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Intrinsic parameters of galactic luminous OB stars.
Butler, K.; Kudritzki, R. P.; Herrero, A. +3 more
We present the results of a spectroscopic analysis of 25 galactic luminous OB stars. The gravities are in general lower than previously assumed, especially for giants. The helium abundances are also higher than normal in many cases. Using data from the spectroscopic analysis, radii, luminosities and masses are derived. The observed wind terminal v…
Observations of Highly Ionized Gas in the Galactic Halo
Sembach, Kenneth R.; Savage, Blair D.
A sample of high-quality sight lines is studied by means of IUE spectra to study the formation of Si IV, C IV, and N V in the Galaxy and constrain the mechanisms of halo gas formation. High-dispersion IUE spectra are taken for 12 objects to give combined spectra for studying the halo gas along the sight lines. N V absorption is reported in 10 of t…
NGC 1705. I. Stellar Populations and Mass Loss Via A Galactic Wind
Freeman, K. C.; Meurer, Gerhardt R.; Dopita, Michael A. +1 more
We present a detailed multi-waveband study of the galaxy NGC 1705. The data include optical and ultraviolet spectroscopy, optical and infrared photoelectric aperture photometry, narrowband and broadband images, H I spectra, and data from the IRAS point source catalog. NGC 1705 is shown to be a nearby (D~5 Mpc for H_0_ = 75 km s^-1^ Mpc^-1^) nuclea…
Reconstruction of the accretion disk in six cataclysmic variable stars.
Rutten, R. G. M.; van Paradijs, J.; Tinbergen, J.
The maximum-entropy eclipse-mapping algorithm is used to reconstruct images of the accretion disks of the novalike variable stars RW Tri, UX UMa, SW Sex, LX Ser, V 1315 Aql, and V363 Aur. The 2D disk intensity maps deduced from the light curves reveal the size of the disk and its radial intensity dependence. Black-body temperature maps deduced fro…
Correlated Hard X-Ray and Ultraviolet Variability in NGC 5548
Nandra, K.; Clavel, J.; Reichert, G. A. +7 more
We present the result of a series of contemporaneous (within one day) hard X-ray (Ginga) and ultraviolet (IUE) observations of the Seyfert 1 galaxy NGC 5548. Nine of these observations were carried out over a period of 51 days in 1990 May-July, and two in 1989. An additional simultaneous IUE-EXOSAT observation obtained on 1984 May 21 is also analy…
X-Ray--heated Models of Stellar Flare Atmospheres: Theory and Comparison with Observations
Hawley, Suzanne L.; Fisher, George H.
A sequence of five model atmospheres consisting of the photosphere, chromosphere, and transition region is computed. The models represent the response of the gas in a magnetically confined loop to intense flare energy release. It is concluded that the structure of the flare transition region is consistent with the conductive heating balancing opti…
Analysis of the Photospheric Epoch Spectra of Type IA Supernovae SN 1990N and SN 1991T
Kirshner, Robert P.; Leibundgut, Bruno; Sonneborn, George +3 more
An analysis of the photospheric epoch optical and UV spectra (obtained with the IUE satellite) of Type Ia supernovae SN 1990N and SN 1991T is presented. To perform the analysis, synthetic spectra calculated using an LTE radiative transfer procedure and white dwarf explosion models of Type Ia supernovae were fitted to the observations. For both sup…
Errors Associated with Fitting Gaussian Profiles to Noisy Emission-Line Spectra
Ayres, Thomas R.; Lenz, Dawn D.
Landman, Roussel-Dupre, and Tanigawa developed prescriptions to predict profile fitting errors for Gaussian emission lines perturbed by white noise. We show that their scaling laws can be generalized to more complicated signal-dependent "noise models" of common astronomical detector systems. (SECTION: Instrumentation and Data Analysis)
A Multiwavelength Study of the Supernova Remnant N49 in the Large Magellanic Cloud
Blair, William P.; Raymond, John C.; Long, Knox S. +1 more
Using the 2.5 m du Pont telescope at Las Campanas, the International Ultraviolet Explorer satellite, and archival high-resolution imager X-ray data from the Einstein Observatory, we present a detailed imaging and spectroscopic study of the supernova remnant (SNR) N49 in the Large Magellanic Cloud. Although the X-ray and optical morphology of N49 a…
Spectral Synthesis in the Ultraviolet. IV. A Library of Mean Stellar Groups
O'Connell, Robert W.; Burstein, David; Wu, Chi-Chao +1 more
A library of mean UV stellar energy distributions is derived from IUE spectrophotometry of 218 stars. The spectra cover 1230-3200 A with a spectral resolution of about 6 A. They have been corrected for interstellar extinction and converted to a common flux and wavelength scale. Individual stars were combined into standard groups according to their…