Spectroscopic observations of some of the brighter W Ursae Majoris type contact binaries in the northern hemisphere have been obtained at a medium dispersion of 20-30 Å/mm. A computer program has been developed to process and analyse these spectra using modem digital reduction techniques in order to obtain more accurate spectroscopic data for such systems. Radial velocity measurements have provided spectroscopic mass ratios which have been compared with the values derived from light curve synthesis. The improved mass ratios have removed the discrepancy which existed between the spectroscopic and photometric values in most of the systems observed. The application of spectrum deconvolution techniques has revealed an asymmetry in the structure of two W subclass systems shown by the variation in the strength of the primary components' spectral lines. Measurement, of the relative line strengths of the two components has provided further evidence for the presence of extensive magnetic starspots on the surface of the primary component of these systems.

The bright hydrogen-deficient binary Upsilon Sgr has been studied in detail in the areas of radial velocities, flux distribution, temperature, surface gravity, composition and mass loss using the analysis of spectroscopic data. From IUE high resolution spectra the primary radial velocity orbit has been confirmed (K1 = 47.3±0.8kms−1) and the secondary radial velocity curve determined for the first time (K2 = 29.7±1.7kms−1). The orbit has been constrained to an inclination of 65 - 78°. The masses of the primary and secondary are then 3.0 ± 0.3 and 4.8 ± 0.5M☉ respectively, with an orbital separation of 230±20R☉.The primary is expected to fill its Roche Lobe at a radius of ~60R☉.Using all the available photometry and line-blanketed hydrogen-deficient model atmospheres the primary effective temperature has been determined to be 11,800±500K. IUE spectra were used to determine an extinction of E[sub]B-v = 0.20±0.05 leading to a distance of ~1400pc and a luminosity of 61,000(+11,000)/(-5,000) L☉. The long standing problem of the flux distribution has been mostly solved and little of the UV flux shortward of 1400 Å comes from a hot bright secondary. The same model atmospheres and a high resolution CCD/echelle spectrum was used to confirm the temperature (Teff= 11,750±750K) and to obtain a surface gravity of log g = 1.5±0.5. υ Sgr is ~ 99.6% helium, 0.016% H with CNO abundances indicative of advanced evolution and high main sequence mass. From profile fitting of the UV resonance lines of C, N and Si the mass-loss rate from υ Sgr is at least 2.5 x10−1°M☉yr−1. The upper limit to the mass-loss rate is 1.0 x10 −5M☉yr−1 from the lack of observed changes in the orbital parameters. The mass of the primary component and the low likely mass-loss rate indicate that the primary component will not be able to shed enough material before core collapse, an event that will be classed as a type Ib supernova. This is the first solid evidence that hydrogen-deficient binaries are progenitors of these objects although other candidates are not ruled out. The other known hydrogen-deficient binaries (KS Per, LSS 1922 and LSS 4300) have had their temperatures (12,500±500K, 12,000±500K, 12,000±1,000K) and interstellar extinctions (0.55± 0.05, 0.80±0.05, 0.90±0.10) re-determined from a flux distribution analysis. Mass-loss rates from 6 O stars, 3 Extreme Helium stars and 2 sdO stars have also been determined. The O and EHe results broadly agree with the previous determinations. Results for the 2 sdO stars, BD H-37° 1977 and BD +37 ° 442, are presented from profile fitting for the first time and indicate a mass-loss rate slightly higher than for the EHe stars.

A statistical study of the orbital elements of Spectroscopic Binary Systems is undertaken with attention given to the distribution of ω, the longitude of periastron, and the observed distribution of orbital eccentricities and periods. Selection effects are taken into account in both cases. Test results indicate that the major non-uniformities previously found by other investigators for the distribution of u have been reduced or eliminated for certain categories of data. A positive correlation is discovered for the observed tabulation of periods and eccentricities. The latter result is viewed with caution, due to certain criteria established in the analysis. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Includes abstract. Bibliography: leaves (8-1)-(8-10)

Thesis (Ph. D.)--University of Adelaide, 1988. / Includes abstract. Includes bibliographical references (leaves (8-1)-(8-10)).

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, August 1999. / Includes bibliographical references. Also available on the Internet.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (vol. 2, leaves 780-785).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 178-184). Available also in a digital version from Dissertation Abstracts.

The application of the discrete Fourier transform to the determination of the frequency content of unevenly-sampled astronomical time series is discussed, and an interactive computer package which incorporates a variety of power-spectrum and time-domain techniques is described. A frequency analysis of the light curves of two hot, extreme helium stars, BD-9°4395 and HD160641, shows that their photometric variability is caused by non-radial pulsation. Spectroscopic evidence in support of non-uniform mass loss is presented for BD-9°4395. Spectroscopic and photometric observations of two early-type eclipsing binary systems, AL Sculptoris and DM Persei, have been analysed to yield their absolute dimensions. AL Scl is found to be a detached system in which both components rotate faster than synchronism. The origin of distortions in its light curve is unclear. DH Per is shown to be part of a triple system in which the third component is most probably a late-B star in a 98-day orbit with a semi-major axis of 0.9 A.U. The binary system is confirmed to be semi-detached and to have evolved through a phase of rapid mass transfer. DH Per joins a small group of massive, semi-detached systems whose characteristics differ significantly from the classical Algols, and which may result from case-A, mass-transfer processes. Spectroscopic and photometric observations of the F4V star HD123058 do not support the hypothesis that it is a binary system. Broad lines in its spectrum are attributed to a somewhat enhanced rotation rate, and the star is shown to be essentially unevolved. The derivation of the equation of condition in Sterne's rigorous method for the analysis of the spectroscopic elements of binary systems, and its modification for incorporating observed times of minimum light into the adjustment of the elements, are outlined. A computer code for the determination of orbital elements according to this scheme is described.

No description available.