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The Orbit and Companions of the Classical Cepheid FF AQL
Evans, Nancy Remage; Teays, Terry J.; Welch, Douglas L. +1 more
New radial velocities of the classical Cepheid FF Aql have been obtained and combined with previous observations to provide a revised orbit. A companion has been detected at 1800 A in IUE spectra with a spectral type of A9 V to F3 V. If the Cepheid has an evolutionary mass, then the mass ratio is M1/M2 = 3.8. A companion recently detected by speck…
A New Method to Determine the Interstellar Reddening toward WN Stars
Conti, Peter S.; Morris, Patrick W.
The emission lines in Wolf-Rayet stars may be utilized to determine the absorption properties of their line-of-sight interstellar medium. One can measure the line strengths both in terms of the equivalent widths (in units of the continuum) and fluxes. In general, in a comparison of two lines, the equivalent width ratio is extinction independent; i…
IUE Observations of WX Ceti in Outburst
Downes, Ronald A.
IUE observations of the peculiar dwarf nova WX Ceti roughly two weeks into a rare outburst, the first since 1963, are obtained. The SWP and LWP observations are very similar to other erupting dwarf novae, both in the line and continuum spectrum. The C IV 1549 A doublet displays blueshifted absorption, indicating the presence of a wind which has a …
Optical Variability of Extragalactic Objects Used to Tie the HIPPARCOS Reference Frame to an Extragalactic System Using Hubble Space Telescope Observations
Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel
Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65% are optical v…
Ultraviolet Colors as Age Indicators for LMC Clusters
Freeman, K. C.; Meurer, Gerhardt R.; Cacciari, C.
Empirical correlations are found between log ages (logτ) intrinsic ultraviolet colors C(18 - 31)_0_ and C(25 - 31)_0_ for 27 LMC clusters, where log τ is on the uniform age scale of Elson correlations as age indicators for LMC clusters and other stellar populations are discussed. The results are partially based on a new calibration of log τ vs the…
The Dynamical Mass of S MUSCAE
Cottrell, P. L.; Wallerstein, George; Bohm-Vitense, Erika +1 more
The amplitudes and phase relations of pulsational velocities of the Cepheid S Muscae, measured for lines originating at different atmospheric depths, are investigated. A mass M(A) = 4.4 + or - 0.5 solar masses is found for the Cepheid; however, the Cepheid is the evolved star and should have a mass larger than that of its companion. If the measure…
VLBI and Optical Astrometry of Southern Extragalactic Radio Sources and Radio Stars
White, Graeme L.; Jauncey, David L.; Lestrade, Jean-Francois +3 more
Mark III very long baseline interferometry (VLBI) has been used to determine the positions of ten compact extragalactic radio sources in the southern hemisphere. These positions are relative to the Jet Propulsion Laboratory VLBI celestial reference frame and are accurate at the 0.01" level, more than an order of magnitude improvement compared to t…
Coordinated Optical and Ultraviolet Observations of DH Leo
Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W. +4 more
Results are reported from contemporaneous KPNO optical spectroscopy, IUE UV spectroscopy, and KPNO R photometry of the DH Leo triple system in spring 1987. The data are presented in tables, graphs, and spectral phase images and discussed in detail. The H-alpha, H-beta, H-gamma, H-delta, and Ca II H and IRT lines are found to have excess emission, …
Rapid Line Variations in the Far-Ultraviolet Spectrum of 21 Com. I. The 1979 Event
Monier, R.
An analysis of archival IUE spectra of 21 Com revealed an instance of large and rapid flux variations on a time scale of 1 hr which occurred on November 15, 1979. Deep and broad features developed in less than 60 min and vanished in about 45 min shortwards of 1720 A. The 1979 event is thought to reflect a transient and abrupt change in the outer l…
A Search for Evidence of Past and Ongoing Mass Loss in the Hot DO Degenerates PG 1159-035, PG 1034+001, and KPD 0005+5106
Sion, Edward M.; Fritz, Matthew L.; Leckenby, Henry J.
The results are reported of a search for evidence of mass loss from three very hot, helium-rich degenerate stars, PG 1034 + 001, PG 1159 - 035, and KPD 0005 + 5106, based upon a search for weak, velocity-displaced line features in high-resolution IUE spectra. The search was entirely negative for PG 1159 - 035 and resulted in the detection of Si IV…