The results of a long term monitoring program on the massive X-ray binary Cygnus X-1, whose constituents are believed to consist of a normal 0 star primary and a black hole companion, are presented. Spectra of this system were collected between 1980 and 1984 using a Reticon detector. The resulting absorption line radial velocity (RV) curve is characteristic of a single line spectroscopic binary. These velocities were combined with those available in the literature to determine an orbital period of 5.59977 ± 0.00001 days. A P/P ≃ 10⁻⁵ day⁻¹ was found from analysis of all available velocity measures. This change in the period is larger than that expected as a result of mass loss from the primary or from- models of the system in which large mass transfer rates occur between the components. A fit of the orbital motion of the primary to the RV curve gives a K = 75.0 ± 1 km/s and no significant eccentricity. The vsini of the primary was found, using the fourier transform technique, to be 94.3 km/sec. This is substantially smaller than the literature value of vsini = 140 km/sec. The value of the K and vsini allow the ratio mp/mx to be determined as ≃ 2.0 . The equivalent width of Hƴ allows the absolute magnitude of the primary to be estimated at -6.5 ± 0.2 . A comparison of the spectrum of the primary to those of an array of standards allows the spectral type to be given as between 09.5 and 09.7 I . This spectral type is consistent that the primary is a normal star of mass ≃ 20 M⊙. The mass of the secondary is therefore 10 ± 3 Mʘ. Measurement of the interstellar lines to obtain an independent E(B-V) reveals that the interstellar line strength per unit E(B-V) is lower than in any other direction in the sky. Stars for which velocity-excitation slopes and mass loss estimates, from UV line profile modeling and/or radio free-free emission measures, are available in the literature were collated. An empirical fit to this material allowed the mass loss rate for HDE 226868 (the primary of Cygnus X-1) to be estimated at 5.7 ± 2 x 10⁻⁶ M/year. The He II λ4686 and Hɑ lines are found in emission. After removal of the contribution to the line profile from the primary the radial velocity curve of the residual He II λ4686 line is found to have small scatter from a smooth fit ( ± 10 km/sec ) with no significant eccentricity. No sizeable variation in the K amplitude at different epochs was found contrary to a previous investigation and the origin of the emission is thus apparently fixed and stable. A phase lag of 130° is measured between the absorption and emission velocity curves and thus the simple interpretation of the emmision originating near the secondary can not be correct. The He II emission equivalent width, corrected for the underlying primary absorption, shows strong modulation (30%) over the 5.6 day orbital period. This variation is probably the result of the profile of the primary varying with which face of the star is directed towards the observer. During two separate observing sessions in 1982 the He II equivalent widths were found to be 40% and 15% larger than the mean of all other observations while still showing the same variation with orbital phase. Such a change has been seen once before and may be associated with transitions to the X-ray high state. The Hƴ and Hβ lines show a 20% variation on the 294 day X-ray period in the sense of largest equvalent widths at X-ray minimum ( 0 phase ). The Balmer lines are a composite of an absorption component from the primary and a weak emission component. This is best explained by variations in the outflow from the star, which is the source of both the emission component and the X-ray flux via accretion. Such variations may be the result of pulsation of the primary. The Hɑ line profile has been decomposed into three components; the absorption component from the primary, emission from a shell with an inner radius 1.4 times that of the primary, arid a component with properties similar to the He II λ4686 line. The great width of the Hɑ line, previously explained as being the result of rotation of the disc, is instead shown to be the result of superposition of these components. The origin of the He II λ4686 emission is explained by assuming that a stellar wind enhanced in the direction of the secondary is completely ionized within a volume surrounding the secondary. The He II between the edge of this volume and the surface of the primary is enhanced as a result of X-ray heating and ionization. Model profiles appear in reasonable agreement with high dispersion spectra. The obvious explanation for the orbital variation in the He II line is that X-ray heating of the side of the primary facing the secondary produces a change in the effective temperature. Calculation of the size of this effect reveals that it is too small to explain the changes observed. X-ray observations made with EXOSAT with excellent time resolution allowed timing of the X-ray absorption features seen near orbital phase zero. Simultaneous X-ray spectra allowed an estimate of their column density as 2.0 x 1023 cm⁻². Two scale lengths of dips were found of 10⁸ and 10¹¹ cm. These values are in good agreement with theoretical predictions for the sizes of inhomogeneties in high mass loss stellar winds. The location of the material producing the absorption dips was calculated as being ≃ 4-8 R⊙ from the X-ray source. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Massive stars profoundly influence the evolution of the Universe, from Galactic dynamics and structure to star formation. They are often found with bound companions. However, our knowledge of O-type multiple systems with periods in the range from years to thousands of years is incomplete due their great distances. We present results from a high angular resolution survey to find angularly resolved companions using the Fine Guidance Sensor (FGS) on the Hubble Space Telescope and using ground-based adaptive optics at Gemini North. We observed 75 O- and early B-type stars in Cyg OB2 and determined that 42% of the sample have at least one companion that meets a statistical criterion for gravitationally bound status. As a case study, we present an examination of high resolution, ultraviolet spectroscopy from Hubble Space Telescope of the photospheric spectrum of the O-supergiant in the massive X-ray binary HDE 226868 = Cyg X-1. We analyzed the ultraviolet and ground-based optical spectra to determine the effective temperature and gravity of the O9.7 Iab supergiant. Using non-LTE, line blanketed, plane parallel models from the TLUSTY grid, we obtain Teff = 28.0 +/- 2.5 kK and log g > 3.00 +/- 0.25, both lower than found in previous studies. The optical spectrum is best fit with models that have enriched He and N abundances. We fit the model spectral energy distribution for this temperature and gravity to the UV, optical, and IR fluxes to determine the angular size of and extinction towards the binary. By assuming that the supergiant rotates synchronously with the orbit, we can use the radius - distance relation to find mass estimates for both components as a function of the distance and the ratio of stellar to Roche radius. Our results indicate masses of 23+8-6 solarmasses for the supergiant and 11+5-3 solarmasses for the black hole. These results agree with subsequent mass estimates Orosz et al. (2011) based on the trigonometric parallax distance measurements of Reid et al. (2011). The results of this survey provide fundamental information on the impact of environment on massive binaries and also the role multiplicity has on massive star formation and evolution.