On the interpretation of the multicolour disc model for black hole candidates

Merloni, A.; Fabian, A. C.; Ross, R. R.

doi:10.1046/j.1365-8711.2000.03226.x

Cited by 242 publications

(305 citation statements)

References 13 publications

(22 reference statements)

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“…Using a distance of 7.4 kpc and an inclination angle of 35 • , we obtain a best-fitting value of 11.4 km. However, this value is generally considered an underestimation of the true inner radius by a factor of ∼2 (Merloni et al 2000). Taking these corrective factors into account, we derive an inner disk radius of ∼10 R g , consistent with the smearing factor of the reflection component and with our estimate of the outer boundary layer radius as derived by the ratio of the continuum fluxes (D'Aí et al 2007;D'Aì et al 2009).…”

Section: The Soft Statesupporting

confidence: 80%

A self-consistent approach to the hard and soft states of 4U 1705-44

D’Aí¹,

Salvo²,

Ballantyne

et al. 2010

A&A

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Context. High-resolution spectroscopy has recently revealed in many low-mass X-ray binaries hosting a neutron star that the shape of the broad iron line observed in the 6.4-6.97 keV range is consistently well-fitted by a relativistically smeared line profile. Aims. The presence of other broad features, besides the iron line, together with a high S/N of the spectra offer the possibility of testing a self-consistent approach to the overall broadband reflection spectrum and evaluating the impact of the reflection component in the formation of the broadband X-ray spectra. Methods. We analyzed two XMM-Newton observations of the bright atoll source 4U 1705-44, which can be considered a prototype of the class of the persistent NS LMXBs showing both hard and soft states. The first observation was performed when the source was in a hard low flux state, the second during a soft, high-flux state. Both the spectra show broad iron emission lines. We fit the spectra using a two-component model, together with a reflection model specifically suited to the case of a neutron star, where the incident spectrum has a blackbody shape. Results. In the soft state, the reflection model, convolved with a relativistic smearing component, consistently describes the broad features present in the spectrum, and we find a clear relation between the temperature of the incident flux and the temperature of the harder X-ray component that we interpret as the boundary layer emission. In this state we find converging evidence that the boundary layer outer radius is ∼2 times the neutron star radius. In the low flux state, we observe a change in the continuum shape of the spectrum with respect to the soft state. Still, the broad local emission features can be associated with a disk reflecting matter, but in a lower ionization state, and possibly produced in an accretion disk truncated at greater distance. Conclusions. Our analysis provides strong evidence that the reflection component in soft states of LMXBs comes from to hard X-ray thermal irradiation, which we identify with the boundary layer emission, also present in the continuum model. In the hard state, the broad iron line if also produced by reflection, and the continuum disk emission can be self-consistently accounted if the disk is truncated at a greater distance than the soft state.

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Section: The Soft Statesupporting

confidence: 80%

A self-consistent approach to the hard and soft states of 4U 1705-44

D’Aí¹,

Salvo²,

Ballantyne

et al. 2010

A&A

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“…The apparent inner radius of the soft disk blackbody emission gives a radius of 8 ± 2 km, calculated for a distance to the source of 4.5 kpc (Kuulkers & van der Klis 2000). Note that this value is thought to underestimate the true inner radius by a factor of more than 2 (Merloni et al 2000). The power law dependence of the disk emissivity, r betor , is parametrized by the index betor, which is −(2.61 ± 0.03), indicating that the disk emission is dominated by irradiation by a central source (see Fabian et al 1989).…”

Section: Discussionmentioning

confidence: 93%

A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1

Piraino

Santangelo

Kaaret

et al. 2012

A&A

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We present the results of a spectroscopic study of the Fe Kα emission of the persistent neutron-star atoll low-mass X-ray binary and type I X-ray burster GX 3+1 with the EPIC-PN on board XMM-Newton. The source shows a flux modulation over several years and we observed it during its fainter phase, which corresponds to an X-ray luminosity of L X ∼ 10 37 erg s −1 . When fitted with a two-component model, the X-ray spectrum shows broad residuals at ∼6−7 keV that can be ascribed to an iron K α fluorescence line. In addition, lower energy features are observed at ∼3.3 keV, ∼3.9 keV and might originate from Ar XVIII and Ca XIX. The broad iron line feature is well fitted with a relativistically smeared profile. This result is robust against possible systematics caused by instrumental pile-up effects. Assuming that the line is produced by reflection from the inner accretion disk, we infer an inner disk radius of ∼25R g and a disk inclination of 35 • < i < 44 • .

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“…From the normalization of the thermal component we are able to calculate the inner radius of the accretion disc (R in = D √ (N/ cos θ) km, D is the distance of the source in units of 10 kpc, θ is the inclination angle of the disc, and N is the normalization of the disc-blackbody). However, this radius is always underestimated, since what we calculate is not the effective radius of the disc (the radius corresponding to the higher inner temperature), but the radius derived from the color temperature (see Merloni et al 1999). All the energy spectra are fitted using this model, modified with photoelectric absorption (the equivalent hydrogen column density was fixed to 7 × 10 22 cm −2 , see Sect.…”

Section: Discussionmentioning

confidence: 99%

Evidence for local mass accretion rate variations in the disc of GRS 1915+105

Migliari

Belloni²

2003

A&A

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Abstract.We have analysed 16 observations of class β of GRS 1915+105 performed with the Rossi X-ray Timing Explorer. We show the time-resolved evolution (every 16 s) of the X-ray spectral parameters during these observations. The three model independent states (A, B, C) identified in the color-color diagrams are described here in terms of the more physical (and model dependent) quantities of the disc and power law components. As in the color analysis, we observe specific and time-asymmetric transitions between states. Within a single observation, we identified a loop-like cycle of the power law spectral index that starts and ends with the ending of state C. There is evidence of local mass accretion rate variations and mass loss during the long instability intervals (long state C). This is consistent with simultaneous radio and X-ray observations that show a one-to-one relation between the long state C and the radio flares, that occur shortly after it: a loss of disc mass is followed by an ejection of matter in the jet.

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On the interpretation of the multicolour disc model for black hole candidates

Cited by 242 publications

References 13 publications

A self-consistent approach to the hard and soft states of 4U 1705-44

A self-consistent approach to the hard and soft states of 4U 1705-44

A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1

Evidence for local mass accretion rate variations in the disc of GRS 1915+105

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