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The Diffuse Interstellar Cloud toward HD 179406 (20 Aquilae)
Snow, Theodore P.; Black, John H.; Hanson, Margaret M.
An analysis of the diffuse interstellar cloud complex in front of HD 179406 (20 Aql) is presented. Along this sight line, multispectral absortion- and emission-line studies have uncovered at least three distinct velocity components due to individual clouds. A dominant velocity component is seen in both the absorption and emission-line data sets at…
Ulysses Radio Occultation Observations of the Io Plasma Torus During the Jupiter Encounter
Bird, M. K.; Asmar, S. W.; Volland, H. +4 more
Radio signals from Ulysses were used to probe the lo plasma torus (IPT) shortly after the spacecraft's closest approach to Jupiter. The frequencies of the two downlinks at S-band (2.3 gigahertz) and X-band (8.4 gigahertz) were recorded, differenced, and integrated in order to derive the columnar electron density of the IPT. The measurements agree …
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 Ultraviolet-bright Stars of Omega Centauri, M3, and M13
O'Connell, Robert W.; Hill, Robert S.; Bohlin, Ralph C. +7 more
Two new UV-bright stars detected within 2 arcmin of the center of Omega Cen are spectroscopically investigated with the short-wavelength spectrograph of the IUE. The IUE spectra of the UV-bright stars UIT-1 and UIT-2 in the core of Omega Cen superficially resemble those of Population I mid-B stars. The absorption lines of the core UV-bright stars …
Inner Shell of Optically Thin Gas in Active Galactic Nuclei
Zheng, Wei
The Lyα and Balmer line profiles in more than 50 Seyfert 1 galaxies and QSOs are studied. Approximately 60% of the objects show similar profiles, 25% show smaller FWHM of Hβ or Hα. In five objects the Lyα profiles have stronger wings than the Balmer lines. The Lyα/Balmer ratio increases along both wings, suggesting an inner envelope of a very broa…
Coordinated Ginga, IUE, and VLA Observations of Stellar Activity in sigma 2 Coronae Borealis
Walter, F.; Vilhu, O.; Stern, R. A. +5 more
Observations of the active cool star binary system Sigma(2) Corona Borealis with the Large Area Counters on the Ginga X-ray satellite over 2.5 d, or about two orbital periods, are reported. Throughout the observations, Sigma(2) CrB exhibited X-ray variability on time scales ranging from tens of minutes to hours. The X-ray light curve shows evidenc…
H 0414+009 - an X-ray bright BL Lac with a radio tail in a distant cluster of galaxies.
Abraham, R. G.; George, I. M.; McHardy, I. M. +2 more
VLA observations of the X-ray selected BL Lac H0414+009 at 6, 20 and 90 cm show that it has a steep-spectrum (α~1; f_v_ is proportional to v^-α^) radio tail. The tail extends ~40 arcsec from the core, in a gentle curve. There is no evidence of extended emission on the opposite side of the core. This is by far the clearest example of a single-sided…
The Ongoing Outburst of the Eclipsing Symbiotic Nova AS 296: The First 1200 days
Munari, Ulisse; Whitelock, Patricia A.; Gilmore, Alan C. +3 more
Ultraviolet, optical, and infrared photometry is reported for the symbiotic star AS 296, spanning the first 1200 d of its outburst which began in June 1988. The effects of the outburst were restricted to the wavelength interval 2200-7500 A. The progress of the event was followed through two maxima and two eclipses of the hot source by the M5 III c…
Multiwavelength observations of RV Tauri stars. I. AC Herculis.
Evans, A.; Shenton, M.; Albinson, J. S. +6 more
We present ultraviolet, optical and infrared (including IRAS) observations of the RV Tauri star AC Her. IRAS LRS spectra suggest that the dust shell of AC Her may consist of both silicon carbide and silicates, and modeling of the optical-IR flux distribution suggests the presence of at least two distinct dust shells, the larger of which may be the…
Hubble Space Telescope Spectroscopy of OB Stars in M31
Bianchi, L.; Hutchings, J. B.; Lamers, H. J. G. L. M. +2 more
We have obtained UV spectra of two luminous hot stars in M31 with the Hubble Space Telescope. The stars are of late O and WN spectral type and lie on opposite sides of M31. We derive UV extinction curves for M31 which differ from both the Galaxy and the LMC. We find differences between the 15 absorbers in both lines of sight in M31 and in the Gala…