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A Survey of Chromospherically Active Stars
Fekel, F. C.; Henry, G. W.; Moffett, T. J.
Photometric and/or spectroscopic observations have been obtained of 52 late-type stars which are suspected or known to be chromospherically active. Although not all types of observations were obtained for each star, these observations include all-sky BVRI Johnson photometry, ultraviolet spectrograms, low-dispersion blue-wavelength spectrograms, an…
Narrow Absorption Components and Variability in Ultraviolet P Cygni Profiles of Early-Type Stars
Howarth, I. D.; Prinja, R. K.
An extensive set of velocity and column density measurements of both narrow absorption components and 'underlying' P Cygni profiles is presented for a sample of 21 main-sequence, giant, and supergiant stars with spectral types B1-O4, selected as having at least one of the NV, Si IV, and CIV resonance doublets unsaturated. To study variability char…
Ultraviolet Extinction toward Five Open Clusters, and the Accuracy of IUE Extinction Measurements
Fitzpatrick, E. L.; Massa, D.
The UV extinction curves of 33 main-sequence B stars in five open clusters are presented and analyzed. An analytic fitting function is introduced which represents the observed curves and codifies the structure of the 2175 A extinction bump. A set of extinction parameters are also defined which describe the shape of the far-UV extinction. These dat…
Ultraviolet Variability and Mass Expulsion from R Aquarii
Hollis, J. M.; Kafatos, M.; Michalitsianos, A. G.
Ultraviolet spectra in the 1200-3200 A range indicate that the extended nebular features which resemble a jet in the peculiar variable R Aquarii (M7e + pec) increased in excitation in 1985. The emission properties of the compact H II region that surrounds the unresolved binary, and those of the extended nebular jet, have been analyzed from low-res…
The Statistical Equilibrium of Hydrogen and Helium in a Radiation Field, with an Application to Interpreting Wolf-Rayet Spectra
Bhatia, A. K.; Underhill, A. B.
A 70-level model helium atom which includes singly and doubly excited states of He I and a 17-level model hydrogen atom are used to solve the equations of statistical equilibrium for helium and hydrogen in a radiation field. The plasma has a velocity gradient, and densities and temperatures typical for the mantles of Wolf-Rayet stars. The emission…
Ultraviolet Observations of Be Stars. II. Superionization in Be Stars of Different Spectral Types
Peters, Geraldine J.; Marlborough, J. M.
The results of an investigation of the dependence of the strength/presence of lines from superionized species (N V, C IV, Si IV) on spectral type and v sin i in the ultraviolet spectra of Be stars are presented. No evidence is found for N V in stars later than B2; this apparent absence may, however, simply reflect problems with the IUE reduction p…
The Ultraviolet Spectrum of Procyon. I. The Atlas from 2030 to 2371 Angstrom
Kondo, Y.; van der Hucht, K. A.; Castelli, F. +2 more
The high-resolution ultraviolet spectrum of Procyon (F5 IV-V) in the range 2030-2371 A is analyzed by using BUSS VIII and IUE data. A detailed identification is performed with the synthetic spectrum method. The theoretical spectrum has been computed with a Kurucz blanketed model, and using an extended and updated version of the Kurucz and Peytrema…