Search Publications
New light on UU Sagittae.
Pollacco, D. L.; Bell, S. A.
New V- and I-band CCD photometry and medium-resolution spectroscopy are used to derive the masses and radii accurate to less than 10 percent for the individual components of the eclipsing central star of the planetary nebula Abell 63 - UU Sge. Emission lines from the secondary component and He II and N V absorption features from the primary compon…
Analysis of the DA white dwarf HZ 43A and its companion star.
Werner, K.; Jordan, S.; Barstow, M. A. +3 more
The DA white dwarf HZ 43 A (WD 1314+293) is analyzed based on a newly obtained optical spectrogram. We demonstrate that the derived parameters Teff = 49.000 K and log g = 7.7 are in agreement with the observed Ly-alpha line, the slope of the UV continuum, and the measured trigonometric parallax. The EXOSAT spectrograms of Paerels et al.…
Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics
Neubauer, Fritz M.; Glassmeier, Karl-Heinz
Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfvén velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of …
Mirror modes and fast magnetoacoustic waves near the magnetic pileup boundary of comet P/Halley
Motschmann, Uwe; Neubauer, Fritz M.; Fuselier, S. A. +4 more
Large-amplitude ultralow-frequency wave structures observed on both sides of the magnetic pileup boundary of comet P/Halley during the flyby of the Giotto spacecraft have been analyzed using suprathermal electron density and magnetic field observations. Upstream of the boundary, electron density and magnetic field magnitude variations are anticorr…
Velocity space diffusion and nongyrotropy of pickup water group ions at comet Grigg-Skjellerup
Coates, A. J.; Neubauer, Fritz M.; Wilken, B. +1 more
The diffusion of water group cometary ions in velocity space at comet Grigg-Skjellerup was measured during the Giotto spacecraft encounter. The evolution of the collapsed pitch angle and energy distributions during the inbound and outbound passes shows that the timescale for energy diffusion may be similar to that for pitch angle diffusion. Fully …
UES and IUE observations of the O9.5V star HD 93521 : non-radial pulsatutions, wind and distance.
Howarth, Ian D.; Reid, Andy H. N.
We have obtained time-series spectroscopy of the rapidly rotating O9.5 V star HD 93521 during commissioning of the Utrecht Echelle Spectrograph (UES) on the William Herschel Telescope. The He I lines show 'wiggles' at the approximately 1% level, which move systematically from blue to red across the profile; by contrast, the He II lines do not show…
Internal structure and polarization of the optical jet of the quasar 3C273
Mackay, C. D.; Thomson, R. C.; Wright, A. E.
THE extragalactic radio source 3C273 was the first quasar to be identified1, and remains one of the nearest and most luminous quasars known. In radio images2-4, it appears as a bright, point-like nucleus from which emerges a single large jet; the jet is also apparent in optical images5-8, but the relatively poor re…
Discovery of a Magnetic/Nonmagnetic Double-degenerate Binary System
Bergeron, P.; Saffer, Rex A.; Liebert, James +1 more
We report the discovery of an unresolved binary system consisting of two degenerate stars: one a polarized object with an inferred magnetic field among the largest yet found on a white dwarf; the other a normal DA with no detectable field. We have deconvolved the composite 1250 Å-2.2 microns energy distribution into individual spectra and find tha…
Polarimetric investigatio, on interstellar dust within 50 PC from the sun.
Leroy, J. L.
We have analyzed the polarization catalogue, for 1000 stars closer than 50 Pc, which has been presented in a companion paper. Although the accuracy of the measurements is generally very good (better than 0.02% for more than 700 stars), the catalogue contains essentially unpolarized stars, which is to be related to the well known depletion of dust …
A Catalog of Stellar Lyman-Alpha Fluxes
Simon, Theodore; Landsman, Wayne
We present a catalog of stellar Ly-alpha emission fluxes, based on new and archival images obtained with the IUE spacecraft. The catalog includes 227 stars with detectable Ly-alpha emission fluxes, and upper limits on the Ly-alpha emission flux for another 48 stars. Multiple flux measurements are given for 52 stars. We present a model for correcti…