynamical cosmological simulations to investigate the cross-correlation between different observables (i.e. X-ray emission, Sunyaev–Zeldovich (SZ) signal at 21 cm, H i temperature decrement, diffuse synchrotron emission, and Faraday Rotation) as a probe of the diffuse matter distribution in the cosmic web. We adopt a uniform and simplistic approach to produce synthetic observations at various wavelengths, and we compare the detection chances of different combinations of observables correlated with each other and with the underlying galaxy distribution in the volume. With presently available surveys of galaxies and existing instruments, the best chances to detect the diffuse gas in the cosmic web outside of haloes is by cross-correlating the distribution of galaxies with SZ observations. We also find that the cross-correlation between the galaxy network and the radio emission or the Faraday Rotation can already be used to limit the amplitude of extragalactic magnetic fields, well outside of the cluster volume usually explored by existing radio observations, and to probe the origin of cosmic magnetism with the future generation of radio surveys.

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Physical inference from the γ-ray, X-ray, and optical time variability of a large sample of Fermi blazars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2557 ◽

2019 ◽

Vol 490 (1) ◽

pp. 124-134

Author(s):

Anwesh Majumder ◽

Kaustav Mitra ◽

Ritaban Chatterjee ◽

C M Urry ◽

C D Bailyn ◽

...

Keyword(s):

Magnetic Field ◽

Cross Correlation ◽

Time Lag ◽

Monitoring Program ◽

Emission Region ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region ◽

Γ Ray

ABSTRACT We present cross-correlation studies of γ-ray (0.1–300 GeV), X-ray (0.2–10 keV), and optical (R band) variability of a sample of 26 blazars during 2008–2016. The light curves are from Fermi-LAT, Swift-XRT, and the Yale-SMARTS blazar monitoring program. We stack the discrete cross-correlation functions of the blazars such that the features that are consistently present in a large fraction of the sample become more prominent in the final result. We repeat the same analysis for two subgroups, namely, low synchrotron peaked (LSP) and high synchrotron peaked (HSP) blazars. We find that, on average, the variability at multiple bands is correlated, with a time lag consistent with zero in both subgroups. We describe this correlation with a leptonic model of non-thermal emission from blazar jets. By comparing the model results with those from the actual data, we find that the inter-band cross-correlations are consistent with an emission region of size 0.1 pc within the broad-line region for LSP blazars. We rule out large changes of magnetic field (>0.5 Gauss) across the emission region or small values of magnetic field (e.g., 0.2 Gauss) for this population. We also find that the observed variability of the HSP blazars can be explained if the emission region is much larger than the distance to the broad-line region from the central black hole.

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Cross-correlation of X-rays for 4U 1608–52

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312019850 ◽

2012 ◽

Vol 8 (S290) ◽

pp. 249-250

Author(s):

Y. J. Lei ◽

H. T. Zhang ◽

A. L. Luo ◽

Y. H. Zhao

Keyword(s):

Black Hole ◽

Cross Correlation ◽

Accretion Rate ◽

X Rays ◽

Galactic Black Hole ◽

The Cross ◽

Black Hole Candidates

AbstractWe study the cross-correlation between X-rays of different energies for the atoll-type source 4U 1608–52 with RXTE, and find the cross-correlation evolutes along the different branches. The anti-correlation is reported from the Galactic black hole candidates and Z-type luminous sources in their hard states. Our results are a little different from the Z-type sources. Here we provide the first evidence that a similar anti-correlated feature can also be found in atoll-type source, and it is not corresponding to the lowest accretion rate.

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X-ray dips and a complex UV/X-ray cross-correlation function in the black hole candidate MAXI J1820+070

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz089 ◽

2019 ◽

Vol 488 (1) ◽

pp. L18-L23 ◽

Cited By ~ 8

Author(s):

J J E Kajava ◽

S E Motta ◽

A Sanna ◽

A Veledina ◽

M Del Santo ◽

...

