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SN 1992A: Ultraviolet and Optical Studies Based on HST, IUE, and CTIO Observations

Suntzeff, N. B.; Fransson, Claes; Challis, Peter M. +18 more

The Type Ia supernova SN 1992A in the 50 galaxy NGC 1380 was observed as a target of opportunity by the International Ultraviolet Explorer (IUE) and with great alacrity by the Hubble Space Telescope (HST). Here we present the HST and lUE spectra and photometry that we obtained, as well as optical spectra obtained at the Cerro Tololo Inter-American…

Lithium and Rapid Rotation in Chromospherically Active Single Giants

Fekel, Francis C.; Balachandran, Suchitra

The rotational velocities presently obtained via spectroscopic observations of a group of moderately rapidly rotating, chomospherically active single giants indicate that Gray's (1989) rotostat hypothesis requires modification. Their rapid rotation appears to be due to high Li abundances, and results in increased chromospheric activity. A scenario…

Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304. I. The IUE Campaign

Maraschi, L.; Chiappetti, L.; Tagliaferri, G. +26 more

Daily monitoring of PKS 2155 - 304 with the IUE satellite throughout 1991 November has revealed dramatic, large-amplitude, rapid variations in the ultraviolet flux of this BL Lac object. Many smaller, rapid flares are superposed on a general doubling of the intensity. During the 5^d^ period when sampling was roughly continuous, the rapid flaring h…

A Determination of the Distance to the High-Velocity Cloud Complex M

Kuntz, K. D.; Danly, Laura; Albert, C. E.

Variations of the Ultraviolet Fe II and Balmer Continuum Emission in the Seyfert Galaxy NGC 5548

Filippenko, A. V.; Netzer, H.; Shapovalova, A. I. +13 more

We present measurements of the Balmer continuum/Fe II emission blend (the "small blue bump") between 2160 and 4130 A in the Seyfert galaxy NGC 5548. The measurements are from spectra obtained as part of the combined space-based and ground-based monitoring program of this object in 1988- 1989. An iterative scheme is used to determine and subtract t…

Winds from Accretion Disks: Ultraviolet Line Formation in Cataclysmic Variables

Shlosman, Isaac; Vitello, Peter

Winds from accretion disks in cataclysmic variable stars are ubiquitous. Observations by IUE reveal P Cygni-shaped profiles of high-ionization lines which are attributed to these winds. We have studied the formation of UV emission lines in cataclysmic variables by constructing kinematical models of biconical rotating outflows from disks around whi…

The Hot Stellar Component in Elliptical Galaxies and Spiral Bulges. I. The Far-Ultraviolet Spectrum of the Bulge of M31

Ferguson, Henry C.; Davidsen, Arthur F.

We present a spectrum of the bulge of M31 from 1850 A to the Lyman limit measured through a 9" X 116" aperture by the Hopkins Ultraviolet Telescope (HUT) during the Astro-1 space shuttle mission in 1990 December. Apart from airglow, no significant emission features are present in the spectrum. A search for stellar absorption features reveals sever…

Synthetic UV Lines of Si IV, C IV, and He II from a Population of Massive Stars in Starburst Galaxies

Robert, Carmelle; Heckman, Timothy M.; Leitherer, Claus

We present the first results of our study of the massive star population in starburst galaxies based on UV data. We have synthesized the Si IV 1400, C IV 1550 and He II 1640 lines for both a continuous and an instantaneous burst of star formation with approximately solar chemical composition. Our code uses the latest generation of stellar evolutio…

Spectrophotometry of Wolf-Rayet Stars. I. Continuum Energy Distributions

Massey, Philip; Vacca, William D.; Conti, Peter S. +2 more

All available low-resolution IUE spectra are assembled for Galactic, LMC, and SMC W-R stars and are merged with ground-based optical and NIR spectra in order to collate in a systematic fashion the shapes of these energy distributions over the wavelength range 0.1-1 micron. They can be consistently fitted by a power law of the form F(lambda) is app…

On the Lyman-Alpha Emission of Starburst Galaxies

Valls-Gabaud, David

Nearby starburst galaxies have consistently shown anomalous Lyα/Hβ ratios. By reanalyzing the published IUE/optical observations, we show that most starbursts present a normal Lyα emission, consistent with case B recombination theory, provided extinction laws appropriate to their metallicities are used. This implies that extinction is more importa…