Evolution of the 0.01–25 Hz power spectral components in Cygnus X-1

Axelsson, M.; Borgonovo, Luis; Larsson, Stefan

doi:10.1051/0004-6361:20042362

Cited by 77 publications

(128 citation statements)

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“…This behavior is consistent with the appearance of the third Lorentzian component in the very hard observations analyzed by Pottschmidt et al (2003) and Axelsson et al (2005). We note that the hardest observations analyzed by these authors are from before 1998 April, i.e., during a time not covered by the data mode we use, while the hardest spectra analyzed here were observed during the long hard state between mid-2006 and mid-2010 Grinberg et al 2013).…”

Section: Energy-independent Evolution Of Psds With Spectral Shapesupporting

confidence: 90%

“…In the spirit of the approach chosen here that avoids depending on models for the variability, we label the lower frequency variability component as component 1 and the higher frequency variability component as component 2. Both components shift to higher frequencies as Γ 1 softens (see also Cui et al 1997;Gilfanov et al 1999;Pottschmidt et al 2003;Axelsson et al 2005;Shaposhnikov & Titarchuk 2006;Böck et al 2011). The two components appear to have roughly similar strengths.…”

Section: Energy-independent Evolution Of Psds With Spectral Shapementioning

confidence: 88%

“…At the time of writing there had been no changes to relevant pieces of HEASOFT since this release. We stress the importance of the orbit-wise approach, as spectral and timing properties of Cyg X-1 can change on timescales of less than a few hours (Axelsson et al 2005;Böck et al 2011;Grinberg et al 2013). 150 100 50 0 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 Grinberg et al (2013), which uses both ASM count rate and ASM hardness of a given measurement: blue represents the hard state, green the intermediate state, and red the soft state.…”

Section: Discussionmentioning

confidence: 99%

“…Parts of the data have been analyzed in the previous papers of this series (Pottschmidt et al 2003;Gleissner et al 2004b,a;Wilms et al 2006;Grinberg et al 2013) and by other authors (e.g., Axelsson et al 2005Axelsson et al , 2006Shaposhnikov & Titarchuk 2006). For all pointed RXTE observations of Cyg X-1 made during the lifetime of the RXTE satellite (MJD 50 071-55 931), we extracted spectral data in the standard2f mode from Proportional Counter Unit 2 of RXTE's Proportional Counter Array (PCA, Jahoda et al 2006) and from RXTE's High Energy X-ray Timing Experiment (HEXTE, Rothschild et al 1998) on a satellite orbit by satellite orbit basis.…”

Section: Discussionmentioning

confidence: 99%

“…The strict use of the same data mode means that we do not cover some of the observations included in previous long-term monitoring analyses by Pottschmidt et al (2003), Axelsson et al (2005Axelsson et al ( , 2006, or Shaposhnikov & Titarchuk (2006), especially the data from the extreme hard state before 1998 May. The long time span covered in this work that includes the extraordinarily long, hard state of ∼MJD 53900-55375 (mid-2006 to mid-2010), and the following series of stable soft states represents, however, a major improvement over all previous analyses.…”

Section: Long-term Source Behaviormentioning

confidence: 99%

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Long term variability of Cygnus X-1

Grinberg

Pottschmidt

Böck

et al. 2014

A&A

116

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We present the most extensive analysis of Fourier-based X-ray timing properties of the black hole binary Cygnus X-1 to date, based on 12 years of bi-weekly monitoring with RXTE from 1999 to 2011. Our aim is a comprehensive study of timing behavior across all spectral states, including the elusive transitions and extreme hard and soft states. We discuss the dependence of the timing properties on spectral shape and photon energy, and study correlations between Fourier-frequency dependent coherence and time lags with features in the power spectra. Our main results follow. (a) The fractional rms in the 0.125-256 Hz range in different spectral states shows complex behavior that depends on the energy range considered. It reaches its maximum not in the hard state, but in the soft state in the Comptonized tail above 10 keV. (b) The shape of power spectra in hard and intermediate states and the normalization in the soft state are strongly energy-dependent in the 2.1-15 keV range. This emphasizes the need for an energy-dependent treatment of power spectra and a careful consideration of energy-and mass-scaling when comparing the variability of different source types, e.g., black hole binaries and AGN. PSDs during extremely hard and extremely soft states can be easily confused for energies above ∼5 keV in the 0.125-256 Hz range. (c) The coherence between energy bands drops during transitions from the intermediate into the soft state but recovers in the soft state. (d) The time lag spectra in soft and intermediate states show distinct features at frequencies related to the frequencies of the main variability components seen in the power spectra and show the same shift to higher frequencies as the source softens. Our results constitute a template for other sources and for physical models for the origin of the X-ray variability. In particular, we discuss how the timing properties of Cyg X-1 can be used to assess the evolution of variability with spectral shape in other black hole binaries. Our results suggest that none of the available theoretical models can explain the full complexity of X-ray timing behavior of Cyg X-1, although several ansatzes with different physical assumptions are promising.

