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HST imaging of the planetary nebula K 648 in M 15.
Bianchi, L.; Paresce, F.; de Marchi, G. +2 more
Two images of the Planetary Nebula K 648 in M 15 were taken in the PC mode of the WFPC1 camera on HST in the narrow [OIII] and Halpha_ filters, and an image in [OIII] light with the FOC. This object, never resolved before in ground-based data, is resolved in the HST images. It shows a bipolar structure: a spherical shell containing a br…
A Method for Determining the Individual Accuracy of Astrometric Catalogues
Wielen, R.
We present a method for determining empirically the actual accuracy (external errors) of proper motions and positions given in astrometric catalogues. The method is based on a comparison of a sufficient number of independent proper motions and positions. The method can be applied, for example, to a comparison of the basic FK5 and the future Hippar…
Coronal electron stream and Langmuir wave detection inside a propagation channel at 4.3 AU
Pick, M.; Forsyth, R. J.; Phillips, J. L. +5 more
Observations of an energetic interplanetary electron event associated with the production of Langmuir waves, both of which are identified at 4.3 AU by instruments on the Ulysses spacecraft, are presented in this paper. This electron event propagates inside a well defined magnetic structure. The existence of this structure is firmly established by …
Far-Ultraviolet and Optical Spectroscopy of the Detached White Dwarf-M Dwarf Binary RE J1629+780
Sion, Edward M.; Barstow, Martin A.; Holberg, Jay B. +1 more
We present optical and far ultraviolet observations, including IUE high and low dispersion spectroscopy of the (DA2+dM4-5) close binary, RE J1629+780, a very bright ROSAT EUV source. The optical data reveal emission reversals in the cores of the Balmer lines, which vary in strength but reveal no evidence of wavelength shifts reflecting orbital mot…
Auroral Signature of Comet Shoemaker-Levy 9 in the Jovian Magnetosphere
Ip, W. H.; Dunlop, M.; Clarke, J. T. +5 more
The electrodynamic interaction of the dust and gas comae of comet Shoemaker-Levy 9 with the jovian magnetosphere was unique and different from the atmospheric effects. Early theoretical predictions of auroral-type processes on the comet magnetic field line and advanced modeling of the time-varying morphology of these lines allowed dedicated observ…
Generation of Mass Loss in K Giants: The Failure of Global Oscillation Modes and Possible Implications
Cuntz, M.; Sutmann, G.
It is a well-established observational result that many inactive K stars show global oscillation modes, which lead to low-amplitude photospheric velocity variations. It is the purpose of this paper to investigate whether these modes are relevant to the outer atmospheric dynamics, including the generation of mass loss. We find that this is not the …
The orbital period of the pre-cataclysmic binary RE 2013+400 and a study of the atmosphere of the DAO white dwarf primary
Rutten, R. G. M.; Barstow, M. A.; Koester, D. +8 more
Several pre-cataclysmic binaries, comprising a hot white dwarf with a red dwarf companion, have been discovered as a result of the optical identification of EUV sources from the ROSAT all-sky survey. The optical spectra have the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of …
Ultraviolet Extinction to 10.8 Inverse Microns
Aannestad, Per A.
UV extinction curves that represent observed variations i diffuse clouds (Zeta Oph, Xi Per, and Sigma Sco) have been derived by combining IUE and Voyager data and have been modeled by a multicomponent size distribution of silicate and carbonaceous giants. We have used theoretical model atmospheres as our reddening-free standards, and, in the case …
Multifrequency monitoring of RU Lupi. I. Observations.
Rossi, C.; Giovannelli, F.; Vittone, A. A. +7 more
In this paper we present the results of a long campaign of coordinated (sometimes simultaneous) multifrequency observations, from X-ray to radio wavelengths of the extreme T Tauri star RU Lupi. The large amount of data obtained can be useful to understanding the physics governing the intriguing behaviour of this pre-main-sequence star. In particul…
The anomalous component of cosmic rays: Oxygen latitudinal gradient
Klecker, B.; Sanderson, T. R.; Marsden, R. G. +3 more
We have studied the latitudinal evolution of the anomalous cosmic ray oxygen component at ULYSSES during its journey to the south pole of the sun. Observations from the COSPIN Low Energy Telescope at ULYSSES are compared with observations in the vicinity of the Earth, provided by the HILT sensor on the SAMPEX spacecraft. We present results in two …