Search Publications
Observations of Highly Ionized Gas in the Galactic Halo
Sembach, Kenneth R.; Savage, Blair D.
A sample of high-quality sight lines is studied by means of IUE spectra to study the formation of Si IV, C IV, and N V in the Galaxy and constrain the mechanisms of halo gas formation. High-dispersion IUE spectra are taken for 12 objects to give combined spectra for studying the halo gas along the sight lines. N V absorption is reported in 10 of t…
X-Ray--heated Models of Stellar Flare Atmospheres: Theory and Comparison with Observations
Hawley, Suzanne L.; Fisher, George H.
A sequence of five model atmospheres consisting of the photosphere, chromosphere, and transition region is computed. The models represent the response of the gas in a magnetically confined loop to intense flare energy release. It is concluded that the structure of the flare transition region is consistent with the conductive heating balancing opti…
Spectral Synthesis in the Ultraviolet. IV. A Library of Mean Stellar Groups
O'Connell, Robert W.; Burstein, David; Wu, Chi-Chao +1 more
A library of mean UV stellar energy distributions is derived from IUE spectrophotometry of 218 stars. The spectra cover 1230-3200 A with a spectral resolution of about 6 A. They have been corrected for interstellar extinction and converted to a common flux and wavelength scale. Individual stars were combined into standard groups according to their…
Ultraviolet and Radio Observations of Milky Way Halo Gas
Savage, Blair D.; Lockman, Felix J.; Danly, Laura +1 more
Interstellar-absorption-line and 21-cm emission-line data for sight lines to 56 stars are combined in order to study the kinematics and spatial distribution of the gas that is at great distances from the Galactic plane. Measurements of the interstellar velocities and H I column densities from the 21-cm emission and Ly-alpha absorption are included…
X-Ray Luminosity and Spectral Variability of Hard X-Ray--selected Active Galactic Nuclei
Tagliaferri, G.; Giommi, P.; Grandi, P. +2 more
One hundred sixty-one observations archived in the EXOSAT data base are analyzed in order to study time and spectral variability of all 30 sion-line active galactic nuclei (AGNs) in the Piccinotti sample. For each source long-term (from days to months) and short-term (from minutes to hours) luminosity variations were sought using the soft (LE: 0.0…
The Broad Emission-Line Profiles and Profile Variability of the Seyfert 1 Galaxy Arakelian 120
Korista, Kirk T.
We present Hα and Hβ broad emission-line profiles of the Seyfert galaxy Arakelian 120 from the past ~10 yr, representing over 100 spectroscopic observations. The broad emission-line profiles of the Balmer lines are complex in structure and variable; the profile variations themselves are complex. We attempt to isolate separate emitting components w…
The Colorado IUE Active Galaxy Survey. I. Blazars
Shull, J. M.; Kinney, Anne; Edelson, Rick +2 more
This paper presents consistently reduced ultraviolet continuum flux densities and spectral indices derived from all 499 usable archived IUE observations of blazars made through mid-1991. The extraction of one-dimensional spectra and the measurement of spectral parameters are discussed. A detailed error analysis is presented, including a discussion…
The Orbital Parameters and the IUE Spectrum of the Single-lined Spectroscopic Binary HD 698
Sahade, Jorge; Barba, Rodolfo; Kondo, Yoji
IUE observations of the spectroscopic binary HD 698 show that its continuous spectrum corresponds to that of a B5 III-II object and that, even in the ultraviolet, the object is single-lined. The spectrum displays several sets of lines, all in absorption, where features can be distinguished that partake of the orbital motion of the B5 component, li…