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The first UV spectrum of 2060 Chiron*
Brosch, N.
Chiron was observed for the first time in the UV, approximately one year before its perihelion passage, with the IUE satellite. Three long-wave, low-dispersion spectra were obtained, representing a total exposure of 56400s. The spectra contain useful information, though with very low S/N ratio, longward of ~2550A. No emission from gaseous species …
The three-ring structure of Supernova 1987A
Burderi, L.; King, A. R.
The current scenario for the complex <=3-arcsec structures surrounding SN 1987A is that they result from the emission of a thin shell of matter surrounding the supernova, illuminated by the initial extreme-ultraviolet flash from the explosion of the progenitor. Before the Hubble Space Telescope (HST) the two ring-shaped loops, ~3 arcsec in size…
Spectropolarimetry of the dwarf nova IP Peg
Dhillon, V. S.; Rutten, R. G. M.
We present spectropolarimetric observations of the eclipsing dwarf nova IP Peg in quiescence. The data show linear polarizations with a mean value of 0.10+/-0.06 per cent. There are no significant differences between the continuum and line polarizations and no significant variations with wavelength or binary phase. We argue that the measured polar…
A photoionization model of the nebula around the WC11 star M4-18
Rao, N. Kameswara; Surendiranath, R.
A photoionization code has been developed incorporating provision for the presence of dust mixed with gas. M4-18 has been modelled utilizing optical CCD spectra and other observations ranging from UV to radio wavelengths. T_e and N_e from the model are 6600K and 6050 cm^-3, respectively. The abundances of C, N and Ne are found to be the same as th…
Average unreddened UV flux distributions of OB dwarfs
Megier, Andrzej
The average intrinsic flux distributions for early-type main-sequence stars are obtained from IUE low-dispersion spectra. The colour-excess dereddening method allows stars of various colour excesses to be included in the samples. The resulting spectra are free from all interstellar extinction effects that correlate with E(B-V).
Elemental abundances for a sample of southern galactic planetary nebulae.
Barlow, M. J.; Kingsburgh, R. L.
We present spectrophotometric observations of a sample of 80 southern galactic planetary nebulae (PN), and derive elemental abundances for 68 objects, supplementing the optical observations with Uv data in 25 cases. We define Type I PN as those objects that have experienced envelope-burning conversion to nitrogen of dredged- up primary carbon. Suc…
Thick tori around active galactic nuclei: a comparison of model predictions with observations of the infrared continuum and silicate features.
Danese, L.; Granato, G. L.
The continuum expected from active galactic nuclei (AGN) surrounded by thick tori is compared to the data available for a sample of optically selected Seyfert 1 galaxies. The optical and near-IR nuclear fluxes have previously been derived for these objects, and hence the spectral energy distributions (SEDs) of their active nuclei can be analysed. …
Terminal velocities of Wolf-Rayet winds from infrared He I lines.
Williams, P. M.; Eenens, P. R. J.
We have observed 1- and 2- im spectra covering the He i 2s-2p triplet and singlet lines in a sample of Wolf-Rayet stars. Most of the He ilines have P Cygni profiles, which are fitted using the SEI (Sobolev with exact integration) method to derive terminal velocities. From our observations of 41 stars, the He i velocities are only about 70 per cent…
A preliminary analysis of the planetary nebula central star V477 Lyrae.
Pollacco, D. L.; Bell, S. A.
We present a preliminary analysis of V477 Lyr, the eclipsing central star of Abell 46. Medium-resolution spectroscopy has been obtained, providing radial-velocity measurements for both components for the first time. New V-band charge coupled devices (CCD) photometry has also been obtained and the first full light-curve analysis is presented. The s…
A ROSAT survey of hot DA white dwarfs in non-interacting binary systems.
Barstow, M. A.; Koester, D.; Holberg, J. B. +3 more
A number of new non-interacting binary systems comprising a white dwarf plus a normal stellar companion have been discovered by the ROSA T X-ray and EUV sky surveys. We discuss the identification of nine of these objects, determine the temperatures and gravities of the white dwarfs, and compare their atmospheric compositions with the population of…