Search Publications
Far-Ultraviolet Imaging of the Globular Cluster NGC 6681 with WFPC2
Casertano, Stefano; Ballester, Gilda E.; Crisp, David +13 more
We have imagined the globular cluster NGC 6681 in the far-UV and visible with Wide Field/Planetary Camera-2 (WFPC2) on the Hubble Space Telescope (HST). Our far-UV images show a sparsely populated and fully resolved central region, and we detect 122 stars. The far-UV to visible color-magnitude diagram shows a well-defined horizontal branch with no…
Hubble Space Telescope Fine Guidance Sensor Interferometric Observations of the Core of 30 Doradus
Lattanzi, M. G.; Bucciarelli, B.; Evans, I. N. +7 more
We present the results of the first high angular resolution observations taken with a Fine Guidance Sensor (FGS) aboard the Hubble Space Telescope (HST) of a star cluster embedded in very bright background. The strong and complex background around the R136 cluster in the 30 Dor nebula does not prevent the FGS from achieving performance close to it…
Generalized Spectral Model for 1--100 keV X-Ray Emission from Cygnus X-3 Based on EXOSAT Data
Singh, K. P.; Rao, A. R.; Chitnis, V. R. +1 more
The X-ray spectrum of the highly variable X-ray source, Cyg X-3, has so far defied a consistent explanation based on simple emission models. We have extracted two of the best data sets from the EXOSAT archives and performed a detailed spectral analysis for its 'high' and 'low' states. The analysis of the less frequently occurring 'low' state is pr…
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. II. SMP 85, A Young Planetary
Dopita, Michael A.; Ford, Holland C.; Maran, Stephen P. +6 more
We have obtained Hubble Space Telescope Planetary Camera images in the [O III] λ5007 A emission line, and FOS UV spectrophotometry of the low-excitation planetary nebula SMP 85 in the Large Magellanic Cloud. By combining these results with existing optical spectrophotometry, absolute flux measurements, and dynamical and density information, we hav…
Directivity of 100--500 keV Solar Flare Hard X-Ray Emission
Hurley, K.; Niel, M.; Li, P. +3 more
We have identified 28 solar flares simultaneously observed by a SIGNE detector aboard the Venera 13 and Venera 14 spacecraft and the Hard X-Ray Burst Spectrometer (HXRBS) aboard the Solar Maximum Mission (SMM), over a wide range of observing angles. Fourteen of them were also observed by the Gamma Ray Spectrometer (GRS) on SMM and were included in…
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 …