On the orbital and physical parameters of the HDE 226868/Cygnus X-1 binary system

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dc.creatorIorio, Lorenzo
dc.date2007-07-24
dc.date2008-05-26
dc.date.accessioned2026-07-07T11:52:49Z
dc.date.available2026-07-07T11:52:49Z
dc.descriptionIn this paper we explore the consequences of the recent determination of the mass m=(8.7 +/- 0.8)M_Sun of Cygnus X-1, obtained from the Quasi-Periodic Oscillation (QPO)-photon index correlation scaling, on the orbital and physical properties of the binary system HDE 226868/Cygnus X-1. By using such a result and the latest spectroscopic optical data of the HDE 226868 supergiant star we get M=(24 +/- 5)M_Sun for its mass. It turns out that deviations from the third Kepler law significant at more than 1-sigma level would occur if the inclination i of the system's orbital plane to the plane of the sky falls outside the range 41-56 deg: such deviations cannot be due to the first post-Newtonian (1PN) correction to the orbital period because of its smallness; interpreted in the framework of the Newtonian theory of gravitation as due to the stellar quadrupole mass moment Q, they are unphysical because Q would take unreasonably large values. By conservatively assuming that the third Kepler law is an adequate model for the orbital period we obtain i=(48 +/- 7) deg which yields for the relative semimajor axis a=(42 +/- 9)R_Sun. Our estimate for the Roche's lobe of HDE 226868 is r_M = (21 +/- 6)R_Sun.
dc.descriptionLatex2e, 7 pages, 1 table, 4 figures. To appear in ApSS (Astrophysics and Space Science)
dc.identifierhttps://arxiv.org/abs/0707.3525
dc.identifierhttp://arxiv.org/abs/0707.3525
dc.identifierAstrophys.SpaceSci.315:335-340,2008
dc.identifierdoi:10.1007/s10509-008-9839-y
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/204315
dc.subjectGeneral Relativity and Quantum Cosmology
dc.subjectAstrophysics
dc.titleOn the orbital and physical parameters of the HDE 226868/Cygnus X-1 binary system
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