The chaotic long-term X-ray variability of 4U 1705–44

Phillipson, Rebecca; Boyd, Patricia T.; Smale, A. P.

doi:10.1093/mnras/sty970

Cited by 17 publications

(10 citation statements)

References 78 publications

(149 reference statements)

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“…Therefore, though the full range of this 'flip-flop' behaviour is still poorly defined, the flaring in MAXI J1820+070 agrees with the spectral and temporal properties of this class. Phillipson et al (2018) note the similarity of this behaviour to the Duffing oscillator, a double welled (hence two typical flux states) non-linear (hence chaotic) oscillator. However, they do not determine the properties of the binary system which correspond to the variables in the Duffing equation: there…”

Section: Discussionsupporting

confidence: 54%

MAXI J1820+070 with NuSTAR – II. Flaring during the hard to soft state transition with a long soft lag

Buisson

Fabian

Gandhi

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We continue the analysis of NuSTAR data from the recent discovery outburst of MAXI J1820+070 (optical counterpart ASASSN-18ey), focussing on an observation including unusual flaring behaviour during the hard to soft state transition, which is a short phase of outbursts and so comparatively rarely observed. Two plateaus in flux are separated by a variable interval lasting ∼10 ks, which shows dipping then flaring stages. The variability is strongest (with fractional variability up to $F_{\rm Var}\sim 10\%$) at high energies and reduces as the contribution from disc emission becomes stronger. Flux-resolved spectra show that the variability is primarily due to the power law flux changing. We also find a long soft lag of the thermal behind the power law emission, which is $20_{-1.2}^{+1.6}$ s during the flaring phase. The lag during the dipping stage has a different lag-energy spectrum, which may be due to a wave passing outwards through the disc. Time resolved spectral fitting suggests that the lag during the flaring stage may be due to the disc re-filling after being disrupted to produce the power law flare, perhaps related to the system settling after the jet ejection which occurred around 1 day before. The timescales of these phenomena imply a low viscosity parameter, α ∼ 10−3, for the inner region of the disc.

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Section: Discussionsupporting

confidence: 54%

MAXI J1820+070 with NuSTAR – II. Flaring during the hard to soft state transition with a long soft lag

Buisson

Fabian

Gandhi

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…It is also well known that a damped, forced, non-linear oscillator, also known as a Duffing Oscillator (Duffing 1918), is able to produce quasiperiodic oscillations. [See e.g Phillipson et al (2018) for an application of the Duffing oscillator to longer timescale variability in an X-ray binary.] We find that an increase in the driving frequency of the oscillator, results in the bicoherence pattern of the resulting lightcurves evolving in a manner similar to that shown in Fig.…”

Section: Evolution During State Transitionmentioning

confidence: 99%

Nonlinear Variability of Quasi-Periodic Oscillations in GX 339-4

Arur

Maccarone

2019

Monthly Notices of the Royal Astronomical Society

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We examine the nonlinear variability of quasi-periodic oscillations (QPOs) using the bicoherence, a measure of phase coupling at different Fourier frequencies. We analyse several observations of RXTE/PCA archival data of the black hole binary GX 339-4 which show QPOs. In the type C QPOs, we confirm the presence of the 'hypotenuse' pattern where there is nonlinear coupling between low frequencies that sum to the QPO frequency as well as the 'web' pattern where in addition to the hypotenuse, nonlinear coupling between the QPO frequency and the broadband noise is present. We find that type B QPOs show a previously unknown pattern. We also show that the bicoherence pattern changes gradually from 'web' to 'hypotenuse' as the source moves from a hard intermediate state to a soft intermediate state. Additionally, we reconstruct the QPO waveforms from six observations using the biphase. Finally, we present a scenario by which a moderate increase in the optical depth of the hard X-ray emission region can explain the changes in the non-linearity seen during this transition.Recently, attempts have been made to understand the non-linear variability in X-ray binaries. Nonlinearity has been shown by presence of a linear rms-flux relation (Uttley & McHardy 2001) and has also been seen in the hard state of Cygnus X-1 using the bispectrum and bicoherence,

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“…X-ray binaries exhibit broad-band PSDs (Bayless et al 2011), whose shape can be constrained with several techniques, complementing each other, including modeling the LCs with Gaussian stochastic processes. Moreover, chaotic modulation is also a considered possibility (Suková et al 2016;Mannattil et al 2016;Phillipson et al 2018) that further validates the use of nonstandard, in particular nonlinear, tools of time series analysis.…”

Section: Possible Applicationsmentioning

confidence: 70%

A comprehensive power spectral density analysis of astronomical time series I: the Fermi-LAT gamma-ray light curves of selected blazars

Tarnopolski,

Żywucka,

Marchenko

et al. 2020

Preprint

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We present the results of the Fermi -LAT 10-years-long light curves (LCs) modeling of selected blazars: six flat spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs), examined in 7-, 10-, and 14-day binning. The LCs and power spectral densities (PSDs) were investigated with various methods: Fourier transform, Lomb-Scargle periodogram (LSP), wavelet scalogram, autoregressive moving average (ARMA) process, continuous-time ARMA (CARMA), Hurst exponent (H), and the A − T plane. First, with extensive simulations we showed that parametric modeling returns unreliable parameters, with a high dispersion for different realizations of the same stochastic model. Hence any such analysis should be supported with Monte Carlo simulations. For our blazar sample, we find that the power law indices β calculated from the Fourier and LSP modeling mostly fall in the range 1 β 2. Using the wavelet scalograms, we confirm a quasi-periodic oscillation (QPO) in PKS 2155−304 at a 3σ significance level, but do not detect any QPOs in other objects. The ARMA fits reached higher orders for 7-day binned LCs and lower orders for 10-and 14-days binned LCs for the majority of blazars, suggesting there might exist a characteristic timescale for the perturbations in the jet and/or accretion disk to die out. ARMA and CARMA modeling revealed breaks in their PSDs at timescales of few hundred days. The estimation of H was performed with several methods. We find that most blazars exhibit H > 0.5, indicating long-term memory. Finally, the FSRQ and BL Lac subclasses are clearly separated in the A − T plane.

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The chaotic long-term X-ray variability of 4U 1705–44

Cited by 17 publications

References 78 publications

MAXI J1820+070 with NuSTAR – II. Flaring during the hard to soft state transition with a long soft lag

MAXI J1820+070 with NuSTAR – II. Flaring during the hard to soft state transition with a long soft lag

Nonlinear Variability of Quasi-Periodic Oscillations in GX 339-4

A comprehensive power spectral density analysis of astronomical time series I: the Fermi-LAT gamma-ray light curves of selected blazars

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