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Rotational modulation and flares on RS CVn and BY Dra-type stars. V. EXOSAT and IUE observations of a flare on EQ Pegasi.
Doyle, J. G.; Rodono, M.; Butler, C. J. +1 more
Time-trailed UV spectra and a soft X-ray lightcurve were obtained during a flare on the binary dMe star EQ Peg AB. On the basis of solar flare Mg II surface fluxes and an about 70-percent enhancement in the disk-integrated flux during the flare on EQ Peg, it is estimated that the chromospheric flare covered about 1.5 percent of the stellar surface…
Soft X-ray observations of the radio pulsar PSR 1055-52.
Brinkmann, W.; Oegelman, H.
The radio pulsar PSR 1055-52 was observed with the EXOSAT X-ray satellite for a total of 105 s. The data can be fitted best with blackbody spectra having temperatures of 5×105 ≤ T ≤ 8×105K. The obtained temperatures are consistent with recent models for the initial cooling of neutron stars.
The pick-up of cometary protons by the solar wind
Altwegg, K.; Balsiger, H.; Goldstein, B. E. +3 more
The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of ≡8 million km upstream of the bow shock of comet P/Halley. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniform…
Comprehensive study of the QSO-galaxy pair 1327-206 and the extent oflow ionization galactic haloes.
Kunth, D.; Bergeron, J.; D'Odorico, S.
New observations of the absorption systems in the spectrum of the QSO-galaxy pair 1327-206 are presented. At a resolving power of about 10000, the Na I doublet from the z = 0.0179 absorber is resolved in at least two components separated by 236 km s-1. The ESO 1327-2041 spiral galaxy (z = 0.0180) is at a projected distance of 20(50/H
Low-frequency magnetic field fluctuations in comet P/Halley's magnetosheath - Giotto observations
Neubauer, F. M.; Glassmeier, K. H.; Mariani, F. +1 more
The interaction region between comets and the solar wind is characterized by large amplitude, low frequency magnetic field fluctuations, both within the upstream region as well as in the magnetosheath. Magnetosheath observations of the magnetic field experiment onboard Giotto indicate values of δB/B ≅ O(1). Power spectral peaks appear at frequenci…
In-situ observations of a bi-modal ion distribution in the outer coma of comet P/Halley
Thomsen, M. F.; Wilken, B.; Feldman, W. C. +2 more
Observations obtained by the Johnstone Plasma Analyzer on the Giotto fly-by of comet Halley showed a fairly sudden decrease in the count rate of energetic (≡30 keV) water-group ions inside about 5×105km from the nucleus. This decrease was accompanied by the appearance of a new water-group ion population at slightly lower energies (<1…
Waves in the magnetic field and solar wind flow outside the bow shock at comet P/Halley
Johnstone, A.; Glassmeier, K.; Acuna, M. +2 more
The existence of hydromagnetic waves in the mass-loaded solar wind upstream from the bow shock of a comet is well-established both for comet Giacobini-Zinner and for comet Halley. Whereas previous reports have been concerned either with the magnetic field observations or with plasma observations, here the authors combine observations of the magnet…
Solar Wind Flow Through the Comet p/ Halley Bow Shock
Coates, A. J.; Winningham, J. D.; Thomsen, M. F. +7 more
The bow shock of a comet is formed by the interaction of three different particle populations; solar wind ions, cometary ions and electrons. We follow the behaviour of the solar wind protons through the Giotto inbound shock crossing at comet P/Halley. A foreshock boundary is seen at ∼1.4 106 km where the level of solar wind fluctuations…
Chromospheric MG II H and K emissions free of interstellar contamination : velocity structure in late-type dwarfs and giants.
Molaro, P.; Beckman, J. E.; Foing, B. H. +3 more
The authors have used high resolution IUE spectra from their own studies and from the archive to examine the Mg II h and k chromospheric emission cores of a sample of late-type dwarfs and giants. Sharp photospheric absorptions were used to provide a velocity rest-frame with respect to each stellar photosphere with the IUE-limited precision of ±4 k…
A comparison of coronal X-ray emission observed with the Einstein andEXOSAT observatories.
Schmitt, J. H. M. M.; Monsignori-Fossi, B. C.; Pallavicini, R. +1 more
The present Einstein and Exosat observatories' star coronal X-ray emission data are subjected to a spectral analysis which employs the Raymond and Smith (1977) and Landini and Fossi (1984) computer codes to calculate X-ray emission from optically thin plasmas that are in collisional equilibrium. It is found that the derived coronal parameters depe…