Long term variability of Cygnus X-1

Grinberg, V.; Leutenegger, Maurice A.; Hell, N.; Pottschmidt, K.; Böck, M.; García, Javier A.; Hanke, Manfred; Nowak, Michael A.; Sundqvist, J. O.; Townsend, R. H. D.; Wilms, J.

doi:10.1051/0004-6361/201425418

Cited by 52 publications

(80 citation statements)

References 79 publications

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“…5, colored data points). The observed variation suggests that part of the neutral N Ne is intrinsic to the source and varies with orbital phase, with a minimum at φ orb ∼ 0.5, consistent with earlier studies of the N H variation in the system (e.g., Grinberg et al 2015;Wen et al 1999;Kitamoto et al 2000). We note, however, that a potential systematic uncertainty is that only ObsID 11044 (φ orb ∼ 0.5) does not show any significant absorption lines in the range of the Ne edge, while for the other ObsIDs this region is populated by many strong lines from ionized Fe.…”

Section: Column Density Variation Of the Neutral Absorbersupporting

confidence: 90%

“…N H is thus a measure for both the ISM foreground absorption and the column of mildly ionized material in the stellar wind. Earlier monitoring, e.g., with RXTE, showed a modulation of N H with orbital phase (Grinberg et al 2015;Hanke 2011;Wilms et al 2006;Kitamoto et al 2000;Holt et al 1976), although we note that some of the modulation seen there is also caused by dips, which were not removed in these analyses.…”

Section: Column Density Variation Of the Neutral Absorbermentioning

confidence: 65%

“…3.2), which were reduced using our standard procedures as described, e.g., by Wilms et al (2006) or Grinberg et al (2015). Figure 2 shows the RXTE All-Sky-Monitor (ASM; Levine et al 1996) lightcurve of Cyg X-1 around the times of the Chandra observations.…”

Section: Selection Of Observationsmentioning

confidence: 99%

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ChandraX-ray spectroscopy of focused wind in the Cygnus X-1 system

Miškovičová

Hell

Hanke

et al. 2016

A&A

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Accretion onto the black hole in the system HDE 226868/Cygnus X-1 is powered by the strong line-driven stellar wind of the O-type donor star. We study the X-ray properties of the stellar wind in the hard state of Cyg X-1, as determined using data from the Chandra High Energy Transmission Gratings. Large density and temperature inhomogeneities are present in the wind, with a fraction of the wind consisting of clumps of matter with higher density and lower temperature embedded in a photoionized gas. Absorption dips observed in the light curve are believed to be caused by these clumps. This work concentrates on the non-dip spectra as a function of orbital phase. The spectra show lines of H-like and He-like ions of S, Si, Na, Mg, Al, and highly ionized Fe (Fe xvii-Fe xxiv). We measure velocity shifts, column densities, and thermal broadening of the line series. The excellent quality of these five observations allows us to investigate the orbital phase-dependence of these parameters. We show that the absorber is located close to the black hole. Doppler shifted lines point at a complex wind structure in this region, while emission lines seen in some observations are from a denser medium than the absorber. The observed line profiles are phase-dependent. Their shapes vary from pure, symmetric absorption at the superior conjunction to P Cygni profiles at the inferior conjunction of the black hole.

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Section: Column Density Variation Of the Neutral Absorbersupporting

confidence: 90%

Section: Column Density Variation Of the Neutral Absorbermentioning

confidence: 65%

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ChandraX-ray spectroscopy of focused wind in the Cygnus X-1 system

Miškovičová

Hell

Hanke

et al. 2016

A&A

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“…The orbital period is observed at all wavelengths: optical, infrared (Gies & Bolton 1982), X-ray , and also at radio frequencies (Pooley et al 1999), suggesting that such a modulation could be the result of absorption by the stellar wind (Brocksopp et al 2002). As confirmation, Grinberg et al (2015) show that the absorption column density in the HS is strongly modulated with a maximum around superior conjunction. The existence of the radio modulation supports the idea that radio emission comes from a continuous jet versus discrete ejections.…”

Section: Introductionmentioning

confidence: 60%

Gamma rays detected from Cygnus X-1 with likely jet origin

Zanin

Fernández-Barral

Wilhelmi

et al. 2016

A&A

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Aims. Probe the high-energy (>60 MeV) emission from the black hole X-ray binary system, Cygnus X-1, and investigate its origin. Methods. We analysed 7.5 yr of data by Fermi-LAT with the latest Pass 8 software version. Results. We report the detection of a signal at ∼8 σ statistical significance spatially coincident with Cygnus X-1 and a luminosity above 60 MeV of 5.5×10 33 erg s −1 . The signal is correlated with the hard X-ray flux: the source is observed at high energies only during the hard X-ray spectral state, when the source is known to display persistent, relativistic radio emitting jets. The energy spectrum, extending up to ∼20 GeV without any sign of spectral break, is well fitted by a power-law function with a photon index of 2.3±0.2. There is a hint of orbital flux variability, with high-energy emission mostly coming around the superior conjunction. Conclusions. We detected GeV emission from Cygnus X-1 and probed that the emission is most likely associated with the relativistic jets. The evidence of flux orbital variability points to the anisotropic inverse Compton on stellar photons as the mechanism at work, thus constraining the emission region to a distance 10 11 − 10 13 cm from the black hole.

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“…The donor star HDE 226868 is close to filling its Roche lobe (Gies & Bolton 1986), creating a focused wind towards the black hole (Friend & Castor 1982), where the wind material forms an accretion disk. The observed X-ray flux from the disk is orbital-phase dependent, since the wind material can absorb a significant amount of the flux, resulting in spectral absorption and, in the most extreme cases, dips in the lightcurves of the observed object (see, e.g., Grinberg et al 2015;Miškovičová et al 2016;Hanke et al 2009;Díaz Trigo et al 2006;Bałucińska-Church et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Revealing the broad iron Kαline in Cygnus X-1 through simultaneousXMM-Newton, RXTE, and INTEGRAL observations

Duro

Dauser

Grinberg

et al. 2016

A&A

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We report on the analysis of the broad Fe Kα line feature of Cyg X-1 in the spectra of four simultaneous hard intermediate state observations made with the X-ray Multiple Mirror mission (XMM-Newton), the Rossi X-ray Timing Explorer (RXTE), and the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The high quality of the XMM-Newton data taken in the Modified Timing Mode of the EPIC-pn camera provides a great opportunity to investigate the broadened Fe Kα reflection line at 6.4 keV with a very high signal to noise ratio. The 4-500 keV energy range is used to constrain the underlying continuum and the reflection at higher energies. We first investigate the data by applying a phenomenological model that consists of the sum of an exponentially cutoff power law and relativistically smeared reflection. Additionally, we apply a more physical approach and model the irradiation of the accretion disk directly from the lamp post geometry. All four observations show consistent values for the black hole parameters with a spin of a ∼ 0.9, in agreement with recent measurements from reflection and disk continuum fitting. The inclination is found to be i ∼ 30• , consistent with the orbital inclination and different from inclination measurements made during the soft state, which show a higher inclination. We speculate that the difference between the inclination measurements is due to changes in the inner region of the accretion disk.

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Long term variability of Cygnus X-1

Cited by 52 publications

References 79 publications

ChandraX-ray spectroscopy of focused wind in the Cygnus X-1 system

ChandraX-ray spectroscopy of focused wind in the Cygnus X-1 system

Gamma rays detected from Cygnus X-1 with likely jet origin

Revealing the broad iron Kαline in Cygnus X-1 through simultaneousXMM-Newton, RXTE, and INTEGRAL observations

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