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The outer atmosphere of the carbon star TX Piscium.
Eriksson, K.; Gustafsson, B.; Olofsson, H. +5 more
A high-resolution LWP IUE spectrum of the bright N-type carbon star TX Psc demonstrates that the Mg II h and k emission profiles are strongly affected by absorption from Mg II, Mn I, probably Fe I, and possibly from molecules. The indication that the absorbing matter has a column density of not less than 10 to the 20th H atoms or molecules per sq …
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…
EXOSAT detection of an X-ray flare from the solar type star pi 1 UMa.
Piro, L.; Landini, M.; Pallavicini, R. +1 more
An X-ray flare has been detected on the G0 dwarf star π1UMa using the European satellite EXOSAT. With the exception of the Sun, this is the first time that an X-ray flare has been observed in a normal solar-type star, which is not a member of a binary system and is not a classical flare star. As a member of the Ursa Major Cluster, π
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…
EXOSAT observations of the Seyfert galaxy NGC 7469; rapid hard X-rayvariability and a soft X-ray excess.
Barr, P.
The results of a series of EXOSAT observations of the Seyfert 1 (and starburst) galaxy NGC 7469 performed in July 1984 are presented. During one observation, hard X-ray variability by a factor 2 within 5 hr was found, while the soft X-ray intensity remained constant. In addition the spectral data indicate an excess of soft X-ray emission over that…
Metal abundances in helium-rich white dwarf atmospheres.
Koester, D.; Weidemann, V.; Zeidler-K. T., E. -M.
IUE observations of L745-46A, L119-34 and Ross 640 reveal the presence of Si, Fe, C, and very strong Mg II lines. These spectra, together with optical observations of white dwarfs with Ca II lines (type DZ) are analyzed within a network of model atmospheres with varying H/He, C/He and metals/He ratios. The influence of non-negligible H content (el…
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…