The Primary orbit and the absorption-lines of HDE-226868 (Cygnus X-1)

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dc.contributor.author Ninkov, Zoran en_US
dc.contributor.author Walker, Gordon en_US
dc.contributor.author Yang, Stephenson en_US
dc.date.accessioned 2006-12-18T16:44:45Z en_US
dc.date.available 2006-12-18T16:44:45Z en_US
dc.date.issued 1987-10-01 en_US
dc.identifier.citation Astrophysical Journal 321N1 (1987) 425-437 en_US
dc.identifier.issn 1538-4365 en_US
dc.identifier.uri http://hdl.handle.net/1850/3011 en_US
dc.description This article may also be accessed on the publisher's website at: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1987ApJ...321..425N&data_type=PDF_HIGH&type=PRINTER&filetype=.pdf en_US
dc.description.abstract From Reticon spectra of ~1 A resolution taken between 1980 and 1984, the radial velocity curve of HDE 226868 is found to be characteristic of a single-line spectroscopic binary with K = 75.0 +/- 1.0 km s^-1 and e=0.0. Combining historical velocities from the literature with our own data and applying a period-folding analysis, a period of 5.59964 +/- 0.00001 days is found. These values agree well with those published by Gies and Bolton in 1982, v sin i is estimated tob e 94.3 +/- 5 km s^-1 from CFHT Reticon spectra taken at 0.1 A resolution. Assuming that the rotation of the primary is synchronized to the orbital revolution of the secondary gives a primary to secondary mass between 1.5 and 2.3. An absolute magnitude of -6.5 +/- 0.2 is derived from the equivalent width of Hy (1.5 +/- 0.1 A) and the 1985 calibration of Walker and Millward which is consistent with the spectral classification of 09.7 Iab. Assuming 20 M_ as a reasonable estimate for the mass of the primary implies a mass of 10 +/- 1 M_ for the secondary. The equivalent width of Hy and HB are 20% larger at zero phase (X-ray minimum) of the 294 day X-ray period. A variation in the outflow rate from the primary could produce variations in both the Balmer-line equivalent widths and the X-ray flux (Refer to PDF file for exact formulas). en_US
dc.description.sponsorship Z. Ninkov acknowledges the support of a Canadian Commonwealth Scholarship and Fellowship Plan Award and the facilities at the Department of Physics and Astronomy, University of Rochester where this paper was written. We are very grateful to Grant Hill and John Amor for their help in making the observations. P. Harmanec made useful comments on the manuscript, and we thank an anonymous referee for his helpful suggestions. This research was supported by funds to GAHW from the Natural Sciences and Engineering Research Council of Canada. en_US
dc.format.extent 1633832 bytes en_US
dc.format.mimetype application/pdf en_US
dc.language.iso en_US en_US
dc.publisher The University of Chicago Press en_US
dc.relation.ispartofseries vol. 321 en_US
dc.relation.ispartofseries no. 1 en_US
dc.subject Stars - individual (HDE 226868) en_US
dc.subject X-rays - binaries en_US
dc.title The Primary orbit and the absorption-lines of HDE-226868 (Cygnus X-1) en_US
dc.type Article en_US

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