An ionized accretion disk in Cygnus X-1

Done, Chris; Mulchaey, John S.; Mushotzky, R. F.; Arnaud, K. A.

doi:10.1086/171649

Cited by 211 publications

(235 citation statements)

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“…They obtained r in ≃ 2-5. We note that the ionization treatment of pexriv is highly approximate, using the ionization calculations of Done et al (1992). Also, the fits were done assuming i = 20 • .…”

Section: Appendix A: Comparison With Previous Spectral Resultsmentioning

confidence: 99%

Spectral analysis of theXMM–Newtondata of GX 339–4 in the low/hard state: disc truncation and reflection

Basak¹,

Zdziarski²

2016

Mon. Not. R. Astron. Soc.

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We analyse all available observations of GX 339-4 by XMM-Newton in the hard spectral state. We jointly fit the spectral data by Comptonization and the currently best reflection code, relxill. We consider in detail a contribution from a standard blackbody accretion disc, testing whether its inner radius can be set equal to that of the reflector. However, this leads to an unphysical behaviour of the disc truncation radius, implying the soft X-ray component is not a standard blackbody disc. This appears to be due to irradiation by the hard X-rays, which strongly dominate the total emission. We consider a large array of models, testing, e.g., the effects of the chosen energy range, of adding unblurred reflection, and assuming a lamppost geometry. We find the effects of relativistic broadening to be relatively weak in all cases. In the coronal models, we find the inner radius to be large. In the lamppost model, the inner radius is unconstrained, but when fixed to the innermost stable orbit, the height of the source is large, which also implies a weak relativistic broadening. In the former models, the inner radius correlates with the X-ray hardness ratio, which is consistent with the presence of a truncated disc turning into a complete disc in the soft state. We also find the degree of the disc ionization to anti-correlate with the hardness, leading to strong spectral broadening due to scattering of reflected photons in the reflector in the softest studied states.

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Section: Appendix A: Comparison With Previous Spectral Resultsmentioning

confidence: 99%

Spectral analysis of theXMM–Newtondata of GX 339–4 in the low/hard state: disc truncation and reflection

Basak¹,

Zdziarski²

2016

Mon. Not. R. Astron. Soc.

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“…A possible source of this emission is the accretion stream, which is also indicated by a prolonged ingress after eclipse of the white dwarf. A way to reconcile the spectral slope with more realistic plasma temperature is by adopting an ionised absorber as implemented in xspec by the absori model (Done et al 1992). Introduction of the absori model significantly improves the fit to χ 2 ν = 1.38.…”

Section: X-ray and Uv Light Curve Morphologymentioning

confidence: 99%

Hunting high and low: XMM monitoring of the eclipsing polar HU Aquarii

Schwarz¹,

Schwope²,

Vogel³

et al. 2009

A&A

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Aims. We want to study the temporal and spectral behaviour of HU Aqr in the X-ray domain during different accretion states. Methods. We obtained spectra and light curves from four different XMM-Newton pointings covering intermediate and low states. The X-ray observations were accompanied with high time resolution photometry obtained with the Optima and ULTRACAM instruments. Results. On two occasions in May 2002 and 2003 HU Aqr was found in an intermediate state with the accretion rate reduced by a factor of 50 compared to earlier high state measurements. X-ray spectra in the intermediate state can be described by a model containing a blackbody component and hot thermal plasma. Contrary to the high state the ratio between soft and hard X-ray flux is nearly balanced. In agreement with previous measurements we observed a migration of the accretion spot and stream towards the line connecting both stars. The brightness of HU Aqr was further reduced by a factor of 80 during two low states in October 2003 and May 2005, where it was detected at a luminosity of only L X = 4.7 × 10 28 erg s −1 . This luminosity would fit well with an active coronal emitter, but the relatively high plasma temperatures of 3.5 and 2.0 keV are more compatible with residual accretion. We updated the eclipse ephemeris of HU Aqr based on the eclipse egress of the accretion spot measured in various wavelength bands. The (O−C)-diagram of the observed accretion spot eclipse timings reveals complex deviations from a linear trend, which can be explained by a constant or cyclic period change or a combination thereof. The quadratic term implies a period decrease at a rate oḟ P orb = −7.. − 11 × 10 −12 s s −1 . In case the observed period change reflects a true angular momentum loss, this would be a factor of 30 larger than given by gravitational radiation.

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“…We assume a temperature of the reflecting medium of 10 6 K, and allow it to be ionized, using the ionization calculations of Done et al (1992). We define the ionizing parameter as ξ ion ≡ 4πF ion /n, where F ion is the ionizing flux and n is the reflector density.…”

Section: Spectral Modelmentioning

confidence: 99%

Characterizing a new class of variability in GRS 1915+105 with simultaneousINTEGRAL/RXTEobservations

Hannikainen¹,

Rodríguez

Vilhu³

et al. 2005

A&A

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Abstract.We report on the analysis of 100 ks INTEGRAL observations of the Galactic microquasar GRS 1915+105. We focus on INTEGRAL Revolution number 48 when the source was found to exhibit a new type of variability as preliminarily reported in Hannikainen (2003, A&A, 411, L415). The variability pattern, which we name ξ, is characterized by a pulsing behaviour, consisting of a main pulse and a shorter, softer, and smaller amplitude precursor pulse, on a timescale of 5 min in the JEM-X 3-35 keV lightcurve. We also present simultaneous RXTE data. From a study of the individual RXTE/PCA pulse profiles we find that the rising phase is shorter and harder than the declining phase, which is opposite to what has been observed in other otherwise similar variability classes in this source. The position in the colour-colour diagram throughout the revolution corresponds to State A (Belloni et al. 2000, A&A, 355, 271) but not to any previously known variability class. We separated the INTEGRAL data into two subsets covering the maxima and minima of the pulses and fitted the resulting two broadband spectra with a hybrid thermal-non-thermal Comptonization model. The fits show the source to be in a soft state characterized by a strong disc component below ∼6 keV and Comptonization by both thermal and non-thermal electrons at higher energies.

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An ionized accretion disk in Cygnus X-1

Cited by 211 publications

References 0 publications

Spectral analysis of theXMM–Newtondata of GX 339–4 in the low/hard state: disc truncation and reflection

Spectral analysis of theXMM–Newtondata of GX 339–4 in the low/hard state: disc truncation and reflection

Hunting high and low: XMM monitoring of the eclipsing polar HU Aquarii

Characterizing a new class of variability in GRS 1915+105 with simultaneousINTEGRAL/RXTEobservations

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