Search Publications
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…
The spectrum of the planetary nebula NGC 6572.
Feibelman, W. A.; Hyung, S.; Aller, L. H.
A detailed, high-spectral-resolution study of the spectrum of the planetary nebula NGC 6572 is made for the optical region 365 to 1005 nm, using the Hamilton echelle spectrograph of Lick Observatory, and for the ultraviolet (UV) spectral region 125 to 320 rIm with the high-dispersion mode of the International Ultraviolet Explorer (lUE) satellite. …
No fundamental-mode pulsation in R Leonis ?
Tuthill, P. G.; Feast, M. W.; Haniff, C. A. +1 more
We present new and precise angular diameter measurements of the long-period variable R Leonis at 833 and 903 nm. Our inferred photospheric diameter (38±2.5 mas) and stellar effective temperature (2459 + 150 K) are both in good agreement with recent determinations made at the same variability phase in the near-infrared. Assuming a parallax of 8.3 m…
Hubble Space Telescope observations of the BL Lac object PKS 1413+135 : the host galaxy revealed.
Abraham, R. G.; McHardy, I. M.; Crawford, C. S. +1 more
In an earlier paper, we showed that the BL Lac object PKS 1413 + 135 appears to lie in a disc-dominated galaxy with colours closer to those of an elliptical than a spiral galaxy. Subsequently, a large neutral hydrogen absorption feature was found at the optical redshift of the proposed host galaxy together with a substantial absorbing column in th…
RE 1738+665: the hottest DA white dwarf detected by ROSAT.
Barstow, M. A.; Koester, D.; Sansom, A. E. +6 more
One of the most important results of the ROSAT all-sky X-ray and EUV surveys has been the discovery of a large number of previously uncatalogued white dwarfs. One of these, RE 1738+665, is found to be the hottest hydrogen-rich DA white dwarf detected, with a temperature of 88000 K and log g =7.8, lying significantly above the 70000-K observational…
The nature of the newly discovered DO white dwarf RE 0503-289.
Werner, K.; Barstow, M. A.; Holberg, J. B. +2 more
We report the discovery of a hot DO white dwarf, RE 0503 - 289, which lies in a region of very low interstellar H I density. It lies within 1 deg of the hot DA white dwarf RE 0457 - 281 which we have reported as having the lowest directly measured H I column. A follow-up observation made using the Voyager 2 UV spectrometer reveals a strong continu…