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Title: Chandra X-ray spectroscopy of focused wind in the Cygnus X-1 system: II. The non-dip spectrum in the low/hard state – modulations with orbital phase

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 thanmore » the absorber. Here, 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.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [3] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ;  [12] ;  [13] ;  [14] ;  [1]
  1. Univ. Erlangen-Nurnberg, Bamberg (Germany)
  2. Univ. Erlangen-Nurnberg, Bamberg (Germany); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  4. Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  5. Univ. Erlangen-Nurnberg, Bamberg (Germany); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  6. Univ. Erlangen-Nurnberg, Bamberg (Germany); AIT Austrian Institute of Technology GmbH, Vienna (Austria)
  7. Radboud Univ. Nijmegen, Nigmegen (The Netherlands); SRON Netherlands Institute for Space Research, Utrecht (The Netherlands)
  8. Univ. of Cambridge, Cambridge (United Kingdom)
  9. CEA/DSM-CNRS-Univ. Paris Diderot, Gif-sur-Yvette (France)
  10. Max-Planck Computing and Data Facility, Garching (Germany)
  11. Georgia College & State Univ., Milledgeville, GA (United States)
  12. Univ. of California, Berkeley, CA (United States)
  13. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  14. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-737481
Journal ID: ISSN 0004-6361
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 590; Journal ID: ISSN 0004-6361
Publisher:
EDP Sciences
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; accretion; accretion disks; stars: individual: Cyg X-1; stars: individual: HDE 226868; X-rays: binaries; stars: winds; outflows
OSTI Identifier:
1438726

Miskovicova, Ivica, Hell, Natalie, Hanke, Manfred, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Grinberg, Victoria, Duro, Refiz, Madej, Oliwia K., Lohfink, Anne M., Rodriguez, Jerome, Bel, Marion Cadolle, Bodaghee, Arash, Tomsick, John A., Lee, Julia C., Brown, Gregory V., and Wilms, Jorn. Chandra X-ray spectroscopy of focused wind in the Cygnus X-1 system: II. The non-dip spectrum in the low/hard state – modulations with orbital phase. United States: N. p., Web. doi:10.1051/0004-6361/201322490.
Miskovicova, Ivica, Hell, Natalie, Hanke, Manfred, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Grinberg, Victoria, Duro, Refiz, Madej, Oliwia K., Lohfink, Anne M., Rodriguez, Jerome, Bel, Marion Cadolle, Bodaghee, Arash, Tomsick, John A., Lee, Julia C., Brown, Gregory V., & Wilms, Jorn. Chandra X-ray spectroscopy of focused wind in the Cygnus X-1 system: II. The non-dip spectrum in the low/hard state – modulations with orbital phase. United States. doi:10.1051/0004-6361/201322490.
Miskovicova, Ivica, Hell, Natalie, Hanke, Manfred, Nowak, Michael A., Pottschmidt, Katja, Schulz, Norbert S., Grinberg, Victoria, Duro, Refiz, Madej, Oliwia K., Lohfink, Anne M., Rodriguez, Jerome, Bel, Marion Cadolle, Bodaghee, Arash, Tomsick, John A., Lee, Julia C., Brown, Gregory V., and Wilms, Jorn. 2016. "Chandra X-ray spectroscopy of focused wind in the Cygnus X-1 system: II. The non-dip spectrum in the low/hard state – modulations with orbital phase". United States. doi:10.1051/0004-6361/201322490. https://www.osti.gov/servlets/purl/1438726.
@article{osti_1438726,
title = {Chandra X-ray spectroscopy of focused wind in the Cygnus X-1 system: II. The non-dip spectrum in the low/hard state – modulations with orbital phase},
author = {Miskovicova, Ivica and Hell, Natalie and Hanke, Manfred and Nowak, Michael A. and Pottschmidt, Katja and Schulz, Norbert S. and Grinberg, Victoria and Duro, Refiz and Madej, Oliwia K. and Lohfink, Anne M. and Rodriguez, Jerome and Bel, Marion Cadolle and Bodaghee, Arash and Tomsick, John A. and Lee, Julia C. and Brown, Gregory V. and Wilms, Jorn},
abstractNote = {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. Here, 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.},
doi = {10.1051/0004-6361/201322490},
journal = {Astronomy and Astrophysics},
number = ,
volume = 590,
place = {United States},
year = {2016},
month = {5}
}