Keyword(s):

Black Hole ◽

Correlation Function ◽

Cross Correlation ◽

Timing Analysis ◽

Cross Correlation Function ◽

X Rays ◽

X Ray ◽

Black Hole Candidate ◽

Uv Emission ◽

Partial Covering

ABSTRACT MAXI J1820+070, a black hole candidate first detected in early 2018 March, was observed by XMM–Newton during the outburst rise. In this letter we report on the spectral and timing analysis of the XMM–Newton X-ray and UV data, as well as contemporaneous X-ray data from the Swift satellite. The X-ray spectrum is well described by a hard thermal Comptonization continuum. The XMM–Newton X-ray light curve shows a pronounced dipping interval, and spectral analysis indicates that it is caused by a moderately ionized partial covering absorber. The XMM–Newton/OM U-filter data do not reveal any signs of the 17 h orbital modulation that was seen later on during the outburst decay. The UV/X-ray cross-correlation function shows a complex shape, with a peak at positive lags of about 4 s and a precognition dip at negative lags, which is absent during the X-ray dipping episode. Such shape could arise if the UV emission comes partially from synchrotron self-Compton emission near the black hole, as well as from reprocessing of the X-rays in the colder accretion disc further out.

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Inclination effects on the X-ray emission of Galactic black-hole binaries

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935070 ◽

2019 ◽

Vol 625 ◽

pp. A90 ◽

Cited By ~ 4

Author(s):

Pablo Reig ◽

Nikolaos D. Kylafis

Keyword(s):

Black Hole ◽

Linear Regression Analysis ◽

Time Lag ◽

Light Curves ◽

Energy Spectra ◽

Time Lags ◽

X Ray ◽

Galactic Black Hole ◽

Photon Index ◽

Inclination Angles

Context. Galactic black-hole X-ray binaries (BHBs) emit a compact, optically thick, mildly relativistic radio jet when they are in hard and hard-intermediate states. In these states, BHBs exhibit a correlation between the time lag of hard with respect to softer photons and the photon index of the power law component that characterizes the X-ray spectral continuum above ∼10 keV. The correlation, however, shows large scatter. In recent years, several works have brought to light the importance of taking into account the inclination of the systems to understand the X-ray and radio phenomenology of BHBs. Aims. Our objective is to investigate the role that the inclination plays on the correlation between the time lag and photon index. Methods. We obtained RXTE energy spectra and light curves of a sample of BHBs with different inclination angles. We computed the photon index and the time lag between hard and soft photons and performed a correlation and linear regression analysis of the two variables. We also computed energy spectra and light curves of BHBs using the Monte Carlo technique that reproduces the process of Comptonization in the jet. We account for the inclination effects by recording the photons that escape from the jet at different angles. From the simulated light curves and spectra we obtained model-dependent photon index and time lags, which we compared with those obtained from the real data. Results. We find that the correlation between the time lag and photon index is tight in low-inclination systems and becomes weaker in high-inclination systems. The amplitude of the lags is also larger at low- and intermediate-inclination angles than at high inclination. We also find that the photon index and time lag, obtained from the simulated spectra and light curves, also follow different relationships for different inclination angle ranges. Our jet model reproduces the observations remarkably well. The same set of models that reproduces the correlation for the low-inclination systems, also accounts for the correlation for intermediate- and high-inclination systems fairly well. Conclusions. The large dispersion observed in the time lag – photon index correlation in BHBs can naturally be explained as an inclination effect. Comptonization in the jet explains the steeper dependence of the lags on the photon index in low- and intermediate-inclination systems than in high-inclination systems.

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Jets from Compact X-ray Sources

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310009142 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 266-267

Author(s):

Nick D. Kylafis

Keyword(s):

Black Holes ◽

Black Hole ◽

Neutron Star ◽

Time Lag ◽

Power Spectra ◽

Common Belief ◽

X Rays ◽

Radio Waves ◽

Characteristic Frequencies ◽

X Ray

AbstractJets have been observed from both neutron stars and black holes in binary X-ray sources. The neutron star jets are typically 30 times weaker than the black-hole ones. Thus, the second have been studied more extensively. Contrary to common belief, jets from compact X-ray sources are not simply “fireworks” that emit radio waves. I will demonstrate that they play a central role in the observed phenomena in both neutron star and black-hole systems. In particular, for black-hole jets, a simple jet model can explain the very stringent correlations that have been found between the power-law X-ray spectrum and a) the time lag between hard and soft X-rays and b) the characteristic frequencies observed in the power spectra. Up to now, no other model has even attempted to explain these correlations. I will present the weaknesses of the model and the improvements that need to be done to it.

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