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

dc.contributor.authorGrinberg, V.
dc.contributor.authorLeutenegger, M. A.
dc.contributor.authorHell, N.
dc.contributor.authorPottschmidt, Katja
dc.contributor.authorBöck, M.
dc.contributor.authorGarcía, J. A.
dc.contributor.authorHanke, M.
dc.contributor.authorNowak, M. A.
dc.contributor.authorSundqvist, J. O.
dc.contributor.authorTownsend, R. H. D.
dc.contributor.authorWilms, J.
dc.date.accessioned2023-09-06T14:02:34Z
dc.date.available2023-09-06T14:02:34Z
dc.date.issued2015-04-16
dc.description.abstractBinary 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. 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. 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.en_US
dc.description.sponsorshipSupport for this work was provided by NASA through the Smithsonian Astrophysical Observatory (SAO) contract SV3-73016 to MIT for Support of the Chandra X-Ray Center (CXC) and Science Instruments; CXC is operated by SAO for and on behalf of NASA under contract NAS8-03060. It was partially completed by LLNL under Contract DE-AC52-07NA27344, and is supported by NASA grants to LLNL and NASA/GSFC. We thank the Bundesministerium für Wirtschaft und Technologie for funding through Deutsches Zentrum für Luft- und Raumfahrt grant 50 OR 1113. M.A.N. acknowledges support from NASA Grant NNX12AE37G. R.H.D.T. acknowledges support from NASA award NNX12AC72G. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. We thank John E. Davis for the development of the slxfig module used to prepare all figures in this work and Fritz-Walter Schwarm, Thomas Dauser, and Ingo Kreykenbohm for their work on the Remeis computing cluster. This research has made use of ISIS functions (isisscripts) provided by ECAP/Remeis observatory and MIT3 . Without the hard work by Evan Smith and Divya Pereira to schedule the observations of Cyg X-1 so uniformly for more than a decade, this whole series of papers would not have been possible.en_US
dc.description.urihttps://www.aanda.org/articles/aa/abs/2015/04/aa25418-14/aa25418-14.htmlen_US
dc.format.extent11 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m23vcm-f7bz
dc.identifier.citationGrinberg, V., M. A. Leutenegger, N. Hell, K. Pottschmidt, M. Böck, J. A. García, M. Hanke, et al. “Long Term Variability of Cygnus X-1 - VII. Orbital Variability of the Focussed Wind in Cyg X-1/HDE 226868 System.” Astronomy & Astrophysics 576 (April 1, 2015): A117. https://doi.org/10.1051/0004-6361/201425418.en_US
dc.identifier.urihttps://doi.org/10.1051/0004-6361/201425418
dc.identifier.urihttp://hdl.handle.net/11603/29565
dc.language.isoen_USen_US
dc.publisherEDP Sciencesen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Center for Space Sciences and Technology
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Physics Department
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.en_US
dc.rightsAttribution 4.0 International (CC BY 4.0)*
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/*
dc.titleLong term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1/HDE 226868 systemen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0002-4656-6881en_US

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