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Mid-Ultraviolet Determination of Elliptical Galaxy Abundances and Ages
Ferguson, Henry C.; Lotz, Jennifer M.; Bohlin, Ralph C.
We investigate the effects of abundance and age on the mid-UV spectra and Mg2 strengths of stellar populations using simple population synthesis models. These models are used to constrain the star formation history of four nearby elliptical galaxies and spiral bulges. The mid-UV (1800-3200 Å) light of evolved stellar populations (>1 …
Compositional Variation on the Surface of Centaur 8405 Asbolus
Brown, R. H.; Buie, M. W.; Campins, H. +3 more
Near-infrared 1-2 µm spectra of the Centaur 8405 Asbolus (1995 GO) have been obtained using the Hubble Space Telescope near-infrared camera and multiobject spectrometer. Strong and variable absorption features indicate a significantly inhomogeneous surface characterized by water ice mixed with additional unknown constituents. Over a 1.7 hr i…
Probing the Interstellar Medium in Early-Type Galaxies withInfrared Space Observatory Observations
Helou, G.; Lu, N.; Malhotra, S. +9 more
Four IRAS-detected early-type galaxies were observed with the Infrared Space Observatory (ISO). With the exception of the 15 µm image of NGC 1052, the mid-IR images of NGC 1052, NGC 1155, NGC 5866, and NGC 6958 at 4.5, 7, and 15 µm show extended emission. Mid-IR emission from NGC 1052, NGC 1155, and NGC 6958 follows a de Vaucouleurs pr…
On the Ionizing Continuum in Active Galactic Nuclei: Clues from the Infrared Space Observatory
Prieto, M. Almudena; Viegas, Sueli M.
The Infrared Space Observatory (ISO) coronal line spectrum of the brightest Seyfert galaxies from the CfA sample is presented and modeled. ISO observations of [O IV] 25.9 µm, [Ne V] 14.3 µm, [Mg VIII] 3.02 µm, and [Si IX] 2.58 µm lines are presented; their relationship with the soft part of the ionizing spectrum from 50 to …
Water and Dust Emission from W Hydrae
Elitzur, Moshe; Zubko, Victor
We construct a self-consistent model for the wind around W Hydrae by solving the coupled equations describing the hydrodynamics and dust radiative transfer problems. The model matches simultaneously the observed continuum radiation and wind velocity profile. The water line emission is calculated next using the water abundance as the only free para…
Extreme-Ultraviolet Spectral Line Widths in Quiet-Sun Coronal Plasmas at Distances of 1.03<=Rsolar<=1.45 along the Solar Equatorial Plane
Doschek, G. A.; Feldman, U.
We measure the full width at half-maximum intensity (FWHM) of extreme-ultarviolet (EUV) spectral line profiles as a function of height in the Sun's equatorial west limb streamer region using EUV spectra recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) spacecra…
Dynamic-range limitations of intensified CCD photon-counting detectors
Fordham, J. L. A.; Moorhead, C. F.; Galbraith, R. F.
The bright limit to the dynamic range of intensified CCD photon-counting detectors is governed by coincidence losses. In this paper a theoretical analysis of the loss mechanisms is carried out and verified using laboratory data. For applications where the input source is stable, such as star field imaging from space, the theoretical dynamic-range …
Active eclipsing binary RT Andromedae revisited
Chochol, D.; Vittone, A. A.; Errico, L. +4 more
All available photometric and spectroscopic data of the short-period RS CVn-like binary RT And have been reanalyzed in a homogeneous way. The long-term orbital period change is explained by two period jumps, a continuous period decrease combined with the light-time orbit or two light-time orbits. UBVRIJK light curves without maculation effects tog…
Properties and nature of Be stars. XIX. Spectral and light variability of 60 Cygni
Harmanec, P.; Huang, L.; Cao, H. +11 more
An analysis of electronic spectra secured between 1992 and 1999 at the Haute Provence, Ondřejov and Dominion Astrophysical Observatories and of differential UBV measurements of 60 Cyg obtained between 1984 and 1999 at Hvar, San Pedro Mártir, Toronto and Xinglong Observatories, the all-sky Hipparcos satellite H_p photometry transformed to Johnson V…
HE 2-113: A Multipolar Planetary Nebula with Rings around a Cool Wolf-Rayet Star
Sahai, Raghvendra; Nyman, Lars-Åke; Wootten, Alwyn
We present Hα imaging and molecular-line (CO) observations of He 2-113, an object which belongs to a rare class of planetary nebulae with Wolf-Rayet type central stars. The Hα images, obtained with the Hubble Space Telescope Wide-Field Planetary Camera 2, show that He 2-113 has an overall bipolar shape and two bright, knotty, compact ringlike stru…