scholarly journals Identifying the radiative components responsible for quasi-periodic oscillations of black hole systems

2020 ◽  
Vol 498 (2) ◽  
pp. 2757-2765
Author(s):  
Akash Garg ◽  
Ranjeev Misra ◽  
Somasri Sen
Keyword(s):  
Black Hole ◽  
Spectral Component ◽  
Temporal Variations ◽  
Time Lags ◽  
Temporal Data ◽  
Periodic Oscillations ◽  
Temporal Behaviour ◽  
Galactic Black Hole ◽  
Best Fitting ◽  
Energy Dependent

ABSTRACT While the dynamical origin of the variability observed in Galactic black hole systems, such as quasi-periodic oscillations (QPOs), is still a matter of debate, insight into the radiative components responsible for such behaviour can be obtained by studying their energy-dependent temporal behaviour. In particular, one needs to ascertain which variations of the parameters of the best-fitting time-averaged spectral components reproduce the observed energy-dependent fractional rms and time-lags. However, to obtain meaningful interpretation, the standard spectral component parameters have to be recast to physically relevant ones. Then, the energy-dependent temporal variations that their fluctuations will cause, needs to be predicted and compared with observations. In this work, we describe a generic method to do this and apply the technique to the ∼3–4 Hz QPOs observed in the black hole system GRS 1915+105 as observed by AstroSat where the time-averaged spectra can be represented by emission from a truncated disc and hot thermal Comptonizing coronae in the inner regions. We find that the QPOs and their harmonic can be explained in terms of correlated local accretion rate variations in the disc, the truncated disc radius, the optical depth and the heating rate of the coronae with time-delays between them. We highlight the potential of such techniques to unravel the radiative process responsible for variability using high-quality spectral and temporal data from AstroSat and NICER.

scholarly journals Comptonisation and Time-lags in Multi-temperature Plasmas Surrounding Compact Objects

2000 ◽  
Vol 17 (1) ◽  
pp. 48-55
Author(s):  
Jason Cullen
Keyword(s):  
Black Hole ◽  
Gamma Ray ◽  
Time Lag ◽  
Compact Objects ◽  
Time Lags ◽  
Monte Carlo Code ◽  
Energy Bands ◽  
Temporal Behaviour ◽  
Galactic Black Hole ◽  
Black Hole Candidates

AbstractThis paper investigates a recent model proposed by Moskalenko, Collmar & Schönfelder (1998) for the plasma surrounding galactic black hole candidates. Using a linear Monte Carlo code, the spectral and temporal behaviour of the model is found for the case where the plasma geometry consists of a hot shell surrounding a cooler spherical core. The spectrum produced by this model at X-ray and gamma-ray energies is obtained numerically. Also found for the first time in this geometry are the photon time-lags between two energy bands due to rapid aperiodic variability. It is argued that the time-lag information may be able to determine whether this particular geometry is a realistic model for the material surrounding galactic black hole candidates.

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

2019 ◽  
Vol 625 ◽  
pp. A90 ◽  
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.

scholarly journals Anticorrelated Hard X‐Ray Time Lags in Galactic Black Hole Sources

2007 ◽  
Vol 661 (2) ◽  
pp. 1055-1063 ◽  
Author(s):  
K. Sriram ◽  
V. K. Agrawal ◽  
Jayant K. Pendharkar ◽  
A. R. Rao
Keyword(s):  
Black Hole ◽  
Time Lags ◽  
X Ray ◽  
Galactic Black Hole

scholarly journals X-ray variability of accreting black hole systems: propagating-fluctuation scenario

2006 ◽  
Vol 2 (S238) ◽  
pp. 319-320
Author(s):  
Patricia Arévalo ◽  
Phil Uttley ◽  
Ian McHardy
Keyword(s):  
Black Hole ◽  
Light Curves ◽  
Time Lags ◽  
Spectral Densities ◽  
Energy Bands ◽  
X Ray ◽  
Fundamental Properties ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Energy Dependent

AbstractPropagating fluctuation models can reproduce fundamental properties of the variability observed in the X-ray light curves of accreting black hole systems. We explore this type of model and show how extended emitting regions introduce at the same time energy dependent power spectral densities (PSD) and time lags between different energy bands.

