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The Ionization Structure of Planetary Nebulae. VI. NGC 7662
Barker, T.
Spectrophotometric observations of emission-line intensities over the spectral range 1400 - 7200 Å have been made in five positions in the planetary nebula NGC 7662. The variation of the Balmer decrement with position in the nebula suggests that there may be internal dust. The O++ and Balmer continuum electron temperatures decrease with…
The Abundance of Gallium in B-Type Chemically Peculiar Stars
Sadakane, K.; Jugaku, J.; Takada-Hidai, M.
Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, eight He-weak stars, and seven normal stars are made with the resonance lines of Ga II at 1414 A and Ga III at 1495 A in International Ultraviolet Explorer (IUE) spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper …
Ultraviolet and Infrared Observations of Stars with ``Quenched'' Chromospheres and the Nature of Mass Loss
Carpenter, K. G.; Stencel, R. E.; Hagen, W.
Previous observational evidence implies that the presence of Ca II emission, a chromospheric indicator, is correlated with the gas/dust ratio in the envelopes of red giant and supergiant stars. An attempt is made to determine whether this correlation can be generalized to all chromospheric activity indicators and the gas/dust ratio. New ultraviole…
H1504+65: an Extraordinarily Hot Compact Star Devoid of Hydrogen and Helium
White, N. E.; Giommi, Paolo; Holberg, J. B. +4 more
The optical identification of the bright soft X-ray source H 1504 + 65, originally discovered by the HEAO I A-2 low energy detectors, is reported. The optical counterpart exhibits a steep, virtually featureless continuum from optical wavelengths through the ultraviolet. The spectrum is remarkably featureless except for a broad O VI adsorption feat…
C +2 Electron Temperatures in Planetary Nebulae
Kaler, J. B.
Electron temperatures are calculated for 30 planetary nebulae from the flux ratios of the C III] λ1909 and C II λ4267 lines, both of which are produced in the C+2 zone of the nebula. These temperatures correlate much better with optical [O III] temperatures than they do with those derived from [N II], except for low central star tempera…
The Ultraviolet Calibration of the Hubble Space Telescope. I. Secondary Standards of Absolute Ultraviolet Flux and the Recalibration of IUE
Bohlin, R. C.
Spectral energy distributions of IUE standards are presented. The five UV standards, HD 60753, BD +75°325, HD 93521, BD +33°2642, and BD +28°4211, were well observed in the original calibration epoch of the IUE observatory and have been monitored for UV variability since the IUE launch in 1978. Only observations from the first year of IUE were use…
X-Ray Variability of the BL Lacertae Object PKS 2155-304 in the 0.1--6 keV Range
Maccagni, D.; Maraschi, L.; Tanzi, E. G. +5 more
Observations of the bright BL Lac object PKS 2155 - 304 obtained at 1-6 keV using the ME argon counters and channel-multiplier array at the focus of the Exosat LE telescope, in conjunction with the 0.05-2-keV-bandpass 3000-A Lexan filter, during a total of 30 h in October-November 1983 and November 1984 are reported. The data are presented in tabl…
The Behavior of the C IV Emission Line in Active Galactic Nuclei
Colina, L.; Wamsteker, W.
The behavior of the C IV 1550 A emission line strength in variable active galactic nuclei (AGNs) such as Seyfert 1 galaxies and one broad-line radio galaxy (BLRG) is discussed on the basis of low-resolution spectra from IUE. The results are compared with those obtained previously for QSO samples. The variation of individual AGNs indicate that they…
The Stellar Population of NGC 6166
Gregg, M. D.; Bertola, F.; Oemler, A., Jr. +1 more
New optical and ultraviolet observations were obtained of NGC 6166, a cD galaxy and strong radio source in which both a large cooling flow and ongoing star formation have been detected. The spectrophotometry has been analyzed by a technique of differential spectral synthesis, in which the galaxy spectrum is compared with a spectral sequence compos…
X-Ray Spectral Observations of the Crab-like Supernova Remnants G21.5-0.9 and 3C 58
Becker, R. H.; Smith, A.; Davelaar, J.
Broad-band (2 - 10 keV) spectral data of the Crab-like supernova remnants 3C 58 and G21.5-0.9 have been obtained from the medium-energy instrument on EXOSAT. Both objects show a simple power-law spectrum with a spectral index of 0.72±0.12 for G21.5-0.9 and 1.30±0.26 for 3C 58. VLA 21 cm absorption measurements for G21.5-0.9 indicate a distance of …