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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

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 ≡ 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 locationmore » 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.« less

Authors:
 [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)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1529832
Report Number(s):
LLNL-JRNL-761005
Journal ID: ISSN 0004-6361; 949966
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 626; Journal ID: ISSN 0004-6361
Publisher:
EDP Sciences
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Hirsch, Maria, Hell, Natalie, Grinberg, Victoria, Ballhausen, Ralf, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Dauser, Thomas, Hanke, Manfred, Kallman, Timothy R., Brown, Gregory V., and Wilms, Jörn. Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system: III. Dipping in the low/hard state. United States: N. p., 2019. Web. doi:10.1051/0004-6361/201935074.
Hirsch, Maria, Hell, Natalie, Grinberg, Victoria, Ballhausen, Ralf, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Dauser, Thomas, Hanke, Manfred, Kallman, Timothy R., Brown, Gregory V., & Wilms, Jörn. Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system: III. Dipping in the low/hard state. United States. doi:10.1051/0004-6361/201935074.
Hirsch, Maria, Hell, Natalie, Grinberg, Victoria, Ballhausen, Ralf, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Dauser, Thomas, Hanke, Manfred, Kallman, Timothy R., Brown, Gregory V., and Wilms, Jörn. Thu . "Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system: III. Dipping in the low/hard state". United States. doi:10.1051/0004-6361/201935074.
@article{osti_1529832,
title = {Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system: III. Dipping in the low/hard state},
author = {Hirsch, Maria and Hell, Natalie and Grinberg, Victoria and Ballhausen, Ralf and Nowak, Michael A. and Pottschmidt, Katja and Schulz, Norbert S. and Dauser, Thomas and Hanke, Manfred and Kallman, Timothy R. and Brown, Gregory V. and Wilms, Jörn},
abstractNote = {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.},
doi = {10.1051/0004-6361/201935074},
journal = {Astronomy and Astrophysics},
number = ,
volume = 626,
place = {United States},
year = {2019},
month = {6}
}

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