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Section: Energy-independent Evolution Of Psds With Spectral Shapesupporting

confidence: 90%

Section: Energy-independent Evolution Of Psds With Spectral Shapementioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Long-term Source Behaviormentioning

confidence: 99%

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Long term variability of Cygnus X-1

Grinberg

Pottschmidt

Böck

et al. 2014

A&A

116

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Modelling Spectral and Timing Properties of Accreting Black Holes: The Hybrid Hot Flow Paradigm

Poutanen

Veledina

2013

The Physics of Accretion Onto Black Holes

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The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to 100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.

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X-Ray Variability of AGN and Relationship to Galactic Black Hole Binary Systems

McHardy

2009

Lecture Notes in Physics

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Over the last 12 years, AGN monitoring by RXTE has revolutionised our understanding of the X-ray variability of AGN, of the relationship between AGN and Galactic black hole X-ray binaries (BHBs) and hence of the accretion process itself, which fuels the emission in AGN and BHBs and is the major source of power in the universe. In this paper I review our current understanding of these topics.I begin by considering whether AGN and BHBs show the same X-ray spectraltiming 'states' (e.g. low-flux, hard-spectrum or 'hard' and high-flux, soft-spectrum or 'soft'). Observational selection effects mean that most of the AGN which we have monitored will probably be 'soft state' objects, but AGN are found in the other BHB states, although possibly with different critical transition accretion rates.I examine timescale scaling relationships between AGN and BHBs. I show that characteristic power spectral 'bend' timescales, TB, scale approximately with black hole mass, MBH , but inversely with accretion rate,ṁE (in units of the Eddington accretion rate) probably signifying that TB arises at the inner edge of the accretion disc. The relationship TB ∝ MBH /ṁE is a good fit, implying that no other potential variable, e.g. black hole spin, varies significantly. Lags between hard and soft X-ray bands as a function of Fourier timescale follow similar patterns in AGN and BHBs.I show how our improved understanding of X-ray variability enables us to understand larger scale properties of AGN. For example, the width of the H β optical emission line, V , scales as T 1/4 B , providing a natural explanation of the observed small black hole masses in Narrow Line Seyfert Galaxies; if MBH were large then, as TB ∝ MBH /ṁE, we would requireṁE> 1 to obtain narrow lines. I note that the rms X-ray variability scales linearly with flux in both AGN and BHBs, indicating that the amplitude of the shorter timescale variations is modulated by that of the longer timescale variations, ruling out simple shot-noise variability models. Blazars follow approximately the same pattern. The variations may therefore arise in the accretion disc and propagate inwards until they hit, and modulate, the X-ray emission region which, in the case of blazars, lies in a relativistic jet. Short timescale (weeks) optical variability arises from reprocessing of X-rays in the accretion disc, providing a diagnostic of X-ray source geometry. On longer timescales, variations in the disc accretion rate may dominate optical variations. AGN X-ray monitoring has greatly increased our understanding of the accretion process and there is a strong case for continued monitoring with future observatories.

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Evolution of the 0.01–25 Hz power spectral components in Cygnus X-1

Cited by 77 publications

References 42 publications

Long term variability of Cygnus X-1

Long term variability of Cygnus X-1

Modelling Spectral and Timing Properties of Accreting Black Holes: The Hybrid Hot Flow Paradigm

X-Ray Variability of AGN and Relationship to Galactic Black Hole Binary Systems

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