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

Journal Article · · Astronomy and Astrophysics
 [1];  [2];  [3];  [1];  [4];  [5];  [6];  [1];  [1];  [7];  [2];  [1]
  1. Univ. Erlangen-Nurnberg, Bamberg (Germany)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. Tubingen, Tubingen (Germany)
  4. Washington Univ., St. Louis, MO (United States)
  5. Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  6. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  7. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
+ Show Author Affiliations

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.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1529832
Report Number(s):
LLNL-JRNL-761005; 949966
Journal Information:
Astronomy and Astrophysics, Vol. 626; ISSN 0004-6361
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions text January 2020
Highly charged ions in a new era of high resolution X‐ray astrophysics journal April 2019

Figures / Tables (22)

Fig. 1(p. 5)figure Fig. 1
Fig. 2(p. 5)figure Fig. 2
Table 1(p. 6)table Table 1
Fig. 3(p. 7)figure Fig. 3
Fig. 4(p. 7)figure Fig. 4
Table 2(p. 7)table Table 2
Fig. 5(p. 8)figure Fig. 5
Fig. 6(p. 10)figure Fig. 6
Table 3(p. 11)table Table 3
Table 4(p. 11)table Table 4
Fig. 7(p. 12)figure Fig. 7
Fig. 10(p. 13)figure Fig. 10
Fig. 11(p. 13)figure Fig. 11
Fig. 8(p. 13)figure Fig. 8
Fig. 9(p. 13)figure Fig. 9
Fig. 12(p. 14)figure Fig. 12
Fig. 13(p. 15)figure Fig. 13
Fig. 14(p. 16)figure Fig. 14
Fig. 15(p. 16)figure Fig. 15
Table 5(p. 19)table Table 5
Table 6(p. 20)table Table 6
Table 7(p. 21)table Table 7

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