Understanding spectral variability and time lags in accreting black holes

Poutanen, Juri

doi:10.1016/s0273-1177(01)00406-9

Cited by 42 publications

(52 citation statements)

References 66 publications

(90 reference statements)

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“…The difference between these states does not seem to be related to radiation pressure instability, but there must be a mechanism of hot plasma generation that works less efficiently when the total flux is larger. There are several phenomenological models proposed, but the physics of formation and geometry of hot plasma is under discussion (e.g., Poutanen 2001;Di Salvo et al 2001). Some objects in the high state are possibly slightly above the threshold predicted by our model, although their coronal emission is not stronger than f cor ¼ 0:5 (LMC X-3 and J1748À288).…”

Section: Luminosity States In Other Sources and Their Relation To Radmentioning

confidence: 69%

Radiation Pressure Instability Driven Variability in the Accreting Black Holes

Janiuk

Czerny

Siemiginowska

2002

ApJ

117

191

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The time-dependent evolution of the accretion disk around the black hole is computed. The classical description of the -viscosity is adopted so the evolution is driven by the instability operating in the innermost radiation pressure-dominated part of the accretion disk. We assume that the optically thick disk always extends down to the marginally stable orbit, so it is never evacuated completely. We include the effect of the advection, coronal dissipation, and vertical outflow. We show that the presence of the corona and/or the outflow reduces the amplitude of the outburst. If only about half of the energy is dissipated in the disk (with the other half dissipated in the corona and carried away by the outflow), the outburst amplitude and duration are consistent with observations of the microquasar GRS 1915+105. Viscous evolution explains in a natural way the lack of direct transitions from the state C to the state B in the color-color diagram of this source. Further reduction of the fraction of energy dissipated in the optically thick disk switches off the outbursts, which may explain why they are not seen in all high accretion rate sources being in the very high state.

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Section: Luminosity States In Other Sources and Their Relation To Radmentioning

confidence: 69%

Radiation Pressure Instability Driven Variability in the Accreting Black Holes

Janiuk

Czerny

Siemiginowska

2002

ApJ

117

191

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“…Gierliński et al 1999). The soft radiation is expected to come from an optically thick, geometrically thin accretion disc, while the hard emission is usually explained by a hot, optically thin medium where the soft disk photons are Comptonized Poutanen 2001).…”

Section: Hardness and Spectral Indexmentioning

confidence: 99%

“…Seed photons from the disk are believed to gain energy in the corona through Comptonization ). The models vary in the geometry and properties of mainly the corona/comptonizing region (for a review on coronal models, especially in regard to timing characteristics, see Poutanen 2001). However, changes in the inner radius of the accretion disk are a common source of variability in many models (e.g.…”

Section: Introductionmentioning

confidence: 99%

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

Axelsson¹,

Borgonovo²,

Larsson³

2005

A&A

112

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Abstract. Analyzing the archival data from the Rossi X-ray Timing Explorer (RXTE), we study the power density spectra (PDS) of Cygnus X-1 from 1996 to 2003 in the frequency range of 0.01-25 Hz. Using a model consisting of one or two Lorentzians and/or an exponentially cut-off power-law, we are able to achieve a good fit to the PDS during the observations. With our model we are also able to track the evolution of the Lorentzian components through all spectral states of the source. We confirm the relation between characteristic frequencies seen both in black hole candidate and neutron star sources, and show the changes in this relation during the transitional and soft states of the source. The connection between the Lorentzian components is investigated by analyzing similarities and differences in their behavior. We find that the spectral state of the source can be uniquely determined from the parameters of these components. The parameter correlations can all be described by continuous functions, which differ between components. We discuss our results in the context of relativistic precession model for the accretion disk, and show a remarkable agreement between the model prediction and the data in the hard state. We estimate a value for the specific angular momentum of a * = 0.49 (−0.57) in the case of prograde (retrograde) rotation and an estimate for the inner radius of 22 to 50 (25 to 55) gravitational radii. Additional assumptions are required to explain the soft state data, and attempting to invoke rotational reversal for state transitions shows that it is insufficient to explain the differences between the hard and soft state data.

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“…These studies potentially offer a method for constraining the emission models and their geometry (e.g. Edelson et al 2002;Poutanen 2001). …”

Section: Introductionmentioning

confidence: 99%

Mapping the inner regions of MCG-6-30-15 withXMM-Newton

Ponti

Cappi

Dadina

et al. 2004

A&A

134

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Abstract. Timing analysis of a ∼95 ks long XMM-Newton observation of the Seyfert 1 galaxy MCG-6-30-15 is presented. Model-independent tools have been used with the intent of resolving the different components that produce the observed flux and spectral variations down to timescales as short as ∼300 s. We find that the fractional variability is possibly due to a variable power law component in the hard band, and a slower thermal component at softer energies, but the data do not rule out effects due to the warm absorber. The most relevant result of this work is the first detection of a significant enhancement of the fractional variability in the ∼4.7−5.8 keV energy band compared to the underlying continuum. This represents one of the strongest, model-independent, pieces of evidence to date for the presence of redshifted relativistic matter accreting into the black hole. During the brightest flare of the observation, a soft-to-hard time lag of ∼600 s is measured. A very significant increase of the iron line intensity is observed ∼3000 s after this flare. In the framework of a disk-corona model and assuming the soft-to-hard time lag is due to Comptonization, these findings make it possible to estimate the electron density and the dimensions of the flare region and the disk-flare distance.

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Understanding spectral variability and time lags in accreting black holes

Cited by 42 publications

References 66 publications

Radiation Pressure Instability Driven Variability in the Accreting Black Holes

Radiation Pressure Instability Driven Variability in the Accreting Black Holes

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

Mapping the inner regions of MCG-6-30-15 withXMM-Newton

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