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HST Observations of NGC 4395, the Least Luminous Seyfert 1 Nucleus: Evidence against the Starburst Hypothesis for Broad-lined Active Galactic Nuclei

Filippenko, Alexei V.; Ho, Luis C.; Sargent, Wallace L. W.

We have used the Hubble Space Telescope to obtain ultraviolet spectra and optical images of the nucleus of NGC 4395, the least luminous and nearest known type 1 Seyfert. The spectrum closely resembles those of normal Seyfert nuclei; narrow emission lines span a wide range of ionization, and the permitted lines have broad wings. If parameterized by…

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…

Detection of Boron, Cobalt, and Other Weak Interstellar Lines toward zeta Ophiuchi

Lambert, D. L.; Federman, S. R.; Gilliland, R. L. +1 more

Numerous weak lines from interstellar atomic species toward Zeta Ophiuchi were observed with the Goddard High-Resolution Spectrograph. Of particular note are the first interstellar detection of cobalt and the detection of boron in this sight line. These measurements provide estimates for the amount of depletion for the two elements. Boron, a volat…

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…

Ultraviolet Transitions of Low Condensation Temperature Heavy Elements and New Data for Interstellar Arsenic, Selenium, Tellurium, and Lead

Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +1 more

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…

The EXOSAT Medium Energy (ME) Sample of Dwarf Novae

Mukai, K.; Shiokawa, K.

We present our analysis of the EXOSAT medium energy (ME) archival data on dwarf novae. Many dwarf novae were observed with EXOSAT; unfortunately, a significant fraction resulted in nondetection or marginal detection with the ME instrument. Our analysis of the brightest dwarf nova, SS Cyg, shows little correlation between the count rate and the har…

Does a Luminosity-dependent Continuum Shape Cause the Baldwin Effect?

Zheng, Wei; Malkan, Matthew A.

We combine ground- and space-based spectrophotometry to measure the luminosity dependence of the shape of the optical/UV continuum in 108 QSO and 37 Seyfert 1 nuclei. The UV continuum at 1250 Å in high-luminosity QSOs, compared with the optical continuum at 6500 Å, is over one magnitude higher than that in the less luminous Seyfert galaxies. In te…

Silicon and Carbon Abundances in the Orion Nebula

Dufour, Reginald J.; Rubin, Robert H.; Walter, Donald K.

We assess the gas-phase abundances of Si and C from our recent measurements of Si(2+), C(2+), and C(+) in the Orion Nebula by expanding on our earlier 'blister' models. The C and Si abundances are derived from new IUE high-dispersion spectra of the C(2+) 1907, 1909 A and Si(2+) 1883, 1892 A lines and archival IUE data. Gas-phase Si/C = 0.016 in th…