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The NextGen Model Atmosphere Grid for 3000<=Teff<=10,000 K
Baron, E.; Hauschildt, Peter H.; Allard, France
We present our NextGen Model Atmosphere grid for low-mass stars for effective temperatures larger than 3000 K. These LTE models are calculated with the same basic model assumptions and input physics as the VLMS part of the NextGen grid so that the complete grid can be used, e.g., for consistent stellar evolution calculations and for internally con…
Dust Absorption and the Ultraviolet Luminosity Density at z ~ 3 as Calibrated by Local Starburst Galaxies
Heckman, Timothy M.; Meurer, Gerhardt R.; Calzetti, Daniela
We refine a technique to measure the absorption-corrected ultraviolet (UV) luminosity of starburst galaxies using rest-frame UV quantities alone and apply it to Lyman-limit U dropouts at z~3 found in the Hubble Deep Field (HDF). The method is based on an observed correlation between the ratio of far-infrared (FIR) to UV fluxes with spectral slope …
A Reanalysis of the Ultraviolet Extinction from Interstellar Dust in the Large Magellanic Cloud
Gordon, Karl D.; Clayton, Geoffrey C.; Misselt, K. A.
We have reanalyzed the Large Magellanic Cloud's (LMC) ultraviolet (UV) extinction using data from the IUE final archive. Our new analysis takes advantage of the improved signal-to-noise ratio of the IUE NEWSIPS reduction, the exclusion of stars with very low reddening, the careful selection of well-matched comparison stars, and an analysis of the …
Ultraviolet and Multiwavelength Variability of the Blazar 3C 279: Evidence for Thermal Emission
Maraschi, L.; Chiappetti, L.; Pian, E. +13 more
The γ-ray blazar 3C 279 was monitored on a nearly daily basis with IUE, ROSAT, and EGRET for 3 weeks between 1992 December and 1993 January. During this period, the blazar was at a historical minimum at all wavelengths. Here we present the UV data obtained during this multiwavelength campaign. A maximum UV variation of ~50% is detected, while duri…
Interstellar Abundances in the Magellanic Clouds. II. The Line of Sight to SN 1987A in the Large Magellanic Cloud
Sonneborn, G.; Frisch, P. C.; York, D. G. +1 more
We have analyzed both high-resolution optical absorption-line spectra and UV spectra obtained with IUE of the LMC SN 1987A, in order to determine abundances and physical conditions in the various neutral interstellar clouds along the line of sight to the supernova (SN). We have used a flat-fielding procedure to enhance the signal-to-noise ratios (…
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I. Observations toward δ Orionis by the Interstellar Medium Absorption Profile Spectrograph
Tripp, Todd M.; Jenkins, Edward B.; Sofia, Ulysses J. +2 more
Studies of the abundances of deuterium in different astrophysical sites are of fundamental importance to answering the question about how much deuterium was produced during big bang nucleosynthesis and what fraction of it was destroyed later. With this in mind, we used the Interstellar Medium Absorption Profile Spectrograph (IMAPS) on the ORFEUS-S…
Infrared Spectroscopy of NGC 4151: Probing the Obscured Ionizing Active Galactic Nucleus Continuum
Lutz, Dieter; Netzer, Hagai; Alexander, Tal +3 more
The Infrared Space Observatory (ISO) Short-Wavelength Spectrometer4 (SWS) infrared spectroscopic observations of the nucleus of Seyfert galaxy NGC 4151, which are described in a companion paper, are used in conjunction with a compilation of UV to IR narrow emission line data to determine the spectral shape of the obscured extreme-UV continuum that…
Determining the Physical Properties of the B Stars. I. Methodology and First Results
Fitzpatrick, Edward L.; Massa, Derck
We describe a new approach to fitting the UV-to-optical spectra of B stars to model atmospheres and present initial results. Using a sample of lightly reddened stars, we demonstrate that the Kurucz model atmospheres can produce excellent fits to either combined low-dispersion IUE and optical photometry or HST FOS spectrophotometry, as long as the …
Hubble Space Telescope Observations of the Dusty Small Magellanic Cloud H II Region N88A
Garnett, D. R.; Skillman, E. D.; Dufour, R. J. +5 more
We present results from the analysis of Hubble Space Telescope Faint Object Spectrograph (FOS), WFPC1, IUE, and Cerro Tololo Inter-American Observatory 4 m observations of the morphology, physical conditions, and chemical abundances in the anomalous H II region N88A in the Small Magellanic Cloud. Not only is N88A unusual among SMC H II regions bec…
Morphology and Composition of the Helix Nebula
Dufour, R. J.; Henry, R. B. C.; Kwitter, K. B.
We present new narrowband filter imagery in Hα and [N II] λ6584, along with UV and optical spectrophotometry measurements from 1200 to 9600 Å of NGC 7293, the Helix Nebula, a nearby, photogenic planetary nebula of large diameter and low surface brightness. Detailed models of the observable ionized nebula support the recent claim that the Helix is …