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M 4-18 : a young cool planetary nebula.
Goodrich, R. W.; Dahari, O.
The unresolved planetary nebula M4-18 has been studied spectroscopically from the ultraviolet to the near-infrared. The nebula is found to be of very low excitation, with electron density Ne = 11,000 + or - 1,000/cu cm and electron temperature Te = 5600 + or - 1300 K, and a high O abundance. The central star is found to be among the coolest centra…
Simultaneous observations of CA II K and MG II K in T TAuri stars.
Basri, G.; Calvet, N.; Giampapa, M. S. +1 more
The first simultaneous, calibrated observations of the Ca II K and Mg II k resonance lines in T Tauri stars are presented. It is found that for T Tauri stars with mass greater than 1.5 solar mass, which have radiative cores and tend to be fast rotators, the k line seems to arise in an extended region (probably also responsible for the H-alpha emis…
The Jovian stratosphere in the ultraviolet
Encrenaz, T.; Owen, T.; Caldwell, J. +3 more
The center-of-disk reflectivity of Jupiter in the wavelength range from 1450 to 3150A˚has been computed from 30 low-dispersion IUE spectra taken during solar maximum in 1978-1980. A vertically inhomogeneous radiative transfer program is used to compute model reflectivities of various stratospheric compositions for comparison. Ammonia and acetylene…
Star formation and chemical abundances in the blue compact galaxy ESO338-IG04.
Bergvall, N.
The blue compact galaxy ESO 338 - IG04, which is undergoing a burst of star formation, is luminous for its type and has extremely blue colors. Attention is given to new broadband UBVIR photometry, spectroscopy, and both direct photographic and CCD observations of this galaxy, together with the reanalysis of a low resolution IUE spectrum. In H-alph…
An analysis of the bright white dwarf CD -38 10980.
Bruhweiler, F. C.; Wesemael, F.; Holberg, J. B. +1 more
The bright DA white dwarf CD - 38 deg 10980 is comprehensively analyzed using all available data. Detailed comparisons of the overall energy distribution and Lyman-alpha and Balmer profiles are made with theoretical predictions based on a homogeneous grid of model atmospheres. These comparisons yield a consistent, well-defined effective temperatur…
Spectrum of the high-excitation planetary nebula NGC 6741 (33-2 1).
Czyzak, S. J.; Keyes, C. D.; Aller, L. H.
Image tube observations carried out at the Lick and Mount Wilson Observatories were combined with IUE and infrared observations to study the spectra of the high-excitation planetary nebula NGC 6741. Plasma diagnostics were carried out and ion concentrations were calculated for ions from He I to Ca4(+). The ion densities and plasma diagnostics data…
The ultraviolet variability of Seyfert 1 galaxies.
Huchra, J. P.; Geller, M. J.; Chapman, G. N. F.
Multiple IUE spectra of nine Seyfert 1 galaxies, obtained over four years, were examined. Spectra of Mrk 509, ESO 141-G55, Fairall 9, III Zwicky 2, Mrk 279, NGC 3783, NGC 4593, NGC 7213, and NGC 7469 were examined for evidence of variability in both continuum and emission-line fluxes. All except NGC 7213 and III Zw 2 show 20 percent-80 percent con…
AY Ceti : a flaring, spotted star with a hot companion.
Simon, T.; Gibson, D. M.; Fekel, F. C., Jr.
AY Ceti is a late-type single-line spectroscopic binary, a bright X-ray source (L/x/ equal to about 1.5 x 10 to the 31st ergs/s), and a spotted star, as evidenced by its prominent photometric wave. In this paper, observations made with the IUE satellite and the VLA radio interferometer are reported. The 1200-2000 A UV spectrum of AY Cet shows a ho…
The development of the new Be phase of 59 CYG in the visual and in the far UV in 1978-1983.
Bolton, C. T.; Grady, C. A.; Stalio, R. +10 more
A tentative synthesis of visual and IUE observations of 59 Cyg during 1978-1983 when the new Be phase began to develop is presented. The study reveals correlation between those spectral features originating in the cool H-alpha-emitting envelope and features originating in superionized regions exhibiting C IV and N V lines. The long-term variabilit…
Transient quasi-periodic oscillations in in the X-ray flux of Cygnus X-3
van der Klis, M.; Jansen, F. A.
Cygnus X-3, a bright X-ray source at a distance1 of more than ~12 kpc beyond the edge of the galactic plane, has peculiar properties including very strong radio outbursts2, possibly showing jet-like features3, and emission in various γ-ray bands4-6 (but see ref. 7). The discovery of its 4.8-h X-ray perio…