Spectroscopy of the Stellar Wind in the Cygnus X-1 System

Miškovičová, Ivica; Hanke, Manfred; Wilms, J.; Nowak, Michael A.; Pottschmidt, K.; Schulz, Norbert S.

doi:10.14311/1332

Cited by 3 publications

(3 citation statements)

References 12 publications

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“…In addition to the general change in spectral shape due to photoelectric absorption, we see strong changes between the individual dipping stages in the region between 1.6 keV and 2.7 keV (7.7-4.6 Å), where absorption lines of silicon and sulfur ions are the most prominent spectral features (box in Fig. 4, see also Miškovičová et al 2011). We therefore concentrate on these Si and S lines.…”

Section: Spectral Evolution From Non-dip To Dipmentioning

confidence: 78%

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

Hirsch

Hell

Grinberg

et al. 2019

A&A

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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.

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Section: Spectral Evolution From Non-dip To Dipmentioning

confidence: 78%

“…Clear P Cygni-like profiles for Cyg X-1 were reported only at φ orb = 0.5 during ObsID 11044 (Miškovičová et al 2011). Schulz et al (2002b) also found indications of P Cygni profiles at φ orb = 0.74.…”

Section: Line Symmetrymentioning

confidence: 87%

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

Hirsch

Hell

Grinberg

et al. 2019

A&A

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“…H-and He-like, ions (Hanke et al 2009, Miškovičová et al 2012, in the case of silicon and, with lower signal to noise, sulfur those lines grow significantly weaker with increasing dipping strength. Instead, 1s-2p transitions of low charge states (Li-through N-like) of the same elements appear, indicating a shift of the charge balance of the observed spectra toward low ionization states (Miškovičová et al 2011(Miškovičová et al , 2012. The latter can only be in equilibrium with the radiation field, if they exist in correspondingly dense clumps of material.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2013

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Strong, relatively short, absorption dips have been observed in the x-ray light curves measured from the high mass x-ray binary system Cygnus X-1. With increasing strength of the dips, which are believed to be caused by 'clumps' of cold material present in the stellar wind of Cyg X-1's companion star, K-shell absorption lines in L-shell ions of Si and S develop. To determine the bulk motion of the clumps via the Doppler shifts of these lines with high accuracy, we measured their reference energies using the Lawrence Livermore National Laboratory electron beam ion trap EBIT-I and EBIT Calorimeter Spectrometer. Our findings-shifts consistent with zero velocity of the absorber throughout all ionization states at orbital phase zero-provide evidence for an onion-like ion structure of the clumps.

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The broad-band radio spectrum of LS I +61°303 in outburst

Zimmermann

Fuhrmann

Massi

2015

A&A

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Aims. Our aim is to explore the broad-band radio continuum spectrum of LS I +61 • 303 during its outbursts by employing the available set of secondary focus receivers of the Effelsberg 100 m telescope. Methods. The clear periodicity of the system LS I +61 • 303 allowed observations to be scheduled covering the large radio outburst in March-April 2012. We observed LS I +61 • 303 on 14 consecutive days at 2. 6, 4.85, 8.35, 10.45, 14.3, 23, and 32 GHz with a cadence of about 12 h followed by two additional observations several days later. Based on these observations we obtained a total of 24 quasi-simultaneous broad-band radio spectra. Results. During onset, the main flare shows an almost flat broad-band spectrum, most prominently seen on March 27, 2012, wherefor the first time -a flat spectrum (α = 0.00 ± 0.07, S ∝ ν α ) is observed up to 32 GHz (9 mm wavelength). The flare decay phase shows superimposed "sub-flares" with the spectral index oscillating between −0.4 and −0.1 in a quasi-regular fashion. Finally, the spectral index steepens during the decay phase, showing optically thin emission with values α ∼ −0.5 to −0.7. Conclusions. The radio characteristics of LS I +61 • 303 compare well with those of the microquasars XTE J1752-223 and Cygnus X-3. In these systems the flaring phase is actually also composed of a sequence of outbursts with clearly different spectral characteristics: a first outburst with a flat/inverted spectrum followed by a bursting phase of optically thin emission.

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Spectroscopy of the Stellar Wind in the Cygnus X-1 System

Cited by 3 publications

References 12 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

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

The broad-band radio spectrum of LS I +61°303 in outburst

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