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Hot Evolved Objects in Different Parent Galaxies: The Stellar Winds of Three Planetary Nebula Nuclei in the Large Magellanic Cloud
Bianchi, Luciana; Vassiliadis, Emanuel; Dopita, Michael
Three planetary nebulae in the Large Magellanic Cloud (LMC) were observed with the Faint Object Spectrograph on board the Hubble Space Telescope. Their central stars display P Cygni-like features in the ultraviolet. We modeled these profiles to derive the stellar wind velocities. The wind velocities of the LMC planetary nebula nuclei (PNNs) are co…
Hubble Space Telescope Spectroscopy of the Carbon Star TX Piscium
Robinson, Richard D.; Johnson, Hollis R.; Querci, Francois +5 more
Ultraviolet spectra obtained with the Hubble Space Telescope of the carbon star TX Piscium (HR 9004) are presented, along with analysis providing information on its outer atmosphere, including flow and turbulent velocities, line formation mechanisms, and variations with time. Both thermal (collisionally excited) and fluorescent emission from the c…
Ultraviolet and Optical Observations of Hen 1213, Hen 1341, and Hen 1761
Feibelman, W. A.; Gutiérrez-Moreno, A.; Moreno, H. +1 more
We present UV observations of the symbiotic stars Hen 1213, Hen 1341, and Hen 1761, made almost simultaneously with optical observations during 1995; previous optical observations were made during 1987 and 1991. The UV spectrum of Hen 1213 was badly affected by background radiation, and only a rough description of the spectrum could be given here;…
The Extremely Active Single Giant 1E 1751+7046 = ET Draconis: Revised Properties and a Reevaluation of Its Evolutionary Status
Guinan, Edward F.; Hrivnak, Bruce J.; Fekel, Francis C. +1 more
New spectroscopic observations have resulted in significant revisions to several of the orginally published properties of the X-ray bright, chromospherically active star 1E 1751+7046: the spectral classification has been revised from K5 IV to K0 III, v sin i from 30-40 km s-1 to 23 km s-1, and the reported nondetection of the…
Convection, Thermal Bifurcation, and the Colors of A Stars
Simon, Theodore; Landsman, Wayne B.
Broadband ultraviolet photometry from the TD-1 satellite and low-dispersion spectra from the short wavelength camera of IUE have been used to investigate a long-standing proposal of Böhm-Vitense that the normal main-sequence A and early-F stars may divide into two different temperature sequences: (1) a high-temperature branch (and plateau) compris…
Temperature and Velocity Diagnostics of the Red Rectangle from UV Spectra of CO and C I
Lauroesch, James T.; Sitko, Michael L.; Glinski, Robert J. +1 more
The UV spectrum of the Red Rectangle and its central source, HD 44179, was examined using the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST). Spectra have been obtained of the 0-0, 0-1, and 0-2 vibronic bands of the CO fourth positive system, the 1657 Å C I multiplet, and the 1931 Å C I line. All of the lines and b…
A Detailed Comparison of Hubble Space Telescope Faint Object Spectrograph and IUE Ultraviolet Spectra of Selected Seyfert Nuclei
Koratkar, Anuradha; Evans, Ian; Pesto, Sharon +1 more
Despite the contributions of the Hubble Space Telescope Faint Object Spectrograph (FOS) to the archive of UV observations of active galactic nuclei, the vast majority of UV reference data were obtained using the International Ultraviolet Explorer (IUE) satellite. These data remain important since they provide historical information about the inten…
Analysis of Optical and Ultraviolet Spectroscopy of the DAZ White Dwarf G74-7
Bergeron, P.; Wesemael, F.; Billères, M. +1 more
We present new spectroscopic and photometric observations of the cool DAZ white dwarf G74-7. These data are combined with archival HST Faint Object Spectrograph data covering the range 1700-3200 Å, allowing estimates of the Ca, Mg, and Fe abundances in this object. Our analysis suggests that G74-7 is a hydrogen-rich star of normal gravity, with T<…
A Transition Disk Model Fit for the Broadband X-Ray Spectrum of Cygnus X-1
Rao, A. R.; Misra, R.; Melia, F. +1 more
The broadband (2-500 keV) data for Cygnus X-1 from observations by EXOSAT, OSSE, and the XMPC balloon, have been fitted to the transition disk model. In this model the emission is from the inner region of an accretion disk where the temperature is a rapidly varying function of radius and the radiative mechanism is saturated Comptonization. We fit …
Far-Ultraviolet Observations with the Voyager Ultraviolet Spectrometer: New Evidence for Interacting Winds in Symbiotic Systems
Leahy, D. A.; Li, P. S.
The interacting winds model has been used to explain many observational phenomena of symbiotic systems and planetary nebulae successfully. New observational results on seven symbiotic systems, obtained by the ultraviolet spectrometer (UVS) on board of spacecrafts Voyager 1 and Voyager 2, provide strong new evidence supporting the interacting winds…