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

Miskovicova I, Hell N, Hanke M, Nowak MA, Pottschmidt K, Schulz NS, Grinberg V, Duro R, Madej OK, Lohfink AM, Rodriguez J, Bel MC, Bodaghee A, Tomsick JA, Lee JC, Brown GV, Wilms J (2016)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Publisher: EDP Sciences

Book Volume: 590

Article Number: A114

DOI: 10.1051/0004-6361/201322490

Abstract

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. 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.

Authors with CRIS profile

Involved external institutions

Massachusetts Institute of Technology (MIT) United States (USA) (US) University of Maryland, Baltimore County United States (USA) (US) Radboud University Nijmegen Netherlands (NL) University of Cambridge United Kingdom (GB) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot France (FR) Rechenzentrum Garching der Max-Planck-Gesellschaft (MPCDF) / Max Planck Computing & Data Facility Germany (DE) Georgia College & State University (GCSU) United States (USA) (US) University of California, Berkeley United States (USA) (US) Harvard University United States (USA) (US) Lawrence Livermore National Laboratory United States (USA) (US)

How to cite

APA:

Miskovicova, I., Hell, N., Hanke, M., Nowak, M.A., Pottschmidt, K., Schulz, N.S.,... Wilms, J. (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. Astronomy & Astrophysics, 590. https://dx.doi.org/10.1051/0004-6361/201322490

MLA:

Miskovicova, Ivica, et al. "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." Astronomy & Astrophysics 590 (2016).

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