Low charge states of Si and S in Cygnus X-1

Hell, N.; Miškovičová, Ivica; Brown, G. V.; Wilms, J.; Clementson, J.; Hanke, Manfred; Beiersdörfer, P.; Liedahl, D. A.; Pottschmidt, K.; Porter, F. S.; Kilbourne, Caroline A.; Kelley, R. L.; Nowak, Michael A.; Schulz, Norbert S.

doi:10.1088/0031-8949/2013/t156/014008

Cited by 17 publications

(17 citation statements)

References 9 publications

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“…This is more consistent with the picture of photons being reprocessed by clumps of material with an onion-like structure, where the outer layers shield the colder and denser core of the clump from the ionizing radiation of the compact object. Similar results were also obtained for Cyg X-1 (Hell et al 2013), where these lines are seen in absorption.…”

Section: Center Of Line Blendssupporting

confidence: 86%

“…Watanabe et al (2006) build a three-dimensional Monte-Carlo radiative transfer model and report a mass loss rate for the companion star and the structure of the wind, although they do not analyze the line emission from the L-shell silicon ions, but only from H-like Si. In the case of Cygnus X-1, the Kα absorption features in L-and K-shell ions of silicon and sulfur have been measured and used to diagnose the nature of the stellar wind (Hanke et al 2008;Hell et al 2013;Miškovičová et al 2016). Specifically, these features have been shown to be produced by "clumps" of onion-structured material, where the inner layers are colder, denser, and less ionized, moving in and out of the observational line of sight.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory Measurements of the K-Shell Transition Energies in L-Shell Ions of Si and S

Hell

Brown

Wilms

et al. 2016

ApJ

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We have measured the energies of the strongest 1s-2 ( ) = ℓ ℓ s, p transitions in He-through Ne-like silicon and sulfur ions to an accuracy of <1 eV using the Lawrence Livermore National Laboratory's electron beam ion traps, EBIT-I and SuperEBIT, and the NASA/GSFC EBIT Calorimeter Spectrometer (ECS). We identify and measure the energies of 18 and 21 X-ray features from silicon and sulfur, respectively. The results are compared to new Flexible Atomic Code calculations and to semi-relativistic Hartree-Fock calculations by Palmeri et al. (2008). These results will be especially useful for wind diagnostics in high-mass X-ray binaries, such as Vela X-1 and Cygnus X-1, where high-resolution spectral measurements using Chandraʼs high-energy transmission grating has made it possible to measure Doppler shifts of -100 km s 1 . The accuracy of our measurements is consistent with that needed to analyze Chandra observations, exceeding Chandraʼs -100 km s 1 limit. Hence, the results presented here not only provide benchmarks for theory, but also accurate rest energies that can be used to determine the bulk motion of material in astrophysical sources. We show the usefulness of our results by applying them to redetermine Doppler shifts from Chandra observations of Vela X-1.

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Section: Center Of Line Blendssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Laboratory Measurements of the K-Shell Transition Energies in L-Shell Ions of Si and S

Hell

Brown

Wilms

et al. 2016

ApJ

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“…As HDE 226868 fills > ∼ 90% of its Roche lobe (Gies et al 2003) and has a strong (a few 10 −6 M yr −1 , Gies et al 2003) fast wind, the black hole accretes via a focussed wind (Friend & Castor 1982;Gies & Bolton 1986a,b;Sowers et al 1998;Miller et al 2005;Hanke et al 2009;Hell et al 2013;Miškovičová et al 2015, and others). Values for ∞ for HDE 226868 vary in the literature: Davis & Hartmann (1983) obtain (2300±400) km s −1 in the hard state, but Vrtilek et al (2008) find 1420 km s −1 in the soft state.…”

Section: Introductionmentioning

confidence: 96%

Long term variability of Cygnus X-1

Grinberg

Leutenegger

Hell

et al. 2015

A&A

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Binary systems with an accreting compact object offer a unique opportunity to investigate the strong, clumpy, line-driven winds of early-type supergiants by using the compact object's X-rays to probe the wind structure. We analyze the two-component wind of HDE 226868, the O9.7Iab giant companion of the black hole Cyg X-1, using 4.77 Ms Rossi X-ray Timing Explorer (RXTE) observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-AbbottKlein wind: as it does not incorporate clumping, the model does not describe the observations well. A qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could either be due to lack of a focussed wind component in the model or to a more complicated clump structure.

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“…Holczer et al (2010) reported Si vi to Si xiv absorption lines in the slow warm absorber of bright Seyfert 1 galaxy MCG 6-30-15. Hell et al (2013) observed the K-shell absorption lines from Si viii to Si xiv in the high-mass X-ray binary Cygnus X-1. More recently, Si viii to Si xiv K lines have been detected in warm absorbers around the quasar MR 2251-178 (Reeves et al2013).…”

Section: Introductionmentioning

confidence: 99%

K-shell energy levels and radiative rates for transitions in Si ix

Wei

Shi

Wang

et al. 2014

A&A

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Context. Accurate atomic data are needed to analyze the Si ix K-shell features in astrophysical X-ray spectra. Relative large discrepancies in the existing atomic data have impeded this progress.Aims. We present the accurate Si ix K-shell transition data, including K-shell energy levels, wavelengths, radiative rates, and oscillator strengths. Methods. The flexible atomic code (FAC), which is a fully relativistic atomic code with configuration interaction (CI) included, was employed to calculate these data. To investigate the CI effects, calculations with different configurations included were carried out.Results. The K-shell atomic data of Si ix transitions between 1s 2 2s 2 2p 2 , 1s 2 2s2p 3 , 1s 2 2p 4 , 1s2s 2 2p 3 , 1s2s2p 4 , and 1s2p 5 are reported.The accuracy of our data is demonstrated by comparing them with the available experimental measurements and theoretical calculations. The energy levels are accurate to 3.5 eV, the wavelengths to within 15 mÅ. For most transitions, the radiative rates an accuracy of 20%. The effects of CI from high-energy configurations were investigated as well.

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Low charge states of Si and S in Cygnus X-1

Cited by 17 publications

References 9 publications

Laboratory Measurements of the K-Shell Transition Energies in L-Shell Ions of Si and S

Laboratory Measurements of the K-Shell Transition Energies in L-Shell Ions of Si and S

Long term variability of Cygnus X-1

K-shell energy levels and radiative rates for transitions in Si ix

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