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The Masses and Radii of the Eclipsing Binary zeta Aurigae
Harper, Graham M.; Bennett, Philip D.; Brown, Alexander +1 more
We present a full determination of the fundamental stellar and orbital parameters of the eclipsing binary ζ Aurigae (K4 Ib + BS V) using recent observations with the Hubble Space Telescope Goddard High Resolution Spectrograph (GHRS) and the Mark III long-baseline optical interferometer. The information obtained from spectroscopic and interferometr…
ULYSSES observations of pressure-balance structures in the polar solar wind.
Forsyth, R.; Balogh, A.; McComas, D. J. +4 more
Throughout its high-latitude excursion Ulysses has observed several types of solar wind structures. In addition to structures such as Alfven waves, compressional features, and microstreams, the solar wind also contains low contrast pressure-balance structures (PBSs). The PBSs are marked by an anti-correlation of the plasma and field pressures; the…
Heating of the thermal electrons in the coma of comet P/Halley
Geiss, Johannes; Altwegg, Kathrin; Balsiger, Hans +1 more
In the inner coma of a comet the total ion (or electron) density results from an equilibrium between ion production and ion destruction. The ions are mainly produced by photoionization of cometary gas, whereas the main destruction process is dissociative recombination of molecular ions with electrons. The reaction rate for the recombination depend…
GX340+0 with EXOSAT: its correlated X-ray spectral and timing behaviour.
van der Klis, M.; Kuulkers, E.
We report on three observations of the Z source GX340+0 performed with EXOSAT during 1985 and 1986. In two observations the source was in the horizontal branch and the upper part of the normal branch of the Z pattern in the X-ray colour-colour diagram, while in the third observation it was in the normal and flaring branches. We found that the hori…
The canonical X-ray/gamma-ray spectrum of Seyfert 1s and low-state Galactic black hole candidates.
Zdziarski, A. A.; Magdziarz, P.; Gierlinski, M. +1 more
We review broad-band X-ray/γ-ray spectra of radio-quiet Seyfert 1s as well as of Galactic black hole candidates in the low state. The spectra share their basic components: an underlying power law, a Compton-reflection component with an Fe Kα line, low-energy absorption by cold matter, and a high-energy cutoff above ~200keV. The X-ray energy spectr…
Observations of the central star and nebula of Abell 65.
Walsh, J. R.; Walton, N. A.
Imaging and spectrophotometry of the low surface brightness planetary nebula Abell 65 and its eclipsing binary central star are presented. The spectrum of the central star is remarkable in showing H and He lines in emission, similar to the spectra of cataclysmic variables. This is the second PN central star, after HFG 1, to show such stellar line …
A Long EUVE Observation of the Seyfert Galaxy RX J0437.4-4711
Halpern, Jules P.; Marshall, Herman L.
We monitored the soft X-ray-selected Seyfert galaxy RX J0437.4 - 4711 with the EUVE satellite continuously for 20 days in 1994 October- November. The Seyfert was detected in the 70-110 A range, both in the short-wavelength spectrometer and in the Deep Survey imager. Its light curve shows large-amplitude variability by a factor of 4 over the 20 day…
The abundance of boron in evolved A- and B-type stars.
Lambert, D. L.; Venn, K. A.; Lemke, M.
Boron abundances in A- and B-type stars may be a successful way to track evolutionary effects in these hot stars. The light elements - Li, Be, and B - are tracers of exposure to temperatures more moderate than those in which the H-burning CN-cycle operates. Thus, any exposure of surface stellar layers to deeper layers will affect these light eleme…
SO 2Distributions on Io
McGrath, Melissa A.; Belton, Michael J. S.; Sartoretti, Paola
We present an analysis of disk-resolved images of Io at 232.5, 260, and 285 nm taken with the FOC (Faint Object Camera) of the Hubble Space Telescope. The images at 232.5 and 260 nm were acquired in 1993 in an effort to separate the surface and SO2atmosphere contributions to the observed UV albedo. We combine these images to make UV col…
The central star of LoTr5 revisited.
Jasniewicz, G.; Thevenin, F.; Monier, R. +1 more
We report on new photometric and spectroscopic observations carried out in 1994 of the late-type star HD112313 in the binary nucleus of the planetary nebula LoTr5. From comparison with model spectra we derive a gravity logg=2.7+/-0.5 and an effective temperature T_eff_=5250+/-200K, in full agreement with a spectral type G5III. Iron is found to be …