Search Publications
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…
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…
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…
Improved Calculations for the C III lambda lambda 1907,1909 and SI III lambda lambda 1883,1892 Electron Density Sensitive Emission-Line Ratios, and a Comparison with IUE Observations
Feibelman, W. A.; Keenan, F. P.; Berrington, K. A.
Atomic data are used in conjunction with the statistical equilibrium code of Dufton (1977) to calculate relative C III and Si III level populations, and hence emission-line strengths for a range of electron temperatures and densities. It is assumed that photoexcitation and deexcitaton rates are negligible in comparison with the corresponding colli…
A Magnitude-limited Survey of Cepheid Companions in the Ultraviolet
Evans, Nancy R.
Results of a magnitude-limited survey of classic Cepheids brighter than 8th mag carried out to search for hot main-sequence companions are presented. Spectra of 76 stars obtained with the IUE satellite in the 2000-3200-A region were compared with the spectra of nonvariable supergiants and also the single Cepheid Delta Cep to search for excess flux…
LY alpha Emission from Cooling Flows and Measures of the Dust Content of Rich Clusters of Galaxies
Hu, Esther M.
We tabulate Ly α and UV continuum fluxes from measurements across the emission-line regions of 10 "cooling flow" clusters of galaxies. Comparison of Ly α emission fluxes obtained with the IUE satellite with optical Balmer emission fluxes is used to demonstrate that the lines of sight to the centers of these clusters show an average excess reddenin…
A Prediction of the gamma -Ray Flux from Nova Herculis 1991
Truran, James W.; Shore, Steven N.; Sonneborn, George +3 more
UV observations made with the IUE satellite of Nova Her 1991 are presented and discussed. A distance of 3.4 kpc and reddening of 0.6 E(B-V) to Nova Her 1991 are determined by comparing its UV and optical outburst behavior with those of the extragalactic ONeMg nova LMC 1990 No. 1. Her 1991 was also detected by Rosat five days into its outburst, and…
The Nature of the Recurrent Nova T Coronae Borealis: Ultraviolet Evidence for a White Dwarf Accretor
Cassatella, Angelo; Gilmozzi, Roberto; Selvelli, Pier L.
Data from eleven years of IUE observations of T CrB during its quiescent phase suggest that a white dwarf accretor rather than a main-sequence star is the hot component of the system. The spectroscopic and photometric behavior of T CrB during the 1946 outburst actually supports the interpretation of a thermonuclear runaway event on a massive white…
Spherically Symmetric, Expanding, Non--LTE Model Atmospheres for Novae during Their Early Stages
Hauschildt, P. H.; Starrfield, S.; Wehrse, R. +1 more
In the continuum and line-blanketed models presented here, nova atmospheres are characterized by a very slow decrease of density with increasing radius. This feature leads to very large geometrical extensions so that there are large temperature differences between the inner and outer parts of the line-forming regions. The theoretical spectra show …
A Multiwavelength Study of Nova QU Vulpeculae 1984
Williams, Robert E.; Truran, James W.; Ferland, Gary J. +6 more
We have combined ground-based optical and satellite ultraviolet spectrophotometric data to study the ejected shell of Nova Vulpecula 1984 No. 2 (QU Vul). Substantial uncertainties concerning the nature of the ionizing continuum, and the role played by density inhomogeneities, now exist. Because of these uncertainties, the chemical composition is d…