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Infrared Space Observatory Measurements of [C II] Line Variations in Galaxies
Helou, G.; Stacey, G.; Malhotra, S. +11 more
We report measurements of the [C II] fine-structure line at 157.714 µm in 30 normal star-forming galaxies with the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). The ratio of the line to total far-infrared (FIR) luminosity, L[CII]/LFIR, measures the ratio of the cooling of gas to that of dus…
On the Evolutionary Phase and Mass Loss of the Wolf-Rayet--like Stars in R136a
Hubeny, Ivan; Heap, Sara R.; de Koter, Alex
We report on a systematic study of the most massive stars, in which we analyzed the spectra of four very luminous stars in the Large Magellanic Cloud. The stars lie in the 30 Doradus complex, three of which are located in the core of the compact cluster, R136a (R136a1, R136a3, and R136a5), and the fourth (Melnick 42), located about 8" north of R13…
Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images
Wells, Eddie N.; Storrs, Alex D.; Thomas, Peter C. +3 more
We utilize the 56 images of Asteroid 4 Vesta obtained through four mineralogically diagnostic filters by the Hubble Space Telescope (Zellneret al.1997,Icarus) to construct a geologic map. Vesta's surface is found to be geologically diverse and to be dichotomous at a hemispheric scale. The eastern hemisphere (longitude definition from Thomaset al.1…
SN IA light curves and radioactive decay
Turatto, M.; Cappellaro, E.; Benetti, S. +4 more
The absolute V light curves of 5 SNe Ia, selected to represent the known range of absolute luminosities at maximum for this class of objects, are presented. Comparison of the long term luminosity evolution shows that the differences seen at maximum persist, and actually increase with time, reinforcing the notion that intrinsic differences do exist…
EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection
Llebaria, A.; St. Cyr, O. C.; Michels, D. J. +31 more
We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the p…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. IX. Ultraviolet Observations of Fairall 9
Shull, J. M.; Malkan, M. A.; Martin, P. G. +53 more
An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with the International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). While the results of this campaign are more ambiguous than those of…
Polar Plume Anatomy: Results of a Coordinated Observation
Plunkett, S. P.; Thompson, B. J.; Gurman, J. B. +5 more
On 7 and 8 March 1996, the SOHO spacecraft and several other space- and ground-based observatories cooperated in the most comprehensive observation to date of solar polar plumes. Based on simultaneous data from five instruments, we describe the morphology of the plumes observed over the south pole of the Sun during the SOHO observing campaign. Ind…
Time-Distance Helioseismology with the MDI Instrument: Initial Results
Kosovichev, A. G.; Hoeksema, J. T.; Scherrer, P. H. +10 more
In time-distance helioseismology, the travel time of acoustic waves is measured between various points on the solar surface. To some approximation, the waves can be considered to follow ray paths that depend only on a mean solar model, with the curvature of the ray paths being caused by the increasing sound speed with depth below the surface. The …
Microvariability survey with the Hubble Space Telescope Fine Guidance Sensors. Exploring the instrumental properties
Kuschnig, R.; Weiss, W. W.; Gruber, R. +2 more
The suitability of the Hubble Space Telescope (HST) Fine Guidance Sensors (FGS) for a magnitude limited survey of microvariability among guide stars is investigated. The linearity, relative sensitivity, and dead-time constants of the three FGSs are determined, and the photon noise limitation of the FGS photometry is confirmed. The noise spectrum i…
Infrared spectroscopy of interstellar apolar ice analogs
van Dishoeck, E. F.; Tielens, A. G. G. M.; Boogert, A. C. A. +2 more
Apolar ices have been observed in several regions in dense clouds and are likely dominated by molecules such as CO, CO_2 and the infrared inactive molecules O_2 and N_2. Interstellar solid CO has been well characterized by ground-based high resolution measurements. Recent ISO results showed the ubiquitous presence of abundant CO_2 ice and the pres…