Modeling black hole x-ray power spectra

1994 ◽  
Author(s):  
Michael A. Nowak
Keyword(s):  
Black Hole ◽  
Power Spectra ◽  
X Ray

scholarly journals A minimal timescale for the continuum in 4U 1608-52 and Aql X-1

2021 ◽  
Vol 502 (1) ◽  
pp. L72-L78
Author(s):  
K Mohamed ◽  
E Sonbas ◽  
K S Dhuga ◽  
E Göğüş ◽  
A Tuncer ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Power Spectra ◽  
Light Curves ◽  
State Transitions ◽  
Strong Positive Correlation ◽  
Present Evidence ◽  
X Ray ◽  
X Ray Binaries ◽  
The Continuum

ABSTRACT Similar to black hole X-ray binary transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries. Using a method based on wavelets and light curves constructed from archival Rossi X-ray Timing Explorer observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.

scholarly journals A minimal time-scale for the spectral states of GX 339−4

2020 ◽  
Vol 499 (2) ◽  
pp. 2513-2522
Author(s):  
E Sonbas ◽  
K Mohamed ◽  
K S Dhuga ◽  
A Tuncer ◽  
E Göğüş
Keyword(s):  
Black Hole ◽  
Root Mean Square ◽  
Time Scale ◽  
Power Spectra ◽  
Mean Square ◽  
X Ray ◽  
Minimal Time ◽  
Power Spectral ◽  
Power Spectral Densities ◽  
Spectral States

ABSTRACT Black hole transients are known to undergo spectral transitions that form q-shaped tracks on a hardness intensity diagram. In this work, we use the archival Rossi X-ray Timing Explorer data to extract a characteristic minimal time-scale for the spectral states in GX 339−4 for the 2002–2003 and 2010 outbursts. We use the extracted time-scale to construct an intensity variability diagram for each outburst. This new diagram is comparable to the traditional hardness intensity diagram and offers the potential for probing the underlying dynamics associated with the evolution of the relevant emission regions in black hole transients. We confirm this possibility by connecting the minimal time-scale with the inner disc radius, Rin (estimated from spectral fits), and demonstrate a positive correlation between these variables as the system evolves through its spectral transitions. Furthermore, we probe the relation between the minimal time-scale and the break frequencies extracted from the power spectral densities. Lastly, we examine a possible link between the extracted time-scale and a traditional measure of variability, i.e. the root mean square, determined directly from the power spectra.

scholarly journals Looking for the underlying cause of black hole X-ray variability in GRMHD simulations

2020 ◽  
Vol 496 (3) ◽  
pp. 3808-3828
Author(s):  
D A Bollimpalli ◽  
R Mahmoud ◽  
C Done ◽  
P C Fragile ◽  
W Kluźniak ◽  
...  
Keyword(s):  
Black Hole ◽  
Power Spectra ◽  
Time Lags ◽  
X Ray ◽  
Accretion Flows ◽  
Mass Fluxes ◽  
Frequency Independent ◽  
Show Evidence ◽  
General Relativistic ◽  
Characteristic Features

ABSTRACT Long-term observations have shown that black hole X-ray binaries exhibit strong, aperiodic variability on time-scales of a few milliseconds to seconds. The observed light curves display various characteristic features like a lognormal distribution of flux and a linear rms–flux relation, which indicate that the underlying variability process is stochastic in nature. It is also thought to be intrinsic to accretion. This variability has been modelled as inward propagating fluctuations of mass accretion rate, although the physical process driving the fluctuations remains puzzling. In this work, we analyse five exceptionally long-duration general relativistic magnetohydrodynamic (GRMHD) simulations of optically thin, geometrically thick, black hole accretion flows to look for hints of propagating fluctuations in the simulation data. We find that the accretion profiles from these simulations do show evidence for inward propagating fluctuations below the viscous frequency by featuring strong radial coherence and positive time lags when comparing smaller to larger radii, although these time lags are generally shorter than the viscous time-scale and are frequency-independent. Our simulations also support the notion that the fluctuations in $\dot{M}$ build up in a multiplicative manner, as the simulations exhibit linear rms–mass flux relations, as well as lognormal distributions of their mass fluxes. When combining the mass fluxes from the simulations with an assumed emissivity profile, we additionally find broad agreement with observed power spectra and time lags, including a recovery of the frequency dependency of the time lags.

scholarly journals Jets from Compact X-ray Sources

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.

scholarly journals Variability of Black Hole Accretion Disks

1994 ◽  
Vol 159 ◽  
pp. 487-487
Author(s):  
Michael A. Nowak ◽  
Robert V. Wagoner
Keyword(s):  
Black Hole ◽  
Accretion Disks ◽  
Power Spectra ◽  
X Ray ◽  
Black Hole Accretion ◽  
Hole Accretion

We consider two forms of variability in black hole accretion disks: harmonically oscillating modes trapped near the disk inner edge, and noisy fluctuations throughout the entire disk. We apply the former to AGN disks, and the latter to the X-ray power spectra of GX339-4.

scholarly journals X-ray spectral and flux variability of the microquasar GRS 1758−258 on timescales from weeks to years

2020 ◽  
Vol 636 ◽  
pp. A51 ◽  
Author(s):  
Maria Hirsch ◽  
Katja Pottschmidt ◽  
David M. Smith ◽  
Arash Bodaghee ◽  
Marion Cadolle Bel ◽  
...  
Keyword(s):  
Black Hole ◽  
Power Spectra ◽  
State Transitions ◽  
X Ray ◽  
Soft State ◽  
Term Variation ◽  
Transient Sources ◽  
Hard State ◽  
Proportional Counter Array

We present the spectral and timing evolution of the persistent black hole X-ray binary GRS 1758−258 based on almost 12 years of observations using the Rossi X-ray Timing Explorer Proportional Counter Array. While the source was predominantly found in the hard state during this time, it entered the thermally dominated soft state seven times. In the soft state GRS 1758−258 shows a strong decline in flux above 3 keV rather than the pivoting flux around 10 keV more commonly shown by black hole transients. In its 3–20 keV hardness intensity diagram, GRS 1758−258 shows a hysteresis of hard and soft state fluxes typical for transient sources in outburst. The RXTE-PCA and RXTE-ASM long-term light curves do not show any orbital modulations in the range of 2–30 d. However, in the dynamic power spectra significant peaks drift between 18.47 and 18.04 d for the PCA data, while less significant signatures between 19 d and 20 d are seen for the ASM data as well as for the Swift/BAT data. We discuss different models for the hysteresis behavior during state transitions as well as possibilities for the origin of the long term variation in the context of a warped accretion disk.

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