X‐Ray Shots of Cygnus X‐1

Feng, Yuxin; Li, T. P.; Chen, L.

doi:10.1086/306946

Cited by 31 publications

(34 citation statements)

References 28 publications

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“…This strongly constrains the origin of the spectral variability since it requires that the pulses producing the variability last longer at low energies than at higher energies. Similar energy dependence is observed also in the ACF of the peak aligned average shot profiles (Feng et al 1999). Our results extend their work by demonstrating that the trend of the width of the ACF versus energy applies across more energy bands.…”

Section: Autocorrelation Functionssupporting

confidence: 88%

“…These are the last papers, to our knowledge, that present the CCFs, despite immense advances in temporal resolution, photon statistics, and duration of observations. Aside from attempts to model individual shots (Lochner, Swank, & Szymkowiak 1991;Negoro et al 1994;Focke 1998;Feng et al 1999), recent analyses have concentrated on Fourier domain techniques.…”

Section: Introductionmentioning

confidence: 99%

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Time Domain Analysis of Variability in Cygnus X-1: Constraints on the Emission Models

Maccarone

Coppi

Poutanen

2000

The Astrophysical Journal

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We use time domain analysis techniques to investigate the rapid variability of Cygnus X-1. We show that the cross-correlation functions between hard and soft energy bands reach values very close to unity and peak at a lag of less than 2 ms for energies separated by a factor of 10. This confirms that the process that produces Xray photons at different energies is extremely coherent on short timescales and strongly constrains emission models proposed to explain Fourier-frequency-dependent time lags. We present autocorrelation functions at different energies and note that their widths decrease with increasing energy. We show that the extended Compton corona model produces autocorrelation functions whose widths increase with increasing energy and that the model of cylindrical waves moving inward through a transition disk has too large a peak lag in the cross-correlation function. Models of magnetic flaring and of drifting blobs in a hot corona can qualitatively fit the observations.

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Section: Autocorrelation Functionssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Time Domain Analysis of Variability in Cygnus X-1: Constraints on the Emission Models

Maccarone

Coppi

Poutanen

2000

The Astrophysical Journal

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“…For many years, the time domain analysis was not applied to GBHs despite immense advances in temporal resolution, photon statistics, and duration of observations. Aside from attempts to model individual shots (Lochner, Swank, & Szymkowiak 1991;Negoro et al 1994;Feng et al 1999), recent analyses have concentrated on Fourier domain techniques.…”

Section: Variability In the Time Domain Auto-and Cross-correlation Fumentioning

confidence: 99%

Understanding spectral variability and time lags in accreting black holes

Poutanen

2001

Advances in Space Research

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I review the temporal/spectral data of accreting black hole sources paying most attention to the properties of the temporal variability such as photon energy dependent auto-and cross-correlation functions, average shot profiles and hardness ratios, and the Fourier frequency dependent time/phase lags. These statistics characterize spectral changes at short time scales that are otherwise impossible to study by direct spectral analysis. The data provide strong constraints on the theoretical models for X-ray production in accreting black holes. Models for the spectral variability of the Comptonized component are briefly reviewed. It is also shown that Compton reflection can have significant impact on the observed temporal characteristics.

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“…To overcome this difficulty, Negoro, Miyamoto, & Kitamoto (1994) obtained average X-ray shot proÐles from a Ginga observation of Cyg X-1 in the low state, by superposing many shots through aligning their peaks, and then studied their properties. Recently we analyzed the structures of X-ray shots with the characteristic timescale D0.01È0.1 s in the di †erent states of Cyg X-1 using PCA/RXT E observations and an improved searching and superposing algorithm (Feng, Li &, Chen 1998). From the obtained average shot proÐles we have observed some interesting features.…”

Section: Introductionmentioning

confidence: 99%

Temporal and Spectral Correlations of Cygnus X‐1

Feng

Chen

1999

ApJ

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Temporal and spectral properties of X-ray rapid variability of Cyg X-1 are studied through correlation analysis in the time domain on di †erent timescales. The correlation coefficients between the total intensity in the 2È60 keV band and the hardness ratio of the 13È60 keV to the 2È6 keV band on the timescale of D1 ms are always negative in all states. For soft states, the correlation coefficients are positive on all timescales from D0.01 to D100 s, which is signiÐcantly di †erent from those for transition and low states. The temporal structures in the high-energy band are narrower than those in low-energy band in quite a few cases. The delay of high-energy photons relative to low-energy ones in the X-ray variations has also been revealed by the correlation analysis. The implications of the observed temporal and spectral characteristics for the production region and mechanism of Cyg X-1 X-ray variations are discussed.

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X‐Ray Shots of Cygnus X‐1

Cited by 31 publications

References 28 publications

Time Domain Analysis of Variability in Cygnus X-1: Constraints on the Emission Models

Time Domain Analysis of Variability in Cygnus X-1: Constraints on the Emission Models

Understanding spectral variability and time lags in accreting black holes

Temporal and Spectral Correlations of Cygnus X‐1

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