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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…
Interstellar extinction in the Small Magellanic Cloud.
Nandy, K.; Willis, A. J.; Wilson, R. +5 more
IUE observations of three considerably reddened stars located near the core of the Small Magellanic Cloud and of two comparison stars which are also SMC members are presented. This region contains a considerable amount of dust. The UV spectrum of one of the reddened stars (BBB 338) shows the 2200-A wavelength feature characteristic of the Galactic…
IUE observations of the Lac object AO 0235+164.
Boksenberg, A.; Penston, M. V.; Snijders, M. A. J. +1 more
AO 0235+164 was observed with IUE during its February 1979 outburst. The object was detected in both the short and long wavelength cameras. Hydrogen Lyman-alpha absorption in the z = 0.524 system is detected with equivalent width of 62 + or - 28 A (1-sigma error). From this and previous 21-cm data, the spin temperature of the absorbing material is…
Interstellar extinction in the Perseus arm.
Nandy, K.; McLachlan, A.; Morgan, B. L.
Individual UV extinction curves for nine stars located in the direction of h and Chi Persei in the distance range 0.6-4.4 kpc are presented. The observations were made with the International Ultraviolet Explorer (IUE) in the low dispersion mode with large aperture. The sample has been enlarged by the use of available UV and visible data for 32 red…
Ultraviolet spectra of planetary nebulae. VII. The abundance of carbon in the very low excitation nebula HE 2-131.
Seaton, M. J.; Adams, S.
Features observed in infrared spectra suggest that certain very low excitation (VLE) nebulae have low C/O abundance ratios (Cohen & Barlow 1980; Aitken & Roche 1982). Fluxes in the multiplets [O II] sun2470 and [O II] λ2326 have been measured for the VLE nebula He 2-131 = HD 138403 using lUE high-dispersion spectra. An analysis …