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Title: Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1/HDE 226868 system

Journal Article · · Astronomy and Astrophysics
 [1];  [2];  [3];  [2];  [4];  [5];  [6];  [1];  [7];  [8];  [6]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Kavli Inst. for Astrophysics and Space Research
  2. Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States). Center for Research and Exploration in Space Science & Technology (CRESST); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States). Astrophysics Science Division
  3. Dr. Karl Remeis-Sternwarte – Astronomical Inst. and Erlangen Center for Astroparticle Physics (ECAP), Bamberg (Germany); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Max Planck Inst. for Radio Astronomy, Bonn (Germany); Dr. Karl Remeis-Sternwarte – Astronomical Inst. and Erlangen Center for Astroparticle Physics (ECAP), Bamberg (Germany)
  5. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)
  6. Dr. Karl Remeis-Sternwarte – Astronomical Inst. and Erlangen Center for Astroparticle Physics (ECAP), Bamberg (Germany)
  7. Univ. of Delaware, Newark, DE (United States). Bartol Research Inst.; Ludwig Maximilian Univ., Munich (Germany). Inst. of Astronomy and Astrophysics
  8. Univ. of Wisconsin, Madison, WI (United States). Dept. of Astronomy
+ Show Author Affiliations

Binary systems with an accreting compact object offer a unique opportunity to investigate the strong, clumpy, line-driven winds of early-type supergiants by using the compact object’s X-rays to probe the wind structure. In this paper, we analyze the two-component wind of HDE 226868, the O9.7Iab giant companion of the black hole Cyg X-1, using 4.77 Ms Rossi X-ray Timing Explorer (RXTE) observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-Abbott-Klein wind: as it does not incorporate clumping, the model does not describe the observations well. Finally, a qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could either be due to lack of a focussed wind component in the model or to a more complicated clump structure.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Dr. Karl Remeis-Sternwarte – Astronomical Inst. and Erlangen Center for Astroparticle Physics (ECAP), Bamberg (Germany); Max Planck Inst. for Radio Astronomy, Bonn (Germany)
Sponsoring Organization:
USDOE; National Aeronautics and Space Administration (NASA); Federal Ministry for Economic Affairs and Energy (BMWi) (Germany)
Grant/Contract Number:
AC52-07NA27344; SV3-73016; NAS8-03060; NNX12AE37G; NNX12AC72G; 50 OR 1113
OSTI ID:
1438677
Report Number(s):
LLNL-JRNL-741010; TRN: US1900483
Journal Information:
Astronomy and Astrophysics, Vol. 576; ISSN 0004-6361
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 30 works
Citation information provided by
Web of Science

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Cited By (8)

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Multi-time-scale X-ray reverberation mapping of accreting black holes journal January 2018
A re-establishing jet during an X-ray re-brightening of the Be/X-ray binary Swift J0243.6+6124 journal December 2018
THE SOFT STATE OF CYGNUS X-1 OBSERVED WITH NuSTAR : A VARIABLE CORONA AND A STABLE INNER DISK journal July 2016
A Comprehensive Chandra Study of the Disk Wind in the Black Hole Candidate 4U 1630-472 journal November 2019
The Soft State of Cygnus X-1 Observed with NuSTAR: A Variable Corona and a Stable Inner Disk text January 2016
Observatory science with eXTP text January 2018
A Comprehensive Chandra Study of the Disk Wind in the Black Hole Candidate 4U 1630-472 text January 2019

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
stars
Cyg X-1
binary x-rays
winds
outflows