Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system III. Dipping in the low/hard state

Abstract

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 $\equiv$ 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.

19 pages, 15 figures, accepted for publication in A&A

References in corpus (15)

• Mass loss from hot massive stars
• Bright OB stars in the Galaxy - III. Constraints on the radial stratification of the clumping factor in hot star winds from a combined Halpha, IR and radio analysis
• X-ray Spectral Study of the Photoionized Stellar Wind in Vela~X-1
• Towards a unified view of inhomogeneous stellar winds in isolated supergiant stars and supergiant high mass X-ray binaries
• High resolution X-ray spectroscopy of bright O type stars
• Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulation and spectral hardness on the superorbital phase
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system. I. The non-dip spectrum in the low/hard state
• Stellar Wind Variations During the X-ray High and Low States of Cygnus X-1
• Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1 / HDE 226868 system
• The clumpy absorber in the high-mass X-ray binary Vela X-1
• Origin of the X-ray off-states in Vela X-1
• A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522
• Laboratory Measurements of the K-shell transition energies in L-shell ions of Si and S
• Beyond XSPEC: Towards Highly Configurable Analysis
• Ultraviolet observations of the X-ray photoionized wind of Cygnus X-1 during X-ray soft/high state

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