On the properties of dissipative shocks in the relativistic accretion flows

2020 ◽  
Vol 497 (2) ◽  
pp. 2119-2132
Author(s):  
Soumen Mondal ◽  
Prasad Basu
Keyword(s):  
Black Hole ◽  
Temporal Variations ◽  
Maximum Energy ◽  
Radiative Loss ◽  
Time Lags ◽  
X Rays ◽  
Pressure Drops ◽  
Accretion Flows ◽  
Flow Parameters ◽  
Post Shock

ABSTRACT In this work, we study the properties of dissipative shocks for fully relativistic accretion flows around spinning black holes. In an accretion flow harbouring a dissipative shock (formally known as radiative shock), a significant portion of the thermal energy may get released from the post-shock corona. A stellar-mass black hole may therefore emit hard X-rays from the inner edge of the disc. If the bulk energy loss is significant, post-shock pressure drops, and shock moves forward towards the black hole compressing the size of the post-shock corona, resulting an enhancement of the corona temperature and compression ratio. The dynamical properties of the radiative shocks are therefore systematically investigated to understand accurately the radiative loss processes, temporal variations, and the spectral properties. We notice that the range of flow parameters (e.g. energy and angular momentum) responsible for the formation of ‘shocks in accretion (SA)’ is identical for both the cases of standing and dissipative shocks. The spin of the black hole enhances the dissipation further. We estimate the maximum energy release, which is observed close to $100{{\ \rm per\ cent}}$ in the extreme cases. This could be useful in explaining various observed phenomena namely the formation and the systematic evolution of quasi-periodic oscillations, and the time lags in between hard and soft X-ray photons (e.g. XTE J1550−564, GRO J1655−40, etc.) during their outbursts.

scholarly journals Epicyclic Oscillations around Simpson–Visser Regular Black Holes and Wormholes

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 279
Author(s):  
Zdeněk Stuchlík ◽  
Jaroslav Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Observational Data ◽  
High Frequency ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Periodic Oscillations ◽  
High Length ◽  
Circular Geodesic

We study epicyclic oscillatory motion along circular geodesics of the Simpson–Visser meta-geometry describing in a unique way regular black-bounce black holes and reflection-symmetric wormholes by using a length parameter l. We give the frequencies of the orbital and epicyclic motion in a Keplerian disc with inner edge at the innermost circular geodesic located above the black hole outer horizon or on the our side of the wormhole. We use these frequencies in the epicyclic resonance version of the so-called geodesic models of high-frequency quasi-periodic oscillations (HF QPOs) observed in microquasars and around supermassive black holes in active galactic nuclei to test the ability of this meta-geometry to improve the fitting of HF QPOs observational data from the surrounding of supermassive black holes. We demonstrate that this is really possible for wormholes with sufficiently high length parameter l.

scholarly journals Properties of Faint X-ray Activity of XTE J1908+094 in 2019

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 25
Author(s):  
Debjit Chatterjee ◽  
Arghajit Jana ◽  
Kaushik Chatterjee ◽  
Riya Bhowmick ◽  
Sujoy Kumar Nath ◽  
...  
Keyword(s):  
Black Hole ◽  
Temporal Analysis ◽  
Power Density Spectrum ◽  
Periodic Oscillations ◽  
Telescope Array ◽  
Density Spectrum ◽  
X Ray ◽  
Black Hole Candidate ◽  
Short Period ◽  
Spectral State

We study the properties of the faint X-ray activity of Galactic transient black hole candidate XTE J1908+094 during its 2019 outburst. Here, we report the results of detailed spectral and temporal analysis during this outburst using observations from Nuclear Spectroscopic Telescope Array (NuSTAR). We have not observed any quasi-periodic-oscillations (QPOs) in the power density spectrum (PDS). The spectral study suggests that the source remained in the softer (more precisely, in the soft–intermediate) spectral state during this short period of X-ray activity. We notice a faint but broad Fe Kα emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be 6.5−0.7+0.5M⊙, with 90% confidence.

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