X-ray and ultraviolet spectroscopy of Cygnus X-1 = HDE 226868

Pravdo, S. H.; White, N. E.; Becker, R. H.; Kondo, Y.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; McCluskey, G. E.

doi:10.1086/183237

Cited by 17 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is also observed for other sources (Hemphill et al 2014;Grinberg et al 2017). During the hard state of Cyg X-1, such short-term dipping events are observed predominantly during the upper conjunction of the black hole, i.e., when the line of sight passes through the densest region of the stellar wind and is most likely to pass through a clump (Li & Clark 1974;Mason et al 1974;Parsignault et al 1976;Pravdo et al 1980;Remillard & Canizares 1984;Kitamoto et al 1984;Bałucińska-Church et al 2000;Feng & Cui 2002;Poutanen et al 2008;Hanke et al 2009;Miškovičová et al 2016;Grinberg et al 2015). The precise structure of the clumps, i.e., their density and ionization structure, is unknown.…”

Section: Introductionsupporting

confidence: 59%

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

Hirsch

Hell

Grinberg

et al. 2019

A&A

View full text Add to dashboard Cite

We present an analysis of three Chandra High Energy Transmission Gratings observations of the black hole binary Cyg X-1/HDE 226868 at different orbital phases. The stellar wind that is powering the accretion in this system is characterized by temperature and density inhomogeneities including structures, or "clumps", of colder, more dense material embedded in the photoionized gas. As these clumps pass our line of sight, absorption dips appear in the light curve. We characterize the properties of the clumps through spectral changes during various dip stages. Comparing the silicon and sulfur absorption line regions (1.6-2.7 keV ≡ 7.7-4.6 Å) in four levels of varying column depth reveals the presence of lower ionization stages, i.e., colder or denser material, in the deeper dip phases. The Doppler velocities of the lines are roughly consistent within each observation, varying with the respective orbital phase. This is consistent with the picture of a structure that consists of differently ionized material, in which shells of material facing the black hole shield the inner and back shells from the ionizing radiation. The variation of the Doppler velocities compared to a toy model of the stellar wind, however, does not allow us to pin down an exact location of the clump region in the system. This result, as well as the asymmetric shape of the observed lines, point at a picture of a complex wind structure.

show abstract

Section: Introductionsupporting

confidence: 59%

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

Hirsch

Hell

Grinberg

et al. 2019

A&A

View full text Add to dashboard Cite

show abstract

“… References: 1 Mason et al 1974; 2 Li & Clark 1974; 3 Remillard & Canizares 1984; 4 Bałucińska 1988; 5 Pravdo et al 1980; 6 Kitamoto et al 1984; 7 Bałucińska & Hasinger 1991; 8 Present work; 9 Marshall et al 1993; 10 Bałucinska‐Church et al 1995; 11 Ebisawa et al 1996; 12 Bałucińska‐Church et al 1997. …”

Section: Observationsunclassified

The distribution of X-ray dips with orbital phase in Cygnus X-1

Bałucińska‐Church

Church

Charles

et al. 2000

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present results of a comprehensive study of the distribution of absorption dips with orbital phase in Cygnus X‐1. First, the distribution was obtained using archival data from all major X‐ray observatories and corrected for the selection effect that phase zero (superior conjunction of the black hole) has been preferentially observed. Dip occurrence was seen to vary strongly with orbital phase φ, with a peak at φ∼0.95, i.e. was not symmetric about phase zero. Secondly, the RXTE ASM has provided continuous coverage of the low state of Cygnus X‐1 since 1996 September, and we have selected dip data based on increases in hardness ratio. The distribution, with much increased numbers of dip events, confirms that the peak is at φ∼0.95, and we report the discovery of a second peak at φ∼0.6. We attribute this peak to absorption in an accretion stream from the companion star HDE 226868. We have estimated the ionization parameter ξ at different positions showing that radiative acceleration of the wind is suppressed by photoionization in particular regions in the binary system. To obtain the variation of column density with phase, we make estimates of neutral wind density for the extreme cases that acceleration of the wind is totally suppressed, or not suppressed at all. An accurate description will lie between these extremes. In each case, a strong variation of column density with orbital phase resulted, similar to the variation of dip occurrence. This provides evidence that formation of the blobs in the wind, which lead to absorption dips, depends on the density of the neutral component in the wind, suggesting possible mechanisms for blob growth.

show abstract

“…Further evidence comes from the modeling of the IR continuum emission (Rahoui et al 2011). Finally, in the X-rays, the overall absorption column density and dipping vary strongly with orbital phase and are largest at φ orb ∼ 0.0 (e.g., Li & Clark 1974;Mason et al 1974;Parsignault et al 1976;Pravdo et al 1980;Remillard & Canizares 1984;Kitamoto et al 1984Kitamoto et al , 1989Wen et al 1999;Bałucińska-Church et al 2000;Feng & Cui 2002;Lachowicz et al 2006;Poutanen et al 2008;Hanke et al 2009), which is consistent with the focused wind picture (e.g., Li & Clark 1974;Remillard & Canizares 1984;Bałucińska-Church et al 2000;Poutanen et al 2008). Owing to the presence of the focused wind, the accretion process in Cyg X-1 is not primarily wind accretion like in other HMXBs, such as Vela X-1, SMC X-1, or 4U 1700−37 (Bondi & Hoyle 1944;Blondin & Woo 1995;Blondin 1994;Blondin et al 1991), but a small accretion disk is present.…”

Section: Introductionmentioning

confidence: 99%

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

Miškovičová

Hell

Hanke

et al. 2016

A&A

View full text Add to dashboard Cite

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.

show abstract

X-ray and ultraviolet spectroscopy of Cygnus X-1 = HDE 226868

Cited by 17 publications

References 0 publications

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

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

The distribution of X-ray dips with orbital phase in Cygnus X-1

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

Contact Info

Product

Resources

About