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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…
Implications of the UV observations of SN 1987A.
Panagia, N.; Fransson, C.; Grewing, M. +2 more
The implications of the UV observations of SN 1987A are discussed. The authors conclude that the UV spectrum is not a distinguishing feature between Type I and II supernovae. There is therefore no contradiction with the optical observations. Instead it is proposed that the differences in the UV properties are to be sought in the varying degree of …
A search for X-ray emission from a nearby pulsar : PSR 1929+10.
Brinkmann, W.; Kiziloglu, U.; Oegelman, H. +2 more
The authors report observations of PSR 1929+10 with the EXOSAT observatory. In the 0.04 to 2.4 keV range a 2σ upper limit of 0.5×10-3cts s-1 was obtained. This translates to a luminosity upper limit of L ≤ 2×1029erg s-1 for a power-law source with photon number index α = 1 - 3, and L ≤ 1030erg…
Long-term variability of the far-UV high velocity components in gammaCas (1978-1986).
Doazan, V.; Thomas, R. N.; Rusconi, L. +2 more
A synthesis of the authors' long term observations of γ Cas in the visual and in the far UV, combined with IUE archived spectra, shows that: (1) The occurrence of the high velocity components observed in the Si IV, C IV, and N V resonance lines exhibits a long term variability pattern, which is associated with the cyclic V/R variations of the Balm…
Alfvenic Turbulence in the Solar Wind Flow during the Approach to Comet p/ Halley
Coates, A. J.; Winningham, J. D.; Thomsen, M. F. +8 more
The Johnstone Plasma Analyser on Giotto operated almost continuously for two days before the encounter with comet Halley. Throughout this period it made observations of the proton and alpha particle distributions in the solar wind with 8 seconds time resolution. As the comet was approached, fluctuations were observed in all the primary bulk parame…
Photometry and spectroscopy of the eclipsing P Cygni star R 81 in theLarge Magellanic Cloud.
Stahl, O.; Zickgraf, F. -J.; Wolf, B.
IUE high resolution data of the LMC P Cyg star R 81 confirm that the wind characteristics of R 81 and P Cyg are very similar. Photometric monitoring from 1982 to 1986 revealed several brightness minima with a period of 74.59 days. It is concluded that R 81 is an eclipsing binary with this period. From the photometry and the period, a preliminary m…
NGC 40 : IUE observations of the nucleus.
Grewing, M.; Bianchi, L.
UV spectra of the nucleus of NGC 40 allow a derivation of an E(B-V) foreground reddening of 0.50 and a distance to the object of 980 pc; accordingly, T(eff) of 90,000 K, log L/L(solar) of 4.4, R of 0.66 R(solar), and M of 1.1 M(solar) are obtained. It is suggested that the discrepancy between the temperature determined from the UV emission of the …