Search Publications
The Abundance of Ammonia in Comet P/Halley Derived from Ultraviolet Spectrophotometry of NH by ASTRON and IUE
Feldman, P. D.; Grinin, V. P.; Fournier, K. B. +1 more
From an analysis of the spatial profiles of both the NH and OH UV emissions observed by the ASTRON satellite, the ratio of ammonia-to-water production rates in Comet Halley on April 9, 1986 is derived and found to lie in the range of 0.44-0.94 percent. In order to compare this result with those based on both ground-based and in situ observations m…
Simultaneous GINGA and IUE Observations of the Seyfert Galaxy NGC 3516
Koyama, Katsuji; Halpern, Jules P.; Awaki, Hisamitsu +2 more
Simultaneous X-ray and UV observations of the Seyfert 1 galaxy NGC 3516 were carried out to investigate the connection between the variable X-ray and ultraviolet absorption features. Over a 2 week period, X-ray spectra Were obtained with Ginga, simultaneously with UV spectra from IUE. The X-ray spectrum was complex and could be fitted satisfactori…
LSIV -12 degrees 111: A Candidate Halo Proto--Planetary Nebula
Dufton, P. L.; Keenan, F. P.; Conlon, E. S. +1 more
We report on multiwavelength observations of LSIV -12 deg 111, which may be an emerging halo planetary nebula. This object was previously classified as a young emission-line B-type star, but a model atmosphere abundance analysis of high-resolution optical spectra has revealed it to be an evolved object, probably in the postasymptotic giant branch …
Hubble Space Telescope Images of the Subarcsecond Jet in DG Tauri
Yang, C.; Hartigan, P.; Kepner, J. +1 more
We have applied a new restoration technique to archival [O~I], H$\alpha$, and continuum HST images of DG~Tau. The restored [O~I] and H$\alpha$ images show that DG~Tau has a jet with a projected length of 25~AU and width $\leq$10~AU, and is already collimated at a projected distance of $\sim$~40~AU (0\farcs25) from the star. Such a narrow width and…
In-Flight Performance and Preliminary Results from the Far Ultraviolet Space Telescope (Faust) Flown on ATLAS-1
Bowyer, Stuart; Lampton, Michael; Sasseen, Timothy P. +1 more
In 1992 March the Far Ultraviolet Space Telescope was flown as part of the NASA ATLAS-1 mission. We describe the in-flight instrument performance and provide a preliminary view of some of the results. Twenty-two wide-field far-ultraviolet images were obtained. At this stage of our analysis, we have far-ultraviolet photometry for more than 4800 sou…
Far-Ultraviolet Radiation from Disk Globular Clusters
Minniti, Dante; Rich, R. M.; Liebert, James
IUE spectra obtained in a survey of the metal-rich disk system of globular clusters are presented. Significant FUV fluxes were detected in the 1200-2000-A short-wavelength (SWP) range of the IUE Observatory in several disk globular clusters. These clusters are the most metal-rich known to have an FUV flux. Three clusters show spectral energy distr…
A Spectroscopic and Photometric Study of FK Comae in 1989
Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W. +1 more
Results of an observational campaign, coordinated between visual photometry, optical spectroscopy, and UV spectroscopy, to elucidate the characteristics of FK Comae are presented. The photometry showed complicated but systematic behavior. Photospheric absorption lines were distorted by a Doppler-shifted bump caused by dark starspots resulting in s…
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. I. The Extreme Type I SMP 83/WS 35
Dopita, Michael A.; Ford, Holland C.; Evans, Ian N. +2 more
We have obtained Hubble Space Telescope Planetary Camera images in both the Hα and the [O III] λ5007 emission lines of the planetary nebula SMP 83 alias WS35, alias N66 in the Large Magellanic Cloud. By combining these results with optical and UV spectrophotometry, absolute flux measurements, and dynamical and density information, we have been abl…
A Giant X-Ray Flare on lambda Eridani (B2e)
Smith, Myron A.; Peters, Geraldine J.; Grady, Carol A. +1 more
A 30 ks observation with the ROSAT PSPC distributed over 39 hr shows that the putatively single, mild B2e star Lambda Eri emits at most times a soft X-ray flux at a rate and temperature consistent with other B stars. However, during the middle of our observations, this star's X-ray flux increased by a factor of 6 before returning to the basal leve…
The Ultraviolet Continua of Blazars: A Reconsideration of IUE Archives
Pian, E.; Treves, A.
The IUE archive data on blazars are reconsidered. They refer to 47 objects, 24 radio-strong BL Lac objects, 15 radio-weak BL Lac objects, and eight optically violently variable quasars, increasing substantially the sample examined by Ghisellini et al. (1986). For each object a dereddened spectral slope is evaluated starting from the extraction of …