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The dust around R Coronae Borealis type stars.
Holm, A. V.; Wu, C. -C.; Hecht, J. H. +1 more
Measurements taken by the International Ultraviolet Explorer spacecraft of the stars RY Sgr and R CrB have been analyzed using Mie theory. The extinction data, which show a 2400-2500 A peak, are consistent with a distribution of 5-60 nm glassy or amorphous carbon particles obscuring the stellar flux. The data are also fairly consistent with a clou…
Spectroscopy of the shell episode of η Car (1981-1983).
Stahl, O.; Wolf, B.; Zanella, R.
High-dispersion spectra of η Car obtained in March 1974, Dec. 1981, and Feb. 1983 have been compared. The spectrum of Dec. 1981 shows conspicuous deviations from the usual spectral appearance of η Car; all lines originating from high ionization and/or excitation levels have dramatically faded. The P Cygni characteristics of the Balmer lines are mo…
Mass loss in O-type stars : parameters which affect it.
Conti, P. S.; Garmany, C. D.
Newly determined mass loss rates are presented for sixteen O-type stars in three open clusters. Combining the data with that already in the literature, no evidence is found that the rates are different in clusters with differing galactocentric distances and compositions, at least near the sun. There is still appreciable dispersion in the relations…
Ultraviolet spectral morphology of the O stars : the remarkable luminosity dependence of the SI IV stellar wind effect.
Walborn, N. R.; Panek, R. J.
An extensive survey of ultraviolet O type spectra, by means of high-resolution data from the International Ultraviolet Explorer archives, shows a strong correlation between both the photospheric and stellar wind features, and the optical spectral types. In particular, the stellar wind effect in the Si IV resonance doublet displays a strong luminos…
Spectrophotometry of two complete samples of flat radio spectrum quasars.
Gaskell, C. M.; Baldwin, J. A.; Wampler, E. J. +1 more
Spectrophotometry of two complete samples of flat-spectrum radio quasars show that for these objects there is a strong correlation between the equivalent width of the C IV 1550 A emission line and the luminosity of the underlying continuum. Assuming Friedmann cosmologies, the scatter in this correlation is a minimum for Q(O) approximately unity. A…
A study of the dependence of MG II emission on the rotational periodsof main-sequence stars.
Hartmann, L.; Baliunas, S. L.; Duncan, D. K. +1 more
International Ultraviolet Explorer satellite measurements of the Mg II chromospheric emission from a sample of late-type dwarfs with known rotational periods are presented. The ratio of chromospheric to photospheric luminosity for the late-G and K type stars in this sample can be fitted within the probable errors by a single function of rotational…
Hot subdwarfs in detached binary systems and thick-disk cataclysmic variables from the Palomar-Green survey.
Green, R. F.; Liebert, J.; Ferguson, D. H.
A total of 19 stars from the Palomar Green (PG) survey which were found to show composite spectra, generally with a hot subdwarf primary and a cool main-sequence secondary star, are discussed. The primary components have Teff values between 27,000 and 38,000 K (Mv = +5 to +7) and log g = about 6.5, while the secondaries generally show spectral typ…
Radial velocity studies of cataclysmic binaries. II. The ultrashort period dwarf nova T Leonis.
Szkody, P.; Shafter, A. W.
Spectroscopic and photometric observations of T Leo which reveal the object to be an ultrashort period dwarf nova are presented. In particular, the analysis indicates that T Leo has an orbital period of 84.69936 (plus or minus 0.00068) minutes, which is the third shortest orbital period of any known cataclysmic variable and the shortest known for …
The chromosphere and corona of T Tauri.
Jordan, C.; Brown, A.; de M. Ferraz, M. C.
Observations of the ultraviolet spectrum of the pre-main-sequence star T Tauri have been made using the International Ultraviolet Explorer (IUE) satellite. The fluxes of the emission lines are used to make models of the temperature and density structure of the chromosphere and transition region to the corona. Several models are discussed to cover …
High-resolution IUE observations of interstellar absorption lines in the VELA supernova remnant.
Jenkins, E. B.; Wallerstein, G.; Silk, J.
Ultraviolet spectra of 45 stars in the vicinity of the Vela supernova remnant were recorded by the short-wavelength echelle spectrograph aboard the International Ultraviolet Explorer (IUE). Over one-third of the stars show interstellar absorption lines at large radial velocities (greater than 60 km/s). The mapping of these high-velocity components…