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Ultraviolet spectra of planetary nebulae. 6 NGC 7662.
Harrington, J. P.; Lutz, J. H.; Seaton, M. J. +1 more
The planetary nebula NGC 7662 considered in the present investigation has been a popular object for detailed modelling. Two models are considered. In Model I, which is similar to a model considered by Harrington et al. (1979), dust absorption is neglected. The model cannot provide results which are in agreement with two types of observational data…
Detailed observations of NGC 4151 with the IUE -II. Variability of the continuum from 1978 february to 1980 may, including X-ray and optical observations.
Tanzi, E. G.; Tarenghi, M.; Perola, G. C. +13 more
NGC 4151 has been extensively monitored with IUE from 1978 February to 1980 May. The rather erratic behaviour of the ultraviolet light curve seems to be mainly due to variations which occur at rates which, if extrapolated, would produce factor two changes in time-scales between five and 30 days, implying a radius of the order of 0.01 pc for the so…
P-Cyg profiles observed in the ultraviolet and visible spectra of Wolf-Rayet stars.
Willis, A. J.
A semi-qualitative analysis of the UV P-Cygni line profiles observed in the IUE spectra of seven WN and three WC Wolf-Rayet stars is presented. The velocity characteristics of these profiles are presented and combined with complementary measurements from visible spectra, allowing an inspection of P-Cygni profiles encompassing a wide range of ionic…
Very extended ionized gas in radio galaxies-I. A radio, optical and ultraviolet study of PKS 2158-380.
Boksenberg, A.; Penston, M. V.; Snijders, M. A. J. +7 more
IUE observations of PKS 2158-380 show gas in a high state of ionization extending out to a radius of 15 kpc, with a spectrum which is inconsistent with local photoionization by hot stars, and a UV point source at the nucleus which can be fitted by a power law with a spectral index of -1.4. If the gas is distributed within the galaxy in such a way …
The carbon and nitrogen abundances in WN and WC Wolf-rayet stars.
Willis, A. J.; Smith, L. J.
New ultraviolet spectroscopy obtained with the IUE satellite of helium, carbon and nitrogen lines in six WN and four WC stars have been analysed using non-LTE Escape Probability techniques to derive the stellar atmospheric C/N, C/He and N/He ratios. The derived C/N ratio is found to lie in the range: 0.02-0.06 for WNE stars; 0.006-0.04 for WNL sta…
A study of element depletions in interstellar gas.
Gondhalekar, P. M.; Pettini, M.; Phillips, A. P.
Optical and ultraviolet studies have shown that most elements in the gas phase of the interstellar medium are underabundant relative to the solar composition. The missing gas atoms are assumed to be contained in interstellar grains. The study of the depletion of interstellar elements in the gas phase provides, in this connection, a means for study…
The physical conditions within the poly-polar nebula NGC 6302 - III.
Walsh, J. R.; Meaburn, J.; Barral, J. F. +1 more
IUE observations of the ultraviolet emission lines and continuum from the wind-driven poly-polar nebula NGC 6302 have been combined with those obtained of the visible emission lines to investigate the physical parameters of the ionized gas. Several relationships consolidate the view that this nebula is predominantly ionized radiatively by a very h…
IUE spectra of clumpy irregular galaxies
Casini, C.; Benvenuti, P.; Heidmann, J.
IUE spectra at short wavelengths were obtained for two clumpy irregular galaxies, Mkn 8 and Mkn 325. Clumps could be resolved across the slit. Statistics now available on 10 clumps show that, on average, each clump radiates 100 times more at 155 nm than the giant H II region 30 Doradus and contains 0.00007 early-type stars. This confirms the hypot…
The ultraviolet spectra of the nuclei of spiral galaxies. I - NGC 4594, 3031, 5194 and 4258
Efstathiou, G.; Gondhalekar, P. M.; Ellis, R. S.
Absolute spectrophotometry is presented from 1250 A to 4 microns within the same aperture in the nuclei of four spiral galaxies. The light distributions within the apertures are often irregular but no positive evidence for internal reddening has been found, except possibly for NGC 3031. The absence of any reddening features could still be consiste…
The interstellar spectrum of the supernova 1980k in NGC 6946.
Panagia, N.; Savage, B. D.; Boksenberg, A. +10 more
Bright supernovae in external galaxies offer a rare opportunity to probe the intervening interstellar media over very extended path-lengths, including the disk and halo of the Galaxy and the parent galaxy of the supernova. SN 1980k was discovered in NGC 6946 on 1980 October 29. In the first month after discovery, high resolution optical and ultrav…