Search Publications
The origin of extended interstellar shells around Wolf-Rayet stars having bright optical ring nebulae.
Fesen, R. A.; Nichols, J. S.
Investigations of the interstellar environment around Wolf-Rayet (WR) stars have led to the discovery of extended shells of gas and dust 50-100pc in diameter in the lines of sight toward three WR stars. In this paper, several origins for these extended shells are discussed. While positional coincidences cannot be excluded, the locations of the WR …
Origin of the O^+^ pick-up ions in the heliosphere.
Geiss, J.; Mall, U.; Gloeckler, G.
The main sources for the ions in the interplanetary medium are the solar wind and the interstellar gas intruding into the heliosphere. Other sources, i.e. comets and planets can, however, contribute significantly locally. We present approximate expressions for deriving fluxes of pick-up ions originating from local neutral gas sources. Since the Io…
Determining hot star wind terminal velocities from low-resolution IUE data.
Prinja, R. K.
Empirical relations are provided which enable consistent determinations of wind terminal velocities for hot stars where only low-resolution IUE spectra are available. The calibrations are based on terminal velocities derived from the violet limit of `black' absorption troughs seen in high-resolution IUE spectra of saturated wind lines of hot stars…
Multiwavelength observations of RV Tauri stars III. R Scuti
Evans, A.; Lloyd Evans, T.; Rawlings, J. M. C. +7 more
We present ultraviolet, optical and infrared observations of the RV Tauri star R Sct. We argue that changes in the ultraviolet spectrum with pulsational phase cannot be due to changes in effective temperature and gravity alone, and that variable circumstellar extinction in the form of Rayleigh scattering is also necessary. The intrinsic ultraviole…
Hydrodynamic model of Kepler's supernova remnant constrained by EINSTEIN and EXOSAT X-ray spectra.
Ballet, J.; Rothenflug, R.; Magne, B. +1 more
We have used the EXOSAT spectrum of Kepler's supernova remnant (including the Fe K line and the high-energy continuum) to further constrain its models. On the basis of the large abundances of Si, S and Fe required by a Sedov model, we have focused on models of young supernova remnants in which the reverse shock (propagating into the stellar ejecta…
A study of a high resolution IUE spectrum of AM Canum Venaticorum.
Sion, E. M.; Solheim, J. -E.
We have obtained the first high resolution IUE spectrum of the helium-rich, cataclysmic variable star AM CVn. The spectrum is greatly underexposed, but we can still detect both wide and narrow line profiles. We report broad, shortward-shifted, P-Cygni-like absorption and in some cases emission lines in the far UV high ionization resonance lines of…
The massive star content of the blue dwarf galaxy IZw 36 from Faint Object Camera observations
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
We have observed the blue dwarf galaxy IZw 36 with the f/96 relay of the Faint Object Camera and have for the first time resolved massive stars, using the broad band filters F175W, F342W, F430W and F480LP. We have measured the fluxes of 143 of these objects and studied their characteristics in color-magnitude diagrams. A few stars may be red super…
Ultraviolet flare activity on the eclipsing binary SZ Piscium.
Doyle, J. G.; Mathioudakis, M.; Mitrou, C. K. +1 more
The estimated total chromospheric, transition region and coronal losses for a flare observed on the eclipsing binary SZ Psc with the International Ultraviolet Explorer (IUE) satellite on 6 July 1990 is of the order of 4.5 1036 ergs. This estimate is similar to that derived by Doyle et al. (1989) for an ultraviolet flare on another RS CV…
The interior structure and evolution of blue straggler stars in open clusters.
Napiwotzki, R.; Schoenberner, D.
We present a detailed spectroscopic determination of effective temperatures and surface gravities of B- and A-type blue straggler stars in four open clusters by means of model atmospheres and new optical/UV spectrograms. By using a new method of analysis which also allows to separate objects not belonging to the cluster under investigation we show…
Optical observations of the hot post-asymptotic giant branch star, HD 177566.
Dufton, P. L.; Keenan, F. P.; Kendall, T. R. +2 more
An LTE model atmosphere analysis of optical and ultra-violet spectra is presented for a hot high galactic latitude star, HD 177566, previously identified as a post-asymptotic giant branch candidate from its ultra-violet spectrum. The derived atmospheric parameters and chemical composition confirm that HD 177566 is a low mass (M=~0.55Msun