Search Publications
An Ultraviolet-Visible Investigation of the Globular Cluster NGC 1851
Cheng, Kwang-Ping; O'Connell, Robert W.; Bohlin, Ralph C. +8 more
Two-color ultraviolet images of the globular cluster NGC 1851 were obtained with the Ultraviolet Imaging Telescope (UIT) during the 1990 December Astro-1 Spacelab mission. A total of 133 stars are detected at 2490 A and 74 stars at 1520 A. An ultraviolet color-magnitude diagram based on the 46 well-photometered stars that appear in both images is …
High-Resolution Imaging of the Pluto-Charon System with the Faint Object Camera of the Hubble Space Telescope
Barbieri, C.; Hook, R. N.; Sparks, W. B. +8 more
Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) after the refurbishment of the telescope. The images are of superb quality, allowing the determination of radii, fluxes, and albedos. Attempts were made to improve the resolution of the already diffraction limited images by image …
The ``Monochromatic Density Diagnostic'' Technique: First Detection of Multiple Density Components in the Chromosphere of alpha Tauri
Judge, P. G.
Emission line profiles of the red giant alpha Tau, obtained by Carpenter et al. (1991) using the echelle and medium dispersion gratings of the Goddard High Resolution Spectrograph are re-examined. Ratios of monochromatic flux densities of lines of the C II) 2s2 2p(2)P0 goes to 2s2p2 (4)P multiple near 2325 A, well-…
Theoretical Modeling of GHRS Observations of the Of/WN-Type Star R136a5
Hubeny, Ivan; Heap, Sara R.; Lanz, Thierry +1 more
We present a theoretical analysis of the Hubble Space Telescope (HST) Goddard High Resolution Spectrograph (GHRS) spectrum of R136a5, an O3fWN star in the R136a cluster in 30 Doradus. Using non-LTE extended and expanding model atmospheres, we find a surprisingly high mass-loss rate dot-M = 1.8 +/- 0.5 x 10-5 solar mass/yr and an effecti…
The HST Quasar Absorption Line Key Project. IX. an Emission-Line Study of PG 2251+113
Turnshek, David A.; Schneider, Donald P.; Savage, Blair D. +9 more
We present HST and quasi-simultaneous ground-based observations of the z = 0.3252 QSO PG 2251 + 113. We find a correlation between line widths and the critical density for de-excitation of the forbidden emission lines observed in this object. We can show that this correlation also applies to the semiforbidden and possibly also the permitted lines …
Infrared Observations of Comet Austin (1990 V) by the COBE/Diffuse Infrared Background Experiment
Reach, W. T.; Lisse, C. M.; Kelsall, T. +4 more
Comet Austin was observed by the Cosmic Background Explorer (COBE)/Diffuse Infrared Background Experiment (DIRBE) with broadband photometry at 1-240 micrometers during the comet's close passage by Earth in 1990 May. A 6 deg long (6 x 106 km) dust tail was found at 12 and 25 micrometers, with detailed structure due to variations in parti…
Highly Ionized Gas in the Galactic Disk: The L = 295 degrees , B = 0 degrees Interarm Direction
Sembach, Kenneth R.
I present new high-resolution measurements of ultraviolet interstellar absorption lines toward three distant stars in the Galactic disk in the general direction l = 295 deg, b = 0 deg. The high ionization lines of Si IV and C IV toward HD 100276, HD 103779, and HD 104705 show substantial variations on angular scales of less than 1 deg, or about 50…
Ultraviolet Observations of the Accretion Disk in LMC X-3
Hutchings, J. B.; Crampton, D.; Cowley, A. P. +1 more
We report information obtained from a series of IUE low-resolution spectra and two HST UV spectra of LMC X-3. The HST spectra are used to identify disk emission lines and interstellar absorptions as well as to fit continuum models, which indicate the presence of a hot disk component. The IUE observations, mainly taken over ~1.5 years, were intende…
Observations of SN 1987A with the COSTAR-corrected Faint Object Camera
Panagia, N.; Jakobsen, P.; Macchetto, F. +1 more
New near-ultraviolet and visible [O III] observations of SN 1987A obtained 2511 and 2533 days after outburst with the Corrective Optics Space Telescope Axial Replacement (COSTAR) corrected Faint Object Camera on board the Hubble Space Telescope are presented. Even though the supernova is now very faint (m ~ 19), the new data are of dramatically hi…
Evolution of Solitary Density Waves in Stellar Winds of Early-Type Stars: A Simple Explanation of Discrete Absorption Component Behavior
Waldron, Wayne L.; Altner, Bruce; Klein, Larry
We model the evolution of a density shell propagating through the stellar wind of an early-type star, in order to investigate the effects of such shells on UV P Cygni line profiles. Unlike previous treatments, we solve the mass, momentum, and energy conservation equations, using an explicit time-differencing scheme, and present a parametric study …